An Active Quench Protection System for MRI Magnets

An active quench protection system is developed to safely protect a 1.5 T superconducting MRI magnet. The protection system includes a digital quench detection controller, a set of quench heaters and voltage taps, a battery backed DC power supply and solid-state switches. The quench controller takes the voltage signals from the voltage taps over superconducting coils and monitor a quench onset. To distinguish a quench signal from operational signals, the quench controller uses a pre-determined moving average voltage over 50 ms as the threshold signal for quench detection. The threshold signal is more than 10 times larger than any of the normal operation signals to avoid false quenching. Once detected moving average voltage exceeds the threshold, the quench controller will close solid-state relays and power quench heaters to accelerate the quench propagation over the entire magnet. The system has been tested in a MRI magnet test module.