No neutrons due to spontaneous fission

Particles, Track, Event, Run and Biasing
1

_Geant4 Version:_11.1.2
_Operating System:_Ubuntu 22.04.4 LTS
_Compiler/Version:_11.4.0
_CMake Version:_3.22.1

Hello,

I’m trying to score neutrons due to spontaneous fission from uranium fuel. I am able to score alphas successfully but I’m not getting any data for neutrons. I tried running example rdecay02 with macro u238c.mac which should model the decay of stationary u238 nuclei but I’m having the same problem where there are no neutrons scored in the secondary particle output file. In my own model I have implemented the physics list and biasing physics from rdecay02 and also used /process/had/rdm/BRbias true in my macro to switch on branching ratio biasing but no luck so far. Am I missing something?

Best wishes,

Emma

2

I am bumping this topic because I am having the exact same issue with some spontaneous fission sources that I am trying to score.

_Geant4 Version: 11.2.2
_Operating System: Ubuntu 22.04.4 LTS
_CMake: 3.30.3
_GCC: 12.4.0

I recently updated my code from version 10.7.4 where it was working previously. I suspect it might be a physics list issue so I have attached the older version that showed the proper neutron/gamma multiplicity and the newer version (G4_11) wherein I am only able to see properly the gamma ray multiplicity and no neutron emission. I have separately verified that neutrons can be simulated correctly and set:

G4ParticleHPManager::GetInstance()->SetSkipMissingIsotopes( false );
G4HadronicParameters::Instance()->SetTimeThresholdForRadioactiveDecay(1.0e+60 * CLHEP::year);

in the main function. The env directories also appear to be set correctly (I can provide this as well).

physics_G4_10.txt (3.8 KB)
physics_G4_11.txt (3.8 KB)

I have tried to set every single verbose flag that I can, but am looking for further suggestions. It compiles and no flags are raised. Even in UI mode, I can see the tracks of ions, gammas, etc. but no neutrons.
I have a hunch that there is a conflict or flag that must be set that I am skipping over in reading the release notes.
Thanks,
Justin