Imaging Electron Trajectories in a Laser-Wakefield Cavity Using Betatron X-Ray Radiation

We demonstrate that betatron x-ray radiation accurately provides direct imaging of electrons trajectories accelerated in laser wakefields. Experimental far field x-ray beam profiles reveal that electrons can follow similar transverse trajectories with typical excursions of 1.5 μm±0.5 μm in the plane of laser polarization and 0.7 μm±0.2 μm in the plane perpendicular