Generation of gas density transition for laser wake field acceleration

Summary form only given, as follows. Recently, Suk et al. [2001] proposed a self-injection scheme using a sharp density transition In their scheme, a number of background plasma electrons are trapped near a sharp, localized, downward density transition and accelerated in the wake field. The experiments to verify Suk´s proposal is scheduled to perform using the Table Top Tarawatt (T/sup 3/) laser facility at KERI in Korea. In this paper, as a preliminary step, we present an experimental result on the generation of gas density transition. We use a tungsten wire just above a jet of He gas to generate a spatial modulation of the gas density in the direction of the beam propagation. We used a Mach-Zendher interferometer to measure the gas density distribution The fringe pattern in the plane of the gas jet is imaged onto a CCD camera. Second harmonic pulses from a Nd:YAG laser with the pulse width of 10 nsec were used as a probe of the interferometer. Spatial and temporal distribution of He gas density from pulse gas jet will be presented and discussed in detail.