Critical Surfaces for Commercial Nb₃Sn Ribbon and Nb-25%Zr Wire

Abstract

Superconductors with properties that make their application to magnet construction attractive are now a commercial reality, The problems of stability and predictability that plagued the superconducting magnet designer now appear to be solvable [^1,2]. Magnets of certain types and sizes can now be designed with a high degree of confidence that the finished product will perform as predicted from the tabulated characteristics of the superconductor. The magnet design problem is usually stated in terms of the magnetic field intensity and geometry, cost, operating temperatures, and for some special applications (e.g., the space program), weight. The three prime variables which define the usefulness of a superconductor are temperature T, magnetic field H, and current I. A surface in this space HIT defines the boundary between resistive and nonresistive (superconducting) behavior. The optimum solution to the magnet system design problem will lie on this surface for a material chosen with regard to the other variables of cost, strength, weight, etc.