Production of ultra-collimated bunches of multi-MeV electrons by 35-fs laser pulses propagating in exploding-foil plasmas

Very collimated bunches of high energy electrons have been produced by focusing super-intense femtosecond laser pulses in submillimeter under-dense plasmas. The density of the plasma, preformed with the laser exploding-foil technique, was mapped using Nomarski interferometry. The electron beam was fully characterized: up to 10^9 electrons per shot were accelerated, most of which in a beam of aperture below 10^-3 sterad, with energies up to 40 MeV. These measurements, which are well modeled by three-dimensional numerical simulations, validate a reliable method to generate ultrashort and ultracollimated electron bunches.