Transverse and longitudinal critical current densities in Nb46.5wt%Ti multifilamentary wire from 2K up to Tc in magnetic fields up to 15 Tesla

The critical current density of a Nb46.5wt%Ti multifilamentary commercial wire has been measured from 2K up to Tc in magnetic fields up to 15 Tesla. Measurements have been made for both the transverse and longitudinal orientation of the current with respect to the applied field. We have found that the structure of the E-J characteristic is strongly affected by the orientation of the applied field with respect to the macroscopic current. In addition we have explicitly measured the temperature dependent effective upper critical field, B*c2(T), in each orientation and found it to be higher for the longitudinal orientation. The pinning force is described by the same functional form in both configurations such that the orientation dependence of Jc is primarily determined by B*c2(T) and not by the magnitude of the macroscopic Lorentz force operating. (orig.)