Deep Dive: The Hot-Ion Posture

Running the ions hotter than the electrons raises fusion output and limits losses — a real upside Kronos treats as a bet, with the near-thermal case as the operating baseline.

Condition

T_i/T_e ≥ 1.5 (prediction P2)

Ceiling

P_fus 2.41 GW, P_net 0.84 GWe

Baseline

near-thermal, P_fus 1.5 GW, P_net 0.4–0.5 GWe

Bound

channeling redress ≤ ~30%

Fusion rate rises with ion temperature, while radiation losses concentrate in the electrons — so running the ions hotter than the electrons (T_i/T_e > 1) buys more fusion for less loss. Kronos targets central temperatures of 65–70 keV (ions) against 34 keV (electrons), and the physics helps: driving T_i/T_e toward 1 raises the ITG turbulence threshold about 1.3×.

Crucially, Kronos states this as a ceiling, not a baseline. The hot-ion ceiling reaches P_fus ≈ 2.41 GW and P_net ≈ 0.84 GWe — but a full Spitzer equilibration analysis (S61) found the hot-ion posture is not sustainable at that ceiling, and the channeling redress of the hot-ion "tax" is bounded at about 30% even at perfect efficiency (S72).

So the honest operating baseline is near-thermal: P_fus ≈ 1.5 GW, P_net ≈ 0.4–0.5 GWe. Kronos plans and prices to that baseline and treats the hot-ion upside as something to be earned at the G1 gate (prediction P2).