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.
The goal of fusion research is to produce energy in a roughly similar fashion as the Sun. To ignite the fusion in a stellarator, the plasma must be confined by magnetic fields and heated to 100 million kelvin; this is not quite the same as what happens inside the Sun, which confines its plasma mainly by gravity and ignites it through extreme pressure rather than extreme temperatures (the Sun is very hot at its core, but is estimated to be at "only" 15 million kelvin rather than 100 million); however, the gravity of the Sun cannot be created artificially on Earth, and very high temperatures are considerably easier to create on Earth than very high pressures.
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.
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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.
Its completion originally expected in 2006, an 8-year schedule slip pushed this date out to 2014. [1] [2] On 16 November, 2011, the last module of the stellarator's cryostat was lifted into place. [3]
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