RESUMEN
This Letter presents a one-channel method of measurements of a grazing incidence reflection coefficient. The idea is to use the quasi-flat field extreme ultraviolet spectrometer to produce direct and reflected from the sample images of the spectral lines simultaneously at the same detector matrix. The analysis of a set of spectral lines in the working spectral range of the spectrometer gives the spectral dependence of the reflection coefficient. The results of the refection coefficient measurements for a plane ruthenium mirror for grazing angles of 6° and 10° in the spectral range 15-40 nm are presented.
RESUMEN
Targeting micrometer sized metal droplets with near-infrared sub-picosecond laser pulses generates intense stress-confined acoustic waves within the droplet. Spherical focusing amplifies their pressures. The rarefaction wave nucleates cavitation at the center of the droplet, which explosively expands with a repeatable fragmentation scenario resulting into high-speed jetting. We predict the number of jets as a function of the laser energy by coupling the cavitation bubble dynamics with Rayleigh-Taylor instabilities. This provides a path to control cavitation and droplet shaping of liquid metals in particular for their use as targets in extreme-UV light sources.
RESUMEN
The deformation and fragmentation of liquid metal microdroplets by intense subpicosecond Ti:sapphire laser pulses is experimentally studied with stroboscopic shadow photography. The experiments are performed at a peak intensity of 10^{14}W/cm^{2} at the target's surface, which produces shock waves with pressures in the Mbar range. As a result of such a strong impact, the droplet is transformed into a complex-shaped hollow structure that undergoes asymmetrical expansion and eventually fragments. The hollow structure of the expanding target is explained by the effects of cavitation and spallation that follow the propagation of the laser-induced shock wave.