Socool: A 300 K-0.3 K pulse tube/sorption cooler

CEA/SBT has acquired substantial experience in the fields of Pulse Tube (PTC) and Sorption coolers. Double stage PTC capable of lifting about 0.5 W of cooling power at 4 K have been successfully experimented in the past years. Single stage 3He and 4He sorption coolers have been developed for both ground and space applications. A precooling temperature below 2.5 K is required to operate a 3He sorption cooler efficiently. This is commonly achieved with a pumped liquid 4He bath. However for some applications (for example bolometers cooling in astrophysics) the vibrations induced by the pumping system are problematic. In addition the fraction of liquid lost during the bath pumped down significantly affects the bath hold time. To overcome this difficulty, a double stage (4He/3He) sorption cooler has been developed which can be operated either from an atmospheric 4He bath or from a 4 K PTC, and which provides temperature down to 260 mK. The first experimental results obtained with this cooler and a 4 K PTC deve...