How to improve the accuracy of Geant4 simulation

Physics Processes, Models and Cross Sections
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Geant4 Version: 11.2
Operating System: Window 11
Compiler/Version:
CMake Version:

Hi everyone,
I’m trying to simulate the gamma spectrum from a soil sample (RGU sample) by Geant4.
I have performed that. When I compared the Geant4 result with the experiment, it showed that there was a difference at the lowest part of the spectrum. At energy below 180 keV, the Geant4 result (cyan color) was lower than the experiment (grey color). This happens similarly to mcnp6 (orange color). At the higher energy parts, the simulation results seem to agree quite well.

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image1888×973 109 KB

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image1889×960 81.1 KB

I used the EM3 library and enabled the X-ray fluorescence features. The cut-off values for gamma, e-,
and e+ is 1mm.
PhysicList.cc (6.0 KB)
run.mac.txt (613 Bytes)
How can I enhance the accuracy of the Geant4 simulation result? Thank you in advance.

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My guess is that the experimental data includes the effects of backscatter from the shielding and equipment surrounding the detector and that your simulation does not. Backscatter effects are usually found in the ~200keV region. To improve accuracy, you have to improve how accurately your modelled geometry agrees with the experimental geometry.

1 Like
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Thank you for your comment.
I will try to recheck it.