Sie befinden Sich nicht im Netzwerk der Universität Paderborn. Der Zugriff auf elektronische Ressourcen ist gegebenenfalls nur via VPN oder Shibboleth (DFN-AAI) möglich. mehr Informationen...
Overview of first Wendelstein 7-X high-performance operation
Ist Teil von
Nuclear fusion, 2019-11, Vol.59 (11), p.112004
Erscheinungsjahr
2019
Beschreibungen/Notizen
Abstract
The optimized superconducting stellarator device Wendelstein 7-X (with major radius
, minor radius
, and
plasma volume) restarted operation after the assembly of a graphite heat shield and 10 inertially cooled island divertor modules. This paper reports on the results from the first high-performance plasma operation. Glow discharge conditioning and ECRH conditioning discharges in helium turned out to be important for density and edge radiation control. Plasma densities of
with central electron temperatures
were routinely achieved with hydrogen gas fueling, frequently terminated by a radiative collapse. In a first stage, plasma densities up to
were reached with hydrogen pellet injection and helium gas fueling. Here, the ions are indirectly heated, and at a central density of
a temperature of
with
was transiently accomplished, which corresponds to
with a peak diamagnetic energy of
and volume-averaged normalized plasma pressure
. The routine access to high plasma densities was opened with boronization of the first wall. After boronization, the oxygen impurity content was reduced by a factor of 10, the carbon impurity content by a factor of 5. The reduced (edge) plasma radiation level gives routinely access to higher densities without radiation collapse, e.g. well above
line integrated density and
central temperatures at moderate ECRH power. Both X2 and O2 mode ECRH schemes were successfully applied. Core turbulence was measured with a phase contrast imaging diagnostic and suppression of turbulence during pellet injection was observed.