Laser Diagnostics of a Nansoecond Pulsed Helium Plasma Jet Using Thomson Scattering and Talif

Non-invasive laser diagnostics such as Thomson scattering and Two-Photon Absorption Laser Induced Fluorescence (TALIF) are powerful tools to measure electron properties and to probe the plasma chemistry with high spatial and temporal resolutions. Using laser Thomson scattering, the electron density and electron temperature of a 140-ns pulsed helium plasma jet were resolved in distributions of bell-shaped profiles with lower values in the center and higher at the outer edge of the 1-mm diameter helium flow column. Laser energy dependence studies were performed to validate the quantitative measurements. Absolute atomic oxygen measurements for the same plasma jet using TALIF, however, revealed a Gaussian-shaped distribution of the O-density. Dependence of the electron properties and atomic oxygen generation on the peak voltage of the applied nanosecond pulses and the oxygen concentration in helium are discussed.