Abstract
The cavitation-driven expansion dynamics of liquid tin microdroplets is investigated, set in motion by the ablative impact of a 15-ps laser pulse. We combine high-resolution stroboscopic shadowgraphy with an intuitive fluid dynamic model that includes the onset of fragmentation, and find good agreement between model and experimental data for two different droplet sizes over a wide range of laser pulse energies. The dependence of the initial expansion velocity on these experimental parameters is heuristically captured in a single power law. Further, the obtained late-time mass distributions are shown to be governed by a single parameter. These studies are performed under conditions relevant for plasma light sources for extreme-ultraviolet nanolithography.
Highlights
Intense, short-pulse laser radiation can produce strong shock waves in liquids, leading in some spectacular cases to explosive cavitation and violent spallation of the material [1,2,3,4,5]
The remarkably sharp outer boundary of this ablated mass may be explained by the existence of an inhomogeneous two-phase, gas-liquid mixture of low average density but approaching liquid density in the vicinity of the ablation front [14,15]
We present an analysis of the cavitation-driven expansion dynamics of liquid tin microdroplets that is set in motion by the ablative impact of a 15-ps laser pulse
Summary
Short-pulse laser radiation can produce strong shock waves in liquids, leading in some spectacular cases to explosive cavitation and violent spallation of the material [1,2,3,4,5]. Such dramatic physical phenomena can readily find applications, a very recent example being in the field of nanolithography where microdroplets of liquid tin are used to create extreme-ultraviolet (EUV) light [6,7,8]. Recent developments [8,9], produced tentative but tantalizing evidence
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