Deep Dive: Lawson & the Triple Product

The condition for net fusion — density × temperature × confinement time — done honestly with radiation losses, yielding the H98 = 1.84 requirement and a driven, not igniting, operating point.

Triple product

n · T · τ_E

With losses

Bremsstrahlung 498 MW, synchrotron 51 MW

Requirement

H98 = 1.84 (profile basis)

Operating point

Driven, not ignited

The Lawson criterion — expressed as the triple product of density, temperature, and confinement time — is the bar a plasma must clear for net fusion. Kronos evaluates it with radiation losses included, because a high-field, high-density plasma radiates strongly.

Folding in bremsstrahlung (498 MW) and synchrotron (51 MW at R_wall = 0.90), the confinement multiplier the chain requires is H98 = 1.84 — the largest bet in the design. The plant reaches its target triple product through high density (n̄_e = 1.9 × 10²⁰ m⁻³), high ion temperature (65–70 keV), and the confinement negative triangularity is meant to deliver.

Crucially, Kronos is honest that the resulting operating point is driven, not igniting — strongly net-positive (Q_eng ≈ 2.1–2.7), but sustained by continuous heating. Doing the Lawson analysis with losses, and stating the driven result plainly, is part of the design's honesty. See the confinement case.