Technical Papers and Presentations

Quench detection- and protection are critical for superconducting magnets due to their high current density which translates to high stored magnetic energy. During a sudden discharge, this can dissipate inhomogeneously in the winding pack as heat and may cause irreversible damage if left unaddressed. In this work, a novel quench detection and protection principle called Rapid Quench Transformation is investigated on a co-wound Nb-Ti and Cu solenoid demonstrator magnet. Similar to a co-wound voltage tap, the secondary coil suppresses inductive noise, facilitating low-noise quench detection. For quench protection, the demonstrator magnet features a rapid initial discharge of the superconducting coil using dump resistors, followed by inductive current transfer to the secondary coil, minimizing the external voltages. A COMSOL Multiphysics simulation describing the electromagnetic and thermodynamic quench behaviour of such a system is shown together with experimental results. For quench detection, an adiabatic hotspot temperature calculation was made based on a quench integral obtained from COMSOL to determine whether repeated discharging of the coil poses a risk of damaging the coil. As part of the quench protection study, a 2D-axisymmetric time-dependent study was made for current and voltage characteristics during a fast discharge. Peak discharge voltage was found to be 45 V together with a fourfold reduction in Nb-Ti coil current within 300 ms from opening the main breaker. The simulation results were compared to the experiment and found to be in good agreement. Compared to a typical single-conductor superconducting coil without quench-back, using the co-wound coil method, the necessary energy extraction voltage is reduced by more than one order of magnitude, highlighting the improved safety aspect of such a design.