Speaker
Christoph Biedermann
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1023.pdf
Signatures of the magnetic configuration observed with the video diagnostic
at Wendelstein 7-X stellarator
C. Biedermann1, G. Cseh2, G. Kocsis2, T. Szepesi2, M. Otte1
and the W7-X Team
1
Max-Planck-Institute for Plasma Physics, Greifswald, Germany
2
Wigner RCP RMI, Budapest, Hungary
Wendelstein W7-X is a highly optimized stellarator experiment with a modular
superconductive coil system operating at a magnetic field of 2.5 T. Commissioning started in
2015 with plasmas up to 20s. W7-X is stepwise upgraded: beginning from uncooled fine-grain
graphite limiters, then installing uncooled divertor units, and finally implementing actively
water-cooled high-heat flux divertor structures made of graphite. At W7-X the island divertor
concept is applied, with intrinsic island chains at the plasma edge producing multiple X-points
directing the out flowing plasma in the scrape-off layer to dedicated target plates of the divertor.
To verify the magnetic field configuration and measure magnetic field errors, which cause
asymmetries in the heat flux to the island-divertor, a set of 10 1.3MPixel-CMOS cameras has
been installed [1]. These cameras give a toroidal overview of the magnetic field lines and flux
surfaces visualized by an adjustable electron gun and a fluorescent rod [2] and further of the
light emission from the edge plasma in the visible spectral range. The main objective of the
video diagnostic is to visualize plasma shape, position as well as plasma-wall interaction during
the discharge operation for supervision and scientific exploration. During the first operational
phase with the uncooled divertor unit a variety of magnetic configurations have been executed
and the emission of visible light during extensive external as well as intrinsic gas fuelling was
observed. To help the understanding of the recorded radiation distributions a synthetic
diagnostic including the viewing geometry of different magnetic field configurations has been
developed. The set of 10 camera channels with Event Detection Intelligent Camera (EDICAM)
sensors allows coverage of the whole torus interior and visualization of the island structure. In
this contribution we present an overview of the camera system and capabilities and summarize
the observed signatures of the different magnetic field configurations.
[1] G. Kocsis et al. Fusion Engineering and Design 96-97 (2015) 808.
[2] M. Otte et al. Plasma Phys. Contr. Fusion 58 (2016) 064003.
