The Study Of The Electron Acceleration Characteristics Based On The Spherical Plasma Wave And Cylindrical Plasma Channel

The interaction between laser and plasma has aroused great interest of scientists due to its abundant physical phenomena and wide application prospects.One of the main characteristics of this field is the generation of the high-energy electrons.In order to improve the energy obtained by electrons from laser and then generate high-energy electrons,various electron acceleration schemes have been proposed and developed.Through the continuous efforts of people,the energy record of electrons is also constantly refreshing.At present,the highest electron energy obtained in the experiment is 7.8 GeV.However,as far as the existing acceleration schemes are concerned,they have their own advantages and disadvantages.There are still many problems in the field of the electron acceleration,which prevent people from further improving the energy and quality of the electrons.New acceleration mechanisms and solutions still need to be explored.Based on the spherical plasma wave and cylindrical plasma channel,this paper mainly studies the characteristics of electron acceleration,which provides some theoretical guidance for experiments.This thesis consists of two parts,one is about the ladder climbing(LC)and autoresonant(AR)acceleration of the spherical plasma wave,the other is about the relativistic electron characteristics driven by laser in the cylindrical plasma channel.In the first part,based on the hydrodynamic model of the collisionless electron plasma,the governing equation of the perturbed spherical density wave in the energy level space is given for the first time,and it is demonstrated that the quantum ladder climbing and classical autoresonant transition can be achieved in the spherical plasma.The asymptotic thresholds of the ladder climbing and autoresonant transition of the spherical plasma wave are obtained analytically and verified numerically.We find that as the density wave climbs to a higher level,the energy of the spherical wave gradually is concentrated to the center of the sphere.The spherical plasma shows obvious compression characteristics,and the perturbed density at the center of the sphere can even be amplified to 100 times of the initial perturbed density.This kind of compression characteristic of the spherical plasma density wave is analogous to the implosion and compression processes in the inertial confinement fusion(ICF),therefore,our studies may provide a new idea for the implosion compression processes in ICF,for example,we can improve the compression efficiency by reasonably designing ladder climbing and autoresonant acceleration of the spherical plasma density wave.In the second part,in terms of a single-electron model of direct laser acceleration,we study the dynamics of the electron irradiated by a high-power laser pulse in a cylindrical plasma channel with a uniform positive charge density and negative current density.We find that the energy and trajectory of the electrons strongly depend on the positive charge density,negative current density in the plasma channel and laser pulse intensity.Due to the limitation of the dephasing rate between the wave and electron motion,the electrons can be effectively accelerated only when their values are in a suitable range.In particular,we find that when the values of them satisfy a critical condition,the electron can maintain the same phase with the laser and obtain the maximum energy from the laser.However,with the increasing of the electron energy,due to the strong modulation of the relativistic factor,the transverse oscillations of the electrons may become unstable,which will cause the instability of the electron trajectory,i.e.,with the increase of energy,the electron will essentially become a three-dimensional motion.This part of our work makes it possible to control the energy and stability of the electron by properly adjusting the positive charge density,negative current density of the plasma channel and laser pulse intensity.