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The discharge in an electron-beam-sustainer atmospheric pressure CO2 laser is investigated. An arbitrary two-dimensional geometry is employed in calculating the electric field. The conductivity is a function of the local electric field, the loss rate, and the ionization rate, the third of which is proportional to the energy deposition by high-energy electrons. The predicted discharge nonuniformities are compared with experimental results. Experimental evidence indicates that the discharge is recombination dominated.

The presentation will focus on issues which relate directly to the generation of coherent CO2, laser pulses at energy levels of up to -100J and duration of tens of microseconds. Important factors which influence the beam coherence will he addressed in the context of E -beam and self-sustained discharge technologies.An illustration of possible local and volumetric discharge non-uniformities will be provided.

A frequency sweeping (chirping) mechanism governed by the lasing gas pressure and composition has been observed in a long-pulse TE CO2 laser for the first time. The mechanism was detected in heterodyned data obtained from photomixing the pulsed laser output with a cw local oscillator. A theory has been developed which links this chirp-governing mechanism to the vibration-translation (V-T) transfer rate from the lower laser level to the ground state. This new theory extends the existing theories on chirp in pulsed CO2 lasers into the long-pulse regime.