The burner's engineering gain is what survives after the plant pays to sustain its own plug and drive its own plasma. At the reference point that recirculating fraction is 158% — the plant circulates more power internally than it nets — which is exactly why Q_E sits at 0.63.
Auxiliary heating power of 195 MW sustains the reference plasma, split between ions and electrons, against a directed output that only partly funds it. The recirculating fraction of 158% is the gap the plug ratio must close: raising the plug density ratio deepens the confining potential, cuts the auxiliary power required, and drives the recirculating fraction down toward closure.
The recirculating power is where closure is won or lost. Publishing it — rather than a bare gain number — shows precisely how much the plant spends on itself and how much the binding plug requirement has to recover. It makes the closure gate quantitative.
| Auxiliary heating power | 195.4 MW (reference) |
| Recirculating fraction | 158% |
| Engineering gain Q_E | 0.632 |
| Closed by | raising plug density ratio |
| Split | 68.3 MW ions / 127.1 MW electrons |