Electromagnetic and mechanical characterisation of ITER CS-MC conductors affected by transverse cyclic loading. I. Coupling current loss

Abstract

The magnetic field generated by a coil acts on the cable which results in a transverse force on the strands. This affects the interstrand contact resistances (R/sub c/), the coupling current loss and current redistribution during field changes. A special cryogenic press has been built to study the mechanical and electrical properties of full-size ITER conductor samples under transverse, mechanical loading. The cryogenic press can transmit a variable (cyclic) force up to 650 kN/m to a conductor section of 400 mm length at 4.2 K. The jacket is partly opened in order to transmit the force directly onto the cable. In addition a superconducting dipole coil provides the magnetic field required to perform magnetisation measurements using pick-up coils. The various R/sub c/'s between strands selected from different positions inside the cable have been studied. The coupling loss time constants (n/spl tau/) during and after loading are verified for the Nb/sub 3/Sn, 45 kA, 10 and 13 T, ITER Model Coil conductors. A summary of the results obtained with up to several tens of full loading cycles is presented. A significant decrease of the cable n/spl tau/ after several cycles is observed. The values of the n/spl tau/'s are discussed with respect to the R/sub c/ measurements and a multiple time constant model (MTC).