Recent Status & Improvements of the RCS Vacuum System

Abstract

Challenges for achieving an ultrahigh vacuum (UHV) in J-PARC 3 GeV rapid cycling synchrotron (RCS) come from the large thermal and dynamic outgassing. Turbomolecular pump (TMP) was selected as the main vacuum pump because it can evacuate such outgassing with a constant pumping speed in the wide pressure range. Through the operation of the RCS vacuum system, it has been demonstrated that the UHV was stably achieved in all parts of the ring, and the dynamic outgassing originated from the high-power proton beam was effectively pumped down. Efforts to increase the system reliability have also been continuously done, such as TMP system improvement, which means the developments of long cable specification and tough bearing against the free-run touch down trouble, installation of the non-evaporable getter pumps to evacuate the residual gas such as hydrogen and water vapor, the systemization of the vacuum control system of the beam transport line. We report the summary of the recent operation status the improvements of the RCS vacuum system.