Quench development and propagation inmetal/MgB2 conductors

Abstract

The thermal stability of different Fe- and Ni-sheathedMgB2 conductors has been studied experimentally and numerically,focusing on the estimation of the quench propagation velocities,vp, minimum quench energies (MQEs) and minimum propagating zones (MPZs). Themeasurements have been done at self-field and under adiabatic conditions, atvariable temperatures and transport currents. Energy pulses were deposited tothe conductor by passing rectangular current pulses through a graphite-basedepoxy heater. The measured voltage around the heater together with numericalsimulation allows the estimation of the minimum propagating zone. Moreover,vp was obtained by measuring multiple voltage taps and thermocouples attachedalong the conductor. The effect of the current sharing temperatures,Ic(T), of the superconductor, and thermal and electrical properties of the metal sheath havebeen analysed. The experimental results are in qualitative agreement with the simulatedones, obtained by solving the one-dimensional heat balance equation of the system.