Pulse-length Effect on Laser Wakefield Acceleration of Electrons by Skewed Laser Pulses

Abstract

Laser pulse-length-related control and optimization of electron acceleration from laser wakefield acceleration (LWFA) by a shaped laser pulse is proposed to investigate in this study. The laser pulse shape changes and becomes skewed due to the variation in refractive index during propagation in plasmas. The optimum laser pulse-length for excitation of plasma wave in linear regime $(a_{0} is $\tau _{L}=\lambda _{p} / \sqrt {2\pi c} $ , but, in nonlinear regime $(a_{0}>1)$ , is not quite certain. Here, laser strength parameter $(a_{0})$ is defined as the ratio $eE_{L}/\text {m}\omega \text {c}$ . In nonlinear case, the variation in pulse skewedness at an optimized laser pulse-length produces different evolution of the wakefield that might affect the electron beam parameters. The present investigation predicts an optimized laser pulse-length (with an optimize ratio of the leading to the trailing pulse edge duration) 35 fs and laser strength parameter $a_{0}=2$ to control the electron bunch charge, emittance, and energy wakefield. Injected bunch charge is enhanced about 20%, and beam emittance is reported to reduce about 40% by employing the skewed Gaussian laser pulse in place of Gaussian pulse for LWFA. Energy-spread of accelerated electron bunch is also reduced from 18% to 6.6% for $s_{\alpha }=0.45$ for 35-fs laser pulse. The electron bunch parameters can also be controlled and optimized using skewed laser pulse and optimized pulse-length.