Evaluation of AC losses in toroidal field magnets in the China Fusion Engineering Test Reactor

Toroidal field (TF) superconducting magnets are the key components of the China Fusion Engineering Test Reactor (CFETR). While the TF magnets operate in a steady-state, they are located in a time-varying poloidal field environment, which may lead to AC losses. In this paper, the AC losses of a CFETR TF magnet during excitation and plasma disruption were analyzed. According to the experimental data, the relationship between the critical current density and the magnetic field (Jc-B) was obtained, allowing the hysteresis loss of a TF magnet to be calculated. The results show that the hysteresis loss during excitation is high, at about 1.26 MJ. The coupling loss of a TF magnet can be evaluated when the time constant of a conductor is obtained theoretically. The AC losses of TF magnet joints were analyzed by the same method, which showed that they are much less than those of a TF magnet.