Theoretical and experimental studies of phototriggered discharges in argon and neon

Abstract

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.

The influence of and molecules on discharge equilibrium and F-atom production in a phototriggered HF laser using

“…A detailed description of the experimental discharge structure, called 'X510', has been published previously [18]. It is a compact design, with a low circuit inductance L, which has already been used to energize a XeCl * (308 nm) excimer laser [17].…”

OH kinetics in photo-triggered discharges used for VOCs conversion

“…The Boltzmann equation is solved using algorithms developed by Ségur and Bordage [27]. Details on the code configuration and the numerical procedure are given in [26]. The measured time evolutions of the voltage and the discharge current were compared to the computed ones in order to check that energy deposition in the plasma composed of atmospheric gases is well predicted by the model [7,8].…”

“…A 0D model has been previously developed [5][6][7][8]26], which couples : i) the solution of the Boltzmann equation for the electrons, ii) the kinetic equations describing the temporal evolution of the various species (molecular excited states, ions, atoms, radicals, molecules) produced during the discharge or during the afterglow, iii) the electric circuit equations given by the Kirchoff laws. Many reaction rates are sensitive functions of the gas temperature so that temperature time evolution is taken into account through the resolution of the energy conservation equation.…”

Two-step ionization in non-equilibrium SF6discharges at high current density

“…In order to clarify this question, new experiments and calculations have been performed in a very large range of discharge conditions correlated to the excitation of the pulsed chemical HF/DF laser by photo-triggered discharges. In the photo-triggered scheme [10,[14][15][16][17][18][19][20], the discharge electrodes are directly connected to an energy storage unit charged up to a voltage V 0 in a few microseconds. Once the desired voltage has been reached, the pre-ionization is achieved by means of UV-photons or x-rays and initiates the gas breakdown with a variable time lag.…”

“…In electronegative gases, the main advantage of the phototriggered technique relies on the fact that the initial electrons produced by the pre-ionization are immediately subjected to a high electric field, in such a way that the electron multiplication processes largely overcome the losses due to the electron attachment. As a result large volume homogeneous discharges can be produced [10,[15][16][17][18][19][20] and their properties can be directly compared to the predictions of zero-dimensional discharge modelling.…”