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Radio-isotope production using laser Wakefield accelerators

  • Author(s): Leemans, W.P.
  • Rodgers, D.
  • Catravas, P.E.
  • Geddes, C.G.R.
  • Fubiani, G.
  • Toth, C.
  • Esarey, E.
  • Shadwick, B.A.
  • Donahue, R.
  • Smith, A.
  • Reitsma, A.
  • et al.
Abstract

A 10 Hz, 10 TW solid state laser system has been used to produce electron beams suitable for radio-isotope production. The laser beam was focused using a 30 cm focal length f/6 off-axis parabola on a gas plume produced by a high pressure pulsed gas jet. Electrons were trapped and accelerated by high gradient wakefields excited in the ionized gas through the self-modulated laser wakefield instability. The electron beam was measured to contain excesses of 5 nC/bunch. A composite Pb/Cu target was used to convert the electron beam into gamma rays which subsequently produced radio-isotopes through (gamma, n) reactions. Isotope identification through gamma-ray spectroscopy and half-life time measurements demonstrated that Cu^61 was produced which indicates that 20-25 MeV gamma rays were produced, and hence electrons with energies greater than 25-30 MeV. The production of high energy electrons was independently confirmed using a bending magnet spectrometer. The measured spectra had an exponential distribution with a 3 MeV width. The amount of activation was on the order of 2.5 uCi after 3 hours of operation at 1 Hz. Future experiments will aim at increasing this yield by post-accelerating the electron beam using a channel guided laser wakefield accelerator.

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