Effects of Tensile and Compressive Strain on Critical Currents of$rm Nb_3rm Al$Strand and Cable-in-Conduit Conductor

Effects of tensile and compressive strain on critical currents$(I_c)$of$ Nb_3 Al$strand and cable-in-conduit (CIC) conductor were investigated using a newly developed apparatus. The$ Nb_3 Al$strand manufactured by jelly roll process was 0.74mm in diameter with a copper/noncopper ratio of 4.05. The CIC conductor sample which consists of two$ Nb_3 Al$strands and one copper wire inserted into a stainless steel conduit was prepared. The effective strain and magnetic field ranges for the CIC conductor sample were from$-$0.91% to$+$0.26% and from 6 T to 11T, respectively. It is clearly shown that the$I_c$decrease of the CIC conductor sample by longitudinal strain is relieved considerably compared with the strand sample, indicating the relaxation of intrinsic strain in$ Nb_3 Al$filaments in CIC conductor due to the cabling effect. The relaxation effect is about$+$0.1% for$-$0.8% in effective strain of CIC conductor.