Laser Ablation of Aluminum Near the Critical Regime: A Computational Gas-Dynamical Model with Temperature-Dependent Physical Parameters

The complexity of the phenomena simultaneously occurring, from the very first instants of high-power laser pulse interaction with the target up to the phase explosion, along with the strong changes in chemical-physical properties of matter, makes modeling laser ablation a hard task, especially near the thermodynamic critical regime. In this work, we report a computational model of an aluminum target irradiated in vacuum by a gaussian-shaped pulse of 20 ns duration, with a peak intensity of the order of GW/cm2. This continuum model covers laser energy deposition and temperature evolution in the irradiated target, along with the mass removal mechanism involved, and the vaporized material expansion. Aluminum was considered to be a case study due to the vast literature on the temperature dependence of its thermodynamic, optical, and transport properties that were used to estimate time-dependent values of surface-vapor quantities (vapor pressure, vapor density, vapor and surface temperature) and vapor gas-dynamical quantities (density, velocity, pressure) as it expands into vacuum. Very favorable agreement is reported with experimental data regarding: mass removal and crater depth due to vaporization, generated recoil momentum, and vapor flow velocity expansion.

Atmospheric wave energy of the 2020 August 4 explosion in Beirut, Lebanon, from ionospheric disturbances

<p>Atmospheric waves excited by strong surface explosions, both natural and anthropogenic, often disturb upper atmosphere. In this letter, we report an N-shaped pulse with period ~1.3 minutes propagating southward at ~0.8 km/s, observed as changes in ionospheric total electron content using continuous GNSS stations in Israel and Palestine, ~10 minutes after the August 4, 2020 chemical explosion in Beirut, Lebanon.  The peak-to-peak amplitude of the disturbance reached ~2% of the background electrons, comparable to recently recorded volcanic explosions in the Japanese Islands. We also succeeded in reproducing the observed disturbances assuming acoustic waves propagating upward and their interaction with geomagnetic fields.</p><p><strong>Keywords:</strong> Chemical explosion,<strong> </strong>Beirut, N-shaped pulse, Total electron content</p>

Atmospheric wave energy of the 2020 August 4 explosion in Beirut, Lebanon, from ionospheric disturbances

Atmospheric waves excited by strong surface explosions, both natural and anthropogenic, often disturb upper atmosphere. In this letter, we report an N-shaped pulse with period ~ 1.3 min propagating southward at ~ 0.8 km/s, observed as changes in ionospheric total electron content using continuous GNSS stations in Israel and Palestine, ~ 10 min after the August 4, 2020 chemical explosion in Beirut, Lebanon. The peak-to-peak amplitude of the disturbance reached ~ 2% of the background electrons, comparable to recently recorded volcanic explosions in the Japanese Islands. We also succeeded in reproducing the observed disturbances assuming acoustic waves propagating upward and their interaction with geomagnetic fields.