Design and Commissioning of a 700 W@3 K Sub-cooled Helium Test Facility

Abstract

Abstract In order to increase the magnetic field and temperature margin of superconducting magnets, a test facility for a 700 W@3 K sub-cooled helium refrigerator was proposed to decrease the operation temperature from 4.5 K down to 3 K. The process flow of the 3 K sub-cooled helium test facility has been designed with two cold compressors arranged in series to pump the vapour pressure from 120 kPa to 24 kPa. This 3 K sub-cooled unit has been constructed and operated successfully to decompress the 4.5 K saturated helium to 3 K sub-cooled helium. The preliminary commissioning results indicated that this 3K sub-cooled helium unit could achieve more than 700 W capacity at 3 K sub-cooled helium. Thermodynamic parameters and performances of this 3 K sub-cooled helium unit were introduced and compared with the designed values in good agreement. The rotation speeds, pressures and temperatures of cold compressors during the transient state and the steady state were also analysed.