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

Phase space formation of high intensity 60 and 80 mA H beam with orifice in J-PARC front-end

Shibata, Takanori*; Ikegami, Kiyoshi*; Nammo, Kesao*; Liu, Y.*; Otani, Masashi*; Naito, Fujio*; Shinto, Katsuhiro; Okoshi, Kiyonori; Okabe, Kota; Kondo, Yasuhiro; et al.

JPS Conference Proceedings (Internet), 33, p.011010_1 - 011010_6, 2021/03

https://doi.org/10.7566/JPSCP.33.011010

Together with the intensity upgrade in J-PARC Linac Front-End, improvement of RFQ transmission ratio is an important task. This RFQ transmission ratio depends strongly upon the solenoid current settings in the low energy beam transport line (LEBT). In the present study, high beam current cases (72 mA and 88 mA H beam current in LEBT) are investigated at a test-stand. Phase space distributions of the H beam particles at the RFQ entrance are measured and compared with numerical results by Particle-In-Cell simulation. As a result, it has been clarified that a 15 mm orifice for differential pumping of H gas coming from the ion source plays a role as a collimator in these beam conditions. This leads to change the beam emittance and Twiss parameters at the RFQ entrance. Especially in the condition with the beam current up to 88 mA in LEBT, the beam collimation contributes to optimize the phase space distribution to the RFQ acceptance with relatively low solenoid current settings. As a higher solenoid current setting would be necessary to suppress the beam expansion due to high space charge effect, these results suggest that current-saving of the solenoids can be possible even in the higher beam intensity operations.

Neutron scattering study of yttrium iron garnet

Shamoto, Shinichi; Ito, Takashi; Onishi, Hiroaki; Yamauchi, Hiroki; Inamura, Yasuhiro; Matsuura, Masato*; Akatsu, Mitsuhiro*; Kodama, Katsuaki; Nakao, Akiko*; Moyoshi, Taketo*; et al.

Physical Review B, 97(5), p.054429_1 - 054429_9, 2018/02

https://doi.org/10.1103/PhysRevB.97.054429

Nuclear and magnetic structure and full magnon dispersions of yttrium iron garnet YFeO have been studied by neutron scattering. The lowest-energy dispersion below 14 meV exhibits a quadratic dispersion as expected from ferromagnetic magnons. The imaginary part of -integrated dynamical spin susceptibility "() exhibits a square-root energy-dependence in the low energies. The magnon density of state is estimated from the "() obtained on an absolute scale. The value is consistent with a single chirality mode for the magnon branch expected theoretically.

Materials and Life Science Experimental Facility at the Japan Proton Accelerator Research Complex, 3; Neutron devices and computational and sample environments

Sakasai, Kaoru; Sato, Setsuo*; Seya, Tomohiro*; Nakamura, Tatsuya; To, Kentaro; Yamagishi, Hideshi*; Soyama, Kazuhiko; Yamazaki, Dai; Maruyama, Ryuji; Oku, Takayuki; et al.

Quantum Beam Science (Internet), 1(2), p.10_1 - 10_35, 2017/09

https://doi.org/10.3390/qubs1020010

Neutron devices such as neutron detectors, optical devices including supermirror devices and He neutron spin filters, and choppers are successfully developed and installed at the Materials Life Science Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC), Tokai, Japan. Four software components of MLF computational environment, instrument control, data acquisition, data analysis, and a database, have been developed and equipped at MLF. MLF also provides a wide variety of sample environment options including high and low temperatures, high magnetic fields, and high pressures. This paper describes the current status of neutron devices, computational and sample environments at MLF.

A 3 MeV linac for development of accelerator components at J-PARC

Kondo, Yasuhiro; Asano, Hiroyuki*; Chishiro, Etsuji; Hirano, Koichiro; Ishiyama, Tatsuya; Ito, Takashi; Kawane, Yusuke; Kikuzawa, Nobuhiro; Meigo, Shinichiro; Miura, Akihiko; et al.

Proceedings of 28th International Linear Accelerator Conference (LINAC 2016) (Internet), p.298 - 300, 2017/05

https://doi.org/10.18429/JACoW-LINAC2016-MOPLR071

We have constructed a linac for development of various accelerator components at J-PARC. The ion source is same as the J-PARC linac's, and the RFQ is a used one in the J-PARC linac. The beam energy is 3 MeV and nominal beam current is 30 mA. The accelerator has been already commissioned, and the first development program, laser-charge-exchange experiment for the transmutation experimental facility, has been started. In this paper, present status of this 3-MeV linac is presented.

Highly practical and simple ligand for separation of Am(III) and Eu(III) from highly acidic media

Suzuki, Hideya; Tsubata, Yasuhiro; Kurosawa, Tatsuya; Shibata, Mitsunobu; Kawasaki, Tomohiro; Urabe, Shunichi*; Matsumura, Tatsuro

Analytical Sciences, 32(4), p.477 - 479, 2016/04

https://doi.org/10.2116/analsci.32.477

An impeccable, high-performance new reagent called alkyl diamide amine (ADAAM) was examined from the viewpoint of mutual separation of Am(III) and Eu(III). ADAAM has three donor atoms, one soft N-donor atom and two hard O-donor atoms, in the central frame. The combination of soft and hard atoms affords a tridentate donor set of atoms that ensures remarkable extractability and selectivity of Am(III) and Eu(III) in highly acidic media.

Recent developments of instruments in a spallation neutron source at J-PARC and those prospects in the future

Arai, Masatoshi; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Nakajima, Kenji; Shibata, Kaoru; Takahashi, Nobuaki; Suzuki, Junichi*; Takata, Shinichi; Yamada, Takeshi*; et al.

Journal of the Physical Society of Japan, 82(Suppl.A), p.SA024_1 - SA024_14, 2013/01

https://doi.org/10.7566/JPSJS.82SA.SA024

The paper describes developments of neutron scattering instruments in J-PARC neutron facility, which is a short pulse spallation source operated at a repetition rate 25 Hz and has a proton power 1 MW. New concept has been adopted to utilize high intensity coupled moderator even for a high resolution inelastic scattering instruments by taking a pulse shaping chopper system. Advanced technique has been also realized by taking an ability of event-recording system altogether with an improvement of a chopper system, realizing multi-Ei method. The paper also touches upon a general design concept for diffractometers in accordance with the source characteristics.

Quasi-elastic neutron scattering of dense molecular liquid selenium bromide

Shimakura, Hironori; Kawakita, Yukinobu; Inamura, Yasuhiro; Kikuchi, Tatsuya; Ueno, Hiroki; Nakamura, Mitsutaka; Nakajima, Kenji; Kawamura, Seiko; Shibata, Kaoru*; Arai, Masatoshi; et al.

Journal of Physics; Conference Series, 340(1), p.012080_1 - 012080_6, 2012/02

https://doi.org/10.1088/1742-6596/340/1/012080

Liquid selenium bromide consists of Br-Se-Se-Br molecules, where a strong inter-molecular correlation exists so that Se-Se bond is parallel to that in neighboring molecules. Quasi-elastic neutron scattering (QENS) of SeBr was performed by cold-neutron disk-chopper spectrometer in J-PARC. Multi Ei measurement with incident energies of 3.13, 7.72 and 41.83 meV was applied. It is found that QENS can be well fitted by two Lorentzian components corresponding slow and fast relaxation modes. Integral intensity of slow component shows a maximum value at around 1.6 at room temperature and shifts to lower Q direction with increasing temperature. This shift relates to density decrease. In opposite, the HWHM of the latter has so-called de Gennes narrowing and this Q position shifts to lower Q direction with increasing temperature. This mode relates to neighboring-molecular correlation because narrowing generally occurs at Q position which exhibits strong correlation.

Technical development for in-pile IASCC growth tests by using a 0.5T-CT specimen in JMTR

Chimi, Yasuhiro; Shibata, Akira; Ise, Hideo; Kasahara, Shigeki; Kawaguchi, Yoshihiko*; Nakano, Junichi; Omi, Masao; Nishiyama, Yutaka

Proceedings of Enlarged Halden Programme Group Meeting 2011 (CD-ROM), 10 Pages, 2011/10

In order to load a large specimen of 0.5T-CT up to a high stress intensity factor of 30 MPa, we have adopted a lever type loading unit for in-pile irradiation-assisted stress corrosion crack (IASCC) growth tests in the Japan Materials Testing Reactor (JMTR). In this unit, the applied load is generated by shrinking a bellows with lower inner gas pressure than surrounding water pressure and enlarged by leverage. The crack length of the specimen is monitored by potential drop method (PDM) using mineral insulator (MI) cables. In this paper, technical concerns of the in-pile crack growth test unit, especially the estimation procedure of applied load to the specimen inside the irradiation capsule and the evaluation of precision of the PDM signals are presented.