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Title: Spot size dependence of laser accelerated protons in thin multi-ion foils

We present a numerical study of the effect of the laser spot size of a circularly polarized laser beam on the energy of quasi-monoenergetic protons in laser proton acceleration using a thin carbon-hydrogen foil. The used proton acceleration scheme is a combination of laser radiation pressure and shielded Coulomb repulsion due to the carbon ions. We observe that the spot size plays a crucial role in determining the net charge of the electron-shielded carbon ion foil and consequently the efficiency of proton acceleration. Using a laser pulse with fixed input energy and pulse length impinging on a carbon-hydrogen foil, a laser beam with smaller spot sizes can generate higher energy but fewer quasi-monoenergetic protons. We studied the scaling of the proton energy with respect to the laser spot size and obtained an optimal spot size for maximum proton energy flux. Using the optimal spot size, we can generate an 80 MeV quasi-monoenergetic proton beam containing more than 10{sup 8} protons using a laser beam with power 250 TW and energy 10 J and a target of thickness 0.15 wavelength and 49 critical density made of 90% carbon and 10% hydrogen.
Authors:
; ;  [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Department of Physics, University of Maryland, College Park, Maryland 20742 (United States)
  2. (United Kingdom)
  3. Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan (China)
  4. (China)
  5. Department of Physics, National Central University, Taoyuan 32001, Taiwan (China)
Publication Date:
OSTI Identifier:
22304196
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 21; Journal Issue: 6; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ACCELERATION; CARBON IONS; LASER RADIATION; LASERS; NUMERICAL ANALYSIS; PROTON BEAMS