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Tokiwa, Yoshifumi; Sakai, Hironori; Kambe, Shinsaku; Opletal, P.; Yamamoto, Etsuji; Kimata, Motoi*; Awaji, Satoshi*; Sasaki, Takahiko*; Yanase, Yoichi*; Haga, Yoshinori; et al.
Physical Review B, 108(14), p.144502_1 - 144502_5, 2023/10
Times Cited Count：0The vortex dynamics in the spin-triplet superconductor, UTe, are studied by measuring the DC electrical resistivity with currents along the 
-axis under magnetic fields along the 
-axis. Surprisingly, we have discovered an island region of low critical current deep inside the superconducting (SC) state, well below the SC upper critical field, attributed to a weakening of vortex pinning. Notably, this region coincides with the recently proposed intermediate-field SC state. We discuss the possibility of nonsingular vortices in the intermediate state, where SC order parameter does not vanish entirely in the vortex cores due to the mixing of multiple SC components.
Takayama, Yusuke; Yamamoto, Yoichi*; Goto, Takahiro*
Jiban Kogaku Janaru (Internet), 18(3), p.317 - 330, 2023/09
It has been reported that the deformation greatly increased in the secondary consolidation process in the past long-term consolidation test of 1.8 years on Na-type bentonite/sand mixed soil. Therefore, we analyzed potential contributing factors in this behavior. A long-term consolidation test for about 10 years on bentonite and kaolinite was started using the test equipment with countermeasures against these factors. In this paper, the secondary consolidation behavior of bentonite was investigated based on the long-term consolidation test data for 2.7, 3.7 and 4 years. The results were generally consistent with the conventional findings on soil mechanics that the deformation due to secondary consolidation progresses linearly with respect to logarithm of time. This test will be continued for about 10 years and longer-term secondary consolidation behavior will be investigated.
Tada, Kenichi; Kondo, Ryoichi; Endo, Tomohiro*; Yamamoto, Akio*
Journal of Nuclear Science and Technology, 60(6), p.624 - 631, 2023/06
Times Cited Count：2 Percentile：53.91(Nuclear Science & Technology)The sensitivity analysis and the uncertainty quantification have an important role in improving the evaluated nuclear data library. The current computational performance enables us to the sensitivity analysis and uncertainty quantification using the continuous energy Monte Carlo calculation code. The ACE file perturbation tool was developed for these calculations using modules of FRENDY. This tool perturbs the microscopic cross section, the number of neutrons per fission, and the fission spectrum. The uncertainty quantification using the random sampling method is also available if the user prepares the covariance matrix. The uncertainty of the k-effective using the perturbation tool was compared to the current sensitivity analysis codes SCALE/TSUNAMI and MCNP/KSEN. The comparison results indicated that the random sampling method using this tool accurately estimates the uncertainty of k-effective.
Takayanagi, Tomohiro; Ono, Ayato; Fuwa, Yasuhiro; Shinozaki, Shinichi; Horino, Koki*; Ueno, Tomoaki*; Sugita, Moe; Yamamoto, Kazami; Oguri, Hidetomo; Kinsho, Michikazu; et al.
Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.242 - 246, 2023/01
At J-PARC, semiconductor short pulse power supplies to replace kicker power supplies and semiconductor long pulse power supplies to replace klystron power supply systems are under construction. We have fabricated a 40kV/2kA/1.2
s unit power supply that employs a linear transformer drivers (LTD) system for kickers. Currently, we are working on a high voltage insulating cylinder insulator that suppresses corona discharges using only the insulator structure, without using insulating oil. In addition, the MARX system was adopted for klystron power supply system. A main circuit unit for 8kV/60A/830s rectangular pulse output and an 800V/60A correction circuit unit that improves the flat top droop from 10% to 1% were manufactured. Furthermore, a 2.2kV/2.4kW high voltage SiC inverter charger has been fabricated for this MARX power supply. The presentation will report the evaluation results of each test and prospects for semiconductor pulse power supplies.
Tada, Kenichi; Yamamoto, Akio*; Kunieda, Satoshi; Konno, Chikara; Kondo, Ryoichi; Endo, Tomohiro*; Chiba, Go*; Ono, Michitaka*; Tojo, Masayuki*
Journal of Nuclear Science and Technology, 10 Pages, 2023/00
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)Nuclear data processing code is important to connect evaluated nuclear data libraries and radiation transport codes. The nuclear data processing code FRENDY version 1 was released in 2019 to generate ACE formatted cross section files with simple input data. After we released FRENDY version 1, many functions were developed, e.g., neutron multi-group cross section generation, explicit consideration of the resonance interference effect among different nuclides in a material, consideration of the resonance upscattering, ACE file perturbation, and modification of ENDF-6 formatted file. FRENDY version 2 was released including these new functions. It generates GENDF and MATXS formatted neutron multi-group cross section files from an ACE formatted cross section file or an evaluated nuclear data file. This paper explains the features of the new functions implemented in FRENDY version 2 and the verification of the neutron multigroup cross section generation function of this code.
Yamamoto, Yoichi*; Ogawa, Yusuke*; Kobayashi, Masato*; Takayama, Yusuke; Nishimoto, Soshi*
Nihon Genshiryoku Gakkai-Shi ATOMO
, 64(2), p.105 - 109, 2022/02
no abstracts in English
Ishitsuka, Etsuo; Mitsui, Wataru*; Yamamoto, Yudai*; Nakagawa, Kyoichi*; Ho, H. Q.; Ishii, Toshiaki; Hamamoto, Shimpei; Nagasumi, Satoru; Takamatsu, Kuniyoshi; Kenzhina, I.*; et al.
JAEA-Technology 2021-016, 16 Pages, 2021/09
JAEA-Technology-2021-016.pdf:1.8MB
As a summer holiday practical training 2020, the feasibility study for nuclear design of a nuclear battery using HTTR core was carried out, and the downsizing of reactor core were studied by the MVP-BURN. As a result, it is clear that a 1.6 m radius reactor core, containing 54 (18
3 layers) fuel blocks with 20% enrichment of 
U, and BeO neutron reflector, could operate continuously for 30 years with thermal power of 5 MW. Number of fuel blocks of this compact core is 36% of the HTTR core. As a next step, the further downsizing of core by changing materials of the fuel block will be studied.
O
by 
inelastic neutron scattering and their reactivity with ethyleneYamazoe, Seiji*; Yamamoto, Akira*; Hosokawa, Saburo*; Fukuda, Ryoichi*; Hara, Kenji*; Nakamura, Mitsutaka; Kamazawa, Kazuya*; Tsukuda, Tatsuya*; Yoshida, Hisao*; Tanaka, Tsunehiro*
Catalysis Science & Technology, 11(1), p.116 - 123, 2021/01
Times Cited Count：6 Percentile：34.43(Chemistry, Physical)
-electron state of the heavy fermion superconductor NpPd
Al and the isostructural familyMetoki, Naoto; Aczel, A. A.*; Aoki, Dai*; Chi, S.*; Fernandez-Baca, J. A.*; Griveau, J.-C.*; Hagihara, Masato*; Hong, T.*; Haga, Yoshinori; Ikeuchi, Kazuhiko*; et al.
JPS Conference Proceedings (Internet), 30, p.011123_1 - 011123_6, 2020/03
Rare earths (4) and actinides (5) provide variety of interesting states realized with competing interactions between the increasing number of electrons. Since crystal field splitting of many-body electron system is smaller than the bandwidth, (1) high resolution experiments are needed, (2) essentially no clear spectrum with well defined peaks is expected in itinerant Ce and U compounds, and (3) Np and Pu is strictly regulated. Therefore, systematic research on magnetic excitations by neutron scattering experiments of localized compounds and rare earth iso-structural reference is useful. We describe the electron states of heavy electron compounds NpPdAl and actinide and rare earth based iso-structural family.
Kondo, Ryoichi*; Endo, Tomohiro*; Yamamoto, Akio*; Tada, Kenichi
Proceedings of International Conference on Mathematics and Computational Methods applied to Nuclear Science and Engineering (M&C 2019) (CD-ROM), p.1493 - 1502, 2019/00
A perturbation capability of ACE formatted cross section files was developed using the modules of FRENDY. Uncertainty quantification using MCNP was carried out for the Godiva critical experiment by the RS method. We verified the results of the RS method by comparing with those obtained by the conventional sensitivity analyses. Moreover, uncertainty reduction using the bias factor method with the RS technique was applied to kinetic parameter, i.e., neutron generation time.
Kijima, Yuichi; Yamamoto, Yoichi; Oda, Tetsuzo
JAEA-Technology 2017-028, 33 Pages, 2018/01
JAEA-Technology-2017-028.pdf:38.85MB
The International Noble Gas Experiment related to monitoring network for radioactive noble gas (xenon) has been carried out all over the world, as part of the International Monitoring System (IMS) of CTBT. Thirty IMS radionuclide stations including the Takasaki station in Japan are monitoring radioxenon. The past measurement results show that several stations often detect radioxenon and the major emission source of these radioxenon is medical radioisotope production facilities. And nuclear power plants and medical institutions used radioxenon for nuclear medicine diagnosis, and so on are also considered as the possible sources of radioxenon, and it is therefore important to understand the background behavior of radioxenon originated from above facilities for enhancement of monitoring capability for nuclear tests. The international joint measurement was conducted in 2012 by the Preparatory Commission for the CTBT Organization, US Pacific Northwest National Laboratory, Japan Chemical Analysis Center and JAEA at the Ohminato site of JAEA Aomori Research and Development Center in Mutsu city, Aomori, as part of investigation on radioxenon background in East Asia region. In 2014, the additional measurement was carried out at the same place for further investigation. A high sensitive Transportable Xenon Laboratory developed by PNNL was used for this measurement. This paper describes the outline and the results of the joint measurement conducted in 2012 and 2014.
Takayanagi, Tomohiro; Kinsho, Michikazu; Yamamoto, Kazami; Ueno, Tomoaki*; Horino, Koki*; Tokuchi, Akira*; Mushibe, Yoichi*
Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.45 - 49, 2017/12
J-PARC RCS needs updating of equipment after 10 years since the start of operation. Therefore, a pulse power supply applying a next generation semiconductor (SiC-MOSFET) with low switching loss and high breakdown voltage are investigated This supply constructs a serial / parallel multiplexing circuit using a SiC-MOSFET and a plurality of large capacity capacitors with one circuit board (LTD). By using this board as a main board and adopting a multistage hierarchical structure, it is possible to satisfy the specifications of the RCS kicker power supply with a voltage of 40 kV, a current of 4 kA and a rectangular wave pulse width of 1500 ns. Moreover, by adding a plurality of correction boards of 40 V and arbitrarily setting the operation trigger of the board, flatness correction is also possible. It was confirmed that the results of the preliminary test with the maximum output of 4 kV / 2 kA by are effective for maintaining stable operation at the RCS high intensity beam output.
Hasegawa, Kazuo; Kinsho, Michikazu; Oguri, Hidetomo; Yamamoto, Kazami; Hayashi, Naoki; Yamazaki, Yoshio; Naito, Fujio*; Hori, Yoichiro*; Yamamoto, Noboru*; Koseki, Tadashi*
Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1317 - 1321, 2017/12
After the summer shutdown in 2016, the J-PARC restarted user operation late in October for the neutrino experiments (NU) and early in November for the materials and life science experimental facility (MLF). The beam power for the NU was 420 kW in May 2016, but increased to 470 kW in February 2017 thanks to the change and optimization of operation parameters. For the hadron experimental facility (HD), we started beam tuning in April, but suspended by a failure of the electro static septum. After the treatment, we delivered beam at the power of 37 kW. We delivered beam at 150kW for the MLF. In the fiscal year of 2016, the linac, the 3 GeV synchrotron (RCS) and the MLF were stable and the availability was high at 93%. On the contrary, the main ring has several failures and the availabilities were 77% and 84% for NU and HD, respectively.
Hasegawa, Kazuo; Hayashi, Naoki; Oguri, Hidetomo; Yamamoto, Kazami; Kinsho, Michikazu; Yamazaki, Yoshio; Naito, Fujio*; Koseki, Tadashi*; Yamamoto, Noboru*; Hori, Yoichiro*
Proceedings of 8th International Particle Accelerator Conference (IPAC '17) (Internet), p.2290 - 2293, 2017/06
The J-PARC is a high intensity proton facility and the accelerator consists of a 400 MeV linac, a 3 GeV Rapid Cycling Synchrotron (RCS) and a 30 GeV Main Ring Synchrotron (MR). We have taken many hardware upgrades such as front end replacement and energy upgrade at the linac, vacuum improvement, collimator upgrade, etc. The beam powers for the neutrino experiment and hadron experiment from the MR have been steadily increased by tuning and reducing beam losses. The designed 1 MW equivalent beam was demonstrated and user program was performed at 500 kW from the RCS to the neutron and muon experiments. We have experienced many failures and troubles, however, to impede full potential and high availability. In this report, operational performance and status of the J-PARC accelerators are presented.
Tani, Norio; Watanabe, Yasuhiro; Hotchi, Hideaki; Harada, Hiroyuki; Yamamoto, Masanobu; Kinsho, Michikazu; Igarashi, Susumu*; Sato, Yoichi*; Shirakata, Masashi*; Koseki, Tadashi*
Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.708 - 711, 2016/11
At the J-PARC Main Ring (MR), there have been various investigation carried out at the moment aiming at the beam operation of MW order. As one of the investigations, a study of the Rapid-Cycling Synchrotron (RCS) magnets was implemented. Increase of the extraction energy of RCS was needed to reduce beam loss, as beam loss in the MR injection region was large under influence of Space Charge effect at the injection beam of 3GeV. Therefore conceptual design of the extraction energy upgrade using dipole and quadrupole magnets of RCS was performed. In this paper, we will report the contents of the study in extraction energy upgrade of RCS magnets and problems which became clear as a result.
Yamamoto, Keita*; Shiomi, Yuki*; Segawa, Koji*; Ando, Yoichi*; Saito, Eiji
Physical Review B, 94(2), p.024404_1 - 024401_6, 2016/05
Times Cited Count：17 Percentile：61.21(Materials Science, Multidisciplinary)We have investigated spin-electricity conversion on surface states of bulk-insulating topological insulator (TI) materials using a spin-pumping technique. The sample structure is Ni-Fe/Cu/TI trilayers, in which magnetic proximity effects on the TI surfaces are negligibly small owing to the inserted Cu layer. Voltage signals produced by the spin-electricity conversion are clearly observed and are enhanced with decreasing temperature, in line with the dominant surface transport at lower temperatures. The efficiency of the spin-electricity conversion is greater for TI samples with a higher resistivity of bulk states and longer mean free path of surface states, consistent with the surface spin-electricity conversion.
Kijima, Yuichi; Yamamoto, Yoichi
Nihon Genshiryoku Gakkai-Shi ATOMO, 58(3), p.156 - 160, 2016/03
JAEA has built and operated two radionuclide stations and a certified laboratory for monitoring of radionuclide out of facilities of the International Monitoring System (IMS) under the CTBT National Operation System of Japan. JAEA also has developed and operated the National Data Center for analysis and evaluation of radionuclide observation data obtained from the IMS station. In this paper, we explain the outline of the CTBT and the CTBT activities of JAEA, and introduce two examples of detection of some anthropogenic radionuclides including the monitoring case for the DPRK's 3rd nuclear test in February 2013 from all observational results obtained from the CTBT radionuclide stations in Japan.
Hotchi, Hideaki; Harada, Hiroyuki; Yamamoto, Masanobu; Igarashi, Susumu*; Koseki, Tadashi*; Sato, Yoichi*
JPS Conference Proceedings (Internet), 8, p.012008_1 - 012008_6, 2015/09
Now the J-PARC accelerators (Linac, 3GeV RCS, 50GeV MR) are in transition from the initial beam commissioning phase to the final stage aiming for the design output beam power of 1 MW from RCS and 0.75 MW from MR; RCS is to start 1-MW beam tuning from October 2014 after completing the linac upgrade, and MR aims at 0.75 MW within the next 3 years by introducing new main magnet power supplies with the faster cycling time. In view of such current situation, we have started discussions for the future J-PARC accelerator concept toward a Multi-MW output beam power. In this paper, we discuss the feasibility for the introduction of a new 8-GeV booster synchrotron between RCS and MR as one possible option toward a Multi-MW output beam power from MR, in combination with the RCS beam power upgrade from 1 MW to 2 MW.
Nishimori, Nobuyuki; Nagai, Ryoji; Mori, Michiaki; Hajima, Ryoichi; Yamamoto, Masahiro*; Honda, Yosuke*; Miyajima, Tsukasa*; Uchiyama, Takashi*; Jin, X.*; Obina, Takashi*; et al.
Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.511 - 515, 2015/09
no abstracts in English
Yamamoto, Yoichi
Isotope News, (736), p.31 - 33, 2015/08
The Takasaki radionuclide (RN) station for the Comprehensive Nuclear-Test-Ban Treaty (CTBT) has been in operation for monitoring of radioactive noble gases (radioxenon) by the Japan Atomic Energy Agency (JAEA) since 2007, first as a test run prior to receiving the certification. The noble gas system in the station was certified by the CTBT Organization (CTBTO) on December 19, 2014. Monitoring of radioxenon is expected to have a particularly valuable role in detection of an underground nuclear test. The Takasaki RN station detected radioxenon isotopes simultaneously with radioactive concentration exceeding normal background range in April, 2013. This abnormal event was identified as being associated with the nuclear test declared by North Korea in February, 2013. Since the Takasaki RN station is located at the east end of Asia, it is receiving widespread international attention as the station for radionuclides dispersed by the westerlies.
