STRAIN DEPENDENCE OF CRITICAL CURRENTS IN COMMERCIAL HIGH-TEMPERATURESUPERCONDUCTORS

We describe two versions of a simple device that enable the J(c) (B,T, epsilon) characterisation of a < 40 mm diameter single loop of HTS tap e. The loop is mounted on a cylinder that is slit longitudinally at re gular intervals around its circumference. Strain is applied by forcing a conical plug into the tapered bore of the cylinder which expands ev enly as a consequence. The strain is measured by a strain gauge glued to the surface of the tape. The advantage of this configuration is tha t it enables insertion in the small bores of the highest field superco nducting magnets and thus permits access to fields levels not easily a vailable in more traditional linear pulling devices. Also the loop con figuration is more representative of the coil geometry encountered in magnet applications. Representative data are presented and discussed c ritically.