Generation and characterization of quasi-monoenergetic electron beams from laser wakefield

Abstract

In the interaction of a 30 fs, 40 TW Ti:sapphire Hercules laser focused to the intensity of 10 19 W/cm 2 onto a supersonic He gas jet, we observed quasi-monoenergetic electron beams with energy up to 300 MeV and an angular divergence of 10 mrad. We found that the initial plasma density significantly affects the resultant electron beam. For plasma densities ranging between 2 x 10 19 to 3.5 x 10 19 cm -3 , quasi-monoenergetic electrons with energies from 80 to 160 MeV and a total charge of about 0.5 nC were produced. Lower plasma densities around 1.5 x 10 19 cm -3 produced quasi-monoenergetic electron beams with higher energy, up to 320 ± 50 MeV, but with a decrease of the total charge to about 5 pC. Characterization of the electron beam in terms of the electron's maximum energy, beam divergence and pointing stability is presented. The performed 2D PIC simulations show the evolution of the laser pulse in the plasma, electron injection, and the specifics of electron acceleration.