Development of a novel hybrid protection system for superconducting MRI magnets

In order to reliably protect the superconducting MRI magnets as soon as possible, a hybrid protection system is developed. The protection system, which combines the both merits of active and passive protection schemes, includes a quench detection controller, a protection superconducting switch, a capacitor bank, a strip heaters network and a protection circuitry with back to back diode sets and shunting resistance coils. The quench detection controller is employed to detect the start of a quench and to subsequently switch on the capacitor bank to quench the protection superconducting switch. The shunting current in the coil subdivision flows through the shunting resistance coil also to quench the protection superconducting switch. The voltage across the protection superconducting switch energizes the strip heaters. Once a quench occurs in a magnet, the protection system immediately initiates all superconducting coils to quench. The hybrid protection system is successfully applied to a 1.5 T whole-body MRI magnet. This paper describes the details of the hybrid protection system and presents the quench simulation results.