Patent ID: 8375742
Filing Date: 2013-02-19
Classification: F17C,F25B,F25D

Abstract:
1. A method of recondensing boiled-off cryogen from a cryostat from a gaseous state to a liquid state using a multi-stage cryocooler cold head comprising a hot end and a cold end, at least two cooling stations at the cold end, and a condenser thermally coupled to a lowest stage cooling station at the cold end; a vacuum insulated sleeve with an upper end and a liquid end, surrounding the cold end of the cold head of the cryocooler, the at least one cooling station and the condenser; and a gas trapping tube between the upper end of the sleeve and a gas outlet of the cryostat; a liquid transfer tube with a first end connected to the liquid end of the vacuum insulated sleeve and a second end in fluid communication with the cryostat, a heat transfer ring surrounding the vacuum insulated sleeve adjacent to a cooling station; and a radiation shield connected to the heat transfer ring and surrounding at least a lower portion of the vacuum insulated sleeve and the liquid transfer tube; the method comprising the steps of: collecting boiled-off cryogen in gaseous state from the cryostat; conducting the cryogen through the gas trapping tube from the cryostat to the upper end of the sleeve; precooling the cryogen by passage around the cryocooler cold head; recondensing the cryogen into a fluid state on the condenser; and passing the recondensed cryogen in fluid state from the condenser within the insulated sleeve through the liquid transfer tube back into the cryostat.