skip to main content

Title: On the study of threshold intensity dependence on the gain and loss processes in laser induced spark ignition of molecular hydrogen

In the present work, a numerical analysis is performed to investigate the comparative contribution of the mechanisms responsible for electron gain and losses in laser spark ignition and plasma formation of H{sub 2}. The analysis considered H{sub 2} over pressure range 150 -3000 torr irradiated by a Nd:YAG laser radiation at wavelengths 1064 and 532 nm with pulse length 5.5 ns. The study based on a modified electron cascade model by one of the authors which solves numerically the time dependent Boltzmann equation as well as a set of rate equations that describe the rate of change of the excited states population. The model includes most of the physical processes that might take place during the interaction. Computations of The threshold intensity are performed for the combined and separate contribution of each of the gain and loss processes. Reasonable agreement with the measured values over the tested pressure range is obtained only for the case of the combined contribution. Basing on the calculation of the electron energy distribution function, the determined relations of the time evolution of the electrons density for selected values of the tested gas pressure region revealed that photo-ionization of the excited states could determine the time of electronmore » generation and hence spark ignition. Collisional ionization contributes to this phenomenon only at the high pressure regime. Loss processes due to electron diffusion, vibrational excitation are found to have significant effect over examined pressure values for the two applied laser wavelengths.« less
Authors:
;  [1] ;  [2]
  1. Department of physics, Faculty of Science, Cairo University, Giza (Egypt)
  2. National Institute of Laser Enhanced Sciences, Cairo University, Giza (Egypt)
Publication Date:
OSTI Identifier:
22391327
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1653; Journal Issue: 1; Conference: APMAS 2014: 4. International Congress in Advances in Applied Physics and Materials Science, Fethiye (Turkey), 24-27 Apr 2014; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BOLTZMANN EQUATION; CALCULATION METHODS; DIFFUSION; ELECTRON DENSITY; ELECTRONS; ENERGY SPECTRA; EXCITATION; EXCITED STATES; GAIN; HYDROGEN; IRRADIATION; LASER RADIATION; LASER-PRODUCED PLASMA; NEODYMIUM LASERS; NUMERICAL ANALYSIS; PHOTOIONIZATION; PLASMA PRESSURE; PLASMA SIMULATION; PRESSURE DEPENDENCE; TIME DEPENDENCE