The Kink Instability

The kink is a current-driven instability that can disrupt a tokamak. A safety factor above ~2 (Kronos holds q95 ≥ 5) keeps it at bay.

What

A helical distortion driven by plasma current

Guard

Keep the safety factor high enough

Kronos margin

q95(eq) ≥ 5.0 (well above the q = 2 danger)

Analysis

No-wall kink limit (S21)

The kink instability is a helical distortion of the plasma column driven by the very plasma current that helps confine it — the plasma tries to writhe like a kinking garden hose. If it grows unchecked it drives a disruption. The classic guard is the safety factor: keeping q comfortably above the danger value (near 2) stabilizes the most dangerous kink modes.

Kronos MetroVolt runs with wide kink margin — an equilibrium-computed q95 ≥ 5.0 floor, far above the threshold — and the deposited ideal-MHD analyses (S21, no-wall kink limit) confirm the operating point sits safely inside the kink boundary. The remaining stability frontier at high beta is handled separately by the resistive-wall-mode system.