Temperature and Background Field Dependence of Thermal Stability in a Compact MgB 2 Solenoid Coil

A conduction-cooled compact react and wind MgB
₂
solenoid magnet was tested for quench propagation and minimum quench energy (MQE) in a background field, which allows to an extent a decoupling of the peak field in the windings from the conductor field performance. MQE and propagation data were taken in self-field at 30 K, 30.5 K, and 31.5 K and at fields/temperatures of 1 T/25 K, 3 T/18 K, and 5 T/10 K where the power law n-value characteristic was similar at n ~ 30. At all temperatures and at low I/I
_c
, quench propagated first through the insulating layers, in a radial direction, and at high I/I
_c
within the layer. The MQE values as a function of I/Ic are shown to consistently have nonzero values as I → I
_c
, which is characteristic of an analytical quench model that includes the n-value power law dissipation. At 30.5 K, a sharp drop in MQE occurs along with the change in propagation direction. The analytical model is then exploited as 1-D adiabatic, 3-D infinite solenoid, and 3-D with heat transfer at the boundary to explore the effect of dimensionality and conduction cooling on the propagation and MQE behavior.