IMPROVED HE-3-HE-4 REFRIGERATOR

The characteristics and performance of an improved He-3/He-4 double stage refrigerator are presented. It is based on the same principle as the previous double stage refrigerator described in reference 1. A new geometry was used to overcome both the extra thermal input due to gas convection in the condensation lines and the long period required to precool at 4.2 K. The improved refrigerator reaches an operative temperature of almost-equal-to 0.35 K without any external mechanical pumping. The refrigerator has been used to cool He-3 bolometers.