Internal structure and expansion dynamics of laser ablation plumes into ambient gases

Abstract

The effect of ambient gas on the expansion dynamics of the plasma generated by laser ablation of an aluminum target has been investigated using frequency doubled radiation from a Q-switched Nd:YAG laser. The diagnostic tools include fast photography of overall visible plume emission using a 2 ns gated intensified charged coupled device and space and time resolved emission spectroscopy using a 50 cm monochromator/spectrograph and photomultiplier tube. The expansion behavior of the plasma was studied with ambient air pressure ranging from 10 Ϫ6 to 100 Torr. Free expansion, plume splitting and sharpening, hydrodynamic instability, and stagnation of the plume were observed at different pressure levels. Space and time resolved emission spectroscopic studies showed a twin peak distribution for Al and Al ϩ species at farther distances illustrating plume splitting at pressures higher than 100 mTorr. Combining imaging together with time resolved emission diagnostics, a triple structure of the plume was observed. The expansion of the plume front was compared with various expansion models and found to be generally in good agreement.

The influence of plasma dynamics on the growth of Sm0.55Nd0.45NiO3 solid solution during pulsed laser deposition

“…As the time evolves, the second component (the slower one) joins the first component because of the background gas braking of the latter, and the plume splitting disappears. The plume splitting has also been reported by several authors [27][28][29][30][31]. S Lafane et al observed by fast imaging during the laser ablatio n of Sm 1-x Nd x NiO 3 target in background oxygen pressure, the plume splitting at time delays for which the plume front still follows an almost free-plume expansion.…”

“…Plume sharpening behaviour suggests that high kinetic energy particles are emitted closer to the target surface normal [31].…”

“…At longer time delays the measured distances value are smaller than those predicted by shock-wave model. In this stage, the drag model can be used to describe the behaviour of the plume expansion [28,29].…”

“…Generally, it requires oxide reaction above 1000 o C u nder exce ss ive o xy gen p ress ure o f abo ut 2 00 bars du ri ng several days [5][6][7]. Several studies have been reported also on the dynamics of the plasma plume generated by PLD of complex oxides in a background gas [8][9][10][11][12][13]. These studies showed that the dynamics of plasma plume is greatly affected by the ambient g a s p r e s s u r e .…”

Influence of spot size on propagation dynamics of laser-produced tin plasma

“…The plume expansion in vacuum can be described as self-similar and adiabatic and is treated well by Anisimov et al 8 Compared to plume expansion in vacuum; the interaction of the plume with an ambient gas is a far more complex gas dynamic process that involves deceleration, attenuation, and thermalization of the ablated species, as well as the formation of shock waves. [9][10][11][12] Our previous studies revealed a complex plume splitting in a laser created aluminum plasma expanding into an ambient environment where gas phase collisions transformed the initial temporal distribution into a very different final distribution. 12 We distinguished three distinct pressure regimes using fast photography, each of which is characterized by particular behavior of the plume.…”