Propagation of a Light-Emitting Wave-Front in a Fine Tube Positive Column Discharge

Abstract

The propagation velocity of a light-emitting wave-front is observed to be u p∼2×10+5 m/s before Townsend breakdown and u p∼5×10+6 m/s after Townsend breakdown along a discharge tube of inner diameter r o∼1.2 mm and length of 900 mm relevant to liquid crystal display television backlighting. Before Townsend breakdown, the origin of this wave is the ambipolar diffusion of plasma flux with the propagation speed u p∝D a/r o for the plasma bounded by the radius r o with the diffusion coefficient D a along the positive column. After Townsend breakdown, the light-emitting wave-front propagates with the electron plasma wave generated by the pulses of driving voltage. The electron plasma wave propagates such a long distance along the tube without damping due to the effect of localized plasma generation by electron impact ionization collisions. The propagation velocity is described by u p∼2u e 2/u d, which is larger than the electron thermal velocity u e as well as the electron drift velocity u d.

Discharge Characteristics and Plasma Erosion of Various Dielectric Materials in the Dielectric Barrier Discharges

“…Under the special operating conditions, usually those of a low-pressure operation, the glow mode is present [42,43]. The latter cases of the I-V characteristics have been analyzed regarding the usual discharge-tube experiments, including the DBD structure with the gases of a low pressure that is approximately several tens of Torr [44][45][46][47]. At the breakdown voltage, the electron avalanche is accompanied by the Townsend discharge, which is the abrupt current increase followed by the normal glow in terms of the I-V characteristics.…”