Dose-volume histogram analysis of slit-beam irradiation; Biological implications in mouse ex vivo testes

Shirato, Hiroki*; Mizuta, Masahiro*; Matsuya, Yusuke; Yokoya, Akinari*; Fukunaga, Hisanori*

Physics in Medicine & Biology, 71(14), p.145018_1 - 145018_14, 2026/07

https://doi.org/10.1088/1361-6560/ae82b1

Slit-beam irradiation (SI), a form of spatially fractionated irradiation, has been suggested to spare normal tissue through non-target effects (NTE), such as the bystander effect. However, it remains unclear whether the tissue-sparing effects (TSE) reported in previous studies arise from biological mechanisms or from physical dose volume characteristics. In this study, we analyzed a previously reported ex vivo mouse testis experiment using the PHITS code to calculate dose distributions for slit widths of 12.5, 50, and 200 m and to evaluate the corresponding biological effects. The results indicate that the Equivalent Uniform Dose (EUD) is a more appropriate metric for characterizing SI than the doses to irradiated cells, non-irradiated cells, or the entire cell population. These findings suggest that the TSE observed in previous SI studies may be explained by differences in dose-volume histograms (DVHs).

Development for temperature measurement of the stripper foil in J-PARC RCS

Yoshimoto, Masahiro; Yamada, Ippei; Nakanoya, Takamitsu; Saha, P. K.; Hatakeyama, Shuichiro; Saeki, Riuji*; Kuramochi, Masaya*; Otsu, Satoru*

Proceedings of 22nd Annual Meeting of Particle Accelerator Society of Japan (Internet), p.274 - 279, 2026/03

https://www.pasj.jp/web_publish/pasj2025/proceedings/PDF/WEP0/WEP033.pdf

To achieve a high-intensity proton beam, the J-PARC 3-GeV rapid cycling synchrotron accelerator (RCS) adopts the multi-turn charge-exchange beam injection scheme, in which the carbon stripper foils remove the electron from the injected H beam to convert the H beam. Up to now, we have demonstrated that the foils have a sufficient lifetime for continuous beam operation at the design power of 1 MW. On the other hand, we are investigating the possibility of increasing the beam power at the J-PARC further; we hope to achieve a maximum output of 2 MW at the RCS. In general, the key issue for the stripper foil at higher power beam irradiation is the shortened lifetime due to the rising foil temperature. As it reaches the sublimation temperature, it is of concern that the foil's thickness is rapidly decreasing. In this presentation, we will report the simulation result of the rising foil temperature according to the RCS beam power upgrade plan and the recent status of the study for the versatile foil temperature measurement.

Upgrade of two-dimensional scintillation neutron detectors for single crystal diffractometer SENJU at J-PARC MLF

Nakamura, Tatsuya; To, Kentaro; Kiyanagi, Ryoji; Ohara, Takashi; Hosoya, Takaaki; Tobe, Masahiro; Hishinuma, Yukio*; Ebine, Masumi; Sakasai, Kaoru

Journal of Physics; Conference Series, 3130(1), p.012002_1 - 012002_6, 2025/11

https://doi.org/10.1088/1742-6596/3130/1/012002

Upgrade of two two-dimensional scintillation neutron detectors for SENJU diffractometer at the Materials and Life science experimental Facility in the Japan Proton Accelerator Research Complex (J-PARC MLF) is underway. The current status of detector development for this project is briefly reviewed. The detector upgrade plan includes detector developments such as thin add-in detectors, high efficiency detectors to replace the original detectors, a large area detector placed under the sample vacuum tank, rectangular shaped one-bank detectors. All of these new detectors are developed based on Li:ZnS scintillators and WLS fibers. Recently, we developed a detector with a detection area four times larger than the original one (2 2 size, 512 512 mm). Based on these results, work is now underway to further expand the detector area with rectangular shape of 1 3 (256 768 mm) and 2 3 (512 768 mm). The design and experimental results of the prototype detectors will be presented.

Beam loss and beam emittance minimization at J-PARC RCS for simultaneous operation to the MLF and MR

Saha, P. K.; Harada, Hiroyuki; Shobuda, Yoshihiro; Chimura, Motoki; Okabe, Kota; Nakanoya, Takamitsu; Moriya, Katsuhiro; Yamamoto, Kazami; Tamura, Fumihiko; Okita, Hidefumi; et al.

Proceedings of 15th International Particle Accelerator Conference (IPAC'24) (Internet), p.939 - 942, 2024/07

https://doi.org/10.18429/JACoW-IPAC2024-TUAN1

Decommissioning of uranium handling facility for development of nuclear fuel manufacturing equipment

Kageyama, Tomio; Denuma, Akio; Koizumi, Jin*; Odakura, Manabu*; Haginoya, Masahiro*; Isaka, Shinichi*; Kadowaki, Hiroyuki*; Kobayashi, Shingo*; Morimoto, Taisei*; Kato, Yoshiaki*; et al.

JAEA-Technology 2022-033, 130 Pages, 2023/03

JAEA-Technology-2022-033.pdf:9.87MB

Uranium handling facility for development of nuclear fuel manufacturing equipment (Mockup room) was constructed in 1972. The Mockup room has a weak seismic resistance and is deteriorating with age. Also, the original purpose with this facility have been achieved and there are no new development plans using this facility. Therefore, interior equipment installed in this facility had been dismantled and removed since March 2019. After that, the Mockup room was inspected for contamination, and then controlled area in the Mockup room was cancelled on March 29th 2022. A total of 6,549 workers (not including security witnesses) were required for this work. The amount of non-radioactive waste generated by this work was 31,300 kg. The amount of radioactive waste generated by this work was 3,734 kg of combustible waste (103 drums), 4,393 kg of flame resistance waste (61 drums), 37,790 kg of non-combustible waste (124 drums, 19 containers). This report describes about the dismantling and removing the interior equipment in the Mockup room, the amount of waste generated by this work, and procedure for cancellation the controlled area in the facility.

Results of 1-MW operation in J-PARC 3 GeV rapid cycling synchrotron, 2

Yamamoto, Kazami; Yamamoto, Masanobu; Yamazaki, Yoshio; Nomura, Masahiro; Suganuma, Kazuaki; Fujirai, Kosuke; Kamiya, Junichiro; Nakanoya, Takamitsu; Hatakeyama, Shuichiro; Yoshimoto, Masahiro; et al.

Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.277 - 281, 2023/01

https://www.pasj.jp/web_publish/pasj2022/proceedings/PDF/TUP0/TUP004.pdf

The J-PARC 3GeV Rapid Cycling Synchrotron (RCS) is aiming to provide the proton beam of very high power for neutron experiments and the main ring synchrotron. We have continued the beam commissioning and the output power from RCS have been increasing. In recent years, we have been trying continuous supply of 1-MW high-intensity beam, which is the design value, to a neutron target. We tried to operate continuously for over 40 hours in June 2020. However, some trouble occurred and the operation was frequently suspended. In June 2021, we tried again 1-MW operation but it was suspended due to deterioration of the cooling water performance. Last summer shutdown period, we recovered performance of the cooling water system and retried in this June. In the final case, the outside temperature became extremely high. We could not keep 1-MW power, whereas 600 kW beam was delivered in stable.

Recent usage status of charge-exchange stripper foil for 3GeV synchrotron of J-PARC

Nakanoya, Takamitsu; Yoshimoto, Masahiro; Saha, P. K.; Takeda, Osamu*; Saeki, Riuji*; Muto, Masayoshi*

Proceedings of 19th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.629 - 633, 2023/01

https://ibic12.kek.jp/mirror/www.pasj.jp/web_publish/pasj2022/proceedings/PDF/WEP0/WEP042.pdf

In the J-PARC 3-GeV Rapid Cycling Synchrotron (RCS), a 400 MeV H beam injected from the linac is exchange to an H beam by a charge exchange foil and accelerated to 3 GeV. The charge exchange foils mainly used in the RCS are HBC foil (Hybrid Boron mixed Carbon stripper foil), which are made by adding a small amount of boron to carbon rods and using them as electrodes by the arc deposition method. Since 2018, foils produced by JAEA have been used for user operation. So far, no major problems have occurred due to the foils. Meanwhile, the beam power of the RCS has been gradually increased from 500 kW to 830 kW since 2018. As beam power increases, the foil issues were identified to achieve the RCS design power of 1 MW. In this paper, we will report on the recent foil usage status and issue in the user operation.

Decommissioning of Pre-dismantling Temporary Waste Storage Facility 3 (FPG-03a,b,c) in Plutonium Fuel Production Facility

Shinozaki, Masaru; Aita, Takahiro; Iso, Takahito*; Odakura, Manabu*; Haginoya, Masahiro*; Kadowaki, Hiroyuki*; Kobayashi, Shingo*; Inagawa, Takumu*; Morimoto, Taisei*; Iso, Hidetoshi; et al.

JAEA-Technology 2021-043, 100 Pages, 2022/03

JAEA-Technology-2021-043.pdf:7.49MB

It is planned that the MOX (Mixed Oxide) from the decommissioned facilities in Nuclear Fuel Cycle Engineering Laboratories is going to be consolidated and stored stably and safely for a long term in Plutonium Fuel Production Facility of the Plutonium Fuel Development Center of Nuclear Fuel Cycle Engineering Laboratories. For this purpose, it is necessary to pelletize nuclear fuel materials in the facility and store them in the assembly storage (hereinafter referred to as "waste packaging work") to secure storage space in the plutonium material storage. As a countermeasure to reduce the facility risk in this waste packing work, it was decided to construct a new powder weighing and homogenization mixing facility to physically limit the amount (batch size) of nuclear fuel materials handled at the entrance of the process. In order to secure the installation space for the new facility in the powder preparation room (1) (FP-101), the pre-dismantling temporary waste storage facility 3 (FPG-03a, b, c) was dismantled and removed. This facility consists of a granulating and sizing facility, an additive mixing facility, and a receiving and delivering guided facility, which started to be used from January 1993, and was discontinued on February 3, 2012 and became a waste facility. Subsequently, the dismantling and removal of the interior equipment was carried out by pellet fabrication section for glove operation to reduce the amount of hold-up, and before the main dismantling and removal, there was almost no interior equipment except for large machinery. This report describes the dismantling and removal of the glove box and some interior equipment and peripherals of the facility, as well as the Green House setup method, dismantling and removal procedures, and issues specific to powder process equipment (dust, etc.).

Radiation shielding installation for beam injection section of 3GeV synchrotron

Nakanoya, Takamitsu; Kamiya, Junichiro; Yoshimoto, Masahiro; Takayanagi, Tomohiro; Tani, Norio; Kotoku, Hirofumi*; Horino, Koki*; Yanagibashi, Toru*; Takeda, Osamu*; Yamamoto, Kazami

Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.238 - 242, 2021/10

Since a user operation startup, the 3GeV synchrotron accelerator (Rapid-Cycling Synchrotron: RCS) gradually reinforced the beam power. As a result, the surface dose rate of the apparatus located at the beam injection area of the RCS increases year by year. The beam injection area has many apparatuses which required manual maintenance, so reducing worker's dose is a serious issue. To solve this problem, we have decided to adopt removal shielding that could be installed quickly and easily when needed. We carried out shield installation work during the 2020 summer maintenance period. The installation work of the shield has been carried out in a under high-dose environment. For this reason, reducing the dose of workers was an important issue. So, we carefully prepared the work plan and work procedure in advance. During the work period, we implemented various dose reduction measures and managed individual dose carefully. As a result, the dose of all workers could be kept below the predetermined management value. We had installed removal shielding at the beam injection area in the 2020 summer maintenance period. We confirmed that this shield can contribute to the reduction of the dose during work near the beam injection area.

Dependence of charge-exchange efficiency on cooling water temperature of a beam transport line

Yamamoto, Kazami; Hatakeyama, Shuichiro; Saha, P. K.; Moriya, Katsuhiro; Okabe, Kota; Yoshimoto, Masahiro; Nakanoya, Takamitsu; Fujirai, Kosuke; Yamazaki, Yoshio; Suganuma, Kazuaki

EPJ Techniques and Instrumentation (Internet), 8(1), p.9_1 - 9_9, 2021/07

https://doi.org/10.1140/epjti/s40485-021-00067-6

The 3 GeV Rapid Cycling Synchrotron at the Japan Proton Accelerator Research Complex supplies a high-intensity proton beam for neutron experiments. Various parameters are monitored to achieve a stable operation, and it was found that the oscillations of the charge-exchange efficiency and cooling water temperature were synchronized. We evaluated the orbit fluctuations at the injection point using a beam current of the injection dump, which is proportional to the number of particles that miss the foil and fail in the charge exchange, and profile of the injection beam. The total width of the fluctuations was approximately 0.072 mm. This value is negligible from the user operation viewpoint as our existing beam position monitors cannot detect such a small signal deviation. This displacement corresponds to a 1.6310 variation in the dipole magnetic field. Conversely, the magnetic field variation in the L3BT dipole magnet, which was estimated by the temperature change directly, is 4.0810. This result suggested that the change in the cooling water temperature is one of the major causes of the efficiency fluctuation.