5. Transition and protection

Although the entire design of a superconducting magnet is aimed at avoiding quenching, quenching can occur during the life of the magnet (due to a lack of liquid helium, or a major mechanical shock), and care must be taken to ensure that a quench does not damage the magnet. Without an energy extraction system, all the magnet's magnetic energy is converted into heat, and the temperature rise induced can be considerable, especially if the transition remains localized at certain points, known as hot spots.

Beyond the minimum propagation length, a normal zone develops, leading to the transition of the superconducting coil. The normal zone grows under the combined effects of Joule losses and conductive exchanges along the conductor and with the fluid at temperature T ₀ . The resistive front at temperature T _...