Characterization of High Purity Aluminum Material for Use as a Stabilizer of the 60 kA SMES Conductor

Abstract

High purity aluminum is used to stabilize the 60 kA SMES monolithic conductor. The stability margin of this conductor depends on the low temperature resistivity of the HPA1. Residual resistivity ratio (RRR) tests of annealed aluminum samples are used as an acceptance test from the material vendor. Starting with a HPA1 of a given RRR, the conductor manufacturing and assembly process further degrades the aluminum RRR. In this paper we outline the test program that has been used to characterize the HPA1 material for the SMES conductor along with the test results. Two standard RRR measurement techniques are used: the four point Potentiometric DC method and the eddy current decay (ECD) method. The conventional four point probe method is used on wires while the ECD is used for the 25.4 mm rods. RRR measurements of samples machined at different radii of the twisted grooved 25.4 mm rods show that the twisting effect on RRR is higher at the outer surface of the rod.