Thermal tests of 6 KA HTS current leads for the Tevatron

Prototype current leads incorporating High Temperature Superconductor (HTS) elements have been tested at Fermilab. Fermilab's Tevatron includes about 50 pair of 5 to 6 kA current leads, and Fermilab is investigating the feasibility of replacing some of these conventional leads with HTS leads. The prototype HTS current leads are cooled primarily by a countercurrent flow of liquid nitrogen from the 80 K intercept to the warm end of the leads, but also a small flow of helium gas cools the HTS section from the 4 K level. The HTS current leads carried the design current of 5 kA with good thermal and electrical stability. LN2 flow without current was 0.24 g/set per lead and with 5 kA was 0.53 g/set per lead, corresponding to heat inflows to the 80 K intercept of 46 Watts and 101 Watts, respectively. The heat input to the 4 K level was 0.6 W with no current and 0.7 W +/- 0.1 W per lead with 5 kA current, about 1/8 of the heat load via copper, vapor-cooled leads