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Description
No-insulation (NI) rare-earth barium copper oxide (REBCO) magnets have demonstrated the potential to achieve high magnetic fields in compact spaces. Several REBCO magnets, whether combined with resistive outserts or operating standalone, have successfully reached fields over 20 T. However, many quench events have been reported during operation without clearly identified causes, leading to mechanical deformation and increased resistance in REBCO turns and joints.
A notable characteristic of a quench in NI REBCO magnets is the presence of radial leak current. During a quench, when the magnetic field and current change rapidly, current can flow radially within the magnet. This radial flow causes the azimuthal current in each double pancake (DP) coil to vary, resulting in different magnetic stress values for each coil. Such variations may lead to excessive stress at the joints connecting adjacent DP coils, potentially causing mechanical damage.
In this study, we analyze the joint stress of a REBCO solenoid magnet under a background field during a quench. A turn-distributed circuit model coupled with a thermal resistance circuit is used for quench simulation. The azimuthal current in each turn is obtained from the simulation, and these values are then applied in a 2D axisymmetric finite element model (FEM) to simulate joint stress. The joint stress is plotted alongside quench propagation to illustrate how stress changes as the imbalance in current between adjacent DP coils increases.
This work was supported in part by National R&D Program through the National Research Foundation of Korea(NRF) funded by Ministry of Science and ICT(2022M3I9A1072846) and in part by the Applied Superconductivity Center, Electric Power Research Institute of Seoul National University.
