Research On The Novel Injection Methods In Laser Wake-field Electron Acceleration

In recent three decades, with the rapid development of ultra-intense short laser pulse technology and the great progress on laser plasma interaction, laser wake-field accelerator (LWFA) has become one of the most attractive research area in high field science, and is likely to become the novel tabletop-accelerator in the near future. Since electron injection is an critical process in laser wake-field electron acceleration, and several schemes to realize or enhance the electron injection have been proposed according to the characteristics of the LWFA. We also studied several electron injection process for each scheme by particle in cell (PIC) code. The main content includes that:Firstly, we proposed a scheme to enhance the electron injection by two parallel-propagating coaxial non-synchronous laser pulses. The results showed that the two laser pulses can enhance the electron injection due to the wake-field expanding. The injected-electron number is almost two times higher than that in a single laser pulse case with the same total laser energy. This scheme can be optimized by adjusting the spot size, the interval and the polarization of the two pulses.Secondly, we proposed another two schemes to realize the electron injection by two parallel-propagating non-coaxial and non-synchronous laser pulses in non-bubble situation and electron bow wave situation. The simulation results show that the schemes are viable.Lastly, a scheme to enhance the electron injection in one-dimension space by two laser pulses is proposed, basing on the theory of laser ponderomotive force accelerating electrons. We obtained the minimum velocity of the electrons entering the laser pulse accelerating front and the final velocity increment in theory. The simulation shows that the electron injection in two laser pulses case has a great advantage comparing to that in single laser pulse case, which have much higher energy and lower energy spread.