Comparison of Serpent and XCom results for photon transport

Separate section for discussion on gamma transport
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Volodymyr Gulik
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Comparison of Serpent and XCom results for photon transport

Post by Volodymyr Gulik » Fri Nov 20, 2020 10:44 am

Good day.

Our Serpent calculations (version 2.1.31) for several types of concrete provide mass attenuation coefficients that are slightly but systematically smaller then that determined from XCOM, within 0,7%. Such deviations were observed for the energies 1.33 МеV, 2.75 МеV and 3.5 МеV; for 0.66 МеV and 1.17 МеV they were much smaller or absent.
1. What can be the reasons of the observed discrepancy?
2. What option can be used to switch off coherent scattering in Serpent?
We modeled the transport of monoenergetic photons through concrete slab at normal incidence (a thin layer of air and then outside were behind the slab). The beam and slab were infinite in the transverse direction. The ds detector at the end face of a slab registered photons exiting the slab in all directions, within the energy bin (E-0.0001, E+0.0001) around the source energy E. The outward current provided by the detector was used to determine mass attenuation coefficient μm which was compared to total attenuation μm without coherent scattering provided by XCOM.
The coefficients μm were determined in Serpent and XCOM for the energies from 0.375 МеV to 3.5 МеV for ordinary, barite, magnetite and serpentine concretes. The greatest deviations were observed for the barite concrete for the energies 2.75 МеV and 3.5 МеV.
The example of data, 20 cm barite slab, E=1,3325 МеV.
Serpent: μm=0.05153; XCOM: μm = 0.05180 (0.05224 with coherent scattering). Relative deviation -0.52%, relative statistical error (Serpent) 0.02%.

Best regards,
Volodymyr Gulik

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