Stellarator

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)
• NCSX (Princeton, NJ, USA) - cancelled before construction was completed
• W7-AS (Garching, Germany, 1988-2002)

Operational stellarators

• CAT/CTH (Auburn, USA)
• H-1NF (Canberra, Australia)
• Heliotron-J (Kyoto, Japan)
• HSX (Madison, WI, USA)
• LHD (Toki, Japan)
• TJ-II (Madrid, Spain)
• TJ-K (Stuttgart, Germany)
• TU Heliac (Tohoku Univ., Sendai, Japan)
• UST-1 (Spain) - tabletop experiment
• WEGA (Greifswald, Germany)
• W7-X (Greifswald, Germany)

Future stellarators

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

See also

• Stellarator reactor
• Stellarator optimization
• International Stellarator and Heliotron Workshop
• Coordinated Working Group Meeting
• Stellarator symmetry
• Stellarator News
• ARIES Project (conceptual design of a compact stellarator)
• Spherical Stellarator design study

References

• M. Wakatani, Stellarator and Heliotron devices, Oxford University Press, New York and Oxford (1998) ISBN 0-19-507831-4
• P. Helander, Theory of plasma confinement in non-axisymmetric magnetic fields, Rep. Prog. Phys. 77 (2014) 087001