Stability analysis of composite superconductors by thermal analyzer digital computer program

A digital simulation of a copper-stabilized, pool-boiling superconductor driven normal by discrete energy inputs and subsequently recovering by cold-end conduction or unconditionally with current sharing was analyzed using a Cyber 70 computer. Thermal Analyzer Computer Program P4560B, developed by General Dynamics Convair Division, was used for this analysis. The simulation was designed to represent sections of typical 10,000-ampere conductors applicable to the Large Coil Program. The analytical power of this tool for examining stability in either the end-conduction or full recovery mode is characterized by the ability to accommodate all heat transfer rates, fluxes, and thermophysical properties as functions of temperature and/or time. Three-dimensional heat diffusion permits design analysis of heat flow attenuation in three orthogonal directions caused by fabrication and material peculiarities. Further, lateral gradients in large conductors caused by cross-sectionally local heat inputs (such as test heaters) and non-uniform net heating caused by variations in the laterally localized ratio of boiling heat transfer surface to cross-sectional area may be examined. Typical results in the form of temperature profiles along the length of the conductor show the dynamic development and evolution of the normal zone and normal front velocities during cold-end conduction recovery and, for unusual drying sequences, during propagation. For magnets with credible long normal zone development, the emphasis is toward unconditional/full recovery and its achievement is demonstrated analytically through the application of probable boiling heat fluxes for the conductor/channel configuration. Stability is analytically shown to be further enhanced using coating augmented boiling heat fluxes. Application of the detailed results to the mapping of stability margins throughout the conductor winding pack is summarized