Continued development of triple plena gas puff nozzles for Z

Summary form only given. We have previously reported on the designs of triple shell nozzles, 8 and 12 cm in diameter, for use at >;20 MA on the Z generator. Here we describe the characterization of the cold gas flow, a critical input for shot preparations on Z as well as MHD modeling of the implosions. Two types of interferometer have been used for the measurements. One, a fiber optic infrared (FOI) Mach Zehnder design has been in use for many years in our lab. A millimeter diameter beam at 1.55 micron is scanned across the nozzle diameter. The full time history of the flow is captured with a photodiode and digitizer. The puff valves must be fired many times (~150) to get 2 mm radial resolution and averaging at each position to improve signal to noise. Practical axial resolution is 10 mm. Data reduction to average shots, derive phase and then Abel-invert the data is quite time consuming. However, the use of the FOI has the benefit that the durability of the puff valve system can evaluated, optimized and ultimately demonstrated with such rigorous testing. We have also recently assembled a 2D Mach-Zehnder design using a HeNe laser at 633 nm and a low cost interline transfer 5 megapixel CCD. With only a few shots of the puff valves, full 2D maps of gas density can be derived with sub millimeter resolution in both R and Z. The field of view exceeds 8 cm in R and 4 cm in Z. The time resolution is <;20 microseconds, more than sufficient to characterize the flow once it reaches its "steady-state". Data from both interferometer systems will be compared. In addition, by using different gases in the three plena, we can derive data on the contributions of each plenum to the gas at each R,Z location.