disruption is a sudden loss of plasma stability that terminates a tokamak discharge and dumps the plasma's stored thermal and magnetic energy into the surrounding machine.
A disruption unfolds in two phases. In the thermal quench, the confined 📝plasma loses its heat to the wall in roughly a millisecond. In the current quench that follows, the megaampere-scale 📝plasma current collapses, inducing eddy and halo currents in the vessel that produce large electromagnetic forces, and sometimes accelerating a beam of 📝runaway electrons. Disruptions strike when a 📝Tokamak is pushed past its stability limits — density above the 📝Greenwald limit, too little margin in the 📝safety factor (q), or a 📝magnetic island that grows, locks to the wall, and triggers the collapse. The term should not be confused with a quench in the magnet sense: a magnet quench is a superconductor losing superconductivity, while a disruption is the plasma losing stability.
Because the energy released scales with the machine's stored energy, disruptions grow from a nuisance in small experiments to a first-order design constraint at reactor scale. The response is layered: prediction and avoidance through real-time control, and mitigation — ITER's chosen system injects shattered frozen pellets to radiate the energy away harmlessly — when a disruption cannot be avoided. 📝Ryan Sweeney has published the disruption case for both CFS machines: the 2020 SPARC analysis inside 📝The SPARC Physics Basis (2020), which projects halo current forces up to 50 meganewtons, and the 2026 paper on 📝ARC in 📝The ARC Physics Basis (2026), which finds every load within a factor of two of SPARC's and sets a design target of one mitigated disruption per day.