Plasma Beta (β)
Beta measures how much plasma pressure a magnetic field holds — an efficiency and stability metric. Kronos runs β_N = 4.96 at the frozen Mode-D point, wall-stabilized against the computed 5.0 limit.
- Definition
- Ratio of plasma pressure to magnetic pressure
- Toroidal beta
- β_t = 11.6% (Mode D)
- Normalized beta
- β_N = 4.96 (Mode D, wall-stabilized); 4.33 = Mode-C era, labeled history
- Computed limit
- β_N ≤ 5.0 — binding; the banking leg trims to it
Beta (β) is the ratio of plasma pressure to magnetic pressure — a direct measure of how efficiently a machine turns its expensive magnetic field into confined plasma pressure. Higher beta means more fusion power for a given field, but every configuration has a stability ceiling beyond which the plasma disrupts.
Engineers track the normalized beta, β_N, which folds in current and size to express how close the plasma sits to that ceiling. Kronos MetroVolt operates at β_t = 11.6% and β_N = 4.96 at the ratified Mode-D point — inside the wall-stabilized regime, against a computed limit of 5.0 that is binding (the banking leg is density-trimmed to it); the control system enforces that limit as a hard, not-to-exceed clamp before any actuator moves. The Mode-C-era point (β_N 4.33 under a 4.5 clamp) is labeled history. Low aspect ratio and negative triangularity both help raise the achievable beta.