title: Effect of laser-focusing conditions on propagation and monoenergetic electron production in laser-wakefield accelerators.
abstract: The effect of laser-focusing conditions on the evolution of relativistic plasma waves in laser-wakefield accelerators is studied both experimentally and with particle-in-cell simulations. For short focal-length (w_{0}<lambda_{p}) interactions, beam breakup prevents stable propagation of the pulse. High field gradients lead to nonlocalized phase injection of electrons, and thus broad energy spread beams. However, for long focal-length geometries (w_{0}>lambda_{p}), a single optical filament can capture the majority of the laser energy and self-guide over distances comparable to the dephasing length, even for these short pulses (ctau approximately lambda_{p}). This allows the wakefield to evolve to the correct shape for the production of the monoenergetic electron bunches, as measured in the experiment.
authors.affiliation: Blackett Laboratory, Imperial College London, SW7 2AZ, United Kingdom.
authors.forename: A G R
authors.initials: AG
authors.lastname: Thomas
authors.forename: Z
authors.initials: Z
authors.lastname: Najmudin
authors.forename: S P D
authors.initials: SP
authors.lastname: Mangles
authors.forename: C D
authors.initials: CD
authors.lastname: Murphy
authors.forename: A E
authors.initials: AE
authors.lastname: Dangor
authors.forename: C
authors.initials: C
authors.lastname: Kamperidis
authors.forename: K L
authors.initials: KL
authors.lastname: Lancaster
authors.forename: W B
authors.initials: WB
authors.lastname: Mori
authors.forename: P A
authors.initials: PA
authors.lastname: Norreys
authors.forename: W
authors.initials: W
authors.lastname: Rozmus
authors.forename: K
authors.initials: K
authors.lastname: Krushelnick