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Description
The parallel-wound No-insulation (PWNI) high temperature superconducting (HTS) coil is a novel type of pancake-shaped no-insulation coil made by parallel-staked HTS tapes, which is a promising solution for high field magnets. Previous studies have analyzed the electromagnetic characteristics of a PWNI HTS coil during the ramping process through simulations. The current distribution of these models is mainly solved from the equivalent circuit model. However, these models would lose axial fidelity and the computation cost of the equivalent circuit model is too large to calculate the multiple PWNI HTS coil. This paper is to investigate the ramping behaviour of the PWNI HTS magnet for a single silicon crystal growth system through finite-element modelling using rotated anisotropic resistivity. The results show that the turn-to-turn losses and magnetization losses show a significant non-uniform distribution among different coils during the ramping process. The middle coils of the magnets produce higher turn-to-turn losses but lower magnetization losses. The turn-to-turn losses are much higher than the magnetization losses so the total losses show higher values at the middle coils of the magnet. The non-uniform loss distribution would lead to a large temperature difference among the different coils of the magnet, which might cause a local quench to the magnet. By grading distributed the turn-to-turn resistivity, the loss can be adjusted relatively uniformly. This will provide some useful guidelines for the design of PWNI HTS magnets for single silicon crystal growth systems.
