Speaker
Description
A ten-channel overview video diagnostic system was installed and commissioned at
Wendelstein 7-X (W7-X) optimised stellarator. The cameras serve both for surveillance of the
first wall (ensuring safe device operation) and allow for physics studies. The wide range of
applications is ensured by a highly flexible data acquisition and on-board data processing.
Combination with magnetic field line simulations even allow to reveal 3D structures which
are relevant to the development of island divertor scenarios on W7-X.
In the second operation phase of W7-X, OP1.2a, eight channels were equipped with
EDICAMs, 1.3 Mpixel intelligent CMOS cameras and two Photron (SA5 and SX-2) 1.0
Mpixel fast CMOS cameras, observing the visible radiation emitted by the plasma. The fast
cameras can be equipped with interference filters as well; most of the measurements were
done using a C-III filter.
The supervision of the complete torus interior (typically at 100 Hz) is provided by the
EDICAMs, featuring non-destructive region-of-interest (ROI) readout capability; this feature
allows the monitoring of smaller areas in parallel to the full frame overview at much higher
rates (up to 10 kHz). The small ROIs can be used, among others, to study hot-spot evolution
(e.g. strike lines on the divertor). Video data taken by the EDICAMs is streamed through a
powerful FPGA board, suitable for real-time image processing. The user can define events,
such as light intensity thresholds to provide automatically provide trigger signals for the
plasma control system or other diagnostics, including the EDICAM system itself.
Extremely fast phenomena in the 10 microsecond timescale are observed with Photron
cameras, revealing 3D the rotation of filamentary structures. These capabilities make the
cameras a diagnostics for 3D SOL transport providing new insights in the turbulence of the
SOL plasma.
