The EAST superconducting tokamak, an advanced steady-state plasma physics experimental device, is now being built at Institute of Plasma Physics, Chinese Academy of Sciences (CASIPP). All of toroidal field (TF) magnets and poloidal field (PF) magnets made of NbTi/Cu CICC are cooled with forced flow supercritical helium at 3.8 K. The cryogenic system of EAST consists of a 2 kW/4 K helium refrigerator and a helium distribution system for the cooling of PF and TF coils, structures, thermal shields, buslines and the current leads. The assembling and the installation of the 2 kW/4 K refrigerator were finished at the end of 2004 and the refrigerator has been commissioned successfully in July, 2005. The installation of the cryogenic distribution system will be finished at the end of 2005. This paper presents the design of the cryogenic system, the present states of the construction and the test results of the helium refrigerator.
