Results of preliminary tests of an external cryogenic system for the SPIN superconducting synchrotron

Results of testing elements of an extermal cryogenic system for the SPIN superconducting synchrotron are discussed. A cooling circuit of the refrigerator is considered providing the most effective performance of cooling. Experimental characteristics of the KGU-1600/4,5 cryogenic helium refrigerator are presented for simultaneous production of cold and liquid helium. The characteristics are taken for different combinations of the equipment: with a throttle and a steamliquid expansion engine, on two and three turboexpanders at the stage of preliminary cooling, with and without the use of liquid nitrogen. Heat fluxes to the cryogenic helium tubings with a total length of 160 m are determined. The possibility of using TsTG-0.5/0.7 liquid helium tank as a buffer capacity is considered. Allowable heat fluxes to the liquid helium in SPIN are estimated at which reliable refrigeration of the magnet can be achieved