Evaluation of a NbTi cable-in-conduit prototype superconductor for the Wendelstein 7-X magnet system

Swissmetal recently completed a contract to manufacture 200 m of NbTi cable-in-conduit prototype conductors to be used in the Wendelstein 7-X superconducting magnet system. The conductor consists of a 192 strand, four stage NbTi cable in an aluminium alloy jacket cooled by forced flow helium. It will operate at 16 kA, 3.8 K and 6.2 T. To qualify this conductor electrical tests were performed on a 3.6 m long full-size specimen in the SULTAN test facility at CRPP. In preparation for these tests two conductor terminations and one electrical joint were manufactured in a relatively simple and, therefore, time and cost saving way. This paper presents the test results of critical current measurements performed on the conductor as well as of extracted strands in background fields of up to 8 T. The joint is described and its resistance is reported. In addition the results of pressure drop measurements at room temperature are presented