Simulation Studies of Electron Injection in CO2 Laser-driven Self-modulated and Blowout Regimes *

The process of electron self-injection into CO2 laser driven plasma wakes in the parameter space ranging from the self-modulated to the blowout regimes has been studied using 3D Particle-in-Cell simulations with code SPACE. In SM-LWFA regime, self-injection arises with the wave breaking which occurs at a field strength that is significantly below the 1D wave-breaking threshold. This process intensifies at higher laser power and plasma density and is suppressed at low plasma densities, below 1 ×10¹⁷ cm^-3. In the blowout regime, the self-injection was not observed under simulation conditions. The two-color injection process driven in high-Z material plasmas by a high-intensity Ti-sapphire laser with low normalized vector potential a₀, followed up by a lower-intensity, high-a₀ CO2 laser pulse has also been investigated and compared with the recent experiments at Brookhaven National Laboratory..