A numerical investigation of the dependence of the threshold irradiance on the wavelength in laser-induced breakdown in

Gamal, Yosr E. E.-D.; Shafik, M S; Daoud, Jamal M

doi:10.1088/0022-3727/32/4/012

Cited by 15 publications

(5 citation statements)

References 14 publications

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“…Also, over the energy range 5-8 eV, the electron energy distribution function for λ = 266 nm showed the highest value, while the lowest value was found to correspond to the wavelength 355 nm. This was attributed to the high vibrational losses associated with the latter laser wavelength as explained in our recent paper (Gamal et al 1999).…”

Section: Resultsmentioning

confidence: 52%

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Influence of secondary ionization processes on the breakdown of nitrogen by a wide range of laser wavelengths

Gamal

Abdelatif

2000

J. Phys. D: Appl. Phys.

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Following the modified model used in our previous paper for the study of laser-induced breakdown of molecular nitrogen, in this work we present the influence of secondary ionization processes on the breakdown phenomenon. The analysis is based on the calculation of the electron energy distribution function and its parameters for laser wavelengths covering the range 266-1064 nm, in irradiated molecular nitrogen at atmospheric pressure. The result of computations revealed that no evidence is observed for collision and photoionization processes of ground-state molecules. Under the experimental conditions applied in this analysis, collision processes lead only to the population of excited states. Breakdown of nitrogen at laser wavelengths 532, 355 and 266 nm proceeds totally via photoionization of the excited states. For = 1064 nm, electron growth is obtained due to multi-photoionization of the excited states, in addition to the contribution of collisional ionization of these states.

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Section: Resultsmentioning

confidence: 52%

“…This electron is presented by a Gaussian energy distribution, centred at 4 eV. The cross sections and rate coefficients for the inelastic processes considered in this work are taken from the same sources given in our recent paper (Gamal et al 1999).…”

Section: Theorymentioning

confidence: 99%

Influence of secondary ionization processes on the breakdown of nitrogen by a wide range of laser wavelengths

Gamal

Abdelatif

2000

J. Phys. D: Appl. Phys.

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“…where the photoionization cross section σ is set as 10 −17±1 cm 2 , [16,19] ν is the frequency of the laser beam, and hν refers to the energy of the single photon. The second term in Eq.…”

Section: Theoretical Modelmentioning

confidence: 99%

Transmission effects of high energy nanosecond lasers in laser-induced air plasma under different pressures

Yin

Wang

et al. 2023

Chinese Phys. B

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When a high energy nanosecond (ns) laser induces breakdown in the air, the plasma density generated in the rarefied atmosphere is much smaller than that at normal pressure. It is associated with a relatively lower absorption coefficient and reduces energy loss of the laser beam at low pressure. In this paper, the general transmission characterizations of a joule level 10 ns 1064 nm focused laser beam are investigated both theoretically and experimentally under different pressures. The evolution of the electron density (n e ), the changes in electron temperature (T e ) and the variation of laser intensity (I) are employed for numerical analyses in the simulation model. For experiments, four optical image transfer systems with focal length (f) of 200 mm are placed in a chamber and employed to focus the laser beam and produce plasmas at the focus. The results suggest that the transmittance increases obviously with the decreasing pressure and the plasma channels on the transmission path can be observed by its self-illumination. The simulation results agree well with the experimental data. The numerical model presents that the maximum n e at the focus can reach 1019 /cm3, which is far below the critical density (n c ). As a result, the laser beam is not completely shielded by the plasmas.

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“…The goal is to identify the most promising range of parameters to guide selection of experimental conditions. The photon energy of the laser at the wavelength 1064 nm is only 1.1eV, 77 which is too low to interact directly with the nitrogen atmosphere inside the chamber, which has an ionization energy of 15.6 eV and a dissociation energy of 9.8 eV. 78 The laser intensity is low enough that gas breakdown cannot occur, which needs a threshold intensity of 3x 10 10 W/cm 2 .…”

Section: Experimental Details a Fluence Range To Be Exploredmentioning

confidence: 99%

Laser Processing of Metals and Polymers

Singaravelu

2012

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A laser offers a unique set of opportunities for precise delivery of high quality coherent energy. This energy can be tailored to alter the properties of material allowing a very flexible adjustment of the interaction that can lead to melting, vaporization, or just surface modification. Nowadays laser systems can be found in nearly all branches of research and industry for numerous applications. Sufficient evidence exists in the literature to suggest that further advancements in the field of laser material processing will rely significantly on the development of new process schemes. As a result they can be applied in various applications starting from fundamental research on systems, materials and processes performed on a scientific and technical basis for the industrial needs. The interaction of intense laser radiation with solid surfaces has extensively been studied for many years, in part, for development of possible applications. In this thesis, I present several applications of laser processing of metals and polymers including polishing niobium surface, producing a superconducting phase niobium nitride and depositing thin films of niobium nitride and organic material (cyclic olefin copolymer).The treated materials were examined by scanning electron microscopy (SEM), electron probe microanalysis (EPMA), atomic force microscopy (AFM), high resolution optical microscopy, surface profilometry, Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD). Power spectral density (PSD) spectra computed from AFM data gives further insight into the effect of laser melting on the topography of the treated niobium. I owe my deepest gratitude to Dr. J. Michael Klopf from FEL team, who was beside me supporting my experiments. Any discussion I had with him has always been informative and helpful. Thanks for his encouragement and patience. He faced the challenge of a demanding student as I was. Eventually my progress will inspire many more research students to seek his fortunate advice and guidance. I wish to thank Dr. Shukui Zhang from FEL team for training and teaching me the laser system. I can never forget the timely help rendered by Dr. Gwyn Williams, Dr. Steve Benson, Dr. Jim Coleman, Cody Dickover, Chris Gould, Joe Gubeli, Kevin Jordan, Jim Kortze, Dan Sexton, Dr. Michelle Shinn, Dr. Richard Walker, Tom Powers and Guy Wilson, during my stay in FEL building by providing all the help I requested for.

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A numerical investigation of the dependence of the threshold irradiance on the wavelength in laser-induced breakdown in

Cited by 15 publications

References 14 publications

Influence of secondary ionization processes on the breakdown of nitrogen by a wide range of laser wavelengths

Influence of secondary ionization processes on the breakdown of nitrogen by a wide range of laser wavelengths

Transmission effects of high energy nanosecond lasers in laser-induced air plasma under different pressures

Laser Processing of Metals and Polymers

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