Neutron production during low energy deuteron/proton interaction with matter

Physics Lists
1

Dar All,

To interpret the results of an activation experiment we want to simulate the interaction of the 3.46 MeV deuteron beam (or proton beam) with the parts of the experimental setup, which made of Ta, W, Au and Cu. In the simulations I tried to use the all physics lists marked with HP, with the LEND data file installed. ShieldingLEND physics list also was used but in neither case no neutrons are produced! Wtih macro commands, where permitted I activated all the necessary (and perhaps some unnecessary) processes that can lead to the generation of neutrons. I also searched the forum for a clue to the solution, but I couldn’t find it.

My question is primarily whether Geant4 is suitable to study the interacton with matter for such low energy deuterons or protons? If so, what is the magic words for Geant to handle the task correctly.

During the simulations, I noticed that neutrons start to appear above 9MeV beam energy. Would this be the lower limit of manageable energy range? From what source can I get further informations about this subject?

Thank you in advance for your answers and help!
Robi

1 Like
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Dear Robi,
from a “similar” simulation trying to simulate the production of neutrons from a 3H target by protons of 3.8 MeV I can say that using the QGSP_BIC_AllHP and additionally the G4HadronElasticPhysicsHP physics produce neutrons.

Thought they mainly come from 3H, the other materials in the beamline are hit rarely by the beam and because of the cross-section the production is much lower.

3

Hi,

Thanks for your reply!
I tried what you suggested but I still don’t see neutrons. I checked the source code of G4HadronElasticPhysicsHP where the minimum energy is set to 19.5MeV (mainElasticBuilder->GetNeutronModel()->SetMinEnergy(19.5*MeV)). Is this the lower limit of neutrons generation? If yes what is the way to change it, because the mainElasticBuilder is private member of the class and no setter method are provided to this?

Thanks,
Robi

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Dear Robi,
first of all I have to clarify that I have also installed the TENDL and the LEND data sets for cross-sections.
At the moment I am using geant4 version 10.7.p03, but I guess the same holds for 11.0 also.

I have taken the B1 basic example and made some modifications (quick and dirty…).
Bellow I attach the modified files
exampleB1.cc (4.0 KB) (Changed the physics)
B1PrimaryGeneratorAction.cc (4.2 KB) (Changed the defaults)
B1DetectorConstruction.cc (8.0 KB) (changed materials)
B1SteppingAction.cc (3.4 KB) (added output for first step of neutrons)
exampleB1.in.txt (178 Bytes)

At least at my installation when I run the code with the attached macro file I have neutrons produced in both TiT and Cu materials (it is just a print out on the screen), though the ones from Cu are very rare.

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Dear Psaxioti,

Thank you very much for the clue! I will check and report the results soon.

Thanks again!
Robi

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Dear Psaxioti,

Sorry for the late answer!
Thanks for the help, now I see the neutrons too. The G4HadronElasticPhysicsHP physics activation was the solution. Although I was also deceived by the fact that due to the simulation geometry (foils of a few mm or even thinner) the probability of neutron generation is very small. In the case of protons, it is almost zero.

Thanks again!