Cryogenic systems for large research projects

Cryogenic Refrigerators and the distribution system of the refrigerant belong to the key support technologies for large research projects, which rely on superconducting magnets or cavities. Present day refrigerator technology has reached a high degree of reliability due to the use of all rotating machinery. For refrigeration temperatures below 4.5 K cold compressors can be helpful. A diagram is presented for the selection of the appropriate technology for such a machine. Large refrigerators have Carnot-efficiencies in the order of 30%, mainly due to using many stages of work extracting expansion of the refrigerant.