LAYOUT AND TESTING OF A MINIATURE THERMOSIPHON USING SPLIT-STIRLING CRYOCOOLER AS CRYOGENIC UNIT

Cooling systems for HTSC-SQUIDs must have sufficient low mechanical di sturbances and noise. Therefore a miniature thermosiphon was developed with nitrogen as cooling gas. It consists of an expansion tank, a con denser, coupled to the cryocooler, capillary tubes and an evaporator, where the SQUID will be placed. Nitrogen pressure, size of expansion t ank, temperature set point at the condenser, diameter of the capillary tubes have to be optimized. The siphon was built and tested. The foll owing results were found: The heat load at the evaporator is limited t o 0.3 W at the lowest working temperature of 65 K, when nitrogen press ure is 0.4 MPa. The volume of the tank is 200 mi and the capillary tub es are about 1.2 mm. This work is supported by BMBF within 13 N 62975.