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Question neutron elastic scattering 

Forum: Hadronic Processes
Date: 04 Apr, 2012
From: <Santos>

Dear all,

I am simulating neutron scattering (0.65 MeV energy) into 3 detectors located at polar angles of about 50, 90 and 120 degrees. For this, within a heavy water target I generate neutrons with a cross-section that peaks at about 90 degrees with almost symmetric drop-off to zero at 0 and 180 degrees. I boost the distribution into Lab, but, due to low beam energy, that amounts to a few degree shift.

When I run geantinos, the number of counts in the detectors is what I expect: most in 90-degree one, others somewhat fewer, close to each other.

By the way, I get the same thing with neutrons, BUT, if I substitute D2O with vacuum, OR turn off neutron elastic scattering. If both of these are present, I get most counts in the 50-degree detector, followed by 90- and 120-degree ones.

I do not quite know what to make of it. I find it a bit puzzling.

My hadronic physics list is (heavily borrowed from examples):
****************************
  hadrPhysicsList.push_back( new G4EmExtraPhysics(verboseLevel));

  if(flagHP) {
    hadrPhysicsList.push_back( new G4HadronElasticPhysicsHP(verboseLevel) );
  } else {
    hadrPhysicsList.push_back( new G4HadronElasticPhysics(verboseLevel) );
  }

  //
  hadrPhysicsList.push_back( new G4QStoppingPhysics(verboseLevel));
  hadrPhysicsList.push_back( new G4IonPhysics(verboseLevel));
  hadrPhysicsList.push_back( new G4NeutronTrackingCut(verboseLevel));

  hadrPhysicsList.push_back( new HadronPhysicsQGSP_BIC_HP());

************************************ I get this "puzzle" for both flagHP true and false.

Is this a good choice of hadronic physics for this energy? Any known problems with elastic that I am using?

The HadronPhysicsQGSP_BIC_HP was recommended to me by Vladimir for 10MeV neutrons. Still good here?

I also use LivermorePolarizedPhysics and decay process

By the way, since heavy water is where this occurs, here is my definition:
******************************************
  G4Element* elD = new G4Element("Deuterium", "D", z=1., a= 2.014*g/mole);
  G4Element* elO =  nistman->FindOrBuildElement("O");
  G4Material* D2O = new G4Material(name="HeavyWater",density=1.107*g/cm3,ncomponents=2);
  //  G4cout<<"D2O "<<D2O<<G4endl;
  D2O->AddElement(elD, natoms=2);
  D2O->AddElement(elO, natoms=1);
******************************************

Does this all look correct?

Thank you

ST

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1 Idea: Re: neutron elastic scattering   (Vladimir Ivanchenko - 07 May, 2012)
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