Thermal Stability Analysis of HTS Magnet Stacked by Gourd-Shape HTS Plates With/Without Copper Plates

Persistent current mode (PCM) is an ideal operation mode for high temperature superconducting (HTS) magnets with static magnetic fields. However, it's impracticable for HTS magnets fabricated by winding due to the joint resistance. Recently, several concepts of HTS magnets based on PCM have been proposed, which are stacked by HTS plates and energized by the flux pump or the field cooling (FC) method. This paper focuses on the thermal stability performance of HTS magnets stacked by gourd-shape HTS plates and proposes two improved structures using copper plates for heat dissipation based on the simple stacked structure. One structure is alternately stacked by HTS plate and copper plate. The other one is alternately stacked by HTS plate, HTS plate and copper plate, in which the HTS films of two adjacent HTS plates are back-to-back arrangement. The thermal models of the two improved structures and simple stacked structure are established and the thermal stability under bath-cooling is compared by finite element method. The influence of peripheral edge extension length and thickness of copper plates on thermal stability and magnetic flux density of HTS magnets is also investigated. The results show that, compared with the simple stacked structure, both the two improved structures have better thermal stability. The alternating stacked structure has the best heat dissipation, and the back-to-back structure uses fewer copper plates and has higher excitation efficiency. The two improved structures are potential choices for stable operation of the compact HTS stacked magnets with PCM.