Skew photonic Doppler velocimetry to investigate the expansion of a cloud of droplets created by micro-spalling of laser shock-melted metal foils

Abstract

International audienceDynamic fragmentation in the liquid state after shock-induced melting, usually referred to as micro-spallation, is an issue of great interest for both basic and applied sciences. Recent efforts have been devoted to the characterization of the resulting ejecta, which consist in a cloud of fine molten droplets. Major difficulties arise from the loss of free surface reflectivity at shock breakout and from the wide distribution of particle velocities within this cloud. We present laser shock experiments on tin and aluminium, to pressures ranging from about 70 to 160GPa, with complementary diagnostics including a photonic Doppler velocimeter set at a small tilt angle from the normal to the free surface, which enables probing the whole cloud of ejecta. The records are roughly consistent with a one-dimensional theoretical description accounting for laser shock loading, wave propagation, phase transformations, and fragmentation. The main discrepancies between measured and calculated velocity profiles are discussed in terms of edge effects evidenced by transverse shadowgraphy

Molecular dynamics studies of the roles of microstructure and thermal effects in spallation of aluminum

“…The crosses and triangles in Fig. 2(b) are the Hugoniot points and melting points obtained from the work by Loison et al (2012). The curves show good agreements between our MD simulations and available data.…”

Influence of edge conditions on material ejection from periodic grooves in laser shock-loaded tin

“…Interactions between these waves cause tension, which will lead to fracture in a solid sample (as discussed and evidenced in Ref. [14]), or produce cavitation in a liquid metal [17][18][19]. Such cavitation is expected to bound the amount of material to be excavated into each jet, so that this amount would be less in a periodic pattern (Fig.…”

“…Throughout the pulse reflection process, additional contribution of the incident unloading wave produces further cavitation and "micro-spall" [17][18][19], not represented in Fig. 7 for clarity.…”

Dynamic fragmentation of graphite under laser-driven shocks: Identification of four damage regimes

“…Many efforts have been done to understand and predict the mechanical effects of the laser-matter interaction through the development of empirical laws [8][9][10][11] and specific hydrocodes [12,13]. As a consequence, high-power lasers are now commonly used in a large scope of shock studies [14][15][16][17][18][19][20][21].…”