Effect of frequency-chirped ionization laser on accelerated electron beam characteristics in plasma wakefield acceleration

Abstract

Trojan Horse underdense photocathode plasma wakefield acceleration is an effective technique for generating ultralow-emittance electron bunches. In this study, we investigate the impact of frequency chirp in the ionization laser on the properties of the accelerated electron bunches using two-dimensional (2D) particle-in-cell (PIC) simulations. It is found that the total charge of the high-energy electrons produced in the acceleration process depends strongly on the magnitude and the sign of frequency chirp in ionization laser. For an un-chirped ionization laser, an electron bunch gets a maximum acceleration of up to 400 MeV with bunch current \(I_{p} \sim 0.27{\text{kA}}\). However, the use of a negative-chirped ionization laser shows lower energy gain, i.e., 200 MeV with an enhanced bunch current \(I_{p} \sim 5{\text{kA}}\), with normalized emittance \( \varepsilon _{n} \sim 0.78\;\mu m \) in 7.5-mm-long plasma channel. Such high current electron bunches will be useful for compact hard X-ray free-electron laser (FEL) sources.