Measurement of AC Insulation Losses at Cryogenic Temperatures

The design of superconducting high voltage transmission lines requires engineering data which, until recently, have been largely unavailable. The selection of a suitable dielectric for a tape-insulated ac cryogenic cable, for example, requires the knowledge of insulation dissipation fagtors at high voltage, which are typically 20 x 10 or smaller. We present here dissipation factor measurements made on several dielectric tapes under consideration by a superconducting power transmission line project as well as on epoxies which appear mechanically suitable as low-tempetature bushing material. The measurement technique and instrumentation are described.