Quench onset and propagation in Cu-stabilized multifilamentMgB2 conductors

Abstract

The quench development of Cu-stabilized metal-sheathedMgB2 conductors has been analysed. Experimentally, energy pulses were deposited into theconductor by passing rectangular current pulses through a graphite-based epoxy heater.The temperature and the electric field profiles around the point heat disturbance that givesrise to a quench, as well as their time evolution, were measured from multiplevoltage taps and thermocouples along the conductor. The measurements have beendone at self-field under two different conditions: in vacuum and in Ne vapour. Theexperimental results are in qualitative agreement with the simulated ones, obtained bysolving the one-dimensional heat balance equation of the system and using a finiten valuecharacterizing the I–V curves (V∝In). The temperature and current dependences of the minimum quench energy and thequench propagation velocity are presented. Our results show that the nonlinear power-lawcurrent sharing in the normal zone had significant influence on the onset of the quenchprocess and resulted in a marked deviation from the classical quench theory based on thecritical state model.