Experimental Study on Shrink-Fitted REBCO Pancake Coils

This study focuses on two challenges associated with pancake-wound REBCO magnets: 1) mechanical damage in module coils 2) issues related to electrical joint implementation. Shrink-fitting an external ring structure around the pancake coil can resolve the problems by inducing compressive radial and hoop stress, opposing magnetic stress. Moreover, the ring can serve as an electrical joint between pancake coils, facilitating the easy replacement of malfunctioning module coils within this joint structure. In this study, we fabricated a small pancake wound no-insulation magnet with copper shrink-fit joints. Each pancake is surrounded by a ring-shaped copper structure with a rectangular cross-section, achieved through shrink-fitting. We present detailed manufacturing procedures and measured contact resistances. The result demonstrates that shrink-fitting can be applied to pancake wound magnets and perform novel modular design and mechanical reinforcement. This experiment suggests a new approach to implementing electric connection and reinforcement in REBCO pancake-wound magnets.