Neutrons from 2H(g,n) at low energies

Physics Processes, Models and Cross Sections
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We have been having some issues producing neutrons from the photodisintegration of naturally occurring deuterons in a hydrocarbon fluid in Geant4 (a small part of a larger simulation).

Using Geant4.11.0.0 I tried a simple test modifying the extended example Hadr03. First 20 MeV gammas fired at a 100m cube of deuterons. Then 4 MeV gammas at the same cube. With the 20 MeV gammas, you get 2H(g,n)p with a Q = -2.2244 MeV. For the run using 4 MeV gammas you only see gamma + H2 → N gamma or e- + deuteron reactions listed. You’re above threshold but you don’t get any neutrons. I didn’t modify anything else in the example files.

Would one have to explicitly include G4EmExtraPhysics in the physics list in addition to what is included in the GammaNuclearPhysics.cc file? Or did I miss something else in setting up the problem?

Cheers,
David

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If you download LEND data set (ftp://gdo-nuclear.ucllnl.org), you can try to use GammaNuclearPhysicsLEND

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Thanks, that worked! I added the LEND data into $G4INSTALL/share/Geant4-11.0.0/data directory and changed to RegisterPhysics( new GammaNuclearPhysicsLEND(“gamma”)); in the physics list of Hadro03. With 4 MeV gammas, one now gets photodisintegrations of the deuterium with the correct Q value.

Cheers,
David

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