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Journal Articles

A Large modulation of spin pumping using magnetic phase transitions in single crystalline dysprosium

Yamanoi, Kazuto*; Sakakibara, Yuri*; Fujimoto, Junji*; Matsuo, Mamoru; Nozaki, Yukio*

Applied Physics Express, 16(6), p.063004_1 - 063004_6, 2023/06

Journal Articles

Skyrmion creation and annihilation by electric current vorticity

Fujimoto, Junji*; Funaki, Hiroshi*; Koshibae, Wataru*; Matsuo, Mamoru; Maekawa, Sadamichi*

IEEE Transactions on Magnetics, 58(8), p.1500407_1 - 1500407_7, 2022/08

Journal Articles

Repeatable photoinduced insulator-to-metal transition in yttrium oxyhydride epitaxial thin films

Komatsu, Yuya*; Shimizu, Ryota*; Sato, Ryuhei*; Wilde, M.*; Nishio, Kazunori*; Katase, Takayoshi*; Matsumura, Daiju; Saito, Hiroyuki*; Miyauchi, Masahiro*; Adelman, J. R.*; et al.

Chemistry of Materials, 34(8), p.3616 - 3623, 2022/04

 Times Cited Count:6 Percentile:73.76(Chemistry, Physical)

Journal Articles

Zeeman coupling and Dzyaloshinskii-Moriya interaction driven by electric current vorticity

Fujimoto, Junji*; Koshibae, Wataru*; Matsuo, Mamoru; Maekawa, Sadamichi

Physical Review B, 103(22), p.L220402_1 - L220402_5, 2021/06

 Times Cited Count:4 Percentile:38.22(Materials Science, Multidisciplinary)

Journal Articles

Visualizing cation vacancies in Ce:Gd$$_{3}$$Al$$_{2}$$Ga$$_{3}$$O$$_{12}$$ scintillators by gamma-ray-induced positron annihilation lifetime spectroscopy

Fujimori, Kosuke*; Kitaura, Mamoru*; Taira, Yoshitaka*; Fujimoto, Masaki*; Zen, H.*; Watanabe, Shinta*; Kamada, Kei*; Okano, Yasuaki*; Kato, Masahiro*; Hosaka, Masahito*; et al.

Applied Physics Express, 13(8), p.085505_1 - 085505_4, 2020/08

 Times Cited Count:4 Percentile:27.19(Physics, Applied)

To clarify the existence of cation vacancies in Ce-doped Gd$$_{3}$$Al$$_{2}$$Ga$$_{3}$$O$$_{12}$$ (Ce:GAGG) scintillators, we performed gamma-ray-induced positron annihilation lifetime spectroscopy (GiPALS). GiPAL spectra of GAGG and Ce:GAGG comprised two exponential decay components, which were assigned to positron annihilation at bulk and defect states. By an analogy with Ce:Y$$_{3}$$Al$$_{5}$$O$$_{12}$$, the defect-related component was attributed to Al/Ga-O divacancy complexes. This component was weaker for Ce, Mg:GAGG, which correlated with the suppression of shallow electron traps responsible for phosphorescence. Oxygen vacancies were charge compensators for Al/Ga vacancies. The lifetime of the defect-related component was significantly changed by Mg co-doping. This was understood by considering aggregates of Mg$$^{2+}$$ ions at Al/Ga sites with oxygen vacancies, which resulted in the formation of vacancy clusters.

Journal Articles

Magnon current generation by dynamical distortion

Fujimoto, Junji*; Matsuo, Mamoru

Physical Review B, 102(2), p.020406_1 - 020406_5, 2020/07

Journal Articles

Alternating current-induced interfacial spin-transfer torque

Fujimoto, Junji*; Matsuo, Mamoru

Physical Review B, 100(22), p.220402_1 - 220402_5, 2019/12

 Times Cited Count:1 Percentile:4.85(Materials Science, Multidisciplinary)

Journal Articles

Simultaneous recovery and separation of rare earth elements in ferromanganese nodules by using ${{it Shewanella putrefaciens}}$

Fujimoto, Jun*; Tanaka, Kazuya; Watanabe, Naoko*; Takahashi, Yoshio*

Hydrometallurgy, 166, p.80 - 86, 2016/12

 Times Cited Count:6 Percentile:31.71(Metallurgy & Metallurgical Engineering)

We examined recovery of REEs in Fe-Mn nodules by using ${{it Shewanella putrefaciens}}$ (Fe-reducing bacterium). In this method, Fe-Mn nodule decomposition and REE recovery were achieved simultaneously in a single solution system. Fe-Mn nodules were reductively decomposed in NaCl solution under anaerobic conditions with daily addition of sodium lactate as an electron donor. During the decomposition of Fe-Mn nodule, REEs released from the Fe-Mn nodule were adsorbed on bacterial cells. Of the conditions studied here, the best REE adsorption rates were obtained with 0.5M NaCl solution at pH7 with daily addition of 1 mmol sodium lactate.

Journal Articles

$$E1$$ and $$E2$$ cross sections of the $$^{12}$$C($$alpha$$,$$gamma$$)$$^{16}$$O reaction at $$E_{rm{eff}}$$ $$sim$$ 1.2 MeV using pulsed $$alpha$$ beams

Makii, Hiroyuki; Ueda, Hitoshi*; Temma, Yasuyuki*; Nagai, Yasuki*; Shima, Tatsushi*; Fujimoto, Shinya*; Segawa, Mariko; Mishima, Kenji*; Nishiyama, Jun*; Igashira, Masayuki*

AIP Conference Proceedings 1269, p.283 - 288, 2010/10

 Times Cited Count:0 Percentile:0.02

The $$^{12}$$C($$alpha$$,$$gamma$$)$$^{16}$$O reaction cross section plays an important role in stellar evolution at the stage of helium-burning. However, the cross section at low energy still has a large uncertainty mainly due to the poor determination of the ratio of $$E2$$ cross section to $$E1$$ one. Hence, we have installed new system to make a precise measurement of the cross section. In this experiment, we used the high efficiency anti-Compton NaI(Tl) spectrometers with a large S/N ratio, an intense pulsed $$alpha$$ beams, and the monitoring system of target thickness. With use of the system we succeeded in removing a background due to neutron and could clearly detect the $$gamma$$-ray from the $$^{12}$$C($$alpha$$,$$gamma$$)$$^{16}$$O reaction with high statistics. We determined the $$E1$$ and $$E2$$ cross section down to $$E_{rm{eff}} sim $$ 1.2 MeV, and thus obtained results are compared to recent theoretical calculations.

JAEA Reports

Basis data for surveillance test on core support graphite structures for the High Temperature Engineering Test Reactor (HTTR)

Sumita, Junya; Shibata, Taiju; Kikuchi, Takayuki; Ishihara, Masahiro; Iyoku, Tatsuo; Sawa, Kazuhiro; Fujimoto, Nozomu

JAEA-Data/Code 2007-001, 57 Pages, 2007/02

JAEA-Data-Code-2007-001.pdf:3.0MB

Visual inspection by a TV camera and material properties measurement by surveillance test on core support graphite structures are planned for the High Temperature Engineering Test Reactor (HTTR) to confirm their structural integrity and characteristics. The surveillance test is aimed to investigate the change of material and mechanical properties by aging effects such as fast neutron irradiation and oxidation. The obtained data will be used not only for evaluating the structural integrity of the core support graphite structure of the HTTR but also for design data to advanced Very High Temperature Reactor (VHTR) discussed at generation IV international forum. This report describes the material properties and installed position of surveillance specimens in the HTTR in order to carry out the surveillance test.

Journal Articles

Evaluation of fuel temperature on high temperature test operation at high temperature gas-cooled reactor 'HTTR'

Tochio, Daisuke; Sumita, Junya; Takada, Eiji*; Fujimoto, Nozomu; Nakagawa, Shigeaki

Nihon Genshiryoku Gakkai Wabun Rombunshi, 5(1), p.57 - 67, 2006/03

High Temperature Engineering Test Reactor(HTTR) of high temperature gas-cooled reactor at Japan Atomic Energy Agency(JAEA) achieved the reactor outlet coolant temperature of 950$$^{circ}$$C for the first time in the world at Apr. 19, 2004. To ensure the thermal integrity of fuel in high temperature test operation, it is necessary that fuel temperature is designed appropriately by fuel temperature designing method, and that estimated maximum fuel temperature is lower than the thermal limit temperature. In this report, by constructing newly a realistic core-shape representing model, the current fuel temperature estimation model is improved. Moreover fuel temperature in high-temperature test operation is estimated with the newly-constructed model, and it is confirmed that estimated maximum fuel temperature in high temperature test operation is lower than the thermal limit temperature.

JAEA Reports

Sodium Flow Test for Dummy Core Fuel Sudassemdlies of Prototype Fast Breeder Reactor MONJU (on Pressure Loss Increase of MONJU Dummy Core Fuel Subassemblies)

Fujimoto, Tetsuro*; Sato, Kazujiro*; Takahashi, June*

PNC TN951 76-14, 59 Pages, 1976/09

PNC-TN951-76-14.pdf:2.2MB

The 4,800-hours flow test for MONJU dummy core fuel subassemblies was carried out at sodium flow rate of 19.5 - 20.2 kg/sec. subassembly, sodium temperature of 600$$^{circ}C$$, oxygen impurities in sodium of 2 - 2.5ppm which are about the same condition as that for MONJU core fuel subassemblies. The result of this test showed that the pressure loss of dummy core fuel subassemblies increased up to 11% in 3,000 hours and became constant after that. The integrity of the dummy subassemblies is planned to be investigated by disassembling them and making a material examination. On the other hand,the pressure loss increase for these subassembkies was estimated at 5.4% in case of water flow test which was carried out before and after spdium test. The cause of this difference should be investigated hereafter.

Oral presentation

Development of gamma-ray induced positron annihilation lifetime spectroscopy

Taira, Yoshitaka*; Fujimoto, Masaki*; Fujimori, Kosuke*; Kitaura, Mamoru*; Zen, H.*; Okano, Yasuaki*; Hosaka, Masahito*; Yamazaki, Junichiro*; Kato, Masahiro*; Hirade, Tetsuya; et al.

no journal, , 

For general positron sources, radioisotopes such as $$^{22}$$Na are often used. However, there is a problem that positrons cannot probe the deep region of metal materials with a thickness of 1 mm or more. Gamma-ray induced positron annihilation lifetime measurement (GiPALS) is a method for generating positrons in bulk samples with a thickness of several centimeters and samples placed in vessels such as high temperature and/or pressure furnaces. The annihilation lifetime of positrons is about 200 ps for metal materials, so it is important to use gamma rays with a shorter pulse width for GiPALS in order to accurately measure the positron lifetime. We have succeeded in the proof-of-principle experiment for GiPALS of ultra-short pulse gamma rays with a pulse width of 2 ps, which was originally developed using 90$$^{circ}$$ collision laser Compton scattering at UVSOR.

Oral presentation

Development of gamma-ray induced positron annihilation lifetime spectroscopy at UVSOR

Taira, Yoshitaka*; Fujimoto, Masaki*; Fujimori, Kosuke*; Kitaura, Mamoru*; Zen, H.*; Okano, Yasuaki*; Hosaka, Masahito*; Yamazaki, Junichiro*; Kato, Masahiro*; Hirade, Tetsuya; et al.

no journal, , 

For general positron sources, radioisotopes such as $$^{22}$$Na are often used. However, there is a problem that positrons cannot probe the deep region of metal materials with a thickness of 1 mm or more. Gamma-ray induced positron annihilation lifetime measurement (GiPALS) is a method for generating positrons in bulk samples with a thickness of several centimeters and samples placed in vessels such as high temperature and/or pressure furnaces. The annihilation lifetime of positrons is about 200 ps for metal materials, so it is important to use gamma rays with a shorter pulse width for GiPALS in order to accurately measure the positron lifetime. We have succeeded in the proof-of-principle experiment for GiPALS of ultra-short pulse gamma rays with a pulse width of 2 ps, which was originally developed using 90$$^{circ}$$ collision laser Compton scattering at UVSOR.

Oral presentation

Magnetic circular dichroism in extended X-ray absorption fine structure at the Mn L$$_{2,3}$$ edges on the Heusler alloy Co$$_{2}$$MnSi

Fujiwara, Hidenori*; Kogo, Junya*; Kasahara, Rika*; Nishioka, Takuma*; Fujimoto, Nao*; Nagai, Kodai*; Sekiyama, Akira*; Sumida, Kazuki; Takeda, Yukiharu; Saito, Yuji; et al.

no journal, , 

no abstracts in English

15 (Records 1-15 displayed on this page)
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