Simulating neutron absorption

Physics Processes, Models and Cross Sections
1

Hi all,

I am trying to simulate the energy deposition of the resultants from a neutron capturing onto boron-10, but am wondering if there’s a simpler approach to take. I have a 3D map of where in the material this capture occurs, so all I really need to do is simulate the kinematics of the alpha, lithium, and gamma produced by this. My thought is that rather than randomly generating a momentum for one particle and then generating the other particles’ momenta from conservation laws, this could be done by simple using a neutron capture physics process which produces the output particles with the correct kinematics.

But I was wondering if someone could clarify a few things.

  • In Geant4, when an unstable particle is generated at rest, it immediately decays. If a neutron is placed at rest in an absorbing material, is it similarly immediately absorbed?

  • What physics list is most appropriate for this?

Thank you!

2

No. The hadronic interactions are all discrete (“PostStepDoIt”) processes, not AtRest processes. A neutron at rest will decay, and the time stamp of the daughters will be set by throwing randomly based on the neutron lifetime.

3

you can shoot neutron at meV energies.
Here, a run of example Hadr03, with QGSP_BIC_HP selected (see PhysicsList.cc)

nicconflo.mac.txt (443 Bytes)
nicconflo.out.txt (1.9 KB)

4

This works, but the energies do not seem correct. They seem to vary by a few keV between runs instead of being constant as they should. Why is that?

Edit: the issue may be related to this thread, where the variation came from disagreeing values for mass in different G4 data files.