Design and characterization of a thermal hydrogen atom source

The hydrogen atom source considered here incorporates a hot capillary fed by hydrogen gas. Our earlier measurements on a source heated by electron bombardment are interpreted in terms of a simple model which encourages us to design a source heated by the radiation from a filament. The radiatively heated source is much simpler, more reliable, and easier to run than the electronically heated source. Furthermore, the radiatively heated source is free of any energetic particles. In order to obtain quantitative data on the intensity, an apparatus is constructed revealing the angular distribution of the hydrogen atoms and molecules by means of a quadrupole mass analyzer. The intensity of the source is controlled by the mass flow rate of the feed gas and the electric power to the filament. The flux density of hydrogen atoms at a substrate 6 cm away from the source is variable over two orders of magnitude and extends up to some 1015 atoms/cm2 s