Evolution of the self-injection process in long wavelength infrared laser driven LWFA

Long wavelength infrared laser-driven plasma wakefield accelerators are investigated here in the self-modulated laser wakefield acceleration (SM-LWFA) and blowout regimes using 3D particle-in-cell simulations. The simulation results show that in the SM-LWFA regime, self-injection arises with wave breaking, whereas in the blowout regime, self-injection is not observed under the simulation conditions. The wave breaking process in the SM-LWFA regime 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 (≤ 1 × 10 17 cm-3 here). The produced electrons show spatial modulations with a period matching that of the laser wavelength, which is a clear signature of direct laser acceleration.