title: Measurements of the critical power for self-injection of electrons in a laser wakefield accelerator.
abstract: A laser wakefield acceleration study has been performed in the matched, self-guided, blowout regime producing 720 +/- 50 MeV quasimonoenergetic electrons with a divergence Deltatheta_{FWHM} of 2.85 +/- 0.15 mrad using a 10 J, 60 fs 0.8 microm laser. While maintaining a nearly constant plasma density (3 x 10{18} cm{-3}), the energy gain increased from 75 to 720 MeV when the plasma length was increased from 3 to 8 mm. Absolute charge measurements indicate that self-injection of electrons occurs when the laser power P exceeds 3 times the critical power P{cr} for relativistic self-focusing and saturates around 100 pC for P/P{cr} > 5. The results are compared with both analytical scalings and full 3D particle-in-cell simulations.
authors.affiliation: L-399, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551, USA. froula1@llnl.gov
authors.forename: D H
authors.initials: DH
authors.lastname: Froula
authors.forename: C E
authors.initials: CE
authors.lastname: Clayton
authors.forename: T
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authors.lastname: Döppner
authors.forename: K A
authors.initials: KA
authors.lastname: Marsh
authors.forename: C P J
authors.initials: CP
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authors.lastname: Divol
authors.forename: R A
authors.initials: RA
authors.lastname: Fonseca
authors.forename: S H
authors.initials: SH
authors.lastname: Glenzer
authors.forename: C
authors.initials: C
authors.lastname: Joshi
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authors.lastname: Lu
authors.forename: S F
authors.initials: SF
authors.lastname: Martins
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authors.lastname: Michel
authors.forename: W B
authors.initials: WB
authors.lastname: Mori
authors.forename: J P
authors.initials: JP
authors.lastname: Palastro
authors.forename: B B
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authors.lastname: Pollock
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authors.lastname: Pak
authors.forename: J E
authors.initials: JE
authors.lastname: Ralph
authors.forename: J S
authors.initials: JS
authors.lastname: Ross
authors.forename: C W
authors.initials: CW
authors.lastname: Siders
authors.forename: L O
authors.initials: LO
authors.lastname: Silva
authors.forename: T
authors.initials: T
authors.lastname: Wang