JAEA Elastic Scattering Model
The \(\gamma\)-ray elastic scattering process in Geant4 is a process that takes into consideration the different mechanisms in which a high-energy photon may be elastically scattered by an atom. These mechanisms include Rayleigh scattering, nuclear Thomson scattering, and Delbrück scattering. A new model developed by JAEA includes all these scattering mechanisms collectively as elastic scattering. A more detailed description can be found in Ref. [OH18].
Total cross section
The total cross section is given by [OH17]
where
Here \(A^R \) is the Rayleigh scattering amplitude, \(A^T \) is the nuclear Thomson scattering amplitude, \(A^D \) is the Delbrück scattering amplitude, and \(A \) is the resultant scattering amplitude. The resultant amplitude is a function of the incident photon energy \(E \), scattering angle \(\theta \), and the atomic number of the scattering atom \(Z \). The total and differential cross sections are pre-calculated and prepared in data files for all elements with \(1\leq Z\leq 100 \) and 10 keV \(\leq E\leq 3 \) MeV over the whole angular range. The structure of the data file is explained in Ref. [OH18].
Sampling of the Final States
Sampling procedure is as the following:
- atom is selected randomly according to the total cross section.
- angular distribution functions are retrieved from data files according to the incident photon energy and atomic number of the scattering atom.
- polar angle is sampled based on the angular distribution function retrieved in 2.
- azimuthal angle is sampled uniformly.
Bibliography
[OH17] | Mohamed Omer and Ryoichi Hajima. Including delbrück scattering in geant4. Nucl. Instrum. Methods Phys. Res., Sect. B, 405:43 – 49, 2017. URL: http://www.sciencedirect.com/science/article/pii/S0168583X17306092, doi:https://doi.org/10.1016/j.nimb.2017.05.028. |
[OH18] | (1, 2) Mohamed Omer and Ryoichi Hajima. Geant4 physics process for elastic scattering of γ-rays. Technical Report 2018-007, Japan Atomic Energy Agency, June 2018. URL: https://jopss.jaea.go.jp/search/servlet/search?5059687, doi:http://dx.doi.org/10.11484/jaea-data-code-2018-007. |