研究者詳細 - 清水　裕彦

超流動4He中の流れ場可視化にむけた中性子3He吸収反応による4He励起分子集団生成の実証

松下琢, Volker Sonnenschein, 井口哲夫, 伊藤大介, 北口雅暁, 鬼柳善明, Wei Guo, 齊藤泰司, 篠原武尚, 清水裕彦, 鈴木颯, 辻義之, 富田英生, 林田洋寿, 菱田真由, 廣井孝介, 広田克也, 丸山巧, 脇慎一郎, 和田信雄

波紋 30 巻 ( 4 ) 頁： 192 - 196 2020年11月

A Multi-Center Contouring Study of Spinal Cord Comparing MRI and Myelo-CT Fusion Open Access

Tanaka H., Aoyama T., Shimizu H., Tachibana H., Koide Y., Miyauchi R., Wakabayashi K., Ooshima Y., Adachi S., Kozai Y., Kodaira T.

INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS 108 巻 ( 3 ) 頁： E377 - E377 2020年11月

Development and application of a 3He Neutron Spin Filter at J-PARC Open Access

Okudaira T., Oku T., Ino T., Hayashida H., Kira H., Sakai K., Hiroi K., Takahashi S., Aizawa K., Endo H., Endo S., Hino M., Hirota K., Honda T., Ikeda K., Kakurai K., Kambara W., Kitaguchi M., Oda T., Ohshita H., Otomo T., Shimizu H.M., Shinohara T., Suzuki J., Yamamoto T.

Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 977 巻 2020年10月

記述言語：日本語出版者・発行元：Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment

We are developing a neutron polarizer with polarized 3He gas, referred to as a 3He spin filter, based on the Spin Exchange Optical Pumping (SEOP) for polarized neutron scattering experiments at Materials and Life Science Experimental Facility (MLF) of Japan Proton Accelerator Research Complex (J-PARC). A 3He gas-filling station was constructed at J-PARC, and several 3He cells with long spin relaxation times have been fabricated using the gas-filling station. A laboratory has been prepared in the MLF beam hall for polarizing 3He cells, and compact pumping systems with laser powers of 30 W and 110 W, which can be installed onto a neutron beamline, have been developed. A 3He polarization of 85% was achieved at a neutron beamline by using the pumping system with the 110 W laser. Recently, the first user experiment utilizing the 3He spin filter was conducted, and there have been several more since then. The development and utilization of 3He spin filters at MLF of J-PARC are reported.

DOI： 10.1016/j.nima.2020.164301

A candidate secular variation model for IGRF-13 based on MHD dynamo simulation and 4DEnVar data assimilation Open Access

Minami Takuto, Nakano Shin'ya, Lesur Vincent, Takahashi Futoshi, Matsushima Masaki, Shimizu Hisayoshi, Nakashima Ryosuke, Taniguchi Hinami, Toh Hiroaki

EARTH PLANETS AND SPACE 72 巻 ( 1 ) 2020年9月

記述言語：日本語出版者・発行元：Earth, Planets and Space

We have submitted a secular variation (SV) candidate model for the thirteenth generation of International Geomagnetic Reference Field model (IGRF-13) using a data assimilation scheme and a magnetohydrodynamic (MHD) dynamo simulation code. This is the first contribution to the IGRF community from research groups in Japan. A geomagnetic field model derived from magnetic observatory hourly means, and CHAMP and Swarm-A satellite data, has been used as input data to the assimilation scheme. We adopt an ensemble-based assimilation scheme, called four-dimensional ensemble-based variational method (4DEnVar), which linearizes outputs of MHD dynamo simulation with respect to the deviation from a dynamo state vector at an initial condition. The data vector for the assimilation consists of the poloidal scalar potential of the geomagnetic field at the core surface and flow velocity field slightly below the core surface. Dimensionless time of numerical geodynamo is adjusted to the actual time by comparison of secular variation time scales. For SV prediction, we first generate an ensemble of dynamo simulation results from a free dynamo run. We then assimilate the ensemble to the data with a 10-year assimilation window through iterations, and finally forecast future SV by the weighted sum of the future extension parts of the ensemble members. Hindcast of the method for the assimilation window from 2004.50 to 2014.25 confirms that the linear approximation holds for 10-year assimilation window with our iterative ensemble renewal method. We demonstrate that the forecast performance of our data assimilation and forecast scheme is comparable with that of IGRF-12 by comparing data misfits 4.5 years after the release epoch. For estimation of our IGRF-13SV candidate model, we set assimilation window from 2009.50 to 2019.50. We generate our final SV candidate model by linear fitting for the weighted sum of the ensemble MHD dynamo simulation members from 2019.50 to 2025.00. We derive errors of our SV candidate model by one standard deviation of SV histograms based on all the ensemble members.[Figure not available: see fulltext.].

DOI： 10.1186/s40623-020-01253-8

Fluorescence Imaging of He2* Excimers generated by neutron and gamma irradiation of superfluid Helium using a cold neutron beamline at J-PARC / MLF

Sonnenschein Volker Thomas, Matsushita Taku, Tsuji Yoshiyuki, Guo Wei, Hayashida Hiroshi, Hirota Katsuya, Kosuke Hiroi, Maruyama Takumi, Hishida Mayu, Tomita Hideki, Ito Daisuke, Kitaguchi Masaaki, Kiyanagi Yoshiaki, Sou Suzuki, Saito Yasushi, Shimizu Hirohiko, Shinohara Takenao, Wada Nobuo

JSAP Annual Meetings Extended Abstracts 2020.2 巻 ( 0 ) 頁： 287 - 287 2020年8月

3-D Intrinsic and Scattering Seismic Attenuation Structures Beneath Kyushu, Japan Open Access

Shito A., Matsumoto S., Ohkura T., Shimizu H., Sakai S., Iio Y., Takahashi H., Yakiwara H., Watanabe T., Kosuga M., Okada T., Yoshimi M., Asano Y.

JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH 125 巻 ( 8 ) 2020年8月

記述言語：日本語出版者・発行元：Journal of Geophysical Research: Solid Earth

The attenuation of seismic wave energy is caused by intrinsic absorption and scattering. The former involves the conversion of seismic wave energy to heat energy via internal friction due to the anelasticity of the medium, whereas the latter involves the scattering of seismic wave energy due to random elastic heterogeneities in the medium. Quantifying both intrinsic ((Formula presented.)) and scattering ((Formula presented.)) attenuation is therefore important for understanding the physical properties of the Earth's interior and predicting seismic wave propagation. Here we develop a new procedure to separately map three-dimensional (3-D) (Formula presented.) and (Formula presented.) structures. The path-averaged (Formula presented.) and (Formula presented.) values are obtained via an envelope-fitting approach that employs a multiple-scattering model. The path-averaged (Formula presented.) and (Formula presented.) structures are then mapped into 3-D space using a tomographic inversion technique based on sensitivity kernels, which are calculated from a Monte Carlo simulation of the radiative transfer equations. We apply this method to map the crustal structure beneath Kyushu, Japan, and obtain 3-D (Formula presented.) and (Formula presented.) structures for the 1–2, 2–4, and 4–8 Hz frequency bands. The spatial attenuation patterns are similar for each of the analyzed frequency bands, with the spatial variability in (Formula presented.) being more pronounced than that in (Formula presented.). The high- (Formula presented.) and (Formula presented.) regions correspond to the locations of active volcanoes. Conversely, the northern Kyushu area possesses low- (Formula presented.) and (Formula presented.) zones that correspond to low heat flow and Cretaceous granite, respectively. The overall (Formula presented.) and (Formula presented.) distributions correlate with thermal and geological structures, respectively.

DOI： 10.1029/2019JB018742

Neutron spin dynamics in polarized targets Open Access

Gudkov V., Shimizu H.M.

Physical Review C 102 巻 ( 1 ) 2020年7月

記述言語：日本語出版者・発行元：Physical Review C

We present the neutron elastic scattering amplitude for an arbitrarily polarized target in an irreducible spherical-tensor representation. The general approach for the description of neutron spin dynamics for propagation through the medium with an arbitrary polarization is discussed in relation to the search for a time-reversal invariance violation in neutron scattering.

DOI： 10.1103/PhysRevC.102.015503

Transverse asymmetry of γ rays from neutron-induced compound states of La 140 Open Access

Yamamoto T., Okudaira T., Endo S., Fujioka H., Hirota K., Ino T., Ishizaki K., Kimura A., Kitaguchi M., Koga J., Makise S., Niinomi Y., Oku T., Sakai K., Shima T., Shimizu H.M., Takada S., Tani Y., Yoshikawa H., Yoshioka T.

Physical Review C 101 巻 ( 6 ) 2020年6月

記述言語：日本語出版者・発行元：Physical Review C

An sp-mixing model, which describes a compound nuclear reaction by mixing partial waves, predicts a correlation term in this reaction. A detailed study of the sp-mixing model is required to study the feasibility of a new type of time reversal symmetry violation search experiment. The correlation term σn·(kn×kγ) in the La139(n - ,γ) reaction has been studied by measuring γ-ray and neutron energies utilizing epithermal polarized neutrons and germanium detectors. The transverse asymmetry for single γ-ray transition was measured to be 0.60±0.19 in the p-wave resonance.

DOI： 10.1103/PhysRevC.101.064624

An experimental setup for creating and imaging 4 He 2∗ excimer cluster tracers in superfluid helium-4 via neutron-3He absorption reaction

Sonnenschein V., Tsuji Y., Kokuryu S., Kubo W., Suzuki S., Tomita H., Kiyanagi Y., Iguchi T., Matsushita T., Wada N., Kitaguchi M., Shimizu H.M., Hirota K., Shinohara T., Hiroi K., Hayashida H., Guo W., Ito D., Saito Y.

Review of Scientific Instruments 91 巻 ( 3 ) 2020年3月

記述言語：日本語出版者・発行元：Review of Scientific Instruments

For the purpose of future visualization of the flow field in superfluid helium-4, clusters of the triplet state excimer 4He<inf>2</inf>* are generated along the micro-scale recoil tracks of the neutron-absorption reaction n + 3He → 3T + p. This reaction is induced by neutron irradiation of the 3He fraction contained in natural isotopic abundance liquid helium with neutron beams either from the Japan Proton Accelerator Research Complex, Materials and Life Science Experimental Facility (JPARC)/Materials and Life Science Experimental Facility or from the Kyoto University Institute for Integrated Radiation and Nuclear Science. These 4He<inf>2</inf>* clusters are expected to be ideal tracers of the normal-fluid component in superfluid helium with several advantageous properties. Evidence of the excimer generation is inferred by detection of laser induced fluorescence emitted from the 4He<inf>2</inf>* clusters excited by a purpose-built short pulse gain-switched titanium:sapphire (Ti:sa) laser operating at a wavelength of 905 nm. The setup and performance characteristics of the laser system including the Ti:sa and two continuous wave re-pumping lasers are described. Detection at the fluorescence wavelength of 640 nm is performed by using optical bandpass filtered photomultiplier tubes (PMT). Electrical noise in the PMT acquisition traces could successfully be suppressed by post-processing with a simple algorithm. Despite other laser-related backgrounds, the excimer was clearly identified by its fluorescence decay characteristics. Production of the excimer was found to be proportional to the neutron flux, adjusted via insertion of different collimators into the neutron beam. These observations suggest that the apparatus we constructed does function in the expected manner and, therefore, has the potential for groundbreaking turbulence research with superfluid helium.

DOI： 10.1063/1.5130919