Lawson Criterion
A fundamental condition for net thermonuclear fusion power gain, specifying minimum values for plasma density n, energy confinement time τ_E, and temperature T.
Governing formula
n τ_E T ≥ 3 × 10²¹ keV·s/m³ (Triple Product for D-T Ignition)
SI unit
keV·s/m³ (Fusion Triple Product)
In depth
Formulated by John Lawson in 1957. For a fusion reactor to reach ignition (where self-heating by fusion alpha particles sustains reaction without external heating input), fusion energy production must exceed total thermal radiation and conduction losses.
Examples in the real world
Evaluating performance targets for magnetic fusion tokamaks (ITER) and laser inertial confinement (NIF).