Penning ionization in doped CO2 TEA lasers

Abstract

A quantitative model is presented which predicts the behavior of the discharge of a CO2 laser gas mixture with a low-ionization seed gas. The basis of the developed model is the assumption of the so-called Penning ionzation mechanism in which metastable nitrogen molecules ionize the seed gas. The developed model will be compared with measurements on an appropriate CO2 laser device. As a result of this study, we describe the successful operation of a simple large-aperture amplifier with a diameter of 12 cm.

Parametric measurements on a doped CO2TEA laser

“…The results of this measurements are shown in fig. 12 and confirm the well established behaviour of a doped laser [3][4][5]. For high TPA concentrations (solid line) the peak current increases, while the laser voltage at which the discharge takes place decreases.…”

“…As a U.V. source we first used trigger wires [1,2], then knive edges [4], but finally a structure was developed that combines the simplicity of knive edges with the high U.V. production of sliding sparks.…”

“…It is well known that the performance of a simple wire triggered TEA laser improves drastically when a low ionization seed gas is added to the laser gas mixture [1][2][3]. Some explanations that have been given to this phenomenon are improved photo-ionization [1,2], and a modified electron energy distribution function [3][4][5] causing more optimal pumping and a shift of an attachment dominated discharge towards a more stable recombination dominated discharge. Negative effects have been reported in [3], where a depopulation of the upper laser level by TPA was measured.…”

Metastable states in gases with lives over 24 hours

“…Molecules in these states are notable to ionize the gas, but can cause secondary electron cmission from the cathode [61,68]. The radiative lifetime of a 1 Hg state is 15 9 10-6 s (REITS [69]). …”