Physics / mechanism
Stellarators confine plasma in a twisted, non-axisymmetric magnetic field generated entirely by external coils — no net toroidal current required. The field topology is shaped via helical or modular coils to cancel neoclassical transport losses. Key parameters: energy confinement time (τ_E), plasma beta (ratio of plasma to magnetic pressure), and ion temperature. Wendelstein 7-X (W7-X, IPP Greifswald) is the current SoA: optimised for quasi-isodynamic configuration, achieved ~8 minutes of steady-state plasma at ~20 MW heating power, ion temperatures exceeding 40 million K, and confinement competitive with mid-scale tokamaks. No disruption risk — structurally the central differentiator versus tokamaks.
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