Dual-color γ-rays via all-optical Compton scattering from a cascaded laser-driven wakefield accelerator

We have experimentally produced two-color electron beams with peak energies at ∼300 and ∼210 MeV based on the combination of self-injection with density-gradient injection in a cascaded laser-driven wakefield accelerator. Performing all-optical Compton scattering, the driving laser pulse, which was reflected by a plasma mirror, can be directed to collide with the generated electron beams to produce dual-color $\gamma$-rays peaking at 1.07 and 0.59 MeV. In order to get insights into the experimental results, particle-in-cell simulations have been performed to demonstrate the process of the two-color electron beams' injection and acceleration. The simulated spectrum of $\gamma$-ray radiation closely matches the experimental spectrum. These dual-color $\gamma$-rays can be used for ultrafast pump-probe experiments and high energy x-ray radiology. (paper)