The characterization of superconducting materials - conflicts and correlations

A superconducting material can be said to be characterized when sufficient of its properties have been measured for its response to be predicted under any conceivable experimental constraints. The experimental constraints constitute a moving target. The problems and pitfalls in making superconducting measurements on inhomogeneous superconducting materials are reviewed by reference to recent work on A15 and Nb-Ti conductors. The breadth of information available in comparative studies of inductive transitions and various types of resistive transition is assessed. The problem of the critical current criterion and its relation to a time dependent voltage-current characteristic is discussed as is the measurement and definition of the upper critical field in inhomogeneous superconductors