Document Details

Document Type : Thesis 
Document Title :
Studying the Role of the Physical Processes Responsible For the Breakdown of Molecular Oxygen Gas by Laser Radiation:
دراسة دور العمليات الفيزيائية المسؤولة عن انهيار غاز الأكسجين الجزيئي بأشعة الليزر: نمذجة عددية
 
Subject : Laser beams 
Document Language : Arabic 
Abstract : This work presents a study on the breakdown of molecular oxygen by a Nd: YAG laser source operating at the wavelengths 1064 nm and 532 nm with a pulse duration of 5.5 ns over a gas pressure range varies between 190-3000 torr, to determine the threshold intensity for gas breakdown as a function of both gas pressure, and laser wavelength. More over , this study is also aimed to determine the physical processes responsible for the breakdown phenomenon. In doing so a numerical model is applied which was previously developed by Evans and Gamal (1980).This model is refined to take into account most of the physical processes which might take place during the interaction between the laser beam and the oxygen molecules (Gamal and Omar, 2001). The computations are devoted to investigate the experimental measurements that was carried out by Phuoc (2000), to study the breakdown phenomenon of oxygen gas as one of the most important constituent of atmospheric air. The model considers the inverse Bresstrahlung absorption as a process that leads to the gain of energy of free electrons from the electric field associated with the laser beam. In addition, it takes also into account electron collisional processes to excite neutral molecules as well as to ionize ground and excited molecules. Further more, the model considered the photo-ionization of the excited molecules. Comparison between the calculated thresholds and the measured ones determine the validity of the model in investigating the breakdown of oxygen under the experimental conditions applied in this analysis. While comparison of the calculated Electron Energy Distribution Function (EEDF) and its parameters (i.e. the time evolution of the electron density, the variation of the mean electron energy, the variation of the ionization and excitation rates…etc) at different values of the gas pressure determine the physical processes responsible for gas breakdown. The calculations are carried out at the two values of the laser wavelength on the breakdown of oxygen. 
Supervisor : Yosr Ezz Eldin Gamal 
Thesis Type : Master Thesis 
Publishing Year : 1431 AH
2010 AD 
Number Of Pages : 208 
Added Date : Tuesday, March 11, 2014 

Researchers

Researcher Name (Arabic)Researcher Name (English)Researcher TypeDr GradeEmail
مها محمد بادحدح. Badahdah, maha MohammadInvestigatorMaster 

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 36686.pdf pdf 

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