3He Neutron Capture

Physics Processes, Models and Cross Sections
1

_Geant4 Version: 4-11.2
_Operating System: Windows 11
_Compiler/Version: Visual Studio 17.9
_CMake Version: 3.29.2

Hello! I am trying to model a 3He neutron detector with a cylindrical moderator. I am using the Shielding_HP physics list and I have defined my polyethylene moderator using the TS_H_of_Polyethylene thermal scattering file. My question is how Geant4 treats to reaction 3He + n → p + 3H. I originally tried looking for nCapture events in my helium-3 volume, but I was not getting any detected. I then just looked for events which had a proton and 2H in the output and these all came from neutronInelastic events. Is this typical for neutron capture reactions at low energies? I am trying to model the detector response, so the number of 3He + n events needs to be accurate.

2

The reaction you wrote doesn’t balance. Maybe 3He + n → 2D, or p + n + D, or 2n + 2p.

3

My mistake, I wrote a 2H instead of a 3H. The products are a proton and triton.

It is 3He + n → p + 3H + 764 keV

4

The nCapture process would be nothing but 3He + n → 4He. You should find the charge exchange process you’re looking for as nInelastic.

You might find example Hadr06 useful, changing the target material from Li7 to He3.

5

@mkelsey, @keblb1dk, I would suggest to start with Hadr03, then Hadr06