The Superconducting Magnet System for the Wendelstein 7-X Stellarator

The WENDELSTEIN 7-X Stellarator, construction of which is about to start at the IPP, is a further experiment in the small group of next-step fusion devices in the world. An essential goal of this machine is to demonstrate concept improvement towards the development of fusion devices. The magent system is designed for optimum stellarator plasma performance and the technical layout will allow steady-state plasma operation - an intrinsic property of stellarators. Consequently, the coil system is superconducting. The main technical parameters are: major radius R_o = 5.5 m, magnetic induction B_o = 3 T, stored magnetic energy W_m = 600 MJ, average plasma radius r_o = 0.53 m. The magnet system comprises 50 nonplanar coils, modularly arranged in five periods. Twenty additional ancillary planar coils are arranged around the modular system. These coils serve only to provide experimental flexibility and, consequently, will not be necessary for a power producing fusion device.