Stability tests of the Nb-Ti cable-in-conduit superconductor with bare strands for demonstration of the Large Helical Device poloidal field coils

摘要

Stability and quench experiments of a Nb-Ti cable-in-conduit superconductor with bare strands have been carried out to determine the performance of the poloidal coil for the Large Helical Device (LHD). The conductor was formed into a double-pancake coil named IV-S and was mounted on TOKI-PF-a previously tested R&D coil. In excitation tests at 7.4-8.3 K, the IV-S coil reached the critical currents without premature quenches. Stability tests at 7.5 K indicated that the limiting current exceeds 20 kA, which is the nominal operating current of the LHD poloidal coils. These results demonstrated that the stability of the chosen conductor with bare strands is high enough for the LHD.