Simulation on the hollow cathode discharge in hydrogen

A rectangular hollow cathode discharge (HCD) in hydrogen with a pressure of 2 Torr is simulated using a 2-D fluid model. The potential, electric field, particle density, and average electron temperature are calculated. The discharge space consists of the cathode sheath region near the cathode electrode and the negative glow (NG) region in the central region of the discharge cell. A high electric field of thousands of V/cm and a low electric field of tens of V/cm appear in the cathode sheath region and NG region, respectively. The average electron temperature in the cathode sheath region is tens of eV, which is significantly higher than that in the NG region. Electrons and H3+ are the main negative particles and positive ions, whose peaks appear in the NG region, and the peak magnitude is on the order of 1010 cm−3. H atom is the highest-density neutral particle other than H2 with a peak density of 1013 cm−3. The reaction kinetics of the generation and consumption of different particles are explored. The results show that each reaction generates certain particles while consuming other particles, ultimately achieving a dynamic equilibrium in the density of various particles. The electrons mainly originate from the ground state ionization between electron and H2 (e+H2 → e+H2++e) and are consumed by the dissociative attachment (e+H2 → H−+H). The charge transfer collision reaction (H2++H2 → H3++H) is the only reaction that produces H3+ ions. Different reactions to the consumption of H3+ ions do not differ significantly. The generation and consumption of H mainly originate from the electron collision dissociation reaction (e+H2 → e+H+H) and the ionization reaction (e+H→H++2e).