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 MLF MUSE (Muon Science Establishment). The energy deposited by a 1-MW proton beam is estimated to be 3.9kW in the muon target. The ﬁrst muon beam was successfully generated on September 26th, 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 graphite through 1-MW proton beam operation. To extend the lifetime, a muon rotating target, in which the radiation damage is distributed to a wider area, had been developed. In the rotating target, the lifetime of the bearings will have a dominant influence on the lifetime of the muon target. Disulfide tungsten is employed as solid lubricant for the bearings. The muon rotating target was installed in September, 2014. The stable operation by 500-kW proton beam has been conducted since April, 2018 without replacement. On 3rd July 2018, 935-kW proton operation for 1 hour was successfully completed. Furthermore, on 3rd July of 2019, 1-MW proton operation for 12 hours will be conducted.
In this presentation, the status and future prospect of the muon target at J-PARC MLF MUSE will be introduced.
|Working Group||WG3 : Accelerator Physics|