Intensity distribution of the focal lines of the prepulse and mainpulse at the solid target surface

Abstract

At the Prague Asterix Laser System (PALS) the former Asterix iodine laser of the Max-Planck-Institut fur Quantenoptik is currently re-installed. For the x-ray laser experiments that will be performed in the near future a well defined focal line at the position of the target surface is crucial. Applying the prepulse technique there are two possibilities, either the main beam and the prepulse beam are focused by the same focusing optics or the two different beams are focused by two optical systems separately. It is important to characterise the intensity distribution of the both line foci in two dimensions (along and across the focal line), since their energy ratio is giving only a mean value and not the actually existing non-uniformity's along or across the focal line. By using two different focusing optics it is possible that the two line foci do not have exactly the same width. In order to realise a well defined prepulse line focus it is necessary to measure the intensity distribution in two dimensions. We concept a method to obtain quantified two-dimensional focal images and we present preliminary experimental results using a cylindrical lens array as well as using only a single cylindrical lens in combination with a spherical focusing lens.