Positron production at extreme light infrastructure – nuclear physics (ELI-NP)

Applied and material physics studies with positron beams of Fermi-surfaces, defects, interfaces etc. offer excellent diagnostics tools. At ELI-NP, an intense beam of about 10(11) photons/s with energies up to 3.5 MeV will be used to generate a positron beam via pair production in a tungsten converter target. To obtain a high intensity beam of moderated positrons the design of the positron source is of high importance. The design of a dedicated positron source at ELI-NP is being investigated based on extensive GEANT4 simulations. The goal of the simulations is to optimize the geometry of the target and the gamma beam collimation. We present here the characteristics of the positron beam obtained for different geometries of the converter target.