Wendelstein 7-A

Wendelstein 7-A
Device type	Stellarator
Location	Garching, Germany
Affiliation	Max Planck Institute for Plasma Physics
Technical specifications
Major radius	2 m (6 ft 7 in)
Minor radius	0.12 m (4.7 in)
Plasma volume	0.6 m3
Magnetic field	3.4 T (34,000 G)
Heating power	2.9 MW
Plasma current	0-45 kA
Plasma temperature	<1.5 keV
Plasma density	1×1020 m3
History
Year(s) of operation	1975–1985
Preceded by	Wendelstein II-B
Succeeded by	Wendelstein 7-AS
Links
Website	https://www.ipp.mpg.de/3951949/wendelstein7a

Wendelstein 7-A was a stellarator operated between 1975 and 1985 at the Max Planck Institute for Plasma Physics. In 1980 the stellarator showed that it could confine plasma fusion fuel, necessary for fusion power by magnetic confinement, without a current in the plasma. This was a major result because the current could drive various plasma instabilities, and was also inherent to the operation of the main competing device type, the tokamak. When plasma current was reduced below 5 kA, the entire class of magnetohydrodynamic instabilities was no longer observed.^[1]^[2]

Wendelstein 7-A was a circular classical stellarator, with two pairs of helical electromagnetic coils to produce the stellarator magnetic field,^[3] and five field periods around the torus. One key feature of the new stellarator was the addition of neutral beam injection for heating the plasma. This enabled zero current operation because earlier heating systems, particularly Ohmic heating, created a plasma current as an inherent part of the heating process, even if it was not desired by the experiment operators.^[2]^[4]

The experiment gave a major boost to the stellarator line^[1], and was cited by pre-eminent plasma physicist Vitaly Shafranov in concluding in 1980 that, "there is no doubt: plasma can be confined in stellarators no less satisfactorily and possibly even more satisfactorily than in tokamaks".^[5]

It was succeeded at the Max Planck Institute by the considerably developed Wendelstein 7-AS stellarator, with modular coils enabling numerical optimization of the magnetic field.^[2]^[4]^[6]

References

1 2 3 4 5 6 7 8 9 "Wendelstein 7-A". Max Planck Institute for Plasma Physics. Retrieved 7 October 2026.
1 2 3 4 5 Grieger, G.; Renner, H.; Wobig, H. (1985). "Wendelstein Stellarators". Nuclear Fusion. 25 (5). doi:10.1088/0029-5515/25/9/040.
↑ Morse, E. (2018). Nuclear Fusion. Springer Nature. p. 216. doi:10.1007/978-3-319-98171-0. ISBN 9783319981703.
1 2 Reinders, L.J. (2021). The Fairy Tale of Nuclear Fusion. Cham: Springer Nature. p. 355-357. doi:10.1007/978-3-030-64344-7. ISBN 9783030643430.
↑ Shafranov, V.D. (1980). "Stellarators". Nuclear Fusion. 20 (1075). doi:10.1088/0029-5515/20/9/005.
↑ Hirsch, M.; et al. (2008). "Major results from the stellarator Wendelstein 7-AS". Plasma Phys. Control. Fusion. 50 (053001). doi:10.1088/0741-3335/50/5/053001.

[ippw7a-1] 1 2 3 4 5 6 7 8 9 "Wendelstein 7-A". Max Planck Institute for Plasma Physics. Retrieved 7 October 2026.

[grieger85-2] 1 2 3 4 5 Grieger, G.; Renner, H.; Wobig, H. (1985). "Wendelstein Stellarators". Nuclear Fusion. 25 (5). doi:10.1088/0029-5515/25/9/040.

[3] Morse, E. (2018). Nuclear Fusion. Springer Nature. p. 216. doi:10.1007/978-3-319-98171-0. ISBN 9783319981703.

[reinders-4] 1 2 Reinders, L.J. (2021). The Fairy Tale of Nuclear Fusion. Cham: Springer Nature. p. 355-357. doi:10.1007/978-3-030-64344-7. ISBN 9783030643430.

[5] Shafranov, V.D. (1980). "Stellarators". Nuclear Fusion. 20 (1075). doi:10.1088/0029-5515/20/9/005.

[6] Hirsch, M.; et al. (2008). "Major results from the stellarator Wendelstein 7-AS". Plasma Phys. Control. Fusion. 50 (053001). doi:10.1088/0741-3335/50/5/053001.

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References