N In The Free Electron Laser Photon Compton Scattering Theory Research And Program Design

The core problem of the free electrons laser is the free electronic and optical fieldinteraction. With the development of laser technology, when relativistic free-electrons interactwith intense laser field in vacuum, some nonlinear phenomena begin to appear, which is quitedifferent from the ordinary Compton scattering, at that time the main mechanism of energyexchange is the nonlinear Compton scattering, in which the electron absorb multi-photon, andemit a new photon. Nonlinear Compton scattering leades the study of short-wavelength FEL toa completely new field.Two models are used to study free-electron–photon interaction mechanisms in this paper.One is using the method of standard perturbation theory, the intensity of optical field is ignored,and n photons are all absorbed; the other is considering the intensity of optical field, and usingthe semi-classical quantum electrodynamics. This paper consists of five chapters:Chapter1, we give a brief introduction of the development, applications and the trend ofthe free electron laser. The development and current research state of multi-photonsphenomenon is summarized.In chapter2, we use the standard perturbation theory to research the characteristics ofscattered photon frequency and electron energy change by n-photon group model, and discussthe situation under extremely low frequency condition in depth by writing programs, thendeduce differential scattered cross-section in the electron rest frame, at last we get theexpression in the laboratory frame through the Lorentz transformation. It is concluded that, thevalue of the scattered photon frequency and electron energy change are proportional to thenumber of the incident photons. The angular distribution of the scattered photon frequency andelectron energy change are drawn in the program, and through changing the value of thevariables continuously, we can conclude that, the normalized velocity of electron controls thesharpness of the graph, and the incidence angle of the n-photon and electron controls thescattering angle corresponding to the peak of the scattered photon frequency, when scatteredphoton frequency obtain the maximum, the azimuth equel to0. The differential cross-sectionderived is related to the scattering angle, azimuth and the initial conditions, and it isproportional to the (n-1)th power of number density of the incident photon.In chapter3, we use the semi-classical method to analyze the scattered photon frequencyand electron energy change in the process of n-photon nonlinear Compton scattering, and writeprograms to draw the angular distribution of the scattered photon frequency and electron energychange under extremely low frequency condition. Then introduce the quantum electrodynamics theory of motion of an electron, and analyze the character of the differential cross-section in anintense plane electromagnetic wave field with circle polarization. It is concluded that, thescattered photon frequency and electron energy change are related to the scattering angle,azimuth and the initial conditions, and they are proportional to the number of the incidentphotons. In the program, the normalized velocity of electron controls the sharpness of the graphand the incidence angle of the n-photon and electron controls the scattering angle correspondingto the peak of the scattered photon frequency, and the intense of optical field is both affects. Thedifferential cross-section is related to initial conditions and scattering direction.In chapter4，we compare the two model above. It is concluded that, to get shortwavelength free electron laser, we should let scattering angle tends to180, and let azimuthtends to0or180, in addition, proper incidence angle and intense of optical field are bothrequired.In chapter5, we summarize the main results from this paper and illustrate the importantrole of multi-photon scattering on the development of short wave light source and free electronlaser.