Volume pinning force and upper critical field of irradiated Nb3Sn

Irradiation by neutrons and ions in A15 superconductors (Nb3Sn, V3Ga) exerts a stronger influence on the pinning behavior than in nonordered alloys (NbTi). In this work it is shown for deuteron irradiated Nb3/Sn wires prepared by the bronze process that the dose curve of the volume pinning force P/sub V/ can be conveniently described by a sum of two terms, due to the grain boundary pinning and to the radiation pinning, respectively. After deduction of the contribution by the radiation-induced pinning centers, good agreement is obtained between the measured P/sub V/ values and those calculated using the upper critical field B/sub c/2 and the transition temperature T/sub c/ on the basis of the irradiation fluence. The use of a theoretical relationship between B/sub c/2 and T/sub c/ is supported by measured values. Application to multifilamentary superconductors with high current carrying capabilities simplifies the calculation of P/sub V/, since the radiation induced volume pinning force can be neglected