Radiofrequency breakdown at low gas pressures

Gas breakdown is certainly one of the most spectacular phenomena in discharge physics, during which gases change from an insulator to a conductor. This phenomenon has attracted considerable interest since the beginnings of the investigations of ionized gases. Depending on the conditions, a variety of gas-phase and surface elementary processes can contribute to the development of electron avalanches, which at some point during the process can establish sufficient ionization and charge reproduction. In alternating (radiofrequency) electric fields, the roles of gas-phase and surface processes change considerably with the frequency of the excitation voltage, making the breakdown process more complex as compared to the case of static fields. Recent studies of gas breakdown have been aided by advanced experimental diagnostic tools (like Phase-Resolved Optical Emission Spectroscopy) and numerical approaches (like Monte Carlo and Particle-in-Cell / Monte Carlo collisions simulations). These tools provide a detailed insight into the microscopic spatio-temporal dynamics of the charged particles and the development of the plasma via consecutive phases of the breakdown process.