Generation of 20 kA electron beam from a laser wakefield accelerator

We present the experimentally generated electron bunch from laser-wakefield acceleration (LWFA) with a charge of 620 pC and a maximum energy up to 0.6 GeV by irradiating 80 TW laser pulses at a 3mm Helium gas jet. The charge of injected electrons is much larger than the normal scaling laws of LWFA in bubble regime. We also got a quasi-monoenergetic electron beam with energy peaked at 249MeV and a charge of 68 pC with the similar laser conditions but lower plasma density. As confirmed by 2D particle-in-cell simulations, the boosted bunch charge is due to the continuous injection caused by the self-steepening and self-compression of a laser pulse. During the nonlinear evolution of the laser pulse, the bubble structure broadens and stretches, leading to a longer dephasing length and larger beam charge. Published by AIP Publishing.