Energy Absorption And ?-ray Emission In The Intense Laser-plasma Interaction

?-rays are electromagnetic radiation with extremely high frequency and photon energy.As a promising radiation source,?-rays have a wide range of applications in materials science,nuclear physics,astrophysics,industry,cancer treatment and other fields.When the laser intensity reaches the magnitude of 10²²Wcm^-2,the interaction between laser and plasma will enter the quantum electrodynamics region.When the high intensity laser propagates in the plasma,the electrons in the plasma are accelerated to a high energy by ponderomotive force of the laser,and emit high energy gamma photons through nonlinear oscillation.In laser plasma interaction,laser energy absorption mechanism mainly depends on plasma temperature,density and laser intensity.In this paper,the nonlinear QED phenomena such as laser energy absorption,radiation damping effect,high energy and bright?ray generation in the interaction between intense laser and plasma are studied by theoretical and two-dimensional(2D)particle in-cell simulation(PIC)method.This paper includes the following main contents:In the first part,briefly introduces the development history of laser technology and the basic physical process of laser plasma interaction.The nonlinear QED phenomena such as radiation reaction effect and?-ray generation are described in detail.The common laser energy absorption mechanism in laser plasma interaction is described in detail.Finally,the PIC simulation method used in this paper is briefly introduced.In the second part,the influence of quantum electrodynamics effect on laser energy absorption in the interaction of intense laser and plasma is studied theoretically.The effects of electron motion characteristics,dispersion relations and radiation damping on laser energy absorption under classical and QED conditions are discussed,respectively.The complete analytical expressions of electron motion in electromagnetic field are given in both classical and QED cases,and the theoretical models related to radiation damping,electromagnetic frequency,critical density and laser intensity are established.The results show that the radiation damping effect has a great influence on the electron motion.Compared with the classical case,the strong radiation damping in the QED case leads to the strong absorption of laser energy.The change of electron energy in the case of QED is more realistic.In the third part,an all-optical scheme for producing bright gamma rays is presented by using 2D-PIC simulation method.Three different target structures were used in the simulation to study the influence of target shape on?-ray production.The simulation results show that,compared with the other two targets,target 3 has better focusing effect on both the incident and reflected laser fields,and reduces the divergence angle of?photons.In the case of target 3,the gamma rays with peak brightness of10²⁶photons/s/mm²/mrad²/0.1%BW(100Me V)and 10²³photons/s/mm²/mrad²/0.1%BW(2Ge V)are obtained at a laser intensity of 8.5×10¹²Wcm^-2 when the plasma density is equal to the critical plasma density n_c.In addition,the effects of plasma channel length,target curvature radius,laser polarization,laser intensity and radiation reaction effects on?-ray generation are also discussed,and their optimal parameters are given through a series of simulation calculations.The high energy and bright?-rays obtained in this paper provide a reference value for the generation of high energy positron and negative electron pairs and the experiment of obtaining high energy and bright?-ray source.In the fourth part is the summary of the full text and the prospect of the future work.