Ion-Focusing Induced by a Precursor Electron Bunch in Quasi-Phase Matched Direct Laser Acceleration
C.-Y. Hsieh1*, M.-W. Lin2, I. Jovanovic3, S.-H. Chen1
1Department of Physics, National Central University, Jhongli, Taiwan
2Institute of Nuclear Engineering and Science, National Tsing Hua University, Hsinchu, Taiwan
3Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, USA
* presenting author:Chia-Ying Hsieh,
Quasi-phase matched direct laser acceleration (DLA) of electrons can be achieved by guiding a radially polarized laser pulse in a plasma waveguide. However, the ponderomotive force of a TW laser pulse perturbs the plasma electrons to generate an electrostatic field, which significantly defocuses the electrons of the witness bunch throughout the acceleration process. To improve the performance of DLA, a leading precursor electron bunch is applied to induce an ion channel in the plasma and reduce the divergence of witness bunch. Our three-dimensional particle-in-cell simulations show that the bunch charge and the transverse size of a precursor are the dominating factors affecting the performance of the ion-focusing effect. Once a favorable ion-focusing force is provided by the precursor, the transverse properties of witness bunch can be maintained and the overall DLA efficiency can be improved.

Keywords: Direct Laser Acceleration, Quasi-Phase Matched method, Ion-Focusing Force, Particle-In-Cell Simulations