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Title: Self-modulated laser wakefield accelerators as x-ray sources

The development of a directional, small-divergence, and short-duration picosecond x-ray probe beam with an energy greater than 50 keV is desirable for high energy density science experiments. We therefore explore through particle-in-cell (PIC) computer simulations the possibility of using x-rays radiated by betatron-like motion of electrons from a self-modulated laser wakefield accelerator as a possible candidate to meet this need. Two OSIRIS 2D PIC simulations with mobile ions are presented, one with a normalized vector potential a 0 = 1.5 and the other with an a 0 = 3. We find that in both cases direct laser acceleration (DLA) is an important additional acceleration mechanism in addition to the longitudinal electric field of the plasma wave. Together these mechanisms produce electrons with a continuous energy spectrum with a maximum energy of 300 MeV for a 0 = 3 case and 180 MeV in the a 0 = 1.5 case. Forward-directed x-ray radiation with a photon energy up to 100 keV was calculated for the a 0 = 3 case and up to 12 keV for the a 0 = 1.5 case. The x-ray spectrum can be fitted with a sum of two synchrotron spectra with critical photon energies of 13more » and 45 keV for the a 0 of 3 and critical photon energies of 0.3 and 1.4 keV for a 0 of 1.5 in the plane of polarization of the laser. As a result, the full width at half maximum divergence angle of the x-rays was 62 × 1.9 mrad for a 0 = 3 and 77 × 3.8 mrad for a 0 = 1.5.« less
Authors:
 [1] ;  [2] ;  [1] ;  [1] ;  [1] ;  [3] ;  [3] ;  [1]
  1. Univ. of California, Los Angeles, CA (United States)
  2. Univ. de Lisboa (UT), Lisbon (Portugal)
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
OSTI Identifier:
1332478
Report Number(s):
LLNL-JRNL--697677
Journal ID: ISSN 0741-3335
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Plasma Physics and Controlled Fusion
Additional Journal Information:
Journal Volume: 58; Journal Issue: 3; Journal ID: ISSN 0741-3335
Publisher:
IOP Science
Research Org:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING betatron radiation; laser wakefield acceleration; direct laser acceleration; particle-in-cell codes; laser-plasma interaction; self-modulation instability; Raman forward scattering