Inputs generation for COLISEUM coupling losses model using X-ray tomography: analytic and experimental approaches

Abstract

Tokamaks coils are wound with long lengths of cables including hundreds of superconducting and copper strands twisted together into multiple stages. They refer to Cable In Conduit Conductors (CICC). Coupling losses induced by magnetic field variations dissipate power in the coils during machine operation. For several years, the CEA has been developing the analytical model COLISEUM (COupling Losses analytIcal Staged cablEs Unified Model) aiming at predicting coupling losses at various conductor scales. Geometrical (cabling radii, twist pitches) and electrical (inter-strand and inter-bundle conductances) parameters of each stage constitute the model inputs. In this article, we first present the raw 3D tomographic image treatment method that will serve to generate COLISEUM inputs with high level of reliability. We then define and extract several relevant effective geometric cable parameters from images data. These inputs are used along with the COLISEUM model to improve coupling losses prediction. A systematic study of six JT-60SA TF type samples has been realized and a geometric parameters database is constructed. The COLISEUM model is used in a 2-stage configuration with the two highest stages of the cable. First results are presented and discussed.Index Terms— Superconducting magnets, CICC, X-ray tomography, geometric parameters measurement, AC losses, modelling.