An analytical framework for computing AC losses in the HTS insert of the EU-DEMO central solenoid

Abstract

High-temperature superconductors (HTS) are being explored for integration into coil systems for magnetic confinement fusion, due to their ability to extend operational margins in terms of temperature, current, and magnetic field. Recently, a conductor design based on a sector-assembled (SECAS) cable-in-conduit-conductor (CICC) concept was proposed for the innermost layer of the central solenoid (CS) module in the EU-DEMO tokamak. The dynamic nature of plasma scenarios, characterized by rapid variations in current and magnetic fields, induces significant AC losses in the superconducting magnets. These losses can be particularly pronounced during phases like plasma start-up and control operation, where field variations can be significant. In this study, we evaluate the instantaneous power losses — both hysteretic and coupling losses — during a baseline plasma scenario using an analytical model that accurately accounts for the temporal evolution of the magnetic field profile within the innermost layers of the CS1 HTS insert.