INFLUENCE OF STRUCTURE OF FINE FILAMENT NbTi COMPOSITE ON ITS ELECTROMAGNETIC CHARACTERISTICS

The study of the influence of filament diameter d(f), filament spacing d(n) and of B on critical current density J(c) and AC losses p(s) in one type of fine filament composite (FFC) has revealed 2 components of J(c), bulk and surface critical current density J(cb) and J(cs), respectively. A simple relation between them, J(c) and geometrical parameters of FFC including those with different types of artificial pinning centers (APC) is formulated. It is used to explain measured J(c)(B, d(f)) dependence in FFC with island type APC as well as to discuss the prospects of both types of APC in FFC for AC use. To verify the obtained theoretical results another series of FFC samples with sheet type APC has been prepared and measured. Experimental values of J(c)(B, d(f)) obtained in this series samples are smaller than expected. One possible reason for this difference is suggested.