Effect of a femtosecond-scale temporal structure of a laser driver on generation of betatron radiation by wakefield accelerated electrons

A brightness of a betatron radiation generated by laser wakefield accelerated electrons can be increased by utilizing the laser driver with shorter duration at the same energy. Such shortening is possible by pulse compression after its nonlinear self-phase modulation in thin plate. However, this method can lead to a rather complex femtosecond-scale time structure of the pulse. In this work, the results of numerical simulations show that the presence of a pedestal or prepulses containing few percents or more of the main pulse energy can inhibit the acceleration process and lead to lower energies of accelerated electrons and generated photons. Simultaneously, the presence of a relatively long and intense postpulse following the main pulse at optimal distance can enhance the oscillations of accelerating electrons and increase the brightness of betatron radiation.