Radiation Efficiency and Kinetic Calculations for the Positive Column in Hg/Ar Mixtures II. Impact of Tube Radius and Current Density

Abstract

In a preceding part of the paper, based on experimentid methods and on a corresponding kinetic model, especially the impact of the effective life times of the 63P1 and 61P1 Hg resonance levels on the main properties of the low pressure Hg-Ar positive column has been studied. In the presented second part these investigations, which have been performed under the aspect of their applicnt.ion in fluorescent lamps, will be continued. They are related to the effects of tube radius and discharge current density. New fluorescent lamps have reduced tube radii from R = 18 t o 13 mm and compact lamps down to R = 5 mm. Thus it is of interest to study the electron distribution function and main macroscopic properties of such low pressure discharge plasmas, where the latter properties nre obtained by adequate energy space averaging. At first, results are reported and discussed which are related to the dependence of main plasma parameters on the Hg partizrl pressure when reducing the discharge tube radius for constant discharge current i and argon pressure P,,~. Starting from the electron distribution function thc particle and energy budget will be studied in detail, especially of course the change of the ultraviolet radiation output from both Hg resonmce levels 63P, and 61P1 and, in addition, of visible radiation. Then, to understand the effect of the discharge current density, as a reprcsentntive example two cases with different v i h e s of R, i and pAr but with equal current density have been investigated and discussed.Altogether the investigations made will shed light upon the complex relntions in the mentioned mixture plasma and give hints to select suitable pnrnmetcr values which can be usefill to irnprovc light soiirccs.

Particle in cell simulations of low pressure small radius positive column discharges

“…As better electrode materials become available, the incentive to operate at smaller buffer gas pressure will increase. In addition, the incentive to operate at small discharge diameter exists because the efficiency of light production increases as discharge diameter decreases and because of the marketability of compact fluorescent lamps [3,4]. Thus, the need for positive column simulation techniques at lower gas pressure and smaller discharge diameter is already established.…”