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High temperature superconductor (HTS) coils are widely acknowledged to have greater stability margins than their low temperature superconductor (LTS) counterparts. In particular, no-insulation (NI) coils are often assumed to exhibit even greater stability owing to enhanced thermal conduction between turns and inherent current-bypass capabilities. However, we hypothesize that this assumption may not universally hold true. Specifically, reducing the turn-to-turn contact resistivity in NI HTS coils may actually heighten their quench susceptibility, because normal zones can propagate via an electromagnetic “inductive-type” mechanism rather than relying solely on the conventional “diffusive-type” thermal conduction. This fundamental difference in quench propagation may necessitate distinct methodologies for assessing the stability of NI HTS coils.
In this study, we examine the influence of turn-to-turn contact resistivities on the stability of single-pancake NI HTS coils by investigating their contact resistivity-dependent quench behavior. Our findings reveal that stability against inductive-type quenches could decrease as inter-turn contact resistivity is lowered, indicating an increased vulnerability of NI HTS coils to inductive-type quenches when inter-turn contact resistivity is excessively reduced.
