研究者詳細 - 大野　哲靖

論文 - 大野　哲靖

分割表示 657 件中 61 - 80 件目／全件表示 >>

Penetration of deuterium into neutron-irradiated tungsten under plasma exposure 査読有り

Yajima M., Hatano Y., Alimov V.K., Toyama T., Kuwabara T., Schwarz-Selinger T., Oya Y., Spitsyn A.V., Ohno N.

Physica Scripta 96 巻 ( 12 ) 頁： 124042 2021年10月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physica Scripta

Hydrogen isotope trapping at lattice defects in neutron-irradiated tungsten (W), a leading candidate as plasma facing material, is an important problem determining tritium (T) inventory in a vacuum vessel of a future fusion reactor. In this study, W samples were irradiated with neutrons in the Belgium Reactor 2 at 563 K to 0.06 or 0.016 displacement per atom (dpa). After characterizing defects by positron lifetime measurements, deuterium (D) penetration under exposure to D plasma was examined at 563-773 K. Positron lifetime showed the presence of dislocations, monovacancies and relatively large vacancy clusters. These defects trapped D atoms with different values of binding energy. Dependence of D retention on plasma exposure temperature and damage level indicated that the concentrations of weak traps with smaller binding energy increased more significantly with damage level than those of strong traps.

DOI： 10.1088/1402-4896/ac2c20

Scopus

その他リンク： https://iopscience.iop.org/article/10.1088/1402-4896/ac2c20/pdf

The dependence of Mo ratio on the formation of uniform black silicon by helium plasma irradiation 査読有り国際共著

Shi Quan, Kajita Shin, Feng Shuangyuan, Ohno Noriyasu

JOURNAL OF PHYSICS D-APPLIED PHYSICS 54 巻 ( 40 ) 頁： 405202 2021年10月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Physics D: Applied Physics

Reducing the optical reflection of silicon (Si) material is a crucial issue on the surface of solar cells and other photonic applications. Fabrication of nanocone structures on the Si surface (black Si) by plasma (helium or argon) irradiation is a novel technique in recent decades with advantages, such as simple, economical, and harmless to the Si substrate. However, the uniformity and controllability of the surface remain problematic. In this study, uniform black silicon was obtained by low energy (<50 eV) helium ion irradiation with auxiliary Mo co-deposition. The characteristics of the nanocone show a clear relation with the Mo ratio. Deposited Mo was found to accumulate on the cone body, especially on the tip, and it worked as a nano mask to induce the formation of the nanocone and protect it from sputtering. The surface with high and large diameter nanocones possesses low reflectances of roughly 2%. The study of the relation between Mo ratio, characteristics of the nanostructure, and the reflectance of the surface raises a potential method of surface tailoring.

DOI： 10.1088/1361-6463/ac1190

Web of Science

Scopus

Enhanced photocatalytic ethylene decomposition with anatase-rutile mixed nanostructures formed by He plasma treatment 査読有り

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

Journal of Photochemistry and Photobiology A: Chemistry 418 巻頁： 113420(8 pp) 2021年9月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Photochemistry and Photobiology A: Chemistry

In order to realize high-performance titanium dioxide (TiO2) photocatalysts for ethylene decomposition, titanium (Ti) thin film samples with fiberform nanostructures were prepared by helium (He) plasma treatment. Then, the oxidation condition for ethylene decomposition were optimized in terms of the oxidation temperature and duration. It is shown that He plasma irradiation with Ti deposition followed by oxidation in the air formed anatase-rich TiO2. The rutile anatase transition temperature increased to higher than 1000 K on the He treated samples and the best photocatalytic performance is twice higher than that on TiO2 sample formed in a magnetron sputtering device. Helium plasma treatment induces vacancies, He clusters, and He bubbles together with formation of nanostructures. The results suggested that those morphology changes lead to the formation of stable anatase structure, which is likely the key factor for the enhancement of photocatalytic activity. Based on the obtained ethylene decomposition rate, we will discuss the necessary light source and amount of photocatalysts to keep vegetables fresh in a long-distance transport cargo.

DOI： 10.1016/j.jphotochem.2021.113420

Scopus

Thermal treatment of W large-scale fiberform nanostructures 査読有り

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

PHYSICA SCRIPTA 96 巻 ( 9 ) 2021年9月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Physica Scripta

Recent experiments have revealed that accelerated tungsten (W) nanostructure growth occurs during the exposure to helium (He) plasmas with an additional W deposition, and mm-thick large-scale fiberform nanostructures (LFNs) are formed when certain condition is satisfied. In order to reveal whether accelerated growth occurs in fusion device, it is important to understand the annealing process in addition to the growth process. In this study, we will perform thermal treatment of W LFNs. Detailed observation reveals that the LFNs shrink at a faster rate than that of conventional fuzz, though it takes longer time to fully be reintegrated to the surface because the thickness is orders of magnitude greater.

DOI： 10.1088/1402-4896/ac0866

Web of Science

Scopus

Enhancement of Arc Ignition on Tungsten in Helium Plasmas with Impurity Gases 査読有り国際共著

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

Plasma and Fusion Research 16 巻 ( 0 ) 頁： 24045069(5 pp) - 2405069 2021年5月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人プラズマ・核融合学会

Arcing was ignited on deformed tungsten (W) surfaces, where W fuzz and/or nano-tendril bundles (NTBs) were grown, by steady state helium (He) plasma exposures with impurity gas seeding. At the same sample potential of −250 V, the presence of NTBs enhanced the frequency of arc ignition, whereas no arc ignition appeared on typical fuzz surfaces without NTBs. After a series of arc ignitions on a sample surface with NTBs, the aspect ratio of NTBs decreased, indicating that protruded NTBs with larger aspect ratio tend to trigger arcing easily.

DOI： 10.1585/pfr.16.2405069

Scopus

Modeling of the impurity-induced silicon nanocone growth by low energy helium plasma irradiation 査読有り国際共著

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

Plasma Science and Technology 23 巻 ( 4 ) 頁： 45503 2021年4月

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

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 16 巻 ( 0 ) 頁： 2402041 - 2402041 2021年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人プラズマ・核融合学会

Influences of nitrogen ratio on plasma detachment and molecular activated recombination (MAR) processes during combined seeding with hydrogen have been investigated utilizing end-loss plasma in the GAMMA 10/PDX tandem mirror. Additional gases were injected under the condition that hydrogen partial pressure was fixed and nitrogen partial pressure was changed from 0% - 10% compared to that of hydrogen. Electron density and ion flux further decrease with increasing nitrogen ratio. In addition, it is suggested that the hydrogen-MAR process that begins with dissociative attachment is suppressed during combined seeding of nitrogen and hydrogen. Observed emission spectrum of NH radicals suggests that the density of NH increases as nitrogen ratio increases and nitrogen-induced MAR efficiently contributes to the reduction of particle flux.

DOI： 10.1585/pfr.16.2402041

Scopus

Computer Tomography on Divertor Impurity Monitor for ITER with Minimizing Errors in a Logarithmic Scale 招待有り査読有り国際共著

NATSUME Hiroki, OGAWA Hiroaki, KITAZAWA Sin-iti, KAJITA Shin, NEVEROV Vladislav S., KHUSNUTDINOV Radmir I., VESHCHEV Evgeny, DE BOCK Maarten, POLEVOI Alexei R., TANAKA Hirohiko, OHNO Noriyasu

Plasma and Fusion Research 16 巻 ( 0 ) 頁： 2405019 - 2405019 2021年3月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人プラズマ・核融合学会

The computer tomography for divertor impurity monitor, which measures plasma emissions in the divertor region, for ITER has been conducted using a ray-tracing technique. We have attempted four different solution methods for the inversion problem and compared the results. The solution methods which minimize errors in logarithmic scale had better performance than the methods which minimize errors in linear scale. This is likely due to the fact that the values in the emission profile vary in a wide range of orders of magnitude. The accuracy of the reconstruction has been investigated by changing discharge conditions and the number of field-of-views used. The deterioration in accuracy was most noticeable when the emission profile was reconstructed using only two field-of-views. In addition, the accuracy deteriorated, making the estimation more challenging, under discharge conditions with low emission intensity because of the wider range of emission intensity under such conditions.

DOI： 10.1585/pfr.16.2405019

Scopus

Particle-in-cell-Monte Carlo collision simulation and experimental measurement of Ar plasma in a fast atom beam source for surface-activated bonding 査読有り国際誌

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

Japanese Journal of Applied Physics 60 巻 ( SC ) 頁： SCCB01 2021年3月

Doppler and Stark Broadenings of He II Emission in NAGDIS-PG 招待有り査読有り

KAJITA Shin, NAKAMORI Takaya, TANAKA Hirohiko, KIKUCHI Yusuke, OHNO Noriyasu

Plasma and Fusion Research 16 巻 ( 0 ) 頁： 1202013 - 1202013 2021年2月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人プラズマ・核融合学会

Time evolutions of the emission from helium (He) ion at 468.6 nm were observed in the magnetized co-axial plasma gun device NAGDIS-PG, and the broadening of the spectrum was analyzed in terms of Doppler and Stark broadenings to deduce the ion temperature and the electron density. A significant broadening of the He II spectrum was identified around a dip in the discharge current, suggesting that increases in the temperature and density occurred.

DOI： 10.1585/pfr.16.1202013

Scopus

Fabrication of nanostructured Ti thin film with Ti deposition in He plasmas 査読有り

Miyaguchi Kazuya, Kajita Shin, Tanaka Hirohiko, Ohno Noriyasu

JAPANESE JOURNAL OF APPLIED PHYSICS 60 巻 ( 3 ) 頁： 038004(4 pp) 2021年2月

Accelerated/reduced growth of tungsten fuzz by deposition of metals 査読有り国際共著

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

Journal of Nuclear Materials 548 巻頁： 152844 2021年1月

Tungsten Large-Scale Fiberform Nanostructures Retained under High Temperature Conditions 査読有り

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

PLASMA AND FUSION RESEARCH 16 巻頁： 1206001 2021年1月

Experimental observations and modelling of radiation asymmetries during N<inf>2</inf> seeding in LHD 査読有り国際共著

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 26 巻頁： 100848 2020年12月

Experimental observations and modelling of radiation asymmetries during Ne and N2 seeding in LHD 招待有り査読有り国際共著

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 26 巻頁： 100848 2020年12月