Wendelstein 7-X, under construction at the Greifswald branch of IPP, is a large stellarator with modular superconducting coils which enable steady state plasma operation in order to explore the reactor relevance of this concept.
Assembly of Wendelstein 7-X is to be concluded at the end of 2014. Once all technical systems have been checked step by step the first plasma is scheduled for 2015.
When completed, Wendelstein 7-X will be the world’s largest fusion device of the stellarator type. Its objective is to investigate the suitability of this type for a power plant. It will also test an optimised magnetic field for confining the plasma, which will be produced by a system of 50 non-planar and superconducting magnet coils, this being the technical core piece of the device.
The structure composed of single coils allows the magnetic field to be shaped in detail. A great deal of theory and computation effort was invested to optimise the magnetic field for Wendelstein 7-X so as to overcome the disadvantages of previous classical stellarators. Its predecessor, Wendelstein 7-AS (1988 - 2002), the first device of this new generation of Advanced Stellarators, had already subjected elements of the concept to first experimental testing.
The further developed successor, Wendelstein 7-X, is now to investigate the new stellarator’s suitability for a power plant. It is expected that plasma equilibrium and confinement will be of a quality comparable to that of a tokamak of the same size. But it will avoid the disadvantages of a large current flowing in a tokamak plasma: With plasma discharges lasting up to 30 minutes, Wendelstein 7-X is to demonstrate the essential stellarator property, viz. continuous operation.