Hello everyone, I would like to get ~200 MeV quasi-monoenergetic electron beam by doing 2D Particle-In-Cell simulation in bubble regime. The moving window dimension is 50x50 μm for x and y, the simulation mesh size is set 0.04x0.4 μm, each mesh includes 10 particles, laser wavelength is 800 nm, plasma density ~ 8 to 9e18 cm-3, laser pulse duration ~30 fs, normalized vector potential >3.0 and the spot size is around 9-12 μm. I got the e-beam but the energy spread was very large. I hope someone has experiences in this simulation can help me fix some parameters. Thanks a lot!