Characterization of pulsed gas sources for intense laser field-atom interaction experiments

We describe the application of a tunable differential interferometer to the characterization of pulsed gas valves, operating in the low-pressure regime ( Torr). The spatial profile of the pressure in the gas jet has been studied for piezoelectric and electromagnetic valves in various experimental conditions, for both Ne and Ar gases. Moreover the time response of the valves has been investigated by using, for the first time to our knowledge, the third harmonic generation process. The number of third harmonic photons has been determined as a function of the delay time between a Nd:YAG pump laser pulse and the opening time of the valve, thus allowing the determination of the jet temporal profile. The time dependence of the local pressure in the jet has been studied for various gas pulse durations.