Proton acceleration by a pair of successive ultraintense femtosecond laser pulses

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We investigate the target normal sheath acceleration of protons in thin aluminum targets irradiated at a relativistic intensity by two time-separated ultrashort (35 fs) laser pulses. When the full-energy laser pulse is temporally split into two identical half-energy pulses, and using target thicknesses of 3 and 6 μm, we observe experimentally that the second half-pulse boosts the maximum energy and charge of the proton beam produced by the first half-pulse for time delays below ∼0.6-1 ps. Using two-dimensional particle-in-cell simulations, we examine the variation of the proton energy spectra with respect to the time-delay between the two pulses. We demonstrate that the expansion of the target front surface caused by the first pulse significantly enhances the hot-electron generation by the second pulse arriving after a few hundreds of fs time delay. This enhancement, however, does not suffice to further accelerate the fastest protons driven by the first pulse once three-dimensional quenching effects have set in. This implies a limit to the maximum time delay that leads to proton energy enhancement, which we theoretically determine.


  • J. Ferri
  • L. Senje
  • M. Dalui
  • K. Svensson
  • B. Aurand
  • M. Hansson
  • A. Persson
  • O. Lundh
  • C. G. Wahlström
  • L. Gremillet
  • E. Siminos
  • T. C. Dubois
  • L. Yi
  • J. L. Martins
  • T. Fülöp
External organisations
  • Chalmers University of Technology
  • CEA Dam Ile-de France (DIF)
  • University of Gothenburg
  • Lund University
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Atom and Molecular Physics and Optics
Original languageEnglish
Article number043115
JournalPhysics of Plasmas
Issue number4
Publication statusPublished - 2018 Apr 1
Publication categoryResearch