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

F. MINOTTI; L GIULIANI; M.XAUBET; D. GRONDONA

PHYSICS OF PLASMAS

AMER INST PHYSICS

Lugar: New York; Año: 2015 p. 1135121 - 1135127

1070-664X

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