Pulsed CsI-coated tufted carbon fiber cathode plasma

This paper discusses the out-gassing behavior of a repetitively pulsed electron beam diode with a CsI-coated tufted carbon fiber cathode and a carbon fiber anode. Through this paper, a cross section model was developed that utilizes experimental data including pressure, temperature and voltage (energy) for determination. Mass and optical spectroscopy identified neutral and ion species likely responsible for the pressure pulses. The identified neutral and ionization cross sections from the published literature and databases were compared with the experimentally determined cross sections. The types of cross sections were electron-neutral and was single impact leading to single, double and triple ionization as well as elastic scattering. This comparison leads to the conclusion that initial pressure bursts consist of plasma with constituents of Cs, Cs⁺⁺, Cs⁺⁺⁺, I, I⁺⁺, N₂, N₂⁺, H₂O⁺, H, H⁺, and H₂⁺. Larger pressure bursts after the initial ones also include Cs⁺ and I⁺. Smaller bursts observed during steady state operations fluctuate between plasmas that contain H and H⁺, and those that contain H, H⁺, and H₂⁺. Consistently, the initial pressure pulses exceeded those found under steady-state operations. The optical spectroscopy timing and results are self-consistent with what is obtained from the cross section model. The cross section model coupled with the experimental data determines the transient plasma makeup responsible for the observed pressure pulses.