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Naoe, Takashi; Kinoshita, Hidetaka; Kogawa, Hiroyuki; Wakui, Takashi; Wakai, Eiichi; Haga, Katsuhiro; Takada, Hiroshi
JPS Conference Proceedings (Internet), 28, p.081004_1 - 081004_6, 2020/02
The beam window of the mercury target vessel in J-PARC is severely damaged by the cavitation. The cavitation damage is a crucial factor to limit lifetime of the target because it increases with the beam power. Therefore, mitigating cavitation damage is an important issue to operate the target stably for long time at 1 MW. At J-PARC, to mitigate the cavitation damage: gas microbubbles are injected into mercury for suppressing pressure waves, and double-walled structure with a narrow channel of 2 mm in width to form high-speed mercury flow (
4m/s) has been adopted. After operation, the beam window was cut to inspect the effect of the cavitation damage mitigation on inner wall. We optimized cutting conditions through the cold cutting tests, succeeding in cutting the target No.2 (without damage mitigation technologies) smoothly in 2017, and target No.8 with damage mitigation technologies. In the workshop, progress of cavitation damage observation for the target vessel will be presented.
Takada, Hiroshi; Haga, Katsuhiro; Teshigawara, Makoto; Aso, Tomokazu; Meigo, Shinichiro; Kogawa, Hiroyuki; Naoe, Takashi; Wakui, Takashi; Oi, Motoki; Harada, Masahide; et al.
Quantum Beam Science (Internet), 1(2), p.8_1 - 8_26, 2017/09
At the Japan Proton Accelerator Research Complex (J-PARC), a pulsed spallation neutron source provides neutrons with high intensity and narrow pulse width to promote researches on a variety of science in the Materials and life science experimental facility. It was designed to be driven by the proton beam with an energy of 3 GeV, a power of 1 MW at a repetition rate of 25 Hz, that is world's highest power level. A mercury target and three types of liquid para-hydrogen moderators are core components of the spallation neutron source. It is still on the way towards the goal to accomplish the operation with a 1 MW proton beam. In this paper, distinctive features of the target-moderator-reflector system of the pulsed spallation neutron source are reviewed.
Ikeda, Tsubasa; Kogawa, Hiroyuki; Naoe, Takashi; Kawamura, Shunsuke; Tanaka, Nobuatsu*; Futakawa, Masatoshi
no journal, ,
In the mercury target of the pulsed spallation neutron source at J-PARC, pressure waves are generated by the high-intensity pulsed-proton beam bombardment, resulting in inducing cavitation. Because the cavitation causes severe erosion damages on the mercury enclosure vessel made of stainless steel, suppressing the pressure waves and the cavitation are crucial issues to realize stable target operations at rated proton beam power of 1 MW. Gas microbubbles injection into flowing mercury is one of the prospective techniques to suppress pressure waves. At the J-PARC, a swirl-flow bubble-generator has been developed to generate microbubbles and installed in the mercury target. In order to improve the performance of the pressure wave suppression by increasing the amount of microbubbles, effects of the vane angle and throttling ratio of the Venturi on the amount of microbubbles were parametrically investigated through water experiments. The experimental results showed that the amount of the microbubbles was increased with decreasing the throttling ratio of the Venturi.
