Wendelstein 7-A
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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 in Wendelstein 7-A, the entire class of magnetohydrodynamic instabilities was no longer observed.[1][3]
| Wendelstein 7-A | |
|---|---|
The magnetic coil configuration of W7-A (black and red). | |
| Device type | Stellarator |
| Location | Garching, West Germany |
| Affiliation | Max Planck Institute for Plasma Physics |
| Technical specifications | |
| Major radius | 2 m (6 ft 7 in)[1] |
| Minor radius | 0.12 m (4.7 in)[1] |
| Plasma volume | 0.6 m3[1] |
| Magnetic field | 3.4 T (34,000 G)[1] |
| Heating power | 2.9 MW[1] (Ohmic heating, 200 kW ECRH, 500 kW ICRH, 1.2 MW NBI)[2] |
| Plasma current | 0-45 kA[3] |
| Plasma temperature | <1.5 keV |
| Plasma density | 1×1020 m−3[3] |
| History | |
| Year(s) of operation | 1975[1]–1985[1] |
| Preceded by | Wendelstein II-B |
| Succeeded by | Wendelstein 7-AS |
| Links | |
| Website | https://www.ipp.mpg.de/3951949/wendelstein7a |
Wendelstein 7-A was a circular classical stellarator, with two pairs of helical electromagnetic coils to produce the stellarator magnetic field,[4] 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 required for stellarator plasma confinement and not desired by the experiment operators.[3][5]
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".[6]
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.[3][5][7]
Related experiments
- Saturn-1, USSR
- CLASP, UK