A facility for the measurement of electron transport parameters in a gas mixture

A facility for studying electron transport parameters in a given gas mixture is illustrated. A controlled ionization is induced by means of multiple-photon processes by focussing a short (∼1 ns) pulsed nitrogen laser in the gas gap. The test gas volume, where a suitable E-field is applied, is installed on a micrometric motion system which allows to accurately scan the volume (resolution ∼3 μm) with a beam focus waist of the order of 10 μm. Such a facility has been used for measurements of the gas parameters of the He drift chamber of KLOE experiment at DAøNE and for preliminary measurements of gain and attachment coefficients in the binary mixtures (C2H2F4+3%, 10% isoC4H10) planned for the ATLAS and CMS RPC systems. An upgraded version of the set-up, which allows also for O2 and H2O vapour controlled contamination, is currently being used for measurements on ternary mixtures (C2H2F4+isoC4H10+SF6).