Magnetic configuration effects on the Wendelstein 7-X stellarator
A. Dinklage , C. D. Beidler , P. Helander , G. Fuchert , H. Maaßberg , K. Rahbarnia , T. Sunn Pedersen , Y. Turkin , R. C. Wolf , A. Alonso , T. Andreeva , B. Blackwell , S. Bozhenkov , B. Buttenschön , A. Czarnecka , F. Effenberg , Y. Feng , J. Geiger , M. Hirsch , U. Höfel , M. Jakubowski , T. Klinger , J. Knauer , G. Kocsis , A. Krämer-Flecken , M. Kubkowska , A. Langenberg , H. P. Laqua , N. Marushchenko , A. Mollén , U. Neuner , Heinrich Niemann , E. Pasch , N. Pablant , L. Rudischhauser , J. D. H. Smith , O. Schmitz , T. Stange , T. Szepesi , G. Weir , T. Windisch , G. A. Wurden , Dan Zhang , Łukasz Ciupiński , Grzegorz Krzesiński , Piotr Marek
AbstractThe two leading concepts for confining high-temperature fusion plasmas are the tokamak and the stellarator. Tokamaks are rotationally symmetric and use a large plasma current to achieve confinement, whereas stellarators are non-axisymmetric and employ three-dimensionally shaped magnetic field coils to twist the field and confine the plasma. As a result, the magnetic field of a stellarator needs to be carefully designed to minimize the collisional transport arising from poorly confined particle orbits, which would otherwise cause excessive power losses at high plasma temperatures. In addition, this type of transport leads to the appearance of a net toroidal plasma current, the so-called bootstrap current. Here, we analyse results from the first experimental campaign of the Wendelstein 7-X stellarator, showing that its magnetic-field design allows good control of bootstrap currents and collisional transport. The energy confinement time is among the best ever achieved in stellarators, both in absolute figures (τE > 100 ms) and relative to the stellarator confinement scaling. The bootstrap current responds as predicted to changes in the magnetic mirror ratio. These initial experiments confirm several theoretically predicted properties of Wendelstein 7-X plasmas, and already indicate consistency with optimization measures.
|Total number of authors||372|
|Journal series||Nature Physics, ISSN 1745-2473|
|Publication size in sheets||0.5|
|Keywords in English||Collisional plasmas, Magnetic mirrors, Magnetohydrodynamics, Plasma collision processes, Stellarators|
|Score||= 45.0, 06-07-2020, ArticleFromJournal|
|Publication indicators||= 41; = 42; = 56.0; : 2017 = 5.975; : 2018 = 20.113 (2) - 2018=21.797 (5)|
|Citation count*||56 (2020-07-03)|
* presented citation count is obtained through Internet information analysis and it is close to the number calculated by the Publish or Perish system.