Персона: Вагнер, Вольфганг Зигфрид
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Simulation of positron spectra of a hybrid positron source
As known, the dipole approximation of channeling radiation (CR) successively overestimates the radiation yield, when the electron-beam energy approaches and exceeds 1 GeV. Consequently, we applied the nondipole approximation to simulate positron production via conversion of CR into e(+)e(-)-pairs in the scheme of a so-called hybrid positron source. GEANT4 simulations of positron spectra obtained from an amorphous tungsten converter at irradiation by <100> axial CR generated in tungsten and diamond single crystals are presented. For comparison, we calculated the CR spectra in dipole and nondipole approximation.
Simulation of channeling radiation and positron production in thick diamond structures and a tungsten single crystal
© 2019 The process of de-channeling for electrons of energy 2 GeV channeled in the (110) plane of silicon and tungsten single crystals has been studied. The dynamics of the particle distribution density has been investigated in dependence on both the energy and scattering distribution of the initial electron beam. The influence of de-channeling on the spectral intensity of channeling radiation has been investigated by solving the Fokker-Planck equation. A non-conventional positron source is described based on the generation of radiation by relativistic electrons channeled along different crystallographic planes or axes of W, Si, Ge and C (diamond) single crystals and the subsequent conversion of the radiation into e+e−-pairs in an amorphous tungsten target. The simulation of channeling radiation and its dependence on the incidence angle into the crystal has been carried out by means of our Mathematica codes. The conversion of the radiation into e+e−-pairs and the energy distribution of positrons have been simulated using the GEANT4 package.
Nondipolarity of axial channeling radiation at GeV beam energies
We consider the nondipolarity of axial channeling radiation generated in a tungsten single crystal at electron-beam energies of several GeV. The calculations are based on the realistic axial continuous potential. It could be shown that, compared to the dipole approximation, the nondipole approximation results in a considerable variation of the channeling radiation spectrum. In a simulation of positron production via conversion of gamma radiation into e(+)e(-) pairs, the observed effect may play an important role.
Geant4 implementation of axial channeling radiation in classical description
New module for channeling radiation simulation in Geant4
© 2021 IOP Publishing Ltd and Sissa MedialabWe present a new C++ module for simulation of channeling radiation to be implemented in Geant4 as a discrete physical process. The module allows simulation of channeling radiation from relativistic electrons and positrons with energies above 100 MeV for various types of single crystals. In this paper, we simulate planar channeling radiation applying the classical approach in the dipole approximation as a first attempt not yet considering other contributory processes. Simulation results are proved to be in a rather good agreement with experimental data.