title: Three electron beams from a laser-plasma wakefield accelerator and the energy apportioning question.
abstract: Laser-wakefield accelerators are compact devices capable of delivering ultra-short electron bunches with pC-level charge and MeV-GeV energy by exploiting the ultra-high electric fields arising from the interaction of intense laser pulses with plasma. We show experimentally and through numerical simulations that a high-energy electron beam is produced simultaneously with two stable lower-energy beams that are ejected in oblique and counter-propagating directions, typically carrying off 5-10% of the initial laser energy. A MeV, 10s nC oblique beam is ejected in a 30°-60° hollow cone, which is filled with more energetic electrons determined by the injection dynamics. A nC-level, 100s keV backward-directed beam is mainly produced at the leading edge of the plasma column. We discuss the apportioning of absorbed laser energy amongst the three beams. Knowledge of the distribution of laser energy and electron beam charge, which determine the overall efficiency, is important for various applications of laser-wakefield accelerators, including the development of staged high-energy accelerators.
authors.affiliation: SUPA, Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK.
authors.forename: X
authors.initials: X
authors.lastname: Yang
authors.affiliation: SUPA, Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK.
authors.forename: E
authors.initials: E
authors.lastname: Brunetti
authors.affiliation: SUPA, Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK.
authors.forename: D Reboredo
authors.initials: DR
authors.lastname: Gil
authors.affiliation: SUPA, Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK.
authors.forename: G H
authors.initials: GH
authors.lastname: Welsh
authors.affiliation: SUPA, Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK.
authors.forename: F Y
authors.initials: FY
authors.lastname: Li
authors.affiliation: SUPA, Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK.
authors.forename: S
authors.initials: S
authors.lastname: Cipiccia
authors.affiliation: SUPA, Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK.
authors.forename: B
authors.initials: B
authors.lastname: Ersfeld
authors.affiliation: SUPA, Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK.
authors.forename: D W
authors.initials: DW
authors.lastname: Grant
authors.affiliation: SUPA, Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK.
authors.forename: P A
authors.initials: PA
authors.lastname: Grant
authors.affiliation: SUPA, Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK.
authors.forename: M R
authors.initials: MR
authors.lastname: Islam
authors.affiliation: SUPA, Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK.
authors.forename: M P
authors.initials: MP
authors.lastname: Tooley
authors.affiliation: SUPA, Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK.|Institute of Physics of the ASCR, ELI-Beamlines, Na Slovance 2, 182 21 Prague, Czech Republic.
authors.forename: G
authors.initials: G
authors.lastname: Vieux
authors.affiliation: SUPA, Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK.
authors.forename: S M
authors.initials: SM
authors.lastname: Wiggins
authors.affiliation: SUPA, Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK.|Laboratory of Laser Plasmas and Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Z M
authors.initials: ZM
authors.lastname: Sheng
authors.affiliation: SUPA, Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK.
authors.forename: D A
authors.initials: DA
authors.lastname: Jaroszynski