Flux flow in high-temperature type II superconductors governed by the activation of Frank-Read sources and the resultant motion of core dislocations

Abstract

The functional form of the volume pinning force Fp for high-temperature type II superconductors is derived as the degree of distortion in the flux-line lattice changes. A single mechanism operates in both NbTi and Nb3Sn, namely the activation of Frank-Read sources where Fp=(1/100)( mu 0H2c2/DK2)b(1-b/0.95) for 0.3<or=b<or=0.9 and Fp=(1/21)( mu 0H2c2/DK2)b12/(1-b)2 for 0.1<or=b<or=0.9 respectively. Above the critical state, flux flow is first characterised by the motion of core dislocations.