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A stellarator is a magnetic confinement device. The rotational transform is predominantly generated by external coils - as opposed to a tokamak, in which the poloidal field is generated by plasma currents. Hybrid concepts (including the concepts known as quasi-axisymmetry and quasi-omnigeneity) employ both external coils and self-generated (bootstrap) currents (e.g. NCSX).

NCSX plasma vessel.

Classification of stellarators

Somewhat arbitrarily, stellarators may be classified according to the type of magnetic configuration.

  • Torsatron / Heliotron: the rotational transform is produced by an external helical coil surrounding the plasma.
  • Heliac: a stellarator with a toroidally helical magnetic axis.
  • Helias: advanced stellarator with modular coils.

Defunct stellarators

  • ATF (Oak Ridge, TN, USA)
  • CHS (Japan)
  • H-1NF (Canberra, Australia)
  • NCSX (Princeton, NJ, USA) - cancelled before construction was completed
  • W7-AS (Garching, Germany, 1988-2002)

Operational stellarators

Future stellarators

  • QPS (in design phase, TN, USA)
  • STELL (in design phase, University of Lorraine, France, in collaboration with IPP Greifswald)

See also