Single bunch injection scheme for doubling the beam intensity of J-PARC Main Ring

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

https://doi.org/10.7566/JPSCP.45.011129

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.

Operational experience of single-ended magnetic alloy cavities at J-PARC RCS

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

https://www.pasj.jp/web_publish/pasj2025/proceedings/PDF/WEP0/WEP032.pdf

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.

Consideration for improving the longitudinal beam matching between RCS and MR at the J-PARC

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

https://doi.org/10.1088/1742-6596/3094/1/012027

no abstracts in English

Mitigation of cavity voltage jump due to high intensity beam extraction in J-PARC RCS

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

https://www.pasj.jp/web_publish/pasj2024/proceedings/PDF/THP0/THP071.pdf

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.

Effect of grain boundary on the friction coefficient of pure Fe under the oil lubrication

Adachi, Nozomu*; Matsuo, Yasutaka*; Todaka, Yoshikazu*; Fujimoto, Mikiya*; Hino, Masahiro*; Mitsuhara, Masatoshi*; Oba, Yojiro; Shiihara, Yoshinori*; Umeno, Yoshitaka*; Nishida, Minoru*

Tribology International, 155, p.106781_1 - 106781_9, 2021/03

https://doi.org/10.1016/j.triboint.2020.106781

Performance evaluation of the European Committee Standardization Method EN1785 for the detection of irradiated processed food

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

https://doi.org/10.5986/jrafi.49.9

no abstracts in English

Resonant inelastic X-ray scattering study of intraband charge excitations in hole-doped high- cuprates

Wakimoto, Shuichi; Ishii, Kenji; Kimura, Hiroyuki*; Ikeuchi, Kazuhiko*; Yoshida, Masahiro*; Adachi, Tadashi*; Casa, D.*; Fujita, Masaki*; Fukunaga, Yasushi*; Gog, T.*; et al.

Physical Review B, 87(10), p.104511_1 - 104511_7, 2013/03

https://doi.org/10.1103/PhysRevB.87.104511

Recent progress in the energy recovery linac project in Japan

Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05

http://accelconf.web.cern.ch/AccelConf/IPAC10/papers/tupe091.pdf

Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.

Monte Carlo particle trajectory simulation for classification of C cluster ion structure utilizing coulomb explosion imaging

Adachi, Masahiro; Saito, Yuichi; Chiba, Atsuya; Narumi, Kazumasa; Yamada, Keisuke; Kaneko, Toshiaki*

Radiation Physics and Chemistry, 77(10-12), p.1328 - 1332, 2008/10

https://doi.org/10.1016/j.radphyschem.2008.05.049

no abstracts in English

Average charge and its structure dependence of fragment ions under irradiation of a thin carbon foil with a 1-MeV/atom C cluster ion

Chiba, Atsuya; Saito, Yuichi; Narumi, Kazumasa; Adachi, Masahiro; Kaneko, Toshiaki*

Physical Review A, 76(6), p.063201_1 - 063201_6, 2007/12

https://doi.org/10.1103/PhysRevA.76.063201

The charge states of fragment ions were measured for 1-MeV/atom C cluster ions penetrating a carbon foil of 2.4-g/cm thickness. Those ions were detected with a luminance plate detector monitored by a CCD camera. The detected ion signals were traced by coulomb explosion imaging technique, which enabled us to classify charge states of each fragment ion and spatial structure of a cluster ion on emerging from the foil. Using this technique, for the first time, we found that (1) the measured average charges of the fragment ions in a triangular structure are smaller than those in a linear-chain structure, and (2) the edge-position ions in a linear structure have the average charges greater than the middle-position ion. These experimental results are well supported by a recent theory on the cluster average charge.