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Forum: Hadronic Processes
Re: Question The weird recoil energy
Date: Feb 10, 10:05
From: michel maire <michel maire>

On Thu, 31 Jan 2019 01:27:48 GMT, DMHunter wrote:
> Dear Geant4ers,
> We recently met a weird problem with Geant 4.10.3.
> Our simulation is pretty simple: we have 2.45 MeV neutrons emitted
> isotropically from a neutron generator, the neutrons then hit the
> reflector. Some of neutrons will be reflected into the water tank. For
> this thread, we only care about the recoil energy of the neutrons hit on
> the reflector. The attached schematic drawing shows such a setup. The
> material of the reflector is Deuterium only.
> The weird thing we found is: the recoil energy spectrum of the reflector
> has a "cliff", (more accurately, the maximum recoil energy), at ~ 1000
> keV, as another attachment shown. If everything is correct, the expected
> "cliff" would be around 2178 keV, with the calculation of
> 4.0*A/(1+A)/(1+A)*2.45, where A is the atomic number of the material of
> the reflector, 2.45 is energy of incident neutrons, with the unit of
> MeV. We have tested with other elements like Carbon and Hydrogen, the
> "cliff" appeared at the expected energy consistent with the above
> equation.
> Beside, when we set the material of the reflector as composed of Carbon,
> Deuterium and Hydrogen with the mass fraction of 85.8%, 14.15% and
> 0.05%, respectively, this "cliff" also appeared at the same energy
> place, ~ 1000 keV.
> Using the same equation and the maximum recoil of ~ 1000 keV, we figure
> out the appropriate A value would be 8, which is very confusing since we
> have set the reflector to have only one type of element : Deuterium.
> The definition of Deuterium in our script is as following:
>     density = 0.953*g/cm3;
>     G4Isotope* H2 = new G4Isotope("H2",1,2,2.0*g/mole);
>     G4Element* D  = new G4Element("Heavy Water", "D", 1);
>     D->AddIsotope(H2, 100*perCent);
>     G4Material* EJ315 = new G4Material(name="EJ315",density,ncomponents=1);
>     EJ315->AddElement(D, fractionmass=100.0*perCent);
> Can any people please comment it ?

  I ran example Hadr03 with attached macro deuteron.mac.txt
  I also attach output and deuteron plot.


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1 None: Re: The weird recoil energy   (DMHunter - Mar 11, 11:22)
(_ None: Re: The weird recoil energy   (michel maire - Mar 12, 10:55)
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