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Adachi, Kyosuke; Tamura, Fumihiko; Nomura, Masahiro; Shimada, Taihei; Miyakoshi, Ryosuke*; Okita, Hidefumi; Yoshii, Masahito*; Omori, Chihiro*; Seiya, Kiyomi*; Hara, Keigo*; et al.
JPS Conference Proceedings (Internet), 45, p.011121_1 - 011121_8, 2026/06
no abstracts in English
Tamura, Fumihiko; Okita, Hidefumi; Hotchi, Hideaki*; Saha, P. K.; Sato, Yoichi*; Yoshii, Masahito*; Omori, Chihiro*; Yamamoto, Masanobu; Seiya, Kiyomi*; Sugiyama, Yasuyuki*; et al.
JPS Conference Proceedings (Internet), 45, p.011129_1 - 011129_7, 2026/06
The current goal of the J-PARC Main Ring (MR) is an output beam power of 1.3 MW, with a beam intensity is 3.3e14 protons per pulse (ppp) at a repetition period is 1.16 s. The Rapid Cycling Synchrotron (RCS) delivers two bunches to the MR in each injection and eight bunches are accumulated in the MR with four injections. The harmonic number of the RCS is 2 and the maximum nunch intensity of the RCS is 4.2e13 protons per bunch (ppb). If the harmonic number of the RCS is set to 1 and the RCS can accelerate a single bunch with the same intensity of 8.3e13 ppp/ppb, the bunch intensity in the MR can be doubled to 8.3e13 ppb, which corresponds to the accumulated beam intensity of 6.6e14 ppp with eight bunches. In this presentation, the feasibility of single bunch acceleration in the RCS is discussed based on the longitudinal beam simulations.
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; 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
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
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
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.
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; Okita, Hidefumi; Yoshii, Masahito*; Omori, Chihiro*; Seiya, Kiyomi*; Hara, Keigo*; Hasegawa, Katsushi*; et al.
no journal, ,
no abstracts in English
