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Tamura, Fumihiko; Omori, Chihiro*; Yoshii, Masahito*; Tomizawa, Masahito*; Toyama, Takeshi*; Sugiyama, Yasuyuki*; Hasegawa, Katsushi*; Kobayashi, Aine*; Okita, Hidefumi
Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.175 - 178, 2023/01
J-PARC MR delivers high intensity proton beams to the neutrino experiment. Eight bunches with high peak currents are extracted from the MR by the extraction kicker, therefore the neutrino beam has the similar structure. Intermediate Water Cherenkov Detector (IWCD) will be installed for the future experiments and the IWCD requires a time structure with low peaks. We consider bunch manipulation at flattop of the MR for reducing the peak current. It should be quickly done to avoid the significant loss of the beam power. The beam gap for the kicker rise time must be kept. We propose a non-adiabatic bunch manipulation using the multiharmonic rf voltage. The longitudinal impedance in the MR can affect the beam stability. The feasibility of the manipulation is discussed by using the longitudinal simulations.
Yamamoto, Kazami; Kinsho, Michikazu; Hayashi, Naoki; Saha, P. K.; Tamura, Fumihiko; Yamamoto, Masanobu; Tani, Norio; Takayanagi, Tomohiro; Kamiya, Junichiro; Shobuda, Yoshihiro; et al.
Journal of Nuclear Science and Technology, 59(9), p.1174 - 1205, 2022/09
Times Cited Count：6 Percentile：84.97(Nuclear Science & Technology)In the Japan Proton Accelerator Research Complex, the purpose of the 3 GeV rapid cycling synchrotron (RCS) is to accelerate a 1 MW, high-intensity proton beam. To achieve beam operation at a repetition rate of 25 Hz at high intensities, the RCS was elaborately designed. After starting the RCS operation, we carefully verified the validity of its design and made certain improvements to establish a reliable operation at higher power as possible. Consequently, we demonstrated beam operation at a high power, namely, 1 MW. We then summarized the design, actual performance, and improvements of the RCS to achieve a 1 MW beam.
Watanabe, Tamaki*; Toyama, Takeshi*; Hanamura, Kotoku*; Imao, Hiroshi*; Kamigaito, Osamu*; Kamoshida, Atsushi*; Kawachi, Toshihiko*; Koyama, Ryo*; Sakamoto, Naruhiko*; Fukunishi, Nobuhisa*; et al.
Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1105 - 1108, 2019/07
Upgrades for the RIKEN heavy-ion linac (RILAC) involving a new superconducting linac (SRILAC) are currently underway at the RIKEN radioactive isotope beam factory (RIBF). It is crucially important to develop nondestructive beam measurement diagnostics. We have developed a beam energy position monitor (BEPM) system which can measure not only the beam position but also the beam energy simultaneously by measuring the time of flight of the beam. We fabricated 11 BEPMs and completed the position calibration to obtain the sensitivity and offset for each BEPMs. The position accuracy has been achieved to be less than 
0.1 mm by using the mapping measurement.
Yamamoto, Masanobu; Nomura, Masahiro; Schnase, A.; Shimada, Taihei; Tamura, Fumihiko; Ezura, Eiji*; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Takagi, Akira*; et al.
Proceedings of 3rd International Particle Accelerator Conference (IPAC '12) (Internet), p.2952 - 2954, 2012/05
In J-PARC RCS, the high intensity beam is delivered to the MR. The longitudinal beam emittance at the RCS extraction should be optimized to avoid the beam loss after the MR injection. In order to match the longitudinal emittance shape between the RCS and the MR, it is desirable to enlarge the longitudinal emittance during the RCS acceleration. We have performed the particle tracking simulation for the controlled longitudinal emittance blow up in the RCS.
Schnase, A.; Tamura, Fumihiko; Koseki, Tadashi*; Tomizawa, Masahito*; Toyama, Takeshi*; Yoshii, Masahito*; Omori, Chihiro*; Nomura, Masahiro; Yamamoto, Masanobu; Toda, Makoto*; et al.
Proceedings of 7th Annual Meeting of Particle Accelerator Society of Japan (DVD-ROM), p.1079 - 1081, 2010/08
Schnase, A.; Tamura, Fumihiko; Koseki, Tadashi*; Tomizawa, Masahito*; Toyama, Takeshi*; Yoshii, Masahito*; Omori, Chihiro*; Nomura, Masahiro; Yamamoto, Masanobu; Toda, Makoto*; et al.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.1446 - 1448, 2010/05
superconductorsTsutsui, Kenji; Toyama, Atsushi*; Toyama, Takami*; Maekawa, Sadamichi*
Journal of Physics and Chemistry of Solids, 69(12), p.3365 - 3368, 2008/12
Times Cited Count：0 Percentile：0(Chemistry, Multidisciplinary)Substitution of impurities Zn and Ni for Cu in high- superconductors has attracted much attention. The recent neutron scattering experiment show that Ni doping traps holes in the vicinity of Ni sites. We theoretically examine the electronic state with impurity based on the 
model where impurity Zn and Ni 3
orbitals are explicitly treated. We carry out the numerically exact diagonalization method on small cluster. We find the region where a hole is trapped in the Ni site so that the effective hole concentration decreases and the ground state has strong antiferromagnetic correlations, as indicated from the experimental study.
solution for identification of fluoride species of DbToyoshima, Atsushi; Mitsukai, Akina; Murakami, Masashi*; Sato, Daisuke*; Motoyama, Risa*; Oe, Kazuhiro*; Komori, Yukiko*; Haba, Hiromitsu*; Asai, Masato; Tsukada, Kazuaki; et al.
no journal, ,
The purpose of the present study is characterization of fluoride complexes of Db. In this study, we investigated anion-exchange behavior of Nb and Ta, lighter homologs of Db, in 1.0-24 M HF/2.0 M HNO solutions as a model experiment of Db. 
Nb and 
Ta produced at JAEA tandem accelerator and RIKEN AVF cyclotron, respectively, were prepared as non-carrier-added radiotracers by an ion exchange method. Batch experiments were performed with anion-exchange resin. As a result, distribution coefficients (
) of Nb showed a sharp increase at 
6 M HF while those of Ta had a monotonic decrease as increasing HF concentration. This suggests that Nb forms fluoride complexes from oxy fluoride one at 6 M HF and Ta exists as fluoride complexes under the conditions. It is expected that chemical species of Db fluorides are characterized in its anion-exchange experiments under the present conditions.
Toyama, Takeshi*; Inoue, Koji*; Nagai, Yasuyoshi*; Kinomura, Atsushi*; Suzudo, Tomoaki; Hatano, Yuji*
no journal, ,
Tungsten (W) is promising as a fusion reactor plasma facing material. Retention and accumulation of hydrogen isotopes become a problem under irradiation, but it was found that the amount of hydrogen isotope accumulation is significantly reduced by the addition of rhenium (Re) and chromium (Cr). This is thought that Re and Cr suppress the formation of vacancy-type defects under irradiation, which are hydrogen trapping sites, but sufficient experimental findings to support this phenomenon have not been obtained yet. The purpose of this study is to apply the positron annihilation method and to investigate the effect of additive elements on the formation of irradiation defects in W alloys under electron beam and neutron irradiation.
