Safety Factor (q₉₅)
The safety factor q₉₅ measures how tightly magnetic field lines wind around a tokamak — a primary stability margin. Kronos holds an equilibrium-computed q₉₅ ≥ 5.0 floor.
- Symbol
- q₉₅ (safety factor at 95% flux surface)
- MetroVolt floor
- q₉₅(eq) ≥ 5.0 (equilibrium-computed)
- Benchmark
- q₉₅ = 4.94 at 43 MA on the design boundary
- Plasma current
- I_p = 42.5 MA
The safety factor (q) counts how many times a magnetic field line travels the long way around the torus for each time it goes the short way. It is a core measure of tokamak stability: too low, and the plasma is prone to disruptive kink instabilities. Engineers usually quote q95, the value at the flux surface enclosing 95% of the plasma.
Kronos MetroVolt operates at a plasma current of Ip = 42.5 MA under an equilibrium-computed safety-factor floor of q95(eq) ≥ 5.0. A free-boundary benchmark on the design boundary gives q95 = 4.94 at 43 MA, bracketed by the shaped-cylindrical (−17%) and Uckan (+28%) analytic conventions. The design series insists on the equilibrium-computed value as binding, rather than an analytic estimate, because the convention you pick can swing the answer by tens of percent.