The heat load of an 80 K liner for the SSC

The Superconducting Super Collider (SSC) will be the first proton machine in which synchrotron radiation significantly affects the cryogenic system and the beam tube vacuum. Synchrotron radiation represents the single largest heat load on the 4 K single-phase helium. It also provides a mechanism by which hydrogen can be desorbed from the beam tube wall, gradually worsening the vacuum. Insertion of a perforated and heated liner into the cold beam tube, together with a strip of cryosorber, effectively creates a distributed cryopump. Such an arrangement is an attractive solution to possible vacuum problems, provided it does not increase the heat load on the single-phase helium. In this paper, the primary mechanisms of heat transfer from an 80 K liner are considered, and the results of measurements on heat conduction through prototypical mechanical supports are presented