Evaluation of the temperature and magnetic field dependence of critical current densities of multifilamentary superconducting composites

Crucial to the development of new superconducting materials is a quantitative determination of critical current density (J
c
). It is widely known that the choice of definition of J
c
can affect the absolute values determined and this paper will begin, therefore, with brief reference to this problem coupled with experimental considerations and relate these to the selection of the "short sample" configuration most suited to the investigation of the resistive transition. This will then provide the background for the description of a new facility which permits the evaluation of critical current densities at short sample currents up to 500 A and magnetic fields up to 16T. The temperature dependence of J
c
in a magnetic field plays a major role in determining the operating parameters and stability of any superconductive magnet system. Thus a further feature of the facility is the ability to measure short sample currents in an applied magnetic field over a range of temperature from below 4.2 K up to the critical temperature, (T
c
), for T
c
< 30K. Details will be given of the construction and performance of the variable temperature, high-current probe. Results will be given for J
C
(B,T) for selected commercially available mnltifilamentary materials.