A Gas-Puff-Imaging (GPI) diagnostic is being designed for use on the W7-X Stellarator. It will allow for detailed study of boundary and scrape-off-layer physics during the long-pulse W7-X operation period OP 2. GPI requires an in-vessel nozzle close to the plasma, through which non-perturbing amounts of H2 or He gas are puffed; a re-entrant view of the puff, ideally along local field lines; and an optical system that relays the imaged emission to a fast 2D detector. This must be done in the harsh long-pulse environment, where re-entrant hardware must be actively cooled and collecting optics shuttered. We have prepared a design for viewing a roughly 50 x 70 mm region at the plasma boundary with spatial resolution of ~5 mm and time resolution of ~1 ?sec. We propose to puff the gas through 4 converging-diverging nozzle apertures in order to collimate the gas cloud. We have performed finite-element analysis of fluid flow down the feed tube and through the nozzles. We have modeled the puff emission using DEGAS 2. We have designed a water-cooled re-entrant tube to hold the light collection optics and modeled the optics to attain sufficient resolution and light throughput. The details of the design and modeling will be shown.
Design of a Gas-Puff Imaging Diagnostic for W7-X
Scarin P;
2018
Abstract
A Gas-Puff-Imaging (GPI) diagnostic is being designed for use on the W7-X Stellarator. It will allow for detailed study of boundary and scrape-off-layer physics during the long-pulse W7-X operation period OP 2. GPI requires an in-vessel nozzle close to the plasma, through which non-perturbing amounts of H2 or He gas are puffed; a re-entrant view of the puff, ideally along local field lines; and an optical system that relays the imaged emission to a fast 2D detector. This must be done in the harsh long-pulse environment, where re-entrant hardware must be actively cooled and collecting optics shuttered. We have prepared a design for viewing a roughly 50 x 70 mm region at the plasma boundary with spatial resolution of ~5 mm and time resolution of ~1 ?sec. We propose to puff the gas through 4 converging-diverging nozzle apertures in order to collimate the gas cloud. We have performed finite-element analysis of fluid flow down the feed tube and through the nozzles. We have modeled the puff emission using DEGAS 2. We have designed a water-cooled re-entrant tube to hold the light collection optics and modeled the optics to attain sufficient resolution and light throughput. The details of the design and modeling will be shown.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
