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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
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.
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
Okita, Hidefumi; Adachi, Kyosuke; Tamura, Fumihiko; Nomura, Masahiro; Shimada, Taihei; Yoshii, Masahito*; Omori, Chihiro*; Seiya, Kiyomi*; Sugiyama, Yasuyuki*; Hasegawa, Katsushi*; et al.
Journal of Physics; Conference Series, 3094(1), p.012027_1 - 012027_7, 2025/09
no abstracts in English
Tamura, Fumihiko; Sugiyama, Yasuyuki*; Okita, Hidefumi; Yamamoto, Masanobu; Yoshii, Masahito*; Omori, Chihiro*; Seiya, Kiyomi*; Nomura, Masahiro; Shimada, Taihei; Hasegawa, Katsushi*; et al.
Proceedings of 21st Annual Meeting of Particle Accelerator Society of Japan (Internet), p.774 - 776, 2024/10
The 3GeV RCS of J-PARC accelerates proton beams with a maximum beam intensity of 8e13 ppp, utilizing the features of magnetic alloy (MA) cavities. The beam is extracted in a single turn by kicker magnets, and immediately after the beam is extracted, a short voltage jump occurs in the cavity. This is due to a delay in the voltage control feedback, which takes a certain amount of time to respond to the step-like decrease of beam current upon single-turn extraction. In a wideband (Q=2) MA cavity, this response delay is observed as a voltage jump. This voltage jump can cause damage to the cavity system if the voltage at the time of extraction is high. Therefore, we prepared a logic to suppress the output synchronously with the beam extraction as a function of the LLRF control system. The details of the function and test results are reported.
Adachi, Kyosuke; Tamura, Fumihiko; Nomura, Masahiro; Shimada, Taihei; Miyakoshi, Ryosuke*; Okita, Hidefumi; Yoshii, Masahito*; Omori, Chihiro*; Seiya, Kiyomi*; Hara, Keigo*; et al.
Proceedings of 21st Annual Meeting of Particle Accelerator Society of Japan (Internet), p.543 - 546, 2024/10
no abstracts in English
Adachi, Taihei*; Ikedo, Yutaka*; Nishiyama, Kusuo*; Yabuuchi, Atsushi*; Nagatomo, Takashi*; Strasser, P.*; Ito, Takashi; Higemoto, Wataru; Kojima, Kenji*; Makimura, Shunsuke*; et al.
JPS Conference Proceedings (Internet), 8, p.036017_1 - 036017_4, 2015/09
Tani, Norio; Kanazawa, Kenichiro; Shimada, Taihei; Suzuki, Hiromitsu; Watanabe, Yasuhiro; Adachi, Toshikazu*; Someya, Hirohiko*
Proceedings of 8th European Particle Accelerator Conference (EPAC 2002), p.2376 - 2378, 2002/00
The 3-GeV synchrotron proposed in the JAERI/KEK Joint Project is a rapid-cycling synchrotron (RCS), which accelerates a high-intensity proton beam from 400 MeV to 3 GeV at a repetition rate of 25 Hz. The 3-GeV synchrotron is used to produce pulsed spallation neutrons and muons. It also works as an injector for a 50-GeV synchrotron. Since the magnets for the 3-GeV synchrotron are required to have a large aperture in order to realize the large beam power of 1 MW, there is a large leakage field at an end part than a usual synchrotron magnet. In addition, 25-Hz ac field induces an eddy current in magnet components: e.g. a coil, magnet end plates and etc. We intend to use a stranded conductor as a coil conductor so that the eddy current induced in the coil can be reduced. On the other hand, the eddy current induced in the end plates is expected to be large. Therefore, it is important to investigate an effect of the large leakage field and the eddy current to the beam motion around the magnet end part. We have constructed a prototype dipole magnet and field measurement system for this purpose. This paper reports the results of the design and the preliminary test about this magnet.
Adachi, Kyosuke; Tamura, Fumihiko; Nomura, Masahiro; Shimada, Taihei; Okita, Hidefumi; Yoshii, Masahito*; Omori, Chihiro*; Seiya, Kiyomi*; Hara, Keigo*; Hasegawa, Katsushi*; et al.
no journal, ,
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.
no journal, ,
The J-PARC 3GeV Synchrotron (RCS) has achieved user operation at a design beam power of 1MW. The RF acceleration system of the RCS has contributed to minimizing beam loss in high-intensity beams by utilizing the characteristics of magnetic alloy (MA) cavities, which are capable of generating high acceleration voltages and have wideband frequency responses, and by mitigating space charge effects through bunch shaping using the second harmonics. It is also necessary to address issues specific to wideband cavities. In this presentation, we discuss these issues and their solutions. It also reports on efforts to achieve beam power exceeding the design beam power.
Adachi, Kyosuke; Tamura, Fumihiko; Nomura, Masahiro; Shimada, Taihei; Miyakoshi, Ryosuke*; Okita, Hidefumi; Yoshii, Masahito*; Omori, Chihiro*; Seiya, Kiyomi*; Hara, Keigo*; et al.
no journal, ,
no abstracts in English
