Fast-camera imaging on the W7-X stellarator

Fast cameras recording in the visible range have been used to study filamentary (``blob'') edge turbulence in tokamak plasmas, revealing that emissive filaments aligned with the magnetic field can propagate perpendicular to it at speeds on the order of 1 km/s in the SOL or private flux region. The motion of these filaments has been studied in several tokamaks, including MAST, NSTX, and Alcator C-Mod. Filaments were also observed in the W7-X Stellarator using fast cameras during its initial run campaign [1]. For W7-X's upcoming 2017--18 run campaign, we have installed a Phantom V710 fast camera with a view of the the machine cross section and part of a divertor module in order to continue studying edge and divertor filaments. The view is coupled to the camera via a coherent fiber bundle. The Phantom camera is able to record at up to 400,000 frames per second and has a spatial resolution of roughly 2 cm in the view. A beam-splitter is used to share the view with a slower machine-protection camera. Stepping-motor actuators tilt the beam-splitter about two orthogonal axes, making it possible to frame user-defined sub-regions anywhere within the view. The diagnostic has been prepared to be remotely controlled via MDSplus. [1] G. Kocsis et al., 44th EPS Conf. (2017).