Laser Induced Fluorescence Gas Puff Density Measurements
The double gas puff valve is a device used to inject a supersonic puff of gas to act as a load in z-pinch plasma implosions. The purpose of the annular gas shells is to mimic a cylindrical column along the z-axis in efforts to reduce Rayleigh-Taylor instability. However before integration of the valve into the zpinch pulsed power machine the gas profile needs to be examined. Tuning the density of the gas to fit specific profiles leads to improvement in plasma radiative sources and yields. The axial uniformity of the cylindrical gas column is highly dependent on the nozzle characteristics and shape. Performance is then determined by the density, speed, and symmetry of the gas column. Measurement of the density distribution is performed using a spectroscopic measuring technique called laser-induced fluorescence. LIF is a 1-dimensional imaging technique that maps the concentration of atoms with the aid of a tracer. LIF and the 2-dimensional counterpart planar laser-induced fluorescence (PLIF) examine the gas flow in the r-z plane with sub-millimeter resolution. The tracer molecule fluoresces due to excitation by a laser beam. The fluorescence signal is imaged using a streak camera and a charge-coupled-device (CCD) in combination. The method also allows the study of gas puff reliability. Any differences between gas shells can then be examined and interpreted with reliable certainty. Imaging software is used to determine the density from the intensity of the fluorescence images. A detail account of the process is illustrated in this study. A control system was constructed for operations of the gas puff valve in both LIF and z-pinch experiments. The pressure system is designed to tailor specific profiles as needed. The LIF system is detailed along with any components built for the gas puff valve. Results of these measurements serve to verify the uniformity of flow and determine the density distribution of the gas puff.
Gas puff density measurements; Laser inducced fluorescence; Cornell Laboratory of Plasma Studies
Kusse, Bruce Raymond
M.S., Applied Physics
Master of Science
dissertation or thesis