Shaping and Controlled Fragmentation of Liquid Metal Droplets through Cavitation

Abstract

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.

Cylindrically and non-cylindrically symmetric expansion dynamics of tin microdroplets after ultrashort laser pulse impact

“…Prior works have studied the deformation of liquid tin droplets irradiated by femto-and picosecond laser pulses [7,8,[11][12][13]. A general observation is that irradiation by such ultrashort pulses leads to the generation of intense pressure waves inside the droplet, resulting in shock-wave-driven phenomena such as cavitation and spallation, and associated explosive fragmentation.…”

Smoothed particle hydrodynamics simulation of a laser pulse impact onto a liquid metal droplet

“…An unstructured pseudo-grid consisting of tetrahedral cells is created inside the liquid sphere, by defining the number of the discretization nodes on the radius and on the quarter circle arcs. In order to model the laser pulse which impacts the liquid metal droplet in [ 26 ], a constant pressure field of p init = 1.25 ⋅ 10 11 Pa , based on the ablation pressure scaling law [ 63 ], is applied as initial condition on the outer shell of the hemisphere with positive z-axis values (the corresponding density from Tait EoS is ρ init = 12530.0 kg / m 3 ), while the pressure in the rest of the droplet is zero (corresponds to density of ρ 0 = 7300.0 kg / m 3 ). The thickness of the outer shell is actually the initial diameter of the droplets and thus, it depends on the particles population.…”

“…Basko et al [ 25 ], employed experimental, theoretical and numerical methods for studying the deformation and fragmentation of a metal droplet by sub-picosecond and picosecond laser pulses. Recently, Krivokorytov et al [ 26 ] impacted metal droplets with sub-picosecond laser pulses and they captured their expansion and fragmentation, as well as high-speed jets starting from the droplet surface. The cause of this jetting phenomenon is cavitation formation at the center of the droplet, due to the rarefaction wave and the number of the jets was correlated to the laser energy by coupling the cavitation bubble dynamics with Rayleigh-Taylor instabilities.…”

Jetting from cavitation bubbles in viscous and confined liquids

“…Chapter 5 is published as Krivokorytov, M.S., Zeng, Q., Lakatosh, B.V., Vinokhodov, A.Y., Sidelnikov, Y.V., Kompanets, V.O., Krivtsun, V.M., Koshelev, K.N., Ohl, C.D. and Medvedev, V.V., 2018.…”

“…Shaping and controlled fragmentation of liquid metal droplets through cavitation. Scientific reports, 8(1):597, 2018 (Krivokorytov et al, 2018).…”