This paper studies the dynamics of (dipole-dipole) laser induced collision processes. Coupled equations are numerically integrated, first over time, and then over impact parameter. Transition probability and collision cross section are given as a function of the detuning from the R = \infty frequency of the separated atoms, and of the incident laser power density. Numerical results are compared with approximate formulae for collision cross section at line center and in the wing.

Numerical analysis of laser induced inelastic collisions

A simple discharge model is used to evaluate the field uniformity requirements for TEA CO2 lasers and to predict the electron density distribution which results with Chang profile electrodes.

https://iopscience.iop.org/article/10.1088/0022-3735/11/11/006/pdf

Field uniformity requirements in TEA CO2 lasers

The useful usable time delay range between the preionizing and main discharges in a TEA CO2 laser, for reliable, arc-free operation, has been observed to be greatly reduced by the presence of small (<1 %) amounts of O2 in the laser gas mixture. Three-body attachment of thermal electrons to O2 molecules provides a loss mechanism for preionizing electrons to explain the observed results.

Attachment loss of photo-ionization electrons in TEA CO2 lasers

A simple model of photoionization of excited atoms by UV photons from capacitor spark discharges is suggested to explain the improvement in both plasma density production and laser efficiency noticed by several investigators when the proportion of helium in high-pressure CO 2 laser mixtures is increased. Such improvements with increased He proportion take place both with and without seeding with low ionization potential dopants. The model is also applicable to explaining the arc suppression qualities of helium as well as the ability to ignite discharges at higher total pressures when the proportion of helium is increased. Several implications regarding future TEA laser work are suggested.

The role of excited atoms in UV photopreionization TEA lasers

The attainable maximum pressure and the small signal gain are compared at pressures up to 3 bar in a TE-CO2 laser amplifier with two preionization systems. It is found that doping with tripropylamine increases the attainable pressure for glow discharges but decreases the small signal gain. At slightly superatmospheric pressure and low doping amount the simple lamberton-Pearson device gives the best results. For constant input energy the inversion grows with increasing total pressure.

Characteristics of CO2 TE-amplifiers with different UV preionization at superatmospheric pressure with doping additives

The effective recombination coefficient γ* in a self‐sustained CO2 laser discharge at a pressure of 1.3 bar is determined from a rate equation for the electron density using experimental values of the discharge current and voltage. It is found that γ* depends strongly on the electric field strength as well as on the electron density.

Determination of the recombination coefficient in CO2 laser discharges

Glow discharges in superatmospheric CO2-N2-He gas mixtures in a Lamberton-Pearson device

For a quantitative description of the fast, self-sustained, high-pressure gas discharges used in transversely excited gas lasers the waveforms of current and voltage must be known accurately. An integrated system is described measuring currents and voltages without any interference by using the Faraday and Kerr effects. The sensitivity of the current measurement is 20 mV kA-1. The Kerr cell can be used with different sensitivities within the range 10-150 kV. The rise time of each detector system is 5 ns.

http://iopscience.iop.org/0022-3735/11/3/017/pdf/0022-3735_11_3_017.pdf

H. Hübner

Papers

Characteristics of CO2 TE-amplifiers with different UV preionization at superatmospheric pressure with doping additives

Determination of the recombination coefficient in CO2 laser discharges

Glow discharges in superatmospheric CO2-N2-He gas mixtures in a Lamberton-Pearson device

Electro-optical measurement of current and voltage in fast, high-pressure glow discharges