CLIQ – Coupling-Loss Induced Quench System for Protecting Superconducting Magnets

The recently developed Coupling-Loss-Induced Quench (CLIQ) protection system is a new method for initiating a fast and voluminous transition to the normal state for protecting high energy density superconducting magnets. Upon quench detection, CLIQ is triggered to generate an oscillating current in the magnet coil by means of a capacitive discharge. This in turn introduces a high coupling loss in the superconductor which provokes a quick transition to the normal state of the coil windings. The system is now implemented for the protection of a two meter long superconducting quadrupole magnet and characterized in the CERN magnet test facility. Various CLIQ configurations with different current injection points are tested and the results compared to similar transients lately measured with a not optimized configuration. Test results convincingly show that the newly tested design allows for a more global quench initiation and thus a faster discharge of the magnet energy. Moreover, the performance of CLIQ for reducing the hot spot temperature after a quench is compared to what can be achieved with conventional quench heaters. In addition, the measured transients are reproduced by means of a lumped-element dynamic electro-thermal model developed with Simulink©. After its validation, the model is now in use for simulating various discharges in order to find the optimum CLIQ configuration and operating parameters for the most homogeneous transition to the normal state of the coil windings and hence the lowest hot spot temperature. Finally, the integration of the new CLIQ system with conventional protection systems like quench heaters and energy extraction is thoroughly discussed for incompatibilities and effective synergies.