Ultra high vacuum system of Lanzhou heavy ion cooler-storage ring

UHV obtaining technology has been successfully developed to achieve an ultra high base pressure of 6 × 10 Pa for Lanzhou heavy ion cooler-storage ring project (HIRFL-CSR). Discussion focuses on technological details, including selection of pumps, related instruments and materials for the ultra high vacuum system and effective reduction of out-gassing rate by degassing in a vacuum furnace and by in-site vacuum baking-out. Since the base pressure of the lab-built prototype vacuum chamber has already achieved 5 × 10-10 Pa, the well-tested pumping technology should work well in large ultra-high vacuum system of HIEFL-CSR. So far, the base pressure of the lab-built subsystems has successfully been pumped to 2 × 10-9-4 × 10-10 Pa.