Faculty Profiles - OHNO, Noriyasu

Tungsten fuzz growth at low temperatures (<900 K) on a surface with nanocones Reviewed International journal

Shi Q., Kajita S., Ohno N.

Nuclear Materials and Energy Vol. 39 page： 101668 2024.5

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Nuclear Materials and Energy

The tungsten (W) fuzzy structure was widely observed in linear plasma devices under the fusion-relevant condition. This type of structure can be used in many application fields benefiting from its larger surface area and high optical absorbance. However, W fuzz can be barely formed when the sample temperature is lower than 900 K. This study decreased the threshold to ∼800 K using W co-deposition on a Si nanocones substrate. It suggests that the conventional threshold temperature is only necessary for He bubble rupture to create a rough surface that induces the uneven trapping of the adatom diffusion.

DOI： 10.1016/j.nme.2024.101668

Surface modification of ZrC dispersion-strengthened W under low energy He plasma irradiation Reviewed International coauthorship

Li L., Liu Z., Chen Z., Yin C., Mao S., Wu X., Ohno N., Ye M.

Nuclear Fusion Vol. 64 ( 5 ) page： 56008 2024.5

Language：English Publishing type：Research paper (scientific journal) Publisher：Nuclear Fusion

ZrC dispersion-strengthened W exhibits high strength/ductility, low ductile-to-brittle transition temperature, and excellent thermal shock resistance, making it a promising candidate plasma-facing material for future fusion devices. In this study, surface modification of 0.5 wt.% ZrC dispersion-strengthened W (WZrC) under low energy and high fluence He plasma irradiation at high temperature was presented. Under the energy of 90 eV and fluence ranging from 6 × 1024 He·m−2-2 × 1026 He·m−2 He irradiation at 920 °C, a typical fuzz nanostructure appeared on the W matrix of WZrC. The thickness of fuzz layer is proportional to the square root of He irradiation fluence. The fuzz showed comparable thickness and structural features to pure W, indicating limited effects of the particle’s addition on resistance to high fluence He irradiation at high temperatures. Under continuous He injection, the fuzz would grow extending onto the particle area, making the particle obscured. Besides, the erosion behavior of particles under He plasma irradiation has been investigated, which is thought to be dominated by a sputtering process. Under the He influence of 6 × 1024 He·m−2, only nanopores were observed in the surface region. With fluence increasing to 5 × 1025 He·m−2, the surface became relatively uneven with larger holes. W aggregated in spots and distributed on the surface of the particle, which might be the result of subthreshold sputtering and deposition. When fluence further increased to 2 × 1026 He·m−2, the particles were eroded completely and covered by the extended fuzz, forming cavities. In addition, distinctive layered nanotendrils were observed above the cavities, which were characterized to consist of inner W-riched skeletons and outer Zr-riched layers. It indicates that the layered nanotendrils should be the result of fuzz extension combined with particle sputtering/deposition.

DOI： 10.1088/1741-4326/ad2f4c

Nanopatterning of Si surfaces by normal incident He plasma irradiation Reviewed

Liu Z., Li L., Gao Z., Chen Z., Yin C., Mao S., Kajita S., Ohno N., Ye M.

Applied Physics Letters Vol. 124 ( 10 ) 2024.3

Publisher：Applied Physics Letters

This study reports on the formation of self-organized silicon (Si) nanostructures by 75 eV helium (He) plasma irradiation at normal incidence without the presence of impurities. In contrast to the featureless surface after normal incidence argon (Ar) ion beam irradiation without the co-deposition of impurities, the Si surface exhibits the development of faceted nanostructures under 75 eV He plasma irradiation. The faceted structures are interspersed with valleys that extend in two orthogonal directions, imparting a mountain-like morphology to the surface. Our investigation verifies that the He bubbles align themselves along the direction perpendicular to the surface underneath these valleys. Furthermore, the presence of He bubbles induces distortion in the surface layer and leads to the formation of an amorphous Si layer. The underlying mechanism driving this surface evolution could be attributed to the instability induced by the presence of He bubbles.

DOI： 10.1063/5.0186756

Cone array formation on Si surfaces by low-energy He plasma irradiation with magnetron sputtering pre-deposited Ta Reviewed International coauthorship

Liu Z., Li L., Gao Z., Chen Z., Yin C., Mao S., Kajita S., Ohno N., Ye M.

Journal of Applied Physics Vol. 135 ( 9 ) page： 93302 2024.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Applied Physics

Low-energy ion beam irradiation, combined with the introduction of impurities, presents a promising approach for nanopatterning silicon (Si) surfaces. In this research, we investigate the surface evolution of Si (100) surfaces irradiated by 75 eV helium (He) plasma, in the presence of tantalum (Ta), traditionally regarded as an impurity incapable of initiating pattern formation, as evidenced in prior studies. The Ta impurities are pre-deposited onto the Si surfaces using the magnetron sputtering method, which offers a more controlled and quantifiable approach compared with the conventional co-deposition route. After irradiation at 800 K, dense cone arrays are produced on the Si surface. The growth of the cones is explored for fluence spanning (1-10) × 1025 m−2. The cross-sectional scanning electron microscope images indicate that the cone lengths and base width are well characterized by t1/2 dependence. The kinetics of the cone growth follow Fick’s law, characterized by an effective diffusive mechanism with the coefficients of diffusion: D = 6.49 ± 0.83 × 10−16 m−2 s−1. Transmission electron microscope observations reveal that the cone has distinct inner and outer parts with different microstructures and a clear interface. The growth mechanism of these cones is elucidated as a composite process involving preferential sputtering, the destabilizing influence of He bubbles, and the migration of adatoms.

DOI： 10.1063/5.0187265

Plasma-Driven Sciences: Exploring Complex Interactions at Plasma Boundaries Reviewed International journal

Ishikawa K., Koga K., Ohno N.

Plasma Vol. 7 ( 1 ) page： 160 - 177 2024.3

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Plasma

Plasma-driven science is defined as the artificial control of physical plasma-driven phenomena based on complex interactions between nonequilibrium open systems. Recently, peculiar phenomena related to physical plasma have been discovered in plasma boundary regions, either naturally or artificially. Because laboratory plasma can be produced under nominal conditions around atmospheric pressure and room temperature, phenomena related to the interaction of plasma with liquid solutions and living organisms at the plasma boundaries are emerging. Currently, the relationships between these complex interactions should be solved using science-based data-driven approaches; these approaches require a reliable and comprehensive database of dynamic changes in the chemical networks of elementary reactions. Consequently, the elucidation of the mechanisms governing plasma-driven phenomena and the discovery of the latent actions behind these plasma-driven phenomena will be realized through plasma-driven science.

DOI： 10.3390/plasma7010011

Thermal Conductivity Measurement of Fuzzy W Using a Thermoreflectance Method Reviewed

Kajita S., Yagi T., Ohno N.

IEEE Transactions on Plasma Science Vol. Early Access page： 1 - 6 2024.1

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE Transactions on Plasma Science

Fuzzy nanostructured tungsten (W) is formed by helium (He) plasma irradiation. In fusion devices, the thermophysical properties are important to consider the response to pulsed heat load from the plasma. In this work, the thermal conductivity of the W fuzz is measured using a pulsed light heating thermoreflectance method. A detailed model was developed to explain the entire temporal evolution of the thermoreflectance signal. It was found that the thermal conductivity of the nanostructured layer was deduced to be in the range of 0.18%–0.21% of the pure (ideal) W and lower than the previously reported highly porous metallic materials. In addition to the porosity, the specific nonuniform nanofiber structure is likely to contribute to the low effective thermal conductivity.

DOI： 10.1109/TPS.2023.3348465

Thermal response of nano-tendril bundles to steady heat load Reviewed International coauthorship

Xue Qi, Tanaka Hirohiko, Zhang Rongshi, Kajita Shin, Hori Kenta, Shi Quan, Kuwabara Tatsuya, Ohno Noriyasu

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 62 ( SN ) 2023.11

Transition from MAR to EIR of deuterium plasma detachment in NAGDIS-II Reviewed International coauthorship

Shi J., Kaizawa H., Tanaka H., Kajita S., Ohno N., Ding H.

Physica Scripta Vol. 98 ( 11 ) page： 115605 2023.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Physica Scripta

Volumetric plasma recombination in a detached deuterium (D) plasma was experimentally studied in the linear plasma device NAGDIS-II. The radial distributions of the electron temperature (Te) and the electron density (ne) were measured by upstream and downstream laser Thomson scattering (LTS) systems and D-atom excited states of the Balmer series (n = 3-7) were measured by optical emission spectroscopy (OES). The results indicated that the electron static pressure, particle flux and heat flux present a two-step reduction with an increasing neutral pressure, suggesting that molecule activated recombination (MAR) and electron-ion recombination (EIR) were activated, respectively. The difference in the distributions of the atomic state population densities was observed to be a feature of the transition from the MAR-dominant phase to the EIR-dominant phase. The transition between the two phases had a distinct boundary at Te ∼0.7 eV, which was considered a transition point between the phases. The ratios of the atomic state population densities showed different features in the two phases, and are expected to be useful in characterizing the phase and degree of plasma detachment.

DOI： 10.1088/1402-4896/acfeb4

Application of machine learning for optical emission spectroscopy data in NAGDIS-II Reviewed

Kajita S., Sakakibara T., Kaizawa H., Natsume H., Tanaka H., Fujii K., Ohno N.

Fusion Engineering and Design Vol. 196 page： 114012 2023.9

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Fusion Engineering and Design

In this study, we applied machine learning to optical emission spectroscopy (OES) data and device parameters from the linear plasma device NAGDIS-II to explore the potential application of machine learning for predicting electron density, ne, and temperature, Te. The covered ranges of ne and Te, which were measured by an electrostatic probe, are 3.6 × 1017–2.4×1019 m−3 and 0.3–7.1eV, respectively. A three hidden layer neural network (NN) is introduced to model the relationship between ne/Te and the combination of line intensities, radial position, and device parameters. It is shown that the errors in ne and Te become 18.0 and 18.8%, respectively, which were almost the same level for the electrostatic probe, using all available data. Lasso regression and greedy algorithm are used to select the necessary line emissions. It is shown that four or five line intensities are sufficient to obtain almost the same quality as the one with all the other lines.

DOI： 10.1016/j.fusengdes.2023.114012

Erratum: Morphologies of co-depositing W layer formed during He plasma irradiation (International Atomic Energy Agency (2018) 58 (106002) DOI: 10.1088/1741-4326/aad24e) Reviewed

Fabrication of tungsten-based optical diffuser using fiberform nanostructure via efficient plasma route Reviewed International coauthorship

Feng Shuangyuan, Natsume Hiroki, Kajita Shin, Li Enhao, Yasuhara Ryo, Tokitani Masayuki, Tanaka Hirohiko, Ohno Noriyasu

OPTICS EXPRESS Vol. 31 ( 16 ) page： 25438 - 25445 2023.7

Field emission properties of nano-tendril bundles formed via helium plasma exposure with various additional impurity gases Reviewed International coauthorship

Zhang Rongshi, Kajita Shin, Hwangbo Dogyun, Tanaka Hirohiko, Feng Shuangyuan, Ohno Noriyasu

MATERIALS RESEARCH EXPRESS Vol. 10 ( 5 ) page： 054002 2023.5

Growth origin of large-scale fiberform nanostructures in He-W co-deposition environment Reviewed

Hori K, Kajita S, Zhang R, Tanaka H, Ohno N

Scientific reports Vol. 13 ( 1 ) page： 5450 2023.4

Rapid growth of nanostructure on tungsten thin film by exposure to helium plasma Reviewed

Feng Shuangyuan, Kajita Shin, Tokitani Masayuki, Nagata Daisuke, Ohno Noriyasu

PLASMA SCIENCE & TECHNOLOGY Vol. 25 ( 4 ) page： 042001 2023.4

Kajita S., Kawaguchi S., Yoshida N., Ohno N., Tanaka H.

Nuclear Fusion Vol. 63 ( 4 ) 2023.4

Correlation of the Orthogonal Basis of the Core Plasma Distribution to the Divertor Footprint Distribution in LHD

TANAKA Hirohiko, MASUZAKI Suguru, KAWAMURA Gakushi, HAYASHI Yuki, KOBAYASHI Masahiro, SUZUKI Yasuhiro, MUKAI Kiyofumi, KAJITA Shin, OHNO Noriyasu

Plasma and Fusion Research Vol. 18 ( 0 ) page： 2402021 - 2402021 2023.3

Language：English Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Plasma Science and Nuclear Fusion Research

We have applied the multivariable analysis technique called the proper orthogonal decomposition (POD) to both the divertor particle flux distribution and the electron pressure distribution in the core region of LHD. The cross-correlation analysis indicates that 3rd, 4th, and 5th POD modes of the electron pressure distribution are highly correlated with the divertor footprint index which is a measure of where the peak position of the particle flux distribution is located on the inner divertor plate. Both the 3rd and 4th modes seem to correspond to the shift of the electron pressure peak position from the magnetic-axis radius. In contrast, 5th mode has a strong influence on the peripheral gradient of the electron pressure distribution. Their relationships with the divertor footprint could be explained by the finite βand the Pfirsch-Schlüter current effects.

DOI： 10.1585/pfr.18.2402021

Study of the intermittent plasma structure around the divertor simulation experimental module in GAMMA 10/PDX Reviewed

Tanaka H., Ezumi N., Sugiyama T., Gamo H., Shigematsu N., Yoshikawa M., Kohagura J., Hirata M., Togo S., Ohno N., Sakamoto M.

PHYSICS OF PLASMAS Vol. 30 ( 3 ) page： 32501 2023.3

Structural Correlation of Random Lasing Performance in Plasma-Induced Surface-Modified Gallium Nitride Reviewed

Shi Q., Fujiwara H., Kajita S., Yasuhara R., Tanaka H., Ohno N., Uehara H.

ACS Applied Optical Materials Vol. 1 ( 1 ) page： 412 - 420 2023.1

Publisher：ACS Applied Optical Materials

The surface of GaN has been modified by a simple method that irradiates the substrate with Ar plasma and impurity codeposition, which is termed CoDE (Co-Deposition Etching). Unique structures were formed by the assistance of a small amount of Mo deposition without degradation of the crystal structure. The size of protrusions on the structure is influenced by the amount of deposited Mo particles. The mechanism for the structure formation is discussed based on transmission electron microscopy (TEM) observations and energy dispersive X-ray spectroscopy (EDS) measurements. Based on the GaN surface roughness, we have demonstrated random laser action in the UV region under photoexcitation. The lowest threshold (0.06 J/cm2) for random lasing was observed where the size of the structure is larger than 0.05 μm2, which was formed under conditions with the least amount of deposition. The correlation between the submicro/nanosize structures generated by plasma irradiation and lasing was evaluated in detail. The critical parameter to optimize the random lasing was determined to be the size of structures that can be modified by the Mo deposition rate. The results confirmed that the emission properties can be controlled by the processing conditions. This random laser fabrication technique is expected to be widely applicable to various direct-bandgap compound semiconductors.

DOI： 10.1021/acsaom.2c00085

Motion analysis of arc spots on tungsten fuzz by means of self-avoiding random walk model Reviewed

Hwangbo Dogyun, Nishijima Daisuke, Kajita Shin, Ohno Noriyasu

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 62 ( SA ) page： SA1007 2023.1

Field emission current from protrusion structures formed by helium plasma with various impurity gases Reviewed

Zhang R., Kajita S., Tanaka H., Hwangbo D., Ohno N.

Proceedings - International Symposium on Discharges and Electrical Insulation in Vacuum, ISDEIV Vol. 2023-June page： 529 - 532 2023

Publisher：Proceedings - International Symposium on Discharges and Electrical Insulation in Vacuum, ISDEIV

Rod-like protrusion structures were formed on tungsten by helium plasma exposure with various impurity gases seeded as nitrogen (N2) and argon (Ar). Surface morphology observations and field emission current measurements were done for two samples. Cross-section observation shows that the inside of the protrusions was solid but not porous like conventional fuzz. Therefore, a new formation mechanism which is different from fuzz can be considered. The field emission current from N2-seeded case was slightly higher than that from fuzz, but much lower than that from NTBs, while the field emission current from Ar-seeded case was similar to that from NTBs. The difference in field emission current could be due to the different morphology of the tips between two samples.

DOI： 10.23919/ISDEIV55268.2023.10200357

Thermal conductivity measurement of fuzzy W using a thermoreflectance method Reviewed

Kajita S., Yagi T., Ohno N.

Proceedings - International Symposium on Discharges and Electrical Insulation in Vacuum, ISDEIV Vol. 2023-June page： 526 - 528 2023

Publisher：Proceedings - International Symposium on Discharges and Electrical Insulation in Vacuum, ISDEIV

Thermophysical properties of the fuzzy nanostructured tungsten (W) layer formed by helium plasma irradiation (a) are measured using a pulsed light heating thermoreflectance method. A three layered model has been developed to explain the temporal evolution of the themoreflectance signal. The thermal conductivity of the nanostructured layer was deduced to be in the range of 0.14-0.26% of the pure (ideal) W.

DOI： 10.23919/ISDEIV55268.2023.10200254

Plasma induced surface nanostructure on semiconductors for the application of random laser Reviewed

Use of machine learning for a helium line intensity ratio method in Magnum-PSI Reviewed International coauthorship

Kajita Shin, Iwai Sho, Tanaka Hirohiko, Nishijima Daisuke, Fujii Keisuke, van der Meiden Hennie, Ohno Noriyasu

NUCLEAR MATERIALS AND ENERGY Vol. 33 page： 101281 2022.10

Shi Q., Fujiwara H., Osaka R., Kajita S., Yasuhara R., Ohno N., Uehara H.

2022 Conference on Lasers and Electro-Optics Pacific Rim, CLEO-PR 2022 - Proceedings 2022

POWER TRANSMISSION FACTOR FOR TUNGSTEN TARGET W/WO FIBER-FORM NANOSTRUCTURE IN H PLASMAS WITH HOT ELECTRON COMPONENT USING COMPACT PLASMA DEVICE AIT-PID Reviewed International journal

Takamura, S; Miyamoto, T; Ohno, N

FUSION SCIENCE AND TECHNOLOGY Vol. 63 ( 1T ) page： 225 - 228 2013.5

Simulation of dynamics of carbon dust particles in the JT-60U tokamak Reviewed International coauthorship International journal

Tanaka, Y; Smirnov, RD; Pigarov, AY; Takenaga, H; Asakura, N; Uesugi, Y; Ohno, N

JOURNAL OF NUCLEAR MATERIALS Vol. 415 ( 1 ) page： S1106 - S1110 2011.8

Dusty sheaths in plasmas with two-temperature electrons Reviewed International journal

Asano, K; Chutov, YI; Kravchenko, OY; Ohno, N; Pshenychnyj, AF; Smirnov, RD; Takamura, S

DUSTY PLASMAS IN THE NEW MILLENNIUM Vol. 649 page： 277 - 280 2002

Generation of high heat flux plasma in divertor plasma simulator by ion cyclotron wave heating Reviewed International journal

Watanabe, S; Ohsawa, S; Takagi, M; Ohno, N; Uesugi, Y; Takamura, S

ICPP 96 CONTRIBUTED PAPERS - PROCEEDINGS OF THE 1996 INTERNATIONAL CONFERENCE ON PLASMA PHYSICS, VOLS 1 AND 2 page： 1050 - 1053 1997

Generation of high heat flux plasmas by rf heating in divertor plasma simulator NAGDIS-II Reviewed International journal

Watanabe, S; Ohsawa, S; Takagi, M; Ohno, N; Uesugi, Y; Takamura, S

RADIO FREQUENCY POWER IN PLASMAS ( 403 ) page： 483 - 486 1997

STUDIES ON SHEATH FORMATION IN DIVERTOR PLASMAS BY COMPUTER-SIMULATION USING PARTICLES Reviewed International journal

OHNO, N; MASUZAKI, S; KONNO, H; TAKAMURA, S

CONTRIBUTIONS TO PLASMA PHYSICS Vol. 32 ( 3-4 ) page： 249 - 254 1992

Experiments on Subharmonic Waves in an Ion Beam-Plasma System Reviewed

Ono Noriyasu, Kasuya Toshiro, Tanaka Masayoshi, Komori Akio, Kawai Yoshinobu

Vol. 9 ( 1 ) page： 23 - 27 1987.7

Language：Japanese Publisher：Interdisciplinary Graduate School of Engineering Sciences, Kyushu University

Subharmonic waves are experimentally studied in detail by applying pump waves to an ion beam-plasma system. It is found that the subharmonic waves are excited in the characteristic region of the pump-wave frequency, accompanied with low-frequency fluctuations. These low-frequency fluctuations are considered to play an important role on excitation of the subharmonics.

DOI： 10.15017/17680

TALIF measurements of atomic deuterium in toroidal divertor simulator NAGDIS-T Reviewed International journal

Kajita S., Hiraiwa K., Tanaka H., Iwai R., Aramaki M., Yasuhara R., Ohno N.

Nuclear Materials and Energy Vol. 42 2025.3

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Nuclear Materials and Energy

The behavior of neutral deuterium (D) atoms is important for understanding the physics in the divertor region of nuclear fusion reactors. It is necessary to introduce an active measurement when considering the application to detached plasmas, where recombination processes dominate the processes determining the population distribution. In this work, we have developed a two-photon absorption laser-induced fluorescence (TALIF) system in the toroidal divertor simulator NAGDIS-T to measure D atomic density. The absolute D atomic density was obtained by calibrating the signal with the krypton TALIF signal. The gas pressure and power dependence of the D atomic density is shown. The D atomic density was in the range of 1.6 × 1018–1.4 × 1019 m−3, and the temperature was estimated to be <0.4 eV. The behavior of the D atoms is discussed in terms of the production process.

DOI： 10.1016/j.nme.2025.101898

Formation of micro-pillars on W by He plasma irradiation with N<inf>2</inf>/Ar impurities Reviewed International journal

Zhang R., Kajita S., Hwangbo D., Tanaka H., Yamamoto Y., Ohno N.

Materialia Vol. 39 2025.3

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Materialia

Tungsten samples were exposed to helium plasma with additional nitrogen and argon impurity gases. As a result, microscale pillar-like structures formed on the tungsten surface under similar conditions where nanotendril bundles can be formed. This study summarizes the condition under which those pillar-like structures form. The surface morphology and height profile were observed, and the field emission properties of the W sample with the pillar-like structure were analyzed. The possible formation mechanism of these structures was discussed.

DOI： 10.1016/j.mtla.2025.102341

DISCOVER: New integrated code to simulate helium detached plasma in a linear device Reviewed International journal

Natsume H., Masuda S., Tanaka H., Migita R., Mano R., Sugiura K., Sawada K., Hoshino K., Hayashi Y., Ohno N.

Physics of Plasmas Vol. 32 ( 2 ) 2025.2

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Physics of Plasmas

A detached plasma integrated simulation code with various elastic/inelastic reactions (DISCOVER) was developed for better understanding of detached helium plasma experiments. DISCOVER, which includes a neutral transport code, fluid code, and collisional radiative code, considers elastic and inelastic collisions between recycling neutrals and bulk particles, as well as the transport of metastable atoms [He( 21S) and He( 23S)]. The code was used for simulating helium plasma in the linear plasma device NAGDIS-II. The transition from attached to detached plasma was demonstrated in the simulation by increasing the upstream electron density through an increase in the gas supply from the plasma source while maintaining a fixed downstream gas injection rate. In addition, similar transition was also observed by introducing neutral particles from downstream, while maintaining a fixed upstream electron density. In the detached plasma, the density of He( 23S) near the end target was approximately seven times higher than that in the attached plasma. Furthermore, it was evident that the transport of He( 23S) enhanced the electron energy rate coefficient and influenced the spatial distribution of the detached plasma.

DOI： 10.1063/5.0243036

Dynamic response of recombining detached plasma to electron beam injection Reviewed International journal

Tanaka H., Kajita S., Kaizawa H., Ohno N.

Physics of Plasmas Vol. 32 ( 2 ) 2025.2

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Physics of Plasmas

Dynamic response of recombining detached helium plasma to high-energy electrons was investigated in the linear plasma device NAGDIS-II by introducing an electron beam source. A square wave bias was applied to the tungsten electrode to generate a pulsed electron beam with controlled beam energy. At high beam energy condition, a large increase in the target ion flux and different-shape time evolutions between emissions from low- and high-excited states were observed. From the analysis using a collisional radiative code applicable to two electron temperature components, qualitative changes were explained by contributions due to the excitation process from the ground state by the electron beam and the volume recombination process due to the parameter change of bulk plasma.

DOI： 10.1063/5.0242483

Thermal evolution of helium bubbles in tungsten by GISAXS and TDS Reviewed International journal Open Access

Teo S.H.B., Thompson M.A.T., Kirby N., Hughes D.R., Hammoud N., Khan A., Tanaka H., Ohno N., Mummery P., Harmer S.L., Corr C.S.

Journal of Nuclear Materials Vol. 604 2025.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Nuclear Materials

Grazing-incidence small-angle x-ray scattering (GISAXS) and thermal desorption spectroscopy (TDS) were used to study the thermal evolution of helium (He) bubbles in tungsten (W). W samples were exposed to a low ion energy (∼20 eV, sheath accelerated) He plasma at two sample temperatures: 573 K (low-temperature) and 1050 K (high-temperature). They were then annealed to temperatures of 773 K, 873 K and 998 K. GISAXS analysis showed an increase in the median bubble radius of the high-temperature samples from 6.42 Å to 12.87 Å as a result of annealing to 998 K. No changes in the bubble radii distributions were observed for the low-temperature samples and the median radius remained at ∼4 Å even after annealing. TDS showed that the desorption behaviour of He in W has a dependence on the sample temperature during plasma irradiation. The higher-temperature sample experienced a maximum desorption rate that is an order of magnitude larger than the low-temperature sample. The desorption profile of the high-temperature sample spanned a wider temperature range, 500 K - 1500 K, than the low-temperature sample, 500 K - 750 K. The formation and thermal evolution of He bubbles in W have a clear dependence on sample temperature during plasma exposure. The differences in annealing behaviour observed in this work agree with prior in-situ TEM annealing experiments and help explain macroscopic plasma-material interaction effects such as recrystallisation suppression.

DOI： 10.1016/j.jnucmat.2024.155524

Open Access

Evaluation of local erosion and deposition on the W-monoblock of JA-DEMO divertor Reviewed International journal

Oya M., Hoshino K., Asakura N., Sakamoto Y., Ohno N., Hanada K.

Nuclear Materials and Energy Vol. 41 2024.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Nuclear Materials and Energy

We developed and performed a 3D Monte-Carlo simulation on local erosion and deposition in outer divertor target of JA-DEMO. The local erosion and deposition were evaluated considering the divertor plasma parameters and the roof shape of W-monoblocks. First, for local erosion simulation, the trajectories of D ions and impurity (He and Ar) ions were traced before irradiating the monoblock surface. The physical sputtering was calculated by these ions irradiation, considering their charge states, incident-energies and -angles. The highest sputtering flux was produced by multiply-charged Ar ions (Ar3+–Ar5+). The sputtering flux strongly depended on the poloidal positions along the divertor target. Although almost no erosion (sputtering) was obtained in low-temperature zone (∼1 eV), the erosion occurred in mid- (∼10 eV) and high-temperature (>10 eV) zone. Second, for local deposition simulation, the trajectories of W atoms emitted from the monoblock surface were traced. After transport (including ionization and recombination) in the plasma, W atoms and ions were deposited on the monoblock surface. The deposition occurred even on the area where plasmas did not irradiate (shadow). This was due to perpendicular diffusion to magnetic field lines, gyro-orbit effects for W ions and straight-line motion for neutral W atoms. The poloidal distribution of the deposition fluxes was similar to that of the sputtering fluxes. In low-temperature zone, no deposition flux occurred due to very low sputtering flux. The deposition flux in mid-temperature zone increased significantly and that in high-temperature zone remained high.

DOI： 10.1016/j.nme.2024.101793

Recent progress of JT-60SA project toward plasma operation Reviewed International coauthorship International journal

Shirai H., Takahashi K., Di Pietro E., Abate D., Abdel Maksoud W., Abe H., Aiba N., Abe T., Akimitsu M., Ayllon-Guerola J., Arai T., Artaud J.F., Asakura N., Ashikawa N., Balbinot L., Barabaschi P., Baulaigue O., Belonohy E., Belpane A., Bin W., Bombarda F., Bolzonella T., Bonne F., Bonotto M., Botija J., Buermans J., Cabrera-Pérez S., Cardella A., Carralero D., Carraro L., Cavalier J., Cavinato M., Chernyshova M., Chiba S., Clement-Lorenzo S., Cocilovo V., Coda S., Coelho R., Coffey I., Collin B., Corato V., Cucchiaro A., Czarski T., Dairaku M., Davis S., Day C., Dela Luna E., De Tommasi G., Decool P., Di Pace L., Dibon M., Disset G., D’Lsa F., Ejiri A., Endo Y., Ezumi N., Falchetto G., Fassina A., Fejoz P., Ferro A., Fietz W., Figini L., Fornal T., Frello G., Fujita T., Fukuda T., Fukui K., Fukumoto M., Funaba H., Furukawa M., Futatani S., Gabellieri L., Gaio E., Galazka K., Garcia J., Garcia-Dominguez J., Garcia-Lopez J., Garcia-Munoz M., Garzotti L., Gasparini F., Gharafi S., Giacomelli L., Ginoulhiac G., Giruzzi G., Giudicotti L., Gonzalez-Martin J., Guillén-González R., Hajnal N., Hall S., Hamada K., Hanada K., Hanada M., Hasegawa K., Hatakeyama S., Hauer V., Hayashi N., Hayashi T., Heller R., Hidalgo-Salaverri J., Higashijima S.

Nuclear Fusion Vol. 64 ( 11 ) 2024.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Nuclear Fusion

Superconducting (SC) tokamak JT-60SA plays an essential role in fusion research and development by supporting and complementing the ITER project, providing directions to the DEMO design activity and fostering next generation scientists and engineers. Since the short circuit incident at the terminal joints of equilibrium field coil #1 during the integrated commissioning (IC) in March 2021, both EU and JA implementing agencies (IAs) have examined how to ensure safe operation of JT-60SA by mitigating the risk of possible discharge occurrence inside the cryostat. Based on the experience of the global Paschen tests, the IAs have established a strategy of risk mitigation measures, which is a combination of (i) reinforcement of insulation, (ii) avoiding unnecessary voltage application to the coil systems and (iii) immediate de-energization of the coils when deteriorated vacuum conditions are detected. Thanks to the considerable efforts of the Integrated Project Team members, the IC restarted in May 2023. After confirmation of the SC state of the coil systems (TF, EF and CS), the coil energization test and the plasma operation phase 1 (OP-1) started. The first plasma was successfully achieved on 23 October 2023 with a limited value of voltage and current applied to the coils. The plasma configuration control was also confirmed with low plasma current and low auxiliary heating power conditions. Based on the IO-F4E-QST collaboration, activities of JT-60SA have been shared with the IO and provided an important lesson for ITER assembly and commissioning, and will provide an outstanding contribution to fusion research at large. After OP-1, maintenance & enhancement phase 1 (M/E-1) starts from January 2024, in which in-vessel components are installed, and heating and diagnostic systems are extensively upgraded to allow a high power heating experiment planned in OP-2. In order to make the best use of JT-60SA, a newly organized JT-60SA experiment team will refine the research plan for the future high heating power operation phase.

DOI： 10.1088/1741-4326/ad34e4

Machine learning aided line intensity ratio method for helium-hydrogen mixed recombining plasmas Reviewed International coauthorship International journal

Kajita S., Nishijima D., Fujii K., Tanaka H., Vernimmen J., van der Meiden H., Classen I., Ohno N.

Plasma Physics and Controlled Fusion Vol. 66 ( 10 ) page： 105005 2024.8

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Plasma Physics and Controlled Fusion

The helium line intensity ratio (LIR) with the help of a collisional radiative (CR) model has long been used to measure the electron density, n e , and temperature, T e , and its potential and limitations for fusion applications have been discussed. However, it has been reported that the CR model approach leads to deviations in helium-hydrogen mixed plasmas and/or recombining plasmas. In this study, a machine learning (ML) aided LIR method is used to measure n e and T e from spectroscopic data of helium-hydrogen mixed recombining plasmas in the divertor simulator Magnum-PSI. To analyze mixed plasmas, which have more complex spectral shapes, the spectroscopy data were used directly for training instead of separating the intensities of each line. It is shown that the ML approach can provide a robust and simpler analysis method to deduce n e and T e from the visible emissions in helium-hydrogen mixed plasmas.

DOI： 10.1088/1361-6587/ad6a81

Germanium nanostructures by helium plasma irradiation Reviewed International journal

Kajita S., Shi Q., Tabata K., Kuwabara T., Tanaka H., Ohno N.

Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers Vol. 63 ( 7 ) page： 07SP07 2024.7

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers

The effects of helium plasma irradiation, which has been widely studied on metals, on germanium have been experimentally investigated. The irradiation temperature ranges from 430 to 720 K, and the incident ion energy ranges from 30 to 100 eV. From the scanning electron microscope (SEM) observation, it was found that various morphological changes including pits, nanocones, nanopillars, and roughened surfaces occur. The spatial scale of the morphological change was analyzed by applying fast Fourier transform to SEM micrographs. Thermal desorption spectroscopy analysis suggests that He atoms implanted on Ge play major roles in forming roughened surfaces at a surface temperature higher than 500 K.

DOI： 10.35848/1347-4065/ad5afe

Hydrogen isotope effects on recombination dominant plasmas in NAGDIS-II Reviewed International coauthorship International journal

Shi J., Kaizawa H., Uematsu Y., Tanaka H., Kajita S., Ohno N., Sawada K., Ding H.

Plasma Physics and Controlled Fusion Vol. 66 ( 8 ) page： 085006(11 pp) 2024.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Plasma Physics and Controlled Fusion

The detachment processes of the hydrogen (H) and deuterium (D) plasmas are comparatively investigated in the linear plasma device NAGDIS-II. The laser Thomson scattering measurements demonstrate that the recombination rate of the H plasma is greater than that of the D plasma as the neutral pressure increases in the molecular activated recombination (MAR) dominant detachment phase. As the recombination process by MAR is strongly dependent on the vibrational and rotationally excited states of the molecule, the rovibrational quantum state populations of the H and D molecules are measured using the Fulcher-α band spectroscopy. The results indicate that the vibrational temperature in the electronic ground state is considerably higher than the rotational temperature during detachment. The reaction rate coefficients for MARs due to charge exchange chains (CX-MAR) and dissociative attachment chains (DA-MAR) are calculated by the collision-radiation model under the measured temperature conditions. It can be observed that the CX-MAR is larger than the DA-MAR for both H and D, and that the CX-MAR of H is larger than the CX-MAR of D at electron temperatures T e above 1 eV. In consideration of the experimentally observed vibrational and rotational excitation temperatures, the reaction rate coefficients of CX-MAR and DA-MAR are increasing in the low T e region. These calculations are in accordance with the experimental results, which indicate that recombination processes due to MAR are more predominant in the H plasma compared to the D plasma. Furthermore, a transition from MAR to electron-ion recombination processes is observed in the D plasma at T e below 0.5 eV.

DOI： 10.1088/1361-6587/ad59c4

Lithography-Free Nanofabrication on Various Semiconductors by the Codeposition Etching Technique Reviewed International journal

Shi Q., Kajita S., Ohno N., Tanaka H., Yasuhara R., Fujiwara H., Uehara H.

Langmuir Vol. 40 ( 24 ) page： 12437 - 12442 2024.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Langmuir

Nano-/microstructures can be formed with the aid of small amounts of impurities during deposition with noble gas plasma irradiation, which is referred to as codeposition etching. This can be a new method for lithography-free semiconductor nanofabrication. Here, the codeposition etching method was employed with argon plasma and molybdenum (Mo) impurities on various semiconductors. Structures can be formed only on substrates that have a lower sputtering yield than the seed impurity. The density, area, and height of structures are related to both the impurity deposition rate and the substrate material. Moreover, two mechanisms of impurity nucleation are proposed according to time dependence results for the formation of the structures.

DOI： 10.1021/acs.langmuir.4c00686

PubMed

First results of multi-fluid modeling of detached hydrogen plasmas in a linear plasma device using fluid code LINDA-NU Reviewed International journal

Sugiura K., Ido T., Tanaka H., Natsume H., Masuda S., Hoshino K., Sawada K., Ohno N.

Contributions to Plasma Physics Vol. 2024;e202300150 2024.6

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Contributions to Plasma Physics

In order to simulate hydrogen (H) plasma in the linear plasma device NAGDIS-II, we have modified the fluid code LINDA-NU to allow the simultaneous calculation of multiple ion species consisting of hydrogen atomic ions ((Formula presented.)) and molecular ions ((Formula presented.)). In this simulation, H and (Formula presented.) neutrals are assumed to be uniformly distributed in space in order to obtain initial qualitative results. The fraction of (Formula presented.) ions increases as the (Formula presented.) molecular density increases, and the recombination process between (Formula presented.) and electrons is observed to reduce the particle flux to the target plate. With an increase in H density, the electron density increases due to the decrease in ion flow velocity due to the change exchange process, and the electron temperature decreases to less than 1 eV, leading to the detached plasma formation attributed to the electron-ion recombination process.

DOI： 10.1002/ctpp.202300150

Four-dimensional conditional averaging tomography of rotating plasma ejection from cylindrical detached plasma Reviewed International journal

Tanaka H., Kajita S., Natsume H., Ohno N.

Scientific Reports Vol. 14 ( 1 ) page： 9329 2024.4

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Scientific Reports

Detached plasma formation is a way to reduce the heat load on the wall in magnetic fusion devices. This study proposes a novel analysis technique consisting of the conditional averaging, sliding window, and tomography to reveal the spatiotemporal behavior of the rotating radial ejection event of detached plasma, which further contributes to local heat load reduction. The used equipment is a high-speed camera and an electrostatic probe located at the periphery of the linear plasma device NAGDIS-II. By applying this method, four-dimensional (4D) behavior of the emission structure along time (1D) and space perpendicular and parallel to the magnetic field (3D) was clarified; a rotating distorted structure appears as a precursor, which is then scraped and transported radially and axially. The proposed method is widely applicable to short-term rigid-body rotating structures, especially in linear plasmas.

DOI： 10.1038/s41598-024-59182-5

PubMed

Study of the intermittent plasma structure around the divertor simulation experimental module in GAMMA 10/PDX Invited Reviewed

H.Tanaka, N.Ezumi, T.Sugiyama, H.Gamo, N.Shigematsu, M.Yoshikawa, J.Kohagura, M.Hirata, S.Togo N.Ohno, M.Sakamoto

Physics of Plasmas Vol. 30 ( 3 ) page： 10.1063/5.0129886 2023.3

Increased Photoelectrochemical Performance of Vanadium Oxide Thin Film by Helium Plasma Treatment with Auxiliary Molybdenum Deposition Reviewed International coauthorship

Kajita Shin, Eda Tomoki, Feng Shuangyuan, Tanaka Hirohiko, Bieberle-Hutter Anja, Ohno Noriyasu

ADVANCED ENERGY AND SUSTAINABILITY RESEARCH Vol. 4 page： 2200141 2023.1

Structural correlation of random lasing performance in plasma-induced surface-modified galium nitride Reviewed

Q.Shi, H.Fujiwara, S.Kajita, R.Yasuhara H.Tanaka, N.Ohno,H.Uehara

ACS Applied Optical Materials Vol. 1 page： 412 - 420 2022.12

Corrigendum to “Photoelectrochemical properties of plasma-induced nanostructured tungsten oxide” [Appl. Surf. Sci. 580 (2022) 151979] (Applied Surface Science (2022) 580, (S0169433221030166), (10.1016/j.apsusc.2021.151979)) Invited Reviewed

S.Feng, S.Kajita, M.Higashi, A.Bieberle-Hutter, T.Yoshida, N.Ohno

Applied Surface Science Vol. 599 page： 153668 2022.10

Reduction of pulsed particle load with dynamic pressure induced by transient recycled neutral flux Reviewed International coauthorship International journal

Hayashi Y., Tanaka H., Ohno N., Kajita S., Morgan T., van der Meiden H., Scholten J., Vernimmen J., Natsume H., Sawada K., Masuda S.

Plasma Physics and Controlled Fusion Vol. 64 ( 10 ) page： 105013 2022.9

Bidirectional reflectance distribution function of recrystallized tungsten mono-block exposed to cyclic heat loading Reviewed International journal

Natsume H., Nojiri K., Kajita S., Fukuda M., Ushiki T., Tanaka H., Sugie T., Kitazawa S.i., Kikuchi T., Yokozuka T., Ohno N., Ezato K., Hatae T.

Nuclear Materials and Energy Vol. 33 page： 101243 2022.9

Fuzz Growth Process under He-W Co-Deposition Conditions Reviewed International coauthorship International journal

SHEN Wanqi, KAJITA Shin, TANAKA Hirohiko, SHI Quan, OHNO Noriyasu

Plasma and Fusion Research Vol. 17 ( 0 ) page： 1302094 - 1302094 2022.8

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Plasma Science and Nuclear Fusion Research

Helium (He)-Tungsten (W) co-deposition experiments were conducted in the linear plasma device Co-NAGDIS at a temperature of 1223 K to observe the characteristics of fuzz growth on the W surface with auxiliary W deposition. The dependence on the deposition rate of W was investigated and a clear difference in fuzz thickness was found between He-only and co-deposition experiments. In addition, the fuzz structures on a single sample exhibited a spatially nonuniform distribution, which was probably caused by the nonuniformity in the deposition rate.

DOI： 10.1585/pfr.17.1302094

Measurement of the Bidirectional Reflectance Distribution Function of Tungsten Surface Sputtered in Argon Plasma Reviewed

H.Natsume, K.Nojiri, S.Kajita, T.Ushiki, T.Sugie, S.Kitazawa, T.Kikuchi, T.Yokozuka, H.Tanaka, N.Ohno, T.Hatae

Plasma and Fusion Research:Regular Articles Vol. 17 page： 2405041 2022.5

Isotope Effect for Plasma Detachment in Helium and Hydrogen/Deuterium Mixture Plasmas Reviewed International journal

GUO Xinyue, TANAKA Hirohiko, KAJITA Shin, OHNO Noriyasu, HATTORI Shogo, SAWADA Keiji

Plasma and Fusion Research Vol. 17 ( 0 ) page： 2402027 - 2402027 2022.5

Language：English Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Plasma Science and Nuclear Fusion Research

To investigate the isotope effect on the plasma detachment in helium (He) and hydrogen (H)/deuterium (D) mixture plasmas, we performed H2, D2 or He gas puffing into He plasma in the linear plasma device NAGDIS-II. Axial distributions of electron density (ne) and electron temperature (Te) were obtained using a movable Langmuir probe. Additionally, optical emission spectroscopy (OES) was applied to measure axial distributions of Balmer lines and He I lines. When the neutral gas pressure was high (ΔPn = 7 ∼10 mTorr), ne distribution in He-D2 mixture plasma was similar to that in pure He plasma, showing a sharp decrease at the downstream region where Te < 1 eV. In contrast, in He-H2 mixture plasma, a decrease in ne was confirmed from upstream region where Te > 1 eV. The upstream Hα/Hγ in He-H2 plasma was significantly larger than the Dα/Dγ in He-D2 plasma at the same Te. This result indicated that molecular activated recombination (MAR) processes significantly occurred in He-H2 plasma, while electron-ion recombination (EIR) processes were dominant in He-D2 and pure He plasmas.

DOI： 10.1585/pfr.17.2402027

Nitrogen Atom Density Measurements in NAGDIS-T Using Vacuum Ultraviolet Absorption Spectroscopy Reviewed

Study of optical emission spectroscopy in dual frequency synchronized pulsed capacitively coupled discharges with DC bias at low-pressure in Ar/O2/C4F8 plasma etching Reviewed International coauthorship

B.B,Sahu, K.Nakane, K.Ishikawa, M.Sekine, T.Tsutsumi, T.Gohira, Y.Ohya, N.Ohno, M.Hori

Physical Chemistry Chemical Physics Vol. 24 page： 13883 - 13896 2022.5

Changes in morphology and field emission property of nano-tendril bundles after high temperature annealing Reviewed International coauthorship International journal

Zhang R., Kajita S., Hwangbo D., Sinelnikov D., Tanaka H., Ohno N.

Nuclear Materials and Energy Vol. 31 page： 101178 2022.4

An approach to implement a heat flux limit in a model for fusion relevant plasmas Reviewed International coauthorship

M.Z.Tokar, M.Kobayashi, N.Ohno

Physics of Plasmas Vol. 29 page： 32502 2022.3

Completion of JT-60SA construction and contribution to ITER Reviewed International coauthorship International journal

Kamada Y., Di Pietro E., Hanada M., Barabaschi P., Ide S., Davis S., Yoshida M., Giruzzi G., Sozzi C., Abdel Maksoud W., Abe H., Aiba N., Akiyama T., Ayllon-Guerola J., Arai T., Artaud J.F., Asakura N., Ashikawa N., Balbinot L., Bando T., Baulaigue O., Belonohy E., Bin W., Bombarda F., Bolzonella T., Bonne F., Bonotto M., Botija J., Cabrera-Pérez S., Cardella A., Carraro L., Cavalier J., Chernyshova M., Chiba S., Clement-Lorenzo S., Cocilovo V., Coda S., Coelho R., Coffey I., Collin B., Corato V., Cucchiaro A., Czarski T., Dairaku M., Davis S., Day C., de la Luna E., De Tommasi G., Decool P., Di Pace L., Di Pietro E., Dibon M., Disset G., Ejiri A., Endo Y., Ezumi N., Falchetto G., Fassina A., Fejoz P., Ferro A., Fietz W., Figini L., Fornal T., Frello G., Fujita T., Fukuda T., Fukui K., Fukumoto M., Furukawa M., Futatani S., Gabellieri L., Gaio E., Galazka K., Garcia J., Garcia-Dominguez J., Garcia-Lopez J., Garcia-Munoz M., Garzotti L., Gasparini F., Gharafi S., Giacomelli L., Ginoulhiac G., Giruzzi G., Giudicotti L., Guillén González R., Hajnal N., Hall S., Hamada K., Hanada K., Hanada M., Hasegawa K., Hatae T., Hatakeyama S., Hauer V., Hayashi N., Hayashi T., Heller R., Higashijima S., Hinata J.

Nuclear Fusion Vol. 62 ( 4 ) page： 42002 2022.3

NISHIO Ryosuke, KAJITA Shin, TANAKA Hirohiko, ASAOKA Koji, TSUTSUMI Takayoshi, HORI Masaru, OHNO Noriyasu

Plasma and Fusion Research Vol. 17 ( 0 ) page： 1201004 - 1201004 2022.1

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：The Japan Society of Plasma Science and Nuclear Fusion Research

For the development of a high nitrogen atom density source, we produced nitrogen plasmas and measured the nitrogen atom density using vacuum ultraviolet absorption spectroscopy (VUVAS) at high neutral gas pressure (>1.5 mTorr) and discharge power (>500 W) in the NAGDIS-T, which could generate spiral-shaped dissociative recombining plasmas. It was seen that the nitrogen atom density increases with increasing neutral gas pressure and discharge power, and it reached 6.2 × 1017 m−3. In the low gas pressure case, the estimated atom density was confirmed to be consistent with that measured by the actinometry method.

DOI： 10.1585/pfr.17.1201004

Plasma induced surface nanostructure on semiconductors for the application of random laser Reviewed

Shi Q., Fujiwara H., Osaka R., Kajita S., Yasuhara R., Ohno N., Uehara H.

Optics InfoBase Conference Papers 2022

Photoelectrochemical properties of plasma-induced nanostructured tungsten oxide Reviewed International coauthorship International journal

Feng S., Kajita S., Higashi M., Bieberle-Hütter A., Yoshida T., Ohno N.

Applied Surface Science Vol. 580 page： 151979(7 pp) 2021.12

Growth of Mo Large-Scale Fiberform Nanostructures Reviewed

Kajita Shin, Okuyama Tatsuki, Tanaka Hirohiko, Ohno Noriyasu

PLASMA AND FUSION RESEARCH Vol. 16 ( 0 ) page： 1206105 - 1206105 2021.12

Language：English Publishing type：Research paper (scientific journal) Publisher：一般社団法人プラズマ・核融合学会

We performed helium (He) plasma irradiation to molybdenum (Mo) substrate with auxiliary Mo deposition. Different from W cases, large-scale fiberform nanostructure (LFN) growth did not occur easily. The experiments suggested that the experimental condition of Mo LFN growth has a much narrower conditional window than that of fuzz growth or another hidden control factor exists for LFN growth.

DOI： 10.1585/pfr.16.1206105

Enhanced photocatalytic ethylene decomposition with anatase-rutile mixed nanostructures formed by He plasma treatment Reviewed

Penetration of deuterium into neutron-irradiated tungsten under plasma exposure Reviewed

Miyuki Yajima, Yuji Hatano, Vladimir Alimov, Takeshi Toyama, Tatsuya Kuwabara, Thomas Schwarz-Selinger, Yasuhisa Oya, Alexander Spitsyn, Noriyasu Ohno

Physica Scripta Vol. 96 ( 12 ) page： 124042 2021.10

The dependence of Mo ratio on the formation of uniform black silicon by helium plasma irradiation Reviewed International coauthorship

Shi Quan, Kajita Shin, Feng Shuangyuan, Ohno Noriyasu

JOURNAL OF PHYSICS D-APPLIED PHYSICS Vol. 54 ( 40 ) page： 405202 2021.10

Kajita S., Miyaguchi K., Tanaka H., Yasunaga E., Yoshida T., Ohno N.

Journal of Photochemistry and Photobiology A: Chemistry Vol. 418 page： 113420(8 pp) 2021.9

Thermal treatment of W large-scale fiberform nanostructures Reviewed

Kajita Shin, Okuyama Tatsuki, Tanaka Hirohiko, Kuwabara Tatsuya, Ohno Noriyasu, Yoshida Naoaki

PHYSICA SCRIPTA Vol. 96 ( 9 ) 2021.9

Enhancement of Arc Ignition on Tungsten in Helium Plasmas with Impurity Gases Reviewed International coauthorship

ZHANG Rongshi, KAJITA Shin, HWANGBO Dogyun, TANAKA Hirohiko, OHNO Noriyasu

Plasma and Fusion Research Vol. 16 ( 0 ) page： 24045069(5 pp) - 2405069 2021.5

Modeling of the impurity-induced silicon nanocone growth by low energy helium plasma irradiation Reviewed International coauthorship

Q Shi, S Kajita, S Dai, S Feng, N Ohno

Plasma Science and Technology Vol. 23 ( 4 ) page： 45503 2021.4

Influence of Nitrogen Ratio on Plasma Detachment during Combined Seeding with Hydrogen on Divertor Simulation Experiment of GAMMA 10/PDX Reviewed

GAMO Hiroki, HWANGBO Dogyun, SAKAMOTO Mizuki, PERILLO Renato, KUWABARA Tatsuya, TANAKA Hirohiko, OHNO Noriyasu, SAWADA Keiji, TONEGAWA Akira, MASUZAKI Suguru, EZUMI Naomichi, SUGIYAMA Tsukasa, NOJIRI Kunpei, KONDO Ayane, HIRATA Mafumi, KOHAGURA Junko, YOSHIKAWA Masayuki, NAKASHIMA Yousuke

Plasma and Fusion Research Vol. 16 ( 0 ) page： 2402041 - 2402041 2021.3

Computer Tomography on Divertor Impurity Monitor for ITER with Miinimizing Errors in a Logarithmic Scale Invited Reviewed International coauthorship

H.Natsume, S.Kajita, V.S.Neverov, R.I.Khusnutdinov, E.Veshchev, M.DE Rock, A.R.Polevoi, H.Tanaka, N.Ohno, H.Ogawa, S.Kitazawa

Plasma and Fusion Research Vol. 16 ( 0 ) page： 2405019 - 2405019 2021.3

Particle-in-cell-Monte Carlo collision simulation and experimental measurement of Ar plasma in a fast atom beam source for surface-activated bonding Reviewed International journal

R.Morisaki, T.Yamazaki, C.Oka, J.Sakurai, T.Hirai, T.Takahashi, H.Tsuji, N.Ohno, S.Hata

Japanese Journal of Applied Physics Vol. 60 ( SC ) page： SCCB01 2021.3

Doppler and Stark Broadenings of He II Emission in NAGDIS-PG Invited Reviewed

S.Kajita, T.Nakamori, H.Tanaka, Y.Kikuchi, N.Ohno

Plasma and Fusion Research: Rapid Communications Vol. 16 ( 0 ) page： 1202013 - 1202013 2021.2

Fabrication of nanostructured Ti thin film with Ti deposition in He plasmas Reviewed

Miyaguchi Kazuya, Kajita Shin, Tanaka Hirohiko, Ohno Noriyasu

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 60 ( 3 ) page： 038004(4 pp) 2021.2

Accelerated/reduced growth of tungsten fuzz by deposition of metals Reviewed International coauthorship

S. Kajita, T. Morgan, H. Tanaka, Y. Hayashi, N. Yoshida, D. Nagata, J. Vernimmen, S. Feng, R. Zhang, N. Ohno

Journal of Nuclear Materials Vol. 548 page： 152844 2021.1

Tungsten Large-Scale Fiberform Nanostructures Retained under High Temperature Conditions Reviewed

T.Okuyama, S.Kajita, N.Yoshida, H.Tanaka, T.Kuwabara, N.Ohno

PLASMA AND FUSION RESEARCH Vol. 16 page： 1206001 2021.1

Experimental observations and modelling of radiation asymmetries during N<inf>2</inf> seeding in LHD Reviewed International coauthorship

B.J. Peterson, G.Kawamura, P.L. van de Giessen, K.Mukai, H.Tanaka, R.Sano, S.N. Pandya, S.Y. Dai, S. Masuzaki, T. Akiyama, M. Kobayashi, M. Goto, G. Motojima, R. Sakamoto, N. Ohno, T. Morisaki, J. Miyazawa, the LHD Experiment Group

Nuclear Materials and Energy Vol. 26 page： 100848 2020.12

Experimental observations and modelling of radiation asymmetries during Ne and N2 seeding in LHD Invited Reviewed International coauthorship

B.J. Peterson, G. Kawamura, P.L. van de Giessen, K. Mukai, S. Borling, H. Tanaka, R. Sano, S. N. Pandya, S. Y. Dai, S. Masuzaki, T. Akiyama, M. Kobayashi, M. Goto, G. Motojima, R. Sakamoto, N. Ohno, T. Morisaki, J. Miyazawa and the LHD Experiment Group

Nuclear Materials and Energy Vol. 26 page： 100848 2020.12

Unipolar arc plasmas on nanostructured tungsten surfaces under perpendicular magnetic field Reviewed International coauthorship

D.Hwangbo, D.Nishijima, S.Kajita, R.Doerner, N.Ohno

PLASMA SOURCES SCIENCE & TECHNOLOGY Vol. 29 ( 12 ) page： 125015 2020.12

Dynamics of Hydrogen Isotope Absorption and Emission of Neutron-Irradiated Tungsten Reviewed International coauthorship

T.Toyama, M.Yajima, N.Ohno, T.Kuwabara, V.Kh.Alimov, Y.Hatano

PLASMA AND FUSION RESEARCH Vol. 15 page： 150581(7 pp) 2020.11

Plasma Potential Measurement in Detached Plasmas by Emissive Probe Considering Space-Charge-Limited Effect Reviewed

S.Hattori, H.Tanka, S.Kajita, N.Ohno

PLASMA AND FUSION RESEARCH Vol. 15 page： 1301082(4 pp) 2020.11

Size distribution of nano-tendril bundles with various additional impurity gases Reviewed

R. Zhang, D. Hwangbo, S. Kajita, H. Tanaka, N. Ohno

NUCLEAR MATERIALS AND ENERGY Vol. 25 page： 100843 2020.11

Tungsten fuzz: Deposition effects and influence to fusion devices Reviewed

S Kajita, N Yoshida, N Ohno

NUCLEAR MATERIALS AND ENERGY Vol. 25 page： 100828 2020.11

Cross-field transport in detached helium plasmas in Magnum-PSI Reviewed International coauthorship

H.Tanaka, Y.Hayashi, S.Kajita, H.J. van der Meiden, M.Yoshikawa, J.W.M.Vernimmen, J.Scholten, I.Classen, T.W.Morgan, N.Ohno

PLASMA PHYSICS AND CONTROLLED FUSION Vol. 62 ( 11 ) page： 115021 (14pp) 2020.10

Nano-tendril bundles behavior under plasma-relevant electric fields Reviewed

V.V.Kulagin, D.N.Sinelnikov, D.G.Bulgadaryan, N.E.Efimov, V.A.Kurnaev, D.Hwangbo, N.Ohno, S.Kajita

VACUUM Vol. 183 page： 109799 2020.10

Evaluation of axial decay length of plasma pressure in detached plasma Reviewed

H.Tanaka, N.Ohno, S.Kajita, H.Takano, S.Hattori, Y.Imaeda

NUCLEAR MATERIALS AND ENERGY Vol. 25 page： 100812(5 pp) 2020.10

Detached helium plasma simulation by a one-dimensional fluid code with detailed collisional-radiative model Reviewed

H.Tanaka, I.Saeki, N.Ohno, S.Kajita, T.Ido, H. Natsume, A.Hatayama, K.Hoshino, K.Sawada, M.Goto

PHYSICS OF PLASMAS Vol. 27 ( 10 ) page： 102505 2020.10

Dust Formation from Arc Spots on Nanostructured Tungsten Surface Reviewed International coauthorship

M.Yajima, S.Kajita, N.Ohno, S.Masuzaki, N.Yoshida, D.U.B.Assems, T.W.Morgan, K.Bystrovc, H, van der Meiden

PLASMA AND FUSION RESEARCH Vol. 15 page： 1205061(3 pp) 2020.8

Atomic nitrogen density measurements by actinometry method in the toroidal device NAGDIS-T Reviewed

S.Kajita, K.Asaoka, H.Tanaka, R.Nishio, T.Tsutsumi, M.Hori, N.Ohno

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 59 ( 8 ) page： 086002(6 pp) 2020.8

Effect of temperature and incident ion energy on nanostructure formation on silicon exposed to helium plasma Reviewed International coauthorship

M.Thompson, Q.Shi, S.Kajita, N.Ohno, C.Corr

PLASMA PROCESSES AND POLYMERS Vol. 17 ( 12 ) page： e2000126(7 pp) 2020.8

Helium-W co-deposition layer: TEM observation and D retention Reviewed

S.Kajita, K.Asai, N.Ohno, H. Tanaka, N.Yoshida, D. Nagata, M. Yajima

JOURNAL OF NUCLEAR MATERIALS Vol. 540 page： 152350 2020.7

The influence of impurities on the formation of nanocone structures on silicon surface irradiated by low energy helium plasma Reviewed

Q.Shi, S. Kajita, N. Ohno, M.Tokitani, D.Nagata, S. Feng

JOURNAL OF APPLIED PHYSICS Vol. 128 ( 2 ) page： 23301 2020.7

Thin film and noble metal loading effects on the photocatalytic reactivity of helium-plasma-induced nanostructured tungsten oxides Reviewed

S.Feng, S.Kajita, T.Yoshida, N.Ohno, D.Nagata, M.Tokitani

MATERIALS RESEARCH EXPRESS Vol. 7 page： 75007 2020.7

Spatiotemporal dynamics of cross-field ejection events in recombining detached plasma Reviewed

H.Tanaka, S.Kajita, H.Natsume, I.Saeki, N.Ohno

PLASMA PHYSICS AND CONTROLLED FUSION Vol. 62 ( 7 ) page： 075011(10 pp) 2020.6

Application of dynamic mode decomposition to rotating structures in detached linear plasmas Reviewed

H.Natsume, H. Tanaka, S. Kajita, N.Ohno

PHYSICS OF PLASMAS Vol. 27 ( 4 ) page： 42301 2020.4

Modifications of WNOx films by keV D and H ions Reviewed

N.Matsunami, N.Ohno, M. Tokitani, B. Tsuchiya, M. Sataka, S. Okayasu

SURFACE & COATINGS TECHNOLOGY Vol. 394 page： 125798 2020.4

Inspection of Arc Trails Formed in Stellarator/Heliotron Devices W7-X and LHD Reviewed International coauthorship

Hwangbo Dogyun, Kajita Shin, Dhard Chandra Prakash, Tokitani Masayuki, Krause Marco, Naujoks Dirk, Masuzaki Suguru, Klose Soeren, Ohno Noriyasu

PLASMA AND FUSION RESEARCH Vol. 15 page： 2402012 2020.3

Helium irradiation effects on the surface modification and recrystallization of tungsten Reviewed International coauthorship

Khan A, De Temmerman G, Kajita S, Greuner H, Balden M, Hunger K, Ohno N, Hwangbo D, Tomita Y, Tokitani M, Nagata D, Yajima M

PHYSICA SCRIPTA Vol. T171 ( 1 ) page： 14050 2020.3

Microstructure and Retention in He-W Co-Deposition Layer Reviewed

K.Asai, N.Yoshida, N.Ohno, S.Kajita, H.Tanaka, M.Yajima, D.Nagata

PLASMA AND FUSION RESEARCH Vol. 15 page： 1201004 2020.2

Growth of nano-fibers on HCP-metals by He plasma irradiation Reviewed

S.Kajita, T.Nojima, Y.Yamamoto, N.Yoshida, T.Okuyama, T.Kuwabara, N.Ohno

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 59 ( SH ) page： SHHA03 2020.2

First EMC3-EIRENE modelling of JT-60SA edge plasmas with/without resonant magnetic perturbation field Reviewed International coauthorship

H.Tanaka, G.Kawamura, K.Hoshino, M.Kobayashi, G.Matsunaga, Y.Suzuki, T.Lunt, Y.Feng, N.Ohno

CONTRIBUTIONS TO PLASMA PHYSICS Vol. 60 ( 5-6 ) page： e201900114 2020.2

Dynamics of the changes in the parameters of the arc plasma during the destruction of a helium-induced tungsten fuzz by arc pulses Reviewed International coauthorship

S. A.Barengolts , D.Hwangbo , S.Kajita , N.Ohno , V. P.Frolova , A. G.Nikolaev , E. M.Oks , D. L.Shmelev , M. M.Tsventoukh , G. Yu Yushkov

NUCLEAR FUSION Vol. 60 ( 4 ) page： 44001 2020.2

Photocatalytic application of helium plasma induced nanostructured tungsten oxides Reviewed

S.Feng, S.Kajita, Y.Tomita, T.Yoshida, N.Ohno

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 59 ( SA ) page： SAAB04(6 pp) 2019.11

Helium-plasma–induced straight nanofiber growth on HCP metals Reviewed

S.Kajita, T.Nojima, T.Okuyama, Y.Yamamoto, N.Yoshida, N.Ohno

Acta Materialia Vol. 181 page： 342 - 351 2019.10

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

© 2019 Acta Materialia Inc. Low-energy helium (He) plasma irradiations were conducted on ruthenium (Ru) and rhenium (Re), which have hexagonal close packed (HCP) crystal structures. Growth of linear shaped fiberform nanostructures were identified on the surfaces of the both metals after the He plasma irradiation. We also conducted He plasma irradiation while Re particles were deposited on tungsten substrate; 3-mm-thick large scale fiberform nanostructures were grown on the surface. The crystal orientation was analyzed using diffraction patterns of Re and Ru nanofibers together with detailed transmission electron microscope observations. It was found that the growth of linear nanofibers has a preferential crystal orientation in the growth direction and it is always in the c-direction of the HCP crystals. Potential growth processes and mechanisms are proposed based on the experimental observations.

DOI： 10.1016/j.actamat.2019.09.053

Kinetics of deuterium penetration into neutron-irradiated tungsten under exposure to high flux deuterium plasma Reviewed

Field Emission From Nanostructured Tendril Bundles Reviewed International coauthorship

D.Sinelnikov, D.Bulgadaryan, D.Hwangbo, S.Kajita, V.Kumaev, N.Ohno

IEEE TRANSACTIONS ON PLASMA SCIENCE Vol. 47 ( 11 ) page： 5186 - 5190 2019.10

M. Yajima, Y. Hatano, N. Ohno, T. Kuwabara, T. Toyama, M. Takagi, K. Suzuki

Nuclear Materials and Energy Vol. 21 page： 100699 2019.8

Language：English Publishing type：Research paper (scientific journal)

© 2019 The Authors The objective of this study is to investigate the effects of neutron (n) irradiation on hydrogen isotope transport in tungsten (W). W samples were irradiated with neutrons in a fission reactor and then exposed to high flux deuterium (D) plasma at 563 K in a linear plasma device. The fraction of D release increased with increasing exposure time. In addition, the D retention in n-irradiated W increased in proportion to the square root of the plasma exposure time. These observations were explained by increase in the penetration depth of D with filling up displacement damages acting as strong trapping sites.

DOI： 10.1016/j.nme.2019.100699

Spatial and temporal measurement of recombining detached plasmas by laser Thomson scattering Reviewed

Application of Ion Sensitive Probe to High Density Plasmas in Magnum-PSI Reviewed International coauthorship

Y.Hayashi, N.Ohno, H.van der Meiden, J.Scholten, S.Kajita, J.van der Berg, R.Perillo, J.Vernimmen, T.Moragan

PLASMA AND FUSION RESEARCH Vol. 14 page： 1202135(3 pp) 2019.7

S. Kajita, H. Ohshima, H. Tanaka, M. Seki, H. Takano, N. Ohno

PLASMA SOURCES SCIENCE & TECHNOLOGY Vol. 28 page： 105015 (9pp) 2019.7

Photocatalytic decomposition of ethylene using He plasma induced nano-TiO<inf>2</inf> Reviewed

S.Kajita, Y.Tomita, E.Yasunaga, T.Yoshida, K.Miyaguchi, H.Tanaka, N.Ohno

Japanese Journal of Applied Physics Vol. 58 page： 070903(4 pp) 2019.6

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

© 2019 The Japan Society of Applied Physics. Ethylene decomposition via photocatalytic reaction using ultra-violet light was performed using an oxidized titanium (Ti) sheet and/or thin film samples fabricated by helium (He) plasmas treatments. We prepared nanostructured Ti samples formed by He plasma irradiation and additional thin film deposited samples using radio frequency magnetron sputtering. The samples prepared in this study had a slightly lower photocatalytic activity compared to the thin film deposited on tungsten nanostructure samples previously reported; the anatase formation was solely identified on Ti sheet samples and is hopeful for further improvement of photocatalytic activity of plasma treated titania.

DOI： 10.7567/1347-4065/ab2830

Fabrication of a nanostructured TiO<inf>2</inf> photocatalyst using He plasma-irradiated tungsten and ethylene gas decomposition Reviewed

Y.Tomita, S.Kajita, E.Yasunaga, T.Yoshida, N.Ohno, H.Tanaka

Japanese Journal of Applied Physics Vol. 58 ( SE ) page： SEEG01(6 pp) 2019.5

Language：English Publishing type：Research paper (scientific journal)

© 2019 The Japan Society of Applied Physics. Decomposition of ethylene gas by a photocatalyst is an environmentally friendly and sustainable process. We fabricated titanium dioxide thin films deposited on nanostructured tungsten substrates formed by exposure to helium plasma and evaluated their photocatalytic performance. The nanostructures were maintained even after sputtering and annealing, and the proportion of tungsten inside the thin film increased with increasing oxidation temperature. The photocatalytic activity was improved due to formation of the nanostructure.

DOI： 10.7567/1347-4065/ab09c8

Investigation of recombination front region in detached plasmas in a linear divertor plasma simulator Reviewed International coauthorship

N.Ohno, M.Seki, H.Ohshima, H.Tanaka, S.Kajita, Y.Hayashi, H.Natsume, H.Takano, I.Saeki, M.Yoshikawa, H.van der Meiden

Nuclear Materials and Energy Vol. 19 page： 458 - 462 2019.5

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

We have investigated detailed plasma structure around the recombination front region (RFR), where volume electron-ion recombination (EIR) strongly occurs in detached plasmas, by using two-dimensional (2D) movable probe system as well as laser Thomson scattering diagnostics. The 2D distribution of electron density, electron temperature, and plasma potential around the RFR, has been revealed for the first time. The spatial distribution of the particle loss rate due to EIR estimated from electron temperature and electron density profiles indicated that the three-dimensional structure of the RFR adopts a cone structure. Furthermore, in the peripheral region of the RFR, the radial profile of the electron density was widened locally with increasing cross-field transport caused by plasma fluctuation. From the heat transport analysis of electrons, it was found that the thermal relaxation process between electrons and ions is important for the cooling of electrons, and that the convection of electrons regulates electron heat transport near the RFR.

DOI： 10.1016/j.nme.2019.03.010

Generation of Spiral Shape Nitrogen Recombining Plasma for Atomic Nitrogen Source Reviewed

K. Asaoka, N. Ohno, Y. Hayashi, S. Kajita, and H. Tanaka

Plasma and Fusion Research Vol. 14 page： 3401069(4 pp) 2019.4

Characterization of He induced nanostructures using SEM image analysis Reviewed

H.Tanaka, S.Kajita, N.Ohno

Plasma and Fusion Research Vol. 14 ( Specialissue2 ) page： 3402049(6 pp) 2019.4

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

© 2019 The Japan Society of Plasma Science and Nuclear Fusion Research. Helium induced nanostructures on tungsten were characterized by applying basic statistical analysis techniques to scanning electron microscope (SEM) images. As the analysis targets, pinhole- and fuzz-dominant surfaces irradiated with different ion fluences were employed. Although two-dimensional Fourier analysis of the normalized brightness of SEM images clarified several characteristic features, their differences are small to distinguish the dominant nanostructures. On the other hand, probability density functions (PDFs) of the normalized brightness indicate that hole- and fuzz-dominant surfaces have long tail and Gaussian-like shape, respectively. By using several indexes with considering the black and white saturation, it was found that kurtosis and Kullback- Leibler divergence could provide reasonable judgement as the characterization index.

DOI： 10.1585/pfr.14.3402049

Ignition and Behavior of Arc Spots on Helium Irradiated Tungsten under Fusion Relevant Condition Reviewed

Synergistic effect of nitrogen and hydrogen seeding gases on plasma detachment in the GAMMA 10/PDX tandem mirror Reviewed

N.Ezumi, T.Iijima, M.Sakamoto, Y.Nakashima, M.Hirata, M.Ichimura, R.Ikezoe, T.Imai, T.Kariya, I.Katanuma, J.Kohagura, R.Minami, T.Numakura, M. Yoshikawa, S. Togo, MD S.Islam, MD M.Islam, K.Nojiri, A.Terakado, S.Jang, Y.Kinoshita, T.Mikami, S.Yamashita, T.Yoshimoto, T.Hara, A.Hatayama, K.Ichimura, S.Kado, S.Masuzaki, T.Nakano, N.Ohno, K. Sawada, H. Tanaka, A.Tonegawa and R.Perillo

Nuclear Fusion Vol. 59 page： 060030 2019.4

S.Kajita, D.Hwangbo, N.Ohno

IEEE Transactions on Plasma Science Vol. 47 ( 8 ) page： 3909 - 3916 2019.4

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

© 1973-2012 IEEE. In nuclear fusion reactors, unipolar arcing is a longstanding plasma surface interaction issue. In this paper, short summaries of morphology changes by helium plasma irradiation under fusion relevant conditions and ignition of arcing on the He irradiated surfaces are given. Helium plasma irradiation leads to surface morphology changes, and arcing can be ignited on the surface in response to pulsed heat load accompanied by plasma instabilities. Then, we focused on arcing ignited on large-scale fiberform nanostructures (LFNs) formed with deposition of metallic particles together with helium-ion irradiation. Dusts release from the arc spot and the amount of material erosion are discussed based on the experiments.

DOI： 10.1109/TPS.2019.2908193

Increased energy absorption into W due to the metal deposited layer from an ELM-like pulsed plasma Reviewed

Analysis of indefinite divertor footprint with proper orthogonal decomposition in hydrogen/deuterium plasmas in LHD Reviewed

H.Tanaka, S.Masuzaki, G.Kawamura, M.Kobayashi, Y.Suzuki, T.Morisaki, N.Ohno LHD Experimental Group

Nuclear Materials and Energy Vol. 19 page： 378 - 383 2019.3

T.Nakamori, N.Ohno, H.Tanaka, S.Kajita, Y.Kikuchi, T.Akiyama

Plasma and Fusion Research Vol. 14 page： 1401051(5 pp) 2019.3

Language：English Publishing type：Research paper (scientific journal)

© 2019 The Japan Society of Plasma Science and Nuclear Fusion Research. It is important in divertor physics research to investigate thermal response process of beryllium deposited tungsten to high transient heat load such as ELMs. We investigated the heat load on aluminum-coated tungsten by comparing the measured back surface temperature and calculation results of the one-dimensional heat conduction equation. When the plasma power was low enough so that the evaporation did not occur sufficiently, the heat load on the aluminum-coated tungsten was higher than the virgin tungsten. It was caused by the reduction in the energy reflection coefficient due to the formation of aluminum layer. The results suggested that the beryllium deposited layer adversely affects the heat load on the divertor plate when the heat load was not high such as Grassy-ELM.

DOI： 10.1585/pfr.14.1401051

Double-probe measurement in recombining plasma using NAGDIS-II Reviewed

Y. Hayashi, H. Nishikata, N. Ohno, S. Kajita, H. Tanaka, H. Ohshima, M. Seki

Contributions to Plasma Physics Vol. 59 ( 7 ) page： e201800088 2019.2

Language：English Publishing type：Research paper (scientific journal)

© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim We have studied the validity of the double-probe method in recombining plasmas. Electron temperature (Te) measured with a double probe was quantitatively evaluated by taking into account the influences of plasma potential fluctuation, plasma resistivity, and electron density fluctuation on the current–voltage characteristics. Differential potential fluctuation and plasma resistivity between two electrodes have a minor effect on Te especially when the inter-distance is small (typically 1 mm). Scattering of measured Te due to the density fluctuation was sufficiently suppressed by making the data acquisition time long (typically 4 s) and taking the average. There is a good agreement between Te measured with the optimized double-probe method and that with laser Thomson scattering diagnostics.

DOI： 10.1002/ctpp.201800088

Development of Thomson scattering measurement system for Upstream plasmas in the NAGDIS-II device Reviewed

H.Takano, H.Ohshima, S.Kajita, H.Tanaka, N.Ohno

Plasma and Fusion Research Vol. 14 ( Specialissue1 ) page： 2405031(4 pp) 2019.2

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

© 2019 The Japan Society of Plasma Science and Nuclear Fusion Research. A new laser Thomson scattering (LTS) measurement system in the upstream region of the linear plasma device NAGDIS-II is established in addition to the recently introduced LTS in the downstream. Further, horizontal distributions of the electron temperature and electron density were compared with those obtained from the Langmuir probe, indicating plasma disturbance due to the insertion of the probe head. We discuss the variation of the electron energy distribution function at upstream and downstream in the recombining plasma.

DOI： 10.1585/pfr.14.2405031

Growth of membrane nanostructures on W co-deposition layer Reviewed

S. Kajita, N. Yoshida, S. Kawaguchi, H. Tanaka, N. Ohno, D. Nagata, M. Tokitani

Nuclear Materials and Energy Vol. 18 page： 339 - 344 2019.2

Language：English Publishing type：Research paper (scientific journal)

© 2019 The Authors Large-scale mm thick fiberform nanostructures are grown when materials are subjected to high flux helium ions with tungsten particles (ions and neutrals) precipitation. Observations of the large-scale fiberform nanostructures (LFNs) were conducted by scanning electron microscope (SEM) and transmission electron microscope (TEM) analyses. In particular, this study focuses on membrane nanostructures. Membranes that contain He bubbles were always observed when LFNs covered the surface. We discuss the growth process of the membrane structures based on detailed observations.

DOI： 10.1016/j.nme.2019.02.004

Spatiotemporal Structure of Hα Emission from the Detached Plasma in GAMMA 10/PDX Reviewed

H.Tanaka, M.Sakamoto, N.Ezumi, A.Terakado, K.Nojiri, T.Mikami, Y.Kinoshita, K.Kobayashi, M.Yoshikawa, J. Kohagura, N.Ohno

Plasma and Fusion Research: Regular Articles Vol. 14 page： 2402036(5 pp) 2019.2

Growth process of nano-tendril bundles with sputtered tungsten Reviewed

D. Hwangbo, S. Kajita, H. Tanaka, and N. Ohno

Nuclear Materials and Energy Vol. 18 page： 250 - 257 2019.1

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

© 2019 The Authors Nano-tendril bundles (NTBs) were generated in DC He plasma with impurity gas-seeding (Ne and N 2 ) under sputtering-dominated conditions. NTB morphologies were characterized using the net erosion yield of samples. NTBs’ height and area were analyzed and ion fluence dependence was discussed. For both impurities, the number of NTBs increased steadily with increasing the fluence. It was revealed that NTB can be generated newly and continuously regardless of ion fluence. Surface observations suggested that micro-protrusions can evolve into NTBs. The effect of re-deposition of W was discussed based on SEM observations. Line-of-sight deposition seemed to play a key role of W feeder to enable NTBs to grow greater.

DOI： 10.1016/j.nme.2019.01.008

Multipoint measurements employing a microwave interferometer and a Langmuir probe in the detached linear plasma Reviewed

H. Natsume, H. Tanaka, S. Kajita, M. Yoshikawa, M. Seki, H. Ohshima, and N. Ohno

AIP ADVANCES Vol. 9 page： 015016 (6pp) 2019.1

Influence of heavier impurity deposition on surface morphology development and sputtering behavior explored in multiple linear plasma devices Reviewed International coauthorship

D.Nishijima, A.Kreter, M.Baldwin, D.Borodin, A.Eksaeva, D.Hwangbo, S.Kajita, M.Miyamoto, N.Ohno, M.Patino, A.Psopieszczyk, M.Rasinski, T.Schlummer, A.Terra, R.P.Doerner

NUCLEAR MATERIALS AND ENERGY Vol. 18 page： 67 - 71 2019.1

Spatiotemporal Structure of H alpha Emission from the Detached Plasma in GAMMA 10/PDX Reviewed

H.Tanaka, M.Sakamoto, N.Ezumi, A.Terakado, K.Nojiri, T.Mikami, Y.Kinoshita, K.Kobayashi, M.Yoshikawa, J. Kohagura, N.Ohno

PLASMA AND FUSION RESEARCH Vol. 14 ( Specialissue1 ) page： 2402036(5 pp) 2019.1

Effect of Damage Introduction and He Existence on D Retention in Tungsten by High Flux D Plasma Exposure Reviewed

Yasuhisa Oya, Keisuke Azuma, Akihiro Togari, Moeko Nakata, Qilai Zhou, Mingzhong Zhao, Tatsuya Kuwabara, Noriyasu Ohno, Miyuki Yajima, Yuji Hatano, Takeshi Toyama

Lecture Notes in Networks and Systems Vol. 53 ( 8 ) page： 89 - 96 2019

Proton scattering from tungsten fuzz

D. Bulgadaryan, D. Sinelnikov, V. Kurnaev, S. Kajita, D. Hwangbo, N. Ohno

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms Vol. 434 page： 9 - 12 2018.11

Language：English Publishing type：Research paper (scientific journal)

© 2018 Elsevier B.V. Tungsten fuzz is a nanostructure formed on tungsten surface under helium plasma impact. In this work, we investigate this structure using the scattering of keV-energy protons. Energy spectra of scattered protons have double-peak shape that corresponds to the scattering from fuzz and underlying pure tungsten. The energy losses of protons in fuzz are estimated as the difference between primary beam energy and the energy corresponding to the local minimum between two peaks. Computer simulations with SRIM code also demonstrate double-peak shape of energy spectra of protons scattered from fuzzy target. Fuzz and pure tungsten stopping powers for protons are compared and fuzz density relative to pure tungsten is estimated and discussed. Evolution of H+energy spectra during fuzz irradiation by Ar+beam is measured and discussed.

DOI： 10.1016/j.nimb.2018.07.038

Characterized divertor footprint profile modification with the edge pressure gradient in the Large Helical Device Reviewed

Plasma exhaust and divertor studies in Japan and Europe broader approach, DEMO design activity Reviewed International coauthorship

N.Asakura, K.Hoshino , H.Utoh, Y.Someya, S.Suzuki, C.Bachmann, H.Reimerdes, R.Wenninger, H.Kudo, S.Tokunaga, Y.Hommai, Y.Sakamoto, R.Hiwatari, K.Tobita, Jeong-Ha You, G.Federici, K.Ezato, Y.Seki, ...N.Ohno

FUSION ENGINEERING AND DESIGN Vol. 136 page： 1214 - 1220 2018.11

Tanaka H., Masuzaki S., Kawamura G., Kobayashi M., Suzuki Y., Motojima G., Murase T., Morisaki T., Ohno N.

PLASMA PHYSICS AND CONTROLLED FUSION Vol. 60 ( 12 ) page： 125001 2018.10

Morphologies of co-depositing W layer formed during He plasma irradiation Reviewed

Kajita Shin, Kawaguchi Shota, Yoshida Naoaki, Ohno Noriyasu, Tanaka Hirohiko

NUCLEAR FUSION Vol. 58 ( 10 ) page： 106002 2018.10

One-Step Plasma Synthesis of Nb<inf>2</inf>O<inf>5</inf> Nanofibers and their Enhanced Photocatalytic activity Reviewed

S.Kajita, F.Mimuro, T.Yoshida, N.Ohno, N.Yoshida

ChemPhysChem Vol. 19 ( 23 ) page： 3237 - 3246 2018.9

Language：English Publishing type：Research paper (scientific journal)

© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Fiberform nanostructured niobium (Nb) was fabricated by one step helium (He) plasma irradiation. He ion implantation formed He nano-bubbles on a Nb plate and led to formation of protrusions while migrating in Nb matrix; fiberform nanostructures (FN) were grown when the fluence became high (>1026 m−2). The necessary conditions for the formation of Nb FN were revealed to be the surface temperature range of 900–1100 K and the incident ion energy higher than 70 eV. The sample was oxidized at 573–773 K in an air atmosphere, and Pt nanoparticles were photo-deposited on the Nb2O5 samples. The surface was analyzed by scanning electron microscope, transmission electron microscope, x-ray photoelectron spectroscopy, and ultraviolet-visible spectrophotometry. Photocatalytic activity of the fabricated materials was studied using methylene blue (MB) decolorization process. An enhanced photocatalytic performance was identified on FN Nb2O5 substrate with Pt deposition.

DOI： 10.1002/cphc.201800769

Thomson Scattering Measurement of Two Electron Temperature Components in Transition to Detached Plasmas Reviewed

Growth of nano-tendril bundles on tungsten with impurity-rich He plasmas Reviewed

Hwangbo Dogyun, Kajita Shin, Ohno Noriyasu, McCarthy Patrick, Bradley James W, Tanaka Hirohiko

NUCLEAR FUSION Vol. 58 ( 9 ) page： 096022 2018.9

Ohshima Hiroshi, Kajita Shin, Tanaka Hirohiko, Ohno Noriyasu, Van der Meiden Hennie J

PLASMA AND FUSION RESEARCH Vol. 13 page： 1201099 2018.8

Effect of the Nanostructured Layer Thickness on the Dynamics of Cathode Spots on Tungsten Reviewed International coauthorship

S.A. Barengolts, V.G. Mesyats, M. M. Tsventoukh, S.Kajita, D.Hwangbo, N.Ohno

IEEE Transactions on Plasma Science Vol. 46 ( 11 ) page： 4044 - 4050 2018.8

Authorship：Last author Language：English Publishing type：Research paper (scientific journal)

IEEE Experimental data on the effect of the thickness of a nanostructured layer present on the surface of a tungsten cathode on its arcing properties have been analyzed. It has been shown that if the nanostructured layer is not completely destroyed as a result of the operation of a cathode spot cell, the spot ``sinks'' in the layer, the spot cells group together, and the trajectory of the spot motion becomes ``entangled.'' To interpret the experimental results, the grouping of arc spot cells was simulated using a random walk model based on the Monte Carlo method into which an attractive force was introduced and assuming that the cell plasma density, i.e., the cell initiation probability, is proportional to 1/r&#x00B2;, where r is the distance between two spot cells. It has been demonstrated that spot cells are entangled, forming a group and moving together when the attractive force between them is strong enough. When this force decreases and the directionality of the cells increases as the cathode spot shifts to a lower thickness region of the nanostructured layer, the velocity of motion of the spot increases and its trace left on the surface becomes narrower.

DOI： 10.1109/TPS.2018.2859953

Blob- and hole-like structures outstanding during the transition from attached to detached divertor states in GAMMA 10/PDX Reviewed

Tanaka, H, Sakamoto, M, Ezumi, N, Nojiri, K, Terakado, A, Mikami, T, Kinoshita, Y, Kobayashi, K, Yoshikawa, M, Kohagura, J, Ohno, N

PHYSICS OF PLASMAS Vol. 25 ( 8 ) page： 082505(6 pp) 2018.8

Localized spiraling plasma ejection contributing the ion-flux broadening in the detached linear plasma Reviewed

Tanaka, H, Takeyama, K, Yoshikawa, M, Kajita, S, Ohno, N, Hayashi, Y

PLASMA PHYSICS AND CONTROLLED FUSION Vol. 60 ( 7 ) page： 075013 2018.7

Ignition and erosion of materials by arcing in fusion-relevant conditions Reviewed

Hwangbo Dogyun, Kajita Shin, Barengolts Sergey A, Tsventoukh Mikhail M, Kawaguchi Shota, Mesyats Vadim G, Ohno Noriyasu

CONTRIBUTIONS TO PLASMA PHYSICS Vol. 58 ( 6-8 ) page： 608 - 615 2018.7

Helium line emission spectroscopy in recombining detached plasmas Reviewed

Shin Kajita, Kensuke Suzuki, Hirohiko Tanaka, Noriyasu Ohno

Physics of Plasmas Vol. 25 ( 6 ) page： 063303 2018.6

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：American Institute of Physics Inc.

Line emissions from helium (He) plasmas have been used for measurement of electron density and temperature in various situations. We performed measurements of He line intensities in recombining plasmas in a divertor simulator, followed by discussion of some potential difficulties of using the line intensity ratio (LIR) method in a divertor environment under detached conditions. When using four line emissions (501.6, 667.8, 706.5, and 728.1 nm), the discrepancy of the results compared to results from the laser Thomson scattering (LTS) method increased along with increasing gas pressure. However, the LIR method agreed well with LTS when a recombination sensitive line emission (447.1 nm) was added. The influence of the transport of metastable atoms is also discussed. Additionally, anomalous characteristics of the LIR method were revealed in hydrogen helium mixture plasmas when the temperature was in the range of 1-4 eV. These anomalies were likely attributable to the dissociative recombination of HeH+.

DOI： 10.1063/1.5029414

Fabrication of photocatalytically active vanadium oxide nanostructures via plasma route Reviewed

Nanostructure Growth on Rhodium/Ruthenium by the Exposure to He Plasma Reviewed

Tomohiro NOJIMA, Shin KAJITA, Naoaki YOSHIDA, Shota KAWAGUCHI, Noriyasu OHNO, Hirohiko TANAKA, Masayuki TOKITANI, Daisuke NAGATA, Tsuyoshi AKIYAMA, Takashi YAGI

Plasma and Fusion Research Vol. 13 page： 3406064 2018.6

Mode Structure Analysis of Detached Plasmas with 2D Images Reviewed

Kajita Shin, Tanaka Hirohiko, Ohno Noriyasu, Onda Takuya

PLASMA AND FUSION RESEARCH Vol. 13 page： 1402033(5 pp) 2018.5

Shin Kajita, Tomoko Yoshida, Noriyasu Ohno, Yusuke Ichino, Naoaki Yoshida

Journal of Physics D: Applied Physics Vol. 51 ( 21 ) page： 215201 2018.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Institute of Physics Publishing

Plasma irradiation was used to create nanostructured vanadium oxide with potential commercial and industrial applications. Morphology changes were induced at the nano- and micro-meter scale, accompanied by the growth of helium nanobubbles. Micrometer-sized pillars, cube-shaped nanostructures, and fuzzy fiberform nanostructures were grown on the surface
the necessary conditions in terms of the incident ion energy and the surface temperature for those morphology changes were revealed. Hydrogen production experiments using a photocatalytic reaction with aqueous methanol solution were conducted on the fabricated samples. Enhanced H2 production was confirmed with the plasma irradiated nanostructured sample that had been oxidized in air atmosphere. Photocatalytically inactive vanadium oxide exhibited a high photocatalytic activity after nanostructurization of the surface by helium plasma irradiation.

DOI： 10.1088/1361-6463/aabe44

Fuzzy nanostructure growth on precious metals by He plasma irradiation Reviewed

Shin Kajita, Tomohiro Nojima, Yudai Tomita, Noriyasu Ohno, Hirohiko Tanaka, Naoaki Yoshida, Miyuki Yajima, Tsuyoshi Akiyama, Masayuki Tokitani, Takashi Yagi

Surface and Coatings Technology Vol. 340 page： 86 - 92 2018.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier B.V.

Growth of helium bubbles near the surface of metals leads to various morphology changes when sufficient helium ions are continuously implanted on the surface. In this study, low energy (&lt
100 eV) helium plasma irradiations to various noble metals were conducted, and consequent surface morphology changes were analyzed. It was found that fiberform nanostructures were formed by the helium plasma irradiation on rhodium and ruthenium thin films, which were deposited by magnetron sputtering, and on platinum and iridium wires. Growth of fiberform structures were not identified on gold, silver, and palladium samples exposed to helium plasmas even though the irradiations were conducted at various surface temperatures, though pinholes were observed on palladium surface. We discussed the relation between the morphology changes and material properties.

DOI： 10.1016/j.surfcoat.2018.02.026

Measurement of He neutral temperature in detached plasmas using laser absorption spectroscopy Reviewed

Pulsation Effects of Incident Ion Energy on W Fuzz Growth Reviewed

Kajita Shin, Kawaguchi Shota, Hwangbo Dogyun, Tanaka Hirohiko, Ohno Noriyasu

PLASMA AND FUSION RESEARCH Vol. 13 page： 1205001 2018.1

Aramaki M., Tsujihara T., Kajit S., Tanaka H., Ohno N.

AIP ADVANCES Vol. 8 ( 1 ) page： 015308 2018.1

Analysis of ELM stability with extended MHD models in JET, JT-60U and future JT-60SA tokamak plasmas Reviewed

Aiba N., Pamela S., Honda M., Urano H., Giroud C., Delabie E., Frassinetti L., Lupelli I., Hayashi N., Huijsmans G.T.A., Litaudon X., Abduallev S., Abhangi M., Abreu P., Afzal M., Aggarwal K.M., Ahlgren T., Ahn J.H., Aho-Mantila L., Airila M., Albanese R., Aldred V., Alegre D., Alessi E., Aleynikov P., Alfier A., Alkseev A., Allinson M., Alper B., Alves E., Ambrosino G., Ambrosino R., Amicucci L., Amosov V., Sundén E.A., Angelone M., Anghel M., Angioni C., Appel L., Appelbee C., Arena P., Ariola M., Arnichand H., Arshad S., Ash A., Ashikawa N., Aslanyan V., Asunta O., Auriemma F., Austin Y., Avotina L., Axton M.D., Ayres C., Bacharis M., Baciero A., Baião D., Bailey S., Baker A., Balboa I., Balden M., Balshaw N., Bament R., Banks J.W., Baranov Y.F., Barnard M.A., Barnes D., Barnes M., Barnsley R., Wiechec A.B., Orte L.B., Baruzzo M., Basiuk V., Bassan M., Bastow R., Batista A., Batistoni P., Baughan R., Bauvir B., Baylor L., Bazylev B., Beal J., Beaumont P.S., Beckers M., Beckett B., Becoulet A., Bekris N., Beldishevski M., Bell K., Belli F., Bellinger M., Belonohy , Ayed N.B., Benterman N.A., Bergsåker H., Bernardo J., Bernert M., Berry M., Bertalot L., Besliu C., Beurskens M.

Plasma Physics and Controlled Fusion Vol. 60 ( 1 ) 2018.1

Language：Japanese Publisher：Plasma Physics and Controlled Fusion

The stability with respect to a peelingballooning mode (PBM) was investigated numerically with extended MHD simulation codes in JET, JT-60U and future JT-60SA plasmas. The MINERVA-DI code was used to analyze the linear stability, including the effects of rotation and ion diamagnetic drift (w∗i), in JET-ILW and JT-60SA plasmas, and the JOREK code was used to simulate nonlinear dynamics with rotation, viscosity and resistivity in JT-60U plasmas. It was validated quantitatively that the ELM trigger condition in JET-ILW plasmas can be reasonably explained by taking into account both the rotation and w∗i effects in the numerical analysis. When deuterium poloidal rotation is evaluated based on neoclassical theory, an increase in the effective charge of plasma destabilizes the PBM because of an acceleration of rotation and a decrease in w∗i. The difference in the amount of ELM energy loss in JT-60U plasmas rotating in opposite directions was reproduced qualitatively with JOREK. By comparing the ELM affected areas with linear eigenfunctions, it was confirmed that the difference in the linear stability property, due not to the rotation direction but to the plasma density profile, is thought to be responsible for changing the ELM energy loss just after the ELM crash. A predictive study to determine the pedestal profiles in JT-60SA was performed by updating the EPED1 model to include the rotation and w∗i effects in the PBM stability analysis. It was shown that the plasma rotation predicted with the neoclassical toroidal viscosity degrades the pedestal performance by about 10% by destabilizing the PBM, but the pressure pedestal height will be high enough to achieve the target parameters required for the ITER-like shape inductive scenario in JT-60SA.

DOI： 10.1088/1361-6587/aa8bec

Enhanced growth of large-scale nanostructures with metallic ion precipitation in helium plasmas Reviewed

Shin Kajita, Shota Kawaguchi, Noriyasu Ohno, Naoaki Yoshida

Scientific Reports Vol. 8 page： 56 2018.1

Language：English Publishing type：Research paper (scientific journal) Publisher：Nature Publishing Group

Helium plasma irradiation on metal surfaces leads to the formation of metallic fuzzy nanostructures accompanied by the growth of helium bubbles in metals. The mechanism of the growth process, its impact for fusion devices, and potential application have been explored. Here we show enhanced growth of large-scale fuzz by precipitating additional metallic particles during helium plasma irradiation. The growth rate of the fuzzy structures became orders of magnitude greater than conventional fuzz growth
in an hour of irradiation, 1 mm-thick visible tungsten and molybdenum fuzzy fur structures covered a tungsten metal substrate. Additional precipitation of metallic ions breaks the bottleneck diffusion process
moreover, further acceleration in the growth rate could have occurred if the electric sheath shape was influenced by the grown structure and the electric field that formed around the structure started collecting ions.

DOI： 10.1038/s41598-017-18476-7

Recent progress of divertor simulation research using the GAMMA 10/PDX tandem mirror Reviewed

Morphology Changes of Platinum and Tungsten Carbide by He Plasma Irradiation Reviewed

Tomita Yudai, Kajita Shin, Ohno Noriyasu, Tanaka Hirohiko, Ichino Yusuke

PLASMA AND FUSION RESEARCH Vol. 13 page： 3406074 2018

Nakashima Y, Ichimura K, Islam M. S, Sakamoto M, Ezumi N, Hirata M, Ichimura M, Ikezoe R, Imai T, Kariya T, Katanuma I, Kohagura J, Minami R, Numakura T, Yoshikawa M, Iijima T, Islam M. M, Nojiri K, Shimizu K, Terakado A, Togo S, Asakura N, Fukumoto M, Hatayama A, Hirooka Y, Kado S, Kubo H, Masuzaki S, Matsuura H, Nakano T, Nagata S, Nishino N, Ohno N, Sagara A, Sawada K, Shoji M, Tonegawa A, Ueda Y

NUCLEAR FUSION Vol. 57 ( 11 ) 2017.11

Language：English Publishing type：Research paper (scientific journal)

© 2017 IAEA, Vienna. This paper describes the recent progress in divertor simulation research using the GAMMA 10/PDX tandem mirror towards the development of divertors in fusion reactors. During a plasma flow generation experiment in the end cell of the GAMMA 10/PDX, ICRF heating in the anchor cell successfully extended the particle flux up to 3.3 1023 m2 s-1. Superimposing the short pulse of the ECH also attained a maximum heat flux of ∼30 MW m-2. We have succeeded in achieving and characterizing the detachment of the high-temperature plasma, which is equivalent to the SOL plasma of tokamaks, by using the divertor simulation experimental module (D-module) in the GAMMA 10/PDX end cell, in spite of using a linear device with a short magnetic field line connection length. Various gases (Ar, Xe, Ne and N2) are examined to evaluate the effect of radiation cooling against the plasma flow at the MW m-2 level in the divertor simulation region and the following results are obtained: (i) Xe gas was most effective in the reduction of heat and particle fluxes (1%, 3%, respectively) and has a stronger effect on electron cooling (down to ∼1.6 eV) in the used gas species. (ii) Ne gas was less effective. On the other hand, (iii) N2 gas showed more favorable effects than Ar in the lower pressure range. These results will contribute to the progress in detached plasma operation and in clarifying the radiation cooling mechanism towards the development of future divertors.

DOI： 10.1088/1741-4326/aa7cb4

Development of a Compact Divertor Plasma Simulator for Plasma-Wall Interaction Studies on Neutron-Irradiated Materials Reviewed

N.Ohno, T.Kuwabara, M.Takagi, R.Nishimura, M.Yajima, A.Sagara, T.Toyama, K.Suzuki, H.Kurishita, T.Shikama, Y.Hatano, N.Yoshida

Plasma and Fusion Research Vol. 12 ( 0 ) page： 1405040 - 1405040 2017.10

Studies of power exhaust and divertor design for a 1.5 GW-level fusion power DEMO Reviewed

N.Asakura, K.Hoshino, S.Suzuki, S.Tokunaga, Y.Someya, H.Utoh, H.Kudo, Y.Sakamoto, R.Hiwatari, K.Tobita, K.Shimizu, K.Ezato, Y.Seki, N.Ohno, Y.Ueda, Joint Special Team for DEMO Design

Nuclear Fusion Vol. 57 page： 126050(12 pp) 2017.10

Plasma Exhaust and Divertor Studies in JA and EU Broader Tokamak Fusion Reactor Approach, DEMO Design Activity Reviewed

Nobuyuki Asakura, Kazuo Hoshino, Hiroyasu Utoh, Yoji Someya, Satoshi Suzuki, Christian Bachmann, Holger Reimerdes, Hironobu Kudo, Shinsuke Tokunaga, Yuki Homma, Yoshiteru Sakamoto, Ryoji Hiwatari, Ronald Wenninger, Kenji Tobita, Noriyasu Ohno,Gianfranco Federici, Koichiro Ezato, Yohji Seki, Noriyasu Ohno, Yoshio Ueda

2017.9

Extension of the operational regime of the LHD towards a deuterium experiment Reviewed

Takeiri Y., Morisaki T., Osakabe M., Yokoyama M., Sakakibara S., Takahashi H., Nakamura Y., Oishi T., Motojima G., Murakami S., Ito K., Ejiri A., Imagawa S., Inagaki S., Isobe M., Kubo S., Masamune S., Mito T., Murakami I., Nagaoka K., Nagasaki K., Nishimura K., Sakamoto M., Sakamoto R., Shimozuma T., Shinohara K., Sugama H., Watanabe K. Y., Ahn J. W., Akata N., Akiyama T., Ashikawa N., Baldzuhn J., Bando T., Bernard E., Castejon F., Chikaraishi H., Emoto M., Evans T., Ezumi N., Fujii K., Funaba H., Goto M., Goto T., Gradic D., Gunsu Y., Hamaguchi S., Hasegawa H., Hayashi Y., Hidalgo C., Higashiguchi T., Hirooka Y., Hishinuma Y., Horiuchi R., Ichiguchi K., Ida K., Ido T., Igami H., Ikeda K., Ishiguro S., Ishizaki R., Ishizawa A., Ito A., Ito Y., Iwamoto A., Kamio S., Kamiya K., Kaneko O., Kanno R., Kasahara H., Kato D., Kato T., Kawahata K., Kawamura G., Kisaki M., Kitajima S., Ko W. H., Kobayashi M., Kobayashi S., Kobayashi T., Koga K., Kohyama A., Kumazawa R., Lee J. H., Lopez-Bruna D., Makino R., Masuzaki S., Matsumoto Y., Matsuura H., Mitarai O., Miura H., Miyazawa J., Mizuguchi N., Moon C., Morita S., Moritaka T., Mukai K., Muroga T., Muto S., Mutoh T., Nagasaka T., Nagayama Y., Nakajima N., Nakamura Y., Nakanishi H., Nakano H., Nakata M., Narushima Y., Nishijima D., Nishimura A., Nishimura S., Nishitani T., Nishiura M., Nobuta Y., Noto H., Nunami M., Obana T., Ogawa K., Ohdachi S., Ohno M., Ohno N., Ohtani H., Okamoto M., Oya Y., Ozaki T., Peterson B. J., Preynas M., Sagara S., Saito K., Sakaue H., Sanpei A., Satake S., Sato M., Saze T., Schmitz O., Seki R., Seki T., Sharov I., Shimizu A., Shiratani M., Shoji M., Skinner C., Soga R., Stange T., Suzuki C., Suzuki Y., Takada S., Takahata K., Takayama A., Takayama S., Takemura Y., Takeuchi Y., Tamura H., Tamura N., Tanaka H., Tanaka K., Tanaka M., Tanaka T., Tanaka Y., Toda S., Todo Y., Toi K., Toida M., Tokitani M., Tokuzawa T., Tsuchiya H., Tsujimura T., Tsumori K., Usami S., Velasco J. L., Wang H., Watanabe T. -H., Watanabe T., Yagi J., Yajima M., Yamada H., Yamada I., Yamagishi O., Yamaguchi N., Yamamoto Y., Yanagi N., Yasuhara R., Yatsuka E., Yoshida N., Yoshinuma M., Yoshimura S., Yoshimura Y.

NUCLEAR FUSION Vol. 57 ( 10 ) 2017.8

Erosion of nanostructured tungsten by laser ablation, sputtering and arcing Reviewed

Dogyun Hwangbo, Shota Kawaguchi, Shin Kajita, Noriyasu Ohno

Nuclear Materials and Energy Vol. 12 page： 386 - 391 2017.8

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier Ltd

Mass loss of nanostructured tungsten, which was formed by helium plasma irradiation, due to laser ablation, sputtering, and arcing was investigated. Below the helium sputtering energy threshold (&lt
117 eV), sputtering by impurity gases such as nitrogen and oxygen was dominant. Sputtering yield became closer to theoretical value with increasing the incident ion energy, and sputtering by helium ions became the major contribution when the energy was &gt
200 eV. Reduction in sputtering on nanostructured surface was observed. Arcing was initiated using laser pulses, and the erosion rate by arcing was measured. The erosion rate increased with arc current, while the erosion per Coulomb was not affected by arc current.

DOI： 10.1016/j.nme.2017.03.004

Measuring temperature effects on nano-bubble growth in tungsten with grazing incidence small angle X-ray scattering Reviewed

Matt Thompson, Russ Doerner, Noriyasu Ohno, Nigel Kirby, Patrick Kluth, Daniel Riley, Cormac Corr

Nuclear Materials and Energy Vol. 12 page： 1294 - 1297 2017.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier Ltd

W samples were exposed to He plasma in the MAGPIE, NAGDIS-II and PISCES-A across a range of sample temperatures between 473–1123 K. GISAXS was used to quantify the effect of plasma fluence and W surface temperature on He nano-bubble size distributions. In NAGDIS-II at 873 K nano-bubbles are exponentially distributed with mean diameters μ=0.64±0.01nm, similar to the value of μ=0.62±0.01nmfound for the MAGPIE plasma device at the much lower temperature of 473 K. Above ∼900 K nano-bubbles followed an approximately exponential distribution with μ &gt
0.72 nm demonstrating a significant increase in nano-bubble sizes at higher temperatures.

DOI： 10.1016/j.nme.2016.11.025

Toroidally symmetric/asymmetric effect on the divertor flux due to neon/nitrogen seeding in LHD Reviewed

A Particle-In-Cell approach to particle flux shaping with a surface mask Reviewed

Kawamura G, Ohno N, Takamura S, Tomita Y

NUCLEAR MATERIALS AND ENERGY Vol. 12 page： 297 - 301 2017.8

H. Tanaka, G. Kawamura, S. Masuzaki, M. Kobayashi, T. Akiyama, B.J. Peterson, K. Mukai, R. Sano, S.Y. Dai, R. Sakamoto, T. Morisaki, N. Ohno, LHD Experiment Group

Nucl. Mater. Energy Vol. 12 page： 241 - 246 2017.8

Molecular activated recombination in divertor simulation plasma on GAMMA 10/PDX Reviewed

Sakamoto M, Terakado A, Nojiri K, Ezumi N, Nakashima Y, Sawada K, Ichimura K, Fukumoto M, Oki K, Shimizu K, Ohno N, Masuzaki S, Togo S, Kohagura J, Yoshikawa M

NUCLEAR MATERIALS AND ENERGY Vol. 12 page： 1004 - 1009 2017.8

Fractality and growth of He bubbles in metals Reviewed

Shin Kajita, Atsushi M. Ito, Noriyasu Ohno

PHYSICS LETTERS A Vol. 381 ( 29 ) page： 2355 - 2362 2017.8

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Pinholes are formed on surfaces of metals by the exposure to helium plasmas, and they are regarded as the initial process of the growth of fuzzy nanostructures. In this study, number density of the pinholes is investigated in detail from the scanning electron microscope (SEM) micrographs of tungsten and tantalum exposed to the helium plasmas. A power law relation was identified between the number density and the size of pinholes. From the slope and the region where the power law was satisfied, the fractal dimension D and s(min), which characterize the SEM images, are deduced. Parametric dependences and material dependence of D and s(min) are revealed. To explain the fractality, simple Monte-Carlo simulations including random walks of He atoms and absorption on bubble was introduced. It is shown that the initial position of the random walk is one of the key factors to deduce the fractality. The results indicated that new nucleations of bubbles are necessary to reproduce the number-density distribution of bubbles. (C) 2017 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.physleta.2017.05.028

Field Emission From Metal Surfaces Irradiated With Helium Plasmas Reviewed International coauthorship

Dogyun Hwangbo, Shin Kajita, Noriyasu Ohno, Dmitry Sinelnikov

IEEE TRANSACTIONS ON PLASMA SCIENCE Vol. 45 ( 8 ) page： 2080 - 2086 2017.8

Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC

Field electron emission from metal (tungsten, molybdenum, and tantalum) surfaces with different surface morphology was measured. Fuzz and loop samples had small increment in the emission current, whereas bubble samples marked huge increment in the current, accompanied by breakdown. The emission current became greater on the fuzzy samples than the loop samples probably because of more elongated morphology of fuzzy fiber. Among the materials, molybdenum had the lowest current. From Fowler-Nordheim plot analysis, it was revealed that fuzz samples had higher field enhancement factor than loop samples. Bubble samples marked the highest value in the field enhancement factor among the three types of morphology, likely due to the continuous emission from the craters formed after the breakdown. Molybdenum showed favorable properties in terms of suppressing the field emission and preventing the breakdown and the arcing in fusion reactor. From the scanning electron microscope observation, the size of the crater increases with the emission current on the bubble samples. Fuzzy structure was observed at the crater on the tantalum bubble surface after breakdown even without stationary plasma irradiation or stationary incidence of ion flux.

DOI： 10.1109/TPS.2017.2679211

Effects of modified surfaces produced at plasma-facing surface on hydrogen release behavior in the LHD Reviewed

Nobuta Y, Masuzaki S, Tokitani M, Ashikawa N, Nagata D, Yoshida N, Oya Y, Yajima M, Motojima G, Kasahara H, Miyamoto M, Ohno N, Yamauchi Y

NUCLEAR MATERIALS AND ENERGY Vol. 12 page： 483 - 487 2017.8

Behavior of 23S metastable state He atoms in low-temperature recombining plasmas Reviewed

S.Kajita, T.Tsujihara, M.Aramaki, H.van der Meiden, H.Oshima, N.Ohno, H.Tanaka, R.Yasuhara, T.Akiyama, K.Fujii, T.Shikama

Physics of Plasmas Vol. 24 page： 073301(8 pp) 2017.6

Influence of expanding and contracting magnetic field configurations on detached plasma formation in a linear plasma device Reviewed

Y.Hayashi, N.Ohno, S.Kajita, H.Tanaka

Physics of Plasmas Vol. 24 page： 062509(8 pp) 2017.6

Recent progress of the JT-60SA project Reviewed International coauthorship International journal

Shirai H., Barabaschi P., Kamada Y., Maksoud W.A., Aiba N., Akiyama T., Alonso J., Angioni C., Arai T., Arakawa H., Ardellier F., Artaud J.F., Asakura N., Ashikawa N., Barbato E., Barrera G., Baruzzo M., Baulaigue O., Beaufils S., Bécoulet M., Benkadda S., Benoit F., Bettini P., Beurskens M., Bierwage A., Boboc A., Boccaccini L., Bolzonella T., Bonne F., Borba D., Botija J., Bourdelle C., Brolatti G., Bruschi A., Bucalossi J., Cabrera-Pérez S., Canton A., Cardella A., Carvalho I., Challis C., Chapman I., Chiba S., Ciazynski D., Cismondi F., Clement-Lorenzo S., Coccoluto G., Cocilovo V., Coda S., Coelho R., Coletti A., Collin B., Conway G., Corato V., Costa P., Crisanti F., Cristofani C., Cruz N., Cucchiaro A., Dairaku M., Davis S., Day C., de Baar M., de la Luna E., De Tommasi G., De Vellis A., De Vries P., Decker J., Decool P., Delrez C., Di Pace L., Di Pietro E., Disset G., Donati A., Douai D., Dougnac H., Duchateau J.L., Duglue D., Dumas N., Dunai D., Ejiri A., Endo Y., Enoeda M., Falchetto G., Farina D., Farthing J., Fejoz P., Fernandez P., Ferro A., Fiamozzi-Zignani C., Fietz W., Figini L., Frello G., Frosi P., Fujita T., Fukuda T., Fukumoto M., Fukuyama A., Furukawa M., Furukawa M.

Nuclear Fusion Vol. 57 ( 10 ) 2017.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Nuclear Fusion

The JT-60SA project has been implemented for the purpose of an early realization of fusion energy. With a powerful and versatile NBI and ECRF system, a flexible plasma-shaping capability, and various kinds of in-vessel coils to suppress MHD instabilities, JT-60SA plays an essential role in addressing the key physics and engineering issues of ITER and DEMO. It aims to achieve the long sustainment of high integrated performance plasmas under the high β N condition required in DEMO. The fabrication and installation of components and systems of JT-60SA procured by the EU and Japan are steadily progressing. The installation of toroidal field (TF) coils around the vacuum vessel started in December 2016. The commissioning of the cryogenic system and power supply system has been implemented in the Naka site, and JT-60SA will start operation in 2019. The JT-60SA research plan covers a wide area of issues in ITER and DEMO relevant operation regimes, and has been regularly updated on the basis of intensive discussion among European and Japanese researchers.

DOI： 10.1088/1741-4326/aa5d01

Increase in the energy absorption of pulsed plasma by the formation of tungsten nanostructure Reviewed

Measurement of Poloidal Flow Profiles Using a Mach Probe Array in HYBTOK-II Tokamak with RMP Fields Reviewed

Okamoto Masaaki, Sakakibara Satoru, Yoshimoto Naoya, Ohno Takuya, Ohno Noriyasu

PLASMA AND FUSION RESEARCH Vol. 12 page： 1202027 2017.6

Observations of sustained phase shifted magnetic islands from externally imposed m/n=1/1 RMP in LHD Reviewed International coauthorship

Narushima Y., Sakakibara S., Suzuki Y., Watanabe K. Y., Ohdachi S., Takemura Y., Yoshinuma M., Ida K., Castejon F., Lopez-Bruna D., Hegna C. C., Kobayashi M., Tanaka H., Akiyama T., Ohno N.

NUCLEAR FUSION Vol. 57 ( 7 ) page： 076024 2017.5

Molecular activated recombination in divertor simulation plasma on GAMMA 10/PDX Reviewed

M.Sakamoto, A.Terakado, K.Nojiri, N.Ezumi, Y.Nakashima, K.Sawada, Ichimura, M.Fukumoto, N.Ohno, S.Masuzaki, S.Togo, Kohagura, M.Yoshikawa

Nuclear Materials and Energy Vol. 12 page： 1004-1009 2017.5

D. Sato, N. Ohno, F. Domon, S. Kajita, Y. Kikuchi, I. Sakuma

Nuclear Fusion Vol. 57 ( 6 ) page： 066028(8 pp) 2017.4

Language：English Publishing type：Research paper (scientific journal)

© 2017 IAEA, Vienna. The synergistic effects of steady-state and pulsed plasma irradiation to material have been investigated in the device NAGDIS-PG (Nagoya DIvertor Simulator with Plasma Gun). The duration of the pulsed plasma was ∼0.25 ms. To investigate the pulsed plasma heat load on the materials, we developed a temperature measurement system using radiation from the sample in a high time resolution. The heat deposited in response to the transient plasma on a tungsten surface was revealed by using this system. When the nanostructures were formed by helium plasma irradiation, the temperature increase on the bulk sample was enhanced. The result suggested that the amount of absorbed energy on the surface was increased by the formation of nanostructures. The possible mechanisms causing the phenomena are discussed with the calculation of a sample temperature in response to the transient heat load.

DOI： 10.1088/1741-4326/aa67ad

Tailoring of fuzzy nanostructures on porous tungsten skeleton by helium plasma irradiation Reviewed

Shin Kajita, Hirohiko Tanaka, Noriyasu Ohno

Japanese Journal of Applied Physics Vol. 56 ( 3 ) page： 030303(4 pp) 2017.3

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Japan Society of Applied Physics

Porous tungsten skeleton, which was fabricated by sintering of tungsten powder, was exposed to helium plasmas, and the fuzzy nanostructures were tailored on the surface. The hemispherical optical reflectance of the samples was measured at the wavelength of 633 nm. It was shown that the optical reflectance of the porous tungsten skeleton was lower than that of flat tungsten samples. The minimum reflectance was &gt
0.4%, suggesting that the darkest metallic material was fabricated. The advantage of the porous tungsten skeleton with nanostructures for optical application is discussed.

DOI： 10.7567/JJAP.56.030303

Plasma detachment in linear devices Reviewed

Ohno N.

PLASMA PHYSICS AND CONTROLLED FUSION Vol. 59 ( 3 ) page： 034007(9 pp) 2017.3

Localized density fluctuation in the downstream of detached plasma Reviewed

Kohei Takeyama, Noriyasu Ohno, Masayuki Yoshikawa, Hirohiko Tanaka, Shin Kajita

Plasma and Fusion Research Vol. 12 ( 1 ) page： 1202007 2017.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Japan Society of Plasma Science and Nuclear Fusion Research

The density fluctuation was measured with a 70-GHz microwave interferometry system in the linear divertor plasma simulator NAGDIS-II while changing from the attached to the detached states. In the detached plasma, a large amplitude fluctuation of ≤ 10 kHz appeared in the peripheral region. The fluctuation has a maximum value at the neutral gas pressure of 30 - 34 mTorr. Further, the measurement of the light emission associated with the plasma recombination indicates that the large amplitude fluctuation is located at just downstream of the recombination front, in which the recombination process is the most enhanced.

DOI： 10.1585/pfr.12.1202007

Transverse motion of a plasma column in a sheet plasma Reviewed

Takuya Onda, Shin Kajita, Takaaki Iijima, Akira Tonegawa, Noriyasu Ohno, Hirohiko Tanaka

CONTRIBUTIONS TO PLASMA PHYSICS Vol. 57 ( 2 ) page： 87 - 93 2017.2

Language：English Publishing type：Research paper (scientific journal) Publisher：WILEY-V C H VERLAG GMBH

In this paper, we show the dynamic behaviors of a sheet plasma and the corresponding release of blob-like plasmas to the periphery of the sheet based on observation with a high-speed camera. We found that the plasma column moves in a transverse direction reciprocally when injecting a small amount of Ar gas to the He plasma from the plasma source region. The motion continued periodically at a frequency of similar to 5 kHz. The frequency of the plasma column motion decreased with increasing Ar gas flow rate and increasing magnetic field. The mechanism of the transverse motion is discussed. Furthermore, in response to the reciprocating motion, release of a blob-like plasma was observed. The differences in the behavior of the released plasma compared with the other linear devices are discussed.

DOI： 10.1002/ctpp.201500142

In Situ TEM Observation of Helium Bubbles Collapsing on Nanostructured Tungsten during Annealing Reviewed

M. Yajima, N. Yoshida, S. Kajita, and N. Ohno

Plasma and Fusion Research Vol. 11 page： 1206125 2016.12

Measurement of heat diffusion across fuzzy tungsten layer Reviewed

S.Kajita, T.Yagi, K.Kobayashi, M.Tokitani, N.Ohno

Results in Physics Vol. 6 page： 877-878 2016.11

Enhancement of photocatalytic activity of TiO2 by plasma irradiation Reviewed

S.Kajita, T.Yoshida, N.Ohno, T.Ishida, D.Kitaoka

Japanese Journal of Applied Physics Vol. 55 page： 106202(5 pp) 2016.9

Plasma detachment study of high density helium plasmas in the Pilot-PSI device Reviewed

Y.Hayashi, K.Jesko, H.J.van der Meiden, J.W.M.Vernimmen, T.W.Morgan, N.Ohno, S.Kajita, M.Yoshikawa, S.Masuzaki

Nuclear Fusion Vol. 56 page： 126006(13 pp) 2016.9

Fuzzy nanostructure growth on Ta/Fe by He plasma irradiation Reviewed

S.Kajita, T.Ishida, N.Ohno, D.Hwangbo, T.Yoshida

Scientific Reports Vol. 6 page： 30380 2016.7

Statistical Analysis of Particle Flux Flowing into the End-Target in between Atached and Detached Sttes in the Linear Divertor Plasma Simulator NAGDIS-II Reviewed

H.Tanaka, N.Ohno, T.Onda, K.Takeyama, S.Kajita, T.Kuwabara, Y.Tsuji

Contrib. Plasma Phys. Vol. 56 ( 6-8 ) page： 723-728 2016.6

Measurement of thermophysical property of plasma forming tungsten nanofiber layer Reviewed

S.Kajita, T.Yagi, K.Kobayashi, M.Tokitani, N.Ohno

Japanese Journal of Applied Physics Vol. 55 page： 056203(5 pp) 2016.4

Dynamics of three-dimensional radiative structures during RMP assisted detached plasmas on the large helical device and its comparison with EMC3-EIRENE modeling Reviewed International coauthorship

Shwetang N. Pandya, Byron J. Peterson, Masahiro Kobayashi, Katsumi Ida, Kiyofumi Mukai, Ryuichi Sano, Junichi Miyazawa, Hirohiko Tanaka, Suguru Masuzaki, Tsuyoshi Akiyama, Gen Motojima, Noriyasu Ohno

NUCLEAR FUSION Vol. 56 ( 4 ) page： 046002 2016.3

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

The resonant magnetic perturbation (RMP) island introduced in the stochastic edge of the large helical device (LHD) plasma plays an important role in the stabilization of the plasma detachment (Kobayashi et al 2013 Nucl. Fusion 53 093032). The plasma enters in the sustained detachment phase in the presence of an RMP once the line averaged density exceeds a critical value with a given input power. During detachment the enhanced radiation from the stochastic edge of the LHD undergoes several spatiotemporal changes which are studied quantitatively by an infrared imaging video bolometer (IRVB) diagnostic. The experimental results are compared qualitatively and quantitatively with the radiation predicted by the 3D transport simulation with fluid model, EMC3-EIRENE. A fair amount of qualitative agreement, before and after the detachment, is reported. The issue of overestimated radiation from the model is addressed by changing the free parameters in the EMC3-EIRENE code till the total radiation and the radiation profiles match closely, within a factor of two with the experimental observations. A better quantitative match between the model and the experiment is achieved at higher cross-field impurity diffusion coefficient and lower sputtering coefficient after the detachment. In this article a comparison, the first of its kind, is established between the quantified radiation from the experiments and the synthetic image obtained from the simulation code. This exercise is aimed towards validating the model assumptions against the experimentally measured radiation.

DOI： 10.1088/0029-5515/56/4/046002

Strong Reduction of Ion Flux to a Target Plate in a Magnetically Contracting Detached Plasma Reviewed

Y.Hayashi, H.Nishikata, N.Ohno, S.Kajita

Plasma and Fusion Research: Rapid Communications Vol. 11 page： 1202005(2 pp) 2016.2

Plasma flow in peripheral region of detached plasma in linear plasma device Reviewed

Y.Hayashi, N.Ohno, S.Kajita, H.Tanaka

Physics of Plasmas Vol. 23 page： 012511(7 pp) 2016.1

Arc tracks on nanostructured surfaces after microbreakdowns Reviewed

D.Sinelnikov, D.Bulgadaryan, D.Hwangbo, S.Kajita, D.Kolodko, V.Kurnaev, N.Ohno

Journal of Physics:Conference Series Vol. 748 page： 012012(6 pp) 2016

Detailed Analysis of Plasma Resistivity in Detached Recombining Plasmas Reviewed

H.Nishikata, Y.Hayashi, N.Ohno, S.Kajita, T.Kuwabara

Contrib. Plasma Phys. Vol. 56 ( 6-8 ) page： 717-722 2016

Modeling of Linear Divertor Plasma Simulator Experiments with Three-dimensional Target Structure by Using EMC3-EIRENE Code Reviewed

T.Kubawara, H.Tanaka, G.Kawamura, N.Ohno, H.Nishikata, M.Kobayashi, Y.Feng

Contrib. Plasma Phys. Vol. 56 ( 6-8 ) page： 598-603 2016

Effects of Modified Surfaces Produced at Plasma-Facing Surface on Hydrogen Isotopes and Helium Release Behavior in the LHD Reviewed

Y.Nobuta, S.Masuzaki, M.Tokitani, D.Nagata, N.Ashikawa, N.Yoshida, Y.Oya, M.Yajima, G.Motojima, H.Kasahara, M.Miyamoto, N.Ohno

IAEA proccedings page： MPT/P5-19(9 pp) 2016

Photon Trapping Effects in DEMO Divertor Plasma Reviewed

K. Hoshino, K. Sawada, R. Idei, S. Tokunaga, N. Asakura, K. Shimizu, and N. Ohno

Contrib. Plasma Phys. Vol. 56 page： 657-662 2016

Investigation of arcing on fiber-formed nanostructured tungsten by pulsed plasma during steady state plasma irradiation Reviewed

M. Yajima, N. Ohno, S. Kajita, G. De Temmerman, K. Bystrov, S. Bardin

Fusion Engineering and Design Vol. 112 page： 156-161 2016

Vacuum Breakdown from Nanostructured Fuzzy Surfaces Reviewed International coauthorship International journal

Sinelnikov D., Bulgadaryan D., Hwangbo D., Kajita S., Kolodko D., Kurnaev V., Ohno N.

PROCEEDINGS OF THE 27TH INTERNATIONAL SYMPOSIUM ON DISCHARGES AND ELECTRICAL INSULATION IN VACUUM (ISDEIV), VOL 1 page： 68 - 71 2016

Morphology and optical property changes of nanostructured tungsten in LHD Reviewed

S.Kajita, T.Akiyama, N.Yoshida, M.Tokitani, M.Yajima, N.Ohno

Plasma and Fusion Research Vol. 10 page： 1402083(9 pp) 2015.12

Sulfur K-edge XANES for methylene blue in photocatalytic reaction over WO<inf>3</inf> nanomaterials Reviewed International journal

K. Komori, T. Yoshida, T. Nomoto, M. Yamamoto, C. Tsukada, S. Yagi, M. Yajima, S. Kajita, N. Ohno

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms Vol. 365 page： 35 - 38 2015.12

Increase in the work function of W/WO3 by helium plasma irradiation Reviewed

S.Kajita, A.Ohta, T.Ishida, K.Makihara, T.Yoshida, N.Ohno

Japanese Journal of Applied Physics Vol. 54 page： 126201(6 pp) 2015.11

3D effects of edge magnetic field configuration on divertor/scrape-off layer transport and optimization possibilities for a future reactor Reviewed International coauthorship International journal

M. Kobayashi, Y. Xu, K. Ida, Y. Corre, Y. Feng, O. Schmitz, H. Frerichs, F. L. Tabares, T. E. Evans, J. W. Coenen, Y. Liang, A. Bader, K. Itoh, H. Yamada, Ph Ghendrih, G. Ciraolo, D. Tafalla, A. Lopez-Fraguas, H. Y. Guo, Z. Y. Cui, D. Reiter, N. Asakura, U. Wenzel, S. Morita, N. Ohno, B. J. Peterson, S. Masuzaki

Nuclear Fusion Vol. 55 ( 10 ) page： 104021 2015.9

Language：English

© 2015 IAEA, Vienna. This paper assesses the three-dimensional (3D) effects of the edge magnetic field structure on divertor/scrape-off layer transport, based on an inter-machine comparison of experimental data and on the recent progress of 3D edge transport simulation. The 3D effects are elucidated as a consequence of competition between transports parallel () and perpendicular () to the magnetic field, in open field lines cut by divertor plates, or in magnetic islands. The competition has strong impacts on divertor functions, such as determination of the divertor density regime, impurity screening and detachment control. The effects of magnetic perturbation on the edge electric field and turbulent transport are also discussed. Parameterization to measure the 3D effects on the edge transport is attempted for the individual divertor functions. Based on the suggested key parameters, an operation domain of the 3D divertor configuration is discussed for future devices.

DOI： 10.1088/0029-5515/55/10/104021

Initiation of arcing on tungsten surface exposed to steady state He Plasmas Reviewed

S.Kajita, Y.Noiri, N.Ohno

Physica Scripta Vol. 90 ( 9 ) page： 095604(7 pp) 2015.8

Development of Impurity Seeding and Radiation Enhancement in the Helical Divertor of LHD Reviewed

K.Mukai, S.Masuzaki, B.Peterson, T.Akiyama, M.Kobayashi, H.Tanaka, S.Pandya, R.Sano, G.Motojima, N.Ohno, T.Morisaki, C.Suzuki, I.Murakami, J.Miyazawa, N.Tamura, S.Yoshimura, I.Yamada, R.Yasuhara, H.Funaba, K.Tanaka

Nuclear Fusion Vol. 55 page： 83016(9 pp) 2015.7

Overview of transport and MHD stability study:focusing on the impact of magnetic field topology in the Large Helical Device Reviewed

K. Ida, K. Nagaoka, S. Inagaki, H. Kasahara, T. Evans, M. Yoshinuma, K. Kamiya, S. Ohdach, M. Osakabe, M. Kobayashi, S. Sudo1,, K. Itoh, T. Akiyama, M. Emoto, A. Dinklage, X. Du, K. Fujii, M. Goto, T. Goto, M. Hasuo, C. Hidalgo, K. Ichiguchi, A. Ishizawa, M. Jakubowski, G. Kawamura, D. Kato, S. Morita, K. Mukai, I. Murakami, S. Murakami, Y. Narushima, M. Nunami, N. Ohno, N. Pablant, S. Sakakibara, T. Seki, T. Shimozuma, M. Shoji, K. Tanaka, T. Tokuzawa, Y. Todo, H. Wang, M. Yokoyama, H. Yamada, Y. Takeiri, T. Mutoh, S. Imagawa, T. Mito, Y. Nagayama, K.Y. Watanabe, N. Ashikawa, H. Chikaraishi, A. Ejiri, M. Furukawa, T. Fujita, S. Hamaguchi, H. Igami1, M. Isobe, S. Masuzaki, T. Morisaki, G. Motojima, K. Nagasaki, H. Nakano, Y. Oya, C. Suzuki, Y. Suzuki, R. Sakamoto, M. Sakamoto, A. Sanpei, H. Takahashi, H. Tsuchiya, M. Tokitani, Y. Ueda, Y. Yoshimura1, S. Yamamoto, K. Nishimura, H. Sugama, T. Yamamoto, H. Idei, A. Isayama, S. Kitajima, S. Masamune, K. Shinohara, P.S. Bawankar, E. Bernard, M. von Berke, H. Funaba, X.L. Huang, T. Ii, T. Ido, K. Ikeda, S. Kamio, R. Kumazawa, T. Kobayashi, C. Moon, S. Muto, J. Miyazawa, T. Ming, Y. Nakamura, S. Nishimura, K. Ogawa, T. Ozaki, T. Oishi, M. Ohno, S. Pandya, A. Shimizu, R. Seki, R. Sano, K. Saito, H. Sakaue, Y. Takemura, K. Tsumori, N. Tamura, H. Tanaka, K. Toi, B. Wieland, I. Yamada, R. Yasuhara, H. Zhang2, O. Kaneko, A. Komori and Collaborators

Nuclear Fusion Vol. 55 ( 10 ) page： 104018 2015.7

Sulfur E-edge XANES for methylene blue in photocatalytic reaction over WO3 nanomaterials Reviewed

K.Komori, T.Yoshida, T.Nomoto, M.Yamamoto, C.Tsukada, S.Yagi, M.Yajima, S.Kajita, N.Ohno

Nuclear Instruments and Methods in Physics Research B Vol. 365 page： 35-38 2015.7

Molecular dynamics and Monte Carlo hybrid simulation for fuzzy tungsten nanostructure formation Reviewed

A.M.Ito, A.Takayama, Y.Oda, T.Tamura, R.Kobayashi, T.Hattori, S.Ogata, N.Ohno, S.Kajita, M.Yajima, Y.Noiri, Y.Yoshimoto, S.Saito, S.Takamura, T.Murashima, M.Miyamoto, H.Nakamura

Nuclear Fusion Vol. 55 ( 7 ) page： 073013 2015.6

Growth of multifractal tungsten nanostructure by He bubble induced directional swelling Reviewed

S.Kajita, N.Yoshida, N.Ohno, Y.Tsuji

New Journal of Physics Vol. 17 page： 043038(14 pp) 2015.4

Influence of Deuterium Retention on Secondary Electron Emission from Graphite under Deuterium Plasma Exposure Reviewed

T.Kaneko, N.Ohno, Y.Nakamura, M.Yamagiwa, N.Matsunami, S.Kajita, M.Takagi

Plasma and Fusion Research: Regular Articles Vol. 10 page： 1402009(5 pp) 2015.3

Nanostructure growth by helium plasma irradiation to tungsten in sputtering regime Reviewed

Y.Noiri, S.Kajita, N.Ohno

Journal of Nuclear Materials Vol. 463 ( C ) page： 285 - 288 2015.1

Flow damping due to stochastization of the magnetic field Reviewed

K.Ida, M.Yoshinuma, H.Tsuchiya, T.Kobayashi, C.Suzuki, M.Yokoyama, A.Shimizu, K.Nagaoka, S.Inagaki, K.Itoh & the LHD Experiment Group (36th author)

Nature Communications 2015.1

Hybrid simulation research on formation mechanism of tungsten nanostructure induced by helium plasma irradiation Reviewed

A.M. Ito, A.Takayama, Y.Oda, T.Tamura, R.Kobayashi, T.Hattori, S.Ogata, N.Ohno, S.Kajita, M.Yajima, Y.Noiri, Y.Yoshimoto, S.Saito, S.Takamura, T.Murashima, M.Miyamoto, H.Nakamura

Journal of Nuclear Materials Vol. 463 page： 109 - 115 2015.1

Multi-pin Langmuir probe measurement for identification of blob propagation characteristics in the Large Helical Device Reviewed

H.Tanaka, S.Masuzaki, N.Ohno, T.Morisaki, Y.Tsuji, LHD Experiment Group

Journal of Nuclear Materials Vol. 463 page： 761-764 2015

Evolution of radiation profiles during detached plasmas and radiative collapse in LHD Reviewed

S.N.Pandya, B.J.Peterson, M.Kobayashi, K.Mukai, R.Sano, H.Tanaka, S.Masuzaki, J.Miyazawa, T.Akiyama.G.Motojima N.Ohno

Journal of Nuclear Materials Vol. 463 page： 551-554 2015

Nanostructure growth by helium plasma irrdaition to tungsten in sputtering regime Reviewed

Y.Noiri, S.Kajita, N.Ohno

Journal of Nuclear Materials Vol. 463 page： 285-288 2015

Progress of divertor simulation research toward the realization of detached palsam using a large tandem mirror device Reviewed

Y.Nakashima, H.Takeda, K.Ichimura, K.Hosoi, K.Oki, M.Sakamoto, M.Hirata, M.Ichimura, R.Ikezoe, T.Imai, M.Iwamoto, Y.Hosoda, I.Katanuma, T.Kariya, S.Kigure, J.Kohagura, R.Minami, T.Numakura, S.Takahashi, M.Yoshikawa, N.Asakura, M.Fukumoto, A.Hatayama, Y.Hirooka, S.Kado, H.Kubo, S.Masuzaki, H.Matsuura, S.Nagata, N.Nishino, N.Ohno, A.Sagara, T.Shikama, M.Shoji, A.Tonegawa, Y.Ueda

Journal of Nuclear Materials Vol. 463 page： 537-540 2015

Impact of 3D magnetic field structure on boundary and divertor plasmas in stellarator /heliotron devices Reviewed

M.Kobayasahi, Y.Feng, Y.Xu, F.L.Tabares, K.Ida, O.Schmitz, T.E.Evans, H.Frerichs, Y.Liang, A.bader, K.Itoh, H.Yamada, Ph.Ghendrih, G.Ciraolo, D.Tafalla, A.Lopez-Fraguas, H.Y.Guo, Z.Y.Cui, D.Reiter, N.Asakura, U.Wenzel, S.Morita, N.Ohno, B.J.Peterson, S.Masuzaki

Journal of Nuclear Materials Vol. 463 page： 2-10 2015

Global helium particle balance in LHD Reviewed

G.Motojima, S.Masuzaki, M.Tokitani, H.Kasahara, Y.Yoshimura, M.Kobayashi, R.Sakamoto, T.Morisaki, J.Miyazawa, T.Akiyama, N.Ohno, T.Mutoh, H.Yamada, LHD Experiment Group

Journal of Nuclear Materials Vol. 463 page： 1080-1083 2015

Radiated power distributions in impurity-seeded plasmas in LHD Reviewed

T.Morisaki, K.Oyama, N.Tamura, S.Masuzaki, T.Akiyama, G.Motojima, J.Miyazawa, B.J.Peterson, N.Ohno, H.Yamada, LHD Experiment Group

Journal of Nuclear Materials Vol. 463 page： 640-643 2015

Simulation Study of Power Load with Impurity Seeding in Advanced Divertor "Short Super-X Divertor" for a Tokamak Reactor Reviewed

N.Asakura, K.Hoshino, K.Shimizu, K.Shinya, H.Utoh, S.Tokunaga, K.Tobita, N.Ohno

Journal of Nuclear Materials Vol. 463 page： 1238-1242 2015

Influence of external resonant magnetic perturbation field on edge plasma of small tokamak HYBTOK-II Reviewed

Y.Hayashi, Y.Suzuki, N.Ohno, M.Okamoto, Y.Kikuchi, S.Sakakibara, K.Watanabe, Y.Takemura

Journal of Nuclear Materials Vol. 463 page： 463-466 2015

In-situ measurement of deuterium retention in W under plasma exposure Reviewed

T. Watanabe, T. Kaneko, N. Matsunami, N. Ohno, S. Kajita, T. Kuwabara

Journal of Nuclear Materials Vol. 463 page： 1049-1052 2015

CORRELATION ANALYSIS OF 3-4 KILOHERTZ CORE AND EDGE DENSITY FLUCTUATIONS IN THE GAMMA 10 TANDEM MIRROR DEVICE Reviewed

H. Tanaka, M. Sakamoto, K. Furutachi, K. Oki, M. Mizuguchi, Y. Nagatsuka, M. Yoshikawa, R. Nohara, M. Yoshikawa, J. Kohagura, N. Ohno, and Y. Tsuji

Fusion Sci. Tech. Vol. 68 page： 125-129 2015

Influence of Deuterium Retention on Secondary Electron Emission from Graphite under Deuterium Plasma Exposure Reviewed

T.Kaneko, N.Ohno, Y.Nakamura, M.Yamagiwa, N.Matsunami, S.Kajita, M.Takagi

Plasma and Fusion Research Vol. 10 page： 1402009(5 pp) 2015

Arc spot grouping: An entanglement of arc spot cells Reviewed

S.Kajita, D.Hwangbo, N.Ohno, M.M.Tsventoukh, S.A.Barengolts

Journal of Applied Physics Vol. 116 page： 233302 2014.12

Current Activities in the Interactive Joint Research at Tohoku University - Advanced Evaluation of Radiation Effects on Fusion Materials - Reviewed

H.Kurishita, M.Hatakeyama, M.Narui, S.Matsuo, T.Shikama, K.Tada, N.Ohno, T.Takeuchi, Y.Hatano, M.Nishiura, Y.Nakashima, H.Watanabe, K.Tokunaga, T.Hino, Y.Ueda, T.Muroga, A.Sagara, O.Kaneko

Plasma and Fusion Research Vol. 9 page： 3405136（4 pp) 2014.9

Compact and high-particle-flux thermal-lithium-beam probe system for measurement of two-dimensional electron density profile Reviewed

Y.Shibata, T.Manabe, S.Kajita, N.Ohno, M.Takagi, H.Tsuchiya, T.Morisaki

Rev. Sci. Instrum. Vol. 85 page： 93510(6 pp) 2014.9

Application of Nanostructured Tungsten Fabricated by Helium Plasma Irradiation for Photoinduced Decolorization of Methylene Blue Reviewed

K.Komori, T.Yoshida, S.Yagi, H.Yoshida, M.Yajima, S.Kajita, N.Ohno

e-J.Surf.Sci.Nanotech.(e-Journal of Surface Science and Nanotechnology) Vol. 12 page： 343-348 2014.7

Fractality of self-grown nanostructured tungsten by He plasma irradiation Reviewed

S.Kajita, Y.Tsuji, N.Ohno

Physics Letters A Vol. 378 page： 2533-2538 2014.7

In situ observation of structural change of nanostructured tungsten during annealing Reviewed

M.Yajima, N.Yoshida, S.Kajita, M.Tokitani, T.Baba, N.Ohno

Journal of Nuclear Materials Vol. 449 ( 1-3 ) page： 9-14 2014.6

Influence of plasma-neutral collisions on probe measurements in atmospheric pressure plasmas Reviewed International journal

Contributions to Plasma Physics Vol. 54 ( 3 ) page： 304 - 307 2014.4

In situ measurement of deuterium retention in graphite under successive exposure to deuterium and hydrogen plasmas Reviewed

N.Ohno, Y.Nakamura, M.Yamagiwa, T.Kaneko, N.Matsunami, S.Kajita, M.Takagi

Phys. Scr. Vol. T159 page： 014053(4 pp) 2014.4

A plasma source driven predator-prey like mechanism as a potential cause of spiraling intermittencies in linear plasma devices Reviewed

D.Reiser, N.Ohno, H.Tanaka, L.Vela

Physics of Plasmas Vol. 21 page： 032302(10 pp) 2014.3

Surface modification of titanium using He plasma Reviewed

S.Kajita, D.Kitaoka, N.Ohno, R.Yoshihara, N.Yoshida, T.Yoshida

Applied Surface Science Vol. 303 page： 438-445 2014.3

Thermal response of nanostructured tungsten Reviewed

S.Kajita, G.De Temmerman, T.Morgan, S.van Eden, T. de Kruif, N.Ohno

Nuclear Fusion Vol. 54 page： 033005(10 pp) 2014.2

Helium plasma irradiation on single crystal tungsten and undersized atom doped tungsten alloys Reviewed International journal

Shin Kajita, Naoaki Yoshida, Noriyasu Ohno, Yuki Hirahata, Reiko Yoshihara

PHYSICA SCRIPTA Vol. 89 ( 2 ) 2014.2

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

Helium plasma irradiation leads to the formation of nanostructures on the surface when certain conditions are satisfied. The surface morphology changes due to helium plasma irradiation were investigated on single crystal tungsten samples with different crystal orientations. Differences in surface morphology changes were observed in (100) and (110) single crystal tungsten samples when the helium fluence was less than 10(25) m(-2). However, the differences disappeared as growth proceeded. Tungsten alloys were prepared in order to investigate the influence of the additional undersized atomic species on nanostructure growth. The influence of the doping of undersized atoms, i.e. 2 at% Fe doped and 2 at% Cr doped atoms, is presented.

DOI： 10.1088/0031-8949/89/02/025602

Transition in velocity and grouping of arc spot on different nanostructured tungsten electrodes Reviewed

Optical design for divertor Thomson scattering system for JT-60SA Reviewed

S.Kajita, A.Enokuchi, T.Hatae, K.Itami, T.Hamano, S.Kado, N.Ohno, N.Takeyama

Fusion Engineering and Design Vol. 89 ( 1 ) page： 69-76 2014.1

Helium plasma irradiation on single crystal tungsten and undersized atom doped tunsten alloys Reviewed

S.Kajita, N.Yoshida, N.Ohno, Y.Hirahata, R.Yoshihara

Phys. Scr. Vol. 89 page： 025602(7 pp) 2014.1

Modified Power Transmission Factor of Tungsten in Plasmas with Hot Electron Component Reviewed

S.Takamura, S.Ono, N.Ohno

Contrib. Plasma Phys. Vol. 54 ( 4-6 ) page： 474-478 2014

Dogyun Hwangbo, Shin Kajita, Sergey A. Barengolts, Mikhail M. Tsventoukh, Noriyasu Ohno

RESULTS IN PHYSICS Vol. 4 page： 33 - 39 2014

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Behavior of arc spots was investigated in detail using a nanostructured tungsten specimen with different thicknesses of the nanostructured layer. From the observation using a fast framing camera, it was found that the velocity of the arc spots significantly altered as passing the boundary of the two layers. The changes in spot velocity and spot width were discussed theoretically using the ecton model. The fractal dimension of the arc trail evaluated by using a box-counting method was significantly changed. Also, the width of arc trail was increased with the nanostructured layer thickness. From the SEM analysis of the specimen, the amount of tungsten eroded by arcing for two different thickness cases was estimated, and the erosion rates were discussed. (C) 2014 The Authors. Published by Elsevier B.V.

DOI： 10.1016/j.rinp.2014.03.001

Field emission property of nanostructured tungsten formed by helium plasma irradiation Reviewed

Spectroscopic Study and Motion Analysis of Arc Spot Initiated on Nanostructured Tungsten Reviewed

D.Hwangbo, S.Kajita, M.Osaka, N.Ohno

Jpn. J. Appl. Phys. Vol. 52 page： 11NC02(6 pp) 2013.11

Low-energy helium irradiation on in-vessel mirror materials Reviewed

S.Kajita, M.Tokitani, T.Saeki, N.Ohno, N.Yoshida

Journal of Nuclear Materials Vol. 442 ( 1-3, Supplement 1 ) page： S515-S519 2013.11

Helium effects on tungsten surface morphology and deuterium retention Reviewed

Y.Ueda, H.Y.Peng, H.T.Lee, N.Ohno, S.Kajita, N.Yoshida, R.Doerner, G.De Temmerman, V.Alimov, G.Wright

Journal of Nuclear Materials Vol. 442 ( 1-3 ) page： S267-S272 2013.11

Properties of deposited layer formed by interaction with Be seede D-He mixture plasma and tungsten Reviewed

K.Tokunaga, M.J.Baldwin, D.Nishijima, R.P.Doerner, S.Nagata, B.Tsuchiya, H.Kurishita, T.Fujiwara, K.Araki, Y.Miyamoto, N.Ohno, Y.Ueda

Journal of Nuclear Materials Vol. 442 ( 1-3 ) page： S313-S319 2013.11

Characterization of Gun Plasma Penetrated into a Steady State Plasma Device Reviewed

S.Kajita, T.Akiyama, T.Nihashi, M.Osaka, N. Ohno, Y.Kikuchi, I.Sakuma, M.Nagata

IEEE TRANSACTIONS ON PLASMA SCIENCE Vol. 41 ( 11 ) page： 3122-3128 2013.11

Shin Kajita, Noriyasu Ohno, Yuki Hirahata, Mineo Hiramatsu

FUSION ENGINEERING AND DESIGN Vol. 88 ( 11 ) page： 2842 - 2847 2013.11

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA

Field emission property of nanostructured tungsten formed by the exposure to a helium plasma is measured to investigate the initiation process of arcing in nuclear fusion devices. Field emission current from the nanostructured tungsten and tungsten with helium bubbles was significantly higher than that from the polished tungsten specimen. However, field enhancement factor was on the order of 100, which was almost comparable to that of bulk tungsten; the increase in the field emission current is attributed to primarily an increase in the effective emission surface area. From the calculation of thermo-field emission current from a heated tungsten, it is thought that a significant current emission can be still initiated even when the field enhancement factor is not so high when tungsten is exposed to high density plasmas such as the one accompanied with ELMs. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.fusengdes.2013.05.014

Progress of the JT-60SA project Reviewed International coauthorship International journal

Kamada Y., Barabaschi P., Ishida S., Abdel Maksoud W., Aiba N., Akino N., Akiyama T., Alonso J., Angioni C., Arai T., Arakawa H., Ardellier F., Artaud J., Asakawa S., Asakura N., Ashikawa N., Balaguer D., Barbato E., Barrera G., Baruzzo M., Baulaigue O., Bayetti P., Bécoulet M., Benkadda S., Benoit F., Besi U., Beurskens M., Boccaccini L., Bolzonella T., Borba D., Botija J., Bourdelle C., Brolatti G., Bruschi A., Bucalossi J., Cara P., Challis C., Chantant M., Chapman I., Chesny P., Chiba S., Ciayznski D., Cismondi F., Cocilovo V., Coletti R., Coletti A., Collins B., Conway G., Corato V., Costa P., Cucchiaro A., Dael A., Davis S., Day C., De Baar M., Decool P., Della Corte A., Delrez C., De Vries P., Decker J., Di Zenobio A., Di Pace L., Di Pietro E., Disset G., Donati A., Douai D., Dougnac H., Drotziger S., Duchateau J.L., Duglue D., Dumas N., Ejiri A., Endo Y., Farina D., Fernandez P., Ferro A., Fietz W., Figini L., Fslchetto G., Fujita T., Fukuda T., Fukumoto M., Fukuyama A., Furukawa M., Furukawa M., Gaio E., Garcia J., Garzotti L., Gauthier E., Genini L., Geraud A., Ginoulhiac G., Giruzzi G., Gomez Carrasco B., Gonde R., Goniche M., Gouat P., Gros G., Haga S.

Nuclear Fusion Vol. 53 ( 10 ) 2013.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Nuclear Fusion

The JT-60SA project implemented by Japan and Europe is progressing on schedule towards the first plasma in March 2019. After careful R&D, procurements of the major components have entered their manufacturing stages. In parallel, disassembly of JT-60U has been completed on time, and the JT-60SA tokamak assembly is expected to start in January 2013. The JT-60SA device, a highly shaped large superconducting tokamak with a variety of plasma control actuators, has been designed in order to contribute to ITER and to complement ITER in all the major areas of fusion plasma development necessary to decide DEMO reactor construction. Detailed assessments and prediction studies of the JT-60SA plasma regimes have confirmed these capabilities: using ITER- and DEMO-relevant plasma regimes, heating conditions, and its sufficiently long discharge duration, JT-60SA enables studies on magnetohydrodynamic stability at high beta, heat/particle/momentum transport, high-energy ion physics, pedestal physics including edge localized mode control, and divertor physics. By integrating these studies, the project provides 'simultaneous and steady-state sustainment of the key performance characteristics required for DEMO' with integrated control scenario development.

DOI： 10.1088/0029-5515/53/10/104010

Control of 3D edge radiation structure with resonant magnetic perturbation fields applied to the stochastic layer and stabilization of radiative divertor plasma in LHD Reviewed

M. Kobayashi, S. Masuzaki, I. Yamada, Y. Narushima, C. Suzuki, N. Tamura, B. J. Peterson, S. Morita, C. F. Dong, N. Ohno, S. Yoshimura, Y. Feng, M. Goto, K. Sato, T. Akiyama, K. Tanaka

Nuclear Fusion Vol. 53 ( 9 ) 2013.9

Language：English Publishing type：Research paper (scientific journal)

It is found that resonant magnetic perturbation (RMP) fields have a stabilizing effect on the radiating edge plasma, realizing stable sustainment of radiative divertor (RD) operation in the Large Helical Device (LHD). Without RMP, thermal instability leads to radiative collapse. Divertor power load is reduced by a factor of 3-10 during the RMP-assisted RD phase, while maintaining relatively good core plasma confinement with confinement enhancement factor . It has also been demonstrated that the RMP field itself can initiate transition to RD operation by increasing perturbation strength, while keeping constant density and injection power. The results show a possibility of a new control knob for divertor power load in a 3D magnetic field configuration. It is also found that after the transition to RD, the energy confinement enhancement factor based on ISS04 scaling increases by a factor of 1.4 compared with the attached phase. The operation range of the RMP-assisted RD is identified in terms of RMP strength and radial location of the resonance layer of the RMP. A 3D edge radiation structure is analysed using the edge transport code EMC3-EIRENE and the results are compared with experiments. The comparison indicates that the application of RMP modulates the 3D edge radiation structure such that an intense radiation appears around the X-point of the m/n = 1/1 island in the case with RMP, while it is located at the inboard side without RMP. © 2013 IAEA, Vienna.

DOI： 10.1088/0029-5515/53/9/093032

Growth Annealing Equilibrium of Tungsten Nanostructures by Helium Plasma Irradiation in Non Eroding Regimes Reviewed

S.Kajita, N.Ohno, M.Yajima, J.Kato

Journal of Nuclear Materials Vol. 440 ( 1-3 ) page： 55-62 2013.9

Influence of crystal orientation on damages of tungsten exposed to helium plasma Reviewed

N.Ohno, Y.Hirahata, M.Yamagiwa, S.Kajita, M.Takagi, N.Yoshida, R.Yoshihara, T.Tokunaga, M.Tokitani

Journal of Nuclear Materials Vol. 438 page： S879-S882 2013.7

Study of Hydrogen Isotopes Behavior in Carbon Based Materials with In-Situ Ion Beam Analysis under Plasma Exposure Reviewed

Y.Nakamura, M.Yamagiwa, T.Kaneko, N.Matsunami, N.Ohno, S.Kajita, M.Takagi, M.Tokitani, S.Masuzaki

Journal of Nuclear Materials Vol. 438 page： S1036-S1039 2013.7

Tritium retention in nanostructured tungsten with large effective surface area Reviewed

M.Yajima, Y.Hatano, S.Kajita, J.Shi, M.Hara, N.Ohno

Journal of Nuclear Materials Vol. 438 page： S1142-S1145 2013.7

Development of steady/transient dual plasma irradiation device using a plasma gun Reviewed

S.Kajita, N.Ohno, T.Akiyama, T.Nihashi, T.Uchiyama, M.Osaka, Y.Kikuchi, M.Nagata

Journal of Nuclear Materials Vol. 438 page： S707-S710 2013.7

Enhancement of multi-pulse laser induced damage threshold on Cu mirror under vacuum condition Reviewed

S.Kajita, R.Yasuhara, M.Sato, N.Ohno, M.Tokitani, N.Yoshida

Optics Express Vol. 21 ( 14 ) page： 17275-17284 2013.7

Divertor heat and particle control experiments on the large helical device Reviewed

S. Masuzaki, M.Kobayashi, T.Akiyama, N.Ohno, T.Morisaki, et al.

Journal of Nuclear Materials Vol. 438 page： S133-S138 2013.7

Edge and divertor plasma measurements with ion sensitive and Mach probes in LHD Reviewed

Y.Hayashi, N.Ezumi, S.Masuzaki, H.Tanaka, M.Kobayashi, K.Sawada, N.Ohno, the LHD Experiment Group

Journal of Nuclear Materials Vol. 438 page： S1228-S1231 2013.7

Tritium retention in nanostructured tungsten with large effective surface area Reviewed

M.Yajima, Y.Hatano, S.Kajita, J.Shi, M.Hara, N.Ohno

Journal of Nuclear Materials Vol. 438 page： S1142-S1145 2013.7

Study of hydrogen isotopes behavior in carbon based materials with in situ ion beam analysis under plasma exposure Reviewed

Y. Nakamura, M. Yamagiwa, T. Kaneko, N. Matsunami, N. Ohno, S. Kajita, M. Takagi, M. Tokitani, S. Masuzaki

Journal of Nuclear Materials Vol. 438 page： S1036-S1039 2013.7

Influence of crystal orientation on damages of tungsten exposed to helium plasma Reviewed

N.Ohno, Y.Hirahata, M.Yamagiwa, S.Kajita, M.Takagi, N.Yoshida, R.Yoshihara, T.Tokunaga, M.Tokitani

Journal of Nuclear Materials Vol. 438 page： S879-S882 2013.7

Thermal radiation characteristics and direc evidence of tungsten cooling on the way to nanostructure formation on its surface Reviewed

S.Takamura, T.Miyamoto, N.Ohno

Journal of Nuclear Materials Vol. 438 page： S814-S817 2013.7

Recent results of divertor simulation research using an end-cell of a large tandem mirror device Reviewed

Y. Nakashima, H. Takeda, K. Ichimura, K. Hosoi, M. Sakamoto, M. Hirata, M. Ichimura, R. Ikezoe, T. Imai, T. Ishii, T. Kariya, I. Katanuma, J. Kohagura, R. Minami, T. Numakura, H. Ueda, M. Yoshikawa, N. Asakura, T. Furuta, A. Hatayama, et al.(N.Ohno No.27)

Journal of Nuclear Materials Vol. 438 page： S738-S741 2013.7

Kinetic effect of high energy ions on the temperature profile in the boundary plasma region Reviewed

N.Ezumi, Y.Hayashi, K.Todoroki, K.Okazaki, H.Tanaka, S.Masuzaki, N.Ohno

Journal of Nuclear Materials Vol. 438 page： S472-S474 2013.7

Properties of deposited layer formed by interaction with Be seeded D-He mixture plasma and tungsten Reviewed International coauthorship International journal

Tokunaga K., Baldwin M.J., Nishijima D., Doerner R.P., Nagata S., Tsuchiya B., Kurishita H., Fujiwara T., Araki K., Miyamoto Y., Ohno N., Ueda Y.

Journal of Nuclear Materials Vol. 442 ( 1-3 SUPPL.1 ) 2013.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Nuclear Materials

Be-seeded, high-flux, deuterium/helium mixture plasma exposure experiments on tungsten target materials have been performed to simulate ITER all tungsten divertor erosion/modification and deposition phenomena. The exposure conditions are kept fixed at a typical low-ion-energy of 60 eV and a flux of 3-6 × 1022/m2/s. Sample temperature is 1123 K and plasma exposure times spanning 1050-10,100 s are explored. The typical ratio of He/D ions is 0.2 and Be content is 0.2%. A He-induced nanostructure layer is formed on the exposure surfaces of tungsten materials and the surface of the nanostructure is covered by a thin layer of Be and O. A fraction of the re-eroded Be from the target is deposited on a glassy carbon plate with line of sight to the tungsten target. Rutherford backscattering spectrometry analyses show that the Be redeposit layer is in the form of laminae. Small amounts of Mo, W and C are also found in the redeposited Be layer. Elastic recoil detection analyses show that D, He and H are also included in the redeposited Be layer. © 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2013.05.006

Field Emission Property of Nanostuructured Tungsten Formed by Helium Plasma Irradiation Reviewed

S.Kajita, N.Ohno, Y.Hirahata, M.Hiramatsu

Journal of Fusion Engineering and Design Vol. 88 page： 2842-2847 2013.6

Investigation of Advanced Divertor Magnetic Configuration for Demo Tokamak Reactor Reviewed

N.Asakura, K.Shinya, K.Tobita, K.Hoshino, K.Shimizu, H.Utoh, Y.Someya, M.Nakamura, N.Ohno, M.Kobayashi, H.Tanaka

Transactions of Fusion Science and Technology Vol. 63 ( 1T ) page： 70-75 2013.5

Power Transmission Factor for Tungsten Target W/WO Fiber-form Nanostructure in He Plasmas with Hot Electron Component using Compact Plasma Device AIT-PID Reviewed

S.Takamura, T.Miyamoto, N.Ohno

Transactions of Fusion Science and Technology Vol. 63 page： 225-228 2013.5

Impact of arcing on carbon and tungsten: from the observations in JT-60U, LHD and NAGDIS-II Reviewed

S.Kajita, M.Fukumoto, M.Tokitani, T.Nakano, Y.Noiri, N.Ohno, S.Masuzaki, S.Takamura, N.Yoshida, Y.Ueda

Nuclear Fusion Vol. 53 page： 053013(9 pp) 2013.4

Helium plasma implantation on metals: Nanostructure formation and visible-light photocatalytic response Reviewed

S.Kajita, T.Yoshida, D.Kitaoka, R.Etoh, M.Yajima, N.Ohno, H.Yoshida, N.Yoshida, Y.Terao

Journal of Applied Physics Vol. 113 page： 134301(8 pp) 2013.4

Assessment of multi-pulse laser-induced damage threshold of metallic mirrors for Thomson scattering system Reviewed

M.Sato, S.Kajita, R.Yasuhara, N.Ohno, M.Tokitani, N.Yoshida, Y.Tawara

Optics Express Vol. 21 ( 8 ) page： 9333-9342 2013.4

Comparison of damages on tungsten surfac exposed to noble gas plasmas Reviewed

M.Yajima, M.Yamagiwa, S.Kajita, N.Ohno et al.

Plasma Science & Technol. Vol. 15 page： 282-286 2013.3

Two-dimensional visualization of excitation temperature and chemical species in divertor plasmas: Trace CD molecules by chemical sputtering of fusion plasma reactor wall Reviewed

Z.Cui, K.Kodama, M.Yamamoto, Q.Shen, M.Yoshimi, S.Kajita, N.Ohno, K.Kitagawa

Microchemical Journal Vol. 106 page： 174-179 2013.1

Influence of the Probe Electrode on Probe Measurements for Atmospheric Pressure Microwave Plasma Torch Reviewed International journal

Ezumi N., Kodama N., Akahane K., Shiozawa S., Sawada K., Ohno N.

Contributions to Plasma Physics Vol. 53 ( 1 ) page： 81 - 85 2013.1

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Contributions to Plasma Physics

In this study, in order to clarify the influence of a probe electrode during probe measurements of an atmospheric pressure microwave plasma, simultaneous observations of probe current and the change of plasma shape using a high-speed camera have been done. Fast and random repetitions of attachment and detachment of the plasma torch to the probe electrode have been observed. It is found that the response time is related to ion sound speed. Different behaviors of the plasma torch for a floating metal electrode or an insulator have been observed. Probe current-voltage characteristics show asymmetric double probe shape © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOI： 10.1002/ctpp.201310014

First Principles Investigation on Trapping of Multiple Helium Atoms within a Tungsten Monovacancy Reviewed

A.Takayama, A.M.Ito, S.Saito, N.Ohno, H.Nakamura

Japanese Journal of Applied Physics Vol. 52 page： 01AL03(4 pp) 2013

Deuterium Atomic Density Estimation in Recombining Plasmas Using Self-Absorption Spectroscopy Reviewed

S.Kajita, T.Nishiwaki, N.Ohno, K.Sawada, M.Takagi

IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING Vol. 8 ( 1 ) page： 1-6 2013

Observation of Arc Spots Initiated on Nanostructured Tungsten Reviewed

S.Kajita, N.Ohno, S.Takamura

IEEE TRANSACTIONS ON PLASMA SCIENCE Vol. 41 ( 8, Part 2 ) page： 1889-1895 2013

Intermittent transport in edge plasma with a 3-D magnetic geometry in the Large Helical Device Reviewed

H.Tanaka, S.Masuzaki, N.Ohno, T.Morisaki, Y.Tsuji, the LHD Experiment Group

Journal of Nuclear Materials Vol. 438 page： S563-S566 2013

Extension of operation regimes and investigation of three-dimensional currentless plasmas in the Large Helical Device Reviewed

O.Kaneko, H.Yamada, S.Inagaki, M.Jakubowski, S.Kajita, et al.(N.Ohno is the 104th author))

Nucl. Fusion Vol. 53 page： 104015(11 pp) 2013

First-Principles Investigation on Trapping of Multiple Helium Atoms within a Tungsten Monovacancy Reviewed

A.Takayama, A.M.Ito, S.Saito, N.Ohno, H.Nakamura

Jpn. J. Appl. Phys. Vol. 52 page： 01AL023(4 pp) 2013

Effect of resistivity profile on current decay time of initial phase of current quench in neon-gas-puff inducing disruptions of JT-60U Reviewed

S.Kawakami, Y.Shibata, K.Y.Watanabe, N.Ohno, A.Isayama, T.Takizuka, Y.Kawano, M.Okamoto

Physics of Plasmas Vol. 20 page： 112507(6 pp) 2013

Degradation of optical reflectivity of in-vessel mirror materials by helium bombardment Reviewed

S.Kajita, M.Tokitani, T.Saekim N.Ohno, N.Yoshida

J. Nucl. Mater. Vol. 417 page： 838-841 2013

Behavior of Plasma Response Field in Detached Plasma Reviewed International journal

NARUSHIMA Yoshiro, KOBAYASHI Masahiro, AKIYAMA Tsuyoshi, SAKAKIBARA Satoru, MASUZAKI Suguru, ASHIKAWA Naoko, OHNO Noriyasu

Plasma and Fusion Research Vol. 8 ( 0 ) page： 1402058 - 1402058 2013

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：プラズマ・核融合学会

Sustaining a detached plasma is important for the reduction of the heat load on a divertor. The externally controlled methods such as gas puffing in the divertor region, etc. have been studied for maintaining detached plasmas. In the recent LHD experiments, a resonant magnetic perturbation (RMP) is utilized to establish the detached plasma, which is one of the candidates to reduce the divertor heat load. The finite plasma response field has been detected when the RMP is imposed, and its behavior is investigated from the viewpoint of the magnetic island dynamics. A parameter of the phase difference, Δθ (defined as the phase difference between the plasma response field and the RMP), changes from antiphase to in-phase while the plasma transits from the attached to the detached states. Finally, when the Δθ reaches at certain critical value, Δθcrit, the plasma enters the detached state. Since this critical value does not have a dependency on plasma beta and collisionality, Δθcrit seems to be a threshold to establish the detached plasma. From the viewpoint of magnetic island dynamics, the behavior of Δθ approaching in-phase implies the "trend" of island growth. The detached plasma might be established in the case of the tendency for the plasma response field to reinforce the island width.

DOI： 10.1585/pfr.8.1402058

Thermal radiation characteristics and direct evidence of tungsten cooling on the way to nanostructure formation on its surface Reviewed International journal

Takamura S., Miyamoto T., Ohno N.

Journal of Nuclear Materials Vol. 438 ( SUPPL ) 2013

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Nuclear Materials

The physical properties of tungsten with nanostructure on its surface are investigated focusing on the thermal radiation and cooling characteristics. First, direct evidence of substantial W surface cooling has been clearly shown with use of a very thin thermocouple inserted into W target, which solves an uncertainty associated with a radiation thermometer. Second, the above measurements of W surface temperature make it possible to estimate quantitatively the total emissivity from which we may evaluate the radiative power through the Stefan-Boltzmann equation, which is very important for mitigation evaluation of a serious plasma heat load to the plasma-facing component. © 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2013.01.176

Preliminary experiments on the vertical stability with helical coils in a small tokamak, HYBTOK-II Reviewed International journal

Hatakeyama S., Shibata Y., Kawakami S., Tsutsui H., Tsuji-Iio S., Shimada R., Ohno N., Akiyama T., Suzuki Y., Watanabe K.

39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics Vol. 1 page： 285 - 288 2012.12

Language：English Publishing type：Research paper (international conference proceedings) Publisher：39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics

In summary, we proposed saddle shaped stellarator system for vertical mode in toka-mak. These preliminary results demonstrate the feasibility of vertical stability, even if only two selected coils which are localized at one side of the torus. However as noted earlier, the experiment were conducted with the circular cross-section tokamak which is stable vertically. Further work is needed to confirm the improvement in the vertical stability in elongated tokamaks. In addition, very large coil current comparable to the plasma current are needed in our system. In order to reduce the current, future work also should focus on optimal configuration of the coils.

Blob/Hole Generation in the Divertor Leg of the Large Helical Device Reviewed

H.Tanaka, N.Ohno, Y.Tsuji, S.Kajita, S.Masuzaki, M.Kobayashi, T.Morisaki, A.Komori and the LHD Experimental Group

Plasma and Fusion Research Vol. 7 page： 1402152(6 pp) 2012.11

Fatal Damages due to Breakdown on a Diagnostic Mirror Located outside the Vacuum Vessel in JT-60U Reviewed

S.Kajita, T.Hatae, T.Sakuma, S.Takamura, N.Ohno, K.Itami

Plasma and Fusion Research Vol. 7 page： 2405121(4 pages) 2012.9

Optical properties of nanostructured tungsten in near infrared range Reviewed

S.Kajita, N.Ohno, T.Yokochi, N.Yoshida, R.Yoshihara, S.Takamura, T.Hatae

Plasma Physics and Controlled Fusion Vol. 54 page： 105015(7 pages) 2012.9

Superimposition of Pulses to Steady Arc Discharge in Toroidal Divertor Simulator Reviewed

S.Kajita, T.Uchiyama, N.Ohno

Plasma and Fusion Research Vol. 7 page： 1405100(6 pages) 2012.7

Statistical Analysis of the Spatial Behavior of Plasma Blobs Around the Plasma Column in a Linear Plasma Device Reviewed

H.Tanaka, N.Ohno, Y.Tsuji, K.Okazaki, S.Kajita

Contrib. Plasma Phys. Vol. 52 ( 5-6 ) page： 424 - 428 2012.6

Effect of Externally Applied Resonance Magnetic Perturbation on Current Decay during Tokamak Disruption Reviewed

Y.Kanazawa, Y.Shibata, M.Okamoto, N.Ohno, S.Kajita

Plasma and Fusion Research Vol. 7 page： 1202049(2 pages) 2012.6

Effect of neutral pressure on the He plasma flow measurement in a linear device Reviewed International coauthorship

E.-K.Park, H.-J.Woo, K.-S.Chung, H.Tanaka, S.Kajita, N.Ohno

Current Applied Physics Vol. 12 page： 1479 - 1502 2012.5

Transition in Plasma Fluctuation between Attached and Detached Plasmas Reviewed

K.Okazaki, H.Tanaka, N.Ohno, S.Kajita

Plasma and Fusion Research Vol. 7 page： 1201033(2 pages) 2012.4

Arcing on tungsten subjected to helium and transients: ignition conditions and erosion rates Reviewed International journal

S.Kajita, N.Ohno, N.Yoshida, R.Yoshihara, S.Takamura

PLASMA PHYSICS AND CONTROLLED FUSION Vol. 54 ( 3 ) 2012.2

Language：English Publishing type：Research paper (scientific journal) Publisher：IOP PUBLISHING LTD

Arcing is a long standing plasma-surface interaction issue in nuclear fusion research, and the issue has been revived recently from new points of view. In this study, arcing under fusion relevant conditions is demonstrated in a linear plasma device using a pulsed laser to mimic the transient heat load. Ignition conditions of arcing were investigated systematically by changing the laser power, plasma conditions, surface nature and so on. Moreover, the cross-sectional view of arc trail was observed by transmission electron microscope, and the erosion of nanostructured tungsten due to arcing was estimated. It was found that more than half of the nanostructured tungsten still remained after an arc spot run on the nanostructure.

DOI： 10.1088/0741-3335/54/3/035009

TEM analysis of high temperature annealed W nanostructure surfaces Reviewed International journal

Shin Kajita, Naoaki Yoshida, Reiko Yoshihara, Noriyasu Ohno, Takanori Yokochi, Masayuki Tokitani, Shuichi Takamura

JOURNAL OF NUCLEAR MATERIALS Vol. 421 ( 1-3 ) page： 22 - 27 2012.2

Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV

Helium plasma irradiation and electron heating experiments were conducted using tungsten in the divertor simulator NAGDIS-II. Helium plasma irradiation to tungsten led to the formation of nanostructures on the surface, while the nanostructures were annihilated after the potential of the specimen was changed to positive for several 10 min so that electrons irradiated the sample without ion irradiation. The specimens were analyzed in detail by transmission electron microscope with the help of focused ion beam technique. It is revealed that the helium nano-bubbles still remained even after the nanostructures were disappeared from the surface. Porosity of the nanostructured tungsten was measured from the TEM images. (c) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2011.11.044

Anisotropic Graphite Erosion in Low-Temperature and high-Density Deuterium Plasma Reviewed

M.Teraoka, N.Ohno, S.Kajita, T.Nishiwaki, A.M.Ito, H.Nakamura

Jpn. J. Appl. Phys. Vol. 51 page： 01AB03 (5pp) 2012.1

Near Infrared Radiation from Heated Nanostructured Tungsten Reviewed

S.Kajita, T.Yokochi, N.Ohno, T.Kumano

Jpn. J. Appl. Phys. Vol. 51 page： 01AJ03 (5pp) 2012.1

Measurement of ion and electron temperatures in plasma blobs by using an improved ion sensitive probe system and statistical analysis methods Reviewed International journal

K. Okazaki, H. Tanaka, H. Tanaka, N. Ohno, N. Ezumi, Y. Tsuji, S. Kajita

Review of Scientific Instruments Vol. 83 2012.1

Language：English Publishing type：Research paper (scientific journal)

We have measured ion temperature as well as electron temperature in plasma blobs observed in a linear plasma device by using an improved ion sensitive probe. Current-voltage characteristics of the ion sensitive probe inside and outside plasma blobs were re-constructed with a conditional sampling method. It is clearly found that both ion and electron temperatures in plasma blobs decrease more slowly in a cross-field direction than those in a bulk plasma without plasma blobs. © 2012 American Institute of Physics.

DOI： 10.1063/1.3681778

Electric Field at a Plasma-Facing Wall for a Two-Temperature Electron Distribution Reviewed

Y.Tomita, G.Kawamura, M.Ueno, N.Ohno, Z.H.Huang, Y.D.Pan, L.W.Yan

Contrib. Plasma Phys. Vol. 52 ( 5-6 ) page： 484-489 2012

Thermionic Energy Converter System Using Heat Flux in Divertor Region Reviewed

D.Oikawa, N.Ohno, S.Kajita, M.Takagi, S.Masuzaki, M.Tokitani, K.Asano

Plasma and Fusion Research Vol. 7 page： 1405050(8 pages) 2012

Conditions for the Release of a Metallic Dust Particle from a Plasma-Facing Wall Reviewed

M.Ueno, N.Ohno, Y.Tomita, G.Kawamura

Contrib. Plasma Phys. Vol. 52 ( 5-6 ) page： 478-483 2012

Effects of fibre-form nanostructures on particle emissions from a tungsten surface in plasmas Reviewed

S.Takamura, T.Miyamoto, N.Ohno

Nuclear Fusion Vol. 52 page： 123001(8 pages) 2012

Validation of the current decay model in the initial phase of current quench in high disruptive discharges of JT-60U Reviewed International journal

Shibata Y., Watanabe K., Ohno N., Okamoto M., Isayama A., Kurihara K., Oyama N., Nakano T., Kawano Y., Sugihara M.

38th EPS Conference on Plasma Physics 2011, EPS 2011 - Europhysics Conference Abstracts Vol. 35 2 page： 1628 - 1631 2011.12

Language：English Publishing type：Research paper (scientific journal) Publisher：38th EPS Conference on Plasma Physics 2011, EPS 2011 - Europhysics Conference Abstracts

The validation of current decay model during the current quench was investigated in high (3p disruptive discharges on JT-60U. It is experimentally confirmed that the electron temperature does not play an important role in the determination of the current decay time in the initial phase of current quench and that values obtained from L/R model are two orders of magnitude larger than the experimental current decay time. The current decay time predicted by the modified L/R model, in which the time derivative of plasma inductance is taken into account, is in fairly good agreement with the experimental data. In future work, we need to perform the MHD equilibrium code for free-boundary condition such as DINA [5] and TSC [6] code under the axisymmetric assumption in order to clear up the determination mechanism of time derivative of plasma inductance.

Recent progress of tungsten R&D for fusion application in Japan Reviewed International journal

Ueda Y., Lee H.T., Ohno N., Kajita S., Kimura A., Kasada R., Nagasaka T., Hatano Y., Hasegawa A., Kurishita H., Oya Y.

Physica Scripta T Vol. T145 2011.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Physica Scripta T

The status of ongoing research projects of tungsten R&D in Japan is summarized in this paper. For tungsten material development, a new improved fabrication technique, the so-called superplasticity-based microstructural modification, is described. This technique successfully improved fracture strength and ductility at room temperature. Recent results on vacuum plasma spray W coating and W brazing on ferritic steels and vanadium alloys are explained. Feasibility of these techniques for the manufacture of the blanket is successfully demonstrated. The latest findings on the effect of neutron damage in tungsten on T retention and on the change in mechanical and electrical properties are described. Retention characteristics for neutron-damaged W were different compared to those for ion-damaged W. Upon neutron irradiation, tungsten alloys containing transmutation elements of W (Re and Os) show changes in properties that are different compared with those shown by pure W. The effects of mixed plasma exposure (D/He/C) are described. Both D/He and D/C mixed ion irradiations significantly affect ion-driven permeation in W. He bubble dynamics play a key role in nano-structure formation on the W surface. © 2011 The Royal Swedish Academy of Sciences.

DOI： 10.1088/0031-8949/2011/T145/014029

Deuterium retention in Fe <inf>2</inf>O <inf>3</inf> under low-energy deuterium-plasma exposure Reviewed International journal

Matsunami N., Sogawa T., Sakuma Y., Ohno N., Tokitani M., Masuzaki S.

Physica Scripta T Vol. T145 2011.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Physica Scripta T

Stainless steel (SUS) is used as the structure material in nuclear fusion devices. Heating and O 2 plasma discharge are considered for the removal of tritium. Oxide layer growth is anticipated on heating SUS at a high temperature in low-pressure residual O 2 gas. When O 2 plasma discharge is performed, oxygen plasma reaches the structure material and iron oxides such as Fe 2O 3 are formed. Thus, a knowledge of the retention behavior of hydrogen isotopes or deuterium (D) in the oxide layers is important in designing the devices. We investigated D retention in Fe 2O 3 films and the influence of Fe 2O 3 crystal structure on D retention and found that D retention in γ-Fe 2O 3 (cubic-maghemite) is larger than that in α-Fe 2O 3 (hexagonal-hematite). The results for Fe 2O 3 are compared with those for SUS and Fe. © 2011 The Royal Swedish Academy of Sciences.

DOI： 10.1088/0031-8949/2011/T145/014042

TEM observation of the growth process of helium nanobubbles on tungsten: Nanostructure formation mechanism Reviewed International journal

Kajita Shin, Yoshida Naoaki, Yoshihara Reiko, Ohno Noriyasu, Yamagiwa Masato

JOURNAL OF NUCLEAR MATERIALS Vol. 418 ( 1-3 ) page： 152 - 158 2011.11

Helium bubble formation on tungsten in dependence of fabrication method Reviewed International journal

Yamagiwa Masato, Kajita Shin, Ohno Noriyasu, Takagi Makoto, Yoshida Naoaki, Yoshihara Reiko, Sakaguchi Wataru, Kurishita Hiroaki

JOURNAL OF NUCLEAR MATERIALS Vol. 417 ( 1-3 ) page： 499 - 503 2011.10

Nanoscale surface morphology of tungsten materials induced by Be-seeded D-He plasma exposure Reviewed International journal

Tokunaga K., Baldwin M. J., Doerner R. P., Nishijima D., Kurishita H., Fujiwara T., Araki K., Miyamoto Y., Ohno N., Ueda Y.

JOURNAL OF NUCLEAR MATERIALS Vol. 417 ( 1-3 ) page： 528 - 532 2011.10

Exfoliation of the tungsten fibreform nanostructure by unipolar arcing in the LHD divertor plasma Reviewed International journal

Tokitani M., Kajita S., Masuzaki S., Hirahata Y., Ohno N., Tanabe T.

NUCLEAR FUSION Vol. 51 ( 10 ) 2011.10

Development of Nanostructured Black Metal by Self-Growing Helium Bubbles for Optical Application Reviewed International journal

S.Kajita, T.Saeki, Y.Hirahata, M.Yajima, N.Ohno, R.Yoshihara, N.Yoshida

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 50 ( 8 ) page： 08JG01 2011.8

Investigation on the effect of temperature excursion on the helium defects of tungsten surface by using compact plasma device Reviewed

S.Takamura, T.Miyamoto, Y.Tomida, T.Minagawa, N.Ohno

Journal of Nuclear Materials Vol. 415 page： S100-S103 2011.8

Exposure of tungsten nano-structure to TEXTOR edge plasma Reviewed International coauthorship

Y.Ueda, K.Miyata, Y.Ohtsuka, H.T.Lee, M.Fukumoto, S.Brezinsek, J.W.Coenen, A.Kreter, A.Litnovsky, V.Philipps, B.Schweer, G.Sergienko, T.Hirai, A.Taguchi, Y.Torikai, K.Sugiyama, T.Tanabe, S.Kajita, N.Ohno, The TEXTOR team

Journal of Nuclear Materials Vol. 415 ( 1 ) page： S92 - S95 2011.8

Divertor simulation experiment and its future research plan making use of a large tandem mirror device Reviewed International journal

Nakashima Y., Takeda H., Hosoi K., Yonenaga R., Katanuma I., Ichimura K., Ichimura M., Imai T., Ishii T., Kariya T., Kiwamoto Y., Minami R., Miyata Y., Ozawa H., Shidara H., Yamaguchi Y., Yoshikawa M., Asakura N., Hatayama A., Higashizono Y., Kado S., Masuzaki S., Nishino N., Ohno N., Ueda Y.

Journal of Nuclear Materials Vol. 415 ( 1 SUPPL ) 2011.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Nuclear Materials

Divertor simulation study has been started as a new research plan, by making best use of a large linear plasma device. The experiment of generating the plasma flow with high heat and particle flux was successfully performed at an end-mirror exit of the GAMMA 10 tandem mirror. In typical hot-ion-mode plasmas, the heat-flux density of 0.6 MW/m2 and the particle-flux density of 1022 particles/s m2 were simultaneously achieved in the case of only ICRF heating and superimposing the 300 kW ECH pulse attained the peak value of the net heat-flux up to 8 MW/m2 on axis. The above experimental results and the simulation analysis of ICRF heating using the Fokker-Planck code give a clear prospect of generating the required performance for divertor studies by building up the plasma heating systems to the end-mirror cell. Detailed behavior of the plasma flow and the future research plan are also described. © 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2010.11.081

Motion of unipolar arc spots ignited on a nanostructured tungsten surface Reviewed

S.Kajita, S.Takamura, N.Ohno

Plasma Physics and Controlled Fusion Vol. 53 ( 7 ) page： 074002 2011.5

Molecular Dynamics Simulation of Hydrogen Injection onto Diamond Surfaces Reviewed

H.Nakamura, A.M.Ito, S.Saito, A.Takayama, Y.Tamura, N.Ohno, S.Kajita

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 50 ( 1 ) page： 01AB04(4 pages) 2011.1

Molecular Dynamics Simulation of Chemical Vapor Deposition of Amorphous Carbon: Dependence on H/C Ratio of Source Gas Reviewed

A.M.Ito, A.Takayama, S.Saito, N.Ohno, S.Kajita, H.Nakamura

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 50 ( 1 ) page： 01AB01(6 pages) 2011.1

Formation of Metallic Nanostructure by Helium Plasma Irradiation Reviewed

S.Kajita, T.Saeki, Y.Hirahata, N.Ohno

JAPANESE JOURNAL OF APPLIED PHYSICS Vol. 50 ( 1 ) page： 01AH02 2011.1

Practical selection of emission lines of He I to determine the photon absorption rate Reviewed

S.Kajita, N.Ohno

Review of Scientific Instruments Vol. 82 page： 023501(5 pages) 2011

Formation and decay processes of Ar/He microwave plasma jet at atmospheric gas pressure Reviewed

S.Takamura, S.Amano, T.Kurata, H.Kasada, J.Yamamoto, M.A.Razzak, G.Kushida, N.Ohno, M.Kando

Journal of Applied Physics Vol. 110 page： 043301 (8 pages) 2011

Deuterium retention in Fe2O3 under low-energy deuterium-plasma exposure Reviewed

N.Matsunami, T.Sogawa, Y.Sakuma, N.Ohno, M.Tokitani, S.Masuzaki

Physica Scripta Vol. T145 page： 014042 (4pp) 2011

In situ measurement of hydrogen isotope retention using a high heat flux plasma generator with ion beam analysis Reviewed

M.Yamagiwa, Y.Nakamura, N.Matsunami, N.Ohno, S.Kajita, M.Takagi, M.Tokitani, S.Masuzaki, A.Sagara and K.Nishimura

Physica Scripta Vol. T145 page： 014032 (5pp) 2011

Recent progress of tungsten R&D for fusion application in Japan Reviewed

Y.Ueda, H.T.Lee, N.Ohno, S.Kajita, A.Kimura, R.Kasada, T.Nagasaka, Y.Hatano, A.Hasegawa, H.Kurishita and Y.Oya

Physica Scripta Vol. T145 page： 014029 (6pp) 2011

Beryllium erosion induced by transient heat loads and subsequent reactions in a deuterium plasma Reviewed

S.Kajita, D.Nishijima, R.Doerner, K.Umstadter, J.Yu, N.Ohno, Y.Ueda

Journal of Nuclear Materials Vol. 420 page： 252-257 2011

Study of Plasma Current Decay in the Initial Phase of High Poloidal Beta Disruptions in JT-60U Reviewed International journal

SHIBATA Yoshihide, MATSUNAGA Go, KAMADA Yutaka, SUGIHARA Masayoshi, WATANABE Kiyomasa, OHNO Noriyasu, OKAMOTO Masaaki, ISAYAMA Akihiko, KURIHARA Kenichi, OYAMA Naoyuki, NAKANO Tomohide, KAWANO Yasunori

Plasma and Fusion Research ( 6 ) page： 1302136 - 1302136 2011

Language：English Publishing type：Research paper (scientific journal) Publisher：社団法人プラズマ・核融合学会

In order to validate some current decay models during the current quench, the plasma current decay time was studied using the experimental plasma resistance and inductance in high poloidal beta, βp, disruptions in JT-60U. The plasma resistance and inductance were evaluated from an equilibrium calculation code and the measurement value of a magnetic sensor, the electron temperature evaluated by using ECE measurement and the electron density measured by FIR interferometer. In high βp disruptions, it was found that the electron temperature at the plasma center just after current quench starts was approximately 1-4 keV under almost the same current decay time observed during the initial phase of current quench. This result indicates that the electron temperature itself plays no major role in the determination of the current decay time in the initial phase of current quench. Moreover, the current decay time predicted by a modified L/R model [Y. Shibata et al., Nucl. Fusion 50, 025015 (2010)], in which the time derivative of plasma inductance was considered, was in good agreement with the experimental current decay time, while the values obtained from the conventional L/R model were two orders of magnitude larger than the experimental results.

DOI： 10.1585/pfr.6.1302136

Midterm summary of Japan-US fusion cooperation program TITAN Reviewed International journal

Muroga T., Sze D.K., Okuno K., Terai T., Kimura A., Kurtz R.J., Sagara A., Nygren R., Ueda Y., Doerner R.P., Sharpe J.P., Kunugi T., Morley N.B., Hatano Y., Sokolov M.A., Yamamoto T., Hasegawa A., Katoh Y., Ohno N., Tokunaga K., Konishi S., Fukada S., Calderoni P., Yokomine T., Messadek K., Oya Y., Hashimoto N., Hinoki T., Hashizume H., Norimatsu T., Shikama T., Stoller R.E., Tanaka K.A., Tillack M.S.

Fusion Science and Technology Vol. 60 ( 1 ) page： 321 - 328 2011

Language：English Publishing type：Research paper (scientific journal) Publisher：Fusion Science and Technology

Japan-US cooperation program TITAN (Tritium, Irradiation and Thermofluid for America and Nippon) started in April 2007 as 6-year project. This is the summary report at the midterm of the project. Historical overview of the Japan-US cooperation programs and direction of the TITAN project in its second half are presented in addition to the technical highlights.

DOI： 10.13182/FST11-A12373

Deuterium uptake in iron oxide (Fe<inf>2</inf>O<inf>3</inf>) under D <inf>2</inf>+-plasma exposure Reviewed International journal

Sogawa T., Matsunami N., Ohno N., Tokitani M., Masuzaki S.

AIP Conference Proceedings Vol. 1321 page： 274 - 277 2010.12

Language：English Publishing type：Research paper (scientific journal) Publisher：AIP Conference Proceedings

We have studied implantation of low-energy deuterium ions into Fe 2O3 films and deuterium (D)-uptake in Fe2O 3 films, which were prepared by oxidation of Fe sheets in air at 400°C for 20 min. X-ray diffraction (XRD) shows that the films are mixture of hexagonal α-Fe2O3 (hematite) and cubic γ-Fe2O3 (maghemite). According to Rutherford backscattering spectroscopy (RBS) of 1.8 MeV H+, the composition is found to be crudely stoichiometric (Fe:O=2:3). The samples were subjected to D2+-plasma exposure using AC-glow discharge. The amount of D-uptake in Fe2O3 is evaluated to be ∼6×10 16cm2 for AC voltage of 1.5 kV in 0.4 Torr of D 2 gas for 15 min. The amount of D-uptake in Fe2O 3 appears to be larger by a factor of three than that in Fe. Comparisons of XRD patterns and RBS spectra before and after D2+-plasma exposure show no appreciable change of the crystalline structure, quality and composition. © 2010 American Institute of Physics.

DOI： 10.1063/1.3548377

2D Measurement of Edge Plasma Dynamics by Using High-Speed Camera Based on HeI Line Intensity Ratio Method Reviewed

Ohno N., Miyamoto K., Kodama K., Kajita S., Kitagawa K.

CONTRIBUTIONS TO PLASMA PHYSICS Vol. 50 ( 10 ) page： 962 - 969 2010.11

Enhancement of cross-field transport into the private region of detached-divertor in Large Helical Device Reviewed

H. Tanaka, N. Ohno, Y. Tsuji, S. Kajita, S. Masuzaki, M. Kobayashi, T. Morisaki, H. Tsuchiya, A.Komori, and LHD Experimental Group

Physics of Plasmas Vol. 17 page： 102509(8pages) 2010.10

Nanostructured Black Metal: Novel Fabrication Method by Use of Self-Growing Helium Bubbles Reviewed

S.Kajita, T.Saeki, N.Yoshida, N.Ohno, A.Iwamae

Applied Physics Express Vol. 3 page： 085204-1-3 2010.7

2D Statistical Analysis of Non-Diffusive Transport under Attached and Detached Plasma Conditions of the Linear Divertor Simulator Reviewed

H.Tanaka, N.Ohno, Y.Tsuji, S.Kajita

CONTRIBUTIONS TO PLASMA PHYSICS Vol. 50 ( 3-5 ) page： 256 - 266 2010.5

Basic Study on the Generation of RF Plasmas in Premixed Oxy-combustion with Methane Reviewed International coauthorship International journal

Y.Osaka, N.Kobayashi, M.A.Razzak, N.Ohno, S.Takamura, Y.Uesugi

Plasma and Fusion Research ( 5 ) page： 010 2010.3

Language：English Publisher：社団法人プラズマ・核融合学会

Oxy-combustion generates a high temperature field (above 3000 K), which is applied to next generation power plants and high temperature industrial technologies because of N2 free processes. However, the combustion temperature is so high that the furnace wall may be fatally damaged. In addition, it is very difficult to control the heat flux and chemical species' concentrations because of rapid chemical reactions. We have developed a new method for controlling the flame by electromagnetic force on this field. In this paper, we experimentally investigated the power coupling between the premixed oxy-combustion with methane and radio frequency (RF) power through the induction coil. By optimizing the power coupling, we observed that the flame can absorb RF power up to 1.5 kW. Spectroscopic measurements also showed an increase in the emission intensity from OH radicals in the flame, indicating improved combustibility.

DOI： 10.1585/pfr.5.010

Study of current decay time during disruption in JT-60U tokamak Reviewed

Y.Shibata, K.Y.Watanabe, M.Okamoto, N.Ohno, A.Isayama, K.Kurihara, T.Nakano, N.Oyama, Y.Kawano, G.Matsunaga, S.Sakakibara, M.Sugihara, Y.Kamada and the JT-60U team

Nuclear Fusion Vol. 50 page： 025015 (7pp) 2010

Formation Condition of Fiberform Nanostructured Tungsten by Helium Plasma Exposure Reviewed

W. Sakaguchi, S. Kajita, N. Ohno, et al.

Plasma Fusion Research Vol. 5 page： S1023(5pages) 2010

Design study of the divertor Thomson scattering system for JT-60SA Reviewed

S. Kajita, T. Hatae, K. Itami, N. Ohno, T. Nakano

J. Plasma Fus. Res. Series Vol. 9 page： 157-162 2010

2D Measurement of Edge Plasma Dynamics by Using High-Speed Camera Based on HeI Line Intensity Ratio Method Reviewed

N.Ohno, K.Miyamoto, K.Kodama, S.Kajita, K.Kitagawa

Contrib. Plasma Physics Vol. 50 ( 10 ) page： 962-969 2010

Deepening of Floating Potential for Tungsten Target Plate on the way to Nanostructure Formation Reviewed

S.Takamura, T.Miyamoto and N.Ohno

Plasma and Fusion Research: Rapid Communications Vol. 5 page： 039(2 pages) 2010

Compact Plasma Device for PWI Studies Reviewed

S.Takamura, T.Tsujikawa, Y.Tomida, K.Suzuki, T.Minagawa, T.Miyamoto, N.Ohno

J. Plasma Fusion Res. SERIES Vol. 9 page： 441-445 2010

2D Statistical Analysis of Non-Diffusive Transport under Attached and Detached Plasma Conditions of the Linear Divertor Simulator Reviewed

H.Tanaka, N.Ohno, Y.Tsuji, S.Kajita

Contrib. Plasma Physics Vol. 50 ( 3-5 ) page： 256-266 2010

Self-Affine Fractality of Bifurcating Arc Trail in Magnetized Plasma Reviewed

Shin KAJITA, Noriyasu OHNO, Yoshiyuki TSUJI, Hirohiko TANAKA, and Shuichi TAKAMURA

Journal of the Physical Society of Japan Vol. 79 ( 5 ) page： 054501(7 pages) 2010

Fluid Mechanical Characteristics of Microwave Discharge Jet Plasmas at Atmospheric Gas Pressure Reviewed

S.Takamura, S.Saito, G.Kushida, M.Kando, N.Ohno,

IEEJ Trans. FM Vol. 130 ( 5 ) page： 493-500 2010

Comparison with Surfaces of Diamond and Graphite for Adsorption of Hydrogen Reviewed

H.Nakamura, A.Ito, S.Saito, Y.Tamura, S.Fujiwara, N.Ohno, S.Kajita

Proceedings of ITC19, 2009 Vol. 1 2010

Recent progress in understanding the behavior of dust in fusion devices Reviewed

S.I.Krasheninnikov, A.Yu Pigarov, R.D.Smirnov, M.Rosenberg, Y.Tanka, D.J.Benson, T.K.Soboleva, T.D.Rognlien, D.A.Mendis, B.D.Bray, D.L.Rudakov, J.H.Yu, W.P.West, A.L.Roquemore, C.H.Skinner, J.L.Terry, B.Lipschultz, A.Bader, R.S.Granetz, C.S.Pitcher, N.Ohno, S.Takamura, S.Masuzaki, N.Ashikawa, M.Shiratani, M.Tokitani, R.Kumazawa, N.Asakura, T.Nakano, A.J.Litnovsky, R.Maqueda and the LHD Experimental Group

Plasma Physics and Controlled Fusion Vol. 50 ( 12 ) page： 124054(13 pp) 2010

Degradation of optical reflectivity of in-vessel mirror materials by helium bombardment Reviewed

S.Kajita, T.Saeki, N.Ohno, M.Tokitani, T.Hatae, W.Sakaguchi

J. Nuclear Mater. 2010

Tungsten blow-off in response to the ignition of arcing: revival of arcing issue in future fusion devices Reviewed

S.Kajita, S.Takamura, N.Ohno

J. Nuclear Mater. 2010

Comparison of Hydrogen Adsorption on Diamond and Graphite Surfaces Reviewed International journal

NAKAMURA Hiroaki, ITO Atsuhi M., SAITO Seiki, TAMURA Yuichi, FUJIWARA Susumu, OHNO Noriyasu, KAJITA Shin

Plasma and Fusion Research ( 5 ) page： S2072 - S2072 2010

Language：English Publishing type：Research paper (scientific journal) Publisher：社団法人プラズマ・核融合学会

By a classical molecular dynamics (CMD) simulation with a modified Brenner's reactive empirical bond-order (REBO) potential, we found that graphite with zigzag (1010) and armchair (1120) edge states is destroyed more easily than other structures, i.e., graphite with the (0001) surface, and diamond with the (100), (111), (120), and (110) surfaces. Experimental results indicated that graphite is eroded under hydrogen atom injection with Ein = 0.3 eV, and that diamond is not eroded under the same conditions. Our simulation results are consistent with these experimental results. We also reveal the temperature and saturation dependence of the surface structure of carbon crystals.

DOI： 10.1585/pfr.5.S2072

Steady-State Operation Scenario and the First Experimental Result on QUEST Reviewed International journal

HANADA Kazuaki, MAEKAWA Takashi, KISHIMOTO Yasuaki, ISHIGURO Masaki, YOSHINAGA Tomokazu, IGAMI Hiroe, NISHINO Nobuhiro, HONMA Hiroshi, KAWASAKI Shoji, NAKASHIMA Hisatoshi, HIGASHIJIMA Aki, SATO Kohnosuke, HIGASHIZONO Yuta, ANDO Akira, ASAKURA Nobuyuki, EJIRI Akira, HIROOKA Yoshihiko, ISHIDA Akio, KOMORI Akio, MATSUKAWA Makoto, MOTOJIMA Osamu, OGAWA Yuichi, ZUSHI Hideki, OHNO Noriyasu, ONO Yasushi, PENG Martin, SUDO Shigeru, YAMADA Hiroshi, YOSHIDA Naoaki, YOSHIDA Zensho, NAKAMURA Kazuo, SAKAMOTO Mizuki, IDEI Hiroshi, HASEGAWA Makoto, TAKASE Yuichi, MITARAI Osamu

Plasma and Fusion Research ( 5 ) page： S1007 - S1007 2010

Language：English Publishing type：Research paper (scientific journal) Publisher：社団法人プラズマ・核融合学会

QUEST focuses on the steady state operation of the spherical tokamak by controlled PWI and electron Bernstein wave current drive. One of the main purposes of QUEST is an achievement of long duration discharge with MW-class injected power. As the result, QUEST should be operated in the challenging region on heat and particle handling. To do the particle handling, high temperature all metal wall up to 623 K and closed divertors are planned, which is to realize the steady-state operation under recycling ratio, R = 1. This is a dispensable check to DEMO, because wall pumping should be avoided as possible in the view of tritium retention. The QUEST project will be developed in increment step such as, I. low β steady state operation in limiter configuration, II. low β steady state operation in divertor configuration, III. relatively high β steady state operation in closed divertor configuration. Phase I in the project corresponds to these two years, and final goal of phase I is to make full current drive plasma up to 20 kA. Closed divertor will be designed and tested in the Phase II. QUEST is running from Oct., 2008 and the first results are introduced.

DOI： 10.1585/pfr.5.S1007

Formation process of tungsten nanostructure by the exposure to helium plasma under fusion relevant plasma conditions Reviewed

S.Kajita, W.Sakaguchi, N.Ohno, N.Yoshida, T.Saeki

Nuclear Fusion Vol. 49 page： 095005(6pp) 2009.8

Development of Divertor Plasma Simulators with High Heat Flux Plasmas and its Application to Nuclear Fusion Study : A Review Reviewed International journal

OHNO Noriyasu, KAJITA Shin, TAKAGI Makoto, TAKAMURA Shuichi

IEEJ transactions on electrical and electronic engineering : official journal of the Institute of Electrical Engineering of Japan / = 電気学会 Vol. 4 ( 4 ) page： 476 - 487 2009.7

Ray tracing simulation for radiation trapping of the He I resonance transition in a linear plasma device Reviewed International coauthorship

S.Kajita, D.Nishijima,E.M.Hollmann, N.Ohno

Physics of Plasmas Vol. 16 page： 063303 2009.6

Investigation of detached recombining deuterium plasma and carbon chemical erosion in the toroidal divertor simulator NAGDIS-T Reviewed

K.Yada, N.Matsui, N.Ohno, S.Kajita, S.Takamura, M.Takagi

Journal of Nuclear Materials Vol. 390-391 page： 290 - 294 2009.6

Spherical cauliflower-like carbon dust formed by interaction between deuterium plasma and graphite target and its internal structure Reviewed International journal

Ohno N., Yoshimi M., Tokitani M., Takamura S., Tokunaga K., Yoshida N.

JOURNAL OF NUCLEAR MATERIALS Vol. 390-91 page： 61 - 64 2009.6

Deuterium retention in tungsten oxide under low energy D<inf>2</inf>+ plasma exposure Reviewed International journal

Matsunami N., Ohno N., Tokitani M.

Journal of Nuclear Materials Vol. 390-391 ( 1 ) page： 693 - 695 2009.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Nuclear Materials

W is a candidate for plasma facing material and oxide layers are highly anticipated on W surface. We have studied deuterium (D) retention in tungsten oxide (WO3) films and thermal release of deuterium. WO3 films, prepared by oxidation of W metal sheet, were exposed to D2 plasma under AC glow discharge at the applied voltage V up to a few kV and DC discharge. D-retention in W has been studied for comparison. The amount of D retained in the WO3 films and W were analyzed by detecting α particles from the nuclear reaction, D(3He, α)p, using 0.7 MeV 3He+ ions. We find that D-uptake in WO3 film is much larger than in W. According to thermal desorption, release of D2 occurs at ∼180 and 450 °C. © 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jnucmat.2009.01.191

Erratum: Comparison of He I line intensity ratio method and electrostatic probe for electron density and temperature measurements in NAGDIS-II (Physics of Plasmas (2006) 13 (013301)) Reviewed International journal

Kajita S., Ohno N., Takamura S., Nakano T.

Physics of Plasmas Vol. 16 ( 2 ) 2009.3

Prompt ignition of a unipolar arc on helium irradiated tungsten Reviewed

S.Kajita, S.Takamura and N.Ohno

Nuclear Fusion Vol. 49 page： 032002(4pp) 2009.2

Development of Divertor Plasma Simulators with High Heat Flux Plasmas and Its Application to Nuclear Fusion Study Reviewed

大野哲靖

IEEJ Transactions 4 page： 476 - 487 2009

Visualized blow-off from helium irradiated tungsten in response to ELM-like heat load Reviewed

S.Kajita, N.Ohno, W.Sakaguchi, M.Takagi

Plasma and Fusion Research Vol. 4 page： 004(6 pages) 2009

In situ reflectivity of tungsten mirrors under helium plasma exposure Reviewed

W.Sakaguchi, S.Kajita, N.Ohno, M.Takagi

Journal of Nuclear Materials page： doi:10.1016/j.jnucmat.2009.01.276 2009

Statistical analysis to the SOL plasma fluctuation in JT-60U Reviewed

N. Asakura, N. Ohno, H. Tanaka, H. Kawashima, T. Nakano

J.Nucl. Mater. Vol. 390-391 page： 364-367 2009

Effects of tungsten surface conditions on carbon deposition Reviewed

Y. Ueda, M. Fukumoto, A. Yamawaki, Y. Soga, Y. Ohtsuka, S. Brezinsek, T. Hirai, A. Kirschner, A. Kreter, A. Litnovsky, V. Philipps, A. Pospieszczyk, B. Schweer, G. Sergienko, T. Tanabe, K. Sugiyama, K. Ohya, N. Ohno and The TEXTOR team

J.Nucl. Mater. Vol. 390-391 page： 44-48 2009

Deuterium retention in Tungsten Oxyside under low-voltage D2+ plasma exposure Reviewed

N.Matsunami, N.Ohno and M.Tokitani

J.Nucl. Mater. Vol. 390-391 page： 693-695 2009

Development of net-current free heliotron plasmas in the Large Helical Device Reviewed

A.Komori, H.Yamada, S.Sakakibara, O.Kaneko, K.Kawahata, T.Mutoh, N.Ohyabu, S.Imagawa, K.Ida, Y.Nagayama, T.Shimozuma, K.Y.Watanabe, T.Mito, M.Kobayashi, K.Nagaoka, R.Sakamoto, N.Yoshida, S.Ohdachi, N.Ashikawa, Y.Feng, T.Fukuda, H.Igami, S.Inagaki, H.Kasahara, S.Kubo, R.Kumazawa, O.Mitarai, S.Murakami, Y.Nakamura, M.Nishiura, T.Hino, S.Masuzaki, K.Tanaka, K.Toi, A.Weller, M.Yoshinuma, Y.Narushima, N.Ohno, T.Okamura, N.Tamura, K.Saito, T.Seki, S.Sudo, H.Tanaka, T.Tokuzawa, N.Yanagi, M.Yokoyama, Y.Yoshimura, T.Akiyama, H.Chikaraishi, M.Chowdhuri, M.Emoto, N.Ezumi, H.Funaba, L.Garcia, P.Goncharov, M.Goto, K.Ichiguchi, M.Ichimura, H.Idei, T.Ido, S.Iio, K.Ikeda, M.Irie, A.Isayama, T.Ishigooka, M.Isobe, T.Ito, K.Ito, A.Iwamae, S.Hamaguchi, T.Hamajima, S.Kitajima, S.Kado, D.Kato, T.Kato, S.Kobayashi, K.Kondo, S.Masamune, Y.Matsumoto, N.Matunami, T.Minami, C.Michael, H.Miura, J.Miyazaa, N.Mizuguchi, T.Morisaki, S.Morita, G.Motojima, I.Murakami, S.Muto, K.Nagasaki, N.Nakajima, Y.Nakamura, H.Nakanishi, H.Nakano, K.Narihara, A.Nishimura, H.Nishimura, K.Nishimura, S.Nishimura, N.Nishino, T.Notake, T.Obana, K.Ogawa, Y.Oka, T.Ohishi, H.Okada, K.Okuno, K.Ono, M.Osakabe, T.Osako, T.Ozaki, B.J.Peterson, H.Sakaue, M.Sasao, S.Satake, K.Sato, M.Sato, A.Shimizu, M.Shiratani, M.Shoji, H.Sugama, C.Suzuki, Y.Suzuki, K.Takahata, H.Takahashi, Y.Takase, Y.Takeiri, H.Takenaga, S.Toda, Y.Toda, M.Tokitani, H.Tsuchiya, K.Tsumori, H.Urano, E.Veshchev, F.Watanabe, T.Watanabe, T.H.Watanabe, I.Yamada, S.Yamada, O.Yamagishi, S.Yamaguchi, S.Yoshimura, T.Yoshinaga and O.Motojima

Nuclear Fusion Vol. 49 page： 104015(8pp) 2009

Direct observation of cathode spot grouping using nanostructured electrode Reviewed

S.Kajita, N.Ohno, S.Takamura, Y.Tsuji

Physics Letters A Vol. 373 page： 4273-4277 2009

Discharge Bifurcation of Microwave-sustained Helium Plasma Torch at Atmospheric Pressure Reviewed

S.Takamura, M.Kando, N.Ohno

J.Plasma Fusion Res. SERIES Vol. 8 page： 910-913 2009

High temperature irradiation damage of carbon materials studies by laser Raman spectroscopy Reviewed

M.Yoshida, T.Tanabe, N.Ohno, M.Yoshimi, S.Takamura

Journal of Nuclear Materials Vol. 386-388 page： 841-843 2009

*Development of Divertor Plasma Simulators with High Heat Flux Plasmas and its Application to Nuclear Fusion Study: A Review Reviewed

N.Ohno, S.Kajita, M.Takagi, S.Takamura

TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING IEEJ Trans. Vol. 4 page： 476,487 2009

Formation and mitigation of fiberform nanostructured tungsten by helium and sub-ms laser pulse irradiations Reviewed

S.Kajita, W.Sakaguchi and N.Ohno

Plasma Devices and Operations Vol. 17 page： 165,173 2009

Statistical analysis of fluctuation characteristics at high- and low-field sides in L-mode SOL plasmas of JT-60U Reviewed

H.Tanaka, N.Ohno, N.Asakura, Y.Tsuji, H.Kawashima, S.Takamura, Y.Uesugi and the JT-60U Team

Nuclear Fusion Vol. 49 page： 65017 2009

*Spherical cauliflower-like carbon dust formed by interaction between deuterium plasma and graphite target and its internal structure Reviewed

N.Ohno, M.Yoshimi, M.Tokitani, S.Takamura, K.TOkunaga, N.Yoshida

Journal of Nuclear Materials page： doi:10.1016/j.jnucmat.2009.01.051 2009

Statistical properties of edge plasma turbulence in the Mega-Amp Spherical Tokamak and the Large Helical Device Reviewed International coauthorship International journal

Dewhurst J., Hnat B., Ohno N., Dendy R., Masuzaki S., Morisaki T., Komori A., Dudson B., Counsell G., Kirk A.

35th EPS Conference on Plasma Physics 2008, EPS 2008 - Europhysics Conference Abstracts Vol. 32 ( 2 ) page： 898 - 901 2008.12

Deuterium retention near surface of TiO<inf>2</inf> by low-voltage D <inf>2</inf> plasma discharge Reviewed International journal

Matsunami N., Tanaka T., Ohno N., Tokitani M.

Physica Status Solidi (C) Current Topics in Solid State Physics Vol. 5 ( 4 ) page： 923 - 926 2008.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Physica Status Solidi (C) Current Topics in Solid State Physics

We have investigated deuterium (D) uptake in TiO2 (rutile) films under exposure of low-energy D2+ ions and thermal release of D from TiO2 films. The amount of deuterium in the films was analysed by means of nuclear reaction analysis, D(3He, α)p. D-uptake under AC-glow discharge in D2 pressure of ∼90 Pa is compared with that under DC-discharge with well-defined energy of D 2+ ions in D2 pressure of ∼0.1 Pa. The results imply that the effective energy of D2+ ions in AC-glow discharge is much lower than the energy derived from the applied voltage. The results are also compared with those for Ti sheet exposed to low-energy D2+ ions. We find that D-release temperature from TiO2 is considerably lower than from Ti, though D-uptake in TiO2 is smaller than in Ti. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.

DOI： 10.1002/pssc.200778343

11th International Workshop on Plasma Edge Theory in Fusion Devices: Preface Reviewed International coauthorship International journal

Heikkinen J., Ohno N.

Contributions to Plasma Physics Vol. 48 ( 1-3 ) 2008.3

Measurement of Plasma Properties of the Atmospheric Oxy-Combustion Flame by Using Double Probe Method Reviewed

Y.Osaka, N.Kobayashi, N.Ohno, S.Takamura, Y.Tanaka, Y.Uesugi

Contrib. Plasma Physics Vol. 48 ( 5-7 ) page： 485-490 2008

Intermittency and extended self-similarity in space and fusion plasma: boundary effects Reviewed

V.P.Budaev, S.Savin, L.Zelencyi, N.Ohno, S.Takamura and E.Amata

Plasma Physics and Controlled Fusion Vol. 50 page： 074014(20pp) 2008

Extended self-similarity of intermittent turbulencein edge magnetized plasmas Reviewed

V.P. Budaev, N. Ohno, S.Takamura, S. Masuzaki, A. Komori, T. Morisaki

Nuclear Fusion Vol. 48 page： 24014 2008

Deuterium retention near surface of TiO2 by low-voltage D2 plasma discharge Reviewed

N.Matsunami, T.Tanaka, N.Ohno and M.Tokitani

Phys. Stat. Sol.(c) Vol. 5 ( 4 ) page： 923-926 2008

ELM propagation in the low- and high- filed-side Scrape-off Layer of the JT-60U tokamak Reviewed

N.Asakura, H.Kawashima, N.Ohno, G.Matsunaga, T.Nakano and N.Oyama

Journal of Physics; Conference Series Vol. 123 page： 012009(11pp) 2008

Statistical properties of edge plasma turbulence in the Large Helical Device Reviewed

J.M.Dewhurst, B.Hnat, N.Ohno, R.O.Dendy, S.Masuzaki, T.Morisaki and A.Komori

Plasma Physics and Controlled Fusion Vol. 50 page： 095013(15pp) 2008

Fluctuating Helium Emission in Optically Thick Divertor Plasmas Reviewed

F. B. Rosmej, N. Ohno, S. Takamura, S. Kajita

Contributions to Plasma Physics Vol. 48 page： 243-248 2008

Numerical Modeling of Behavior of Dust Made of Different Materials in Plasmas Reviewed

Y. Tanaka, A. Yu. Pigarov, R. D. Smirnov, S. I. Krasheninnikov, N. Ohno, Y. Uesugi

Contributions to Plasma Physics Vol. 48 page： 295-299 2008

Extended Self-Similarity in Edge Plasma Turbulence of Fusion Devices Reviewed

V. P. Budaev, N. Ohno, S. Takamura, S. Masuzaki, A. Komori, T. Morisaki

Contributions to Plasma Physics Vol. 48 page： 42-47 2008

Plasma Rotation Measurements by Passive Spectroscopic Method in the HYBTOK-II using a Dynamic Ergodic Divertor Reviewed

Y.Hasebe, M.Okamoto, S.Kajita, N.Ohno and S.Takamura

Plasma and Fusion Research Vol. 3 page： S1015 2008

ELM propagation in the low- and high-field-side scrape-off layer of the JT-60U tokamak Reviewed International journal

Asakura N., Kawashima H., Ohno N., Matsunaga G., Nakano T., Oyama N.

Journal of Physics: Conference Series Vol. 123 2008

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physics: Conference Series

In JT-60U, the filament structure of Edge Localized Modes (ELMs) is measured at three poloidal locations, and their temporal evolution is investigated at the inner (high magnetic-field-side, HFS) SOL as well as outer (low magnetic-field-side, LFS) SOL. At the inner SOL, filament structure with 7-8 temporal multi-peaks in ion-saturation probe signals and other diagnostics is, for the first time, measured close to the sepatratrix. The delay of the first peak after the start of MHD activity is faster than the characteristic time of the parallel convection from the outer midplane, and the Mach numbers of the plasma parallel flow reach ion sonic levels. These results show that ELM filaments extend from the outer to the inner plasma edge, and that a part of the filaments are ejected into the inner SOL. The toroidal mode numbers (n) and poloidal width of the filaments (δz) are evaluated from the interval of the multi-peaks and duration of each peak, yielding n ∼ 18-44 and δz ∼ 2-6 cm on the HFS SOL, while n and δz are comparable on the LFS SOL. After the multi-peaks appear, flow reversal of the SOL plasma toward is observed over a wide region of the inner SOL. © 2008 IOP Publishing Ltd.

DOI： 10.1088/1742-6596/123/1/012009

Plasma-assisted laser ablation of tungsten: Reduction in ablation power threshold due to bursting of holes/bubbles Reviewed International journal

Kajita S., Ohno N., Takamura S., Sakaguchi W., Nishijima D.

Applied Physics Letters Vol. 91 ( 26 ) 2007.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Applied Physics Letters

Nanosecond laser ablation of tungsten (W) exposed to helium plasma is investigated using optical emission spectroscopy. Submicrometer-sized holes/bubbles are formed on the surface of W when it was exposed to the helium plasma at a sufficiently high temperature (1500-1600 K). The emissions from a virgin W (before the helium plasma irradiation) cannot be detected when the fluence is <1 J cm2; however, the threshold fluence for the detection of neutral W emission after it was exposed to the helium plasma is ∼0.2 J cm2. The physical mechanism of laser-induced bursting of holes/bubbles is proposed for achieving a significant reduction in ablation power threshold. © 2007 American Institute of Physics.

DOI： 10.1063/1.2824873

Effect of cross-field transport on H- density profile in magnetized plasmas: Comparison between measurement and simulation Reviewed International journal

Kajita S., Kado S., Ohno N., Takamura S., Kurihara K., Kuwahara Y.

Physics of Plasmas Vol. 14 ( 10 ) 2007.11

Language：English Publishing type：Research paper (scientific journal) Publisher：Physics of Plasmas

The radial density profile of negative hydrogen ions in magnetized plasma is investigated in the divertor simulator MAP (Material and plasma)-II [S. Kado et al., J. Plasma Fusion Res. 71, 810 (2005)] by measurement and numerical simulation. The laser photodetachment method is used to evaluate the H - density by considering the influence of the magnetic field. The density of H- has a hollow profile and exhibits a peak in the peripheral region, though the electron density and temperature exhibit a peak at the center of the plasma column. The density profile of H- does not agree with the calculation result obtained from, the rate equation, in which the local production and extinction rates are balanced, under the present experimental condition. To understand the behavior of negative ions, their trajectories are calculated by numerically solving the equation of motion by considering the effect of collisions. The negative ion density profile calculated from the particle simulation agrees well with the measured negative ion density profile. It is shown that the cross-field H- transport due to the radial electric field with the assistance of the elastic collisions plays an important role in enhancing the negative ion density in the peripheral region. © 2007 American Institute of Physics.

DOI： 10.1063/1.2789559

Sub-ms Laser Pulse Irradiation on Tungsten Target Damaged by Exposure to Helium Plasma Reviewed

S.Kajita, S.Takamura, N.Ohno, D.Nishijima, H.Iwakiri, N.Yoshida

Nuclear Fusion Vol. 47 page： 1358 - 1366 2007.9

Integrated view of disruption dynamics on internal electromagnetic and plasma structures in the small tokamak HYBTOK-II Reviewed

M. Okamoto, S. Takamura, N. Ohno, S. Kajita, Y. Kikuchi, Y. Uesugi, T. Ozeki, Y. Kawano, M. Sugihara

Nuclear Fusion Vol. 47 page： 1106 - 1111 2007.8

Surface modification at tungsten and tungsten coated graphite due to low energy and high fluence plasma and laser pulse irradiation Reviewed International journal

Ohno N., Kajita S., Nishijima Dai, Takamura S.

JOURNAL OF NUCLEAR MATERIALS Vol. 363 page： 1153 - 1159 2007.6

Modeling of Dust-particle Behavior for Different Materials in Plasmas Reviewed

Y.Tanaka, A.Yu.Pigarov, R.D.Smirnov, S.I.Krasheninnikov, N.Ohno, Y.Uesugi

Physics of Plasmas Vol. 14 page： 52504 2007.5

Systematic Analysis of Current Decay Time during Disruption in HYBTOK-II Tokamak Reviewed

M.Okamoto, N.Ohno, S.Takamura

Plasma and Fusion Research Vol. 3 page： 6 2007

Effect of Cross-field Transport on H-Density Profile in Magnetized Plasmas: Comparison Between Measurement and Simulation Reviewed

S.Kajita, S.Kado, N.Ohno, K.Kurihara, Y.Kuwahara, S.Takamura

Physics of Plasmas Vol. 14 page： 103503 2007

Plasma-assisted Laser Ablaion of Tungsten: Reduction in Ablation Power Threshold Due to Bursting of Holes/Bubbles Reviewed

S.Kajita, N.Ohno, S.Takamura, W.Sakaguchi, D.Nishijima

Applied Physics Letters Vol. 9191 page： 261501 2007

Development of Tungsten Materials for Plasma Facing Components in Japan Reviewed

Y.Ueda, N.Ohno, S.Kajita, H.Kurishita, H.Iwakiri et al

Fusion Science and Technology Vol. 52 page： 513-520 2007

Overview of JT-60U results for the Development of a Steady-state Advanced Tokamak Scenario Reviewed

H.Takenaga, the JT-60 Team

Nuclear Fusion Vol. 47 page： S563-S578 2007

Structural Bifurcation of Microwave Helium Jet Discharge at Atmospheric Pressure Reviewed

S.TAKAMURA, M.KITOH, T.SOGA, H.TAKASHIMA, Y.NISHINO, S.HAYAKAWA, Y.BAN, T.YUHKI, M.KANDO, N.OHNO

Plasma and Fusion Research Vol. 3 page： 12 2007

High density plasma generation by RF ohmic discharge in toroidal divertor simulator NAGDIS-T Reviewed

M. Nagase, H. Masuda, N. Ohno, S. Takamura and M. Takagi

Journal of Nuclear Materials Vol. 363-365 page： 611-615 2007

Alleviation of Damaged Tungsten Having Helium Holes/Bubbles by Use of Transient Heat Load Reviewed

S.Kajita, S.Takamura, N.Ohno, T.Nishimoto

Plasma Fusion Research Vol. 2 page： 9 2007

Extended Steady-state and High-beta Regimes of Net-current Free Heliotron Plasmas in the Large Helical Device Reviewed

O.Motojima, H.Yamada, A.Komori, N.Ohyabu, T.Mutoh, O.Kaneko, K.Kawahata, T.Mito, K.Ida, S.Imagawa, Y.Nagayama, T.Shimozuma, K.Y.Watanabe, S.Masuzaki, J.Miyazawa, T.Morisaki, S.Morita, S.Ohdachi, N.Ohno, K.Saito, S.Sakakibara, Y.Takeiri, N.Tamura, K.Toi, M.Tokitani, M.Yokoyama, M.Yoshinuma, K.Ikeda, A.Isayama, K.Ishii S.Kubo, S.Murakami, K.Nagasaki, T.Sekim K.Takahata, H.Takenaga and the LHD Experimental Group

Nuclear Fusion Vol. 47 page： S668-S676 2007

Plasma-surface Interaction, Scrape-off Layer and Divertor Physics: Implications for ITER Reviewed

B.Lipschultz, X.Bonnin, G.Counsell, A.Kallenbach, A.Kukushkin, K.Krieger, A.Leonard, A.Loarte, .Neu, R.A.Pitts, T.Rognlien, J.Roth, C.Skinner, J.L.Terry, E.Tsitrone, D.Whyte, S.Zweben, N.Asakura, D.Coster, R.Doerner, R.Dux, G.hendrih, A.Herrmann, J.Hu, S.Krasheninnikov, G.Kirnev, A.Kreter, V.Kurnaev, B.LaBombard, S.Lisgo, T.Nakano, N.Ohno, H.D.Pacher, J.Paley, Y.Pan, G.Pautasso, V.Philipps, V.Rohde, D.Rudakov, P.Stangeby, S.Takamura, T.Tanabe, Y.Yang, S.Zhu

Nuclear Fusion Vol. 47 page： 1189-1205 2007

High Density Plasma Generation by RF Ohmic Discharge in Toroidal Divertor Simulator NAGDIS-T Reviewed

M.Nagase, H.Masuda, N.Ohno, S.Takamura, M.Takagi

J. Nucl. Mater. Vol. 363-365 page： 611-615 2007

Dynamic Interaction between Disruptive Plasma and Wall in the Small Tokamak HYBTOK-II Reviewed

M.Okamoto, T.Yamada, T.Hiraishi, Y.Kikuchi, N.Ohno, S.Takamura

J. Nucl. Mater. Vol. 363-365 page： 1076-1080 2007

Alleviation of Helium Holes/Bubbles on Tungsten Surface by Use of Transient Heat Load Reviewed International journal

KAJITA Shin, TAKAMURA Shuichi, OHNO Noriyasu, NISHIMOTO Tentaro

Plasma and Fusion Research ( 2 ) page： 9 - 9 2007

Language：English Publishing type：Research paper (scientific journal) Publisher：社団法人プラズマ・核融合学会

The alleviation effect of transient heat load on helium holes/bubbles has been demonstrated using ruby laser pulses for the transient heat source in the divertor simulator NAGDIS-II. It is shown that the holes and bubbles disappeared following the irradiation of the ruby laser pulses, while the surface roughness was significantly enhanced by the irradiation of the Nd:YAG laser pulses. Based on the numerically calculated temperature in the specimen, the physical mechanism causing this difference is discussed particularly in terms of pulse width (0.6 ms for ruby laser without a Q-switch and 5 ns for Nd:YAG laser with a Q-switch).

DOI： 10.1585/pfr.2.009

Plasma response on penetration of external rotating helical magnetic field in HYBTOK-II tokamak edge plasma Reviewed International journal

Budaev V.P., Pankratov I.M., Takamura S., Ohno N., Kajita S., Takagi M., Matsuno H., Okamoto M., Hosoi S., Hasebe Y., Yamada T., Omelchenko A.Y., Olshansky V.V.

33rd EPS Conference on Plasma Physics 2006, EPS 2006 Vol. 2 page： 1548 - 1551 2006.12

Intermittency in laboratory and space plasmas: Comparative study of multifractal statistics Reviewed International coauthorship International journal

Budaev V., Savin S., Zelenyi L., Takamura S., Ohno N., Shevyrev N.

33rd EPS Conference on Plasma Physics 2006, EPS 2006 Vol. 1 page： 344 - 347 2006.12

Reduction of laser power threshold for melting tungsten due to subsurface helium holes Reviewed International journal

Kajita Shin, Nishijima Dai, Ohno Noriyasu, Takamura Shuichi

JOURNAL OF APPLIED PHYSICS Vol. 100 ( 10 ) 2006.11

Modification of the damping rate of the oscillations of a dust particle levitating in a plasma due to the delayed charging effect Reviewed International coauthorship International journal

Pustylnik M.Y., Ohno N., Takamura S., Smirnov R.

Physical Review E - Statistical, Nonlinear, and Soft Matter Physics Vol. 74 ( 4 ) 2006.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Physical Review E - Statistical, Nonlinear, and Soft Matter Physics

Dependence of the damping rate of the oscillations of the dust particles levitating in the sheath on the plasma parameters is investigated both theoretically and experimentally. Significant deviations of the damping rate from the values predicted by the Epstein formula are found in the experiment. The delayed charging effect is applied for the theoretical explanation of the experimental results. Qualitative agreement between the theoretical and experimental data is obtained. © 2006 The American Physical Society.

DOI： 10.1103/PhysRevE.74.046402

Superdiffusion and multifractal statistics of edge plasma turbulence in fusion devices Reviewed International coauthorship International journal

Budaev V.P., Takamura S., Ohno N., Masuzaki S.

Nuclear Fusion Vol. 46 ( 4 ) 2006.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Nuclear Fusion

The edge plasma turbulence in the T-10 tokamak, the HYBTOK-II tokamak, the linear machine NAGDIS-II and the Large Helical Device have been studied. The fluctuations in the plasma density have been analysed in terms of the multifractal formalism revisited with wavelets. In most of the cases considered, the edge density fluctuations demonstrate multifractal statistics, i.e. the scaling behaviour of the absolute moments is described by a convex function with non-trivial self-similarity properties. The multifractality factor defined in the multiplicative cascade model is a relevant parameter for characterizing the edge plasma turbulence. The multiplicative cascade process has a 'coarse' time scale T ∼ 50-200 ms iterating towards finer scales. This time scale is referred to as an integral correlation scale. The self-similarity parameters have been observed to depend on the edge plasma condition. The correlation and transport properties have been analysed regarding the multifractality parameter. The diffusion transport coefficient in an edge plasma is not a trivial function of multifractality parameters. © 2006 IAEA, Vienna.

DOI： 10.1088/0029-5515/46/4/S10

Comparison of HeI Line Intensity Ratio Method and Electrostatic Probe for Electron Density and Temperature Measurements in NAGDIS-II Reviewed

S.Kajita, N.Ohno, S.Takamura, T.Nakano

Physics of Plasmas Vol. 13 page： 013301(9pages) 2006.1

Numerical Analysis on Generation of High Density Plasmas in the Toroidal Device NAGDIS-T for SOL and Divertor Simulation Studies Reviewed

M.Nagase, S.Takamura, N.Ohno, H.Masuda, H.Kitahara, M.Takagi

Contrib. Plasma Physics Vol. 46 page： 557-562 2006

Charactersitics of rf inductive plasma in oxy-combustion

Yugo Osaka, Noriyuki Kobayashi, M.A.Razzak, Noriyasu Ohno, Shuichi Takamura

The 4th International Conference on Combustion, Incineration/Pyrolysis and Emission Control, September 26-29, 2006, Kyoto, Japan Vol. 1 2006

Fundamental research on plasma-assisted combustion by applying rf power

Yugo Osaka, Noriyuki Kobayashi, M.A.Razzak, Noriyasu Ohno, Shuichi Takamura

11th Asian Pacific Confederation of Chemical Engineering Congress, August 27-30, 2006 Kuala Lumpur, Malaysia Vol. 1 2006

Dust Formation and Transport in the Divertor Plasma Simulators

N.Ohno, M.Miyoshi, T.Yamada, M.Pustylnik, S.Kajita, S.Takamura

7th Workshop ont Fine Particle Plasma, NIFS, oki, Japan December, 15-16, 2006(招待講演) Vol. 1 2006

Two-dimensional measurement of plasma dynamics with an ICCD fast camera based on HeI line intensity ratio method

N.Yamamoto, K.Miyamoto, K.Kitagawa, S.Kajita, M.Okamoto, N.Ohno

16th International Toki Conference on Advanced Imaging and Plasma Diagnostics, Toki, Gifu, Japan, Dec. 5-8, 2006 page： 6-15 2006

Imaging of tungsten impurity ejected from damaged material due to transient heat load

S.Kajita, N.Ohno, S.Takamura

16th International Toki Conference on Advanced Imaging and Plasma Diagnostics, Toki, Gifu, Japan, Dec. 5-8, 2006 page： 4-01 2006

ELM Propagation and Fluctuations Characteristics in H- and L-mode SOL Plasmas on JT-60U

N.Asakura, N.Ohno, H.Kawashima, H.Miyoshi, G.Matsunaga, N.Oyama, S.Takamura, Y.Uesugi, M.Takechi, T.Nakano, H.Kubo

21st IAEA Fusion Energy Conference, Chengdu, China, Oct. 16-21, 2006 page： EX/9-2 2006

Integrated View of Disruption Dynamics on Internal Electromagnetic and Plasma Structures in the small tokamak HYBTOK-II

M.Okamoto, S.Takamura,N.Ohno, S.Kajita, Y.Kikuchi, Y.Uesugi, T.Ozeki, Y.Kawano, M.Sugihara

21st IAEA Fusion Energy Conference, Chengdu, China, Oct.16-21,2006 page： EX/P8-14 2006

Super Dense Core Plasma due to Internal Diffusion Barrier in LHD

N.Ohyabu, .Morisaki, S.Masuzaki, R.Sakamoto, M.Kobayashi, J.Miyazawa, M.SHoji, T.Akiyama, N.Ashikawa, M.Emoto, H.Funaba, P.Goncharov, M.Goto, J.H.Harris, Y.Hirooka, K.Ichiguchi, T.Ido, K.Itoh, H.Igami, K.Ikeda, S.Inagaki, H.KAsahara, T.Kobuchi, S.Kubo, R.Kumazawa, S.Morita, S.Muto, K.Nagaoka, N.Nakajima, Y.Nakamura, H.Nakanishi, K.Nariharam Y.Narushima, M.Nishiura, T.Notake, S.Ohdachi, N.Ohno, Y.Oka, M.Osakabe, T.Ozaki, B.J.Peterson, K.Saito, S.Sakakibara, R.Sanchez, H.Sanuki, K.Sato, T.Seki, A.SHimizu, H.SUgama, C.Suzuki, Y.Suzuki, Y.Takeiri, K.Tanaka, N.Tamura, K.TOi, T.Tokuzawa, S.TOda, K.Tsumori, I.Yamada, O.Yamagishi, M.Yokoyama, S.Yoshimura, Y.Yoshimura, M.Yoshinuma, K.Ida, T.Shimozuma, K.Y.Watanabe, Y.Nagayama, O.Kaneko, T.Mutoh, K.Kawahata, H.Yamada, A.Komori, S.Sudo, O.Motojima

21st IAEA Fusion Energy Conference, Chengdu, China, Oct.16-21, 2006 page： EX/8-1 2006

Bursty Fluctuation Characterisitics in SOL/Divertor Plasmas of Large Helical Device

N.Ohno, S.Masuzzaki, V.P.Budaev, H.Miyoshi, S.Takamura, T.Morisaki, N.Ohyabu, A.Komori

21st IAEA Fusion Energy Conference, Chengdu, China, Oct 16-21, 2006 page： EX/P4-20 2006

Extended Steady-State and High=beta Regimes of Net-Current Free Heliotron Plasmas in the Large Helical Device

O.Motojima, H.Yamada, A.Komori, O.Kaneko, K.Kawahata, T.Mito, T.Mutoh, N.Ohyabu K.Ida, S.Imagawa, Y.Nagayama, T.Shimozuma, K.Y.Watanabe, S.Masuzakim J.Miyazawa, S.Morita, S.Ohdachi, N.Ohno, K.Saito, S.Sakakibara, Y.Takeiri, N.Tamura, K.Toi, M.Tokitani, M.Yokoyama, M.Yoshinuma, K.Ikeda, A.Isayama, K.Ishii, S.Kubo, S.Murakami, K.Nagasaki, T.Seki, K.Takahata, H.Takenaga, LHD Experimental Group

21st IAEA Fusion Energy Conference, Chengdu, China, Oct.16-21. 2006 page： OV/2-1 2006

Plasma-surface interaction, scrape-off layer and divertor physics: Implications for ITER

B.Lipschultz, X.Bonnin, A.Kukushkin, A.Leonard, J.Roth, E.Tsitrone, D.Whyte, N.Asakura, D.Coster, G.Counsell, R.Doerner, R.Dux, G.Federici, M.Fenstermacher, W.Fundamenski, P.Ghendrih, A.Hermann, J.Hu, A.Kallenbach, S.Kasheninnikov, K.Krieger, G.Krienev, A.Kreter, B.Kurnaev, B.LaBombard, S.Lisgom A.Loarte, T.Nakano, R.Neu, N.Ohno, H.Pacher, J.Paley, Y.Pan, G.Pautasso, V.Philipps, R.Pitts, V.Riccardo, V.Rohde, D.Rudakov, P.Stangeb, S.Takamura, T.Tanabe, Y.Yang, S.Zhu

21st IAEA Fusion Energy Confernece, Chnegdu, China, Oct.16-21, 2006 page： IT/1-4 2006

Effects of transient heat load on tungsten surface having sub-micron helium holes and bubbles

S.Kajita, N.Ohno, S.Takamura

33rd EPS Conference on Plasma Phys. Rome, 19-23 June 2006 ECA Vol. 30I page： 4.137 2006

Plasma Response on Penetraton of External Rotating Helical Magnetic Field in HYBTOK-II Tokamak Edge Plasma

V.P.Budaev, I.M.Pankratov, S.Takamura, N.Ohno, S.Kajita, M.Takagi, H.Matsuno, M.Okamoto, S.Hosoi, Y.Hasebe, T.Yamada, A.Ya.Omelchenko, V.V.Olshansky

33rd EPS Conference on Plasma Phys. Rome, 19-23 June 2006 ECA Vol. 30I page： 4.109 2006

Intermittency in laboratory and space plasma: comparative study of multifractal statistics

V.P.Budaev, S.P.Savin, L.M.Zelenyi, S.Takamura, N.Ohno, N.Shevyrev

33rd EPS Conference of Plasma Phys. Rome, 19-23 June 2006 ECA Vol. 30I page： 1.064 2006

Investigation and Application of the Line Intensity Ratio Method for the Measurement of Electron Density and Temperature

S.Kajita, T.Hiraishi, N.Ohno, M.Okamoto, T.Nakano, S.Takamura

13th International Congress on Plasma Physics, Kiev, May 22-26, 2006 page： A151p 2006

Dynamic Interaction between Disruptive Plasma and Wakk in the Small Tokamak HYBTOK-II

M.Okamoto, T.Yamada, T.Hiraishi, Y.Kikuchi, N.Ohno, S.Takamura

17th PSI Conference, Heifei, China, May 22-26, 2006 page： 2-15 2006

High Density Plasma Generation by RF Ohmic Discharge in Toroidal Divertor Simulator NAGDIS-T

M.Nagase, H.Matsuda, N.Ohno, S.Takamura, M.Takagi

17th PSI Conference, Heifei, China, May 22-26, 2006 page： 3-16 2006

Carbon Dust Formation and Chemical Erosion Process in High Density Deuterium Plasmas in the Linear Divertor Simulator

Y.Miyachi, M.Yoshimi, N.Ohno, S.Takamura

17th PSI Conference, Heifei, China, May 22-26, 2006 page： 2-50 2006

Fundamental study on the control of oxy-combustion by rf non-equilibrium plasma Reviewed

Y.Osaka, N.Kobayashi, M.A.Razzak, N.Ohno, S.Takamura

Fluid and heat engineering research Vol. 41 page： 5-12 2006

Formation of Nanostructured Tungsten with Arborescent Shape due to Helium Plasma Irradiation Reviewed

S.Takamura, N.Ohno, D.Nishijima, S.Kajita

Plasma Fusion Res. Vol. 1 page： 051(2pages) 2006

Reduction of Laser Threshold for Melting Tungsten due to Subsurface Helium Holes Reviewed

S.Kajita, D.Nishijima, N.Ohno, S.Takamura

J. Appl. Phys. Vol. 100 page： 103304(10 pages) 2006

Modification of the Damping Rate of the Oscillation of a Dust Particle levitating in a Plasma Due to the Delayed Charging Effect Reviewed

M.Y.Pustylnik, N.Ohno, S.Takamura, R.Smirnov

Phys. Rev. E Vol. 74 page： 046402(9pages) 2006

Analysis on Relation between Magnetic Structure and Bursty Fluctuation in SOL/Divertor Plasma of LHD Reviewed

N.Ohno, S.Masuzaki, H.Miyoshi, S.Takamura, V.P.Budaev, T.Morisaki, N.Ohyabu, A.Komori

Contrib. Plasma Physics Vol. 46 page： 692-697 2006

Control of Energetic Electron Component in a Magnetically Confined Diffusion Ar Plasma Reviewed

M.Pustylnik, N.Ohno, S.Takamura

Japanese Journal of Applied Physics Vol. 45 ( 2A ) page： 926-932 2006

The Effect of the Rotating Helical Fields on the Plasma Edge in the HYBTOK-II Tokamak Reviewed

V.P.Budaev, I.M.Pankratov, S.Takamura, N.Ohno, M.Takagi, H.Matsuno, M.Okamoto, S.K.Saha

Nucl. Fusion Vol. 46 page： S175-S180 2006

Fast Ignition and Mode Transition of Radio Frequency Induction Plasmas at Atmospheric Pressure using tungsten Pin Electrode Array Reviewed

M.Razzak, S.Takamura, N.Ohno

Plasma Fusion Res. Vol. 1 page： 006/Letters(3pages) 2006

Assessment of Meander-Line Antenna covered with Dielectric Material for LHW Heating Reviewed

H.Matsuno, S.Takamura, S.Hosoi, N.Ohno

Plasma & Fusion Res. Vol. 1 page： 0009(6pages) 2006

Validity of Electron Temperature Measurement by Using Boltzmann Plot Method in Radio Freauency Inductive Discharge in the Atmospheric Pressure Range Reviewed

N.Ohno, M.Razzak, H.Ukai, S.Takamura, Y.Uesugi

Plasma Fusion Res. Vol. 1 page： 028(9pages) 2006

Fast Initiation and Mode Transition of Radio Frequency Induction Plasmas at Atmospheric Pressure Using Tungsten Pin Electrodes Array Reviewed International journal

RAZZAK M. Abdur, TAKAMURA Shuichi, OHNO Noriyasu

Plasma and Fusion Research ( 1 ) page： 6 - 6 2006

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：社団法人プラズマ・核融合学会

The effects of using an array of tungsten pin electrodes on the ignition dynamics of radio frequency (rf) discharges generated by inductively coupled plasma (ICP) technique at atmospheric pressure are investigated experimentally. The experimental observations reveal that the array of tungsten pin electrodes successfully enhance the initial discharges maintained by the strong electrostatic field with stable and fast ignition, which enables us to sustain efficient rf induction plasmas at atmospheric pressure range.

DOI： 10.1585/pfr.1.006

Validity of Electron Temperature Measurement by Using Boltzmann Plot Method in Radio Frequency Inductive Discharge in the Atmospheric Pressure Range Reviewed International journal

OHNO Noriyasu, RAZZAK M. Abdur, UKAI Hiroshi, TAKAMURA Shuichi, UESUGI Yoshihiko

Plasma and Fusion Research ( 1 ) page： 28 - 28 2006

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：社団法人プラズマ・核融合学会

The validity of electron temperature measurement using the Boltzmann plot method was investigated in a radio frequency (rf) inductive discharge in the atmospheric pressure range. Since the Boltzmann plot method requires local thermal equilibrium (LTE), the parameter regions of electron temperature and electron density, in which the Boltzmann plot method is applicable, were analyzed in terms of a comparison of the spontaneous emission and collisional excitation to the excited states. It is observed that in our rf-inductive plasma near the atmospheric pressure range the Boltzmann plot method does not provide an exact measurement of electron temperature because of relatively low electron density, which does not satisfy the calculation criteria. An alternative method employing a combination of the Stark broadening measurement and the Saha-Boltzmann equation was demonstrated to more accurately determine the plasma parameters (electron temperature and electron density).

DOI： 10.1585/pfr.1.028

Design of a novel T-lclimmittance conversion circuit for dynamic and non-linear loads Reviewed International coauthorship International journal

Razzak M.A., Takamura S., Ohno N., Uesugi Y.

Proceedings of 4th International Conference on Electrical and Computer Engineering, ICECE 2006 page： 13 - 16 2006

Language：English Publishing type：Research paper (international conference proceedings) Publisher：Proceedings of 4th International Conference on Electrical and Computer Engineering, ICECE 2006

In recent years, the immittance conversion topology [1] has become attractive as a novel power conversion strategy because of its features that a constant voltage source is converted to a constant current source and vice versa. However, the design of an ideal immittance circuit in the high-power (∼kW) and high-frequency (∼MHz) range is practically very important, especially when apply to a dynamic and non-linear load such as induction plasma. In this article, the design and development of an ideal T-LCL immittance circuit is reported. The performance of the designed immittance circuit is analysed by using a time-varying inductive plasma load.

DOI： 10.1109/ICECE.2006.355278

Optimum generation of high heat flux toroidal plasmas by RF ohmic discharge Reviewed International journal

Masuda H., Kitahara H., Nagase M., Ohno N., Takamura S., Takagi M.

32nd EPS Conference on Plasma Physics 2005, EPS 2005, Held with the 8th International Workshop on Fast Ignition of Fusion Targets - Europhysics Conference Abstracts Vol. 3 page： 1946 - 1949 2005.12

Language：English Publishing type：Research paper (international conference proceedings) Publisher：32nd EPS Conference on Plasma Physics 2005, EPS 2005, Held with the 8th International Workshop on Fast Ignition of Fusion Targets - Europhysics Conference Abstracts

We have developed a new toroidal divertor plasma simulator, NAGDIS-T (NAGoya DIvertor plasma Simulator with Toroidal magnetic configuration). Plasma is generated by RF Joule discharge. In order to obtain high density plasmas relevant to divertor plasmas in fusion devices, we investigate the optimum condition of RF Joule discharge by varying gas pressure and driving frequency. The experimental result shows that the optimum condition strongly depends on these parameters. Copyright © (2005) by the European Physical Society (EPS).

High-Z Dust Generation on Tungsten Surfaces due to Synergetic Erosion of Deuterium/Helium Plasma Exposures Reviewed

西島大, 天野浩嗣, 大野哲靖, 吉田直亮, 高村秀一

プラズマ・核融合学会誌 = Journal of plasma and fusion research Vol. 81 ( 9 ) page： 703 - 707 2005.9

Language：English Publishing type：Research paper (scientific journal) Publisher：社団法人プラズマ・核融合学会

Low-energy and high-flux plasma exposures on tungsten surfaces result in blister/hole formation. Subsequent He plasma exposure at 2,000 K on the blister-rich surface forms a hole structure on the surface, including the blister surface, and some blisters collapse due to recrystallization and bubble formation on the blister skin. Grain ejections were observed after deuterium plasma exposure at 550 K on a W surface on which a hole structure had formed due to He pre-exposure at 1,600 K.

DOI： 10.1585/jspf.81.703

Efficient Radio Frequency Inductive Discharges in Near Atmospheric Pressure Using Immittance Conversion Topology Reviewed

Razzak M. Abdur, 高村秀一, 上杉喜彦, 大野哲靖

プラズマ・核融合学会誌 = Journal of plasma and fusion research Vol. 81 ( 3 ) page： 204 - 211 2005.3

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：社団法人プラズマ・核融合学会

A radio frequency (rf) inductive discharge in atmospheric pressure range requires high voltage in the initial startup phase and high power during the steady state sustainment phase. It is, therefore, necessary to inject high rf power into the plasma ensuring the maximum use of the power source, especially where the rf power is limited. In order to inject the maximum possible rf power into the plasma with a moderate rf power source of few kilowatts range, we employ the immittance conversion topology by converting a constant voltage source into a constant current source to generate efficient rf discharge by inductively coupled plasma (ICP) technique at a gas pressure with up to one atmosphere in argon. A novel T-LCL immittance circuit is designed for constant-current high-power operation, which is practically very important in the high-frequency range, to provide high effective rf power to the plasma. The immittance conversion system combines the static induction transistor (SIT)-based radio frequency (rf) high-power inverter circuit and the immittance conversion elements including the rf induction coil. The basic properties of the immittance circuit are studied by numerical analysis and verified the results by experimental measurements with the inductive plasma as a load at a relatively high rf power of about 4 kW. The performances of the immittance circuit are also evaluated and compared with that of the conventional series resonance circuit in high-pressure induction plasma generation. The experimental results reveal that the immittance conversion circuit confirms injecting higher effective rf power into the plasma as much as three times than that of the series resonance circuit under the same operating conditions and same dc supply voltage to the inverter, thereby enhancing the plasma heating efficiency to generate efficient rf inductive discharges.

DOI： 10.1585/jspf.81.204

Characteristic changes of deuterium retention on tungsten surfaces due to low-energy helium plasma pre-exposure Reviewed

Nishijima D, Sugimoto T, Iwakiri H, Ye MY, Ohno N, Yoshida N, Takamura S

JOURNAL OF NUCLEAR MATERIALS Vol. 337 ( 1-3 ) page： 927 - 931 2005.3

Hydrogen Blister Formation on Cold-Worked Tungsten with Layered Structure Reviewed

D.Nishijima, T.Sugimoto, M.Ye, N.Ohno, S.Takamura

Jpn. J. Appl. Phys. Vol. 44 ( 1A ) page： 380-382 2005

Overview of JT-60U progress towards steady-state advanced tokamak Reviewed

S.Ide, N.Ohno, JT-60U Team

Nuclear Fusion Vol. 45 page： S48-S62 2005

Micron-Bubble Formation on Polycrystal Tungsten due to Low-Energy and high-Flux Helium Plasma Exposure Reviewed

D.Nishijima, M.Miyamoto, H.Iwakiri, M.Ye, N.Ohno, K.Tokunaga, N.Yoshida, S.Takamura

Nuclear Fusion Vol. 46 page： 561-564 2005

Further Roughing of Tungsten Surface due to Transient Heat Load by Laser Irradiation during Helium Plasma Exposure Reviewed

S.Kajita, D.Nishijima, N.Ohno, S.Takamura

J. Plasma Fusion Res. Vol. 81 page： 745-746 2005

High-Z Dust Generation on Tungsten Surface due to Synergetic Erosion of Deuterium/Helium Plasma Exposure Reviewed

D.Nishijima, K.Amano, N.Ohno, N.Yoshida, S.Takamura

J. Plasma Fusion Res. Vol. 81 page： 703-707 2005

Suppression of Blister Formation and Deuterium Retention on Tungsten Surface due to Mechanical Polishing and Helium Pre-exposure Reviewed

D.Nishijima, H.Iwakiri, K.Amano, M.Y.Ye, N.Ohno, K.Tokunaga, N.Yoshida, S.Takamura

Nucl. Fusion Vol. 45 page： 669-674 2005

Efficient Radio Frequency Inductive Discharge in Hear Atmospheric Pressure Using Imittance Conversion Topology Reviewed

M.A.Razzak, S.Takamura, Y.Uesugi, N.Ohno

J. Plasma Fusion Res. Vol. 81 ( 3 ) page： 204-211 2005

Characterstic changes of deuterium rentention on tungsten surfaces due to low-energy helium plasma pre-exposure Reviewed

D.Nishijima, T.Sugimoto, H.Iwakiri, M.Y.Ye, N.Ohno, N.Yoshida, S.Takamura

Journal of Nuclear Materials Vol. 337-339 page： 927-931 2005

Carbon dust formation from re-deposited layers in high-density hydrogen/helium plasmas in the NAGDIS-II device Reviewed

N.Ohno, Y.Kobayashi, T.Sugimoto, S.Takamura

Journal of Nuclear Materials Vol. 337-339 page： 35-39 2005

Neutral helium line emission for edge plasma conditions Reviewed

F.B.Rosmej, R.Stamm, S.Fritzsche, H.Capes, M.Koubiti, Y.Marandet, V.S.Lisitsa, N.Ohno, S.Takamura, D.Nishijima

Journal of Nuclear Materials Vol. 337-339 page： 1101-1105 2005

Formation mechanism of bubbles and holes on tungsten surface with low-energy and high-flux helium plasma irradiation in NAGDIS-II Reviewed

Dai. Nishijima, M.Y.Ye, N.Ohno, S.Takamura

J. Nucl. Mater. Vol. 329-333 page： 1029-1033 2005

Transition from electrostatic-to-electromagnetic mode in a radio-frequency Ar inductively coupled plasma in atmospheric pressure Reviewed International journal

Razzak MA, Kondo K, Uesugi Y, Ohno N, Takamura S

JOURNAL OF APPLIED PHYSICS Vol. 95 ( 2 ) page： 427 - 433 2004.1

Proposal of Modeified Child-Langmuir Formula Describing Space-Charge Limited Current in Plasma Reviewed

Y.Hagino, N.Ohno, S.Takamura

Contrib. Plasma Phys. Vol. 44 ( 1-3 ) page： 144-149 2004

Visualization of Intermittent Blobby Plasma Transport in Attached and Detached Plasmas of the NAGDIS-II Reviewed

N.Ohno, K.Furuta, S.Takamura

J. Plasma Fusion Res. Vol. 80 ( 4 ) page： 275-276 2004

Moving-Surface Plasma-Facing Components for Particle Control in Steady State Magnetic Fusion Devices Reviewed

Y.Hirooka, H.Fukushima, N.Ohno, S.Takamura

Fusion Science and Technology Vol. 45 page： 60-64 2004

Reconstruction of Velocity Distribution of density Bursts by Wavelet Analysis in the Linear Divertor Simulator NAGDIS-II Reviewed

N.Ohno, V.P.Budaev, K.Furuta, H.Miyoshi, S.Takamura

Contrib. Plasma Phys. Vol. 44 ( 1-3 ) page： 222-227 2004

Space-Charge Limited Current from Plasma-Facing Material Surface Reviewed

S.Takamura, N.Ohno, M.Y.Ye, T.Kuwabara

Contrib. Plasma Phys. Vol. 44 ( 1-3 ) page： 126-137 2004

Proposal of modified Child-Langmuir formula describing space-charge limited current in plasma Reviewed International journal

Hagino Y, Ohno N, Takamura S

CONTRIBUTIONS TO PLASMA PHYSICS Vol. 44 ( 1-3 ) page： 144 - 149 2004

Proof-of-principle experiments on the concept of moving-surface plasma-facing components - Hydrogen recycling over a titanium-gettered rotating drum Reviewed International journal

Hirooka Y., Fukushima H., Ohno N., Takamura S.

Fusion Engineering and Design Vol. 65 ( 3 SPEC. ) page： 413 - 421 2003.4

Language：English Publishing type：Research paper (scientific journal) Publisher：Fusion Engineering and Design

In the magnetic fusion community much attention has recently been directed to particle control in the existing confinement experiments, as it is recognized that the core plasma performance can directly be affected by the edge conditions. However, it is still true that there is no clear strategy to cope with the needs for steady-state reactor operation. That is that, due to the saturation nature, wall conditioning such as boronization is not applicable for fuel and impurity particles control in steady-state devices, requiring a start from enabling concepts development. As a possible solution, the concept of moving-surface plasma-facing components (MS-PFCs) was proposed in our previous work and in the present work proof-of-principle experiments have been conducted. In this concept, the plasma-facing surface is mechanically circulated out-of-pile for regeneration of particle capturing capabilities by coating getter films on it. A prototypical MS-PFC test unit has been constructed for these proof-of-principle experiments, employing a rotating copper drum as the moving surface and titanium as the getter material. It has been indicated that, from Hα light intensity data taken in front of the rotating target, relative to no getter cases, approximately 6% reduced hydrogen recycling has been achieved at steady state. In support of these data, a first-order particle balance model predicts a 7% reduction in hydrogen recycling. © 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0920-3796(03)00011-5

Ion temperature measurement using an ion sensitive probe in the LHD divertor plasma Reviewed International journal

Ezumi N., Masuzaki S., Ohno N., Uesugi Y., Takamura S.

Journal of Nuclear Materials Vol. 313-316 ( SUPPL. ) page： 696 - 700 2003.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Nuclear Materials

The first reliable measurement of ion temperature in the divertor plasma of the Large Helical Device has been done by using an ion sensitive probe. The satisfactory current-voltage characteristics of the ion collector for evaluating the ion temperature were obtained at the outer part of the divertor leg. Furthermore, simultaneous ion and electron temperature measurements were successfully done in this part. The results show that the ion temperature is higher than the electron temperature in the part. There is a possibility that the profiles of the evaluated ion temperature which shows relatively higher than the electron temperature at the outside of divertor leg are qualitatively explained by particle's orbits around the edge and divertor region. © 2003 Elsevier Science B.V. All rights reserved.

DOI： 10.1016/S0022-3115(02)01364-8

Experimental evaluation of space charge limited emission current from tungsten surface in high density helium plasma Reviewed International journal

Hagino Y., Ohno N., Takamura S., Ye M.

Journal of Nuclear Materials Vol. 313-316 ( SUPPL. ) page： 675 - 678 2003.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Nuclear Materials

The experimental evaluation of space charge limited emission current from tungsten surface in high density helium plasma was done. It was found that the space charge limited current from the tungsten target plate saturated with an increase in sheath voltage. The space charge effect was predicted on the basis of boundary conditions of zero electric field on the material surface.

DOI： 10.1016/S0022-3115(02)01381-8

25aB11P Blister Formation on Low-Temperature Refractory Metal Surface under Low Energy and High Flux Hydrogen Plasma Irradiation Reviewed

非接触再結合プラズマ中の揺動特性 Reviewed

大野哲靖、田中直行、高村秀一

Vol. 7 ( 10 ) page： 1093-1101 2003

Transition from Electrostatic to Electromagnetic Mode in a Radio Frequency Ar Induction Plasma in Atmospheric Pressure Reviewed

M.A.Razzak, K.Kondo, Y.Uesugi, N.Ohno, S.Takamura

J. Appl. Phys. Vol. 95 ( 2 ) page： 427-433 2003

Intermittent structures in the high field side boundary of the HYBTOK-II tokamak Reviewed

V.P.Budaev, S.Takamura, Y.Kikuchi, Y.Uesugi, N.Ohno

Czechoslovak Journal of Phys Vol. 53 ( 10 ) page： 863-868 2003

Formation and dynamics of very deep negative potential well in the small tokamak device CSTN-IV Reviewed

H.Kojima, Y.Fukuzawa, T.Manabe, S.Takamura, T.Okada, N.Ohno

Czechoslovak Journal of Phys. Vol. 53 ( 10 ) page： 895-902 2003

プラズマと接する固体表面からの空間電荷制限放出電流 Reviewed

高村秀一、大野哲靖

放電研究 Vol. 46 ( 3 ) page： 2-22 2003

Proof of principle experiments on the concept of moving-surface plasma-facing components-hydrogen recycling over a titanium-gettered ratating drum Reviewed

Y.Hirooka, H.Fukushima, N.Ohno, S.Takamura

Fusion Engineering and Design Vol. 6 page： 413-421 2003

Blister formation on tungsten surface under low energy and high flux hydrogen plasma irradiation in NAGDIS-I Reviewed

M.Y.Ye, H.Kanehara, S.Fukuta, N.Ohno, S.Takamura

Journal of Nuclear Materials Vol. 313-316 page： 72-76 2003

Incident ion energy dependence of bubble formation on tungsten surface with low energy and high flux helium plasma irradiation Reviewed

D.Nishijima, M.Y.Ye, N.Ohno, S.Takamura

Journal of Nuclear Materials Vol. 313-316 page： 97-101 2003

Experimental evaluation of space charge limited emission current from tungstn surface in high density helium plasma Reviewed

Y.Hagino, N.Ohno, S.Takamura, M.Y.Ye

Journal of Nuclear Materials Vol. 313-316 page： 675-678 2003

Ion temperature measurement using an ion sensitie probe in the LHD divertor Reviewed

N.Ezumi, S.Masuzaki, N.Ohno, Y.Uesugi, S.Takamura, LHD Experimental Group

Journal of Nuclear Materials Vol. 313-316 page： 696-700 2003

High-quality video streaming system for plasma diagnostics using super SINET Reviewed

M.Emoto, K.Watanabe, S.Masuzaki, N.Ohno, H.Okade

Rev. Sci. Instrum. Vol. 74 page： 1766 2003

Self-consistent dusty sheaths in plasmas with two-temperature electrons Reviewed

Yu.I.Chutov, O.Kravchenko, A.Pshenychnyj, R.Smirnov, K.Asano, N.Ohno, S.Takamura, Y.Tomita

Physics of Plasmas Vol. 10 ( 2 ) page： 546-552 2003

Fluctuation Characteristics in Detached Recombining Plasmas

N.Ohno, N.Tanaka, S. Takamura, V.Budaev

AIP Conference Proceedings Vol. 669 page： 240-243 2003

Edge Plasma Turbulence in Fusion Devices: Bursty Behavior and Fractal Properties

V.P.Budaev, S.Takamura, N.Ohno, A.Komori, S.Masuzaki, G.S.Kirnev, S.A.Grashin

30th EPS Conference on Contr. Fusion and Plasma Phys., St. Petersburg, 7-11 July 2003 ECA Vol. 27A page： 3.174 2003

Intermittent Structures in the High Field Side Boundary of the HYBTOK-II Tokamak

V.P.Budaev, S.Takamura, Y.Kikuchi, Y.Uesugi, N.Ohno

30th EPS Conference on Contr. Fusion and Plasma Phys., St. Petersburg, 7-11 July 2003 ECA Vol. 27A page： 3.173 2003

Surface Morphology of Tungsten Irradiated by Low-Energy and High-Flux Steady State Helium Plasma

D.Nishijima, M.Y.Ye, N.Ohno, S.Takamura

30th EPS Conference on Contr. Fusion and Plasma Phys., St.Petersburg, 7-11 July 2003 ECA Vol. 27-A page： 2.163 2003

Structural Dynamics of Deep Negative Potential Well Formation in Small Tokamak Device CSTN-IV

H.Kojima, Y.Fukuzawa, T.Manabe, N.Ohno, S.Takamura

30th EPS Conference on Contr. Fusion and Plasma Phys., St.Petersburg, 7-11 July 2003 ECA Vol. 27A page： 2.130 2003

Experimental Observation and Statistical Analysis of Density Bursts in the Linear Divertor Simulator NAGDIS-II

N.Ohno, K.Furuta, H.Miyoshi, S.Takamura, V.P.Budaev

30th EPS Conference on Contr. Fusion and Plasma Phys., St. Petersburg, 7-11 July 2003 ECA Vol. 27A page： 2.154 2003

Influence of the Ion Beam on the Behavior of Dust Particles Trapped in an Ion Sheath

T.Murakami, M.Sawai, T.Misawa, N.Ohno, S.Takamura

AIP Conference Proceedings Vol. 669 page： 101-104 2003

Sound Wave Propagation in Gases at Low Pressure

T.Tonogaki, N.Ohno, S.Takamura, A.Tsushima

AIP Conference Proceedings Vol. 669 page： 113-116 2003

25aA28P Statistical analysis of fluctuation property in edge plasmas of the LHD Reviewed

MIYOSHI Hideaki, TAKAMURA Shuichi, OHNO Noriyasu, MASUZAKI Suguru, KOMORI Akio, Budaev V.P.

( 20 ) 2003

25aB37P Construction of High Heat Flux Toroidal Divertor Plasma Simulator Reviewed

Sora Shigeki, Kitahara Hiroyoshi, Ohno Noriyasu, Uesugi Yoshihiko, Takamura Shuichi

( 20 ) 2003

SUGIMOTO Takanori, OHNO Noriyasu, TAKAMURA Shuichi

( 20 ) 2003

26aA40P Formation of Deep Potential Well by Electrode Biasing in Tokamak Device Reviewed

FUKUZAWA Yuma, KOJIMA Hiroki, OKADA Takahiro, OHNO Noriyasu, TAKAMURA Shuichi, IGUCHI Tetsuo

( 20 ) 2003

28aA17P Influence of Energetic Electron Components on Unstable Oscillation of Dust Particles Trapped in Plasma-Sheath Boundary Reviewed

KOBAYASHI Atsuhiro, IMASATO Kae, OHNO Noriyasu, TAKAMURA Shuichi

( 20 ) 2003

27pB22P Fluctuation Analysis in Detached and Attached Plasmas Reviewed

Furuta K., Ohno N., Takamura S.

( 20 ) 2003

Generation and characteristics of a detached recombining plasma and its dynamic behaviour-a bridge between fusion plasmas and low-temperature ionized gases Reviewed International journal

Takamura S, Ohno N, Nishijima D, Uesugi Y

PLASMA SOURCES SCIENCE & TECHNOLOGY Vol. 11 ( 3A ) page： A42 - A48 2002.8

Characteristics of detached plasmas associated with electron-ion and molecular assisted recombinations in NAGDIS-II Reviewed International coauthorship International journal

Nishijima D., Wenzel U., Ohsumi K., Ohno N., Uesugi Y., Takamura S.

Plasma Physics and Controlled Fusion Vol. 44 ( 5 ) page： 597 - 610 2002.5

Language：English Publishing type：Research paper (scientific journal) Publisher：Plasma Physics and Controlled Fusion

Recombination in a helium and helium-hydrogen plasma was experimentally investigated in the linear divertor simulator NAGDIS-II. To identify the physical mechanisms, electron-ion recombination (EIR) and molecular assisted recombination (MAR), the plasma parameters in the recombining region have been measured. We used spectroscopic techniques on the basis of continuum emission and line emission from highly excited levels due to EIR and Langmuir probes. The dependence of the plasma parameters on the neutral pressure in a pure helium plasma and in a helium-hydrogen mixture shows clearly that recombination is caused by different processes in the two cases. In a pure helium plasma a roll-over and a following decrease of the electron density as well as a monotonic decrease of the electron temperature down to 0.1 eV were observed when increasing the helium pressure. Here EIR is the recombination mechanism. Conversely, when hydrogen is added to the helium plasma, the electron density decreases monotonically while the central electron temperature remains above 1 eV. This particular behaviour in the helium-hydrogen plasma can only be explained by the dominant action of MAR.

DOI： 10.1088/0741-3335/44/5/307

28pB09 Experimental Evaluation of Space-Charge Limited Emission Current from Tungsten Surface in High Density Helium Plasma Reviewed

Response to "comment on 'dynamic behaviors of dust particles in the plasma-sheath boundary'" [Phys. Plasmas 9, 1057 (2002)] Reviewed International journal

Takamura S., Ohno N., Misawa T., Nunomura S.

Physics of Plasmas Vol. 9 ( 3 ) 2002.3

Proposal of Flexible Atomic and Molecular Process Management for Monte Carlo Impurity Transport Code Based on Object Oriented Method Reviewed

K.Asano, N.Ohno, S.Takamura

Contrib. Plasma Physics Vol. 42 page： 157-162 2002

Generation and characteristics of detached recombining plasma and its dynamic behaviour - a bridge between fusion plasmas and low-temperature ionized gases Reviewed

S.Takamura, N.Ohno, D.Nishijima, Y.Uesugi

Plasma Sources Sci. Technol. Vol. 11 ( 3A ) page： A42-A4 2002

Response to Comment on "Dynamic Behaviours of Dust Particles in the Plasma Sheath Boundary" Reviewed

S.Takamura, N.Ohno, T.Misawa, S.Nunomura

Physics of Plasmas Vol. 9 page： 1060-1061 2002

Characteristics of Detached Plasmas Associated with Electron-Ion and Molecular Assisted Recombination in NAGDIS-II Reviewed

D.Nishijima, U.Wenzel, K.Ohsumi, N.Ohno, Y.Uesugi, S.Takamura

Plasma Physics Controlled Fusion Vol. 44 page： 597-610 2002

Parametric Excitation of a Dust Particle Trapped in a Plasma-Sheath Boundary Reviewed

N.Ohno, M.Sawai, T.Misawa, K.Asano, S.Takamura

Physica Scripta Vol. T98 page： 81-86 2002

Analysics of Detached Recombining Plasmas by Collisional-Radiative Model with Energetic Electron Component Reviewed

N.Ohno, M.Motoyama, S.Takamura

Contrib. Plasma Physics Vol. 42 page： 419-424 2002

Heat Pulse in a Simulated Divertor Plasmas

Y.Uesugi, S.Takamura, K.Ohsumi, N.Ohno, D.Nishijima

29th EPS Conference on Contr. Fusion and Plasma Phys., Montroux, Switzerland, 17-21 June 2002 ECA Vol. 26B page： 1.087 2002

26aB13P Tungsten Surface Irradiated by Low Energy and High Flux Helium Plasma Reviewed

Nishijima D., Ye M.Y., Ohno N., Takamura S.

( 19 ) 2002

Analysis of detached recombining plasmas by collisional-radiative model with energetic electron component Reviewed International journal

Ohno N, Motoyama M, Takamura S

CONTRIBUTIONS TO PLASMA PHYSICS Vol. 42 ( 2-4 ) page： 419 - 424 2002

HAGINO Yoshiharu, YE Minyou, OHNO Noriyasu, TAKAMURA Shuichi

( 19 ) 2002

26pA07 Thermoelectron Emission from a Small Electrode heated with Plasma Heat Flux in AC Tokamak Discharge Reviewed

MANABE Toshiharu, KOJIMA Hiroki, FUKUZAWA Yuma, OHNO Noriyasu, TAKAMURA Shuichi

( 19 ) 2002

26aB18P Proof-of-principle experiments on the concept of particle control by moving-surface plasma-facing components Reviewed

HIROOKA Yoshi, FUKUSHIMA Houju, OHNO Noriyasu, TAKAMURA Shuichi

( 19 ) 2002

Simulation Experiments on Erosion and Redeposition of High - Z Materials in a Linear Plasma Device Reviewed

OHNO Noriyasu, TAKAMURA Shuichi

Journal of plasma and fusion research Vol. 77 ( 9 ) page： 864 - 868 2001.9

Authorship：Lead author Language：Japanese Publishing type：Research paper (scientific journal)

Erosion and redeposition processes of molybdenum, a high-Z material, were investigated in the linear plasma device TPD-I. Comparison between the experimental results and numerical analysis with a 3D Monte Carlo simulation code indicated that the observed erosion profile could be explained by taking account of the effect of prompt redeposition of high-Z material.

Static and dynamic behaviour of plasma detachment in the divertor simulator experiment NAGDIS-II Reviewed International coauthorship International journal

Ohno N., Nishijima D., Takamura S., Uesugi Y., Motoyama M., Hattori N., Arakawa H., Ezumi N., Krasheninnikov S., Pigarov A., Wenzel U.

Nuclear Fusion Vol. 41 ( 8 ) page： 1055 - 1065 2001.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Nuclear Fusion

A comprehensive investigation has been performed of the static and dynamic behaviour of detached recombining plasmas in the linear divertor plasma simulator NAGDIS-II. For stationary plasma detachment, the transition from electron ion recombination (EIR) to molecular activated recombination (MAR) has been observed by injecting hydrogen gas into high density helium plasmas. The particle loss rate due to MAR is found to be comparable to that of EIR. Experiments have also been performed by the injection of a plasma heat pulse produced by RF heating into the detached helium plasma to demonstrate the dynamic behaviour of volumetric plasma recombination. Negative spikes in the Balmer series line emission were observed and found to be similar to the so called negative ELM observed in tokamak divertors. Observed Balmer spectra were analysed in detail using the collisional-radiative model. A rapid increase of the ion flux to the target plate was observed associated with the re-ionization of the highly excited atoms generated by EIR.

DOI： 10.1088/0029-5515/41/8/309

Evidence for the importance of radial transport in plasma detachment in the Nagoya University Divertor Simulator (NAGDIS-II) Reviewed International journal

Hollmann E., Whyte D., Nishijima D., Ohno N., Uesugi Y., Ezumi N.

Physics of Plasmas Vol. 8 ( 7 ) page： 3314 - 3320 2001.7

Language：English Publishing type：Research paper (scientific journal) Publisher：Physics of Plasmas

Measurements of ion and electron temperatures have been performed in detaching helium -hydrogen plasmas in a linear divertor simulator experiment using spectroscopy, a Langmuir probe, and an omegatron mass spectrometer. Detachment in these plasmas is characterized by a significant (≈20×) reduction in the central plasma flux at the target plate as the target region neutral pressure is increased from 2 to 12 mTorr. The data indicate that partially detached gas-target plasmas consist of a hot (Te≈5 eV) core region along the axis of the plasma column, surrounded by a cold (Te ≈0.1 eV) halo region of recombining plasma. At Te = 5 eV, plasma recombination is negligible compared with ionization; these experiments therefore provide evidence that detachment is primarily caused by radial transport and by a gradual drop in the ionization source as the temperature of the core region drops below 5 eV. © 2001 American Institute of Physics.

DOI： 10.1063/1.1372664

Dynamic behavior of detached recombining plasmas during ELM-like plasma heat pulses in the divertor plasma simulator NAGDIS-II Reviewed International journal

Uesugi Y, Hattori N, Nishijima D, Ohno N, Takamura S

JOURNAL OF NUCLEAR MATERIALS Vol. 290 page： 1134 - 1137 2001.3

Evaluation of electron temperature in detached recombining plasmas Reviewed International coauthorship International journal

Nishijima D., Wenzel U., Motoyama M., Ohno N., Takamura S., Krasheninnikov S.

Journal of Nuclear Materials Vol. 290-293 page： 688 - 691 2001.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Nuclear Materials

Detailed spectroscopic measurements have been carried out in the linear divertor plasma simulator, NAGDIS-II in order to acquire the accurate evaluation of the electron temperature, which leads to a deeper understanding of the characteristics of detached recombining plasmas. Electron temperature in the detached recombining plasmas was evaluated by two different spectroscopic methods, using continuum emission and a series of line emission from highly excited levels, giving different electron temperatures. The reasons are discussed based on the effects of energetic electrons.

DOI： 10.1016/S0022-3115(00)00528-6

Experimental observation of vertically polarized transverse dust-lattice wave propagating in a one-dimensional strongly coupled dust chain Reviewed International journal

Misawa T., Ohno N., Asano K., Sawai M., Takamura S., Kaw P.K.

Physical Review Letters Vol. 86 ( 7 ) page： 1219 - 1222 2001.2

Language：English Publishing type：Research paper (scientific journal) Publisher：Physical Review Letters

The existence of transverse dust-lattice wave (T-DLW) propagating in a one-dimensional strongly coupled dust chain levitated in dc argon plasma at low gas pressure was assessed. Both parts of the complex wave number were measured in the experiments. The real part showed that the T-DLW propagation as a backward wave.

DOI： 10.1103/PhysRevLett.86.1219

27aA01 [招待講演]非接触プラズマにおける再結合過程とその動的応答(プラズマ基礎・応用) Reviewed

Experimental Observation of Vertically Polarized Transverse Dust Lattice Wve Propagating in a One Dimensional Strongly Coupled Dust Chain Reviewed

T.Misawa, N.Ohno, K.Asano, M.Sawai, S.Takamura, P.K.Kaw

Physcal Review Letters Vol. 86 ( 7 ) page： 1219-1222 2001

Influence of Plasma Resistance and Fluctuation on Probe Characeteristics in Detached Recombining Plasmas Reviewed

N.Ohno, N.Tanaka, N.Ezumi, D.Nishijima, S.Takamura

Contib. Plasma Physics Vol. 41 page： 473-480 2001

Static and Dynamic Behaviors of Detached Plasma in Divertor Simulator NAGDIS-II Reviewed

S.Takamura, N.Ohno, Y.Uesugi, D.Nishijima, K.Ohsumi, M.Motoyama, N.Hattori, N.Ezumi, S.Krasheninnikov, A.Pigarov, U.Wenzel

Journal of Plasma and Fusion Research SERIES Vol. 4 page： 138-145 2001

Dynamic Behaviors of Dust Particles in the Plasma-Sheath Boundary Reviewed

S.Takamura, T.Misawa, N.Ohno, S.Nunomura, M.Sawai, K.Asano, P.K.Kaw

Physics of Plasmas Vol. 8 ( 5 ) page： 1886-1892 2001

プラズマと接する固体表面からの空間電荷制限電流 Reviewed

桑原竜弥、大野哲靖、高村秀一、叶民友

Vol. 77 ( 5 ) page： 464-475 2001

Evidence for the Importance of Radial Transport in Plasma Detacment in the Nagoya University Divertor Simulator(NAGDIS-II) Reviewed

E.M.Hollmann, D.G.Whyte, D.Nishijima, N.Ohno, Y.Uesugi, N.Ezumi

Physics of Plasmas Vol. 8 ( 7 ) page： 3314-3320 2001

*Static and Dynamic Behavior of Plasma Detachment in the Divertor Simulator Experiment NAGDIS-II Reviewed

N.Ohno, D.Nishijima, S.Takamura, Y.Uesugi, M.Motoyama, N.Hattori, H.Arakawa, N.Ezumi, S.Krasheninnikov, A.Pigarov, U.Wenzel

Nuclear Fusion Vol. 41 ( 8 ) page： 1055-1065 2001

Evaluation of Electron Teperature in Detached Recombining Plasma Reviewed

D.Nishijima, U.Wenzel, M.Motoyama, N.Ohno, S.I.Krasheninnikov, S.Takamura

Journal of Nuclear Materials Vol. 290-293 page： 688-691 2001

小特集「プラズマ対向面での損耗・再堆積研究の進展」3.直線型プラズマ装置を用いた高融点金属材料の損耗・再堆積モデル実験

大野哲靖、高村秀一

プラズマ・核融合学会誌 Vol. 77 ( 9 ) page： 864-868 2001

Dynamic Response of Detached Recombining Plasmas to ELM-Like Plasma Heat Pulse Produced by RF Heating

K.Ohsumi, D.Nishijima, N.Ohno, Y.Uesugi, S.Takamura

Proc. of XXV International Conference on Phenomena in Ionized Gases, Nagoya, Japan page： 195-196 2001

Influence of Supra-Thermal Electrons on Propagation of Transverse Dust Lattice Wave

T.Misawa, K.Asano, M.Sawai, N.Ohno, S.Takamura

Proc. of XXV International Conference on Phenomena in Ionized Gases, Nagoya, Japan page： 65-66 2001

MD Particle Simulation on Dust Lattice Wave

K.Asano, T.Misawa, N.Ohno, S.Takamura, S.Vladimirov

Proc. of XXV International Conference on Phenomena in Ionized Gases, Nagoya, Japan page： 61-62 2001

Fluctuations in Detached Recombining Plasmas

N.Tanaka, N.Ohno, S.Takamura

Proc. of XXV International Conference on Phenomena in Ionized Gases, Nagoya, Japan page： 345-346 2001

Modifications of Tungsten Surface under Low Ionic Energy and High Flux Plasma Irradiation

K.Moriguchi, S.Fukuta, M.Y.Ye, N.Ohno, S.Takamura

Proc. of XXV International Conference on Phenomena in Ionized Gases, Nagoya, Japan page： 83-84 2001

大野哲靖, 高村秀一, 上杉喜彦, 西島大輔, 大住光一, 田中直行, 嶋崎弘志

プラズマ・核融合学会年会予稿集 ( 18 ) 2001

30pA17P Ion Temperature Measurement using an Ion Sensitive Probe in PSI-2 Reviewed

EZUMI Naomichi, OHNO Noriyasu, TAKAMURA Shuichi, KATSUMATA Itsuo, MASUZAKI Suguru, Kiss'ovski Zh., Bohmeyer W., Fussmann G.

( 18 ) 2001

29pA20P Proof of Principle Experiment on Particle Control with Moving-Belt Plasma Facing Component Reviewed

Fukushima Hoju, Hirooka Yoshihiko, Ohno Noriyasu, Takamura Shyuichi

( 18 ) 2001

28aB15P Dynamic Response of Detached Recombining Plasmas to ELM-Like Heat Pulse Produced by Whistler Wave Reviewed

OSUMI Koichi, NISHIJIMA Daisuke, OHNO Noriyasu, UESUGI Yoshihiko, TAKAMURA Shuichi

( 18 ) 2001

27pA12P Measurements of Fluctuations in Detached Recombining Plasmas (2) Reviewed

Tanaka N., Ohno N., Takagi M., Takamura S., Budaev V.

( 18 ) 2001

27pA11P Analysis of dynamic behaviors of detached plasmas by time-dependent collisional radiative code and nuid code Reviewed

SHIMAZAKI Hiroshi, OHNO Noriyasu, TAKAMURA Shuichi

( 18 ) 2001

Influence of plasma resistance and fluctuation on probe characteristics in detached recombining plasmas Reviewed International journal

Ohno N., Tanaka N., Ezumi N., Nishijima D., Takamura S.

Contributions to Plasma Physics Vol. 41 ( 5 ) page： 473 - 480 2001

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：Contributions to Plasma Physics

In order to find the causes of the strong anomaly of current-voltage characteristics of Langmuir probe observed in detached recombining plasmas in a linear divertor plasma simulator, NAGDIS-II, we have investigated plasma resistance along a magnetic field and potential fluctuations in the detached recombining plasmas. Simple calculation on the ratio between the plasma length, at which plasma resistance and resistance of ion sheath formed around a probe tip become equal, and an electron collection length indicates that the evaluation of electron temperature Te becomes inaccurate at Te of less than 0.6 eV when plasma density and neutral pressure are 1.0 × 1018 m-3 and 10 mtorr, respectively. The potential fluctuation in detached recombining plasmas was found to be so large compared to Te/e, which can also modify the probe characteristics.

DOI： 10.1002/1521-3986(200109)41:5<473::AID-CTPP473>3.0.CO;2-8

Dynamic Response of Dust Particles trapped in a Plasma-Sheath Boundary to External Forced Oscillation (2) Reviewed

The Plasma Boudary of Magnetic Fusion Devices Reviewed

Vol. 76 ( 10 ) 2000.10

Detached Recombining Plasmas in relation to Volumetric Hydrogen Recycle in Hydrogen Recycling at Plasma Facing Materials, ed. by C.H.Wu

S.Takamura, N.Ohno, N.Ezumi, D.Nishijima, S.I.Krasheninnikov, A.Yu. Pigarov

NATO Science Series, II. Mathematics, Physics and Chemistry, Vol. 1, Kluwer Academic Publishers Vol. 1 page： 59-66 2000

Fundamental Processes of Plasma Heat Flow through Sheaths to Material Surfaces in Recent Research Development in Plasmas Vol.1-2000

S.Takamura, M.Y.Ye, N.Ohno, Y.Uesugi

Transworld Research Network, 2000, pp.41-64 page： 41-64 2000

Fundamental Process of Plasma Heat Flow through Sheaths to Material Surfaces in Recent Research Development in Plasmas Reviewed

S.Takamura, M.Y.Ye, N.Ohno, Y.Uesugi

Transworld Research Network page： 41-64 2000

Dynamic Behavior of Detached Recombining Plasmas during ELM-like Plasma Heat Pulse in the Diverotr Plasma Simulator NAGDIS-II Reviewed

Y.Uesugi, N.Hattori, D.Nishijima, N.Ohno, S.Takamura

Journal of Nuclear Materials Vol. 290-293 page： 1134-1137 2000

Effects of Condensible Impurities on the Erosion Behavior of the Plasma-Facing Materials Reviewed

N.Ohno, S.Uno, Y.Hirooka, S.Takamura

Journal of Nuclear Materials Vol. 290-293 page： 299-302 2000

低ガス圧プラズマにおけるクーロン結晶の生成と浮遊位置制御 Reviewed

三沢達也、布村正太、浅野和仁、大野哲靖、高村秀一

電気学会論文誌A Vol. 120-A ( 2 ) page： 180-185 2000

Modifications of Tungsten Surface Irradiated by Low Energy and High Flux Helium Plasma Reviewed

M.Y.Ye, S.Fukuta, N.Ohno, S.Takamura, K.Tokunaga, N.Yoshida

Journal of Plasma and Fusion Research SERIES Vol. 3 page： 265-269 2000

2-D PIC Simulation on Space-Charge Limited Emission Current from Plasma-Facing Components Reviewed

K.Asano, N.Ohno, M.Y.Ye, S.Fukuta, S.Takamura

Contib. Plasma Physics Vol. 40 page： 478-483 2000

Dynamic Behavior of Detached Recombining Plasmas for Plasma Heat Pulse in the Diverotr Simulator NAGDIS-II Reviewed

N.Ohno, D.Nishijima, M.Motoyama, N.Hattori, Y.Uesugi, S.Takamura, U.Wenzel

Journal of Plasma and Fusion Research SERIES Vol. 3 page： 202-205 2000

Application of Strongly Ionized AC Tokamak Plasma for Synthesis of TiN Thin Films Reviewed

M.Y.Ye, O.Matsuda, N.Ohno, Y.Uesugi, M.Takagi, S.Takamura

Vacuum Vol. 59 page： 55-62 2000

Observation of Transverse Dust Lattice Wave Excited by Unstable Vertical Oscillations of Dust Particles in an Ion Sheath with Low Gas Pressure Reviewed

T.Misawa, S.Nunomura, N.Ohno, S.Takamura

Japan Journal of Applied Physics Vol. 39 page： L511-L553 2000

Detached Recombining Plasmas in relation to Volumetric Hydrogen Recycle Reviewed

S.Takamura, N.Ohno, N.Ezumi, D.Nishijima, S.I.Krasheninnikov, A.Yu.Pigarov

Hydrogen Recycling at Plasma Facing Materials, ed. by Ch.H.Wu, NATO Science Series, II. Mathematics, Physics and Chemistry, Kluwer Academic Pubilishers Vol. 1 page： 59-66 2000

Dynamic Behaviors of Dust Particles in the Plasma-Sheath Boundary

S.Takamura, T.Misawa, N.Ohno, S.Nunomura, M.Sawai, K.Asano, P.K.Kaw

42nd Annual Meeting of the Division of Plasma Physics of the American Physical Society, combined with ICPP2000, Quebec, Canada Vol. 1 2000

Recombination Plasmas in the ASDEX Upgrade Divertor and the Divertor Simulator NAGDIS-II

U.Wenzel, R.Pugno, K.Schmidtmann, N.Hattori, D.Nishijima, N.Ohno, S.Takamura, Y.Uesugi

Proc. of 27th EPS Conf. on Controlled Fusion and Plasma Physics, Budapest, Hungary Vol. 24B page： 1192-1195 2000

Bubble Formation in Tungsten Surface during Low Energy and High Flux Helium/Hydrogen Plasma Irradiation

M.Y.Ye, S.Fukuta, N.Ohno, S.Takamura

Proc. of Japan/US Workshop(00FT5-1) on High Heat Flux Components and Plasma Surface Interactions for Next Fusion Devices, Osaka, Japan Vol. 1 page： 288-298 2000

2-D PIC simulation on space-charge limited emission current from plasma-facing components Reviewed

Asano K, Ohno N, Ye MY, Fukuta S, Takamura S

CONTRIBUTIONS TO PLASMA PHYSICS Vol. 40 ( 3-4 ) page： 478 - 483 2000

Sawai M., Misawa T., Ohno N., Takamura S.

Meeting Abstracts of the Physical Society of Japan Vol. 55 ( 0 ) 2000

2-D PIC Simulation on Space-Change Limited Emission Current from Plasma-Facing Components Reviewed

Asano K., Ohno N., Ye M. Y., Fukuta S., Takamura S.

Meeting Abstracts of the Physical Society of Japan Vol. 55 ( 0 ) 2000

Dynamic Response of Dust Particles Trapped Reviewed

Sawai M., Misawa T., Ohno N., Takamura S.

Meeting Abstracts of the Physical Society of Japan Vol. 55 ( 0 ) 2000

27pA08P Measurements of Fluctuations in Detached Recombining Plasmas Reviewed

( 17 ) 2000

27pA10P Radial Profile Measurement of Detached Plasma in Divertor Plasma Simulator NAGDIS-II Reviewed

( 17 ) 2000

Recent Topics in Experiments. Molecular Activated Recombination Processes in Divertor Plasmas Reviewed

OHNO Noriyasu

Journal of Plasma and Fusion Research Vol. 75 ( 10 ) page： 1162 - 1168 1999.10

Publisher：The Japan Society of Plasma Science and Nuclear Fusion Research

Molecular processes in detached divertor plasmas, especially molecular activated recombination processes, are briefly reviewed. Several reaction chains related to the volumetric recombination process, that are associated with the vibrationally excited hydrogen molecule are explained. Experimental observations of the molecular activated recombination are also reported.

DOI： 10.1585/jspf.75.1162

CD-ROM Study on Plasma Dynamics Using Scientific Animation II Reviewed

Vol. 75 ( 10 ) 1999.10

PSI in Fusion Devices Edge Plasma Physics and Atomic-Molecular Processes Reviewed

OHNO Noriyasu

Journal of Plasma and Fusion Research Vol. 75 ( 4 ) page： 378 - 383 1999.4

Publisher：The Japan Society of Plasma Science and Nuclear Fusion Research

Edge plasma physics and atomic-molecular processes relating to plasma heat flow to material surfaces are discussed. The local heat flow was found to be enhanced by a thermal contraction induced by cross-field potential variation in a plasma, resulting in hot spot formation on the plasma-facing materials due to nonlinear thermal bifurcation induced by thermoelectron emission. Also examined is the recombination enhancement due to the vibrationally excited hydrogen molecule generated from material surfaces in detached plasma with molecular activated recombination.

DOI： 10.1585/jspf.75.378

Molecular activated recombination in detached recombining plasmas - Reply Reviewed International coauthorship International journal

Ohno N, Ezumi N, Takamura S, Krasheninnikov SI, Pigarov AY

PHYSICAL REVIEW LETTERS Vol. 82 ( 10 ) page： 2216 - 2216 1999.3

Two-dimensional structure of the detached recombining helium plasma associated with molecular activated recombination Reviewed International coauthorship International journal

Nishijima D., Ezumi N., Kojima H., Ohno N., Takamur S., Krasheninnikov S., Pigarov A.

Journal of Nuclear Materials Vol. 266 page： 1161 - 1166 1999.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Nuclear Materials

The structural change of the detached plasmas associated with the molecular activated recombination (MAR) has been studied in a high density helium plasma with helium or hydrogen puff in the linear divertor plasma simulator, NAGDIS-II. The ion particle flux with the hydrogen gas puff starts to decrease in the upstream region close to the plasma source, compared to that with the helium puff. The reduction of the ion particle flux along the magnetic field is found to depend on the plasma density. With the hydrogen gas puff, the attenuation of the ion particle flux is getting smaller as increasing plasma density, which is opposite tendency in pure helium detached plasma where the conventional electron-ion recombination (EIR) is dominating.

DOI： 10.1016/S0022-3115(98)00565-0

Contribution of molecular activated recombination to hydrogen plasma detachment in the divertor plasma simulator NAGDIS-II Reviewed International coauthorship International journal

Ezumi N., Nishijima D., Kojima H., Ohno N., Takamura S., Krasheninnikov S., Pigarov A.

Journal of Nuclear Materials Vol. 266 page： 337 - 342 1999.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Nuclear Materials

We have performed experiments on detached hydrogen plasmas associated with molecular activated recombination (MAR) in a linear divertor plasma simulator. Reductions of the ion particle flux and heat load to the target plate were clearly observed in hydrogen plasmas with the hydrogen gas puff. Detailed analysis of Balmer series spectra with the Collisional-Radiative Atomic-Molecular data (CRAMD) code shows that MAR mainly appears as a weak dependence of the Balmer series emission intensities on experimental conditions in detached hydrogen plasmas. The plasma conditions necessary to obtain plasma detachment through MAR or EIR (electron ion recombination including the radiative and three-body recombination) in tokamak divertors are also discussed.

DOI： 10.1016/S0022-3115(98)00533-9

Dynamic Response of Detached Recombining Plasmas to Plasma Heat Pulse Produced by RF Heating Reviewed

Hot spot formation on electron-emissive target plate with plasma potential variation across magnetic field Reviewed International journal

Ye MY, Kudose K, Kuwabara T, Ohno N, Takamura S

JOURNAL OF NUCLEAR MATERIALS Vol. 266 page： 742 - 746 1999.3

小特集「プラズマ原子・分子過程の展望」5.最近の実験的なトピックス　5.1ダイバータプラズマ中の分子活性化再結合過程

大野哲靖

プラズマ・核融合学会誌 Vol. 75 ( 10 ) page： 1162-1168 1999

Hot Spot Formation on Electron-Emissive Target Plate with Plasma Potential Variation acoss Magnetic Field Reviewed

M.Y.Ye, K.Kudose, T.Kuwabara, N.Ohno, S.Takamura

Journal of Nuclear Materials Vol. 266-269 page： 1001-1004 1999

Simulation on Structure and Dynamic Behavior of Dust Particles in a Direct Current Plasma Sheath Reviewed

K.Asano, N.Ohno, S.Takamura

Journal of Plasma and Fusion Research Vol. 75 ( 10 ) page： CD-ROM 1999

Instability of Dust Particles in a Coulomb Crystal due to Delayed Charging Reviewed

S.Nunomura, T.Misawa, N.Ohno, S.Takamura

Physical Review Letters Vol. 83 ( 10 ) page： 1970-1973 1999

Dynamic response of detached recombining plasmas to plasma heat pulse in a divertor simulator Reviewed

N.Ohno, M.Tanaka, N.Ezumi, D.Nishijima, S.Takamura, S.I.Krasheninnikov, A.Yu.Pigarov, J.Park

Physics of Plasmas Vol. 6 ( 6 ) page： 2486-2494 1999

Two-dimensional structure of the detached recombining plasmas associated with molecular acivated recombination Reviewed

D.Nishijima, N.Ezumi, H.Kojima, N.Ohno, S.Takamura, S.I.Krasheninnikov, A.Yu.Pigarov

Journal of Nuclear Materials Vol. 266-269 page： 1161-1166 1999

Contribution of molecular activated recombination to hydrogen plasma detachment in the divertor plasma simulator, NAGDIS-(]G0002[) Reviewed

N.Ezumi, D.Nishijima, H.Kojima, N.Ohno, S.Takamura, S.I.Krasheninnikov, A.Yu,Pigarov

Journal of Nuclear Materials Vol. 266-269 page： 337-342 1999

小特集「多様なPSI現象」4.核融合装置におけるプラズマ・表面相互作用　4.1周辺プラズマ物理と原子・分子過程

大野哲靖

プラズマ・核融合学会誌 Vol. 75 ( 4 ) page： 378-383 1999

小特集「プラズマ原子・分子過程の展望」5.最近の実験的なトピックス5.1ダイバータプラズマ中の分子活性化再結合過程

大野哲靖

プラズマ・核融合学会誌 Vol. 75 ( 10 ) page： 1162-1168 1999

Modification of Tungsten Surface Irradiated by Low Energy and High Flux Helium Plasma

M.Y.Ye, S.Fukuta, N.Ohno, S.Takamura, K.Tokunaga, N.Yoshida

Proc. of 2nd IAEA TCM on Steady-State Operation of Magnetic Fusion Devices, Vol.II FURKU Report 99-05 Vol. II page： 611-617 1999

Application of Strongly Ionized AC Tokamak Plasma for Synthesis of TiN Thin Films

M.Y.Ye, O.Matsuda, N.Ohno, Y.Uesugi, M.Takagi, S.Takamura

The 2nd Int. Symposium on Applied Plasma Science, Osaka, Japan, 1999, Proc. of ISAPS99, Advances in Applied Plasma Science Vol. 2 page： 23-28 1999

Instabilities of Dust Particles Levitated in an Ion Sheath with Low Gas Pressure

T.Misawa, S.Nunomura, K.Asano, N.Ohno, S.Takamura

Proc. 2nd Int. Conf. on the Physics of Dusty Plasmas, ICPDP-99, in "Frontiers in Dusty Plasmas", Hakone Vol. Elsevier page： 465-468 1999

Structural Formation and Stability of Coulomb Clouds in Medium through Low Gas Pressure Range

S.Takamura, N.Ohno, S.Nunomura, T.Misawa, K.Asano

Proc. 2nd Int. Conf. on the Physics of Dusty Plasmas, ICPDP-99, in "Frontiers in Dusty Plasmas",Hakone, Vol. Elsevier page： 337-344 1999

Ion Temperature Measurement and Energy Balance in Detached Plasmas in the Divertor Simulator, NAGDIS-II

D.Nishijima, D.G.Whyte, Y.Uesugi, N.Ohno, N.Ezumi, Y.Hirohashi, H.Arakawa, S.Takamura, I. Katsumata

Proc. 26th EPS Conf. on Controlled Fusion and Plasma Physics, Maastricht, Europhysics Conference Abstracts Vol. 23J page： 485-488 1999

( 16 ) 1999

Dependence of Radial Electric Field on Neutral pressure Related to Ion Heating in NAGDIS-II Device Reviewed

WHYTE D G

( 16 ) 1999

Effects of Radiation Transport in Detached Recombining Plasmas Reviewed

( 16 ) 1999

Structures of Detached Plasmas with High Heat Flow in a Strong Magnetic Field Reviewed

ニシジマダイスケ, エズミナオミチ, アオキコウジ, オオノノリヤス*, タカムラシュウイチ**

東北大学研究所報告. (工学), 流体科学研究所 Vol. 10 page： 157 - 166 1998.3

*Experimental Evidence of Molecular Activated Recombination in Detached Recombining Plasmas Reviewed

N.Ohno, N.Ezumi, S.Takamura, S.I.Krasheninnikov, A.Yu.Pigarov

Physical Review Letters Vol. 81 ( 4 ) page： 818-821 1998

Numerical Simulation on Structure of Detached Helium Plasmas with Hydrogen and Helium Gas Puff in NAGDIS-II Reviewed

D.Nishijima, N.Ezumi, K.Aoki, N.Ohno, S.Takamura

Contributions to Plasma Physics Vol. 38 ( 1/2 ) page： 55-60 1998

Enhancement of plasma heat flow to the conductive divertor plate associated with cross-field potential variation and thermoelectron emission Reviewed

T.Kuwabara, K.Kudose, M.Y.Ye, N.Ohno, S.Takamura

Contributions to Plasma Physics Vol. 38 ( 1-2 ) page： 349-354 1998

Static and Dynamic Erosion Behavior of TiC Coated Graphite in High Heat Flux Plasma Reviewed

S.Takamura, K.Hayashi, N.Ohno, K.Morita

Journal of Nuclear Materials Vol. 258-263 page： 961-966 1998

Confinement and Structure of Electrostatically Coupled Dust Clouds in a Direct Current Plasma-Sheath Reviewed

S.Nunomura, N.Ohno, S.Takamura

Physics of Plasmas Vol. 5 page： 3517-3523 1998

Heat Flow through Plasma Sheaths Reviewed

S.Takamura, M.Y.Ye, T.Kuwabara, N.Ohno

Physics of Plasma Vol. 6 ( 6 ) page： 2151-2158 1998

Anomaly of Langmuir Probe Characteristics in Detached Recombining Plasma Reviewed

N.Ezumi, N.Ohno, K.Aoki, D.Nishijima, S.Takamura

Contributions to Plasma Physics Vol. 38 ( S ) page： 31-37 1998

Particle simulation on multiple dust layers of coulomb cloud in cathode sheath edge Reviewed

K.Asano, S.Nunomura, T.Misawa, N.Ohno, S.Takamura

Czechoslovak Journal of Physics Vol. 48 page： 239-244 1998

Simulation and experiment on detached plasmas in the linear divertor simulator NAGDIS-(]G0002[) Reviewed

N.Ohno, N.Ezumi, D.Nishijima, S.Takamura

Czechoslovak Journal of Physics Vol. 48 page： 127-136 1998

Erosion Characteristics of High-Temperature Metal-Carbon Composite Materials under High-Flux Plasma Irradiation

N.Ohno, S.Takamura

Proc. of Japan/US Workshop(98FT5-01) on High Heat Flux Components and Plasma Surface Interactions for Next Fusion Devices, Toki, Japan, 1998 page： 474-483 1998

Deposition of TiN Thin Films with Strongly Ionized Plasmas in high Duty AC Tokamak Discharge

M.Y.Ye, O.Matsuda, N.Ohno, M.Takagi, Y.Uesugi, S.Takamura

Proc. of 1998 International Congress on Plasma Physics combined with 25th EPS Conference on Controlled Fusion and Plasma Physics, Praga, Czech page： 2509-2512 1998

Observation of Trapping and Fluctuation of a Dust Could at a Very Low Gas Pressure

S.Nunomura, T.Misawa, K.Asano, N.Ohno, S.Takamura

Proc. of 1998 International Congress on Plasma Physics combined with 25th EPS Conference on Controlled Fusion and Plasma Physics, Praga, Czech page： 114-117 1998

Change in Detached Helium Plasma's Structure Associated with Molecular Activated Recombination

D.Nishijima, N.Ezumi, H.Kojima, N.Ohno, S.Takamura

Proc. of 1998 International Congress on Plasma Physics combined with 25th EPS Conference on Controlled Fusion and Plasma Physics, Praga, Czech page： 23-26 1998

Space-Charge Limited Emission Current from Material Surface in a Plasma

Y.M.Ye, T.Shimada, T.Kuwabara, N.Onno, S.Takamura

Proc. of 1998 International Congress on Plasma Physics combined with 25th EPS Conference on Controlled Fusion and Plasma Physics, Praga, Czech page： 7-10 1998

Observation of Funnel-Shaped Dust Cloud Composed of Multiple Layers Reviewed

MISAWA T., NUNOMURA S., ASANO K., OHNO N., TAKAMURA S.

Meeting Abstracts of the Physical Society of Japan Vol. 53 ( 0 ) 1998

Experimental evidence of molecular activated recombination in detached recombining plasmas Reviewed International coauthorship International journal

Ohno N., Ezumi N., Takamura S., Krasheninnikov S.I., Pigarov A.Y.

Physical Review Letters Vol. 81 ( 4 ) page： 818 - 821 1998

Language：English Publishing type：Research paper (scientific journal) Publisher：Physical Review Letters

Molecular activated recombination (MAR) has been clearly observed for the first time in a divertor plasma simulator. A small amount of hydrogen gas puffing into a helium plasma strongly reduced the ion particle flux along the magnetic field, although the conventional radiative and three-body recombination processes were quenched. Careful comparison of the observed helium Balmer spectra with collisional radiative atomic and molecular data indicates that the population distribution over the atomic levels with relatively low principal quantum numbers can be well explained by taking the MAR effects into account. © 1998 The American Physical Society.

DOI： 10.1103/PhysRevLett.81.818

Erosion and Redeposition Processes of Molybdenum with Oblique Incidence of Magnetic Field Reviewed

小島昌博, 井戸康広, 江角直道, OHNO Noriyasu, TAKAMURA Shuichi

プラズマ・核融合学会誌 = Journal of plasma and fusion research Vol. 73 ( 4 ) page： 452 - 459 1997.4

Language：English Publishing type：Research paper (scientific journal) Publisher：プラズマ・核融合学会

Erosion and redeposition processes have been investigated using a linear plasma device and a Monte Carlo simulation code. Argon plasmas were irradiated on a molybdenum substrate with an oblique incidence of magnetic field. The erosion distributions depending on the direction of magnetic field are clearly observed. Numerical code analysis gives a qualitative explanation for the erosion profiles by considering the effect of prompt redeposition of high Z material. However, we have still quantitative differences for their erosion and redeposition rates.

Effects of ion flow by ExB drift on dust particle behavior in magnetized cylindrical electron cyclotron resonance plasmas Reviewed International journal

Nunomura S, Ohno N, Takamura S

JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS Vol. 36 ( 2 ) page： 877 - 883 1997.2

Effects of Ion Flow by E * B Drift on Dust Particle Behavior in Magnetized Cylindrical Electron Cyclotron Resonance Plasmas.

Nunomura Shota, Ohno Noriyasu, Takamura Shuichi

Japanese Journal of Applied Physics Vol. 36 ( 2 ) page： 877 - 883 1997

Language：English Publisher：The Japan Society of Applied Physics

Interactions between poloidal ion flow associated with E× B drift and dust particles have been investigated in magnetized cylindrical electron cyclotron resonance plasmas, in which radial electric field is controlled by a biased ring-shaped electrode. The dust particles are spun out and removed from the plasma due to poloidal ion drag force, even when the inward electric force on the dust particles is larger than the gravitational force. This indicates the possibility of using a new method to remove the dust particles from the processing plasma. On the other hand, in order to sustain the dust particles in the plasma, the effects of this poloidal ion flow should be substantially reduced by the friction between the dust particles and neutral gas.

DOI： 10.1143/jjap.36.877

Dynamic CT System for Visible Light Emission from Tokamak Plasma with Charge Coupled Detectors Reviewed

Study of hot tungsten emissive plate in high heat flux plasma on NAGDIS-I Reviewed

M.Y.Ye, N.Ohno, S.Takamura

Journal of Nuclear Materials Vol. 241-243 page： 349-352 1997

Density threshold for plasma detachment in gas target Reviewed

N.Ezumi, S.Mori, N.Ohno, S.Takamura, H.Suzuki, J.Park

Journal of Nuclear Materials Vol. 241-243 page： 349-352 1997

Observation of the Structure and its Formation Process of a New Volumetric Coulomb Cloud Composed of Different Multiple Dust Layers Reviewed

S.Nunomura, N.Ohno, S.Takamura

Japan Journal of Applied Physics Vol. 36 page： L949-951 1997

Effects of Ion Flow by 丑X(]G1388[) Drift on Dust Particle Behaviour in Magnetizat Cylindrical Electron Cyclotron Reviewed

S.Nunomura, N.Ohno, S.Takamura

Japan Journal of Applied Physics Vol. 36 page： 877-883 1997

講座「プラズマにおけるカオス現象の観測と実験解析II」3.シースに関連したカオス３　2.準周期ルート

大野哲靖

プラズマ・核融合学会誌 Vol. 73 ( 8 ) page： 827-833 1997

Numerical Analysis on Fine Particle's Behavior in an Ion-Beam Plasma System

N.Ohno, M.Nakamura, S.Nunomura, S.Takamura

Proc. of 23th Inernational Conference on Phenomena in Ionized Gases, Toulouse, France 1997 page： 196-197 1997

Full AC Tokamak Discharge in A Small Research Device CSTN-AC

S.Takamura, K.Hayashi, Y.Marushita, K.Tashiro, Y.Uesugi, N.Ohno, K.Sakurai, M.Kobayashi, M.Takagi, O.Mitarai

Proc. of 20th EPS Conference on Controlled Fusion and Plasma Physics, Bercgtesgardenm Germany, 1997 page： 1225-1228 1997

Studies on Plasma-Gas Interactions in Powerful High Heat Flux Plasma Device NAGDIS-II

N.Ezumi, N.Ohno, Y.Uesugi, J.Park, S.Watanabe, S.A.Cohen, S.Krasheninnikov, A.Yu. Pigarov, M.Takagi, S.Takamura

Proc. of 20th EPS Conference on Controlled Fusion and Plasma Physics, Bercgtesgardenm Germany, 1997 page： 1225-1228 1997

Structure of Detached Plasmas with High Heat Flow in a Strong Magnetic Field

D.Nishijima, N.Ezumi, K.Aoki, N.Ohno, S.Takamura

International Symposium on Plasma and Flow Simulation for Materials Processing, Sendai, Japan, 1997, Reports of the Institute of Fluid Science Tohoku University Vol. 10 page： 157-166 1997

講座「プラズマにおけるカオス現象の観測と実験解析I」2.プラズマにおけるカオス　2.2カオスの解析手法

大野哲靖

プラズマ・核融合学会誌 Vol. 73 ( 7 ) page： 682-687 1997

Plasma Heat FLow through Plasma Sheath with Electron Emission and Plasma Poe\tental Variation across Magnetic Field

M.Y.Ye, K.Kudose, T.Kuwabara, N.Ohno, S.Takamura

7th Asia Pacific Physics Conference, Beijing, China, 1997 Vol. 1 1997

Static and Dynamic Erosion Behavior of TiC Coated Graphite in High Heat Flux Plasma

S.Takamura, K.Hayashi, N.Ohno, K.Morita

8th International Conference on Fusion Reactor Materials, Sendai, Japan, 1997 Vol. 1 1997

Structure and Dynamic Behavior of a Coulomb Cloud Composed of Different Multiple Dust Layers

S.Nunomura, T.Misawa, K.Asano, N.Ohno, S.Takamura

39th Annual Meeting fo the Division of Plasma Physics of the American Physical Society, Pittsburgh, USA, 1997 Vol. 1 1997

Heat Flows through Plasma Sheaths

S.Takamura, M.Y.Ye, T.Kuwabara, N.Ohno

39th Annual Meeting of the Division of Plasma Physics of the American Physical Society, Pittsburgh, USA, 1997 Vol. 1 1997

Suppression of secondary electron emission from the material surfaces with grazing incident magnetic field in the plasma Reviewed International journal

Takamura S, Mizoshita S, Ohno N

PHYSICS OF PLASMAS Vol. 3 ( 12 ) page： 4310 - 4312 1996.12

Nonlinear interactions between high heat flux plasma and electron-emissive hot material surface Reviewed International journal

Ye MY, Masuzaki S, Shiraishi K, Takamura S, Ohno N

PHYSICS OF PLASMAS Vol. 3 ( 1 ) page： 281 - 292 1996.1

Particle in Cell Simulation on Thermoelectron Emission from Hot Target Plate Reviewed

N.Ohno, E.Shimizu, S.Takamura

Contributions to Plasma Physics Vol. 36 ( 2-3 ) page： 386-390 1996

Suppression of Secondary Electron Emission From the Material Surfaces with Grazing Incident Magnetic Field in th Plasma Reviewed

S.Takamura, S.Mizoshita, N.Ohno

Physics of Plasma Vol. 3 ( 12 ) page： 4310-4312 1996

Numerical Simulation Study on Density Dependence of Plasma Detachment in Simulated Gas Divertor Experiments of The TPD-I Device Reviewed

N.Ohno, S.Mori, N.Ezumi, M.Takagi, S.Takamura, H.Suzuki

Contributions to Plasma Physics Vol. 36 ( 2-3 ) page： 339-343 1996

Characterization of gaseous carbon plasma in a low-temperature tokamak discharge Reviewed

O.Matsuda, N.Ohno, S.Takamura

Plasma Source Science and Technology Vol. 5 page： 356-362 1996

Static and Dynamic Characteristics of Plasma Detachment in Gas Target Scheme

N.Ezumi, M.Tanaka, S.Mori, N.Ohno, M.Takagi, S.Takamura, H.Suzuki

Proc. of the 1996 International Conference on Plasma Physics, Nagoya, Japan page： 614-617 1996

Control of Dust Particles' Behavior by Using Ion Flow

S.Nunomura, M.Nakamura, N.Ohno, S.Takamura

International Conference on the Physics of Dusty Plasmas, Goa, India, 1996, "Advances in Dusty Plasmas" ed. by PO.K.Shukla, D.A Mendis and T.Desai, World Scientific Publishing Co., Singapore Vol. 1 1996

Generation of Dustyt Plasma in a Double-Plasma Device

M.Nakamura, S.Nunomura, H.K.Malik, N.Ohno, S.Takamura

Proc. of the 1996 International Conference on Plasma Physics, Naoya Japan page： 1982-1985 1996

Characterization of Gaseous Carbon Plasma in a Low-Temperature Tokamak Discharge as Processing Plasma

O.Matsuda, N.Ohno, S.Takamura

Proc. of the 1996 International Conference on Plasma Physics, Naoya Japan page： 1814-1817 1996

Impurtity Generation, Transport and Redeposition at Plasma Boundary

M.Kojima, Y.Ido, N.Ezumi, N.Ohno, S.Takamura

Proc. of the 1996 International Conference on Plasma Physics, Naoya Japan page： 1402-1405 1996

Physical Mechanism of Plasma Heat Flow into Electron-Emissive Hot Material Surface

M.Y.Ye, T.Kuwabara, N.Ohno, S.Takamura

Proc. of the 1996 International Conference on Plasma Physics, Naoya Japan page： 1398-1401 1996

Plasma Heat Contraction on Conducting Plate due to Plasma Potential Variation across the Magnetic Field

T.Kuwabara, K.Kudose, M.Y.Ye, N.Ohno, S.Takamura

Proc. of the 1996 International Conference on Plasma Physics, Naoya Japan page： 1386-1389 1996

High Heat Flux Plasma Generator for New Divertor Plasma Simulator in Nagoya University

S.Narita, N.Ezumi, N.Ohno, Y.Uesugi, S.Takamura

Proc. of the 1996 International Conference on Plasma Physics, Naoya Japan page： 1362-1365 1996

Comprehensive Studies on Secondary Electron Emission from Material Surface in Magnetized Plasma

S.Takamura, S.Mizoshita, K.Shiraishi, N.Ohno

Proc. of the 1996 International Conference on Plasma Physics, Nagoya, Japan page： 610-613 1996

Temperature Dependence of Ti Sputtering Yield from TiC Composite Material under High Heat Flux Plasma Irradiation

K.Hayashi, N.Ohno, S.Takamura, K.Morita

Proc. of the 1996 International Conference on Plasma Physics, Nagoya, Japan page： 1410-1413 1996

Full AC Plasma Current Operation in the CSTN-AC Tokamak

K.Hayashi, Y.Marushita, K.Tashiro, N.Ohno, S.Takamura, O.Mitarai, K.Sakurai, S.Satoh T.Kuwabara

Proc. of the 1996 International Conference on Plasma Physics, Nagoya, Japan page： 1246-1249 1996

1P-YM-5 Effect of Plasma Flow on Transport of Fine Particles Reviewed

Nunomura S., Nakamura M., Ohno N., Takamura S.

Meeting Abstracts of the Physical Society of Japan Vol. 51 ( 0 ) 1996

電界制御による微粒子プラズマの生成 Reviewed

布村正太, 古橋一能, 大野哲靖, 高村秀一

電気学会研究会資料. EP, プラズマ研究会 Vol. 1995 ( 31 ) page： 51 - 58 1995.5

Reduction of Plasma heat flow to a simulated divertor target plate by ponderomotive force Reviewed

S.Masuzaki, N.Ohno, S.Takamura

Journal of Nuclear Materials Vol. 220-222 page： 1112-1115 1995

Gas target experiments high heat flux plasma of the TPD-I device Reviewed

N.Ohno, S.Masuzaki, M.Takagi, S.Takamura, K.Ishii

Journal of nuclear materials Vol. 220-222 page： 279-283 1995

Heat Transport and Associated Surface Phenomena at the Plasma-Material Interface in Heat and Mass Transfer under Plasma Condition

S.Takamura, N.Ohno

Begell House, Inc., page： 245-252 1995

Experimental Study on Plasma Heat Flow to Plasma Facing Materials Reviewed

S.Masuzaki, N.Ohno, S.Takamura

Journal of Nuclear Materials Vol. 223 page： 173-178 1995

Monte Carlo Simulation on Active Helium-Ash Exhaust by Divertor Biasing Reviewed

T.Kuwabara, M.Kojima, N.Ohno, Y.Uesugi, S.Takamura, Y.Yamamura

Journal of Nuclear Materials Vol. 220-222 page： 1001-1004 1995

Secondary electron emission from solid surface in an oblique magnetic field Reviewed

S.Mizoshita, K.Shiraishi, N.Ohno, S.Takamura

Journal of Nuclear Materials Vol. 220-222 page： 488-492 1995

Heat Transport and Associated Surface Phenomena at the Plasma-Material Interface Reviewed

S.Takamura, N.Ohno

"Heat and Mass Transfer under Plasma Condition" ed by P. Fan chais, M. Boubs and J. Vander Mullen, Begell House page： 245-251 1995

Sensitive Detection of Probing Electron Transport and Magnetic Field Structure in Toroidal Plasma Configuration Reviewed

S.Sakurai, N.Ohno, S.Takamura

Japanese Journal of Applied Physics Vol. 33 ( 2 ) page： 1161-1168 1994

Detection of Electron Beam Orbits in a Tokamak Configuration with External Helical Magnetic Field Reviewed

S.Sakurai, N.Ohno, S.Takamura

Journal of Plasma and Fusion Research Vol. 70 ( 2 ) page： 173-178 1994

Gas Target Experiments in High Heat Flux Plasma of the TPD-I Device

N.Ohno, S.Masuzaki, S.Mori, N.Ezumi, M.Takagi, S.Takamura

36th Annual Meeting APS Division of Plasma Physics, Minneapolis, USA Vol. 1994 1994

Oda Yoshihiro, Takamura Shuichi, Uesugi Yoshihiko, Ohno Noriyasu

Journal of plasma and fusion research Vol. 69 ( 3 ) page： p250 - 257 1993.3

Authorship：Last author Language：English

A tomographic reconstruction system with five channels for visible light emission has been developed and applied to observe the visible light emission from HYBTOK-II tokamak plasma. A compact and low cost computed tomography (CT) system with a good spatial and time resolution was established using an array of charge coupled devices. The shuttering capability of the CT system is 300 μs. A rapid change of the emission profile due to the deviation from the tokamak equilibrium was successfully followed. Present CT system with five CCD cameras enables us to recognize a local increment of the visible light emission due to the plasma arcing, which is difficult to observe with the conventional three camera CT system, which is often employed for fusion plasma diagnostics.

Gaseous Silicon Plasma Generated by a Low-Temperature Tokamak Discharge Reviewed

Hiramatsu Kenji, Takamura Shuichi, Ohno Noriyasu

Journal of plasma and fusion research Vol. 69 ( 2 ) page： p121 - 128 1993.2

Dynamical CT System for visible Light Emission From Tokamak Plasma with Charge Coupled Defectors Reviewed

Y.Oda, Y.Uesugi, S.Takamura, N.Ohno

Journal of Plasma and Fusion Research Vol. 69 ( 3 ) page： 250-257 1993

Sheath Voltage on Carbon Surface in a Hydrogen Plasma with Hot Electrons Reviewed

K.Shiraishi, N.Ohno, S.Takamura

Journal of Plasma and Fusion Research Vol. 69 ( 11 ) page： 1371-1377 1993

Chaotic Behavior Driven by an External Periodic Oscillation in a Current-Carrying Unstable Ion Sheath Reviewed

N.Ohno, A.Komori, M.Kono, Y.Kawai

Physics of Fluids B Vol. 5 ( 3 ) page： 796-805 1993

Experimental and Theoretical Study on Plasma Heat Flow to Plasma Facing Materials

S.Masuzaki, H.Konnno, N.Ohno, S.Takamura

Proc. of 20th EPS Conference on Controlled Fusion and Plasma Physics, Lisboa Vol. 743-746 1993

BIFURCATION PHENOMENA IN AN EMISSIVE PLATE - SIMULATED DIVERTOR PLASMA SYSTEM Reviewed

TAKAMURA S, OHNO N, SHIRAISHI K, MASUZAKI S

JOURNAL OF NUCLEAR MATERIALS Vol. 196 page： 448 - 451 1992.12

SHEATH FORMATION ON CARBON AND REFRACTORY-METALS IN A PLASMA WITH ENERGETIC ELECTRONS Reviewed International journal

SHIRAISHI K, OHNO N, UESUGI Y, TAKAMURA S

JOURNAL OF NUCLEAR MATERIALS Vol. 196 page： 745 - 749 1992.12

INTERMITTENCY DURING TRANSITION BETWEEN STATIONARY AND PERIODIC STATES IN PLASMAS Reviewed International journal

KOMORI A, OHNO N, YAMAURA T, KAWAI Y

PHYSICS LETTERS A Vol. 170 ( 6 ) page： 439 - 442 1992.11

Sheath Formation on Carbon and and Refractory Metals in a Plasma with Energetic Electrons Reviewed

K.Shiraishi, N.Ohno, Y.Uesugi, S.Takamura

Journal of Nuclear Materials Vol. 196-198 page： 745-749 1992

高熱流プラズマの生成とその高速掃引プローブ計測システムによる計測 Reviewed

増崎貴、大野哲靖、高木誠、高村秀一

電気学会論文誌A Vol. 112 ( 11 ) page： 913-921 1992

Intermittency During Transition Between Stationary and Periodic States of Plasmas Reviewed

A.Komori, N.Ohno, T.Yamaura, Y.Kawai

Physics Letter A Vol. 170 ( 6 ) page： 439-442 1992

Bifurcation Phencomena in an Emissive Plate-Simulated Divertor Plasma System Reviewed

S.Takamura, N.Ohno, K.Shiraishi, S.Masuzaki

Journal of Nuclear Materials Vol. 196-198 page： 448-451 1992

Studies on Sheath Formation in Divertor Plasmas by Computer Simulation Using Particle Reviewed

N.Ohno, S.Masuzaki, H.Konno, S.Takamura

Contributions to Plasma Physics Vol. 3 ( 3-4 ) page： 249-354 1992

Gaseous Silicon Plasma Generated by a Low-Temperatue Tokamak Discharge Reviewed

K.Hiramatsu, N.Ohno, S.Takamura

Jouranl of Plasma and Fusion Research Vol. 69 ( 2 ) page： 121-128 1992

Numerical Study of Potential Formation and Negative Resistance in a Currnet Carrying Ion Sheath

N.Ohno, A.Komori, Y.Kawai, S.Takamura

Proc. of 1992 International Conference on Plasma Physics, Innsbruck, Austria page： 1807-1810 1992

26p-C-7 A quasiperiodic route to chaos observed in an ion sheath Reviewed

Komori A, Ohno N, Kono M, Tanaka M, Kawai Y

Meeting Abstracts of the Physical Society of Japan Vol. 1992 ( 0 ) 1992

Averaging effect of radical particle profile by the scanning plasma method in SiH<inf>4</inf>Ar plasmas Reviewed International journal

Fujiyama H., Kawasaki H., Matsuda Y., Ohno N.

Materials Science and Engineering A Vol. 140 ( C ) page： 569 - 575 1991.7

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Materials Science and Engineering A

A new plasma-enhanced chemical vapour deposition (PECVD) method has been developed for preparation of large-area uniform hydrogenated amorphous silicon (aSi:H) thin films. Detailed two-dimensional profiles of both charged particles and radical particles have been measured in magnetized multielectrode glow discharge plasmas in 10% SiH4Ar gas. The detailed profiles of SiH* and Ar I emissions had two peaks in the negative glow and cathode sheath regions but, for Hα emission, only one peak was observed in the cathode sheath region. It was verified that large-area uniform profiles of not only plasmas but also SiH* emission could be realized in the presence of modulated crossed magnetic and electric fields. By using this scanning plasma method (SPM), inhomogeneities for both profiles of plasma and SiH* (413.5 nm) emission intensity have improved to less than 2.5% near the substrate outside the discharge region. The thickness profile of prepared a-Si:H thin film has also been unified to less than 4.8% by SPM. © 1991.

DOI： 10.1016/0921-5093(91)90480-B