Monoenergetic electron beam generation in a laser-drivenplasma acceleration

Abstract

We obtained a 7-MeV monoenergetic electron beam from aplasma with the electron density ne of1.5 × 1020 cm-3 produced by a 2-TW 50-fs laser pulse.In both higher and lower sides of the density region of4 × 1019–4 × 1020 cm-3, energy spectra ofelectrons were bi-Maxwellian distribution function whose maximumelectron energy and effective electron temperature were 30 MeV andapproximately MeV, respectively. Observed first Stokes satellitesin the forward scattering light spectra, and the densitydependences of maximum electron energy and the effectivetemperature suggest that electrons are first accelerated by SMLWFAand are further accelerated by direct laser acceleration (DLA) inthe ne region of more than 2 × 1020 cm-3;a cascade acceleration by SMLWFA and DLA. A Stokes satellite peakobserved with the monoenergetic beam suggests that themonoenergetic beam would be accelerated by SMLWFA.