A Cryogenic Test Stand for Full Length SSC Magnets with Superfluid Capability

Abstract

The Fermilab Magnet Test Facility performs testing of full scale SSC magnets on test stands capable of simulating the cryogenic environment of the SSC main ring. One of these test stands, Stand 5, also has the ability to operate the magnet under test at temperatures from 1.8 K to 4.5 K with either supercritical helium or subcooled liquid, providing at least 25 W of refrigeration. At least 50 g/s flow is available from 2.3 K to 4.5 K, whereas superfluid operation occurs with zero flow. Among the special components designed to permit this variety of operating modes are heat exchangers for both forced flow of normal fluid and stagnant superfluid and special check valves which provide a thermal barrier at each large-diameter penetration to the superfluid space. Other unique features include 10000 A current leads mounted in a separate, removable can for easy lead replacement if necessary, and the room-temperature vacuum pumping system with a 2.5 g/s capacity at 12 Torr. Cooldown time from 4.5 K to 2.0 K is 1.5 hours. Instrumentation to monitor and control the cryogenic conditions is provided.