I have calculated microdosimetric quantity (yF and yD) for 40 keV photon using Geant4-DNA physics (“microyz” input example) in 1 um water sphere and for the same photon with FLUKA code using TEPC filled with TE-propane gas of density required for 1 um. But FLUKA calculated yD values is about 35% higher and yF values is about 40% higher as compared to Geant4-DNA physics based results.
However, for higher energy photon such as 100 keV and above, agreement of yF and yD based on Geant4-DNA and FLUKA is within 2-5 %.
Simulation setup is as below:
- For FLUKA, production and transport cuts are set at 1 keV (which is lowest available) and in Geant4-DNA (option_2) these are 10 eV.
- In FLUKA, parallel photon beam incident on TEPC placed in air whereas in “microyz” input point-isotropic photon source is placed at the centre of water-box.
What may be the probable cause for this large deviation in 40 keV photon or whether I am doing something wrong?