J-PARC LINAC 50 Hz operation verification study

Kondo, Yasuhiro; Chimura, Motoki; Cicek, E.*; Fukui, Yuji*; Futatsukawa, Kenta*; Fuwa, Yasuhiro; Goto, Rikuto*; Hirano, Koichiro; Ishikawa, Masaki*; Ito, Takashi; et al.

Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.124 - 129, 2026/03

https://www.pasj.jp/web_publish/pasj2025/proceedings/PDF/FRO6/FRO601.pdf

Various upgrade plans of the J-PARC linac are underway, and repetition-rate doubling project is one of the most important part. Currently, the linac supplies a 400~MeV H ion beam to the 3~GeV synchrotron (RCS) at a repetition rate of 25~Hz. However, to deliver the beam to both RCS and proton-beam irradiation facility under planning, it is necessary to raise the repetition rate from 25~Hz to 50~Hz. Prior to construction of the beamline to the irradiation facility, we conducted a verification of the 50~Hz operation of all the linac apparatus simultaneously within the current operational limits in May 2025. And also, the verification of the 50~Hz operation of the particle counter system, which is one of the most important safety device of the J-PARC accelerator, was conducted. As a result, any significant problems were not found out, and it is now ready for the upcoming 50~Hz-beam acceleration demonstration. This paper describes this details of the demonstration of the 50~Hz operation, without beam acceleration, of the J-PARC linac.

Progress in linac beam commissioning for high-intensity operations for J-PARC power upgrades

Liu, Y.*; Otani, Masashi*; Miyao, Tomoaki*; Nakazawa, Yuga*; Shibata, Takanori*; Nammo, Kesao*; Fang, Z.*; Futatsukawa, Kenta*; Fukui, Yuji*; Mizobata, Satoshi*; et al.

Proceedings of 16th International Particle Accelerator Conference (IPAC25) (Internet), p.855 - 857, 2025/11

https://doi.org/10.18429/JACoW-IPAC2025-TUAD1

Degradation of a lithium cobalt oxide cathode under high voltage operation at an interface with an oxide solid electrolyte

Ito, Kotaro*; Tamura, Kazuhisa; Shimizu, Keisuke*; Yamada, Norifumi*; Watanabe, Kenta*; Suzuki, Kota*; Kanno, Ryoji*; Hirayama, Masaaki*

RSC Applied Interfaces (Internet), 1(4), p.790 - 799, 2024/04

https://doi.org/10.1039/D3LF00251A

LiCoO is widely used as a cathode material in lithium-ion batteries. However, the reversible capacity of LiCoO at high voltage is not well known because of the oxidative degradation of the electrolyte. In this study, a thin-film all-solid-state battery was fabricated with epitaxially grown LiCoO cathode and LiPO solid electrolyte as a model battery that operates stably at high voltages, ranging up to 4.6 V, without drastic degradation. However, the charge-discharge capacities of the battery decreased with cycling at 4.7 V. synchrotron X-ray diffraction studies revealed that LiCoO was deactivated via a change in its crystal structure to O1 type, with narrow interlayer distances, at 4.7 V. The reduced distance between the interlayers in the O1 structure possibly prevents the re-intercalation of Li ions, leading to irreversibility.

Stable photoelectrochemical reactions at solid/solid interfaces toward solar energy conversion and storage

Watanabe, Kenta*; Horisawa, Yuhei*; Yoshimoto, Masataka*; Tamura, Kazuhisa; Suzuki, Kota*; Kanno, Ryoji*; Hirayama, Masaaki*

Nano Letters, 24(6), p.1916 - 1922, 2024/02

https://doi.org/10.1021/acs.nanolett.3c03982

Electrochemistry has extended from reactions at solid/liquid interfaces to those at solid/solid interfaces. In this study, we achieve the stable photoelectrochemical reaction at the semiconductor-electrode/solid-electrolyte interface in Nb-doped anatase-TiO (a-TiO:Nb)/LiPO (LPO)/Li all-solid-state cell. The oxidative currents of a-TiO:Nb/LPO/Li increase upon light irradiation when a-TiO:Nb is located at a potential that is more positive than its flat-band potential. The photoelectrochemical reaction at the semiconductor/solid-electrolyte interface is driven by the same principle as that at semiconductor/liquid-electrolyte interfaces. Thus, we extend photoelectrochemistry to all-solid-state systems composed of solid/solid interfaces.

Experiences in dismantlement of gloveboxes for wet recovery and other use that are contaminated with nuclear fuel materials

Kitamura, Akihiro; Hirano, Hiroshi*; Yoshida, Masato; Takeuchi, Kentaro

Hoken Butsuri (Internet), 58(2), p.76 - 90, 2023/08

https://doi.org/10.5453/jhps.58.76

The alpha contaminated gloveboxes have been dismantled for over 20 years in Plutonium Fuel Fabrication Facility. The so called wet recovery equipment gloveboxes, which recover plutonium and uranium from scrap fuel by dissolving and extracting processes, were chosen as the priority gloveboxes to be dismantled. These gloveboxes and other gloveboxes in the same room were size reduced and removed up until 2022. Also, non-radioactive ancillary facility and non-radioactive giant glovebox were removed from 2007 to 2010 for ease of glovebox dismantling activities that follows and for making waste storage spaces. Several incidents were occurred and recidivism prevention measures were implemented on each occasion. In this report, glovebox dismantling activities we conducted in the past 20 years are reviewed and lessons we have learned are summarized.

Measurement of the longitudinal bunch-shape distribution for a high-intensity negative hydrogen ion beam in the low-energy region

Kitamura, Ryo; Futatsukawa, Kenta*; Hayashi, Naoki; Hirano, Koichiro; Kondo, Yasuhiro; Kosaka, Satoshi*; Miyao, Tomoaki*; Morishita, Takatoshi; Nemoto, Yasuo*; Oguri, Hidetomo

Physical Review Accelerators and Beams (Internet), 26(3), p.032802_1 - 032802_12, 2023/03

https://doi.org/10.1103/PhysRevAccelBeams.26.032802

A bunch-shape monitor (BSM) is a useful device for performing longitudinal beam tuning using the pointwise longitudinal phase distribution measured at selected points in the beam transportation. To measure the longitudinal phase distribution of a low-energy negative hydrogen (H) ion beam, highly oriented pyrolytic graphite (HOPG) was adopted for the secondary-electron-emission target to mitigate the thermal damage due to the high-intensity beam loading. The HOPG target enabled the measurement of the longitudinal phase distribution at the center of a 3-MeV H ion beam with a high peak current of about 50 mA. The longitudinal bunch width was measured using HOPG-BSM at the test stand, which was consistent with the beam simulation. The correlation measurement between the beam transverse and longitudinal planes was demonstrated using HOPG-BSM. The longitudinal Twiss and emittance measurement with the longitudinal Q-scan method was conducted using HOPG-BSM.

The Muon linac project at J-PARC

Kondo, Yasuhiro; Kitamura, Ryo; Fuwa, Yasuhiro; Morishita, Takatoshi; Moriya, Katsuhiro; Takayanagi, Tomohiro; Otani, Masashi*; Cicek, E.*; Ego, Hiroyasu*; Fukao, Yoshinori*; et al.

Proceedings of 31st International Linear Accelerator Conference (LINAC 2022) (Internet), p.636 - 641, 2022/09

https://doi.org/10.18429/JACoW-LINAC2022-WE1AA05

The muon linac project for the precise measurement of the muon anomalous magnetic and electric dipole moments, which is currently one of the hottest issues of the elementary particle physics, is in progress at J-PARC. The muons from the J-PARC muon facility are once cooled to room temperature, then accelerated up to 212 MeV with a normalized emittance of 1.5 mm mrad and a momentum spread of 0.1%. Four types of accelerating structures are adopted to obtain the efficient acceleration with a wide beta range from 0.01 to 0.94. The project is moving into the construction phase. We already demonstrated the re-acceleration scheme of the decelerated muons using a 324-MHz RFQ in 2017. The high-power test of the 324-MHz Interdigital H-mode (IH) DTL using a prototype cavity was performed in 2021. The fabrication of the first module of 14 modules of the 1296-MHz Disk and Washer (DAW) CCL will be done to confirm the production process. Moreover, the final design of the travelling wave accelerating structure for the high beta region is also proceeding. In this paper, the recent progress toward the realization of the world first muon linac will be presented.

Fabrication and low-power test of disk-and-washer cavity for muon acceleration

Takeuchi, Yusuke*; Tojo, Junji*; Nakazawa, Yuga*; Kondo, Yasuhiro; Kitamura, Ryo; Morishita, Takatoshi; Cicek, E.*; Ego, Hiroyasu*; Futatsukawa, Kenta*; Kawamura, Naritoshi*; et al.

Proceedings of 13th International Particle Accelerator Conference (IPAC 22) (Internet), p.1534 - 1537, 2022/06

https://doi.org/doi:10.18429/JACoW-IPAC2022-TUPOMS046

The muon g-2/EDM experiment is under preparation at Japan Proton Accelerator Research Complex (J-PARC), and the muon linear accelerator for the experiment is being developed. A Disk-and-Washer (DAW) cavity will be used for the medium-velocity part of the accelerator, and muons will be accelerated from = = 0.3 to 0.7 with the operating frequency of 1.296 GHz. Machining, brazing, and low-power measurements of a prototype cell reflecting the design of the first tank of DAW were performed to identify fabrication problems. Several problems were identified, such as misalignment of washers during brazing, and some measures will be taken in the actual tank fabrication. In this paper, the results of the prototype cell fabrication will be reported.

Bunch-size measurement of the high-intensity H beam with 3 MeV by the bunch-shape monitor

Kitamura, Ryo; Futatsukawa, Kenta*; Hayashi, Naoki; Hirano, Koichiro; Kondo, Yasuhiro; Kosaka, Satoshi*; Miyao, Tomoaki*; Nemoto, Yasuo*; Morishita, Takatoshi; Oguri, Hidetomo

JPS Conference Proceedings (Internet), 33, p.011012_1 - 011012_6, 2021/03

https://doi.org/10.7566/JPSCP.33.011012

The new bunch shape monitor (BSM) is required to measure the bunch size of the high-intensity H beam with 3 MeV at the front-end section in the J-PARC linac. The carbon-nano tube wire and the graphene stick are good candidates for the target wire of the BSM, because these materials have the enough strength to detect the high-intensity beam. However, since the negative high voltage of more than a few kV should be applied to the wire in the BSM, the suppression of the discharge is the challenge to realize the new BSM. After the high-voltage test to investigate the effect of the discharge from the wire, the detection of the signal from the BSM was successful at the beam core with the peak current of 55 mA using the graphene stick. The preliminary result of the bunch-size measurement is reported in this presentation.

Development of a bunch-width monitor for low-intensity muon beam below a few MeV

Sue, Yuki*; Yotsuzuka, Mai*; Futatsukawa, Kenta*; Hasegawa, Kazuo; Iijima, Toru*; Iinuma, Hiromi*; Inami, Kenji*; Ishida, Katsuhiko*; Kawamura, Naritoshi*; Kitamura, Ryo; et al.

Physical Review Accelerators and Beams (Internet), 23(2), p.022804_1 - 022804_7, 2020/02

https://doi.org/10.1103/PhysRevAccelBeams.23.022804

A destructive monitor to measure the longitudinal bunch width of a low-energy and low-intensity muon beam was developed. This bunch-width monitor (BWM) employed microchannel plates to detect a single muon with high time resolution. In addition, constant-fraction discriminators were adopted to suppress the time-walk effect. The time resolution was measured to be 65 ps in rms using a picosecond-pulsed laser. This resolution satisfied the requirements of the muon linac of the J-PARC E34 experiment. We measured the bunch width of negative-muonium ions accelerated with a radio-frequency quadrupole using the BWM. The bunch width was successfully measured to be 54 11 ns, which is consistent with the simulation.