The burner runs at an ion temperature of 100 keV, near a genuine interior optimum in the 80-100 keV band. Higher is not simply better: reactivity rises with temperature while the confining potential relative to it falls, so confinement degrades. The design sits on the balance.
Two effects compete. Fusion reactivity climbs with ion temperature, favoring hotter plasma. But the confining potential ratio phi_i/T_i falls as T_i rises, degrading confinement. The product has a maximum in the 80-100 keV range — a real optimum, computed, not a monotone push toward higher temperature.
Finding and sitting on an interior optimum, rather than assuming hotter is always better, is the kind of result that only falls out of a self-consistent solve. It also means the operating window is two-sided in temperature, which is friendlier to control.
| Ion temperature T_i | 100 keV |
| Optimum band | 80-100 keV (interior) |
| Rises with T_i | reactivity |
| Falls with T_i | confining ratio phi_i/T_i |
| Window | 70-120 keV within 10% of reference |