Tomography of the Injection and Acceleration Processes of Monoenergetic Electrons in a Laser Wakefield Accelerator

A tomographic method based on laser machining was used to resolve the electron injection and acceleration processes in a laser wakefield accelerator. It was found that all the electrons in the monoenergetic electron beam are injected at the same location in the plasma column and then accelerated with an acceleration gradient exceeding 2 GeV/cm. In addition, it was observed that there is no significant deceleration of the monoenergetic electron bunch after reaching the maximum energy and the injection position shifts with change of the position of pump-pulse focus. The results are consistent with the model of transverse wave-breaking and beam loading for injection of monoenergetic electrons. With this method the details of the underlying physical processes in a laser wakefield accelerator can be resolved and compared directly to the observations in particle-in-cell simulations