Sharif Digital Repository

In this work, design and construction of copper vapor and Cu Br laser is explained. By special design of copper electrodes the average power from Cu laser system was increased more than 20% in comparison to the same system with expensive electrodes made from molybdenum. However, the basic goal of this work was the construction of CuBr laser. Based on the home made fast trigger unit for Hydrogen thyratron, operation of the manufactured system was possible up to 25 kHz. By using special designed copper electrodes very uniform operation of CuBr plasma diluted in Ne gas was observed. By tuning of the laser parameters such as gas pressure, exciting voltage and pulse repetition rate, from 9 Cm3 of... 

In this work we studied the interaction of a high frequency electromagnetic wave in under relativistic and relativistic regims with a plasma taking into account of the ponderomotive fo per unit volume acting on plasma electrons.In under relativistic regim at first we assumed the plasma is collisionless, unmagnetized and non isothermal which occupying the semi - space Z 0 .We found the nonlinear differential equation for the electric field using theMaxwell and hydrodynamic equations.We obtain the profiles of the electric and magnetic fields in plasma and we see that the electron density oscillations appear highly peaked. Then in this regim a direct one dimensional (1D) procedure for... 

In general cases, the generated electron beam with interaction of high intense and ultra short laser with gas plasma targets has large distributed energy spectrum (100%) that is called Quasi-maxwellian energy spectrum. Recently, in some experimental and 3D-PIC simulation results, a narrow band electron energy spectrum has observed that is called Quasi-monoenergetic electron. We approximated that these electrons have Gaussian distribution. High quality quasi-monoenergetic electron beam can focus in small spot. Therefore, there are many applications such as medical applications, crystallography with electron scattering, spectroscopy with soft energy and ultra fast x-ray, photonuclear... 

In this thesis, conversion of methane into heavier hydrocarbons was performed by nanoparticles-assisted nanosecond laser induced plasma. Nickel oxide nanoparticles was synthesized by sol-gel procedure and packed into a compact tablet after drying and used as a target in a two BK7 windows-camber with pressure of 1500 mbar. Methane was introduced to the chamber and two different nanosecond lasers namely, Nd:YAG (λ=1064 and 532 nm) and KrF (λ=248 nm) were radiated. Interaction of the gas with the plasma produced by metal nanoparticles and the thermionic emissions due to the inverse bremsstrahlung caused conversion of methane to the heavier hydrocarbons. These conversions can also promote by... 

Using plasma cluster in fusion has attracted many attentions in recent year. In this work, generating of hard X-ray with energy more than 10 keVby Ti-sapphire laser, 100 fs pulses’ duration and focal intensity of more than 1014W/cm2 has been discussed. Due to significant enhancement of X-ray production from metal nanoplasma cluster, a reasonable theoretical model is needed to describe the more than 10-fold increment of X-ray generation. Hence, the present models have been studied and a proper model based on available experimental data, has been presented. The X-ray, which is produced through this way, can be used in Inertial Fusion Confinement (ICF). One of the major obstacles in ICF is...