Ion-Temperature-Gradient (ITG) Turbulence

ITG modes are the dominant heat-loss turbulence in hot plasmas. Running the ions hotter than the electrons raises the ITG threshold — a key Kronos lever.

What

Turbulence driven by the ion temperature gradient

Effect

A primary channel for ion heat loss

Kronos lever

T_i/T_e → 1 raises the ITG threshold ≈ 1.3×

Related

Hot-ion posture, negative triangularity

Ion-temperature-gradient (ITG) turbulence is, in most reactor-relevant plasmas, the single largest source of turbulent ion heat loss. It switches on once the ion temperature gradient exceeds a critical value, so much of transport physics is about keeping the plasma just below — or managing the consequences of exceeding — that ITG threshold.

Kronos MetroVolt uses two levers against it. Negative triangularity reshapes the turbulence, and the hot-ion posture helps directly: reduced-order analysis finds that driving the temperature ratio T_i/T_e toward 1 raises the ITG critical gradient by roughly 1.3×, which is part of the physics case behind the confinement requirement. The definitive check is the outstanding nonlinear gyrokinetic study.