Lawrence Berkeley National Laboratory

Conventional quench protection systems for high-magnetic-field superconducting magnets are based on external heaters composed of resistive strips in close contact with the coil and rely on thermal diffusion across insulation layers on the order of tens of micrometers. The large contact areas between the coil and the heater strips, and the thin insulation between them required for an effective protection constitute a significant risk of electrical breakdown and one of the most common causes of magnet damage. Coupling-loss-induced quench (CLIQ) technology offers a valid option for a time-and cost-effective repair of magnets with failing heater-based protection systems. In fact, its effective heating mechanism utilizing coupling loss, its robust electrical design, and its fast implementation, as compared to alternative repair options, constitute definite advantages over the conventional technology. In the past years, CLIQ was successfully implemented on various coils in a single-magnet configuration. Now the design of a CLIQ-based protection system integrated in a chain of series-connected magnets is presented. The protection of a chain of superconducting magnets usually is considerably more challenging than the protection of stand-alone magnets due to the increased energy stored in the circuit and the presence of transitory effects. The effectiveness of this new method is demonstrated by means of electrothermal simulations modeling the transition to the normal state and the temperature evolution in one quenched magnet, and the electrodynamics of the entire magnet chain.