A head-to-head comparison of the two leading magnetic confinement concepts — the tokamak’s proven performance versus the stellarator’s inherent steady-state capability and disruption immunity.
Tokamaks and stellarators are both toroidal magnetic confinement devices, but they create their confining magnetic fields differently. This fundamental difference has cascading consequences for performance, engineering, and reactor design.[1]
Higher confinement: Tokamaks have historically achieved better energy confinement than stellarators, thanks to their axisymmetric field. Simpler coils: Tokamak coils are planar circles (or D-shapes), much easier to manufacture than stellarator coils. Proven performance: Tokamaks hold all records for fusion triple product and have decades more experimental data. ITER is a tokamak.[2]
No disruptions: Without a large plasma current, stellarators cannot disrupt — eliminating the most dangerous operational risk for tokamaks. Inherent steady state: Stellarators need no current drive, eliminating the central solenoid and recirculating power for current drive. No density limit: Stellarators are not subject to the Greenwald density limit. No runaway electrons: Without a large plasma current, the runaway electron problem does not exist.
Wendelstein 7-X has demonstrated that optimised stellarators can approach tokamak-level confinement. Several private companies (Type One Energy, Proxima Fusion, Thea Energy) are betting that modern HTS magnets and computational optimisation have closed the historical performance gap. The fusion community increasingly views both concepts as viable.[3]