Analysis of wakefield electron orbits in plasma wiggler

In relativistic laser plasma interaction, electrons can be simultaneously accelerated and wiggled in an ion cavity created in the wake of an intense short pulse laser propagating in an underdense plasma. As a consequence of their motion, the accelerated electrons emit an intense x-ray beam called laser produced betatron radiation. Being an emission from charged particles, the features of the betatron source are directly linked to the electrons trajectories. In particular, the radiation is emitted in the direction of the electrons velocity. In this article we show how an image of electrons orbits in the wakefield cavity can be deduced from the structure of x-ray spatial profiles.