Physics / mechanism
Tokamaks confine deuterium-tritium plasma in a toroidal magnetic field using superconducting coils (toroidal field) plus induced plasma current (poloidal field) to achieve the Lawson criterion: nτE·T ≥ 3×10²¹ keV·s/m³. Fusion ignition requires plasma temperatures ~150 million K, sustained energy confinement time τE >3s at sufficient density. Key figure of merit is Q (fusion energy out / heating energy in); ITER targets Q=10, JET achieved Q≈0.67 (2022, 59 MJ record). Superconducting coil technology (REBCO high-temperature superconductors) is the current inflection point—Commonwealth Fusion’s SPARC targets Q>2 by ~2027 using 20T HTS magnets, compressing timelines by ~decade versus ITER.
Competitive landscape
ITER (state/multilateral) and Commonwealth Fusion Systems (private, SPARC) lead tokamak. Competing confinement geometries include stellarators (Wendelstein 7-X, no plasma current, better steady-state), inertial confinement (NIF, laser-driven, achieved ignition Q>1 in 2022 but rep-rate unsolved), and alternative private approaches (TAE’s field-reversed configuration, Helion’s FRC targeting direct electricity conversion).
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.