The ESCULAP project aims at studying the capture and acceleration of relativistic electron bunches in a laser plasma wave. A configuration has been proposed where the interaction between the electron bunch and the plasma wave starts few Rayleigh lengths before the laser focal plane. In that configuration, a 100fs 10MeV electron bunch can be compressed up to ~ 4fs during the laser focusing. Then, to accelerate the electrons over large distances, in order to get energies up to several hundreds of MeV, the laser has to be guided over several cm. We have studied guiding by a hollow dielectric capillary. For such guiding, it is well known that the transverse profile of the laser intensity has a strong influence on the fluctuation of the longitudinal and transverse plasma field during the laser propagation. We analyzed in details the effect of these fluctuations on the electron bunch acceleration. Our results show that, even in the best match conditions, the usually used Gaussian transverse profile is not an optimum one, mainly because of the diffraction of the edges of the laser at the entrance of the capillary. We demonstrate that by reducing this diffraction through the use of a flattened Gaussian laser profile, an efficient acceleration of the electron bunch can be obtained over ten centimeters of capillary guiding.
|Working group||Laser-driven electron acceleration|