Effective swarm parameters and transport coefficients in CO2 laser mixtures

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A pulsed electron swarm technique has been used to obtain effective attachment and ionisation cross-sections as well as electron drift velocities in mixtures of CO2 laser interest. In binary CO2:N2 mixtures, below a reduced electric field of E/N=60*10-17 V cm2, attachment was the principal ion production process. (N is the total gas number density.) The reduced attachment coefficients measured were small and in excellent agreement with numerical predictions. In ternary mixtures of He:CO2:N2, positive ion formation described by Townsend's first ionisation coefficient played a more important role over the same range of E/N. The reduced coefficient for total ion formation was measured and found to be in good agreement with numerical calculations. Electron drift velocities in both the binary and ternary mixtures were determined using a time-of-flight technique. Overall agreement with previous experimental and numerical results was good.