|Message: Re: The weird recoil energy||Not Logged In (login)|
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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.
Attachment: http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2019/02/10/10.03-38598-deuteron.mac.txt http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2019/02/10/10.03-5096-deuteron.out.txt http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2019/02/10/10.03-87826-deuteron.gif
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