Wendelstein 7-AS
MW | |
Discharge duration | up to 2 s |
---|---|
History | |
Year(s) of operation | 1988–2002 |
Succeeded by | Wendelstein 7-X |
Wendelstein 7-AS (abbreviated W7-AS, for "Advanced Stellarator") was an experimental
The experiment was succeeded by Wendelstein 7-X, which began construction in Greifswald in 2002, was completed in 2014 and started operation in December 2015. The goal of its successor is to investigate the suitability of components designed for a future fusion reactor.[3]
Experimental design
Wendelstein 7-AS was a
Wendelstein 7-AS was the first in a series of IPP stellarator experiments
Technical specifications
Property | Value |
---|---|
Major radius | 2 m |
Minor radius | 0.13 to 0.18 m |
Magnetic field | up to 2.6 Tesla (≈ 500,000 times Earth's magnetic field in Europe) |
Number of toroidal coils | 45 modular, non-flat coils + 10 flat additional coils |
Plasma duration | up to 2 seconds |
Plasma heating | 5.3 megawatts (2.6 MW microwaves + 2.8 MW neutral particle injection) |
Plasma volume | ≈ 1 cubic meter |
Amount of plasma | <1 milligram |
Electron temperature | up to 78 million K = 6.8 keV |
Ion temperature (hydrogen) | up to 20 million K = 1.7 keV (slightly more than the temperature in the center of the Sun) |
Project results
The following experimental results confirmed the predictions of a partially optimized Wendelstein 7-AS and led to the development and construction of the Wendelstein 7-X:[8]
- The magnetic field was able to trap plasma particles (mostly hydrogen ions and electrons) with higher thermal energies than its predecessors. This improvement made it possible to reach temperatures eight times higher than the internal temperature of the Sun (inside the plasma ring for electrons), and slightly more (internal temperature of the Sun) for hydrogen ions.
- Furthermore, it was shown that the partially optimized stellarator behaves extraordinarily "good-natured" with regard to plasma instabilities, which is of great importance for the continuous operation of a future reactor. Instabilities can lead to temporary cooling or the loss of hot plasma particles and thus reduce the plasma pressure and temperatures inside the vessel.
- A so-called island divertor was successfully operated on the Wendelstein 7-AS – the first time on a stellarator; this removes contaminants from the plasma that would additionally cool the hot plasma inside. For this purpose, the magnetic field lines at the edge of the plasma were deformed in such a way that multi-charged ions of the hot plasma hit targeted baffle plates and distribute their energy as cheaply as possible, thereby avoiding local overheating.[9][10]
- The Wendelstein 7-AS was the first stellarator access the H-mode(H for "high confinement"), which was previously only accessible to tokamaks. This allows it to easily achieve ignition conditions of a fusion reactor as the plasma is able to develop an insulating layer a few centimeters thick from the edge of the machine, allowing for higher temperatures inside.
References
- S2CID 250858130.
- ^ S2CID 118508232.
- ^ Clery, Daniel (2015-10-21). "The bizarre reactor that might save nuclear fusion". Science | AAAS. Retrieved 2020-06-16.
- S2CID 250832456.
- S2CID 121149986.
- ^ Renner, H. (1988). "Experimental programme of W VII-AS and projections to W VII-X". Proceedings of the Workshop on Wendelstein VII-X. 20 (18) – via International Nuclear Information System.
- S2CID 110058999.)
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: CS1 maint: numeric names: authors list (link - ISSN 1070-664X.
- S2CID 250801192.
- ISSN 0022-3115.