Decoupling acceleration and wiggling in a laser-produced Betatron source

Betatron radiation is produced in laser plasma accelerators when the electrons are accelerated and simultaneously wiggle across the propagation axis Rousse et al., Phys. Rev. Lett. 93, 135005 (2004). The mechanisms of electron acceleration and x-ray radiation production follow different scaling laws Corde et al., Rev. Mod. Phys. 85, 1–48 (2013), and the brightest x-ray radiation is often produced for an electron beam with a lower quality in terms of energy and divergence. Here, we report a laser-driven betatron x-ray source where the plasma density profile is tailored in order to separate the acceleration and wiggler stages, which allows for the independent optimizations of acceleration and x-ray production. We demonstrate this concept experimentally and show that the betatron photon energy can be controlled by adjusting the length of the plasma wiggler. This scheme offers a path to overcome the limitations of conventional betatron sources, enabling the production of bright, stable, energetic, and collimated x-ray beams.