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J-PARC/MUSEにおけるミュオン回転標的の現状

Present status of muon rotating target at J-PARC/MUSE

○牧村 俊助，的場 史朗，河村 成肇（高エネ研），鬼澤 聡志，松澤 行洋（NAT），田部 正人（シーケル），小林 庸男，藤森 寛，池戸 豊，幸田 章宏，小嶋 健児，三宅 康博，中村 惇平，下村 浩一郎，ストラッサ― パトリック，門野 良典（高エネ研）

○Shunsuke Makimura, Shirou Matoba, Naritoshi Kawamura (KEK), Satoshi Onizawa, Yukihiro Matsuzawa (NAT), Masato Tabe (Seekel), Yasuo Kobayashi, Hiroshi Fujimori, Yutaka Ikedo, Akihiro Koda, Kenji Kojima, Yasuhiro Miyake, Jumpei Nakamura, Koichiro Shimomura, Patrick Strasser, Ryosuke Kadono (KEK)

A pulsed muon beam with unprecedented intensity will be generated by a 3-GeV 333-microA proton beam on a muon target made of 20-mm thick isotropic graphite at J-PARC/MUSE (Muon Science Establishment). The energy deposited by a 1-MW proton beam is estimated to be 3.9kW on the muon target. The first muon beam was successfully generated in September of 2008. Gradually upgrading the beam intensity, continuous 300-kW proton beam has been operated by a fixed target method without replacements till June of 2014. However, the lifetime of the fixed target will be less than 1 year by the proton-irradiation damage of the graphite in case of 1-MW proton beam operation. To extend the lifetime, the muon rotating target, in which the radiation damage is distributed to a wider area, had been developped. In the rotating target, the lifetime of bearing will have a dominant influence on the lifetime of the muon target. The disulfide tungsten are introduced as solid lubricant of the bearings. The muon rotating target was installed in September of 2014 and has been stabley utilized up to 500-kW proton beam. In this report, the present status of the muon rotating target will be described.