Resistive Wall Mode (RWM)
The RWM is a slow-growing instability at high beta that the conducting wall only partly suppresses. Kronos holds it with active feedback.
- What
- A kink instability slowed by the conducting wall
- When
- Above the no-wall beta limit
- Kronos control
- Active RWM feedback with rotation + kinetic effects
- Enables
- Operating at β_N = 4.96 in the wall-stabilized regime (computed limit 5.0)
The resistive wall mode (RWM) is a magnetohydrodynamic instability that appears when a tokamak runs above its "no-wall" beta limit. A perfectly conducting wall would stabilize it completely; a real, resistive wall only slows it, so it grows on the wall's timescale — slow enough to catch, but only with active control.
Controlling the RWM is what lets Kronos MetroVolt operate at high normalized beta: the ratified Mode-D point sits at β_N = 4.96, inside the wall-stabilized regime whose computed limit is 5.0 — so RWM control is load-bearing for the operating baseline, not an upside held in reserve. The design uses an active feedback system informed by plasma rotation and kinetic effects, and the wall-stabilized limit is exactly what the deposited stability analyses adjudicate.