Experiences from design and production of Wendelstein 7-X magnets

Abstract

The Max-Planck-Institut für Plasmaphysik in Greifswald is building the stellarator fusion experiment Wendelstein 7-X (W7-X). The manufacturing of the W7-X superconducting magnet system, which consists of 50 non-planar and 20 planar coils, was finished in March 2008. The production was a technical challenge for the W7-X design crew as well for the manufacturer due to the complex 3 D shape of the non-planar coils and the stringent requirements for geometrical tolerances. The manufacturers had to solve several technical problems and to consider major design changes even at advanced stages of manufacture. Finally the coils are passing the acceptance tests at cryogenic temperatures at CEA Saclay with a very good performance. Results of the W7-X coil production will be given and critical production steps will be identified. Lessons will be taken from the experiences gained from design, manufacturing and test methods. The reasons for the considerable time delays will be explained.

New method to design stellarator coils without the winding surface

“…This problem remains crucial, as is evidenced by the recent NCSX [1] stellarator, which was partially built at Princeton Plasma Physics Laboratory but, because of budget constraints, was ultimately cancelled; and by the construction delays of the W7-X experiment [2] recently completed in Germany. The construction of the coils is only one component of modern experiments; but, realizing that it is the currents in the coils that produce the "magnetic bottle" that confines the plasma, it is easy to understand that designing and accurately constructing suitable coils is paramount.…”

Constrained stellarator coil curvature optimization with FOCUS

“…Non-planar coils complicate coil design, engineering, assembly and supports. Difficulties arising from non-planar coils led to significant delays during the construction of the W7-X experiment (Riße 2009) and to the cancellation of the NCSX experiment at the Princeton Plasma Physics Laboratory (Neilson et al 2010).…”

Optimization of finite-build stellarator coils

“…However, unlike tokamak devices that rely on both planar coils and large plasma current to provide rotational transform, optimized stellarators generally possess three-dimensional non-planar coils in order to generate adequate confinement. Difficulties constructing coils led to significant delays in the W7-X experiment (Riße et al 2009) and the cancellation of the NCSX experiment at PPPL (Neilson et al 2010).…”