MONTE-CARLO CALCULATION OF ELECTRON-TRANSPORT COEFFICIENTS IN COUNTING GAS-MIXTURES .1. ARGON METHANE MIXTURES

We describe a Monte Carlo simulation of electron transport in gas mixtures, under the influence of a uniform, nonionising electric field, E. Our calculations, in contrast with earlier studies of counting gases based on the Boltzmann transport equation, examine the anisotropic nature of electron diffusion. Independent estimators of the transverse and longitudinal diffusion coefficients F and DL are derived. For both pure argon and pure methane, predictions of the model are shown to be in good agreement with measurements of the electron mobility, μ, and of the ratios DμandDLμ at field-to-pressure quotients 0.03 ⩽ Ep ⩽ 2.0 V cm−1Torr−1. Alternative methane cross sections are compared in detail. Finally, our calculations are extended to the mixtures A-10% CH4. A-20% CH4 and A-50% CH4. This is the first part of an extensive study of electron drift and diffusion in common counting gas mixtures.

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