Empirical Softplus-Based Fitting Function for Magnetic Field-Angle-Temperature Dependent Critical Current in Commercial REBCO Wires

Accurately estimating the critical current of superconducting wires is essential for the reliable design and simulation of high-performance superconducting magnets. In particular, understanding its temperature dependence is vital for realistic quench simulations. Commercial REBCO wires-also known as 2G HTS wires or REBCO coated conductors-feature oriented crystalline structures in their REBCO layers. These orientations result in a critical current that varies with the angle of the applied magnetic field. Although several models exist for estimating the critical current of REBCO wires, a widely accepted fitting function that simultaneously accounts for magnetic field strength, field orientation, and temperature seems to be absent. In this work, we introduce an empirical fitting function based on the softplus formulation that captures all three dependencies. The proposed model is fitted to…