Extracted Strand IC and Strand IC Degradation for SSC Cables

The performance testing of the large quantities of superconducting cables for SSC magnets is a daunting challenge, at best. In an effort to reduce the quantity of full cable testing required, an investigation is underway to evaluate the utility of determining the performance of the SSC cables using extracted strand testing. It is believed that the cable performance can be quite accurately determined by measuring the critical current (Ic) on strand samples removed, at random, from the manufactured cable.1 These strand measurements are used to derive the cable critical current. The measured critical current (Ice) are then compared to the virgin strands (Icv) input into the cable to determine the degradation resulting from the cable fabrication. The advantage of this type of certification is two fold; firstly the manufacturer can certify the performance using existing strand measurement equipment. This allows for a reduction in the lead time between manufacture and delivery of the cable. Secondly, the SSC can perform random sampling, as opposed to 100% cable testing and still maintain adequate visibility into the performance of the cables. The following sections cover the techniques used and the results obtained for measurements of extracted strand Ic (Ice) and field dependence of ICe for rnore than fifty representative cables. The data for another five cables for which full cable Ic values were previously measured at Brookhaven National Laboratory are also presented and compared with full cable Ic results. The details of the full cable measurements performed at BNL are described elsewhere2. The SSCL full cable test facility will soon be in routine operation which will allow for precise verification of the validity of extracted strand testing in the determination of Ic in SSC cables.