Relativistic Dynamics Of Electrons And Related Radiation Emission In Near-QED Regime

Laser-matter interaction has attracted intense concentration and been under broad research in physics.In recent years,with the rapid development of laser technologies,laser intensities in excess of 1022W/cm2 and pulse duration about several femtoseconds(fs)have been demonstrated in experiments.By revolutionary advances in laser technology marked by ongoing PW-class lasers such as Extreme Light Infrastructure(ELI),and International center for Zetta-Exawatt Science and Technology(IZEST),laser intensity is expected to surpass 1024~26W/cm2 in the near future.At such extreme laser intensities,the laser-matter interaction becomes highly nonlinear and enters a new unexplored near-quantum electrodynamics(near-QED)regime,which opens up new possibilities to study heavy ion acceleration,radiation dynamics,energetic radiation source,high field astrophysics,and QED effects,etc.In the near-QED regime,the classical behavior of particles is significantly modified.Relativistic electrons quivering in an ultra-intense laser field emit strong radiation,and the radiation field is sufficiently strong to act back on the electron itself.There is abundant electron-positron pair creation in the collision of two photons.This dissertation is devoted to study the ultra-intense laserplasma interaction in near-QED regime,especially on the electron dynamics and related radiation emission,such as the radiation reaction,energetic ?-ray emission,and electronpositron pair creation.The main contents are given as follows:Firstly,the laser-plasma interaction and electron dynamics in the near-QED regime is examined.When the radiation damping force becomes significant enough to compensate for the laser ponderomotive force,the laser-plasma interaction experiences a great deal of corrections.Based on an approachable laser intensities in current laboratories,we propose a new scheme to study relativistic electron dynamics and radiation reaction effect by ultra-intense laser interaction with a near-critical-density(NCD)plasmas filled gold cone.By using the QED-PIC code EPOCH,it is found that,considering the effect of large radiation damping force,some electrons are kicked into the laser field instead of being scattered off by the laser ponderomotive force.The trapped electrons oscillate significantly in the transverse direction and emit high-energy ? photons in the forward direction.In the scheme,the threshold laser intensity for electron trapping is significantly decreased,and the electron trapping and high-energy ?-ray emission are greatly enhanced.The proposed scheme may provide possibilities to demonstrate the radiation reaction effect and study the ?-ray source in experiments at approachable laser intensities.Secondly,we propose a new scheme as a ultra-bright,high-energy-density ?-ray source.In the simulation of an ultra-intense laser irradiating an NCD plasma filled conecapillary,a high-energy-density ? photon beam is produced with the total flux with the photon energy in the range of 3 MeV to 30 MeV approximately 1013/shot and the corresponding peak brightness being in the order of 1023photons/s/mm2/mrad2/0.1%BW.Moreover,the corresponding energy-density of the ? photons is about 1017J/m3,which is six orders of magnitude higher than the threshold,1011J/m3,for high-energy-density physics(HEDP).Compared with conventional high-energy ? radiation schemes,based on the laser-plasma interaction,the radiation source has many advantages such as low expense,compact source size,fs pulse duration,large photon flux,and high peak spectral brightness,which is expected to be applied in the laboratory astrophysics,high field nuclear physics,HEDP,etc.Thirdly,by studying the multiphoton Breit-Wheeler(BW)process in the highenergy ? photon interaction with ultra-intense laser field,a new scheme of generating extreme dense energetic positron beam is proposed.It is found that,by using two counterpropagating intense lasers irradiating an NCD plasma filled counter-cone target,high energy density ? photons with a density up to tens-9)c-class and an energy above GeVs are emitted.Due to the enhanced pinching and focusing effect of the cone,the peak electric field amplitude of the focused laser is more than five times higher than the peak value of the initial laser electric field.Trapped electrons oscillate significantly in the transverse direction in the focused laser field and emit high energy density ? photons.Pair creation is triggered via multiphoton BW process and extreme dense energetic positrons are emitted.In our scheme,the required laser intensity for dense pair creation is decreased by 107 compare with the spontaneous creation of pairs out of vacuum corresponding to the laser intensity as given by Schwinger.Extreme dense energetic positrons can be obtained via our scheme at approachable laser intensities,which opens up the opportunity to study extreme light field and explore various astronomical phenomena in current laboratories.