Superconducting model coil for the stellarator W 7-X under test

Tests were performed on a solenoidal model coil made of one full size unit length of the superconducting cable being developed for the stellarator Wendelstein 7-X. The conductor is of cable-in-conduit type with the cable embedded in an aluminium alloy jacket. The behaviour of the coil had been investigated in the STAR test facility at FZK under various conditions. The results were promising. The quench currents were highly reproducible and no training occurred. The observed difference between the measured quench current values and those expected from single strand critical currents can be assigned to the thermal treatment performed during cable fabrication and has to be taken into account in future cable design.