Coupling of (Ti–Nb) Filaments in a Superconducting Multifilament Composite Conductor

Abstract

Magnetization measurements were performed on variously prepared samples of multifilament (Ti–Nb) and Cu composites. All measurements were performed at 4.2°K, utilizing peak magnetic fields of 50 kG. The magnetization data were obtained in a manner similar to that described in earlier papers. The impetus for these particular measurements was the hypothesis of P. F. Smith in regard to the coupling of the small filaments of superconductors when they are embedded in a low‐resistivity matrix such as Cu. This coupling, of course, is a function of ∂Ha/∂t, but for very long lengths (e.g., magnets), or even short lengths in the case of well annealed Cu, the time constant for the decoupling is extremely long. The coupling, it was suggested by Smith, could be reduced by increasing the resistance of the matrix material, and then twisting the composite, the equivalent of ``transposition'' of the individual filaments in a two‐dimensional case. Various resistance layers are formed around each strand by the proper heat treatment of these multifilament composites. The filaments of the sample composites were found to be decoupled to varying degrees depending on applied magnetic field, sample length, and matrix resistivity.