Realization of a Gas-Puff Imaging diagnostic on W7-X

A Gas-Puff Imaging system designed to provide 2-d imaging of fluctuations on turbulence time-scales at the outboard edge of W7-X has been installed and is being commissioned for operation at the start of the next run campaign. The system will be used to study turbulence and filament dynamics in the SOL and in the magnetic islands, present as features of the island divertor configuration. Imaging of a ~78 x 38 mm region with 16 x 8 pixel resolution at ~1MHz framerates provides the capability to measure features with k_perp in the range from ~0.04 to ~5 cm^-1., with k_perp ρ_s ~0.1.The system features high-throughput light collection by re-entrant optics imaging directly onto the camera, and a pop-up turning mirror that provides sight lines to the gas-puff region that are within ~10^o of the local field lines. The novel gas-puffer features 2 vertically-stacked nozzles with “converging-diverging” cross-sections to provide improved collimation of the puffed gas. Because better collimation improves the spatial resolution and increases the chord brightnesses, careful measurements of the gas-puff cloud were made. An overview of the system, its expected capabilities, and the gas cloud measurements will be presented.