Effects of Illumination Uniformity Improvement on X-ray Lasing Plasma

An accurate knowledge and an efficient control of the plasma conditions are required for the optimization of the gain to realize a small scale efficient X-ray laser1. We already observed that large scale density inhomogeneities were driven by laser nonuniform irradiation2. In the present work a novel focusing arrangement3, composed of a segmented wedge array (SWA) to overlap several line foci, was employed to produce a nearly uniform illumination. We use simultaneously spatially (2D) and time resolved diagnostic to see, in lasing plasmas, how critical is the irradiation nonuniformity, for various pumping schemes.