Diagnostic Study of Hydrogen in Large-sized Microwave Plasma Reactors by Two-Photon Absorption Laser-induced Fluorescence

Two-photon laser-induced fluorescence is applied to study atomic andmolecular hydrogen in large-sized hydrogen/hydrogenetic compound microwave plasma sources. The influence of the temporalevolution of the laser pulse on the determination of the absolute atomic hydrogen density is analyzed in detail. The temporaland spatial behavior of the H atom density and its mole fraction in large-sized microwave plasma sources is characterizedunder different discharge conditions. The gas temperature is found to have an important influence on the distribution of the Hatom density in these plasmas. A method to obtain the density and temperature of the molecular hydrogen from the laser-induced fluorescence signal is given.