Exploitation of Wendelstein 7-X

Wendelstein 7-X is an experimental stellarator device built in Greifswald, Germany, at the Max Planck Institute of Plasma Physics, and completed in October 2015. It is based on a five field-period Helias configuration. It is mainly a toroid, consisting of 50 non-planar and 20 planar superconducting magnetic coils, 3.5 m high. The 50 non-planar coils are used for adjusting the magnetic field. It aims for a plasma density of 3×1020 particles per cubic metre, and a plasma temperature of 60–130 megakelvin.

The purpose of W7-X is to advance stellarator technology and to evaluate the main components of a future fusion power plant. As of 2016, Wendelstein 7-X was the largest stellarator device in the world. It has been anticipated to achieve operations of up to 30 minutes of continuous plasma discharge, thus demonstrating an essential feature of a future fusion power plant: continuous operation.

W7-X is a key element of the European Fusion Roadmap. As a EUROfusion partner, the National Fusion Laboratory participates in the exploitation of W7-X in several ways: initially through specific theoretical derivations, and by means of the design and commissioning of diagnostics such as the double Doppler reflectometer; later, by conducting or coordinating experiments in which these theories and diagnostics will play a central role.

Three of the main results have been reported in the following papers:

These works validate the optimization of W7-X with respect to neoclassical energy transport and minimization of the bootstrap current. A study on energetic ion transport can be found in

Particle transport has been found to be turbulent, thus mitigating the predicted problem of core depletion:

An overview of theoretical expectations published in the literature and of modelling capabilities of the W7-X team, with respect to impurity transport, can be found in:

Related work can be found in:

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