Buffered high charge spectrally-peaked proton beams in the relativistic-transparency regime

N P Dover, C A J Palmer, M J V Streeter, H Ahmed, B Albertazzi, M Borghesi, D C Carroll, J Fuchs, R Heathcote, P Hilz, K F Kakolee, S Kar, R. Kodama, A Kon, D A MacLellan, P McKenna, S R Nagel, D Neely, M M Notley, M NakatsutsumiR Prasad, G Scott, M Tampo, M Zepf, J Schreiber, Z Najmudin

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Abstract

Spectrally-peaked proton beams of high charge (Ep » 8 MeV, DE » 4 MeV, N » 50 nC ) have been observed from the interaction of an intense laser (>1019 W cm−2) with ultrathin CH foils, as measured by spectrally-resolved full beam profiles. These beams are reproducibly generated for foil thicknesses 5–100 nm, and exhibit narrowing divergence with decreasing target thickness down to »8 for 5 nm. Simulations demonstrate that the narrow energy spread feature is a result of buffered acceleration of protons. The radiation pressure at the front of the target results in asymmetric sheath fields which permeate throughout the target, causing preferential forward acceleration. Due to their higher charge- to-mass ratio, the protons outrun a carbon plasma driven in the relativistic transparency regime.
Original languageEnglish
Article number013038
Number of pages8
JournalNew Journal of Physics
Volume18
DOIs
Publication statusPublished - 18 Jan 2016

Keywords

  • high intensity lasers
  • proton beams
  • micron thick foils

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