Calculations for breakdown induced by "Large defects" in superconducting niobium cavities

A computer program has been written to model thermal magnetic breakdown. It incorporates all the heat production and heat transport factors. The temperature of the defect and vicinity is calculated for increasing rf field levels until the defect grows unstably, determining the breakdown field level. Calculations are performed for a variety of circumstances to explore the relative influence of the various heat production and heat transport factors.