Step-like concave retroreflector for single pulse Compton backscattering

We introduce a step-like retroreflector (SR) designed to enhance all-optical inverse Compton scattering (ICS) based on laser wakefield accelerators (LWFAs). Through extensive three-dimensional simulations and theoretical studies, we compare the performance of our SR with traditional reflectors and demonstrate its superior impact on scattering outcomes. Unlike a standard flat retroreflector, our advanced SR design not only refocuses the pulse in the lateral dimension but also significantly expands its longitudinal extent, leading to a marked increase in scattering efficiency and a concurrent improvement in radiation source quality. We provide a theoretical framework outlining the necessary conditions for gas density in the LWFA and the geometry of the SR to ensure matched collision, thus maximizing scattering efficiency. Furthermore, these simulations attest to the stability and robustness of the ICS approach facilitated by the SR, promising a reliable path forward in the development of advanced radiation sources.