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Degassing a large LHe cryopump

Conference ·
OSTI ID:5345581
A method has been developed and successfully tested to degas a large LHe cryopump. Use of this method inhibits the normally excessive pressure rise during the degassing cycle when the degassing rate exceeds the external pumping capabilities of the system. A small appendage pump, installed close to the main cryopump, absorbs all the gas, as it is desorbed from the main cryopump, with no rise in the system pressure. The appendage pump can then be isolated from the main vacuum system and degassed at high pressure. We pumped 15 to 20 x 10/sup 3/ Torr . 1 of H/sub 2/ on a 1.25 m/sup 2/ panel. During the degassing cycle the system pressure never rose above 1 x 10/sup -4/ Torr. In large vacuum systems for future fusion machines that contain cryopump panels as well as cryogenic magnets, this method is a unique and very useful tool. It will allow the degassing of cryopumps without affecting the temperature equilibrium of cryogenic magnets.
Research Organization:
California Univ., Livermore (USA). Lawrence Livermore Lab.
DOE Contract Number:
W-7405-ENG-48
OSTI ID:
5345581
Report Number(s):
UCRL-79674; CONF-771029-48
Country of Publication:
United States
Language:
English