The effect of titanium content on the pinning force in Nb44wt.%Ti to Nb62wt.%Ti

The authors have been studying high Ti alloys to establish whether they offer higher low-field J/sub c/ values than Nb46.5wt.%Ti and find that they do, with values, as high as 7500 A/mm/sup 2/ at 2 T, 4.2K. They have established that the pinning centers are alpha -Ti precipitates for all alloys from Nb44wt.%Ti to Nb62wt.%Ti, but find a steady shift in the pinning curve peak to lower reduced fields at 4.2 K. Recently, it was shown that both Delta H/sub c/ and Delta kappa pinning can be recognized in Nb47wt.%Ti. Since T/sub c/ and H/sub c/ vary rapidly in the high Ti alloys, Delta H/sub c/ pinning should be proportionately stronger in the high Ti alloys, leading to a displacement of the peak in the pinning force curves to lower fields. The authors present pinning force data at 1.8 K and 4.2 K across the alloy range and find that while lower Ti alloys do exhibit b(1-b) behavior, the higher Ti alloys never realize b/sup 1/2/(1-b)/sup 2/ behavior.<
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