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Fuwa, Yasuhiro; Hattori, Ayaka*; Ito, Hayato*; Iwashita, Yoshihisa*; Katayama, Ryo*; Kubo, Takayuki*; Saeki, Takayuki*
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.353 - 355, 2026/03
no abstracts in English
Nakano, Hideto; Yamamoto, Kazami; Morishita, Takatoshi; Okabe, Kota; Masukawa, Fumihiro
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.775 - 778, 2026/03
no abstracts in English
Saha, P. K.; Harada, Hiroyuki; Tamura, Fumihiko; Shobuda, Yoshihiro; Kojima, Kunihiro; Yoshimoto, Masahiro; Okita, Hidefumi; Okabe, Kota; Hatakeyama, Shuichiro; Nakanoya, Takamitsu; et al.
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.549 - 553, 2026/03
Ito, Takashi
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.364 - 367, 2026/03
no abstracts in English
Kondo, Ayaka*; Iijima, Toru*; Sumi, Kazumichi*; Takeuchi, Yusuke*; Cicek, E.*; Ego, Hiroyasu*; Otani, Masashi*; Nakazawa, Yuga*; Futatsukawa, Kenta*; Mibe, Tsutomu*; et al.
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.18 - 22, 2026/03
The muon anomalous magnetic moment (
) and electric dipole moment (EDM) are sensitive to new physics beyond the Standard Model. At J-PARC, precision measurements using a novel low-emittance muon beam generated via cooling and acceleration are planned. The muon linac consists of four types of RF cavities for different 
ranges. For the medium-velocity range (=0.3-0.7), a prototype bridge coupler, which electromagnetically connects DAW tanks while allowing space for quadrupole magnets, was designed and fabricated. Low-power tests yielded a Q value of 4500 (50% of the design) and 10% field flatness. This paper reports on the design and test results.
Yoshimoto, Masahiro; Yamada, Ippei; Nakanoya, Takamitsu; Saha, P. K.; Hatakeyama, Shuichiro; Saeki, Riuji*; Kuramochi, Masaya*; Otsu, Satoru*
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.274 - 279, 2026/03
To achieve a high-intensity proton beam, the J-PARC 3-GeV rapid cycling synchrotron accelerator (RCS) adopts the multi-turn charge-exchange beam injection scheme, in which the carbon stripper foils remove the electron from the injected H
beam to convert the H
beam. Up to now, we have demonstrated that the foils have a sufficient lifetime for continuous beam operation at the design power of 1 MW. On the other hand, we are investigating the possibility of increasing the beam power at the J-PARC further; we hope to achieve a maximum output of 2 MW at the RCS. In general, the key issue for the stripper foil at higher power beam irradiation is the shortened lifetime due to the rising foil temperature. As it reaches the sublimation temperature, it is of concern that the foil's thickness is rapidly decreasing. In this presentation, we will report the simulation result of the rising foil temperature according to the RCS beam power upgrade plan and the recent status of the study for the versatile foil temperature measurement.
Yamamoto, Kazami; Nakano, Hideto; Matsumoto, Tetsuro*
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.782 - 786, 2026/03
To accumulate a high-intensity beam in the Rapid Cycling Synchrotron (RCS), the H beams from the linac converted into protons and injected into the RCS. In this process, a certain amount of the beam is not converted, and it leads to the injection dump. Since the secondary particles are constantly produced inside the dump due to this waste beam, we have studied if those secondary particles can be used as an irradiation test. In this report, we compare the residual nuclides obtained from the calculations using PHITS/DCHAIN codes and measurements using a germanium-semiconductor detector after activating a bismuth-209 (
Bi) sample. We also developing the sample insertion system for irradiation test.
Oguri, Hidetomo
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1013 - 1018, 2026/03
no abstracts in English
Nakagawa, Sohei; Kabumoto, Hiroshi; Kutsukake, Kenichi; Otokawa, Yoshinori; Asozu, Takuhiro; Matsui, Yutaka; Ikekame, Takuma; Kato, Yuta; Nakamura, Masahiko
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1034 - 1038, 2026/03
no abstracts in English
Kojima, Kunihiro; Harada, Hiroyuki; Saha, P. K.
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.289 - 293, 2026/03
Uncontrolled beam loss in the 3 GeV rapid-cycling synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) was investigated. A significant amount of uncontrolled beam loss was observed, especially at each arc section, despite the RCS being equipped with a collimation system designed to collect halo particles with one scatterer and five absorbers. Based on the time-dependence of the beam loss measured in the collimation system and arc sections, the particles lost at the arc sections are found to be likely scattered by the absorber rather than the scatterer, contrary to the design of the collimation system. By changing the configuration of the collimation system, it was determined that the absorber through which the majority of the lost particles passed was the second absorber. In addition, the trajectory of such a particle was identified by using numerical simulation assuming the lattice structure of the RCS.
Kojima, Kunihiro; Harada, Hiroyuki; Chimura, Motoki; Nagayama, Shota*; Saha, P. K.
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.104 - 108, 2026/03
A detailed study on the random resonance was conducted to ensure sufficient tunability in the 3-GeV rapid cycling synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC). The progressive improvement in beam intensity, aiming for an output beam power of 1.5 MW, inevitably excites the effect of the structure resonance and requires the operating point to be shifted higher. Employing a low-intensity beam, the excitation of the sum linear resonance locating just above the current operating point is revealed. The linear sum resonance was confirmed to be compensated by making local bumps in the arc section by using the steering magnets. Based on the resonance driving term, the main source of the imperfection field is identified as the leakage field from extraction magnets.
Fuwa, Yasuhiro; Mizobata, Satoshi*; Nakano, Hideto; Shinozaki, Shinichi; Takayanagi, Tomohiro; Asano, Hiroyuki; Iwama, Yuhei*
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.389 - 391, 2026/03
no abstracts in English
Tamura, Fumihiko; Okita, Hidefumi; Yamamoto, Masanobu; Yoshii, Masahito*; Omori, Chihiro*; Seiya, Kiyomi*; Sugiyama, Yasuyuki*; Nomura, Masahiro; Shimada, Taihei; Hasegawa, Katsushi*; et al.
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.269 - 273, 2026/03
The replacement project for the Magnetic Alloy (MA) cavities of the 3GeV RCS at J-PARC has been underway for several years. The original cavities are the push-pull (PP) configuration, where rf current is supplied alternately from a pair of tetrode tubes to the electrodes on the upstream and downstream sides of the acceleration gap. All cavities are to be replaced with newly developed single-ended (SE) cavities. In PP cavities, significant unbalance in the operation of the upstream and downstream tetrodes due to multiharmonic rf occurs. This unbalance has been one of the limiting factor of beam intensity. This unbalance does not occur essentially in SE cavities. Currently, six of the twelve cavities have been replaced. The SE cavity does not have a configuration to cancel even-order higher harmonics, therefore the harmonic components are different from those of the original PP cavity. We report on the operational experience with the single-ended cavity at the J-PARC RCS.
Kuriyama, Yasutoshi; Fuwa, Yasuhiro; Iwashita, Yoshihisa*; Terunuma, Nobuhiro*
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.936 - 938, 2026/03
no abstracts in English
Adachi, Kyosuke; Tamura, Fumihiko; Nomura, Masahiro; Shimada, Taihei; Okita, Hidefumi; Yoshii, Masahito*; Omori, Chihiro*; Seiya, Kiyomi*; Hara, Keigo*; Hasegawa, Katsushi*; et al.
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.280 - 284, 2026/03
no abstracts in English
Chimura, Motoki; Watanabe, Kazuhiko*; Takahashi, Hiroki; Hirano, Koichiro; Shinto, Katsuhiro; Kitamura, Ryo; Kawase, Masato*; Suzuki, Takahiro*; Morishita, Takatoshi
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.709 - 713, 2026/03
no abstracts in English
Okita, Hidefumi; Tamura, Fumihiko; Adachi, Kyosuke; Nomura, Masahiro; Shimada, Taihei; Yoshii, Masahito*; Omori, Chihiro*; Seiya, Kiyomi*; Hara, Keigo*; Hasegawa, Katsushi*; et al.
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.795 - 800, 2026/03
no abstracts in English
Morohashi, Yuko; Yamada, Ippei; Kobayashi, Fuminori; Tamura, Jun; Miyao, Tomoaki*; Moriya, Katsuhiro; Kamiya, Junichiro
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.508 - 511, 2026/03
no abstracts in English
Nakanoya, Takamitsu; Yoshimoto, Masahiro; Saha, P. K.; Takeda, Osamu*; Saeki, Riuji*; Muto, Masayoshi*; Miyo, Takuya*
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.790 - 794, 2026/03
The J-PARC 3 GeV Rapid Cycling Synchrotron (RCS) utilizes pure carbon foils produced in-house by JAEA as charge exchange foils. In November 2023, during beam commissioning just before the start of user operation, a malfunction occurred in a foil drive mechanism. The foil drive mechanism is responsible for replacing and inserting foils into the beamline. This malfunction prevented remote replacement of the foils. Therefore, when foil replacement was necessary, it was performed manually with visual confirmation near the mechanism. The foil drive mechanism was subsequently replaced and restored during the 2024 summer maintenance period. Despite the issue with the foil drive mechanism, the charge exchange foils demonstrated stability under beam irradiation, and there were no operational problems. Recent efforts have significantly enhanced the durability of the foils against beam irradiation through the implementation of two novel methods. One method involves selecting an appropriate diameter for the carbon rod used in charge exchange foil fabrication. The other method utilizes carbon nanotube (CNT) wire as a support material for the foils. While beam irradiation causes foil deformation, these methods show significantly reduced deformation compared to previous foils. This improvement raises the possibility of using foils for a longer operational lifespan. In this paper, we report on the foil drive mechanism malfunction, subsequent replacement work, and the performance of the charge exchange foils during user operation from 2023 to 2025.
Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Meigo, Shinichiro; Maekawa, Fujio
Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.130 - 134, 2026/03
Accelerator-Driven Systems (ADS) represent an efficient solution to the challenge of nuclear waste disposal. Therefore, the Japan Atomic Energy Agency (JAEA) is designing a 30-MW proton linac as a key element of its proposal for the use of ADS technology. A key feature of ADS accelerators is their extremely high availability and reliability that is required to avoid thermal stress on reactor structures. To this end, JAEA-ADS adopted a combined strategy of hot standby in the front part of the linac and standby element compensation as a fast and efficient way to reduce the downtime due to an element failure. The JAEA-ADS injector is mainly composed of a normal conducting section and ends with the first section of superconducting cavities (Half Wave Resonator). This paper presents the details of the optics design of the JAEA-ADS injector and the results of beam dynamics simulations.
