THEORETICAL AND EXPERIMENTAL STUDIES OF PHOTOTRIGGERED DISCHARGES IN ARGON AND NEON

Characteristics of phototriggered discharges in pure argon and neon have been experimentally and theoretically investigated at pressures between 0.5 and 5 bars and reduced electric fields E/N in the range 5 to 50 Td. Emphasis is laid on the breakdown delay time, defined as the time lag between the application of a very short preionization pulse and the occurrence of the discharge. The model, developed in the frame of the local field approximation, gives breakdown delay time values in excellent agreement with the experimental results. However, in pure neon, the experiments have revealed a large influence of very small amounts of easily ionizable impurities. The calculations point out that the discharge behavior is mainly determined by the electron multiplication rate due to direct ionization of ground state atoms. Other ionizing processes, such as two-step ionization or Penning effects, or the electrical parameters of the circuit (inductance, capacitance, and intensity of the preionization) have only a secondary effect on the breakdown delay time.