THEORY OF THERMAL HYDRAULIC QUENCHBACK IN CABLE-IN-CONDUIT SUPERCONDUCTORS

In a numerical simulation of the motion induced by local heating of the helium in a cable-inconduit superconductor Luongo et al. discovered a new phenomenon they called thermal hydraulic quenchback. After the creation of a local normal zone, its expansion compresses and displaces adjacent cold helium. This compression and displacement heat the cold helium and case long segments of the conductor rapidly to become normal. The propagation velocity thus appears to increase rather suddenly. The present paper describes an analytical study of this phenomenon. The main result is a simple formula for the time at which thermal hydraulic quenchback first starts.