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Naoe, Takashi; Kinoshita, Hidetaka; Kogawa, Hiroyuki; Wakui, Takashi; Wakai, Eiichi; Haga, Katsuhiro; Takada, Hiroshi
Materials Science Forum, 1024, p.111 - 120, 2021/03
The mercury target vessel for the at the J-PARC neutron source is severely damaged by the cavitation caused by proton beam-induced pressure waves in mercury. To mitigate the cavitation damage, we adopted a double-walled structure with a narrow channel for the mercury at the beam window of the vessel. In addition, gas microbubbles were injected into the mercury to suppress the pressure waves. The front end of the vessel was cut out to inspect the effect of the damage mitigation technologies on the interior surface. The results showed that the double-walled target facing the mercury with gas microbubbles operating at 1812 MWh for an average power of 434 kW had equivalent damage to the single-walled target without microbubbles operating 1048 MWh for average power of 181 kW. The erosion depth due to cavitation in the narrow channel was clearly smaller than it was on the wall facing the bubbling mercury
Wakui, Takashi; Wakai, Eiichi; Kogawa, Hiroyuki; Naoe, Takashi; Hanano, Kohei*; Haga, Katsuhiro; Shimada, Tsubasa*; Kanomata, Kenichi*
Materials Science Forum, 1024, p.145 - 150, 2021/03
To realize a high beam power operation at the J-PARC, a mercury target vessel covered with water shroud was developed. In the first step, to realize an operation at 500 kW, the basic structure of the initial design was followed and the connection method between the mercury vessel and the water shroud was changed. Additionally, the operation at a beam power of 500 kW was realized in approximately eight months. In the second step, to realize the operation at 1 MW, the new structure in which only rear ends of vessels were connected was investigated. Cooling of the mercury vessel is used to reduce thermal stress and thick vessels of the water shroud are used to increase stiffness for the internal pressure; therefore, it was adopted. The stress in each vessel was lower than the allowable stress based on the pressure vessel code criteria prescribed in the Japan Industrial Standard, and confirmation was obtained that the operation with a beam power of 1 MW could be conducted.
Suzudo, Tomoaki
Materials Science Forum, 1024, p.87 - 94, 2021/03
Tungsten (W) is suitable for solid targets of spallation neutron source due to its high neutron yield. The prediction of radiation effects of W is, therefore, of importance; especially, the influence of solute elements are complex and are not clearly known to date. We discuss here the solute effects using the first principles and kinetic Monte Carlo calculations and show that rhenium (Re) and osmium (Os), which are nuclear transmutation products of W, can largely change the stability and mobility of radiation defects. Such influences of the solute elements seem to explain the unsolved mechanism of the microstructural evolution of W-based materials under irradiation.
Iwamoto, Yosuke; Yoshida, Makoto*; Matsuda, Hiroki; Meigo, Shinichiro; Satoh, Daiki; Yashima, Hiroshi*; Yabuuchi, Atsushi*; Shima, Tatsushi*
Materials Science Forum, 1024, p.95 - 101, 2021/03
To predict the lifetime of target materials in high-energy radiation environments at spallation neutron sources, radiation transport codes such as PHITS are used to calculate the displacements per atom (DPA) value. In this work, to validate calculated DPA values of tungsten, we implemented 0.25-mm-diameter wire sample of tungsten in a proton irradiation device with a Gifford-McMahon cryocooler and measured the defect-induced electrical resistivity changes related to the displacement cross section using 389-MeV protons at 10 K. As well as our previous results for aluminum and copper, calculated results with defect production efficiencies provided good agreements with experimental data. Based on measurements of recovery of the defects through annealing, about 85% of the damage remained at 60 K, and the same tendency is observed in other experimental result for reactor neutron irradiation.
Harjo, S.; Kawasaki, Takuro; Tomota, Yo*; Gong, W.
Materials Science Forum, 905, p.46 - 51, 2017/08
Tomota, Yo*; Sato, Shigeo*; Uchida, M.*; Xu, P. G.; Harjo, S.; Gong, W.; Kawasaki, Takuro
Materials Science Forum, 905, p.25 - 30, 2017/08
Iwamoto, Naoya*; Azarov, A.*; Oshima, Takeshi; Moe, A. M. M.*; Svensson, B. G.*
Materials Science Forum, 858, p.357 - 360, 2016/05
Yokoseki, Takashi; Abe, Hiroshi; Makino, Takahiro; Onoda, Shinobu; Tanaka, Yuki*; Kandori, Mikio*; Yoshie, Toru*; Hijikata, Yasuto*; Oshima, Takeshi
Materials Science Forum, 821-823, p.705 - 708, 2015/07
Harjo, S.; Aizawa, Kazuya; Abe, Jun*; Gong, W.; Ito, Takayoshi*; Kawasaki, Takuro; Iwahashi, Takaaki
Materials Science Forum, 777, p.12 - 18, 2014/04
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)
C and 1500C and measurements of lifetime and photoluminescenceKlahold, W. M.*; Devaty, R. P.*; Choyke, W. J.*; Kawahara, Kotaro*; Kimoto, Tsunenobu*; Oshima, Takeshi
Materials Science Forum, 778-780, p.273 - 276, 2014/02
Umeda, Takahide*; Okamoto, Mitsuo*; Arai, Ryo*; Sato, Yoshihiro*; Kosugi, Ryoji*; Harada, Shinsuke*; Okumura, Hajime*; Makino, Takahiro; Oshima, Takeshi
Materials Science Forum, 778-780, p.414 - 417, 2014/02
Times Cited Count：2 Percentile：70.37(Crystallography)Interface defects of Metal-Oxide-Semiconductors (MOSFETs) fabricated on Carbone (C) face 4H-SiC were investigated by Electrically Detected Magnet Resistance (EDMR). Gate oxide of the MOSFETs was formed by either wet-oxidation and H
annealing or dry-oxidation. The values of channel mobility for MOSFETS with wet gate oxide and dry gate oxide are less than 1 and 90 cm
/Vs, respectively. By EDMR measurement under low temperature (less than 20 K), EDMR signals related to C were detected. The peak height of the signals increased with increasing 
-ray doses, and the channel mobility decreased. From this result, it is assumed that hydrogen atoms passivating C dangling bonds are released by -rays and the channel mobility decreases with increasing the C related defects.
Suzuki, Hiroshi; Harjo, S.; Abe, Jun*; Akita, Koichi
Materials Science Forum, 777, p.105 - 111, 2014/02
Times Cited Count：1 Percentile：51.29(Materials Science, Multidisciplinary)Effects of beam divergence on pseudo-strains observed in time-of-flight (TOF) neutron diffraction, that overlapped with the neutron attenuation effect and the surface-effect were investigated. The through-surface strain scanning on an annealed steel plate was performed in different instrument resolutions by controlling the incident beam divergence. Typical pseudo-strain distributions were observed, but they showed different trend according to the beam divergence. Furthermore, it was demonstrated that the pseudo-strains induced in the strain scanning of coarse grain materials can be suppressed by controlling the incident beam divergence. Therefore, the incident beam divergence must be carefully considered to reduce pseudo-strains in time-of-flight neutron diffractometry.
-ray dose rate monitoringFujita, Natsuko; Iwamoto, Naoya; Onoda, Shinobu; Makino, Takahiro; Oshima, Takeshi
Materials Science Forum, 778-780, p.1042 - 1045, 2014/02
Times Cited Count：1 Percentile：51.29(Crystallography)A Silicon Carbide (SiC) dosimeter has been exposed to -rays emitted from a 
Co source in order to test the response of radiation-induced current in the dose rate ranging from 0.4 Gy/h to 4 kGy/h. The SiC dosimeter in this study is a high purity semi-insulating 4H-SiC with nickel and aluminum electrode. The radiation-induced currents in the dosimeter show a linear relationship with the dose rate, and are repeatable and stable.
Shibano, Junichi*; Kajiwara, Kentaro*; Tsukamoto, Takuya*; Kawai, Hirokazu*; Miura, Setsuo*; Zhang, S.*; Shobu, Takahisa; Kobayashi, Michiaki*
Materials Science Forum, 777, p.176 - 181, 2014/02
Times Cited Count：1 Percentile：51.29(Materials Science, Multidisciplinary)Iwamoto, Naoya; Onoda, Shinobu; Fujita, Natsuko; Makino, Takahiro; Oshima, Takeshi
Materials Science Forum, 778-780, p.289 - 292, 2014/02
Times Cited Count：0 Percentile：0.00(Crystallography)Deki, Manato*; Oka, Tomoki*; Takayoshi, Shodai*; Naoi, Yoshiki*; Makino, Takahiro; Oshima, Takeshi; Tomita, Takuro*
Materials Science Forum, 778-780, p.661 - 664, 2014/02
Times Cited Count：2 Percentile：70.37(Crystallography)no abstracts in English
Miyake, Keiko*; Yasuda, Tomonari*; Kato, Masashi*; Ichimura, Masaya*; Hatayama, Tomoaki*; Oshima, Takeshi
Materials Science Forum, 778-780, p.503 - 506, 2014/02
Harjo, S.; Hemmi, Tsutomu; Abe, Jun; Gong, W.; Nunoya, Yoshihiko; Aizawa, Kazuya; Ito, Takayoshi*; Koizumi, Norikiyo; Machiya, Shutaro*; Osamura, Kozo*
Materials Science Forum, 777, p.84 - 91, 2014/02
Times Cited Count：2 Percentile：70.37(Materials Science, Multidisciplinary)Deki, Manato*; Makino, Takahiro; Kojima, Kazutoshi*; Tomita, Takuro*; Oshima, Takeshi
Materials Science Forum, 778-780, p.440 - 443, 2014/02
Times Cited Count：4 Percentile：85.78(Crystallography)no abstracts in English
Suzuki, Kenji*; Shobu, Takahisa; Shiro, Ayumi; Zhang, S.*
Materials Science Forum, 777, p.155 - 160, 2014/02
Times Cited Count：3 Percentile：80.35(Materials Science, Multidisciplinary)