Ionization phenomenon in high-density gaseous and liquid argon in corona discharge experiments

Abstract

Experimental investigations of corona discharge in Ar for a wide region of fluid density from a rare gas up to a liquid have been carried out. Corona current has been observed for a point cathode voltage above the threshold value . Values of have been measured for a wide range of fluid density N and for different cathode radii . The obtained dependences of on N and have been analysed using the Townsend - Meek breakdown criterion. For low-density gas the calculations of have been carried out by using universal data on ionization coefficient . The data of for low-density gas are in good agreement with these calculations. Deviation from the `gaseous' dependence has been obtained in measurements carried out with a continuous increasing of the fluid density. The onset corona voltage in dense supercritical gas and in liquid is appreciably smaller than the values calculated from the gaseous Paschen curve. To explain this disagreement a model of impact ionization in liquid was developed. An assumption was made that inelastic energy losses of fast electrons by excitation of atoms without their ionization are absent in liquid. The expression for the ionization coefficient in liquid Ar has been obtained and it was used for calculation of in liquid. The calculated values are in agreement with the experimental data obtained in liquid Ar.

Clustering effects in plasma-assisted chemical fluid deposition of copper: Similarities between deposition rate and density fluctuation

“…Electron scattering, attachment, and energy loss near the critical point are apparently anomalous because negative charges show the lowest mobility near the critical point [25], and breakdown (or corona onset) voltages show a transition near the critical point [11][12][13][14][15]. Bonifaci et al reported that the transition might be explained by a reduced electron-impact excitation cross section [12]. More electron-impact chemical activation could also be achieved with lower energy loss of the electron (higher electron energy).…”

“…Furthermore, if an unstable/dynamic microscopic structure were used efficiently, then the so-called 'clustering' could be used for processing, such as that observed in anomalous reaction rates near the critical point [10]. Thereby, we might be able to achieve plasma processing that is novel and unique -differing from plasma processing in either gas or liquid; perhaps such a novel method could be supported, in part, by the transition in breakdown (or corona onset) voltages near the critical point [11][12][13][14][15] and density fluctuation near the critical point with discharge plasma [16]. High-speed processing and unique processing might be the two strongest incentives for studying this novel processing environment.…”

Comparative studies of dc corona and back discharges in different gases

“…High ionisation coefficient [3,4] and high electron temperature in Ar cause that the discharge in this gas starts at lower voltages than for other gases tested. The bright point becomes a new source of ions of polarity opposite to that of the discharge electrode.…”

Interaction of Discharges in Heptane with Silicon Covered by a Carpet of Carbon Nanotubes

“…Discharges in liquids are intensively studied because of their use in many application fields, like electrical power systems, [1,2] plasma electrolytic oxidation, [3,4] electrical discharge machining (EDM), [5,6] nanomaterials synthesis, [7,8] and more recently bio-medical applications. [9,10] Interaction of discharges with electrodes is a complex topic, especially in microgap conditions where diagnostics are difficult to perform.…”