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Title: Laser-driven ion acceleration via target normal sheath acceleration in the relativistic transparency regime

Here we present an experimental study investigating laser-driven proton acceleration via target normal sheath acceleration (TNSA) over a target thickness range spanning the typical TNSA-dominant regime (~1 μm) down to below the onset of relativistic laser-transparency (<40 nm). This is done with a single target material in the form of freely adjustable films of liquid crystals along with high contrast (via plasma mirror) laser interaction (~2.65 J, 30 fs, I>1 x 10 21 W cm -2). Thickness dependent maximum proton energies scale well with TNSA models down to the thinnest targets, while those under ~40 nm indicate the influence of relativistic transparency on TNSA, observed via differences in light transmission, maximum proton energy, and proton beam spatial profile. Oblique laser incidence (45°) allowed the fielding of numerous diagnostics to determine the interaction quality and details: ion energy and spatial distribution was measured along the laser axis and both front and rear target normal directions; these along with reflected and transmitted light measurements on-shot verify TNSA as dominant during high contrast interaction, even for ultra-thin targets. Additionally, 3D particle-in-cell simulations qualitatively support the experimental observations of target-normal-directed proton acceleration from ultra-thin films.
Authors:
ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [3] ;  [4] ;  [4] ;  [4] ;  [4] ;  [2] ; ORCiD logo [2] ;  [3] ;  [4]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany); Technische Univ. Dresden (Germany)
  3. The Ohio State Univ., Columbus, OH (United States)
  4. Helmholtz-Zentrum Dresden-Rossendorf, Dresden (Germany)
Publication Date:
Report Number(s):
LLNL-JRNL-733302
Journal ID: ISSN 1367-2630
Grant/Contract Number:
AC52-07NA27344; NA0003107; BMBF; 03Z1O511; 654148
Type:
Published Article
Journal Name:
New Journal of Physics
Additional Journal Information:
Journal Volume: 20; Journal Issue: 1; Journal ID: ISSN 1367-2630
Publisher:
IOP Publishing
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA); German Federal Ministry of Education and Research (BMBF)
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; 70 PLASMA PHYSICS AND FUSION
OSTI Identifier:
1437769
Alternate Identifier(s):
OSTI ID: 1430977