Physics and Engineering Design for Wendelstein VII-X

TLDR

Wendelstein VII‑X is a forthcoming stellarator experiment at the Max‑Planck Institute that aims to reach >5 keV plasma temperatures through combined neoclassical and anomalous transport, while studies show comparable radial and lateral forces in its superconducting coils. The experiment seeks to advance modular stellarator development, demonstrate reactor‑scale capability, and achieve quasi‑steady‑state operation above 5 keV. W VII‑X employs a Helias helical advanced stellarator with five field periods, 20 MW heating, and a 3 T magnetic field (R₀ = 6.5 m, a = 0.65 m, stored energy ≈0.88 GJ) using superconducting coils, with stress analysis accounting for comparable radial and lateral forces and ongoing studies of complex engineering challenges.

Abstract

AbstractThe future experiment Wendelstein VII-X (W VII-X) is being developed at the Max-Planck-Institut für Plasmaphysik. A Helical Advanced Stellarator (Helias) configuration has been chosen because of its confinement and stability properties. The goals of W VII-X are to continue the development of the modular stellarator, to demonstrate the reactor capability of this stellarator line, and to achieve quasi-steady-state operation in a temperature regime >5 keV. This temperature regime can be reached in W VII-X if neoclassical transport plus the anomalous transport found in W VII-A prevail. A heating power of 20 MW will be applied to reach the reactor-relevant parameter regime.The magnetic field in W VII-X has five field periods. Other basic data are as follows: major radius R0 = 6.5 m, magnetic induction B0 = 3 T, stored magnetic energy W ≈ 0.88 GJ, and average plasma radius a = 0.65 m. Superconducting coils are favored because of their steady-state field, but pulsed water-cooled copper coils are also being investigated.Unlike planar circular magnetic field coils, which experience only a radially directed force, twisted coils are subject to a lateral force component as well. Studies of various superconducting coil systems for Helias configurations have shown that the magnitudes of these radial and lateral force components are comparable. Based on a support model, the mechanical stresses are calculated; all components of the stress tensor are of equal importance. Other studies being conducted are concerned with the many complex engineering aspects presented by the construction of nonplanar superconducting coils.