Measurements of stability of cabled superconductors cooled by flowing supercritical helium

The concept of stability in superconductors cooled by forced flow of supercritical helium is somewhat different from conductors cooled by pool-boiling helium. The crucial point is whether such a conductor can recover from a large deposition of energy before the cryogen is heated to a level that prohibits recovery. In an investigation of stability of forced flow conductors it is usually necessary to use indirect methods of heating the conductor initially, such as by an external pulse coil. However, in using such indirect methods it is essential to determine accurately the time development and magnitude of energy deposition. We use ac loss techniques to examine pulse coil heating and compare those results with extensive measurements on a specially constructed sample containing an embedded heater.