225. JT-60粒子入射加熱装置(NBI)用大容量クライオポンプシステムの性能試験

A large capacity cryopump system for JT-60 NBI has been developed and tested. The results obtained are as follows:(1) The pumping speed of a cryopump for hydrogen gas was estimated to be 1, 380m3/s, so that the total pumping speed by 14 cryopumps was about 20, 000m3/s; the largest pumping system in the world was thus achieved.(2) The refrigeration capacity of a helium refrigerator was 3, 020W, which is the largest capacity of a helium refrigerator in Japan.(3) Cool-down of a helium refrigerator and 14 cryopumps was completed in 16h without a thermal imbalance among the cryopumps due to a newly developed computer control.(4) In the rated neutral hydrogen beam injection of power 20MW at beam energy 75keV, pumping characteristics of each cryopump was kept stably and the average reionization loss in the drift tube was 4.6%, satisfying the specified reionization loss 5%.