Sharif Digital Repository

In this work we evaluate the interaction of high intense laser beam with a steepened density profile. During laser interaction with underdense plasma by freely expanding plasma regime, modification of density profile is possible. In this paper we have investigated the ultra short laser pulse interaction with nonisothermal and collisionless plasma. We consider self-focusing as an effective nonlinear phenomenon that tends to increase when the laser power is more than critical rate. By leading the expanded plasma to a preferred location near to critical density, laser reflection is obtained, so the density profile will be locally steepened. The electromagnetic fields are evaluated in this new... 

The electron acceleration in the bubble regime is considered during the laser-plasma interaction. The PIC and experimental results show that the obtained ellipsoid cavity model is more consistent than the spherical model. We prove the fields inside the cavity depend linearly on the coordinates and the spherical cavity is a special case of the ellipsoid model. The quasi mono-energetic electrons output beam tracing the laser plasma can be more appropriately described with this model. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim  

A warm relativistic ideal fluid theory is proposed to study the dynamics of laser-induced high amplitude longitudinal waves in rarefied plasmas. It is demonstrated that fluid equations may be closed using an adiabatic approximation in the local rest frame of the plasma fluid. It is shown that considering three-dimensional thermal fluctuations of plasma for an interacting laser pulse that is invariant in transverse directions, considerably changes the features of describing fluid equations compared to that of previously considered one-dimensional thermal-fluctuations models. For a given shape of laser pulse these equations are solved numerically and their results are compared with those... 

Using the ellipsoidal cavity model, the quasi-monoenergetic electron output beam in laser-plasma interaction is described. By the cavity regime the quality of electron beam is improved in comparison with those generated from other methods such as periodic plasma wave field, spheroidal cavity regime and plasma channel guided acceleration. Trajectory of electron motion is described as hyperbolic, parabolic or elliptic paths. We find that the self-generated electron bunch has a smaller energy width and more effective gain in energy spectrum. Initial condition for the ellipsoidal cavity is determined by laser-plasma parameters. The electron trajectory is influenced by its position, energy and...