Experimental observation of monoenergetic electron beam generated by laser-driven plasma acceleration

Monoenergetic beams containing more than 106 electrons with an energy of 25 MeV are generated by the interaction of an intense Ti:sapphire laser pulse with high density plasmas. The electron energy and the number of electrons of the monoenergetic beams are increased by using a long focus off-axis parabolic mirror. Single shot measurements of the electron energy spectrum and of the forward scattered light spectrum was performed simultaneously in order to investigate the acceleration mechanisms. Several peaks are observed in the electron energy spectrum, the monoenergetic peaks contain more than 106 electrons. As for the forward scattered light spectrum, the second harmonic laser light and its higher order satellite peaks were observed for laser power higher than 3 TW. The plasma electron density estimated from the Stokes satellite peaks agrees with the results of the gas jet density measurement by interferometry