Field and Length Dependence of the Creep Rate in Proximity Effected Multifilamentary Strands
Magnetization creep rates have been measured in proximity effected multifilamentary superconductive strands. Measurements have been made as a function of field for both untwisted strands of various lengths (L), and longer strands for several twist pitches (Lp). The results are described using a model which includes dual field gradients and a semi-Bean approximation. Three regimes are found; (1) low fields where the creep rate is similar to NbTi, (2) intermediate fields, where the creep rate is high due to proximity effect (PE), and (3) high fields, where the NbTi creep rate is recovered. U0 values for proximity effected strands are found to be between 5.3 and 10 meV. PE creep in twisted 71.1 cm strands (even where Lp/L ≪ 1) in which static PE at lower fields is controlled by Lp, is strongly influenced by end effects.
KeywordsCreep Rate Proximity Effect Flux Creep Intermediate Field Magnetization Decay
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