CRYOSTAT

PROBLEM TO BE SOLVED: To solve the problem that, when liquid helium is additionally injected, impurities such as air or water are mixed into a liquid helium tub and the impurities are accumulated in a safety valve in the liquid helium tub during a long-term operation. SOLUTION: A first improved point is that the liquid helium is supplied to a superfluid helium tub 4 through a filter 21 so that a safety valve 22 is not exposed to the liquid helium containing impurities. Therefore, a cooler 13 for saturating and cooling the liquid helium 3 from a first tube 2 is brought into heat contact with a second tub 4, and a helium takeoff tube 18 is wound on a heat exchanger 20 coming into contact with the cooler 13 for cooling, so that the liquid helium of a superfluid state is stored in the second tub 4 through the filter 21. A second improved point is that a third tub 7 serving as a pressure release path is coupled to the second tub 4 through a low temperature safety valve 22. As the tub 7 prevents an invasion of impurities from the atmosphere by a check valve 24, impurities are prevented from staying in the safety valve 22. COPYRIGHT: (C)2007,JPO&INPIT