Operation of the Tevatron Satellite Refrigerators for 0.75- and 2.0-Kilometer-Long Magnet Strings

Abstract

The Tevatron magnets at Fermilab are cooled by a hybrid system which consists of a 5000 liters/hr central helium liquefier coupled with a small-diameter liquid transfer line connecting twenty-four satellite refrigerators. The transfer line supplies liquid helium for both the refrigerators and the magnet lead flow as well as liquid nitrogen for the magnet shields. The satellites act as amplifiers with a gain of twelve by using the enthalpy of the helium supplied by the central liquefier as liquid and converting it to 4.5-K refrigeration and then returning it as 300-K gas. This arrangement combines the advantages of a single central facility with those of individual stand-alone units stationed around the ring. The central liquefier has the high efficiency associated with large components but its requirements for distribution of both cryogenic liquids and electric power to the service buildings is reduced. The six compressor buildings supply 20 atm helium to the twenty-four refrigerators through a discharge header located on the berm and a suction header located in the tunnel. The compressor buildings each have four-two stage 58 g/sec screw compressors; each of these has its own oil removal system. The inventory in the ring is controlled at the first compressormore » building through a cross-connect line to the central liquefier. The suction header is also used as the cooldown line as well as for quench relief. A third header located in the tunnel is the nitrogen collection and relief header.« less