Simulation of positron energy distributions from a hybrid positron source based on channeling radiation

Positron energy distributions of a non-conventional positron source which is based on the generation of channeling radiation by relativistic electrons channeled along different crystallographic planes and axes of Si, C, Ge and W single crystals and the subsequent conversion of radiation into e+e−-pairs in an amorphous tungsten target have been simulated. The photon spectra of channeling radiation were calculated using the Doyle-Turner approximation for the continuum potentials of the crystallographic planes and axes considered. The classical equations of motion for channeled electrons have been solved in order to obtain the particle trajectories, velocities and accelerations. Applying classical electrodynamics, spectral-angular distributions of channeling radiation are calculated and their dependence on the incidence angle of the electrons is investigated. The calculation of channeling radiation was carried out using our developed Mathematica codes whereas the conversion of radiation into e+e−-pairs and the energy distributions of the positrons have been simulated by means of the GEANT4 package.