Enhanced relativistic-electron beam collimation using two consecutive laser pulses

The double laser pulse approach to relativistic electron beam(REB) collimationin solid targets has been investigated at the LULI-ELFIE facility. In this scheme two collinear laser pulses are focused onto a solid target with a given intensity ratio and time delay to generate REBs. The magnetic field generated by the first laser-driven REB is used to guide the REB generated by a second delayed laser pulse. We show how electron beam collimationcan be controlled by properly adjusting the ratio of focus size and the delay time between the two pulses. We found that the maximum of electron beam collimationis clearly dependent on the laser focal spot size ratio and related to the magnetic field dynamics. Cu-Kα and CTR imaging diagnostics were implemented to evaluate the collimationeffects on the respectively low energy (≤100 keV) and high energy (≥MeV) components of the REB.