Japan Atomic Energy Research Institute (JAERI) and High Energy Accelerator Research Organization (KEK) have been working on the Japan Proton Accelerator Research Complex (J-PARC) project for the high intensity proton accelerators. The accelerator complex consists of the 400MeV Linac, the 3GeV Rapid-Cycling Synchrotron (RCS) and the 50 GeV Main Ring (MR). The RCS ring is designed to support 1MW of beam and to deliver the 3GeV pulsed proton beam to the spallation neutron target and the MR at a repetition rate of 25Hz.
In such high intensity accelerator, the secondary electron emission yield (SEY) from the chamber surface is important issue from the point of view of the beam instability by those secondary electron clouds. Especially the beam collimators that we install in order to localize the beam loss will become the source of the secondary electrons. We studied a carbon coating to reduce the secondary electrons from these collimators. We investigated the composition of the carbon coating and the SEY from carbon coating surface.