Wendelstein 7-X is the German device at the Max Planck Institute for Plasma Physics in Greifswald that is the world's largest and most advanced 📝stellarator, built to prove that computationally optimized stellarator physics works.
The near-neighbor distinction is with the 📝Tokamak. A tokamak twists its confining magnetic field partly with a large current driven through the 📝plasma itself — a current that must be sustained and that can disrupt. A stellarator produces the entire twisted field with shaped external coils: no 📝plasma current, no disruptions, and inherently 📝steady-state operation. The historical cost was worse confinement, because early stellarators leaked particles through their imperfect three-dimensional fields. Wendelstein 7-X exists to close that gap: its fifty superconducting non-planar coils, each individually sculpted, realize a magnetic geometry numerically optimized in the 1980s and 1990s to suppress the 📝neoclassical transport that plagued its predecessors.
The machine produced first plasma in December 2015, and its results have largely vindicated the optimization: measured neoclassical transport is reduced as designed, and with an actively cooled 📝divertor installed it has sustained high-performance plasmas for minutes at a time, with gigajoule-scale total energy turnover in a single discharge. Named for a peak in the Bavarian Alps, continuing a line begun at Garching in the 1950s, Wendelstein 7-X is not designed to produce net 📝fusion power; it is the physics case for the stellarator as a power-plant candidate — the leading alternative should the tokamak's instabilities prove intractable.