Gas breakdown threshold measurements using a pulsed HF/DF laser

Deka, B. K.; Dyer, P. E.; James, D. J.; Ramsden, S.A.

doi:10.1016/0030-4018(76)90363-1

Cited by 9 publications

(3 citation statements)

References 12 publications

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“…When a lens focuses the laser beam, the distribution of irradiance in the focal spot is determined by the mode structure in the laser oscillator, by the effect of amplifiers and apertures in the system, and by the parameters of the lens. Single-element lenses were used in most of the previous experiments 12,14,20,[22][23][24][25][26] for focusing high-power laser beams and significant spherical aberration was often present, though it may be minimized by a suitable choice of curvatures. The presence of aberrations may lead to erroneous values of optical breakdown threshold even when the measured spot size is used for the determination.…”

Section: Resultsmentioning

confidence: 99%

“…[20][21][22] Recently, Chen et al 12 reported laser-induced breakdown and energy deposition in air at atmospheric pressure using the fundamental frequency from a Q-switched Nd : YAG laser. Their results give quantitative guidance for the selection of the laser energy to achieve the desired breakdown probability and energy deposition characteristics of the plasma.…”

Section: Introductionmentioning

confidence: 99%

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Energy Absorption and Propagation in Laser-Created Sparks

et al. 2004

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The energy absorption and laser propagation characteristics of air and argon sparks at one atmosphere have been investigated. To create the sparks, 532 nm pulses from a frequency doubled Qswitched Nd : YAG laser are used. We employed 2 ns gated fast photography for studying the time evolution of the kernel at early times. Optical emission spectroscopy is used to infer temperature and density of the sparks. Significant energy absorption by the plasma is observed just above the breakdown threshold. The energy absorption and propagation in the spark indicated that argon plasma is more absorptive than air plasma. The absorption of the spark increases with laser energy, and at higher energies absorption saturation is observed. A spiky behavior is observed in the transmitted temporal profiles of lasers at higher energies and this is explained as due to the formation of a self-regulating regime.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Energy Absorption and Propagation in Laser-Created Sparks

et al. 2004

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“…Onset of the breakdown process on the aerosol first of all needs the exceeding ofan energy density barrier (J/cm2), which corresponds to the vaporization threshold of materials of the constituent elements of air and then the passing of an intensity threshold (W/cm2) which is the breakdown threshold. The latter decreases with radiation wavelength, optical diameter of the aerosol and laser pulse duration ; it depends little on the material (1)(2)(3)(4)(5)(6)(7)(8)(9). It is clear that the transmitted energy ratio depends on the number of aerosols present in the beam path and their dimensional distribution.…”

Section: Experimental Arrangementmentioning

confidence: 96%

Study Of The Propagation Of A High Power Infrared Laser Beam Through The Atmosphere. Influence Of Meteorological Conditions

et al. 1989

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Propagation through the atmosphere of a high power laser beam is limited by gaseous and particulate extinction and above all by optical breakdown induced by aerosols with relatively low intensity thresholds. The plasma created strongly absorbs the incident laser radiation and thus limits the maximum energies transmitted behind the breakdown zone.The object of this paper is to study breakdown thresholds in terms of energy density and incident intensity as well as transmission ratios of a CO2 laser beam as a function of natural atmospheric conditions. The setting up of an automatic station for meteorological and fine granulometric measurements enabled us to know the state of the atmosphere over the first ten meters of the surface boundary layer at each moment during laser shots. Five kinds of characteristic situation from the meteorological point of view with visibility greater than 5 km was studied : A -cold anticyclone conditions with the approach of an atmospheric disturbance B -humid low pressure conditions C-disturbed conditions : rain and drizzle D-maritime and continental wind conditions E-breaking wave sea -state simulation with criteria of similarity.The analysis was carried out in two steps. The first consisted in correlating the variations in meterological parameters and those of the granulometry of the atmospheric aerosol. The second step linked the granulometric fluctuations to the variations in breakdown threshold and transmission ratios.Intensity and fluence thresholds from 70 -90 MW /cm2 ; 2 -4 J /cm2 up to 150 -160 MW /cm2 ; 6,5 -7,5 J /cm2 have been measured for these different conditions.Comparing the best transmission ratios obtained in a cleaned atmosphere with the worst in strongly breaking sea conditions, we have obtained for 62 J /cm2, energy transmission of 90 % and 40 % respectively and 25 % to 15 % for 250 J /cm2.

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