Evaluation of vacuum firing effect on stainless steel from vacuum and surface point of view

Kamiya, Junichiro; Takano, Kazuhiro*; Wada, Kaoru; Yanagibashi, Toru*

e-Journal of Surface Science and Nanotechnology (Internet), 21(3), p.144 - 153, 2023/06

https://doi.org/10.1380/ejssnt.2023-015

no abstracts in English

Catalog of gamma-ray glows during four winter seasons in Japan

Wada, Yuki*; Matsumoto, Takahiro*; Enoto, Teruaki*; Nakazawa, Kazuhiro*; Yuasa, Takayuki*; Furuta, Yoshihiro*; Yonetoku, Daisuke*; Sawano, Tatsuya*; Okada, Go*; Nanto, Hidehito*; et al.

Physical Review Research (Internet), 3(4), p.043117_1 - 043117_31, 2021/12

https://doi.org/10.1103/PhysRevResearch.3.043117

Improved vacuum system for high-power proton beam operation of the rapid cycling synchrotron

Kamiya, Junichiro; Kotoku, Hirofumi*; Kurosawa, Shunta*; Takano, Kazuhiro; Yanagibashi, Toru*; Yamamoto, Kazami; Wada, Kaoru

Physical Review Accelerators and Beams (Internet), 24(8), p.083201_1 - 083201_23, 2021/08

https://doi.org/10.1103/PhysRevAccelBeams.24.083201

Through the operation of the vacuum system in J-PARC, it becomes evident that the high-power beam has more powerful effects on the vacuum system than expected. Those effects are the malfunction of vacuum equipment and the large pressure rise. The former is the failure of the turbomolecular pump (TMP) controller. The TMP itself is also damaged by a bearing crush due to a touch-down. We have developed a TMP controller that can connect with long cables of more than 200 m lengths to install the controller in a control room where there is no radiation influence. The TMP with high-strength bearing has been also developed. The latter is an extreme pressure rise with increasing the beam power. It is indicated that the pressure rise mechanism is a result of ion-stimulated gas desorption. It is finally confirmed that the dynamic pressure during the high-power beam is effectually suppressed by additionally installing the NEG pumps.

Some methods of making titanium vacuum chamber act as getter pump for UHV/XHV

Kamiya, Junichiro; Takano, Kazuhiro; Yuza, Hiromu*; Wada, Kaoru

Proceedings of 12th International Particle Accelerator Conference (IPAC 21) (Internet), p.3471 - 3474, 2021/08

https://doi.org/10.18429/JACoW-IPAC2021-WEPAB337

The NEG coating, which has been developed in CERN, is a revolutionary technique that can make a beam pipe act as a vacuum pump by coating the getter materials with the ability to adsorb/absorb gas molecules on the beam pipe surface. The NEG materials are alloys of titanium, zirconium, and vanadium. Titanium is one of the getter materials. In high-power beam accelerators, titanium has been used as the beam pipe chamber material due to its low radioactivation characteristics. The ordinal titanium surface has no getter function because it is covered with titanium-oxide film. The new technique, which removes the titanium-oxide surface by the sputtering and makes the titanium vacuum chamber itself the vacuum pump like NEG coated chamber, has been developed. After sputtering the inner surface of the titanium chamber, we obtained clear evidence that shows the chamber acts as a vacuum pump. We have also tried to make a titanium chamber with a getter function only by baking. Dependence of the getter characteristics on the baking temperature will also be reported.

Meteorological aspects of gamma-ray glows in winter thunderstorms

Wada, Yuki*; Enoto, Teruaki*; Kubo, Mamoru*; Nakazawa, Kazuhiro*; Shinoda, Taro*; Yonetoku, Daisuke*; Sawano, Tatsuya*; Yuasa, Takayuki*; Ushio, Tomoo*; Sato, Yosuke*; et al.

Geophysical Research Letters, 48(7), 11 Pages, 2021/04

https://doi.org/10.1029/2020GL091910

During three winter seasons from November 2016 to March 2019, 11 gamma-ray glows were detected at a single observation site of our ground-based gamma-ray monitoring network in Kanazawa, Japan. These events are analyzed with observations of an X-band radar network, a ceilometer, a disdrometer, and a weather monitor. All the detected glows were connected to convective high-reflectivity regions of more than 35 dBZ, developed up to an altitude of 2 km. They were also accompanied by heavy precipitation of graupels. Therefore, graupels in the lower layer of thunderclouds that correspond to high-reflectivity regions can form strong electric fields producing gamma-ray glows. Also, these events are compared with a limited sample of nondetection cases, but no significant differences in meteorological conditions were found between detection and nondetection cases in the present study.

Photonuclear reactions in lightning, 1; Verification and modeling of reaction and propagation processes

Wada, Yuki*; Enoto, Teruaki*; Nakazawa, Kazuhiro*; Odaka, Hirokazu*; Furuta, Yoshihiro; Tsuchiya, Harufumi

Journal of Geophysical Research; Atmospheres, 125(20), p.e2020JD033193_1 - e2020JD033193_17, 2020/10

https://doi.org/10.1029/2020JD033193

Photoneutron detection in lightning by gadolinium orthosilicate scintillators

Wada, Yuki*; Nakazawa, Kazuhiro*; Enoto, Teruaki*; Furuta, Yoshihiro; Yuasa, Takayuki*; Makishima, Kazuo*; Tsuchiya, Harufumi

Physical Review D, 101(10), p.102007_1 - 102007_6, 2020/05

https://doi.org/10.1103/PhysRevD.101.102007

Downward terrestrial gamma-ray flash observed in a winter thunderstorm

Wada, Yuki*; Enoto, Teruaki*; Nakazawa, Kazuhiro*; Furuta, Yoshihiro; Yuasa, Takayuki*; Nakamura, Yoshitaka*; Morimoto, Takeshi*; Matsumoto, Takahiro*; Makishima, Kazuo*; Tsuchiya, Harufumi

Physical Review Letters, 123(6), p.061103_1 - 061103_6, 2019/08

AA2018-0706.pdf:0.79MB

https://doi.org/10.1103/PhysRevLett.123.061103

Termination of electron acceleration in thundercloud by intracloud/intercloud discharge

Wada, Yuki*; Bowers, G. S.*; Enoto, Teruaki*; Kamogawa, Masashi*; Nakamura, Yoshitaka*; Morimoto, Takeshi*; Smith, D.*; Furuta, Yoshihiro*; Nakazawa, Kazuhiro*; Yuasa, Takayuki*; et al.

Geophysical Research Letters, 45(11), p.5700 - 5707, 2018/06

https://doi.org/10.1029/2018GL077784

Defect formation and accumulation in CeO irradiated with swift heavy ions

Yasuda, Kazuhiro*; Eto, Motoki*; Sawada, Kenichi*; Yamamoto, Tomokazu*; Yasunaga, Kazufumi*; Matsumura, Sho*; Ishikawa, Norito

Nuclear Instruments and Methods in Physics Research B, 314, p.185 - 190, 2013/11

https://doi.org/10.1016/j.nimb.2013.04.069

We have investigated microstructure evolution in CeO irradiated with 210 MeV Xe ions by using transmission electron microscopy to gain the fundamental knowledge on radiation damage induced by fission fragments in nuclear fuel and transmutation target.