The burner's closing point rests on one condition above all others: the end-plug density must reach n_p/n_c ≈ 16. That is a plug density of 4.16×10²¹ per cubic metre — about 347 times what the GDT mirror experiment has measured, and 26 times the best published mirror design. It is the single binding requirement, and it is specified, not demonstrated.
Mirror confinement is set by the confining electrostatic potential, which scales with the logarithm of the plug-to-central density ratio through Pastukhov theory. At the reference ratio of 10 the machine does not close (Q_E 0.63, net -160 MWe); at n_p/n_c=16 it reaches the locked Q_E 1.31. Getting there needs a plug density 347× above GDT-measured — the largest open item in the whole design (H53).
Naming one number, in one component, that one experiment must eventually demonstrate is the most useful thing a design study can do. The burner does not spread its risk across a dozen soft assumptions; it concentrates it in a single requirement and states plainly that the requirement is not yet met.
| Binding parameter | end-plug density ratio n_p/n_c |
| Closing value | ~16 (Q_E 1.31) |
| Reference n_p/n_c=10 | does NOT close (Q_E 0.63, -160 MWe) |
| Plug density needed | 4.16×10²¹ m⁻³ = 347× GDT / 26× best mirror |
| Status | requirement-class, not demonstrated (M-47) |