Abstract This work introduces the Plasma Degradation Geometry (PDG) Framework, a formal stability–degradation theory for tokamak plasma dynamics. The framework reformulates plasma stability not as a set of isolated operational limits, but as a geometric trajectory problem defined over an instability field. The central object is a scalar instability functional defined on a state manifold, from which dimensionless invariants are constructed to characterize system behavior under accelerating and noisy conditions. A key contribution is the Plasma Degradation Index (PDI), a real-time computable scalar that aggregates stability, sensitivity, load, and accumulated degradation into a unified predictive signal. Under explicit assumptions, PDI is shown to act as a minimal sufficient statistic for disruption prediction, compressing high-dimensional plasma dynamics into a single control-relevant variable. The framework integrates geometric stability theory, rate-induced instability effects, and control-theoretic principles into a closed-loop architecture: diagnostics → state reconstruction → PDI → control action. A contraction-based stability theorem establishes conditions under which controlled plasma trajectories remain bounded under perturbations. The theory further defines explicit falsifiability criteria and experimental validation protocols across major tokamak devices. PDG provides a unified formal layer linking instability, control, and collapse, enabling a transition from disruption prediction to trajectory-level stabilization in real time.
Roman Lukin (Sun,) studied this question.