|Major radius||5.5 m|
|Minor Radius||0.53 m|
|Plasma volume||30 m3|
|Magnetic field||3 T|
The Wendelstein 7-X reactor is an experimental stellarator (nuclear fusion reactor) built in Greifswald, Germany, by the Max-Planck-Institut für Plasmaphysik (IPP), and completed in October 2015. It is a further development of Wendelstein 7-AS. The purpose of Wendelstein 7-X is to evaluate the main components of a future fusion reactor built using stellarator technology, even if Wendelstein 7-X itself is not an economical fusion power plant.
The Wendelstein 7-X reactor is the largest fusion device created using the stellarator concept which was the brainchild of physicist Lyman Spitzer. It is planned to operate with up to 30 minutes of continuous plasma discharge, demonstrating an essential feature of a future power plant: continuous operation.
The name of the project, referring to the mountain Wendelstein in Bavaria, was decided at the end of the 1950s, referencing the preceding project from Princeton University under the name Matterhorn.
The research facility is an independent partner project with the University of Greifswald.
Design and main components
The Wendelstein 7-X device is based on a five field-period Helias configuration. It is mainly a toroid, consisting of 50 non-planar and 20 planar superconducting magnetic coils, 3.5 m high, which induce a magnetic field that prevents the plasma from colliding with the reactor walls. The 50 non-planar coils are used for adjusting the magnetic field.
The main components are the magnetic coils, cryostat, plasma vessel, divertor and heating systems.
The coils are arranged around a heat insulating cladding which is 16 meters in diameter called the cryostat. A cooling device produces enough liquid helium to cool down the magnets and their enclosure (about 425 metric tons) to superconductivity temperature. The plasma vessel, built of 20 parts, is on the inside, adjusted to the complex shape of the magnetic field. It has 299 holes for plasma heating and observation diagnostics. The whole plant is built of five almost identical modules, which are assembled in the experiment hall.
The heating system includes 10 megawatts of microwaves, for up to 10 seconds, and can deliver 1 megawatt for 50 seconds during operational phase 1 (OP-1). For operational phase 2 (OP-2), after completion of the full armor/water-cooling, up to 8 megawatts of neutral beam injection will also be available for 10 seconds, while the microwave system will be extended to true steady state (30 minutes).
In 2012, Princeton University and the Max Planck Society announced a new joint research center in plasma physics, to include research on W7-X.
The end of the construction phase was officially marked by an inauguration ceremony on 20 May 2014. After a period of vessel leak-checking, beginning in the summer of 2014, the cryostat was put under vacuum, and magnet testing was completed in July 2015.
The first plasma tests were scheduled to begin during operational phase 1 (OP-1) in late 2015. A three-lab American consortium (Princeton, Oak Ridge, and Los Alamos) became a partner in the project, paying 7.5 million Euros of the projected total cost of 1.06 billion Euros.
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