Optical probe investigation of laser ablated carbon plasma plume in nitrogen ambient

Abstract

We report the study of carbon plasma produced using 1064 nm laser in nitrogen ambient at atmospheric pressure using 2-dimensional fast imaging of ablated plume, optical emission spectroscopy, and optical probe at 532 nm for interferometry and shadowgraphy. The dominance of C 2 and CN molecules over ionic species at later stages of expanding carbon plasma plume is reported. The observed ring structure in shadowgrams and change in the direction of fringe shift from positive to negative in recorded interferograms are correlated with the relative abundance of different species in the plasma plume as function of time delay with respect to ablating pulse. An agreement in observed onset time of formation of clusters/atomic species or low ionic species using different diagnostic techniques has been reported. V C 2013 AIP Publishing LLC.

Investigation of ion dynamics of laser ablated single and colliding carbon plasmas using Faraday cup

“…The frequent collision between them results in loss of thermal kinetic energy of ions and hence forward movement of plasma species decreases with increase in pressure which enhances the recombination process. At high nitrogen ambient pressure abundance of slow-moving clusters, atomic/molecular species are found compared to ionic species which leads to decrease in ionic yield [ 27 ].

Figure 2 (a) The ion trace of Faraday cup at different collector bias voltage at 10 −5 mbar ambient pressure.

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“…interferometry, optical emission spectroscopy (OES), 2D imaging, ion probe etc. [ 3 , 23 , 27 , 28 , 29 , 30 ]. There are several limitations of each diagnostic technique depending upon the experimental conditions.…”

Effects of a static inhomogeneous magnetic field acting on a laser-produced carbon plasma plume

“…When the laser-produced carbon plasma expands in a low pressure neutral gas backgrounds, the main effect of the background gas is to favor C 2 molecule formation through three-body collisions involving a neutral atom or molecule. 5,20,35,37 As in this case no significant gas background effect is to be expected to promote C 2 molecules formation, a different mechanism should be accounted. In this case C 2 molecules formation might be explained by magnetic field induced enhanced collisionality, as a result of reduced radial diffusion.…”

“…In particular, our results show that in a vacuum background the presence of the magnetic field plays an equivalent role to that of a low pressure neutral background gas, in order to favor the emission of successive plasma fronts and C 2 molecules formation, as reported previously in investigations of laser produced carbon plasmas. 4,5,[17][18][19][20] …”