Self-injected electron in self-modulated laser wakefield accelerator

SM-LWFA has been widely studied because of its simplicity. In the SM-LWFA, a long (>λ_p) ultrahigh-intensity (>10¹⁸ cm^-2) laser pulse is used to generate a laser wakefield in a homogeneous plasma. When a long laser pulse passes through the plasma, the laser pulse is modulated into many shorter pulses due to the Raman forward scattering instability. In this case, the modulated pulse width is equal to the plasma wavelength scattering instability. In this case, the modulated into many shorter pulses due to the plasma wavelength λ_p. These laser pulse train excites the wakefield resonantly and the amplitude of the wakefield grows up. The shape of the wakefield changes from a sinusoidal wave to a steep one as the wave grows, and eventually transverse and longitudinal wave breakings occur. Due to this effect, some electrons are self-injected into the wakefield and they are accelerated to high energies. Some other effects are also known to be a source of the self-injection in the SM-LWFA. Electron self-injection mechanisms and acceleration of self-injected electrons are investigated with the help of laser wakefield accelerator experiments.