Rate equations based on the simplified four level model are derived, and the results of the computer simulation satisfactorily explain the pulse forming mechanism in a TEA $CO_2$ laser. To understand the glow-arc transition in the high pressure gas discharges, neutral dynamics is employed and the electrode phenomena are analysed.
Parameters and detailed informations are described for the design and construction of the laser oscillator system.
In a pearson-Lamberton type TEA $CO_2$ laser, the density of electrons from wire discharge is limited because increasing the value of the coupling capacitor causes non-uniformity in preionization discharge itself and results in arc formation in the main discharge. To solve this problem, triple discharge system with the second set of trigger wires are tried in this experiment, and distinctly improved excitation is obtained compared with that of the double discharge system.
For the same gas composition, the optimum operation voltage of the triple discharge system is higher than that of the double discharge system because the more intense preionization of the triple discharge suppresses the glow-to-arc transition under the higher energy input. More energetic preionization of the triple discharge system allows uniform discharge in the gas mixture containing less helium, and stable operation of the laser is observed even for the mixture $CO_2:N_2:He=1:1:1$.
The maximum output energy of the triple discharge laser is 400mJ at the helium concentration of 47%, and this gives the output energy density of 25 J/l.
The performance characteristics of the triple discharge TEA $CO_2$ amplifier is investigated, and the small signal gain of 2.0% is obtained.