Operational performance of EAST cryogenic system and analysis of it's upgrading

Since the first commissioning in February 2005, EAST cryogenic system was cooled down and warmed up for seven physics experimental campaigns. The operational performance of the cryogenic system, and heat loads released on different operational modes, together with cryogenic behaviors on magnets are presented in this paper. All of the thirteen pairs of current leads (CLs) in EAST tokamak have been upgraded to high temperature superconductor (HTS) current leads, so the liquefaction requirement for the refrigerator was greatly reduced and operational mode is quite different from the original optimization mode. In addition, when the physics experiments progress steadily, the requirements of the refrigeration are becoming higher. Furthermore, some components need to be replaced, because of low efficiencies or low stability. So the cryogenic system needs to be analyzed for upgrading. This paper presents the preliminary analysis.