Status and Future Prospect of Muon Target at J-PARC MLF

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 first muon beam was successfully produced on September 26th, 2008. To extend the lifetime of the muon target, muon rotating target, in which the radiation damage is distributed to a wider area, was installed in September of 2014. The rotating target has been successfully used for five years without replacement. Meanwhile, the failure on the rotation system that leads the possibility of the loss of the transmission was found during the long-shutdown in September of 2018. The rotating target had been operated with the careful monitoring and the measures in preparation for the loss of the transmission from September 2018 to July 2019. In this report, the trouble of the rotation system and the measures at J-PARC MLF MUSE will be introduced.