Penelope Models

Physics processes for photons, electrons and positrons have been implemented in Geant4 according to the PENELOPE code (PENetration and Energy LOss of Positrons and Electrons), version 2008. Models for the following processes have been included: Compton scattering, photoelectric effect, Rayleigh scattering, gamma conversion, bremsstrahlung, ionisation and positron annihilation and are described in more detail in Ref.[eal01]. The Penelope models have been specifically developed for Monte Carlo simulation and great care was given to the low energy description (i.e. atomic effects, etc.). Hence, these implementations provide reliable results for energies from 100 eV up to 6 GeV [eal01, SFernandezVAS03], in Geant4 the upper limit 1 GeV is used. These models may be used as an alternative to standard and Livermore models.

Generic Calculation of Total Cross Sections

In Geant4 EM interpolation of physics tables (energy loss, ranges, cross sections) is performed by the G4PhysicsVector class using linear or logarithmic scale with linear or spline iterpolation. For a number of models the energy dependence of the total cross section is not so regular. For example, the Livermore evaluated data libraries with a scale of the concrete data. Thus, for some models the total cross is obtained by interpolation according to the formula [Ste03]:

(3)\[\log(\sigma(E)) = {\log(\sigma_1)\log(E_2/E) + \log(\sigma_2)\log(E/E_1) \over \log(E_2/E_1)}\]

where \(E\) is actual energy, \(E_1\) and \(E_2\) are respectively the closest lower and higher energy points for which data (\(\sigma_1\) and \(\sigma_2\)) are available. For other processes interpolation method is chosen depending on cross section shape.

Bibliography

eal01(1,2)

F. Salvat et al. Penelope - a code system for monte carlo simulation of electron and photon transport. Technical Report, Workshop Proceedings Issy-les-Moulineaux, France; AEN-NEA, 5-7 November 2001.

SFernandezVAS03

J. Sempau, J.M. Fernández-Varea, E. Acosta, and F. Salvat. Experimental benchmarks of the monte carlo code penelope. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 207(2):107–123, jun 2003. URL: https://doi.org/10.1016/s0168-583x(03)00453-1, doi:10.1016/s0168-583x(03)00453-1.

Ste03

Jiri Stepanek. Electron and positron atomic elastic scattering cross sections. Radiation Physics and Chemistry, 66(2):99–116, feb 2003. URL: https://doi.org/10.1016/s0969-806x(02)00386-9, doi:10.1016/s0969-806x(02)00386-9.