A new type of liquid- 3He target system using small mechanical refrigerators

Abstract

A new type of liquid- 3He target has been developed for photoabsorption experiments at intermediate energies. Using the cooling power of liquid 4He at reduced vapour pressure, 3He gas is liquefied into a cylindrical target cell of 180 ml and is maintained at 2.0 K during the experiment. Evaporated 4He gas is evacuated by a rotary pump and returned into the 4He bath in the cryostat, where two small mechanical refrigerators with cooling capacities of 3 W at 4.3 K and 10 W at 20 K are operated for the purpose of 4He recondensation. A maintenance-free operation of more than 1000 hours has become possible by adopting the 4He circulation system.