The effect of dust on 10.6-μm laser-induced air breakdown

Lencioni, Donald E.

doi:10.1063/1.1654718

Cited by 145 publications

(32 citation statements)

References 5 publications

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“…www.lpr-journal.org It was discovered that the electron generation was initiated by aerosols in the focal volume [38][39][40]. Under normal conditions, there are more than 10 7 particles per mm 3 that are larger than 0.1 μm in the atmosphere [41].…”

Section: Breakdown In Gasesmentioning

confidence: 99%

Laser‐initiated ignition

Tauer¹,

Kofler

Wintner

2010

Laser & Photonics Reviews

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After an introduction illustrating the relevance and motivation of laser ignition of engines, the physical background is reviewed in a first technical section. This mainly comprises the mechanisms of plasma formation, which are the generation of first free electrons and their avalanche-like multiplication, being illustrated by emission and Schlieren diagnostics. Thereafter, combustion fundamentals are discussed leading to an understanding of flammability and minimum ignition laser energies. An important section is represented by the description of the components of laser ignition. This covers the setup and function of a diode-pumped passively Q-switched solid-state laser system, which preferentially is based on Nd:YAG. Other laser sources are mentioned for comparison. Furthermore, multiplexing schemes are discussed that are motivated by cost-saving issues. It is explained why present-day optical fibers are not capable of transporting nanosecond ignition pulses. As a last section, the concepts for an incoupling window and focusing optics are elucidated. Finally, after a summary, in an outlook the chances for commercial realization are analyzed.Sectional view of a prototype of a laser spark plug with an expanding flame kernel.

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Section: Breakdown In Gasesmentioning

confidence: 99%

Laser‐initiated ignition

Tauer¹,

Kofler

Wintner

2010

Laser & Photonics Reviews

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“…Laser-particle interactions are distinct and different from laser interactions with pure gases or bulk solids [1][2][3] and are of great importance in laser-based particle measurements 4 and material processing by laser irradiation. 5,6 Laser interactions with small particles are also used to produce nanoscale particles and control the particle size and morphology.…”

Section: Introductionmentioning

confidence: 99%

Photochemical Interaction of Polystyrene Nanospheres with 193 nm Pulsed Laser Light

et al. 2005

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The photochemical interaction of 193 nm light with polystyrene nanospheres is used to produce particles with a controlled size and morphology. Laser fluences from 0 to 0.14 J/cm 2 at 10 and 50 Hz photofragment nearly monodisperse 110 nm spherical polystyrene particles. The size distributions before and after irradiation are measured with a scanning mobility particle sizer (SMPS), and the morphology of the irradiated particles is examined with a transmission electron microscope (TEM). The results show that the irradiated particles have a smaller mean diameter (∼25 nm) and a number concentration more than an order of magnitude higher than nonirradiated particles. The particles are formed by nucleation of gas-phase species produced by photolytic decomposition of nanospheres. A nondimensional parameter, the photon-to-atom ratio (PAR), is used to interpret the laser-particle interaction energetics.

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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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The effect of dust on 10.6-μm laser-induced air breakdown

Cited by 145 publications

References 5 publications

Laser‐initiated ignition

Laser‐initiated ignition

Photochemical Interaction of Polystyrene Nanospheres with 193 nm Pulsed Laser Light

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

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