Spherical shock waves in laser produced plasmas in gas

Gatti, M.; Palleschi, Vincenzo; Salvetti, A.; Singh, D. P.; Vaselli, M.

doi:10.1016/0030-4018(88)90299-4

Cited by 45 publications

(24 citation statements)

References 3 publications

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“…The results presented here are in good agreement with the numerical results by Zeng et al [2], where they considered only the positive radial variation of electron density, and also agree with the experimental results by Gatti et al [3]. The interferograms in [3] also show the void at the center of the plasma spark. It is important to note that in these two references and this paper, the density also depends on the time after the laser pulse.…”

Section: A Electron Temperature and Densitysupporting

confidence: 81%

“…This inverse Bremsstrahlung process dominates other gas ionization processes [1]. The first stage is breakdown as the gas is ionized, followed by laser energy absorption by the hot gas, and the last stage is detonation which results in plasma expansion and shock wave formation [2], [3]. The evolution of the plasma and the resulting shock waves have been studied both experimentally and theoretically [2], [4]- [6].…”

Section: Introductionmentioning

confidence: 99%

“…A study of plasma spherical shock waves using holographic techniques [3] showed that electron and neutral density pertubations cause phase changes between the two exposure beams. The hollographic 3-D fringe pattern observed showed that the shock wave expanded to a radius of 6 mm in 3 s in air while the electron density decreased from cm at to zero at mm within 650 ns.…”

Section: Introductionmentioning

confidence: 99%

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Radial Variation of Refractive Index, Plasma Frequency and Phase Velocity in Laser Induced Air Plasma

Mathuthu

Raseleka

Forbes

et al. 2006

IEEE Trans. Plasma Sci.

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Abstract-Laser-induced breakdown spectroscopy (LIBS) is a nonintrusive technique that needs no sample preparation and even recently, quantitative measurements were done without the need for calibration standards. Much research has been done on the laser induced air plasma to study the spatial variation of plasma parameters in the axial direction of the laser beam. In this paper, we report investigation on the radial variation of the refractive index, plasma frequency, and phase velocity of a plasma during laser induced breakdown of air. The results show that the radial variations of the plasma frequency and refractive index are caused by the radial electron density gradient of the plasma. The radial variation of the electron density shows a noticeable depletion at the center of the focus which results in plasma phase velocities greater than the speed of light. Further from the plasma core the electron density diminishes to ambient density at the edges of the plasma. The mean full-width at half maximum (FWHM) for these plasma profiles was found to be about 1.2 mm. The results further reveal that the plasma has a concave parabollic electron density and a convex parabollic refractive index profile near the center of the laser axis, i.e., around a diameter of 0.5 mm.Index Terms-Laser-induced breakdown spectroscopy (LIBS), phase velocity, plasma frequency, refractive index.

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Section: A Electron Temperature and Densitysupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Radial Variation of Refractive Index, Plasma Frequency and Phase Velocity in Laser Induced Air Plasma

Mathuthu

Raseleka

Forbes

et al. 2006

IEEE Trans. Plasma Sci.

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“…In the direction towards the lens, the newly ionized gas then absorbs the laser beam and enhances the propagation of the shock. As pointed out by Ramsden and Savic [16], Raizer [17], Gati et al [18], this process is similar to the propagation of a detonation wave in an explosive material. The difference between the two cases is the energy deposition.…”

Section: Introductionmentioning

confidence: 86%

An experimental and numerical study of laser-induced spark in air

Phuoc

2005

Optics and Lasers in Engineering

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“…The coefficient m depends on the plasma expansion geometry and is equal to 2/3 for planar propagation and 2/5 for spherical symmetry [85][86]. Eq.…”

Section: Geometric Set-upmentioning

confidence: 99%