|Message: bug in HP for gammas?||Not Logged In (login)|
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When I was comparing experimental gamma-ray spectra induced by low-energy neutrons (~2 MeV) on different materials (including e.g., copper) taken with a HPGe detector, I have observed that simulations performed with version 9.2 matches quite well with the experiment using QGSP_BIC_HP physics list. However, version 9.4 gave very different result and no match with experimental spectrum. I discussed this problem with experts Vladimir Ivantchenko and Laurent Desorgher and they suggested that the problem might be with HP package.
Therefore, I have performed a simplified simulation. I shoot 1.4 MeV neutrons on a copper cube and detect the gamma-rays with a Ge crystal. I simulated the spectra with version 9.2, 9.4 and 9.5. The results are attached, the x axis is in keV. As is seen, version 9.2 can nicely reproduce the expected gammas and their relative strengths, however version 9.4 and 9.5 give completely wrong gamma-ray energies. Somehow, they are shifted and the relative strengths are also not OK.
Minor problem: using an iron cube, I have also found that the the gamma-ray energy of 1238 keV in 56Fe (from level 2085 keV to level 847 keV) appears at 1233 keV even with version 9.2.
The datafiles, I have used are the following:
version 9.2: PhotonEvaporation2.0 G4EMLOW6.2 G4NDL3.13 RadioactiveDecay3.2 G4ABLA3.0
version 9.4: PhotonEvaporation2.1 G4EMLOW6.19 G4NDL3.14 RadioactiveDecay3.3 G4ABLA3.0 G4NEUTRONXS1.0 G4PII1.2 RealSurface1.0
version 9.5: PhotonEvaporation2.2 G4EMLOW6.23 G4NDL4.0 RadioactiveDecay3.4 G4ABLA3.0 G4NEUTRONXS1.1 G4PII1.3 RealSurface1.0
Attachment: http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2012/06/08/02.33-34613-picture9.2.png http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2012/06/08/02.33-33586-picture9.4.png http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2012/06/08/02.33-84445-picture9.5.png
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