YBACUO CURRENT LEAD FOR LIQUID-HELIUM TEMPERATURE APPLICATIONS

An electric current is supplied to superconducting devices by means of current carrying leads between the room temperature power source and the superconducting device. Up to now, such current leads have been made of copper conductors in rod or pipe form. For an optimized copper current lead between 300 K and 4.2 K, losses at room temperature are about 3 kW per kA. Use of superconducting ceramic between 77 K and 4.2 K would decrease the heat conduction and eliminate ohmic losses. Consequently, we studied the losses of a double current lead (copper from 300 K to 77 K and YBaCuO from 77 K to 4.2 K). In this paper we give the main results obtained: [GRAPHICS] on the electrical contact resistance between YBaCuO and metal on the transport critical current density and 50 Hz losses of sintered tubes and textured material on a 1 kA double DC current lead. On the basis of these results, it seems possible to decrease the current lead losses by a factor of five.