In this thesis electron generation is studied via laser plasma interaction known as laser wakefield acceleration in two regimes of weakly relativistic and highly relativistic laser intensity regimes. The plasma targets consisted of gas jets photonionized by rising edge of the laser pulse to densities as high as 10^20cm3. In the weakly relativistic regime, 210 mJ at 33 fs were focused to intensities of up to 310^18 Wcm2 on the gas targets of 2.4 mm length. In the highly relativistic regime, 3 J of energy compressed in 30 fs were delivered at intensity as high as 6.5 10^18 Wcm2 on targets of 2.4, 5, and 10 mm. Monoenergetic electrons in tens of MeV were observed in weakly relativistic regime, while electron energies as high as 300 MeV were observed in highly relativistic regime. Higher input laser intensity and prepulse levels were found to enhance electron production. Scaling of energy and stability of electron generation were also studied. / Photonics and Plasmas

No description available.

A numerical model was developed to understand the time evolution of a wake structure around a CubeSat moving in a plasma with transonic speed. A cubeSat operates in the F2 layer of ionosphere with an altitude of 300 − 600 Km. The average plasma density varies between 10−6cm−3 − 10−9cm−3 and the temperature of ions and electrons is found between 0.1−0.2 eV. The study of a wake structure can provide insights for its effects on the measurements obtained from space instruments. The CubeSat is modeled to have a metal surface, which is a realistic assumption, with a negative electric potential. To solve the equations of plasma, the numerical difference equations were obtained by discretizing the fluid equations of the plasma along with nonlinear Poisson’s equation. The electrons were assumed to follow the Boltzmann’s relation and the dynamics of ions was followed using the fluid equations. The initial and boundary conditions for the evolution of the structure are discussed. The computation was compared to the analytical solution for a 1D problem before being applied to the 2D model. There was a good agreement between the numerical and analytical solution. In the 2D simulation, we observe the formation of plasma wake structure around the CubeSat. The plasma wake structure consists of rarefaction region where ion density and ion velocity decreases compared to the initial density and velocity.