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None very interacting 1 MeV neutrons 

Keywords: neutrons, too much interaction
Forum: Hadronic Processes
Date: 09 Jun, 2006
From: Dennis Haggerty <Dennis Haggerty>

Iím running 1 MeV neutrons into a scint stack. Iím seeing the 1.45 MeV alphas and both the 0.47 and 2.22 MeV gammas so I think that the physics is working correctly. Iím using the LHEP_PRECO_HP physics list.

The problem is that nearly every single neutron is interacting inside this stack. Itís like the density is 10 times higher, or the stack is 10 times thicker, or Iíve got some strange thing turned on to force each neutron to interact inside the stack.

Below is a few cuts from detectorConstruction

a = 10.0129*g/mole;
 G4Isotope* B10 = new G4Isotope("B10", 5., 10., a);

a = 11.0093*g/mole;
 G4Isotope* B11 = new G4Isotope("B11", 5., 11., a);

 G4Element* Bmod = new G4Element(name="BoronModified", symbol="Bmod", ncomponents=2);
 Bmod->AddIsotope(B10, abundance=19.9*perCent);
 Bmod->AddIsotope(B11, abundance=10.1*perCent);

 density = 1.026*g/cm3;
 G4Material* PVT = new G4Material(name="PVT", density, ncomponents=3);
 PVT->AddElement(C,fractionmass=44.8*perCent);
 PVT->AddElement(H,fractionmass=52.4*perCent);
 PVT->AddElement(Bmod,fractionmass=2.8*perCent);

  D1Material = PVT;

  //                               
  // D1
  // 
  solidD1=0;
  logicD1=0; 
  physiD1=0;  
  G4double phiD1;
  phiD1 = 0.0 * deg;
  G4RotationMatrix rmD1;
  rmD1.rotateY(phiD1);
      solidD1 = new G4Box("D1",1.27/2.0*cm, 5.08/2.0*cm, 5.08/2.0*cm);
      logicD1 = new G4LogicalVolume(solidD1,D1Material,"D1");	                  
      physiD1 = new G4PVPlacement(G4Transform3D(rmD1 , G4ThreeVector(0.0*cm, 0.0*mm, 0.0*mm)),"D1",logicD1,physiLayer,false,0);

Iím working with a 5x5x5 cm stack that has been cut into 4 slabs (So I have a D2, D3, and D4 just as above).

When I check the energy deposited in each of my slabs I get a dump that looks like this:

     D1 (MeV)    D2 (MeV)      D3 (MeV)     D4 (MeV)

    0.482022     2.78924           0           0
  0.00590557    0.994639           0           0
     3.27318 1.91468e-06           0           0
    0.134053    0.866495           0           0
    0.999593     2.75413           0           0
     3.27808           0           0           0
     3.26991           0           0           0
     2.89139    0.584628           0           0
     0.72724    0.273233           0           0
     3.27228    0.210463           0           0
     3.26955           0           0           0
    0.992367           0           0           0
     1.00055      2.2831           0           0
     1.00055           0           0           0
     1.00044           0           0           0
     3.27638           0           0           0
           0     3.27709           0           0
           0     3.27759           0           0

As you can see I dont get much of anything in the last two slabs and almost all of the neutrons are interacting in just the first slab.

My code started a number of years ago as ExN03 and I've modified it from there.

Is there something obvious that would cause this?

Thanks,

Dennis

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1 None: Re: very interacting 1 MeV neutrons   (Dennis H. Wright - 13 Jun, 2006)
(_ None: Re: very interacting 1 MeV neutrons   (Dennis Haggerty - 14 Jun, 2006)
(_ None: Re: very interacting 1 MeV neutrons   (Dennis H. Wright - 14 Jun, 2006)
(_ Ok: Re: very interacting 1 MeV neutrons   (Dennis Haggerty - 14 Jun, 2006)
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