Numerical simulation of dynamic loss and total loss in the REBCO tapes under perpendicular AC magnetic fields up to 8 T at 20 K and 50 K

REBCO tapes carry DC current under AC magnetic fields in proposed HTS fusion applications. AC loss will be generated in the process and it is important to understand the AC loss behaviour for safe operation of the fusion magnets. In this work, magnetisation loss (Q_m), dynamic resistance (R_dyn), and total loss (Q_total) in four different REBCO tapes are numerically studied, using the measured $J_c\left(B,\theta \right)$ and $n\left(B,\theta \right)$, for the magnetic field amplitude applied perpendicularly up to 8 T at 20 K and 50 K, where $J_c\left(B,\theta \right)$ represents the magnetic field and field angle ($\theta$) dependent critical current density. The peak of Theva $J_c\left(B,\theta \right)$ data is different from that of other tapes. We artificially shifted the ab-plane peak of Theva $J_c\left(B,\theta \right)$ to the left by 25° to match the peak value. The newly shifted data is named as Theva-shift, which was also investigated to study the influence of the Theva peak shift on AC loss. The normalised DC transport current level (i = I_t/I_c0) ranges from 0.05 to 0.9, where the DC current amplitude and the self-critical current of the tape are represented by I_t and I_c0, respectively. The simulation results show that the AC losses deviate significantly from the Brandt-Indenbom (BI) equation at high magnetic fields. J_c and instantaneous loss curves for different tapes show correlation at high magnetic fields. The simulation results also show how different $J_c\left(B,\theta \right)$ characteristics for different tapes influence AC losses. When AC loss values are scaled by the self-field critical current, Q_m without current and Q_total with current in the different tapes show a good agreement. It implies that the temperature dependence of the two types of loss can be calculated from a known loss at one temperature and the self-field critical current.