The normal-zone propagation properties of the non-insulated HTS coil in cryocooled operation

High temperature superconducting (HTS) coils wound with HTS wires have very low normal zone propagation velocity (NZPV) and complicated quench behaviors because the wires have a high thermal stability and large specific heat. According to these reasons, in case of HTS coils and magnets, it is difficult to expect the self-protection like low temperature superconducting (LTS) coils. In this paper, we suggest a method which can remove the insulation among turn-to-turn in the coil to improve the self-protection property of HTS coils. Because the thermal and electrical contacts along transverse direction are enhanced by no turn-to-turn insulation, the whole thermal stability of HTS coils begins to increase. Furthermore, although a quench occurs in the coil, it is possible to realize a self-protection of HTS coil because the current path of the coil is modified in order to avoid quenching. To confirm a quantitative evaluation for quench behavior of the suggested coil, we carried out the measurements with the coils having variety types of turn-to-turn insulation. The experimental results and the self-protection ability about the tested coils will be presented.