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. The modular coils allow to optimize the magnetic field of Wendelstein 7-X to overcome the difficulties of previous classical stellarators. The quality of plasma equilibrium and confinement is expected to be comparable to that of a tokamak, however, avoiding the disadvantages of a large current in the plasma. The assembly of Wendelstein 7-X will be completed in 2014.
The design of Wendelstein 7-X also bases on its predecessor experiment Wendelstein 7-AS operated at IPP in Garching from 1988 to 2002. Wendelstein 7-AS was the first experiment of the new generation of "Advanced Stellarators" using modular field coils to prove some basic elements of stellarator optimization. Its successful operation laid the ground to build fully optimized stellarators such as Wendelstein 7-X.