title: Demonstration of a narrow energy spread, ∼0.5  GeV electron beam from a two-stage laser wakefield accelerator.
abstract: Laser wakefield acceleration of electrons holds great promise for producing ultracompact stages of GeV scale, high-quality electron beams for applications such as x-ray free electron lasers and high-energy colliders. Ultrahigh intensity laser pulses can be self-guided by relativistic plasma waves (the wake) over tens of vacuum diffraction lengths, to give >1  GeV energy in centimeter-scale low density plasmas using ionization-induced injection to inject charge into the wake even at low densities. By restricting electron injection to a distinct short region, the injector stage, energetic electron beams (of the order of 100 MeV) with a relatively large energy spread are generated. Some of these electrons are then further accelerated by a second, longer accelerator stage, which increases their energy to ∼0.5  GeV while reducing the relative energy spread to <5% FWHM.
authors.affiliation: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA. pollock6@llnl.gov
authors.forename: B B
authors.initials: BB
authors.lastname: Pollock
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authors.lastname: Ralph
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authors.lastname: Meinecke
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authors.lastname: Froula