Development of High-Current Vapor-Cooled Current Leads for Fusion Devices

Abstract

Japan Atomic Energy Research Institute (JAERl) has been developing a high-current vapor-cooled current lead with a nominal current more than 30 kA for used with the superconducting coil of the Fusion Experimental Reactor. As a development step, we have fabricated a number of current leads with a cable-in-conduit geometry and have tested them up to 20 kA. The measured heat leak at 4 K is about 1.0 W with helium flow rate of 0.05 g/s-kA, which is exactly the same as for the ideal self-cooling condition. In addition, stable operation at the nominal current is possible for more than 10 min with no helium flow. The measured thermal performances are in sufficiently good agreement with those calculated that we concluded that the heat exchange coefficient in current leads is very close to the theoretical value. This paper describes the development status and the test results obtained at operating currents up to 20 kA together with the comparison between the measured and calculated characteristics.