CHARACTERIZATION OF GERMANIUM STRIPE X-RAY LASERS

One method of improving the transverse spatial coherence of x-ray lase rs (XRLs) is by adaptive spatial filtering of XRL apertures using geom etric shaping in the form of bowtie or wedge XRLs. However, we must ma intain the desired geometric shapes in exploding foil or slab configur ations during the lasing period. As a first step toward understanding lasing in such geometries, we study the behavior of simple stripe XRLs . Past experience with stripe XRLs deposited on thick plastic substrat es resulted in significantly weaker laser intensities as compared to l ine-focused slab XRLs. Possible reasons for this intensity reduction o f stripe XRLs could include mixing at the laser boundary, and changes in plasma, kinetics, and hydrodynamic properties that affect laser gai ns and propagation. We present experimental and theoretical characteri zations of germanium line-focused slab and stripe XRLs. Key experiment al parameters we are studying include images of emission profiles of t he laser blowoff, angular divergences, XRL output intensities, and ion ization balances as we vary XRL designs. We compare the experimental r esults with 2-D laser deposition and hydrodynamics simulations using L ASNEX, and study the changes in ionization balances and level populati ons from postprocessing LASNEX results.