Magnet Quench Protection
A quench is detected in milliseconds and the coil's energy is dumped to external resistors before local heating can cause damage.
A quench is when part of a superconducting coil warms above its critical temperature and reverts to normal, resistive metal. Current still flows, so that spot heats rapidly. Left unchecked a quench can damage the coil. Quench protection is the system that detects this and removes the coil's stored energy before harm occurs — a mature discipline in large superconducting magnets.
How protection works
- Detection: voltage taps and sensors identify a growing normal zone in milliseconds.
- Trigger: the protection system fires automatically, without operator action.
- Dump: the coil is switched onto external dump resistors that absorb the stored energy.
- Spread: quench heaters distribute the heat so no single spot bears it all.
The design principle is that most of the magnet's energy ends up in resistors outside the coil rather than as heat inside it. At the breeder's 16.84 T peak field and the burner's 26.49 T plug field, the stored energies are large, so the dump circuits and detection thresholds are sized with margin and tested.
Fail-safe behavior
Quench protection is designed to act on loss of power or loss of signal — the safe response is to open the breaker and dump, which also terminates confinement and ends the plasma. This makes the system fail-safe: ambiguity resolves toward de-energizing the magnet. See stored magnetic energy and magnet safety overview.
Quench management is one of the best-characterized safety functions in superconducting engineering, drawn from accelerators and large research magnets.