Gas distribution measurements from a PRS nozzle

Summary form only given, as follows. Experiments are underway to characterize the argon gas flow from a supersonic z-pinch nozzle used on Phoenix. The annular nozzle has a 3.5-cm mean diameter, 13.75 degree mean inward tilt, and a 1.5-mm exit width. The gas density is measured using an ultra-sensitive, time-resolved, two-color Mach-Zehnder interferometer. The interferometer uses cw lasers of 532 and 1064 nm wavelengths. A single beam line with diameter less than 1 mm traverses the gas flow perpendicular to the nozzle axis, requiring multiple shots to build up transverse density profiles as a function of axial position. Abel inversion is used to determine the radial density profile. Shot-to-shot reproducibility is a major issue for this technique. Shots are correlated with a fast piezo-resistive pressure sensor, a flashover pin, and a valve current monitor. For a 50 /spl mu/g/cm Argon load the path-integrated density across the main part of the flow is about 2/spl times/10/sup 17/ cm/sup -2/. The interferometer system is sensitive to fringe shifts greater than 10/sup -5/ waves permitting path-integrated neutral-density measurements as small as 10/sup 14/ cm/sup -2/, allowing accurate measurements at the gas-flow edge. Possible future experiments include measuring the ionization fraction of pre-ionized gas-puffs and the electron and neutral densities in the early stages of PRS implosions.