Spectroscopic investigation of laser-initiated low-pressure plasmas in atmospheric gases

Armstrong, R. A.; Lucht, R. A.; Rawlins, W. T.

doi:10.1364/ao.22.001573

Cited by 36 publications

(13 citation statements)

References 10 publications

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“…In order to avoid wavelength shift due to off angle incident beam, a f/8 or f/9 system is required. The net radiance in this case is Ncvf = tcvf(l/ 16 f/#2)Np = 2-3xlO- 4 Np.…”

Section: 7mentioning

confidence: 96%

“…Previously [4] the pulse shape of the laser has been measured to be spikey in normal operation with no etalon in the oscillator cavity. The pulse width given ,, specification is 10 nsec.…”

Section: *#mentioning

confidence: 99%

“…Preliminary modelling of the kinetic effects has been described in detail (4]. The initial concentrations assumed, based on energetics, are 80% 0+, 15% 0 and 5% 0 The reaction set, which includes recombination and reionization, is shown in and with the lowest charged state observed (i.e.…”

Section: Kinetic Effectsmentioning

confidence: 99%

“…Initial Parameters Historically [4,5,6], the focal length of the lens used in the experiment has been reported to be 5.6 to 5.8 cm and the laser power absorbed is -10 %. Recent measurements in a new configuration [7] show that the focal length is 4.1 cm and the laser power absorbed is -40 %.…”

mentioning

confidence: 99%

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Investigation of Laser-Induced Plasma Processes.

Ip¹,

Armstrong²,

Baird³

1986

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“…In order to avoid wavelength shift due to off angle incident beam, a f/8 or f/9 system is required. The net radiance in this case is Ncvf = tcvf(l/ 16 f/#2)Np = 2-3xlO- 4 Np.…”

Section: 7mentioning

confidence: 96%

“…Previously [4] the pulse shape of the laser has been measured to be spikey in normal operation with no etalon in the oscillator cavity. The pulse width given ,, specification is 10 nsec.…”

Section: *#mentioning

confidence: 99%

Section: Kinetic Effectsmentioning

confidence: 99%

mentioning

confidence: 99%

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Investigation of Laser-Induced Plasma Processes.

Ip¹,

Armstrong²,

Baird³

1986

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“…8 , 9 Implicit in this relation is the assumption that the gas remains at a xed temperature. Typically, this has been a valid assumption because the majority of the experimental investigations of laserinduced breakdown seem to have been made in xed-volume, uninsulated test cells where the gas is at ambient temperature (see, for example, Armstrong et al 8 or Dewhurst 10 ). That the threshold intensity is actually a function of the gas density may be seen in the report by Grey Morgan, 5 where the threshold intensity is expressed in terms of the neutral molecule concentration for both ionization mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Laser-Generated Localized Freestream Perturbations in Supersonic and Hypersonic Flows

2000

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An optical method for generating localized, controlled perturbations has been developed for use in supersonic and hypersonic ow elds. The thermal spot disturbance is generated when the pulsed beam from a laser is focused at the desired origin and a small region of the gas is ionized. After recombination, the thermal spot persists as a region of heated gas that convects with the local ow velocity. The perturbation is approximately spherical and several millimeters in diameter, with the size dependent on the ow density. Optimal formationof the perturbation is achieved with large-F-number focusing systems. To date, the disturbancehas been used as a freestream perturbation for supersonic receptivity experiments as well as forward-facing cavity and blunt-body shock oscillation studies.

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Laser‐Induced Plasmas for Broadband Cavity‐Enhanced Absorption Spectroscopy

Keary¹,

Ruth²

2020

Encyclopedia of Analytical Chemistry

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The combination of cavity‐enhanced absorption spectroscopy (CEAS) with the phenomenon of laser‐induced breakdown has yielded a variation of CEAS in which the emission from a laser‐induced plasma (LIP) is utilized as a pulsed incoherent broadband light source in the center of a high‐finesse optical cavity. In comparison to standard CEAS implementations, this approach places light directly inside the resonator without injection through the cavity mirrors. The broadband optical emission from the pulsed LIP facilitates the measurement of spectra through (i) time‐dependent cavity ring‐down spectroscopy (CRDS) and (ii) intensity‐dependent incoherent broadband cavity‐enhanced absorption spectroscopy (IBBCEAS) methodologies. Additionally, from the broadband ring‐down time of light within the cavity, cavity mirror reflectivities may be calibrated in situ, thus enabling absolute extinction coefficient measurements with IBBCEAS. The IBBCEAS approach possesses numerous advantages over the CRDS approach in terms of measurement speed and achievable signal‐to‐noise ratios (SNRs). However, it is limited by the presence of an offset in the measured absorption that arises due to the absorption of light that occurs between LIP formation and commencement of data collection. This offset motivated the development of a numerical correction procedure which allows spectra measured in this way to be corrected to improve their overall accuracy.

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Spectroscopic investigation of laser-initiated low-pressure plasmas in atmospheric gases

Abstract: 1A 5L 4. TITLE (sVndtSubtlel.) S1. TYPE OF REPORT A PERIOD COVIRED SPECTROSCOPIC INVESTIGATION OF Scientific. Interima.

Cited by 36 publications

References 10 publications

Investigation of Laser-Induced Plasma Processes.

Investigation of Laser-Induced Plasma Processes.

Laser-Generated Localized Freestream Perturbations in Supersonic and Hypersonic Flows

Laser‐Induced Plasmas for Broadband Cavity‐Enhanced Absorption Spectroscopy

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