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APS » Journals » Phys. Rev. Lett. » Volume 103 » Issue 21
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Phys. Rev. Lett. 103, 215006 (2009) [4 pages]

Measurements of the Critical Power for Self-Injection of Electrons in a Laser Wakefield Accelerator

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D. H. Froula1,*, C. E. Clayton2, T. Döppner1, K. A. Marsh2, C. P. J. Barty1, L. Divol1, R. A. Fonseca4, S. H. Glenzer1, C. Joshi2, W. Lu2, S. F. Martins4, P. Michel1, W. B. Mori2, J. P. Palastro1, B. B. Pollock1,3, A. Pak2, J. E. Ralph1,2, J. S. Ross1,3, C. W. Siders1, L. O. Silva4, and T. Wang2
1L-399, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551, USA
2Department of Electrical Engineering, University of California, Los Angeles, California 90095, USA
3Department of Mechanical and Aerospace Engineering, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA
4GoLP/Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Lisbon, Portugal

Received 17 June 2009; published 19 November 2009

A laser wakefield acceleration study has been performed in the matched, self-guided, blowout regime producing 720±50  MeV quasimonoenergetic electrons with a divergence ΔθFWHM of 2.85±0.15  mrad using a 10 J, 60 fs 0.8  μm laser. While maintaining a nearly constant plasma density (3×1018  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 Pcr for relativistic self-focusing and saturates around 100 pC for P/Pcr>5. The results are compared with both analytical scalings and full 3D particle-in-cell simulations.

© 2009 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevLett.103.215006
DOI:
10.1103/PhysRevLett.103.215006
PACS:
52.38.Kd, 41.75.Jv, 52.35.Mw

*froula1@llnl.gov

 
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