Aspect Ratio

Aspect ratio is the ratio of a tokamak's major to minor radius. Kronos runs a low A = 2.0 — the spherical regime — for stability and pressure efficiency.

Definition

A = R₀ / a (major radius ÷ minor radius)

Conventional tokamak

A ≈ 3–4

Kronos MetroVolt

A = 2.0 (R₀ = 5.75 m, a = 2.875 m)

Benefit

Higher beta, better stability

Aspect ratio (A) is the ratio of a tokamak's major radius (how big the doughnut is) to its minor radius (how fat the plasma tube is). It is the single number that most defines a machine's shape. Conventional tokamaks sit at A ≈ 3–4 — thin doughnuts; spherical tokamaks push toward A ≈ 1.5–2, squeezing the hole in the middle until the plasma resembles a cored apple.

Kronos MetroVolt runs at A = 2.0 (R₀ = 5.75 m, a = 2.875 m). Low aspect ratio raises the plasma pressure achievable for a given field (higher beta) and improves stability, at the cost of a crowded center stack where the inboard magnet and shield must fit in little radial space — a constraint the low-neutron fuel choice helps relieve.