| Summary: | neutron energy drop to zero resulting in fission even though the fission cross-section was set to zero | ||
|---|---|---|---|
| Product: | Geant4 | Reporter: | Cristian Bungau <cbungau> |
| Component: | processes/hadronic/models/neutron_hp | Assignee: | tkoi |
| Status: | RESOLVED FIXED | ||
| Severity: | major | ||
| Priority: | P5 | ||
| Version: | 9.3 | ||
| Hardware: | All | ||
| OS: | Linux | ||
Hi, The problem was caused by fissions induced by neutrons with energies above 20 MeV, so although the cross-section for HP fission processes was set to zero, by not having/removing the Th232 fission data in G4NDL3.13, the fissions above 20 MeV still take place. I wanted to completely switch off the fissions of Th232, so I can identify the fissions of U233, but this probably cannot be done. Best regards, Cristian |
Hi, I am simulating a Thorium Oxide (ThO2) target, bombarded with 1 GeV protons and the QGSP_BIC_HP physics list. Now, there must be no fission going on, since Thorium does not undergo fission, and there is no fission data in G4NDL3.13. This happens with NO Thorium data in G4NDL AND $G4NEUTRONHP_SKIP_MISSING_ISOTOPES = 1. However in my simulation I get strange results: ********************************************************************************** * G4Track Information: Particle = neutron, Track ID = 3350, Parent ID = 3181 ********************************************************************************** Step# X Y Z KineE dEStep StepLeng TrakLeng Volume Process 0 2.75 mm 2.59 mm 38.8 cm 54.7 MeV 0 eV 0 fm 0 fm target initStep 1 2.83 mm -3.43 mm 38.6 cm 54.7 MeV 6.62 keV 6.29 mm 6.29 mm target hElastic 2 1.15 mm -1.41 cm 38.3 cm 0 eV 0 eV 1.12 cm 1.75 cm target nFission "cout message :Fission takes place at t = 0 s" Please note that the neutron energy dropped to zero despite a dEstep of only 6.62 keV.... Or similar: ******************************************************************************** * G4Track Information: Particle = neutron, Track ID = 5053, Parent ID = 94 ******************************************************************************** Step# X Y Z KineE dEStep StepLeng TrakLeng Volume Process 0 -9.75 mm -1.97 mm 19.6 cm 147 MeV 0 eV 0 fm 0 fm target initStep 1 2.7 cm 7.79 mm 16.4 cm 147 MeV 34.5 keV 4.98 cm 4.98 cm target hElastic 2 9.68 cm 1.96 cm 12.6 cm 0 eV 0 eV 8.03 cm 13 cm target nFission With the same sudden drop to 0 eV, with no dE justifying it, Or, ******************************************************************************** * G4Track Information: Particle = neutron, Track ID = 21183, Parent ID = 21085 ******************************************************************************** Step# X Y Z KineE dEStep StepLeng TrakLeng Volume Process 0 7.63 cm -5.85 mm 15.6 cm 38 MeV 0 eV 0 fm 0 fm target initStep 1 8.7 cm 1.21 mm 14 cm 38 MeV 4.27 keV 2.05 cm 2.05 cm target hElastic 2 11 cm 2.53 cm 10.3 cm 0 eV 0 eV 4.94 cm 7 cm target nFission There is always this sudden drop to 0 eV, followed by fission which should not take place. I believe that because the neutron energy becomes strictly zero, the $G4NEUTRONHP_SKIP_MISSING_ISOTOPES = 1 resulting in: NeutronHP: /Fission file for Z = 90, A = 232 is not found and CrossSection set to 0. has no effect... I attached the large /tracking/verbose 1 output file. Best regards, Cristian