Thermonuclear ignition in inertial confinement fusion and comparison with magnetic confinement

TLDR

The physics of thermonuclear ignition in inertial confinement fusion is framed by a Lawson‑type criterion. The study proposes a performance metric that incorporates both the ignition parameter χ and the product Pτ. The authors express the ICF ignition condition as the product of plasma pressure and confinement time (Pτ) and an overall ignition parameter χ, and compare these metrics between inertial and magnetic‑confinement fusion. Cryogenic implosions on OMEGA achieved Pτ≈1.5 atm s, comparable to large tokamaks, but their ignition parameter χ≈0.02–0.03 is about five times lower than JET’s χ≈0.13. Commun.

Abstract

The physics of thermonuclear ignition in inertial confinement fusion (ICF) is presented in the familiar frame of a Lawson-type criterion. The product of the plasma pressure and confinement time Pτ for ICF is cast in terms of measurable parameters and its value is estimated for cryogenic implosions. An overall ignition parameter χ including pressure, confinement time, and temperature is derived to complement the product Pτ. A metric for performance assessment should include both χ and Pτ. The ignition parameter and the product Pτ are compared between inertial and magnetic-confinement fusion. It is found that cryogenic implosions on OMEGA [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] have achieved Pτ∼1.5 atm s comparable to large tokamaks such as the Joint European Torus [P. H. Rebut and B. E. Keen, Fusion Technol. 11, 13 (1987)] where Pτ∼1 atm s. Since OMEGA implosions are relatively cold (T∼2 keV), their overall ignition parameter χ∼0.02–0.03 is ∼5× lower than in JET (χ∼0.13), where the average temperature is about 10 keV.