Absolute density distribution of H atoms in a large-scale microwave plasma reactor

Abstract

Absolute number densities and the spatial distribution of atomic hydrogen in a large-scale microwave plasma reactor were measured by means of two-photon absorption laser-induced fluorescence (LIF) with laser radiation at 205 nm. The microwave discharge was operated at 2.45 GHz with a maximum power of 2 kW. Absolute number densities were obtained by calibrating the LIF detection system via NO2 titration in a flow tube reactor and in the range from 0.5×1015 to 2.5×1015 cm−3. Compared to small-scale reactors with a volume-to-surface ratio less than 3 cm, this reactor has a relatively homogeneous spatial distribution of atomic hydrogen. The mole fraction of atomic hydrogen in hydrogen plasmas ranges from 10% to 20%. The gas temperature–volume effect plays an important role in the spatial distribution of atomic hydrogen in this reactor.