Including Activation physics?

Hello,

Does using a QGSP_BIC_HP physics list will account for activation also? My current implementation is:

G4VModularPhysicsList* phys = new QGSP_BIC_HP();
runManager->SetUserInitialization(phys);

Do I need to add any other physics list for activation? I just want my energy spectrum to include saturated activities of every isotope I modeled. i.e. something similar to ACT card in MCNP.

Thanks very much in advance!

Regards,
Sanchit Sharma

G4VModularPhysicsList* phys = new QGSP_BIC_HP();
phys ->RegisterPhysics(new G4RadioactiveDecayPhysics);
runManager->SetUserInitialization(phys);
1 Like

Respected Dr. Maire,

Many thanks for your response:
Upon implementing your code in my main.cc I get:

-------- WWWW ------- G4Exception-START -------- WWWW -------
*** G4Exception : Run0111
      issued by : G4PhysicsListHelper::RegisterPorcess
Duplication of processes
*** This is just a warning message. ***
-------- WWWW -------- G4Exception-END --------- WWWW -------

Then I looked into the QGSP_BIC_HP.cc source code. And it already has the G4RadioactiveDecay and G4DecayPhysics, package initalized. Which resolved my query.

I have one more question. Is there a way to check the the cutoff for neutrons, i.e. what is the default cutoff? Can I set a cutoff for neutrons in my code, I would be grateful if I can get an example.

My current attempt to modify cutoff is, I go to the QGSP_BIC_HP.cc in Geant4 source code and do:

  defaultCutValue = 0.00007*CLHEP::mm;  
  SetCutValue(0, "proton");
  SetCutValue(0, "neutron"); 

Let me know your thoughts on this.

Thanks very much!

Sincere regards,
Sanchit Sharma

1- About registered processes, you can see them with /process/list
2- See
http://geant4-userdoc.web.cern.ch/geant4-userdoc/UsersGuides/ForApplicationDeveloper/html/TrackingAndPhysics/thresholdVScut.html

In short : there is no production threshold (aka setCut method) from neutron.
What you want is called Special Tracking Cut.
As said at the end of the above document, see examples/basic/B2

1 Like

Hello,

In this document, it is mentioned in Summary, that–

In summary, we do not have tracking cuts; we only have production thresholds in range. All particles produced and accepted are tracked up to zero range.

  1. Does that mean that neutrons are also tracked till 0 MeV?
  2. Also, what does the production threshold mean. For example if hypothetically, I have a 1 eV production threshold for gamma. does it mean that any neutron interaction will not produce secondary gammas below 1eV energy? I am asking this because if neutrons are tracked till 0 MeV, I see some underestimation in 6.1 MeV and 7.1 MeV gammas from oxygen in water. Also, I am using G4ThermalNeutrons with QGSP_BIC_HP.
    Thanks!

[quote=“sanchitsharma, post:5, topic:593, full:true”]
Hello,

  1. Does that mean that neutrons are also tracked till 0 MeV?

In Hadr04, run 1 event with /tracking/verbose 1

  1. Also, what does the production threshold mean. For example if hypothetically, I have a 1 eV production threshold for gamma. does it mean that any neutron interaction will not produce secondary gammas below 1eV energy?

Production threshold is applied only to e- from ionisation (eg. delta rays) and gamma from bremsstrahlung.
The is no cut for secondaries produced in hadronic processes, nor radioactive decay.

I am asking this because if neutrons are tracked till 0 MeV, I see some underestimation in 6.1 MeV and 7.1 MeV gammas from oxygen in water. Also, I am using G4ThermalNeutrons with QGSP_BIC_HP.

I am not sure to understand what you want to say.

Many thanks for your reply.

I am attaching my comparison plot below. This result is from a neutron interrogation experiment simulation where a NaI detector was simulated along with 14.1 MeV neutron source. QGSP_BIC_HP along with G4ThermalNeutrons is used in simulations. As it can be clearly seen that there is a dip in the simulated spectrum from 0 - 1.6 MeV and after 5 MeV. I believe that the dip from 0-1.6 MeV is due to I-128 beta decay over a period of one-hour irradiation. I do not know what is causing the dip after 5 MeV.

Please let me know your thoughts or possible solutions to this issue.

PS: I did not correct this spectrum for Non linearity of NaI

Thanks very much!