Effect of Alternative Insulation Materials on Quench Propagation in ReBa2Cu3O7-delta Coils

ReBa2Cu3Odelta-7 (REBCO) coils have the potential to impact a variety of magnet applications but due to slow normal zone propagation velocity (NZPV), quench detection and protection remain difficult. It is therefore important to understand how quench behavior is affected by various aspects of coil design, geometric considerations and material properties. Although past studies have explored the effects of varying the conductor properties, it is important to investigate the influence of insulation as well.;In this study, the effect of insulation properties on three-dimensional (3D) quench propagation in REBCO-based coils is investigated. At present, superconducting magnets primarily use insulators that are electrically and thermally insulating; typically Kapton. Here the impact of electrically insulating, thermally conducting insulators on quench behavior was studied. In particular, the behavior of a Kapton insulated coil was compared to doped-TiO2 and ideal Al2O3 insulated coils. A non-insulated coil was also evaluated. Using a mixed-dimensional model the effect of various insulation materials on multiple quench parameters in REBCO coated conductor coils was studied. The comparison of the usage alternative insulation was conducted for a 20 mum and 100 mum case using three models: Concept Model 1, 2 and 3. Concept model 1 studied the effects on 3D propagation behavior, including the 3D current sharing volume (CSV) and key quench parameters, including minimum quench energy, hotspot temperature and NZPV. Concept model 2 (CM 2) cooled a room temperature coil configuration from room temperature to 50 K for a 15 min duration. The radial and hoop stresses were observed at the cleavage edge, middle height and along the conductor width in the central conductor. Concept model 3 (CM 3) determined the thermal stresses based upon the thermal development of CM 1 during a quench.;Concept model 1 found that ideal Al2O3 insulation resulted in the highest MQE, lowest peak temperature, slowest rate of increase in hotspot temperature, fastest transverse NZPV and smallest CSV. These results indicated that increasing the thermal conductivity of coil insulation can significantly improve coil behavior. Concept model 2 found that doped- TiO 2 and ideal Al2O3 had the most desirable effect by having the most compression within the conductors. The compression present during cool down could lessen the effect of tension during operation. CM 3 showed that NI has less tensile variation between the REBCO layers and could be helpful so that stress is distributed evenly to reduce stress concentrations. Doped -TiO2 had the lower stress values for each insulation thickness. The lower stress is desirable to reduce the risk for delamination.