A waveguide discharge sustained by Trivelpiece-Gould mode propagation

Abstract

A fluid model of magnetically confined surface-wave plasma columns maintained in a diffusion-controlled regime is given. The propagation of the Trivelpiece-Gould mode which sustains the discharge is in a strong magnetic field. The self-consistent wave-discharge behaviour is ensured by a nonlocal nonlinearity involving transport (diffusion) along the external magnetic field. Simultaneous variation along the discharge's length of the plasma density and maintenance field intensity is the final result presenting the axial structure of the discharge.

Trivelpiece‐Gould mode produced gas‐discharges in a diffusion‐controlled regime

“…used for obtaining (2) from (6), is derived -as discussed before [9,10,12,19] -within the approach of nonlocal heating, appropriate when Ä ² Ê where Ä is the scale length of thermal conduction. The normalizing parameter in (8) …”

“…The nonmonotonic behaviour of ¢ with the Ô-increase, given by (2), is something peculiar for discharges in an external magnetic field. Since both ¢ and ¼ (as well as ± ¼ × ) monotonically increase with the Ô-increase, the nonmonotonic ¢´Ôµ dependence is due to the nonmonotonic changes of with the gas pressure increase (for ¼ const., according to (9), has a maximum at a given Ô-value). Thus, whereas in surface-wave sustained discharges ¢ decreases with increasing Ô, in discharges maintained by TG-waves ¢ has a maximum for a given Ô.…”

“…The second direction [8,9] is in the more traditional -for surface-wave sustained discharges [10] -trends of modelling long plasma column production in glass tubes which, when an external magnetic field is applied, is by TG-modes. A pressure range up to hundred millitorr is considered accounting for direct ionization and diffusion in a transverse direction with a coefficient appearing in its classical form or close to it, as it should be expected for an ambipolar diffusion regime in dielectric vessels [7,11].…”

“…The model in [8] shows the radial structure of the discharge when the behaviour of the TG-mode is described in radially-inhomogeneous plasmas. The model in [9] stresses the axial self-consistency of the discharge structure. It shows that in an infinite magnetic field, the longitudinal diffusion is the mechanism ensuring the relation between plasma density and maintenance field intensity (or, equivalently, power absorbed on average by an electron).…”

Travelling-wave-sustained discharges

“…Operation of stationary and pulsed discharges, discharge maintenance without and in an external magnetic field as well as discharge production in different gases (argon, helium, helium-argon gas mixtures and hydrogen) are covered [16][17][18][24][25][26][27][28][29][30][31][32][33]. In all the cases, the basis of the discharge maintenance-the discharge self-consistency and the electron heating in the high-frequency field-are stressed.…”