Shock physics and shadowgraphic measurements of laser-produced cerium plasmas

Abstract

Shadowgraphic measurements are combined with theory on gas-dynamics to investigate the shock physics associated with nanosecond laser ablation of cerium metal targets. Time-resolved shadowgraphic imaging is performed to measure the propagation and attenuation of the laser-induced shockwave through air and argon atmospheres at various background pressures, where stronger shockwaves characterized by higher propagation velocities are observed for higher ablation laser irradiances and lower pressures. The Rankine-Hugoniot relations are also employed to estimate the pressure, temperature, density, and flow velocity of the shock-heated gas located immediately behind the shock front, predicting larger pressure ratios and higher temperatures for stronger laser-induced shockwaves.

Experimental and computational investigation into the hydrodynamics and chemical dynamics of laser ablation aluminum plasmas

“…An estimation of the thermodynamic properties of this shock-heated gas layer can be determined by applying theory on gas-dynamics to measurements of the laser-induced shockwave. 72,73 In this work, theory is combined with experimental measurements of the shock front position to determine an initial pressure for the laser ablation aluminum plasma to initialize the computational model as well as to compare and validate the numerical predictions to real data.…”

Laser Ablation Plasmas and Spectroscopy for Nuclear Applications

“…218 Furthermore, higher laser fluences produce stronger shockwaves with larger propagation velocities. 54,200,219 Estimates of the initial energy supplied to produce the laser-induced shockwave are obtained using the Sedov-Taylor blast wave model, [220][221][222] which has been implemented with various strong shock phenomena including atmospheric nuclear weapons testing to estimate device yields 223,224 and supernova explosion events to describe expansion dynamics. 225 The blast wave model is an exact analytical solution that describes the distance an expanding blast wave travels through a homogeneous atmosphere with constant specific heat and density, and was derived using selfsimilar theory assuming a strong point source explosion.…”

“…Beyond the strong shock limit, shockwave expansion trajectories generated by LA are described by a power law dependence or the drag model. Further information on these formulations and their implementation can be found in Kwapis et al 54 In addition, the properties (pressure, temperature, density, and subsonic flow velocity) of the shock-heated gas immediately behind the shock front may be calculated using Hugoniot analysis. 233,234 Radioactive Plume and Atmospheric Monitoring…”

“…Laser-ablation-based techniques are continuously making valuable contributions to the broader nuclear forensics research field in areas such as plasma surrogates for nuclear fireball chemistry discussed earlier in this review, as well as similarity of other phenomena between LA plasmas and nuclear fireballs, particularly radio-frequency generation, 392 particle formation, 75 and strong wave generation and interaction with the ambient environment that is partially discussed earlier in this review. 54,55 As always, additional research and development will advance the capabilities of these techniques, and it is possible that these advances improve the applicability of these techniques for nuclear forensics analysis and not just for elucidating fundamental phenomena that occur during and following a nuclear detonation.…”

“…5,[48][49][50][51][52][53] LIBS has also been used to investigate the complex conditions present immediately following a nuclear detonation, where physicochemical plasma properties and LA shock physics are treated as surrogates for nuclear fireballs. 12,[54][55][56][57][58][59] Beyond post-detonation nuclear environments, LIBS is also applied to conduct in situ, noncontact analyses in the corrosive, high-temperature, and high-radiation environments of nuclear reactors. Examples of this application include the in-core reactor monitoring of next-generation reactor designs, specifically molten salt reactors (MSRs) and high-temperature gas-cooled reactors (HTGRs), where LIBS and associated LA-based hyphenated techniques are implemented to conduct quantitative elemental analyses of the reactor head-space, fuel, coolant, and offgases to identify possible failures in fuel and other materials.…”