Nuclear Instruments and Methods in Physics Research A 461 (2001) 96–97 A facility for the measurement of electron transport parameters in a gas mixture V. Golovatyuk, E. Gorini, F. Grancagnolo, R. Perrino*, M. Primavera Dipartimento di Fisica and INFN, Sezione di Lecce, 73100 Lecce, Italy Abstract 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 mm) with a beam focus waist of the order of 10 mm. Such a facility has been used for measurements of the gas parameters of the He drift chamber of KLOE experiment at DANE and for preliminary measurements of gain and attachment coefficients in the binary mixtures (C 2 H 2 F 4 +3%, 10% isoC 4 H 10 ) planned for the ATLAS and CMS RPC systems. An upgraded version of the set-up, which allows also for O 2 and H 2 O vapour controlled contamination, is currently being used for measurements on ternary mixtures (C 2 H 2 F 4 +isoC 4 H 10 +SF 6 ). # 2001 Elsevier Science B.V. All rights reserved. The facility (Fig. 1) is built on an optical bench which hosts a N 2 pulsed laser, optical components (diaphragms, attenuators, periscope mirrors and a converging lens), an XYZ-triad of micrometric linear motion stages capable of 3 mm overall accuracy, a test chamber, and a He–Ne alignment laser. Two test chambers have been used so far. A drift cell made of annular electrodes 1 cm spaced defining the drift field region uses a proportional tube to collect the ionization electrons producing the detectable signal. An Al made box contains a 11  21 cm 2 RPC with a 2 mm gap. Through UV- silica windows the gas gap is reached by the laser, focused in a  10 mm spot (Fig. 2). The gas system (Fig. 3) allows for different gas mixtures, user controlled water content, easy exchange between different test chambers. Pressure and temperature are computer monitored. In addition, the system can operate under and over pressure. Up to four different gases in the flow ranges 0–2.5 sccm and 0–500 sccm with 0.001 f.s. accuracy are managed by a MKS flow/pressure controller 647B connected to MKS 1179 mass flow meters. O 2 and H 2 O content detection (up to Fig. 1. Schematic of the setup. *Corresponding author. E-mail address: roberto.perrino@le.infn.it (R. Perrino). 0168-9002/01/$ - see front matter # 2001 Elsevier Science B.V. All rights reserved. PII:S0168-9002(00)01178-5