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FusionBenchmark

Tokamak vs stellarator

Both confine plasma magnetically in a torus. The difference is where the twist in the magnetic field comes from — and everything else follows from that.

Tokamak

Doughnut-shaped magnetic confinement using a strong toroidal field plus a current driven through the plasma itself. The most-studied configuration, and the one ITER uses.

72 devices · 10 organisations · 371 measurements

Definition and every record using it

Stellarator

Confinement produced entirely by external coils twisted into complex three-dimensional shapes, with no current driven through the plasma. Far harder to build than a tokamak and inherently steady-state rather than pulsed.

12 devices · 9 organisations · 43 measurements

Definition and every record using it

The differences that matter

Tokamak vs stellarator compared
  Tokamak Stellarator
Where the field twist comes from A current driven through the plasma itself. The shape of the external coils alone.
Consequence for operation The plasma current must be sustained, which historically meant pulsed operation and makes long steady-state discharges hard. No plasma current is needed, so steady-state operation is natural. This is the central advantage.
Disruptions A sudden loss of plasma current can dump the stored energy into the wall. Disruption mitigation is a major engineering programme. No plasma current means no current-driven disruptions.
Engineering difficulty Coils are comparatively simple and axisymmetric. Coils are three-dimensional and must be manufactured to very tight tolerance. This is why there are far fewer of them.
Maturity By far the most-built approach, and the basis of ITER. Fewer machines, but W7-X holds the stellarator record for triple product.

Read this before comparing. Neither has produced net electricity. Comparing them on device count measures how much has been attempted, not how well either works.

Devices in this dataset

Tokamak 72

Stellarator 12

Organisations

Tokamak 10

Commonwealth Fusion SystemsEnergy SingularityGeneral AtomicsInstitute of Plasma Physics, Chinese Academy of SciencesITER OrganizationKorea Institute of Fusion EnergyMaritime FusionMax Planck Institute for Plasma PhysicsNT-TaoUK Atomic Energy Authority

Stellarator 9

Gauss FusionHelical FusionMax Planck Institute for Plasma PhysicsNational Institute for Fusion ScienceProxima FusionRenaissance FusionStellarex EnergyThea EnergyType One Energy