Drift-velocity and electron-density measurements in electron-beam- irradiated Ar-F2 gas mixtures subjected to an external electric field

Measurements of drift velocity and electron density in electron-beam- irradiated Ar-F2 gas mixtures which have been subjected to an externally applied electric field are reported. The electron density was measured by time-resolved infrared interferometry. The drift velocity was derived from discharge-current-density measurements. Experiments were performed for gas mixtures with various fluorine concentrations between 0.025% and 2% and total mixture pressures between 0.5 and 2 atm. The electron-beam current density was varied between 10 mA/cm2 and 6 A/cm2 and the field strength was between 0 and 10 Td (1 Td=10-17 V cm2). The experimental results were analyzed using two coupled kinetic codes. One code calculated the secondary-electron energy distribution and the second code calculated the density of the different atomic and molecular ionic and neutral species. The two codes were run in cyclic order until a self-consistent solution was obtained. The experimental results for the drift velocity and electron density were compared with the theoretical predictions. From the dependence of the electron density on the fluorine concentration, the rate constant for dissociative attachment of electrons to fluorine has been obtained. The dependence of the drift velocity and the attachment rate constant for fluorine on experimental parameters such as electric field strength, fluorine concentration, and electron-beam current density are discussed in detail. It is shown that these dependencies can be explained by accounting for the mutual effect of these experimental parameters on the secondary-electron distribution function.