Protection Design for a 10-T HTS Insert Magnet

The NOUGAT project is the first step toward a 30-T all-superconducting high-field magnet. It combines a 20-T resistive outsert, which is one of the test facilities in the National Laboratory for Intense Magnetic Fields (LNCMI), and a 10-T high-temperature superconductor (HTS) insert. After a brief presentation of the HTS insert, we detail the protection principle that is based on the extraction of the energy simultaneously in a discharge resistance and in copper rings located within the insert. The main role of these rings is to act as a transformer secondary and to dissipate a large fraction of the energy during the discharge. We show that this energy dissipation is not significant enough to consider the rings as passive heaters due to the large temperature margins within the HTS insert. Analytical calculations have also been led on a simple two-loop circuit, and criteria regarding the flux linkage and mutual coupling have been defined to check the efficiency of the protection principle.