Influence Of An Electron Initial Incident Angle On Nonlinear Forward Thomson Scattering Under A Combined Field

Nonlinear Thomson scattering refers to the process in which the electron is accelerated to produce radiation in an ultra-intensity laser field.With the de-velopment of laser technology,ultra-short X-ray can be emitted in the process of nonlinear Thomson scattering caused by the interaction between the electron and ultra-intensity laser.It has many advantages,such as brightness is high-peak,good direction,adjustable energy and is useful in a number of fields including medi-cal imaging,femtochemistry and the process of interaction between ultra-short and ultra-intensity laser and matter.In the nonlinear Thomson scattering process,when the combined field of external magnetic field and laser field interacts with the elec-tron in a positive way,the existing research results show that the external magnetic field can cause the electron to be in a resonant state during the radiation process,and can effectively improve the energy obtained by the electron in the laser field.In the existing studies,it is assumed that the electron is stationary at the origin of coordinates or interact with the laser field along the propagation direction at the initial moment.However,the electron has a certain initial velocity,and there is a certain angular deviation from the propagation direction of the laser field in most experiments.In addition,when the combined field of different polarization laser interacts with the electron,the electron will have different radiation characteristics.Therefore,this thesis mainly studies two aspects,one is the influence of electron incidence angle on nonlinear Thomson scattering under linearly polarized laser and external magnetic field,the other is the influence of electron incidence angle on nonlinear Thomson scattering under circularly and elliptically polarized laser and external magnetic field.In the chapter 2,the nonlinear Thomson forward scattering of the electron is studied based on the model of a single electron with a linearly polarized laser and an external magnetic field,considering the influence of the initial incident angle.Giv-en the vector potential of the combined field,the differential equation of electron momentum is derived by using Maxwell’s equations and Lorentz equation,and the momentum and position of the electron is obtained from this equation,and finally the nonlinear Thomson forward scattering spectrum of electron is deduced.The conclusions are summarized as the following:1.In the process of interacting with the combined field,the motion of the electron is the superposition of two periodic motions,one of the periodic motions depends on the frequency of the laser field and the other depends on the cyclotron frequency of the electron in the external magnetic field.The superposition of the two periodic motions of the electron results in two peaks in the nonlinear Thomson forward scattering spectrum,the main peak is dependent on the frequency of the laser field(ω=1)and the magnetic peak is dependent on the cyclotron frequency(ω=ωb),and the radiation intensity of the main peak is much greater than the magnetic peak.2.The periodic motion depen-dent on the frequency of the laser field is independent of the initial incident angle of the electron,while the periodic motion dependent on the cyclotron frequency is related to the initial velocity of the electron,and when the initial velocity is given,it is related to the initial incident angle of the electron.When the initial incident direction of the electron deviates from the propagation direction of the laser,with the increase of the initial incident angle,the number of vibrations of the electron in the laser field increases in a cyclotron period,but the radiation intensity of the main peak and magnetic peak decreases rapidly.In order to obtain higher energies,the initial incident Angle of the electron should not exceed ±3°.3.When the electron is incident at a symmetric angle along the direction of laser propagation,its mo-mentum and trajectory have no symmetry,but the radiation energy has symmetry with respect to the radiation angle.In the chapter 3,based on the research in the chapter 2,we consider the influ-ence of the electron incidence angle on the nonlinear Thomson forward scattering in the combined field of circularly and elliptically polarized laser and external magnetic field.The results show that similar to the linearly polarized laser combination field in chapter 2.Under the combined field of circularly and elliptically polarized laser,the motion of electron is still the superposition of two periodic motions,the radi-ation spectrum also consists of two peaks,the main peak and the magnetic peak,and the energy of the main peak is far greater than the energy of the magnetic peak.In addition,when the initial incident direction of the electron deviates from the propagation direction of the laser,the radiation intensity of the main peak and magnetic peak decreases rapidly with the increase of the initial incident angle,and the radiation energy also has symmetry with respect to the radiation angle.The results also show that the radiation energy is the strongest when the electron is interacting with the linearly polarized laser combination field,the elliptically polar-ized laser combination field and the circularly polarized laser combination field are the weakest.When the initial incident direction of the electron deviates from the propagation direction of the laser,with the increasing of the initial incident angle of the electron,the radiation intensity of the main peak decreases the fastest in the cir-cularly polarized laser combination field,followed by the elliptically polarized laser combination field and the linearly polarized laser combination field,however,the rate of decrease of the magnetic peak radiation intensity is opposite to that of the main peak.Therefore,in order to obtain stronger radiation energy,the combined field of linearly polarized laser should be used to interact with the electron.