Influence of cable layout on the performance of ITER-type Nb3Sn conductors

Abstract

In 2005-2006, the European Union tested in the SULTAN facility (CRPP Villigen, Switzerland) four ITER-type conductors assembled in two samples. Each conductor made use of an advanced Nb3Sn strand specially developed by European companies for the ITER Toroidal Field (TF) coil conductor. The cable layout of these conductors was the one of the ITER TF Model Coil conductor. In 2007, the European Union tested in SULTAN four other conductors within two other samples as prototypes of the updated ITER TF conductor. These conductors differed mainly from the former by their cable layout whereas identical or similar Nb3Sn strands were used. The paper reports on the current sharing temperature measurements of the second samples under ITER relevant operating conditions. The effect of cycling (1000 cycles) in current under full magnetic field was also investigated. The analysis of the test results is performed with respect to the strand properties using the usual smeared models of the cable. These test results were found to be significantly better than those obtained on the first conductors. The paper discusses the possible causes as well as the consequences of such a performance scattering.