CHARACTERIZATION OF PULSED GAS SOURCES FOR INTENSE LASER FIELD-ATOM INTERACTION EXPERIMENTS

We describe the application of a tunable differential interferometer t o the characterization of pulsed gas valves, operating in the low-pres sure regime (less than or similar to 100 Torr). The spatial profile of the pressure in the gas jet has been studied for piezoelectric and el ectromagnetic valves in various experimental conditions, for both Ne a nd Ar gases. Moreover the time response of the valves has been investi gated by using, for the first time to our knowledge, the third harmoni c generation process. The number of third harmonic photons has been de termined as a function of the delay time between a Nd:YAG pump laser p ulse and the opening time of the valve, thus allowing the determinatio n of the jet temporal profile. The time dependence of the local pressu re in the jet has been studied for various gas pulse durations.