Electromagnetic, Thermal, and Mechanical Quench Simulation of NI REBCO Pancake Coils for High Magnetic Field Generation

The no-insulation (NI) winding technique drastically enhances the thermal stability of REBa2Cu3Oy (REBCO) coils. Even if a larger current than a critical current is carried in NI REBCO pancake coils, the coils would not burn out. So far, many NI REBCO pancake coils showed a self-protecting characteristic in experiments. However, most of these experiments have been done under a low magnetic field or cooled by liquid nitrogen. Under these conditions, a huge electromagnetic force does not occur after an NI REBCO pancake coil transitions into a normal state. Recently, the NI winding technique has been applied to high-field magnets, such as NMR and accelerators. Under a high magnetic field (> 20 T), a huge hoop stress is generated after one NI REBCO pancake coil constituting a high-field magnet by stacking reaches to quench. The huge hoop stress causes the delamination of REBCO-coated conductors. That is, the quench protection condition of high-field NI REBCO magnets is decided according to the mechanical condition, even though the magnets show a high thermal stability. In this paper, three simulation models for NI REBCO pancake coils are compared, and then the mechanical condition is discussed for a quench protection through an electromagnetic, thermal, and mechanical simulation of multistacked NI REBCO pancake coils for high field generation.