Expansion Dynamics Of Plasma Plume Research Articles

On the expansion dynamics of plasma plume produced by laser ablation of LiYF4 crystal in a helium atmosphere

The effect of helium ambient gas on the expansion dynamics of plasma plume produced by ablating the LiYF4 crystal with 355 nm laser pulses is investigated. To study the expansion dynamics, the time-resolved optical signals from the plume constituents, either neutral or ionized, were recorded as a function of various experimental parameters, including laser fluency, at different distances, d, from the target along the expansion direction of the plume and at various angles with reference to the target normal. The analysis of the plume constituents at different distances from the target was used to derive the expansion velocities of the species. Depending on the species and on d, the shifted Maxwell–Boltzmann distribution component of the fit gave the values of the expansion velocities in the range 1.0 × 104 m s−1–4.0 × 104 m s−1. The effect of laser fluency on the expansion velocities of the plume species was also investigated. With the exception of Y and Y+, the expansion velocities of all the plume species, increased linearly with increasing laser fluency up to ∼8 J cm−2. Beyond this value, a saturation regime is observed. The angular distribution of the plume constituents in 1 Pa of He evidenced that all the plume species were focused along the target normal, and the FWHM of the angular distribution curve resulted reduced when compared with the vacuum.

Influence of the distance between target surface and focal point on the expansion dynamics of a laser-induced silicon plasma with spatial confinement

Expansion dynamics of a laser-induced plasma plume, with spatial confinement, for various distances between the target surface and focal point were studied by the fast photography technique. A silicon wafer was ablated to induce the plasma with a Nd:YAG laser in an atmospheric environment. The expansion dynamics of the plasma plume depended on the distance between the target surface and focal point. In addition, spatially confined time-resolved images showed the different structures of the plasma plumes at different distances between the target surface and focal point. By analyzing the plume images, the optimal distance for emission enhancement was found to be approximately 6mm away from the geometrical focus using a 10cm focal length lens. This optimized distance resulted in the strongest compression ratio of the plasma plume by the reflected shock wave. Furthermore, the duration of the interaction between the reflected shock wave and the plasma plume was also prolonged.

Fast imaging of the laser-blow-off plume driven shock wave: Dependence on the mass and density of the ambient gas

Abstract A systemic investigation of expansion dynamics of plasma plume, produced by laser-blow-off of LiF–C thin film has been done with emphasis on the formation of shock wave and their dependence on the pressure and nature of the ambient gas. The present results demonstrate that highly directional plume produces a strong shock wave in comparison to shock produced by the diverging plume. Shock-velocity, strength and its structure are strongly dependent on ambient environment; maximum shock velocity is observed in helium whereas shock strength is highest in argon environment. The role of chemically reactive processes was not observed in the present case as the plume structure is almost similar in argon and oxygen.

Effect of ambient gas on the expansion dynamics of plasma plume formed by laser blow off of thin film

A study has been carried out to understand the influence of ambient gases on the dynamics of laser-blow-off plumes of multi-layered LiF–C thin film. Plume images at various time intervals ranging from 100 to 3000 ns have been recorded using an intensified CCD camera. Enhancement in the plume intensity and change in size and shape occurs on introducing ambient gases and these changes are highly dependent on the nature and composition of the ambient gas used. Velocity of the plume was found to be higher in helium ambient whereas intensity enhancement is greater in argon environment. The plume shapes have maximum size at 10−2 and 10−1 Torr of Ar and He pressures, respectively. As the background pressure increases further (>10−2 Torr: depending on the nature of gas), the plume gets compressed/focused in the lateral direction. Internal structure formation and turbulences are observed at higher pressures (>10−1 Torr) in both ambient gases.

Investigation of plume expansion dynamics and estimation of ablation parameters of laser ablated Fe plasma

A systematic investigation of expansion dynamics of plasma plume, generated by a Q-switched Nd–YAG laser at 532 nm with a fluence of ∼30 J cm−2 on Fe target, was done for three different ambient pressures of 2 × 10−4, 2 and 20 mbar of Ar using fast gated intensified charge coupled device imaging. The experimental observations are then fitted with the snow plow and shock wave models to estimate various laser ablation parameters such as laser energy deposited to the ablated material, mass ablated per laser shot, laser spot size and the background gas density. The estimated laser energy deposited to the ablated material is about 70% of the input energy. The density of ambient gas atoms, having interaction with the ablated species, is found to vary from 12% to 50% at 2 mbar and 24% to 80% at 20 mbar. Scanning electron microscope images confirm the effect of ambient gas pressure on the topography of the deposited thin film and size of the nanoparticles which is qualitatively explained on the basis of the changing kinetic energy of impinging plasma plume species due to change in ambient gas pressure.