Plasma Beta (β)

Beta measures how much plasma pressure a magnetic field holds — an efficiency and stability metric. Kronos runs β_N = 4.33 with a ≤ 4.5 clamp.

Definition

Ratio of plasma pressure to magnetic pressure

Toroidal beta

β_t = 10.7%

Normalized beta

β_N = 4.33 (Mode C) / 4.96 (Mode B)

Not-to-exceed clamp

β_N ≤ 4.5 for Mode C

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 = 10.7% and β_N = 4.33 at the Mode-C design point (4.96 in the higher Mode-B case), and the plant's control system enforces β_N ≤ 4.5 as a hard, not-to-exceed clamp before any actuator moves. Low aspect ratio and negative triangularity both help raise the achievable beta.