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Inukai, Munehiro*; Horike, Satoshi*; Itakura, Tomoya*; Shinozaki, Ryota*; Ogiwara, Naoki*; Umeyama, Daiki*; Nagarker, S.*; Nishiyama, Yusuke*; Malon, M.*; Hayashi, Akari*; et al.
Journal of the American Chemical Society, 138(27), p.8505 - 8511, 2016/07
Times Cited Count：135 Percentile：95.46(Chemistry, Multidisciplinary)Kamiya, Junichiro; Ogiwara, Norio; Hotchi, Hideaki; Hayashi, Naoki; Kinsho, Michikazu
Nuclear Instruments and Methods in Physics Research A, 763, p.329 - 339, 2014/11
Times Cited Count：5 Percentile：38.03(Instruments & Instrumentation)One of the main sources of beam loss in high power accelerators is unwanted stray magnetic fields from magnets near the beam line, which can distort the beam orbit. The most effective way to shield such magnetic fields is to perfectly surround the beam region without any gaps with a soft magnetic high permeability material. This leads to the manufacture of vacuum chambers (beam pipes and bellows) with soft magnetic materials. Using this heat treatment, the ratio of the integrated magnetic flux density along the beam orbit between the inside and outside of the beam pipe and bellows became small enough to suppress beam orbit distortion. The outgassing rate of the materials with this heat treatment was reduced by one order magnitude compared to that without heat treatment. By installing the beam pipes and bellows of soft magnetic materials as part of the Japan Proton Accelerator Research Complex 3 GeV rapid cycling synchrotron beam line, the closed orbit distortion was reduced by more than 80%. In addition, a 95.5% beam survival ratio was achieved by this COD improvement.
Kamiya, Junichiro; Kinsho, Michikazu; Hayashi, Naoki; Hotchi, Hideaki; Ogiwara, Norio; Tani, Norio; Watanabe, Yasuhiro
Journal of the Vacuum Society of Japan, 57(4), p.131 - 135, 2014/04
In J-PARC 3GeV synchrotron (RCS), new quadrupole magnets (quadrupole correctors) are planned to be installed in order to correct the edge focusing effect and tune. In this report, we describe a deliberation flow about the design of the beam ducts, which are installed in the quadrupole corrector. The effects of eddy current were examined in the case of the titanium duct. The calculated results showed that the temperature rise was too much (up to over 350
C) and the magnetic field in the beam duct is largely distorted. Therefore we decided to employ alumina ceramics beam ducts. The stress and displacement, which are caused by the atmospheric pressure, were estimated by simulating the realistic equipments in the beam line. It was found that there was no large stress and displacement by installing the alumina ceramics duct.
Kamiya, Junichiro; Ogiwara, Norio; Hayashi, Naoki; Hotchi, Hideaki; Yoshimoto, Masahiro; Kinsho, Michikazu
Journal of the Vacuum Society of Japan, 55(3), p.100 - 103, 2012/03
It is necessary to reduce the beam loss in the high power beam accelerators. One of the reasons of the beam loss is the leakage magnetic field from the beam line magnet, which distorts the beam orbit and makes the beam hit the wall of the beam pipe. The most effective way to shield such leakage field is to cover the beam by the magnetic materials at the nearest space. We decided to apply this method to the vacuum chambers of the straight section of the J-PARC 3 GeV synchrotron, where the effect of the leakage magnetic field to the beam orbit is evident. However, there is few proven evidence of the vacuum chambers of the magnetic material. Therefore we clarify the problems in producing vacuum chambers and bellows, which satisfy the magnetic and vacuum performance. In this article, we deliver the over view of the magnetic shielding project and our approaches to the problems in producing the vacuum chambers of new material.
Yamamoto, Kazami; Kamiya, Junichiro; Ogiwara, Norio; Kinsho, Michikazu; Hayashi, Naoki; Saeki, Riuji; Sato, Kenichiro*; Toyama, Takeshi*
Applied Surface Science, 256(4), p.958 - 961, 2009/11
Times Cited Count：2 Percentile：11.75(Chemistry, Physical)The Japan Proton Accelerator Research Complex (J-PARC) project is a joint project of Japan Atomic Energy Agency (JAEA) and High Energy Accelerator Research Organization (KEK). The accelerator complex of J-PARC consists of a 181 MeV Linac, a 3 GeV Rapid-Cycling Synchrotron (RCS) and a 50 GeV Main Ring (MR). The RCS ring is designed to support 1 MW of beam and to deliver a 3 GeV pulsed proton beam to the spallation neutron target and the MR at a repetition rate of 25 Hz. Since the RCS finally accelerates very high intensity beam, the secondary electron cloud may affect the accelerator performance. The electron cloud effect in RCS was evaluated by simulations, but the secondary electron emission yield (SEY) of the chamber surface and beam loss point, lost proton number were assumed. In this Study we measured the SEY from the samples which was dealt with similar process of an actual chamber surface. We estimate the practical influence of the secondary electron cloud during beam operation.
Kusakawa, Tomoyuki*; Tsukamoto, Takashi*; Kawachi, Naoki; Ishii, Satomi; Ito, Sayuri; Suzui, Nobuo; Fujimaki, Shu; Ishioka, Noriko; Horiuchi, Naomi*; Ogiwara, Isamu*
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no abstracts in English
Kamiya, Junichiro; Ogiwara, Norio; Hotchi, Hideaki; Hayashi, Naoki; Kinsho, Michikazu
no journal, ,
One of the reasons of beam loss in the RCS of J-PARC is unwanted stray magnetic field originating from magnets at the beam extraction line, which distorts the beam orbit so that the beam partially hit a vacuum chamber wall. It is required to shield the unwanted external magnetic field to less than one-tenth. The most effective way to shield such magnetic field is to cover the beam region by magnetic materials. We've developed a vacuum chamber of soft magnetic materials with high permeability. Considering the read availability of a material and fabrication yield, we decided to make the beam ducts and the bellows by a combination of permalloy PC, SUS430 and SUS316L. The magnetic shielding characteristic of these vacuum equipments is measured by taking the magnetic field mapping inside. The required magnetic shielding performance was achieved. After installing these vacuum equipments in the accelerator, we achieve the beam loss reduction by the vacuum chambers of magnetic materials.
