Influence of target-rear-side short scale length density gradients on laser-driven proton acceleration

A Higginson, R Wilson, J Goodman, M King, R J Dance, N M H Butler, C D Armstrong, M Notley, D C Carroll, Y Fang, X H Yuan, D Neely, R J Gray, P McKenna

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The effects of a short plasma density scale length on laser-driven proton acceleration from foil targets is investigated by heating and driving expansion of a large area of the target rear surface. The maximum proton energy, proton flux and the divergence of the proton beam are all measured to decrease with increasing extent of the plasma expansion. Even for a small plasma scale length of the order of the laser wavelength (~1 µm), a significant effect on the generated proton beam is evident; a substantial decrease in the number of protons over a wide spectral range is measured. A combination of radiation-hydrodynamic and particle-in-cell simulations provide insight into the underlying physics. The results provide new understanding of the importance of even a small plasma density gradient, with implications for applications that require efficient laser energy conversion to ions, such as proton-driven fast-ignition of compressed fusion fuel.

Original languageEnglish
Article number114001
Number of pages10
JournalPlasma Physics and Controlled Fusion
Issue number11
Early online date21 Sept 2021
Publication statusPublished - 30 Nov 2021


  • laser-plasma
  • ion-acceleration
  • target-rear-side
  • short scale length density gradients
  • laser-driven proton acceleration


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