Cryocooler-Cooled High<tex>$rm T_rm c$</tex>Superconducting Magnet Excited by a Hybrid Semiconductor-HTS Thermoelectric Element

Abstract

This paper describes progress in a cryocooler-cooled HTS magnet excited by a thermo-electromotive force of a thermoelectric element. Since this system requires no external power sources, there are advantages in compactness and weight over conventional HTS magnet systems. Thus, it is suitable for applications in places where constraints on space and weight are severe. For improvement of this magnet system, we present a concept of the new thermoelectric element which consists of a thermoelectric semiconductor and a superconductor. This hybrid element passively utilizes a superconductor as a thermoelectric material and decreases the cryogenic heat leakage per unit current (Q/I) ideally by half. In this paper, experiments of an HTS coil excitation with a hybrid semiconductor-HTS thermoelectric element are reported. It is shown that there are some obvious merits in using the hybrid element as a substitute for a normal p- and n-type semiconductor element.