Abstract
High-field characteristics of several kinds of superconducting wires were studied by a pulsed magnet. An electrical energy of 28.3 kJ, stored in a capacitor bank, was transferred to the liquid nitrogen cooled magnet. The i.d. of the magnet was 30 mm and the maximum field produced was 220 kOe with a rise time of 16 msec. The noise due to the induced voltage was canceled by a compensation coil. The transition sensitivity of the measuring system was 0.1 mV.Resistive critical fields Hr measured by the pulsed magnet with rise times longer than 10 msec were quite consistent with those measured by a steady field magnet. Critical currents Jc of Nb-Zr alloy wires were much decreased by the pulsed fields, whereas in compounds wires, e.g. V3Ga and Nb3Sn, the decreases of Jc were small. Resistivity changes in flux flow states and the peak effect phenomena could also be observed by the pulsed field measurement. The Hr of Nb-Zr alloy wires were increased by the decomposition reaction at 785°C and decreased by the eutectoid reaction at 560°C. V3Ga wires made by a new solid state diffusion process at 600°∼700°C showed higher Jc than those of Nb3Sn above 120 kOe. Hr of V3Ga wires seemed to be around 220 kOe at 4.2°K.
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