Measurements of the critical power for self-injection of electrons in a laser wakefield accelerator.
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.
Froula
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L-399, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551, USA. froula1@llnl.gov
Clayton
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Döppner
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Marsh
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Barty
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Divol
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Fonseca
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Glenzer
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Joshi
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Martins
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Michel
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Mori
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Palastro
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Pollock
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Ralph
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Wang
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