Abstract
An Nb3Al conductor with stainless steel (SS) conduit has been developed in the framework of ITER Engineering Design Activity. The critical current performance of this conductor was experimentally investigated by using a short conductor sample. The results show that the critical current achieves the expected, resulting in demonstrating the validity of the fabrication method. The thermal strain is generally applied to the strands if SS conduit is used because of the different thermal expansion between the strands and SS conduit. However, it was not applied in our sample, since the conductor length, a few meters, is too short to keep it by friction force between the cable and conduit. The thermal strain applied to the strands in a long conductor is therefore estimated by using the solid model, in which the strain on the strands and conduit are calculated from the equilibrium of their thermal forces, ignoring the effect of cabling on relaxation of the strain on the strands. The results indicate that the Nb3Al strands are subjected to a compressive thermal strain of less than 0.4%. The critical current degradation by this is less than 10%, even though the SS conduit is used. Consequently, its critical current is estimated to be 90kA, which is sufficiently high compared with the nominal, 46kA, at 13T and 4.5K. Furthermore, it should be noted that the large thermal force, 80kN, appears after the heat treatment at room temperature.
