Abstract
Recently, much developing work on large superconducting magnet for MHD power generation has been in progress, in which the arrival of liquid helium cooling system capable of stable and low-cost operation is one of the essential matter. For this, we have developed a closed cycle cooling system for 45kG saddle shaped magnet of 12 tons. The system is composed of 28l/hr helium liquefier, liquid helium storage, 20°K helium refrigerator with cooling capacity of 400 watt at 20°K, helium recovery system with 80Nm3/hr at 130 atm and instrumentation, which has following basic functions; to precooling the magnet to less than 20°K, to liquefy helium continuously and supply liquid helium, and to recover and reprocess any evaporated helium gas from the cryostat.
