CSRm Ultra-High Vacuum System

The new accelerator project (HIRFL-CSR) constructed at the Heavy Ion ResearchFacility in Lanzhou (HIRFL) is approaching completion. It is a multipurpose cooler-storage-ringsystem[1], consisting of a maim ring (CSRm), an experimental ring (CSRe) and two transferbeam lines. The UHV system of CSRm is the most representative subsystem in the project. Tominimize the beam loss due to charge exchange of the heavy ions with the residual gas molecules,the pressure of the CSRm vacuum system should reach 3.5 × 10-9 Pa (N2 equivalent) and thepressure of 8 × 10-10 Pa is expected for very heavy ion such as uranium to make its lifetime longerthan 50 s in the ring. Now, the vacuum system of CSRm has been completed and a pressure lessthan 5 × 10-10 Pa has been obtained. In this paper the layout of the CSRm vacuum system, thevacuum equipment in CSRm, the treatment method for the CSRm vacuum chambers, and theinstallation and operation of the system will be reported.