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Ultrashort pulse filamentation and monoenergetic electron beam production in LWFAs

Research output: Contribution to Journal/MagazineJournal articlepeer-review

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  • Alexander George Roy Thomas
  • Stuart P. D. Mangles
  • C. D. Murphy
  • Aboobaker E. Dangor
  • P. S. Foster
  • J. G. Gallacher
  • D. A. Jaroszynski
  • Christos Kamperidis
  • Karl Krushelnick
  • K. L. Lancaster
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Article number024010
<mark>Journal publication date</mark>02/2009
<mark>Journal</mark>Plasma Physics and Controlled Fusion
Issue number2
Volume51
Number of pages12
Publication StatusPublished
Early online date7/01/09
<mark>Original language</mark>English

Abstract

In the experiments reported here, the filamentation of ultrashort laser pulses, due to non-optimal choice of focusing geometry and/or electron number density, has a severely deleterious effect on monoenergetic electron beam production in laser wakefield accelerators. Interactions with relatively small focal spots, w0 < λp/2, and with pulse length cτ ≈ λp, incur fragmentation into a large number of low power filaments. These filaments are modulated with a density dependent size of, on average, close to λp. The break-up of the driving pulse results in shorter interaction lengths, compared with larger focal spots, and broad energy-spread electron beams, which are not useful for applications. Filamentation of the pulse occurs because the strongly dynamic focusing (small f-number) of the laser prevents pulse length compression before reaching its minimum spot-size, which results in non-spherical focusing gradients.