Design and optimization of a helium refrigerator for testing large superconducting magnets

Superconducting dipole magnets for the Superconducting Super Collider (SSC) must be tested under cryogenic conditions at their production sites during all stages of development and production. Each production phase has its specific needs for magnet cold testing with regard to thermal cycles, power cycles, and quenching. When multiple cryogenic test stands are supported by one helium refrigerator, the system design is complicated by the possibility of magnet operations in the test stands being in any combination of cleanup, cooldown, cold test, quench, quench recovery, and warm-tip. This paper describes the integrated helium refrigeration and circulation system at General Dynamics' SSC collider dipole magnet production facility at Hammond, LA, which was originally designed to support two magnet test stands and later expanded to four. It also discusses modeling of the magnet test program to develop the required system capacity and optimization of the cycle and hardware configuration to minimize life cycle cost. The optimization includes integrating the cleanup and cooldown functions into the refrigerator