Hot-ion mode.

Fusion happens between ions, but energy leaks mostly through electrons. Running the ions hotter than the electrons — hot-ion mode — buys more fusion for less loss. Both Kronos machines lean on it.

Hot-ion mode

Ion temperature > electron temperature

Benefit

More fusion power, less radiation loss

Breeder

Hot-ion operation supports its gain

Burner

Ion temperature ≈ 90 keV

Fusion reactivity depends on how hot the ions are, while the biggest radiation losses (bremsstrahlung, synchrotron) scale with the electrons. If you can keep the ions hotter than the electrons — hot-ion mode — you get more fusion per unit of radiated power. It is a lever both Kronos machines use.

The burner is an extreme case: it runs at an ion temperature near 90 keV, far above where D–³He would otherwise be practical, precisely because the charged-particle payoff justifies the heat. The breeder uses a milder hot-ion posture to reach its gain. In both, the electron channel is a named loss term in the deposited power balance, not an afterthought.