Hydrodynamic Computations Of High-Power Laser Drives Generating Metal Ejecta Jets From Surface Grooves

Understanding dynamic fragmentation in shock-loaded metals and predicting properties of the resulting ejecta are of considerable importance for both basic and applied science. The nature of material ejection has been shown to change drastically when the free surface melts on compression or release. In this work, we present hydrodynamic simulations of laser-driven microjetting from micron-scale grooves on a tin surface. We study microjet formation across a range of shock strengths from drives that leave the target solid after release to drives that induce shock melting in the target. The shock-state particle velocity (U p) varies from 0.3 to 3km/s and the shock breakout pressure is 3-120GPa. The microjet tip velocity is 1-8km/s and the free-surface velocity varies from 0.1 to 5km/s. Two tin equations of state are examined: a "soft" model (LEOS 501) where the target melts forU p > 1km/s and a more detailed multiphase model (SESAME 2161) that melts forU p > 1.4km/s. We use these two models to examine the influence of phase change and the choice of the material model on microjet formation and evolution. We observe in our computational results that jet formation can be classified into three regimes: a low-energy regime where material strength affects jet formation, a moderate-energy regime dominated by the changing phase of tin material, and a high-energy regime where results are insensitive to the material model and jet formation is described by an idealized steady-jet theory. Using an ensemble of 2D simulations, we show that these trends hold across a wide range of drive energies and groove angles.