Takayama, Yusuke; Sato, Daisuke*; Kikuchi, Hirohito*
Genshiryoku Bakkuendo Kenkyu (CD-ROM), 29(2), p.101 - 111, 2022/12
Swelling pressure tests have been conducted to understand the swelling properties of bentonite which is planned to be used as a buffer material in repositories for the geological disposal of radioactive waste. It has been reported that the swelling pressure obtained by swelling pressure test increases monotonically or temporarily decreases after increasing with the passage of the time depending on the initial water content. In this study, swelling pressure tests were conducted under several different initial water content conditions, and the change in wet density distribution inside the specimen during the swelling pressure tests was observed by X-ray CT measurement. It was confirmed that the presence or absence of collapse behavior and its magnitude affect the shape of the change in swelling pressure. When the collapse deformation was large, the amount of temporary decrease in swelling pressure was large. On the other hand, swelling pressure increased monotonically when there was no deformation due to collapse.
Nakajima, Kenji; Kawamura, Seiko; Kofu, Maiko; Murai, Naoki; Inamura, Yasuhiro; Kikuchi, Tatsuya*; Wakai, Daisuke*
JPS Conference Proceedings (Internet), 33, p.011089_1 - 011089_7, 2021/03
The recent update of AMATERAS, a cold-neutron disk-chopper spectrometer at Japan Proton Accelerator Research Complex (J-PARC), is reported. AMATERAS has been operating for a decade. Since 2017, some updates have been done or are underway, which include installing new detectors, replacing the vacuum system of the scattering chamber, and other works. We are also working on the re-investigation of the resolution function. Demonstration measurements were carried out at 1MW test operations done in 2018 and 2019. Plans of upgrading the spectrometer are currently being considered.
Saito, Yuji; Fujiwara, Hidenori*; Yasui, Akira*; Kadono, Toshiharu*; Sugawara, Hitoshi*; Kikuchi, Daisuke*; Sato, Hideyuki*; Suga, Shigemasa*; Yamasaki, Atsushi*; Sekiyama, Akira*; et al.
Physical Review B, 102(16), p.165152_1 - 165152_8, 2020/10
Kikkawa, Takashi*; Suzuki, Motohiro*; Ramos, R.*; Aguirre, M. H.*; Okabayashi, Jun*; Uchida, Kenichi*; Lucas, I.*; Anadn, A.*; Kikuchi, Daisuke*; Algarabel, P. A.*; et al.
Journal of Applied Physics, 126(14), p.143903_1 - 143903_11, 2019/10
Kikuchi, Tatsuya*; Nakajima, Kenji; Kawamura, Seiko; Inamura, Yasuhiro; Nakamura, Mitsutaka; Wakai, Daisuke*; Aoyama, Kazuhiro*; Iwahashi, Takaaki*; Kambara, Wataru*
Physica B; Condensed Matter, 564, p.45 - 53, 2019/07
Details of the background, that is, unwanted signals accumulated by the data acquisition system of neutron instruments, observed by the cold-neutron chopper spectrometer AMATERAS installed at the Materials and Life Science Experimental Facility at J-PARC are reported. In the design phase of AMATERAS, we carefully considered the achievement of high signal-to-noise ratio, and possible countermeasures were implemented. Actually, recent scientific outputs from AMATERAS indicates that the spectrometer is one of excellent neutron instruments with low background. In spite of that, in nine years of AMATERAS operation, we have encountered unwanted signals due to various reasons, including gamma-rays emitted at materials on or near the beam line including the sample itself, scattered neutrons from the beam line devices, air scattering, electronic noise in data acquisition system, cosmic rays, T0 burst, and other unknown sources. In this report, we discuss the background observed by AMATERAS, especially in the conditions of without samples, comprehensively. The possible sources of these signals and the countermeasures considered against the above sources are discussed, which may be helpful to those who are engaged in other existing or planned neutron-scattering instruments.
Nakajima, Kenji; Kawamura, Seiko; Kikuchi, Tatsuya*; Kofu, Maiko; Kawakita, Yukinobu; Inamura, Yasuhiro; Kambara, Wataru*; Aoyama, Kazuhiro*; Wakai, Daisuke*; Harada, Masahide; et al.
Journal of Physics; Conference Series, 1021(1), p.012031_1 - 012031_5, 2018/06
Kikkawa, Takashi*; Suzuki, Motohiro*; Okabayashi, Jun*; Uchida, Kenichi*; Kikuchi, Daisuke*; Qiu, Z.*; Saito, Eiji
Physical Review B, 95(21), p.214416_1 - 214416_7, 2017/06
Kikuchi, Daisuke*; Ishida, Masahiko*; Uchida, Kenichi*; Qiu, Z.*; Murakami, T.*; Saito, Eiji
Applied Physics Letters, 106(8), p.082401_1 - 082401_4, 2015/02
Uchida, Kenichi*; Adachi, Hiroto; Kikuchi, Daisuke*; Ito, Shun*; Qiu, Z.*; Maekawa, Sadamichi; Saito, Eiji
Nature Communications (Internet), 6, p.5910_1 - 5910_8, 2015/01
Tsutsumi, Tomoaki*; Adachi, Rika*; Takatsuki, Satoshi*; Nei, Daisuke*; Kameya, Hiromi*; Todoriki, Setsuko*; Kikuchi, Masahiro; Kobayashi, Yasuhiko; Matsuda, Rieko*; Teshima, Reiko*
Shokuhin Shosha, 49(1), p.9 - 15, 2014/12
no abstracts in English
Kajiwara, Yosuke*; Uchida, Kenichi*; Kikuchi, Daisuke*; An, Toshu*; Fujikawa, Yasunori*; Saito, Eiji
Applied Physics Letters, 103(5), p.052404_1 - 052404_4, 2013/07
Heat-current-induced manipulation of spin relaxation in YFeO under an in-plane temperature gradient is investigated. We show that the linewidth of the ferromagnetic resonance spectrum, i.e., the spin relaxation, in an YFeO film increases or decreases depending on the temperature-gradient direction and that this modulation is attributed to the spin-transfer torque caused by a thermally induced transverse spin-wave spin current in the YFeO film. The experimental results also show that the spin-current magnitude generated by spin pumping in an attached Pt film is inversely proportional to the square of the modulated Gilbert damping constant, consistent with a phenomenological spin-pumping model.
Adare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Aramaki, Y.*; et al.
Physical Review C, 83(4), p.044912_1 - 044912_16, 2011/04
Measurements of electrons from the decay of open-heavy-flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled collisions. Here we extend these studies to two particle correlations where one particle is an electron from the decay of a heavy flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interaction between heavy quarks and the quark-gluon matter. We find the away-side-jet shape and yield to be modified in Au+Au collisions compared to collisions.
Shu, L.*; Higemoto, Wataru; Aoki, Yuji*; Hillier, A. D.*; Oishi, Kazuki*; Ishida, Kenji*; Kadono, Ryosuke*; Koda, Akihiro*; Bernal, O. O.*; MacLaughlin, D. E.*; et al.
Physical Review B, 83(10), p.100504_1 - 100504_4, 2011/03
Zero-field muon spin relaxation experiments have been carried out in the Pr(OsRu)Sb and PrLaOsSb alloy systems to investigate broken time-reversal symmetry (TRS) in the superconducting state, signaled by the onset of a spontaneous static local magnetic field B. In both alloy series B initially decreases linearly with solute concentration. Ru doping is considerably more efficient than La doping, with a 50% faster initial decrease. The data suggest that broken TRS is suppressed for Ru concentration 0.6 but persists for essentially all La concentrations. Our data support a crystal-field excitonic cooper pairing mechanism for TRS-breaking superconductivity.
Kameya, Hiromi*; Kakita, Daisuke*; Kaimori, Yoshihiko*; Kikuchi, Masahiro; Kobayashi, Yasuhiko; Ukai, Mitsuko*; Shimoyama, Yuhei
Radioisotopes, 59(10), p.607 - 614, 2010/10
Mangoes are imported to Japan after treated with hot water. Recently, irradiated mangoes imported to U. S. are widely used. This paper reports on the ESR method for analyzing the radiation induced radicals of irradiated mangoes. Upon the ray irradiation, a strong signal peak in the flesh and skin of mangoes was observed at = 2.004. This singlet peak may be attributed to organic free radicals. The ESR spectra of the flesh and skin of mangoes showed the radiation induced radicals due to cellulose by irradiation over 12 kGy. The relaxation time (T1 and T2) of the singlet signal were calculated. T2 showed dose response according to increasing the irradiation dose levels, while T1 was almost constant. The value of (T1T2)1/2 showed the dependence of irradiation dose level.
Kikuchi, Masahiro; Kakita, Daisuke*; Shimoyama, Yuhei; Ukai, Mitsuko*; Kobayashi, Yasuhiko
Shokuhin Shosha, 45(1-2), p.34 - 38, 2010/09
Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki*; Sato, Kazuhiko*; Aoki, Yuji*; Toda, Shizuka*; Kikuchi, Daisuke*; Sato, Hideyuki*; Baines, C.*
Physical Review B, 82(1), p.014420_1 - 014420_8, 2010/07
An antiferromagnetic (AFM) ground state and a possible high-field ordered state in magnetic fields T of a filled-skutterudite compound CeOsSb were investigated by the muon spin rotation and relaxation method. In a zero applied field, a spontaneous local filed due to the weak AFM ordering was observed below 1.6 K. The magnetic volume fraction gradually increases below 1.6 K with decreasing temperature, suggesting that this phase is sensitive to sample quality. The magnitude of the ordered dipole moment in the AFM state was estimated to be in the range from 0.11 to 0.17 /Ce at 0.1 K. In a field of 2 T applied along the  direction, clear anomalies in the muon Knight shift and line width were observed at 1.5 K, consistent with the phase transition scenario into the high-field ordered state suggested from specific heat, resistivity, elastic, and NMR anomalies.
Osakabe, Toyotaka; Kuwahara, Keitaro*; Kawana, Daichi*; Iwasa, Kazuaki*; Kikuchi, Daisuke*; Aoki, Yuji*; Kogi, Masafumi*; Sato, Hideyuki*
Journal of the Physical Society of Japan, 79(3), p.034711_1 - 034711_7, 2010/03
Ito, Takashi; Higemoto, Wataru; Oishi, Kazuki*; Heffner, R. H.; Nishida, Nobuhiko*; Sato, Kazuhiko*; Sugawara, Hitoshi*; Aoki, Yuji*; Kikuchi, Daisuke*; Sato, Hideyuki*
Physica B; Condensed Matter, 404(5-7), p.761 - 764, 2009/04
We report on detailed longitudinal field (LF) SR studies in SmRuP in order to characterize magnetic fluctuations in a magnetically ordered state below K. A magnitude and fluctuation rate of the fluctuating field are derived as functions of temperature from LF dependence of the longitudinal relaxation rate. Possible low-energy excitations of magnetic multipoles are discussed.
Aoki, Yuji*; Higemoto, Wataru; Tsunashima, Yoshino*; Yonezawa, Yuki*; Sato, Koki*; Koda, Akihiro*; Ito, Takashi; Oishi, Kazuki; Heffner, R. H.; Kikuchi, Daisuke*; et al.
Physica B; Condensed Matter, 404(5-7), p.757 - 760, 2009/04
Zero field (ZF) and transverse field (TF) muon spin relaxation and rotation (SR) study has been carried out in filled-skutterudite SmOsSb in order to investigate the magnetically robust heavy-fermion (HF) state and the weak ferromagnetic anomaly. A large-amplitude oscillating signal appears in the ZF-SR spectra at low temperatures, confirming that the weak ferromagnetic anomaly is an intrinsic bulk property. Analysis reveals that the weak ferromagnetic moment is carried by itinerant heavy quasiparticles.
Sato, Hideyuki*; Aoki, Yuji*; Kikuchi, Daisuke*; Sugawara, Hitoshi*; Higemoto, Wataru; Oishi, Kazuki; Ito, Takashi; Heffner, R. H.; Saha, S. R.*; Koda, Akihiro*; et al.
Physica B; Condensed Matter, 404(5-7), p.749 - 753, 2009/04
Wide varieties of strongly correlated electron phenomena are performed on the stage of a filled skutterudite structure. Especially when one of the players contains a plural number of 4f electrons, the orbital degrees of freedom play a major role as a new type of nonmagnetic and/or weak-magnetic phenomena. Several examples found in Pr- and Sm-based filled skutterudites are introduced in relation to muon spin relaxation experiments.