Quench development and propagation in metal/MgB2 conductors

The thermal stability of different Fe- and Ni-sheathed MgB2 conductors has been studied experimentally and numerically, focusing on the estimation of the quench propagation velocities, upsilon(p), minimum quench energies (MQEs) and minimum propagating zones (MPZs). The measurements have been done at self-field and under adiabatic conditions, at variable temperatures and transport currents. Energy pulses were deposited to the conductor by passing rectangular current pulses through a graphite-based epoxy heater. The measured voltage around the heater together with numerical simulation allows the estimation of the mininium propagating zone. Moreover, upsilon(p) was obtained by measuring multiple voltage taps and thermocouples attached along the conductor. The effect of the current sharing temperatures, I-c(T), of the superconductor, and thermal and electrical properties of the metal sheath have been analysed. The experimental results are in qualitative agreement with the simulated ones, obtained by solving the one-dimensional heat balance equation of the system.