Quench development and propagation in metal/MgB₂conductors

Abstract

The thermal stability of different Fe-and Ni-sheathed MgB 2 conductors has been studied experimentally and numerically, focusing on the estimation of the quench propagation velocities, v 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 minimum propagating zone. Moreover, v 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.

Numerical and Experimental Analysis of Normal Zone Propagation on 2G HTS Wires

“…Since MQE values depend on the pulse duration, t p [9], it is important to fix this value to get the MQE(I,T) dependence. The use of t p =40 ms is arbitrary, but it has been chosen since it is much higher than the time step of the measurements (0.3ms) and allows the MQE measurement at low currents.…”

Quench Characteristics of a Cu-Stabilized 2G HTS Conductor

“…The energy deposited was varied with a resolution up to 0.5% by changing the level and duration of the electrical pulse. Further details of the experimental procedure can be found in earlier publications [7][8].…”

Quench Characteristics of a Stabilizer-Free 2G HTS Conductor

“…The energy deposited was varied with a resolution up to 0.5% by changing the level and duration of the electrical pulse. Further details of the experimental procedure can be found in earlier publications [6], [7].…”