Disruptions and Plasma Quench
A disruption ends the plasma abruptly; its loads are engineered for, and it removes rather than adds energy to the reaction.
A disruption is a sudden loss of plasma confinement in a tokamak — the plasma current collapses and the discharge terminates in milliseconds. It is the breeder's most demanding transient, but it is a shutdown event: it ends the fusion reaction. The engineering challenge is managing the mechanical and electrical loads of the termination, not preventing a runaway.
What a disruption produces
- Thermal quench: the plasma dumps its (small) thermal energy to the first wall.
- Current quench: the plasma current (up to 9.86 MA) decays rapidly, inducing forces.
- Halo and eddy currents: mechanical loads on the vessel and structures.
- Runaway electrons: a beam of fast electrons that must be dissipated — mitigated by design.
Disruption loads are designed for: the vessel and plasma-facing components are built to withstand the electromagnetic forces, and disruption mitigation systems (such as massive gas or pellet injection) can be fired to soften the termination and suppress runaway electrons. The negative triangularity shape (δ = −0.30) is part of a stability strategy that also bears on disruption behavior.
Why it is not a safety cliff
A disruption removes energy from the reaction; it is a fast version of the shutdown that any loss of input produces. It stresses hardware, but it cannot cause a chain reaction, a melt, or a large release. See the off-normal catalog and why fusion cannot run away.
The mirror-based burner has no tokamak-style current disruption; its analogous event is loss of plug confinement, which likewise ends the burn.