Preliminary neutronic performances of Spallation Neutron Source of Second Target Station at Materials and Life Science Experimental Facility in J-PARC

Harada, Masahide

JPS Conference Proceedings (Internet), 45, p.011042_1 - 011042_6, 2026/06

https://doi.org/10.7566/JPSCP.45.011042

At Materials and Life science Facility (MLF) in J-PARC, 3 GeV and 1MW proton beam induces a carbon target and a mercury target to provide muon beam and neutron beam, respectively. The first target station of MLF, "TS1", started to operate from 2008 and stably operates with nearby 1MW as of April 2024. As an upgrade of MLF, the second target station, "TS2", is being planned. TS2 is located near TS1 and the proton beam line to TS2 is divided at halfway to the TS1 proton beam line. Total proton beam power supplied by accelerators increases to 1.5MW. Although the repetition rate is still 25Hz, 1 of 3 pulses are transported to TS2, resulting in 8.3Hz and 0.5MW of proton beam to TS2. TS2 has a tungsten rotating target to provide both neutron and muon, and moderators to provide much higher neutron brightness by adopting higher current density of proton beam, a closer moderator position to the target, a flatter moderator and so on. Beryllium and Iron are chosen as reflector materials. The rotating target cooled by helium gas is also expected to increase neutron and muon intensities with a coexistence of them. Details of TS2 plan are summarized in Ref. In order to provide high intensity neutrons, optimization studies of TS2 were performed by the simulation code PHITS and MCNP. Finally, the coupled moderator of TS2 can provide 4 times higher intensity than that of TS1. If smaller height of moderator is chosen, brightness increases to 8 times compared with TS1. Decoupled moderators of TS2 also provide 3 time higher than that of TS1. A fixed solid target case was also compared.

Sample Radioactivity Evaluation Program (SARE) at Materials and Life Science Facility in J-PARC

Harada, Masahide; Yamaguchi, Yuji; Hashimoto, Norimichi*; Ito, Taku*; Tajima, Takahiro*; Oku, Takayuki; Haga, Katsuhiro; Ikeda, Hiroshi*; Tamura, Satoshi*

JPS Conference Proceedings (Internet), 45, p.011184_1 - 011184_4, 2026/06

https://doi.org/10.7566/JPSCP.45.011184

At Materials and Life Science Facility in J-PARC, 3 GeV and 1 MW pulsed proton beam hits mercury and carbon targets and intense neutron and muon beams are provided for various measurements. As samples in the measurements are activated, estimation of radioactivity of samples is very necessary for a radiation safety of user experiments. Therefore, estimation system, SAmple Radioactivity Evaluation program (SARE), is developed. SARE can estimate radioactivity of samples at each neutron and muon beam line with neutron flux and activation cross section. The neutron flux data was applied from references and the activation cross section data was obtained from DCHAIN-SP-2001. The activation of negative-muon can be also estimated from a database. SARE has a user-friendly interface of Web servlet based on JAVA and JAVA script and can select various conditions for the estimation. In the presentation, we will introduce SARE and validation results performed at BL10 with the foil-activation method.

Coupled dimerized alternating-bond quantum spin chains in the distorted honeycomb-lattice magnet CuSbO

Piyakulworawat, C.*; Morita, Katsuhiro*; Fukumoto, Yoshiyuki*; Hsieh, W.-Y.*; Chen, W.-T.*; Nakajima, Kenji; Kawamura, Seiko; Zhao, Y.*; Wannapaiboon, S.*; Piyawongwatthana, P.; et al.

Physical Review Research (Internet), 8(1), p.013247_1 - 013247_16, 2026/03

https://doi.org/10.1103/vdgg-d128

We analyze powder-averaged inelastic neutron scattering and magnetization data for the distorted honeycomb compound CuSbO using a first-order dimer expansion calculation and quantum Monte Carlo simulations. We show that, in contrast to the previously proposed honeycomb lattice model, CuSbO accommodates interacting dimerized spin chains with alternating ferromagnetic-antiferromagnetic couplings along the chain. Moreover, unlike the typical couplings observed in other Cu-based distorted honeycomb magnets, the spin chains in CuSbO primarily couple through an antiferromagnetic coupling that arises between the honeycomb layers, rather than the expected interchain coupling in the layers. This finding reveals a different magnetic coupling scheme for CuSbO. In addition, utilizing X-ray spectroscopy and transmission electron microscopy, we also refine the crystal structure and stacking-fault model of the compound.

Refined spin Hamiltonian on the Cairo pentagonal lattice of BiFeO

Lenander, E. Y.*; Nielsen, F. B.*; Lass, J.*; Hansen, U. B.*; Krighaar, K. M. L.*; Preuss, A.*; Weber, T.*; Enderle, M.*; Jacobsen, H.*; Stuhr, U.*; et al.

Physical Review B, 113(1), p.014424_1 - 014424_14, 2026/01

https://doi.org/10.1103/3n7r-j7wd

Operation, maintenance and technical development of cryogenic hydrogen system at MLF (JFY20182022)

Aso, Tomokazu; Ariyoshi, Gen; Muto, Hideki*; Tanaka, Shigeto*

JAEA-Technology 2025-005, 51 Pages, 2025/10

JAEA-Technology-2025-005.pdf:2.47MB

The cryogenic hydrogen system of the J-PARC center is one of the most important pieces equipment, which is a refrigeration system for moderating (cooling) the high energy neutrons generated the spallation neutron source of the Material and Life Science Experimental Facility (MLF) that is used by many users from Japan and abroad. Since the first operation of the MLF for neutron use in 2008, the cryogenic hydrogen system has been continuously operated and maintained, and related technology development has been carried out. This report summarized these activities over the past five years.

Neutron target for high-intensity operation at J-PARC MLF

Haga, Katsuhiro; Naoe, Takashi; Kogawa, Hiroyuki; Wakui, Takashi; Kinoshita, Hidetaka; Harada, Masahide

Proceedings of 16th International Particle Accelerator Conference (IPAC25) (Internet), p.3245 - 3249, 2025/06

https://doi.org/10.18429/JACoW-IPAC2025-FRXD1

In April 2024, the beam power at MLF attained 950 kW for the first time for long term user operation, and the beam power at the 3 GeV rapid cycle synchrotron (RCS) outlet was raised to 1 MW. This accomplishment means that the goal of the stable operation of the neutron source with 1 MW was almost achieved at last, and it's time to go on to the new stage of the neutron source R&D. There are two major challenges for the mercury target in the next stage. One is to attain the long-term operation of a mercury target. The service life of the target vessel is primarily determined by cavitation damage that occurs on the inner surface due to the injection of high-intensity pulsed proton beams. Until now, the vessel has been replaced annually to inspect the extent of the damage. However, based on the damage data obtained during 1 MW high-power operation, it has been determined that the vessel can withstand long-term operation for more than two years. Therefore, a new target vessel, which was replaced in 2024, is scheduled to be used for an extended period through 2027. Furthermore, since there are plans to increase the pulse intensity of the RCS in the future, it will be necessary to develop more effective pitting damage suppression techniques and new target vessels that can withstand even stronger proton beam pulses. In this presentation, the present status of the neutron source of MLF and future operation plans will be shown.

Manuals for resonance analysis code for neutron IMaging "RAIM"

Hasemi, Hiroyuki; Kai, Tetsuya

JAEA-Testing 2024-001, 39 Pages, 2024/08

JAEA-Testing-2024-001.pdf:1.4MB

RAIM is an analysis code that analyzes resonance absorption spectra measured at pulsed neutron sources such as the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC) to obtain information on nuclear densities and temperatures. By calculating the convolution of the pulse functions of neutron beam and the resonance capture function that is based on the nuclear cross section data, RAIM reproduces the resonance absorption spectrum measured by a pulsed neutron source. Then, RAIM determines the density and temperature of specific nuclides in a sample by performing spectral fitting on the resonance absorption spectrum data. In addition, RAIM is developed to facilitate the analysis of resonance imaging data by minimizing the number of parameters for calculation setup and by providing scripts for processing many resonance absorption spectra measured by a two-dimensional detector at once. This manual explains how to install RAIM on a computer and how to simulate resonance absorption spectra and fit them to measured data.

Magnetic structure and magnetoelectric properties of the spin-flop phase in LiFePO

Holm-Janas, S.*; Akaki, Mitsuru*; Fogh, E.*; Kihara, Takumi*; Le, M. D.*; Forino, P. C.*; Nikitin, S. E.*; Fennell, T.*; Painganoor, A.*; Vaknin, D.*; et al.

Physical Review B, 109(17), p.174413_1 - 174413_11, 2024/05

https://doi.org/10.1103/PhysRevB.109.174413

Measurements of neutron total and capture cross sections of La and evaluation of resonance parameters

Endo, Shunsuke; Kawamura, Shiori*; Okudaira, Takuya*; Yoshikawa, Hiromoto*; Rovira Leveroni, G.; Kimura, Atsushi; Nakamura, Shoji; Iwamoto, Osamu; Iwamoto, Nobuyuki

European Physical Journal A, 59(12), p.288_1 - 288_12, 2023/12

https://doi.org/10.1140/epja/s10050-023-01203-4

no abstracts in English

Covariance of resonance parameters ascribed to systematic uncertainties in experiments

Endo, Shunsuke; Kimura, Atsushi; Nakamura, Shoji; Iwamoto, Osamu; Iwamoto, Nobuyuki; Rovira Leveroni, G.

EPJ Web of Conferences, 281, p.00012_1 - 00012_5, 2023/03

https://doi.org/10.1051/epjconf/202328100012