Quench Characteristics of a 2G ReBCO Roebel Cable Pancake Coil in External Fields Up to 8T

Abstract

A pancake coil was wound with a length of ReBCO 2G Roebel cable consisting of 15 strands and studied in detail at different operating temperatures between 4.2 K and 77 K. The coil was impregnated with an epoxy resin and cooling achieved through conduction from current contacts. The critical current was measured with transport currents up to 1500 A and in an external axial field up to 8 T. Quench measurements were carried out following point-like disturbances initiated by a localised miniature heater embedded inside the coil. The different heat dissipation at the current contacts was dynamically controlled with axillary heaters to ensure the isothermal condition of the coil for the successive quench episodes. The minimum quench energy (MQE) was obtained at different temperatures, fields and load currents relative to the critical current. The present work is a substantive follow up of previous studies at 77 K in liquid nitrogen and in helium gas down to 60 K, where it has been established that the coil retained the critical current of the superconducting strand/cable and its quench behaviour was unaffected by the lateral cooling by the cryogen.