Present status of construction for the muon target in J-PARC

At the J-PARC muon science facility, the most intense pulsed muon beam in the world will be produced by a 3 GeV/1 MW/25 Hz proton beam on a target made of 20-mm-thick, disc-shaped, isotropic graphite (IG-43). The energy deposited by the proton beam is estimated to be 4 kW on the muon target. While the muon target is located in vacuum, the maintenance of the target must be performed from the maintenance area, which is located 4 m above floor level. In addition, a plug shield is required between the primary proton beam and the maintenance area for radiation shielding. Therefore, a huge vacuum chamber was fabricated so that the muon target and two scrapers, which are positioned downstream of the muon target for proton collimation, could be included. As the muon target and the scrapers will be highly irradiated, the replacement of these components must be performed in a remote handling room. The irradiated components will be transported to the remote handling room inserted into a shielding vessel, called the Muon Transfer Cask, which has a remote controlled gripper. In this paper, the present status of the construction for the muon target station, namely the muon target, the muon target chamber, and the muon transfer cask, will be described.