Electron Acceleration And X-ray Radiation Generated From Laser Wakefield

In recent years,as a novel acceleration technology,the laser wake-field electron acceleration(LWFA)has received widespread attention due to its advantages such as extremely high accelerating gradients,compact structure and low cost,which promising future application of compact electron accelerators and tabletop X-ray sources.This thesis mainly introduces an experimental platform specially designed for the study of LWFA and X-ray sources.We use this platform to study in detail the scheme for accelerating the high-quality electron beam and explore the effective approach of ultra-fast X-ray source.The paper is mainly divided into the following four sections.Section one is the introduction which briefly represents the fundamental concept and the development of LWFA.Then we focus on the generation of X-ray sources based on LWFA:inverse Compton scatter and Betatron radiation.The radiation properties of the two X-ray sources are deduced based on the classical synchrotron radiation model.The second part presents the design and construction of the LWFA platform.Firstly,the design of the accelerator parameters are elaborated according to the current world's mainstream acceleration schemes.Then we show the various components of the acceleration platform we built.The third section describes the method for improving electron beams quality in different acceleration schemes.Firstly,we present the different characteristics of electron beams in self-injection scheme at different initial laser intensity.We found they will eventually reach the same matching focal spot size when two laser pulses with different initial focal spot and same power are propagating in the same density plasma.The laser with large initial focal spot is conducive to stable transmission in plasma,result in the improvement of the electron beams quality.Then LWFA in nitrogen gas via ionization injection is introduced.The influence of global optimization on the electron beam properties was studied.Electron beams with good stability in pointing,beam charge and energy spectrum were generated through global optimization.Next,we present a solution that we can achieve quasi-mono-energetic electron beams from pure nitrogen gas via ionization injection by designing laser and plasma parameters.Finally,we studied the influence of the chirp pulse on the evolution of the laser propagated in the plasma.We found that the chirp pulse not only help to improve the stability of the electron acceleration,but also has a significant effect on increasing the critical energy of the Betatron radiation.In fourth part,we present a systematic investigation on tabletop Inverse Compton Scattering(ICS)hard X-ray source based on the self-synchronized combination of laser-driven pure nitrogen plasma accelerator and plasma mirror.In pure nitrogen medium and ionization induced injection scheme,the LWFA is performed at a lower laser intensity and a lower plasma density that lead to lower evolutive beam profile and higher energy transmission rate after LWFA.We found the quality of electron beam is insensitive to focus position of the laser pulse with respect to gas jet,so the scattering can occur at the focus position,resulting in a dramatic increase in X-ray photon yield.Ultimately,the produced TS X-rays has the yield of 4.5×10~7.The photon number exceeding 200 keV is about 1.2×10~7.