Vapor clouds generated by laser ablation and hypervelocity impact

Abstract

[1] Laser ablation experiments are carried out using a high intensity laser ($10 10 W/cm 2 ) and basalt targets. Using a high-speed camera and a spectrometer, the radius and the temperature of the silicate vapor clouds generated by laser ablation are observed as a function of time. Then a numerical simulation of vapor expansion is carried out, and the thermodynamic state of the silicate vapor is determined so as to reproduce the experimental results. The result of the analysis indicates that the impact velocity which would generate a vapor cloud with this thermodynamic state is $120 km/s for collisions between two basaltic bodies.

Oxidation of carbon compounds by silica-derived oxygen within impact-induced vapor plumes

“…As mentioned in Section 2.1, entropy gained by our LPV experiments are estimated to be ∼10 kJ/K/kg, which corresponds to impacts with velocity of several tens of km/s to hundred km/s (Kadono et al, 2002;Sugita et al, 2003), which is higher than the mean impact velocity of asteroids to the Earth (Chyba, 1991). However, the results of thermodynamic equilibrium calculations along adiabatic pressure-temperature paths suggest that difference in entropy gained by impact does not so much affect the vapor composition at low quenching temperatures where the chemical reactions within planetary-scale vapor plumes are expected to quench (<2000 K).…”

“…Thus, stoichiometric ablation, in which 9 W/cm 2 is sufficient for silicates and plastic materials to achieve stoichiometric ablation (e.g., Chan and Russo, 1991;Russo, 1995;Mao et al, 1996). Entropy gained by laser irradiation with such laser intensity is estimated to be equal to the entropy gained by hypervelocity impacts at velocities between several tens of km/s and a hundred km/s (Kadono et al, 2002;Sugita et al, 2003Sugita et al, , 2012.…”

“…In both experiments and thermodynamic calculations, we consider reaction systems consisting of silica (SiO 2 ) and polyethylene (PE). First, we conduct LPV experiments, which have been used to simulate impact vaporization (e.g., Mukhin et al, 1989;Kadono et al, 2002;Managadze et al, 2003;Sugita et al, 2003;Ohno et al, 2004) and measure whether CO and/or CO 2 are produced in even carbon-poor reaction systems. We use artificial samples, mixtures of silica powder and polyethylene powder, for investigating the effect of silica-derived oxygen.…”

Spectroscopic measurements of Si-O recombination process in laser-induced quartz vapor plumes

“…The excitation temperature of Si used was that of the most luminous part of the vapor between 20 and 21 μs and the SiO temperature is used was that of vapor between 40 and 100 μs. The temperature T of an expanding vapor plume is fitted well by a power-law function of time t, T = A ×t −b , where A and b are constants (Kadono et al, 2002). The value of b is 0.22 ± 0.02 for the vapor plumes observed in this study.…”

“…Incident radiation from outside of the radiation source is also assumed to be negligible. Since radiation sources produced by laser-irradiation are not expected to be homogeneous (Kadono et al, 2002), Eq. (A.15) does not apply in a strict sense.…”