Application of Acetone Planar Laser-induced Fluorescence Technology in Density Distribution Measurements of Gas Puff Load

Being simple to install and with excellent performance, gas-puff loads play an important role in the experimental study of Z pinch.^[1] The gas load in Z-pinch experiment is generated by Laval nozzle, which behaves as a supersonic transient gas flow with density between 10¹⁶ and 10¹⁷cm^-3. Studying the initial density distribution of the load gas flow is helpful to predict the nozzle performance, optimize the nozzle size structure, improve the implosion dynamics process, and finally achieve the purpose of improving the X-ray radiation yield. ^[2] In this paper, the aerodynamic equation and ballistic airflow model are used to analyze and calculate the initial gas flow density distribution of a single-layer gas puff load used in Qiangguang-Ⅰ. After that, a set of acetone PLIF equipment is designed for gas flow density measurements. A 266nm, 100mJ±5%, ~3cm focused laser beam passes through the Kr gas flow with acetone mixed in. An ICCD camera records the fluorescence signal from the direction vertical to the laser beam. The gas density distribution characteristics are obtained by caught fluorescence images coincident with the laser. ^[3] The results of theoretical calculations and measurements made by PLIF method are compared and analyzed, which preliminarily verifies the feasibility of the application of acetone PLIF method in the measurement of gas flow density distribution of the load. Then, using the established experimental platform, the gas density distribution of the single-layer nozzle is measured under the initial gas pressure of 150kPa and 300kPa respectively, and the variation of the gas density distribution characteristics of the gas puff load with time under different initial air pressures is given, which provides theoretical support for the selection of discharge time in the subsequent Z pinch experiment.