Characteristics of CO2 TEA lasers with simple electrode configurations operating with or without helium

The design, construction and operation of two CO2 TEA lasers using cylindrical or extruded electrodes which are capable of operating without the presence of helium in the working gas mixture are discussed. The lasers employ aluminum electrodes with a cylindrical or handrail shape with steel preionization filaments located 3 mm from the cathode. In both lasers, operation without helium or traces of dimethylamine used as an ionization seed is possible at pressures up to 400 torr with cylindrical electrodes and up to 500 torr with the extruded electrodes. Energies of 1 J are typically obtained in 200 nsec pulses at repetition rates of 4/sec with an overall efficiency greater than 10 percent. The laser utilizing the extruded handrail-shaped electrodes is furthermore found to provide a more uniform field with a lower input energy density, allowing more efficient operation at higher pressures.