X-Ray Laser Beam Shape Control: High-Res VIS and keV Imaging of the Amplifying Plasma

Summary

We describe results of an experimental study aimed to control the single-pass far-field profile of the X-ray laser beam at 21.2 nm emitted by a QSS neon-like zinc amplifier. The plasma is produced by a prepulse followed after 10 ns by the main pump pulse, both with duration of ~300 ps, focused down to a 3^-cm long line by a composite smoothing optics. This optics involves a matrix of 10 cylindrical lenses and an aspherical lens, and produces 10 individual line foci which are superimposed in the focal plane of the aspherical lens. In this work, we study the dependence of distribution of the pump intensity across the focal line and the spatial profile of the emitted X-ray laser beam. The intensity distribution of the pump emission is monitored by a high-resolution VIS camera, providing details >5 εm. The results show that the best X-ray laser beam profile is obtained when the partial line foci are not ideally superimposed, while for the “ideal” (=narrow) focus of the optical system the X-ray laser beam is split vertically into two characteristic lobes.