Thermal-hydraulic analysis of the CORCⓇ conductor for the DEMO CS coil

Abstract

Conductors using High Temperature Superconductor (HTS) tapes are considered as a very promising solution for future high-field fusion magnets. Various HTS cable concepts, such as e.g. twisted stack cable, cross-conductor (CroCo), Roebel assembled coated conductor (RACC), conductor on round core (CORC^Ⓡ), HTS cable-in-conduit conductor (CICC), aligned stacks transposed in Roebel arrangement (ASTRA) have been proposed. Some of them are already considered for potential use in some components of the EU-DEMO magnet system. Recently a design of a conductor based on the CORC^Ⓡ concept for the innermost layer of the hybrid Central Solenoid (CS) coil of EU-DEMO was proposed. In the present work we simulated, using the THEA code by Cryosoft, normal operation of this conductor during the current cycle. Two variants of the CS1 geometry were considered: a single CS1 module, and a CS1 module split into two sub-modules (CS1L and CS1U) located one above the other. Taking into account heat loads due to the hysteresis and coupling losses, resulting from time evolution of the magnetic field profile along the conductor, we estimated the minimum temperature margin in the conductor, to verify if it fulfills the performance criterion: min(ΔT_marg) > 1.5 K. The results obtained with the 1D THEA model were complemented by the results of simulations with the ANSYS Mechanical APDL model (3D solid + 1D fluid) aimed at the assessment of radial temperature gradients in the conductor cross-section.