Effects of Transverse Bunch Size of the Precursor Electron Beam on Quasi-Phase Matched Direct Laser Electron Accelerations
Chia-Ying Hsieh1*, Ming-Wei Lin2, Yao-Li Liu1, Shih-Hung Chen1, Igor Jovanovic2
1Physics, National Central University, Jhongli, Taiwan
2Mechanical and Nuclear Engineering, The Pennsylvania State University, Pennsylvania, USA
* presenting author:Chia-Ying Hsieh, email:au03wu03@gmail.com
Direct laser acceleration (DLA) of an electron bunch can be achieved by utilizing a well-guided radially polarized laser pulse in a density-modulated plasma waveguide. However, the laser ponderomotive force excites plasma waves, which generate electrostatic fields to deteriorate the transverse properties of the injected bunch. To improve the bunch quality after DLA, a precursor electron bunch is injected in advance for inducing a focusing electrostatic field in the background plasma that can reduce the expansion of the accelerated bunch electrons. However, the precursor electron bunch expands during the acceleration process so that the focusing force decreases accordingly. With a fixed charge number, selected transverse sizes of the precursor are assigned in particle-in-cell simulations to investigate the expansion of the precursor and optimize the final property of the accelerated bunch. Results confirm that effectively improved transverse quality of the accelerated bunch when a precursor is introduced in DLA.

Keywords: Direct laser acceleration, Radially polarized laser pulse, Density-modulated plasma waveguide, Particle-In-Cell Simulations