Wendelstein 7-X is an experimental stellarator device built in Greifswald, Germany, by 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, which induce a magnetic field that prevents the plasma from colliding with the reactor walls. 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 approximately in 2021, thus demonstrating an essential feature of a future fusion power plant: continuous operation.
W7-X is the key element of Mission 8 (“Stellarators”) of the European Fusion Roadmap. As 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.
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:
- Impurity transport modelling. Overview in the Wendelstein 7-X OP1.2b Program Workshop, Greifswald, Germany, 2018.
Examples of theory-driven experimental proposals can be found in:
- Neoclassical confinement modes. TFIII.1 meeting (neoclassical transport and optimization),Greifswald, Germany, 2017.
- Plasmas close to impurity temperature screening. TFIII.3 meeting (impurity transport),Greifswald, Germany, 2016.
- A quick note on Core Electron Root Confinement. S1 Task Force Meeting, Greifswald, Germany, 2015.
Related work can be found in:
- A Dinklage and the W7-X Team. Magnetic configuration effects on the Wendelstein 7-X stellarator. Nature Physics, 14(8):855–860, 2018. PDF
- N. A. Pablant, A. Langenberg, A. Alonso, C. D. Beidler, M. Bitter, S. Bozhenkov, R. Burhenn, M. Beurskens, L. Delgado-Aparicio, A. Dinklage, G. Fuchert, D. Gates, J. Geiger, K. W. Hill, U. Höfel, M. Hirsch, J. Knauer, A. Krämer-Flecken, M. Landre- man, S. Lazerson, H. Maaßberg, O. Marchuk, S. Massidda, G. H. Neilson, E. Pasch, S. Satake, J. Svennson, P. Traverso, Y. Turkin, P. Valson, J. L. Velasco, G. Weir, T. Windisch, R. C. Wolf, M. Yokoyama, D. Zhang, and W7-X Team. Core radial electric field and transport in Wendelstein 7-X plasmas. Physics of Plasmas, 25(2):022508, 2018. PDF
- T Windisch, A Krämer-Flecken, JL Velasco, A Könies, C Nührenberg, O Grulke, T Klinger, and the W7-X team. Poloidal correlation reflectometry at w7-x: ra- dial electric field and coherent fluctuations. Plasma Physics and Controlled Fusion, 59(10):105002, 2017. PDF
- T Klinger, A Alonso, S Bozhenkov, R Burhenn, A Dinklage, G Fuchert, J Geiger, O Grulke, A Langenberg, M Hirsch, G Kocsis, J Knauer, A Krämer-Flecken, H Laqua, S Lazerson, M Landreman, H Maaßberg, S Marsen, M Otte, N Pablant, E Pasch, K Rahbarnia, T Stange, T Szepesi, H Thomsen, P Traverso, J L Velasco, T Wauters, G Weir, T Windisch, and The Wendelstein 7-X Team. Performance and properties of the first plasmas of wendelstein 7-x. Plasma Physics and Controlled Fusion, 59(1):014018, 2017. PDF
- A Krämer-Flecken, T Windisch, W Behr, G Czymek, P Drews, G Fuchert, J Geiger, O Grulke, M Hirsch, M Knaup, Y Liang, O Neubauer, E Pasch, J L Velasco, and the W7-X Team. Investigation of turbulence rotation in limiter plasmas at w7-x with newly installed poloidal correlation reflectometer. Nuclear Fusion, 57(6):066023, 2017. PDF
- T Sunn Pedersen et al.. Confirmation of the topology of the Wendelstein 7-X magnetic field to better than 1:100,000 Nature Communications, 7:13493, 2016. PDF
- R C Wolf et al.. Major results from the first plasma campaign of the Wendelstein 7-X stellarator. Nuclear Fusion, 57(10):102020, 2017. PDF