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Title: Positron generation using laser-wakefield electron sources

Positron generation, using wakefield-accelerated electrons driven into a converter target, was investigated experimentally and through Monte Carlo simulations. Using experimentally measured initial electron distributions from a 60 fs laser system, modeling shows that a collimated wakefield electron beam of moderate energy (50–200 MeV) produces a large number of positrons (∼10{sup 7}), which are emitted from the rear of a mm-scale, high-Z target with divergence angles between 50 and 150 mrad. The large perpendicular momentum of the positrons was found to be dominated by contributions from multiple small angle Coulomb scattering. Positrons were not observed above background noise for a range of targets where simulations indicate a 5–30× increase in the beam charge was necessary to exceed threshold detection. These results provide new understanding to the fundamental limitations of creating narrow-divergence, high-density positron beams from laser-wakefield platforms for use in future laboratory pair plasma experiments.
Authors:
;  [1] ;  [2] ; ; ;  [1]
  1. Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
22493765
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 9; Other Information: (c) 2015 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; BACKGROUND NOISE; COMPUTERIZED SIMULATION; DETECTION; ELECTRON BEAMS; ELECTRON SOURCES; ELECTRON SPECTRA; LASERS; MEV RANGE; MONTE CARLO METHOD; PLASMA; POSITRON BEAMS; POSITRONS