Fast and accurate electromagnetic modeling of non-insulated and metal-insulated REBCO magnets

TL;DR

This paper introduces a fast, accurate 2D electromagnetic model for REBCO NI and MI superconducting magnets, enabling better design and protection analysis of high-field superconducting magnets.

Contribution

It presents a novel 2D model based on MEMEP for electromagnetic response, validated against existing methods, and analyzes the benefits of metal-insulation in high-field magnet design.

Findings

Metal-insulated coils allow radial current transfer, aiding protection.

Soldered coils with low resistance show reduced AC loss in over-current conditions.

The model can optimize magnet design concerning screening currents and AC loss.

Abstract

REBCO high-temperature superconductors are promising for fully superconducting high-field magnets, including ultra-high field magnets. Non-insulated (NI) and metal-insulated (MI) windings are a good solution for protection against electro-thermal quench. Design and optimization requires numerical modelling of REBCO inserts for high-field magnets. Here, we detail a fast and accurate two-dimensional (2D) cross-sectional model for the electromagnetic response of NI and MI coils, which is based on the Minimum Electro Magnetic Entropy Production (MEMEP). Benchmarking with an $A-V$ formulation method on a double pancake coil shows good agreement. We also analyse a fully superconducting 32 T magnet with a REBCO insert and a low-temperature superconducing (LTS) outsert. In particular, we analyze the current density, the screening curren induced field (SCIF), and the AC loss. We have shown that metal-insulated coils enable transfer of angular current in the radial direction, and hence magnet protection, while keeping the same screening currents and AC loss of isolated coils, even at relatively high ramp rates of 1 A/s. Surprisingly, soldered coils with low resistance between turns present relatively low AC loss for over-current configuration, which might enable higher generated magnetic fields. The numerical method presented here can be applied to optimize high-field magnets regarding SCIF in MI or NI magnets. It also serves as the basis for future electro-thermal modelling and multi-physics modeling that also includes mechanical properties.