Wendelstein 7-X is an experimental stellarator (nuclear fusion reactor) currently being built in Greifswald, Germany by the Max-Planck-Institut für Plasmaphysik (IPP), which will be completed by 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.
Wendelstein 7-X, when finished, will be the largest fusion device created using the stellarator concept. 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 research facility is an independent partner project with the University of Greifswald.
Design and main components
Wendelstein 7-X 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 carry away 5,000 watts of heating power 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 5 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).
Its completion originally expected in 2006, an eight-year schedule slip pushed this date out to 2014. After a period of vessel leak-checking, beginning in the summer of 2014, the cryostat will be put under vacuum, and magnet testing will begin in the fall of 2014. The first plasma tests are scheduled to begin during operational phase 1 (OP-1) in spring 2015.   On 16 November 2011, the last module of the stellarator's cryostat was lifted into place.  A three-lab American consortium (Princeton, Oak Ridge, and Los Alamos) is also now a partner in the project.  Recently, Princeton University and the Max Planck Society announced a new joint research center in plasma physics, which also will include research on the W7-X stellarator.
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