Under the strict no-reabsorption bound, the burner radiates 15.6 times its fusion power and never closes. The design survives only because the plasma reabsorbs most of that synchrotron radiation — a reabsorption fraction that has not been measured at these temperatures. This is stated as the most consequential open item in the harvest chain.
Synchrotron radiation emitted by the electrons can be reabsorbed before it escapes, and the burner operates in a regime where that reabsorption is essential: the fitted model that gives a closeable 100 MW loss extrapolates the reabsorption, while the optically-thin bound — zero reabsorption — gives 3,038 MW and no closure. No measurement of the reabsorption fraction at these conditions was available.
This is where the burner is most exposed, and the record says so directly. Rather than hide the dependence inside a chosen formula, the design isolates it: closure rides on cyclotron reabsorption, which is exactly the experiment that would settle the burner's biggest question.
| No-reabsorption case | 3,038 MW radiated (never closes) |
| Radiated vs fusion | 15.6x |
| Survival requires | cyclotron reabsorption |
| Reabsorption fraction | unmeasured at these conditions |
| Status | most consequential open item |