Global model for plasmas generated by electron beams in low-pressure nitrogen

A global model is presented to determine the densities of the major charged and neutral species generated by a thin, planar electron beam passing through low-pressure nitrogen. The creation rates are based on results provided by a Boltzmann code that includes contributions not only from the beam electrons but also from the energetic daughter electrons created by ionization. Optical emission spectrometry is used to help validate the rates, and measurements of the total ion density are used to help validate the charged-particle densities. A key conclusion of the study is that electron-beam-generated plasmas differ strongly in character and composition, and thus in capabilities, from plasmas generated by the electrical discharges now widely used in material processing.