Here we report on optimization of both energy spread and beam divergence in a laser wakefield accelerator (LWFA) operating in the beam loading regime. The self-truncated ionization injection scheme is employed, enabling a precise control over the amount of injected electrons with charges up to 0.5 nC (FWHM) at a quasi-monoenergetic peak.
By employing the optimal beam loading condition, the accelerating gradient is flattened and we eliminate additional energy spread contribution from the acceleration process1,2. This point of minimized finite energy spread is used to limit the betatron oscillations of bunch electrons, leading to a decrease of the normalized beam divergence. Meanwhile, an ultrafast single-shot electron beam diagnostic based on Coherent Transition Radiation reveals ~10 femtosecond bunch lengths yielding peak currents of over 10 kA. Such peak currents are one to two orders of magnitude larger than those found in conventional RF accelerators. Control of the energy spread and beam divergence of LWFA beams with the beam loading condition together with the scaling to high peak currents paves the road for driving secondary superradiant lights sources.
1. J.P. Couperus, et.al., “Demonstration of a beam loaded nanocoulomb-class laser wakefield accelerator”, Nature Communication, 8, 487 (2017)
2. A. Irman et al., “Improved performance of laser wakefield acceleration by tailored self-truncation ionization injection”, Plasma Physics and Controlled Fusion, 60, 044015 (2018)
|Working group||Laser-driven electron acceleration|