The Plug-Density Caveat
The burner design carries a genuine open constraint: the tandem-mirror plug requires a density condition Kronos states plainly rather than assuming away.
A caveat we refuse to hide
The burner (Aegis / MetroVolt) is a D-3He tandem-mirror generator. Tandem mirrors confine plasma with high-field magnetic 'plugs' — 26.49 T at the plug, 17 T at the throat. Whether those plugs hold the central plasma at feasible parameters depends on a demanding plug-density requirement. This is a real physics constraint, and it is the burner's central open gate.
What the caveat says
Our own phase-2 closure work is explicit that at feasible beta the burner does not clearly establish the magnetic well it needs, and that the closing design point depends on a plug-density condition that must be demonstrated, not assumed. Publishing a burner performance figure without this caveat would overstate how settled the machine is.
Why say it out loud
- An engineer evaluating the burner needs to know the load-bearing assumption
- Named retirement experiments exist to test exactly this condition
- Hiding it would make a later negative result look like a reversal instead of a resolved gate
The burner is a design and simulation study. Its most important number is not a performance figure — it is the caveat that says which condition everything else rests on.