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The aim of fusion research is to reproduce on earth how energy is produced by the sun: a fusion power plant is to derive energy from fusion of atomic nuclei. The fuel needed is an ionised, extremely low-density hydrogen gas, called plasma. To ignite the fusion fire the plasma has to be confined in magnetic fields and heated to temperatures of over 100 million degrees.
In fusion experiments of the stellarator type the plasma is confined by magnetic fields generated by magnet coils outside the plasma region. In contrast, most of the fusion experiments now being conducted throughout the world are of the tokamak type, these producing part of the field with a high electric current flowing in the plasma. The stellarator principle, however, promises advantages where tokamaks have drawbacks. For example, stellarators are suitable for continuous operation, whereas tokamaks without auxiliary facilities can only operate in pulsed mode. Stellarators may thus be the superior solution for a fusion power plant.
The Wendelstein 7-X experiment will be concerned with testing a special construction principle for the magnetic field cage. The core of the experiment is the coil system comprising 50 superconducting magnet coils. Their bizarre shapes are the result of elaborate optimisation calculations: they are to produce a particularly stable and thermally insulating magnetic cage for the plasma. By this means Wendelstein 7-X is to demonstrate the stellarator’s essential property, viz. continuous operation. All coils are accommodated in a common cryostat cooled with liquid helium to superconduction temperatures of 4 kelvin. The magnetic field cage produced is to confine a plasma providing convincing evidence of the power plant properties of stellarators without actually generating energy. Information on the behaviour of a burning plasma is to be provided instead by the ITER international experimental tokamak reactor now being prepared as a world-wide cooperation for construction at Cadarache, France.
The Wendelstein 7-X project is funded by the European Union, the German Federal Government and the state of Mecklenburg-Vorpommern. The manufacture of essential components, in particular the superconducting magnet coils and the plasma vessel, is complete. Modular assembly of the device on the installation rigs is now in progress. Besides the basic machine itself, the facilities for heating the plasma, the cryogenic unit for cooling the coils with liquid helium, the control system, the power supply and diverse measuring instruments have likewise to be set up. The microwave heating system is being provided by Forschungszentrum Karlsruhe; Forschungszentrum Jülich is also involved, e.g. in the development of measuring facilities. Numerous other research establishments throughout Europe are contributing to the construction work. Wendelstein 7-X is to go into operation in 2014.
Project website: www.ipp.mpg.de/ippcms/eng/for/projekte/w7x/
Contact
Prof. Dr. Robert Wolf – spokesman for the Greifswald branch of IPP
Max-Planck-Institut für Plasmaphysik (IPP)
Greifswald Branch
Phone: +49 3834 88-1205
Fax: +49 3834 88-2509
E-Mail: robert.wolf [at] ipp.mpg.de
Antje Lorenz
Event and visitor service
Max-Planck-Institut für Plasmaphysik (IPP)
Greifswald Branch
Phone: +49 3834 88-2614
Fax: +49 3834 88-2009
E-Mail: antje.lorenz [at] ipp.mpg.de
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Stellarator Wendelstein 7-X building, on the left side: the experiment hall - CC - Bernd vdB
Stellarator Wendelstein 7-X, Four out of the five modules on the machine basement, photo: Riemann
Deuterium-tritium fusion diagram - Source: www.wikimedia.org
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