Characterization of liquid targets in Vacuum condition

Yamamoto, Kazami; Ogiwara, Norio*; Kuramochi, Masaya*

e-Journal of Surface Science and Nanotechnology (Internet), 21(4), p.359 - 364, 2023/07

https://doi.org/10.1380/ejssnt.2023-053

In recent years, durable target is required according to increase of the beam power. To solve this problem, a liquid film was formed in vacuum and tested it as a target. An ethanol and a mercury were selected as liquid target materials, and we investigated whether the liquid sheet could be formed stably in a vacuum and how about the vacuum pressure. As a result, it was confirmed that the liquid films were stably formed in both case and the pressures with the films were about the vapor pressure of the materials.

Report of the design examination and the installation work for the radiation shield at the beam injection area in the 3 GeV synchrotron

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

JAEA-Technology 2021-019, 105 Pages, 2021/11

JAEA-Technology-2021-019.pdf:10.25MB

Since a user operation startup, the 3 GeV 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, such as the magnet, vacuum chambers, beam monitors, etc., 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 organized a task force for the installation of the shield. The task force has aimed to optimize the structure of the radiation shield, construct the installation procedure with due consideration of the worker's dose suppression. As the examination result of the shield design, 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 renewal work required to install the shielding 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. It was a large-scale work to occupy the beam injection area during almost of the summer maintenance period. However, it is considered very meaningful for dose suppression in future maintenance works.

Development of a new detector system to evaluate position and activity of plutonium particles in nasal cavities

Morishita, Yuki; Yamamoto, Seiichi*; Momose, Takumaro; Kaneko, Junichi*; Nemoto, Norio

Radiation Protection Dosimetry, 178(4), p.414 - 421, 2018/03

https://doi.org/10.1093/rpd/ncx127

Plutonium dioxide (PuO) is used to fabricate a mixed oxide fuel for fast breeder reactors. When a glove box containing PuO fails, such as by rupture of a glove or a vinyl bag, airborne contamination of plutonium (Pu) can occur. If the worker inhale PuO particles, they deposit in the lung and cause lung cancer. The nasal smear and nose blow methods are useful for checking workers for PuO intake in the field. However, neither method can evaluate the quantitative activity of Pu. No alpha-particle detector that can be used for direct measurements in the nasal cavity has been developed. Therefore, we developed a nasal monitor capable of directly measuring the activity of Pu in the nasal cavity to precisely evaluate the internal exposure dose of a worker. Prismatic-shaped 22 acrylic light guides were used to compose a detector block, and a ZnS(Ag) scintillator was adhered to the surface of these light guides. Silicon photomultiplier (SiPM) arrays with 88 channels were used as a photodetector. Actual PuO particles were measured using the nasal monitor. The nasal monitor could be directly inserted in the nasal cavities. The activity distribution of Pu was obtained by the nasal monitor. The average efficiencies in 4 were 11.43% and 11.58% for the left and right nasal cavities, respectively. The effect of and rays on the detection of the alpha particles of Pu was negligible. The difference in the measured Pu activity between the ZnS(Ag) scintillation counter and the nasal monitor was within 4.0%. The developed nasal monitor can solve the uncertainty problem encountered with the nasal smear and the nose blow methods. We expect this monitor to be useful for accurately estimating the internal exposure dose of workers.

Development of a gas-sheet target for a non-destructive profile monitor

Ogiwara, Norio; Hikichi, Yusuke*; Kamiya, Junichiro; Yamamoto, Kazami; Kinsho, Michikazu

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.563 - 567, 2017/12

Achievement of a low-loss 1-MW beam operation in the 3-GeV rapid cycling synchrotron of the Japan Proton Accelerator Research Complex

Hotchi, Hideaki; Harada, Hiroyuki; Hayashi, Naoki; Kato, Shinichi; Kinsho, Michikazu; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; et al.

Physical Review Accelerators and Beams (Internet), 20(6), p.060402_1 - 060402_25, 2017/06

AA2017-0154.pdf:4.88MB

https://doi.org/10.1103/PhysRevAccelBeams.20.060402

The 3-GeV rapid cycling synchrotron (RCS) of the Japan Proton Accelerator Research Complex (J-PARC) is the world's highest class of high-power pulsed proton driver, aiming for an output beam power of 1 MW. The most important issues in realizing such a high-power beam operation are to control and minimize beam loss for maintaining machine activations within permissible levels. In RCS, numerical simulation was successfully utilized along with experimental approaches to isolate the mechanism of beam loss and find its solution. By iteratively performing actual beam experiments and numerical simulations, and also by several hardware improvements, we have recently established a 1-MW beam operation with very low fractional beam loss of a couple of 10. In this paper, our recent efforts toward realizing such a low-loss high-intensity beam acceleration are presented.

Theoretical elucidation of space charge effects on the coupled-bunch instability at the 3 GeV Rapid Cycling Synchrotron at the Japan Proton Accelerator Research Complex

Shobuda, Yoshihiro; Chin, Y. H.*; Saha, P. K.; Hotchi, Hideaki; Harada, Hiroyuki; Irie, Yoshiro*; Tamura, Fumihiko; Tani, Norio; Toyama, Takeshi*; Watanabe, Yasuhiro; et al.

Progress of Theoretical and Experimental Physics (Internet), 2017(1), p.013G01_1 - 013G01_39, 2017/01

AA2016-0375.pdf:3.07MB

https://doi.org/10.1093/ptep/ptw169

The Rapid Cycling Synchrotron (RCS), whose beam energy ranges from 400 MeV to 3 GeV and which is located in the Japan Proton Accelerator Research Complex, is a kicker-impedance dominant machine, which violates the impedance budget from a classical viewpoint. Contrary to conventional understanding, we have succeeded to accelerate a 1-MW equivalent beam. The machine has some interesting features: for instance, the beam tends to be unstable for the smaller transverse beam size, the beam is stabilized by increasing the peak current . Space charge effects play an important role in the beam instability at the RCS. In this study, a new theory has been developed to calculate the beam growth rate with the head-tail and coupled-bunch modes () while taking space charge effects into account. The theory sufficiently explains the distinctive features of the beam instabilities at the RCS.

Conceptual design of main magnets for the J-PARC RCS energy upgrade

Tani, Norio; Watanabe, Yasuhiro; Hotchi, Hideaki; Harada, Hiroyuki; Yamamoto, Masanobu; Kinsho, Michikazu; Igarashi, Susumu*; Sato, Yoichi*; Shirakata, Masashi*; Koseki, Tadashi*

Proceedings of 13th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.708 - 711, 2016/11

http://www.pasj.jp/web_publish/pasj2016/proceedings/PDF/MOP1/MOP113.pdf

At the J-PARC Main Ring (MR), there have been various investigation carried out at the moment aiming at the beam operation of MW order. As one of the investigations, a study of the Rapid-Cycling Synchrotron (RCS) magnets was implemented. Increase of the extraction energy of RCS was needed to reduce beam loss, as beam loss in the MR injection region was large under influence of Space Charge effect at the injection beam of 3GeV. Therefore conceptual design of the extraction energy upgrade using dipole and quadrupole magnets of RCS was performed. In this paper, we will report the contents of the study in extraction energy upgrade of RCS magnets and problems which became clear as a result.

Recent progress of 1-MW beam tuning in the J-PARC 3-GeV RCS

Hotchi, Hideaki; Harada, Hiroyuki; Kato, Shinichi; Kinsho, Michikazu; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Tani, Norio; Watanabe, Yasuhiro; et al.

Proceedings of 7th International Particle Accelerator Conference (IPAC '16) (Internet), p.592 - 594, 2016/06

https://doi.org/10.18429/JACoW-IPAC2016-MOPOR004

The J-PARC 3-GeV RCS achieved a 1-MW beam acceleration in January 2015. Since then, a large fraction of our effort has been focused on reducing and managing beam losses. Major part of beam loss, such as space-charge induced beam loss, was well minimized by introducing injection painting. Uncontrolled beam loss arising from large-angle foil scattering during charge-exchange injection was also reduced drastically by the expansion of the transverse painting area, which was achieved by introducing quadrupole correctors and anti-correlated painting. By such recent efforts, the 1-MW beam operation is now estimated to be established within a permissible beam loss level. This paper presents the recent progress of 1-MW beam tuning, especially focusing on our approaches to beam loss issues.

The Realignment of the beamline for J-PARC 3GeV RCS

Tani, Norio; Yamamoto, Masanobu; Kamiya, Junichiro; Hotchi, Hideaki; Kinsho, Michikazu

JPS Conference Proceedings (Internet), 8, p.012016_1 - 012016_6, 2015/09

https://doi.org/10.7566/JPSCP.8.012016

J-PARC 3GeV RCS suffered from the misalignments of several millimeters of the magnets in both horizontal and vertical directions caused by the Tohoku Region Pacific Coast Earthquake on March 11, 2011. As the result of the orbit calculation showed that the beam loss was acceptable for beam operation at 300 kW, beam operation with the current placement was implemented until May, 2013. However according to the simulation of beam loss at 1 MW operation, it was found out that the beam loss increased and the horizontal emittance expanded. Therefore it was understood that 1 MW operation was difficult without the realignment of the beamline. The realignment of the beamline was carried out from July to November, 2013 in conjunction with the upgrade of Linac. During the realignment, the adjustment of the magnets and the ceramics chambers was mainly performed. The magnets were adjusted to within 0.2 mm. The ceramics chambers were aimed to be adjusted within 0.5 mm. Beam commissioning started on January 30, 2014. RCS succeeded in injection of 400 MeV beam from the upgraded Linac and extraction of 3GeV beam to MLF. In this paper, the alignment result of the magnets and the ceramics chambers that constitute the beamline of 3 GeV RCS is reported.

Progress of injection energy upgrade project for J-PARC RCS

Hayashi, Naoki; Harada, Hiroyuki; Horino, Koki; Hotchi, Hideaki; Kamiya, Junichiro; Kinsho, Michikazu; Saha, P. K.; Shobuda, Yoshihiro; Takayanagi, Tomohiro; Tani, Norio; et al.

Proceedings of 4th International Particle Accelerator Conference (IPAC '13) (Internet), p.3833 - 3835, 2014/07

https://accelconf.web.cern.ch/accelconf/IPAC2013/papers/thpwo032.pdf

no abstracts in English