Photonuclear Interactions

Hello All, let me preface by saying I am new to Geant4.

I am interested in simulating the Photonuclear interactions of Gold (and other metals). I can’t seem to get a few thing right however…

  1. While querying the interaction type - I only ever see “Transportation”. Below is the relevant code from my stepping action:

const G4ParticleDefinition* part = theTrack->GetDefinition();
G4String partType = part->GetParticleName();
G4StepPoint *postPoint = theStep->GetPostStepPoint();
G4String procName = postPoint->GetProcessDefinedStep()->GetProcessName();
if (nanoStart)
{G4cout << "Particle Type: " << partType << “—” << "Process Type: " << procName << G4endl;}

the print statement returns:

Particle Type: neutron—Process Type: Transportation
Particle Type: neutron—Process Type: Transportation

  1. I’ve copied the physics list setup from the Hadr03 example (in /examples/extended). Is there a better physics list OR (even better) is there a useful example out there?


Hi Nick,

I have simulated photoneutron reactions for gamma energies < 20 MeV in gold and other nuclei near the (82,126) doubly closed shell (e.g., Au, Ta, Tl, Pb, Bi) plus many light nuclei. I have used reference physics lists QBBC, QGSP_BIC_HP, Shielding and ShieldingLEND. The first three all give similar results within statistical error, while the fourth gives somewhat different results. My code gives the same results from at least Geant4 10.5.1 to Geant4 10.7.0. I have used my own custom physics lists for photoneutrons and other processes, but the reference lists are easier to use and more portable across Geant4 versions (I have learned the hard way).

Depending on your geometry, it may be that the only process that the neutron is likely to experience on its track after the photoneutron reaction is transportation (i.e., if the target is small and the surrounding media are vacuum or air).

Hi John, thank you for your reply!

So, neutrons are being created - the process that creates them must be Photonuclear interaction - but still, I don’t see a “Photonuclear” process type… by putting the interrogation at the step level, am I potentially missing the event where the particle is created?

Ahh yes, I’ve found it “GetCreatorProcess”

Yes, you beat me to the draw.