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The thermal diffusion properties of several different kinds of YBCOinsulations and the quench properties of pancake coils made using theseinsulations were studied. Insulations investigated include Nomex, Kapton, andMylar, as well as insulations based on ZnO, Zn2GeO4, and ZnO-Cu. Initially,short stacks of YBCO conductors with interlayer insulation, epoxy, and acentral heater strip were made and later measured for thermal conductivity inliquid nitrogen. Subsequently, three different pancake coils were made. Thefirst two were smaller, each using one meter total of YBCO tape present as fourturns around a G-10 former. One of these smaller coils used Mylar insulationco-wound with the YBCO tape, the other used YBCO tape onto which ZnO basedinsulation had been deposited. One larger coil was made which used 12 totalmeters of ZnO-insulated tape and had 45 turns. The results for all short sampleand coil thermal conductivities were ~1-3 Wm-1K-1. Finally, quench propagationvelocity measurements were performed on the coils (77 K, self field) byapplying a DC current and then using a heater pulse to initiate a quench.Normal zone propagation velocity (NZP) values were obtained for the coils bothin the radial direction and in the azimuthal direction. Radial NZP values(0.05-0.7 mm/s) were two orders of magnitude lower than axial values (~14-17mm/s). Nevertheless, the quenches were generally seen to propagate radiallywithin the coils, in the sense that any given layer in the coil is drivennormal by the layer underneath it.

Thermal Diffusion and Quench Propagation in YBCO Pancake Coils Wound with ZnO-and Mylar Insulations