Investigation of differences in the mean time between beam trips between normal-conducting and superconducting acceleration cavities

Takei, Hayanori

JPS Conference Proceedings (Internet), 45, p.011175_1 - 011175_7, 2026/06

https://doi.org/10.7566/JPSCP.45.011175

The Japan Atomic Energy Agency is working on the research and development of an accelerator-driven nuclear transmutation system (ADS) for transmuting minor actinides. This system is a combination of a subcritical nuclear reactor and a high-power superconducting proton linear accelerator (JADS-linac). One of the challenges in developing the JADS-linac is to reduce the number of beam trips. Until now, the beam trip frequency of the JADS-linac has been estimated from the operation data of the J-PARC linac, which uses the normal-conducting acceleration (NC) cavities. Recently, data on beam trips in the superconducting acceleration (SRF) cavities of the Spallation Neutron Source of the Oak Ridge National Laboratory (SNS) have been published. These data are important for the estimation of the beam trip frequency of the JADS-linac. Rather, the SNS data are more appropriate than the J-PARC data, because the JADS-linac uses the SRF cavities. On the other hand, the calculation methods in the published data for the NC cavities of J-PARC and the SRF cavities of SNS are different, so it is not possible to simply compare the two. In this study, the mean time between beam trips (MTBT) of the J-PARC NC cavity and the SNS SRF cavity are compared using the same condition. Specifically, the MTBT of the acceleration cavities connected to a single klystron system was calculated and compared. As a result, the MTBT of the SNS SRF cavity was 5.0 and 8.8 times longer than that of the J-PARC NC cavity for and h, respectively, where is the beam trip duration.

Effect of coaxial HPGe detector structure on -ray beam measurements

Omer, M.; Shizuma, Toshiyuki*; Koizumi, Mitsuo; Taira, Yoshitaka*; Zen, H.*; Ogaki, Hideaki*; Hajima, Ryoichi*

Radiation Physics and Chemistry, 240, p.113467_1 - 113467_8, 2026/03

https://doi.org/10.1016/j.radphyschem.2025.113467

Advancing materials studies for high-power proton accelerators in J-PARC

Makimura, Shunsuke*; Matoba, Shiro*; Sunagawa, Hikaru*; Naoe, Takashi; Wakui, Takashi; Ishida, Taku*; Matsubara, Tsurayuki*; Fukao, Yoshinori*; Takahashi, Hitoshi*; Watanabe, Hiroaki*; et al.

Proceedings of 71st ICFA Advanced Beam Dynamics workshop on High-Intensity and High-Brightness Hadron Beams (HB2025) (Internet), p.359 - 363, 2025/10

https://meow.elettra.eu/83/pdf/FRIAA01.pdf

In modern proton accelerators, the survivability of beam-intercepting devices, such as targets, beam windows and beam dumps, under intense beam irradiation is a key factor limiting the achievement of higher beam power. This article introduces the challenges faced by the secondary particle production targets and beam windows at the Japan Proton Accelerator Research Complex (J-PARC), and the developments undertaken to overcome these challenges.

A Focusing supermirror for time-of-flight grazing-incidence small-angle neutron scattering measurement

Yamazaki, Dai; Maruyama, Ryuji; Aoki, Hiroyuki; Hanashima, Takayasu*; Akutsu-Suyama, Kazuhiro*; Miyata, Noboru*; Soyama, Kazuhiko

Quantum Beam Science (Internet), 9(2), p.20_1 - 20_12, 2025/06

https://doi.org/10.3390/qubs9020020

Conceptual study of J-PARC Proton Beam Irradiation Facility

Meigo, Shinichiro; Iwamoto, Hiroki; Sugihara, Kenta*; Hirano, Yukinori*; Tsutsumi, Kazuyoshi*; Saito, Shigeru; Maekawa, Fujio

JAEA-Technology 2024-026, 123 Pages, 2025/03

JAEA-Technology-2024-026.pdf:14.22MB

Based on the design of the ADS Target Test Facility (TEF-T) at the J-PARC Transmutation Experimental Facility, a conceptual study was conducted on the J-PARC proton beam irradiation facility. This research was carried out based on the recommendations of the Nuclear Transmutation Technology Evaluation Task Force of the MEXT. The recommendations state that it is desirable to consider facility specifications that can make the most of the benefits of using the existing J-PARC proton accelerator while also solving the engineering issues of the ADS. We considered facilities that could respond to a variety of needs while reducing the facilities that were not needed in the TEF-T design. In order to clarify these diverse needs, we investigated the usage status of representative accelerator facilities around the world. As a result, it became clear that the main purposes of these facilities were (1) Material irradiation, (2) Soft error testing of semiconductor devices using spallation neutrons, (3) Production of RI for medical use, and (4) Proton beam use, and we investigated the facilities necessary for these purposes. In considering the facility concept, we assumed a user community in 2022 and reflected user opinions in the facility design. This report summarizes the results of the conceptual study of the proton irradiation facility, various needs and responses to them, the roadmap for facility construction, and future issues.

Report on research and development of neutron beam utilization at JRR-3 for internal use in FY2021 and FY2022

Materials Sciences Research Center

JAEA-Review 2024-037, 141 Pages, 2024/11

JAEA-Review-2024-037.pdf:13.08MB

Fifteen neutron beam experimental instruments managed by JAEA are installed in JRR-3 (Japan Research Reactor No.3) and are available for internal use including upgrading of instruments and for external users to produce various research results. This report summarizes the progress of internal application research and technical development such as upgrading of neutron beam instruments in the fiscal years 2021 and 2022 after the restart of operation.

Beam transient studies for the JAEA-ADS LEBT

Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Maekawa, Fujio; Meigo, Shinichiro

Proceedings of 32nd Linear Accelerator Conference (LINAC 2024) (Internet), p.488 - 491, 2024/10

https://doi.org/10.18429/JACoW-LINAC2024-TUPB076

The Japan Atomic Energy Agency (JAEA) is designing a 30-MW CW proton linear accelerator (linac) for nuclear waste transmutation. Space-charge is the primary challenge in achieving low losses and high beam quality for high-power accelerators, especially at low energy levels where space-charge forces are greater. To counteract the space-charge effects, the low-energy beam transport (LEBT) uses a magnetostatic design to enable the neutralization of the beam charge, the so-called space charge compensation. The neutralization is an accumulation process that reaches a charge balance between the main beam and the opposite ionized particles. However, this equilibrium is destroyed by the chopper system used during beam ramping. During those transient regimes, the beam optics conditions are not optimal for the beam, producing considerable degradation that can end in serious damage to the accelerator. Thus, analysis of beam behavior at these periods is essential to develop a robust design and an efficient operation of the JAEA-ADS linac. This study presents the beam dynamics of neutralization build-up and chopper operation for the JAEA-ADS LEBT.

Design of the Low energy beam transport line for the JAEA-ADS linac

Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Maekawa, Fujio; Meigo, Shinichiro

Proceedings of 20th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.545 - 549, 2023/11

https://www.pasj.jp/web_publish/pasj2023/proceedings/PDF/WEP2/WEP23.pdf

The Japan Atomic Energy Agency (JAEA) is proposing a 30-MW proton linear accelerator (linac) for the application of accelerator-driven subcritical system (ADS) technology to achieve nuclear waste transmutation. A major challenge for the JAEA-ADS linac is the efficient transport of a 35 keV proton beam from the ion source to the radio-frequency quadrupole. In order to achieve this goal, we have optimized a magnetostatic low energy beam transport (LEBT) consisting of two solenoids to reduce the transmission of high-charge ions generated by the source and minimize the growth of proton emittance, while taking into account various space-charge compensation scenarios. In this report, we present the optical design and discuss the multiparticle tracking results of the JAEA-ADS LEBT.

Measurement of H particles generated by residual gas stripping in the Japan Proton Accelerator Research Complex linac

Tamura, Jun; Futatsukawa, Kenta*; Kondo, Yasuhiro; Liu, Y.*; Miyao, Tomoaki*; Morishita, Takatoshi; Nemoto, Yasuo*; Okabe, Kota; Yoshimoto, Masahiro

Nuclear Instruments and Methods in Physics Research A, 1049, p.168033_1 - 168033_7, 2023/04

https://doi.org/10.1016/j.nima.2023.168033

The Japan Proton Accelerator Research Complex (J-PARC) linac is a high-intensity accelerator in which beam loss is a critical issue. In the J-PARC linac, H beams are accelerated to 191~MeV by a separated drift tube linac (SDTL) and subsequently to 400~MeV by an annular-ring coupled structure (ACS). Because there are more beam loss mechanisms in H linacs than in proton linacs, it is imperative to investigate the beam loss circumstances for beam loss mitigation. Electron-stripping phenomena, which generate uncontrollable H particles, are characteristic beam loss factors of H linacs. To clarify the beam loss causes in the J-PARC linac, a new diagnostic line was installed in the beam transport between the SDTL and ACS. In this diagnostic line, H particles were separated from the H beam, and the intensity profiles of the H particles were successfully measured by horizontally scanning a graphite plate in the range where H particles were distributed. By examining the intensity variation of the H particles with different residual pressure levels, we proved that half of the H particles in the SDTL section are generated by the residual gas stripping in the nominal beam operation of the J-PARC linac.

Design and beam dynamics studies of an ADS RFQ based on an equipartitioned beam scheme

Yee-Rendon, B.; Kondo, Yasuhiro; Tamura, Jun; Nakano, Keita; Maekawa, Fujio; Meigo, Shinichiro; Jameson, R. A.*

Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.499 - 502, 2023/01

https://www.pasj.jp/web_publish/pasj2022/proceedings/PDF/WEP0/WEP001.pdf

The Japan Atomic Energy Agency (JAEA) is designing a 30-MW proton linear accelerator (linac) for the accelerator-driven subcritical system (ADS). The Radio Frequency Quadrupole (RFQ) is an essential component for the performance of high-intensity linac, especially in ADS, where stringent reliability is demanded. The present RFQ will capture a 20 mA proton beam and accelerate from the energy of 35 keV to 2.5 MeV, where the space-charge effects are severe. The present RFQ's design employs the equipartitioning (EP) beam scheme to control the emittance growth and compactness. As a result, the beam halo formation was minimized and allowed to optimize the superconducting linac downstream part. A remarkable feature of this RFQ is the low Kilpatrick factor of 1.2 adopted to achieve high stability by reducing the probability of surface sparking on the vane. This work presents and discusses the results of this RFQ design.