Interaction of a laser beam with a target may generate a high velocity expanding plasma plume, solid debris, and liquid nano- and microparticles. They can be produced from plasma recombination, vapor condensation or by a direct expulsion of the heated liquid phase. Two distinct sizes of particles are observed depending on the temperature achieved in the plasma plume: Micrometer-size fragments for temperatures lower than the critical temperature, and nanometer-size particles for higher temperatures. The paper presents experimental observations of fragments and nanoparticles in plasma plumes created from gold targets. These results are compared with theoretical models of vapor condensation and microparticle formation.

The paper presents an investigation on water drop breakup in the 'catastrophic' mode at Weber numbers above 10 5. Experimental data have been obtained on a detonation shock tube operated at a Mach number between 4.2 and 4.6. Displacement and deformation of the mist cloud generated around the droplet were observed with a shadowgraph system, and Schlieren imagery was used to visualise the bow and wake shocks around the droplet. We observe that all measured quantities scale with the initial drop diameter. In order to analyse the experimental results and relate these observables to the breakup process, numerical hydrodynamic simulations have been performed. Once validated by direct comparison with our experimental observations, the simulation results are used to see "through" the mist and infer the droplet evolution with dimensionless time T. According to our results, the breakup mechanism can be divided into 3 steps. First (T < 1), most of the liquid mass remains in one main drop, whose shape flattens due to the hydrodynamic forces; then (1 < T < 2) fragmentation begins along the outer rim of the liquid drop and splits the corresponding mass into two parts; the first spreads out radially in small fragments while the remains finally (2 < T < 3.5) take the shape of a filament aligned with the flow. Our results are consistent with a complete breakup time T b = 5.5.

This paper presents numerical simulations of hypervelocity impacts of 0.5-mm steel spheres into graphite, for velocities ranging between 1100 and 4500 m/s. Experiments have evidenced a non-monotonic evolution of the projectile penetration depth, along with the trapping of the projectile below the crater surface. Using numerical simulations and simple constitutive relations, we show how our experimental results can be related to both materials mechanical properties. We take advantage of the succession of physical mechanisms to build a step by step procedure and identify thresholds of yield and spall strength that allow a first restitution of the experimental results. These threshold values for the steel projectile were found to be consistent with the literature. As regards the graphite target, the yield strength has also been identified, and we propose to model its dependence with pressure through a linear relation. Comparisons between experiments and simulations are presented and discussed. Despite some difference at the highest impact velocities, the overall trend is well reproduced, which suggests that our results could be used as a starting point for further studies with more complex models.

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