Study of a contracted glow in low-frequency plasma-jet discharges operating with argon

Abstract

In this work, we present an experimental and theoretical study of a low frequency, atmospheric plasma-jet discharge in argon. The discharge has the characteristics of a contracted glow with a current channel of submillimeter diameter and a relatively high voltage cathode layer. In order to interpret the measurements, we consider the separate modeling of each region of the discharge: main channel and cathode layer, which must then be properly matched together. The main current channel was modeled, extending a previous work, as similar to an arc in which joule heating is balanced by lateral heat conduction, without thermal equilibrium between electrons and heavy species. The cathode layer model, on the other hand, includes the emission of secondary electrons by ion impact and by additional mechanisms, of which we considered emission due to collision of atoms excited at metastable levels, and field-enhanced thermionic emission (Schottky effect). The comparison of model and experiment indicates that the discharge can be effectively sustained in its contracted form by the secondary electrons emitted by collision of excited argon atoms, whereas thermionic emission is by far insufficient to provide the necessary electrons. V

Experimental and theoretical study of an atmospheric air plasma-jet

“…The derivation and details of the cathode layer model can be seen in Ref. 4, of which we here give a short account.…”

“…These latter aspects are particularly complex for gases other than noble gases, and especially in the case of air. We have recently presented a study of a low-frequency plasma jet (without a dielectric barrier) operating with argon 4 and found that a rather involved model is required to properly account for the plasma discharge characteristics. It was found that the discharge consists of a non-thermal plasma with a current channel of submillimeter diameter and that impact on the cathode by metastable excited argon atoms, generated under the action of the relatively high electric field in the cathode layer, are required to produce the flow of secondary electrons needed to sustain the discharge.…”

Ambient Species Density and Gas Temperature Radial Profiles Derived from a Schlieren Technique in a Low-Frequency Non-thermal Oxygen Plasma Jet

“…Among different kind of non-thermal atmospheric-pressure plasma sources, low-current (*0.1 A) plasma jets have rapidly gained importance in various plasma processing applications (including biomedical applications) because they can operate in open air providing plasmas without spatial confinement [5,[8][9][10][11]. An afterglow containing electrons, ions and relative long-lifetime radicals dragged from the confined discharge by a relatively large gas flow; is formed at the outflow of those sources.…”