Plasma Density & Fuelling

Fusion power rises with the square of density, so running dense is valuable. Kronos operates above the Greenwald limit, sustained by careful fuelling.

Why density

Fusion power ∝ density²

Kronos density

n̄_e = 1.9 × 10²⁰ m⁻³

Greenwald fraction

f_GW = 1.16 (above the nominal limit)

Sustained by

Gas puffing + pellet fuelling

Because fusion power scales with the square of plasma density, running dense is one of the most direct ways to raise output. But density is bounded: push too hard and the plasma approaches the Greenwald limit, where disruptions become likely in conventional plasmas.

Kronos MetroVolt runs at a line-averaged density of n̄_e = 1.9 × 10²⁰ m⁻³ — a Greenwald fraction of 1.16, slightly above the nominal limit — which the negative-triangularity edge makes non-disruptively accessible (NT plasmas sustain up to 1.8× Greenwald). Holding that density in steady state takes active fuelling: edge gas puffing plus deep pellet injection to keep the core supplied, balanced against exhaust and ash removal.