Status: large-scale subatmospheric cryogenic systems

The state of the art of large-scale refrigeration in the temperature range under 4 K is reviewed. In the late 1960s and early 1970s an interest in testing and operating RF cavities at 1.8 K motivated the development and construction of four large (300 W) 1.8 K refrigeration systems. In the past decade, development of successful superconducting RF cavities and interest in obtaining higher magnetic fields with the improved niobium-titanium superconductors has once again created interest in large-scale 1.8 K refrigeration systems. The L´Air Liquide plant for Tore Supra is a recently commissioned 300 W, 1.8 K system which incorporates new technology (cold compressors) to obtain the low vapor pressure for low-temperature cooling, CEBAF (Continuous Electron Beam Acceleration Facility) proposes to use cold compressors to obtain 5 W at 2.0 K. Magnetic refrigerators of 10 W capacity or higher at 1.8 K are now being developed