Message: Energy deposited is larger than the energy of the primary gamma beam Not Logged In (login)
 Next-in-Thread Next-in-Thread
 Next-in-Forum Next-in-Forum

Question Energy deposited is larger than the energy of the primary gamma beam 

Forum: Processes Involving Optical Photons
Date: 27 Jan, 2014
From: Martin Kocan <Martin Kocan>

Dear Geant experts,

(i) The energy deposited in a NaI scintillator is larger than the energy of the primary gamma beam. As an example the energy of the gamma beam was set to 1MeV shooting straight into the NaI scintillator (defined in PrimaryGenerationAction.cc) however the energy deposited occured most often at about 1.01965MeV. I would expect the maximum energy deposited at 1MeV. Not sure where the stray energy comes from...

(ii) The number of optical photons detected at the photon detector was ~6800 which is less than expected ~8000. The scintillation yield was set to 40000 photons per 1MeV. The efficiency of the PMT was 20% so the expected photon hits should be around 8000 per 1MeV.

Could you please point me to any error in the code? I am struggling.

The geometry is as follows:

-NaI cylinder (simulating scintillator) and a thin metallic disc (simulating photon detector) are both housed within a mother volume Al cylinder ("AlHousing").

-The metallic disc (photon detector made of Ag) is positioned at the back of the NaI cylinder against NaI's rear surface.

-Al cylinder ("AlHousing") is within a mother volume "DetectorBox" (box made of air).

-"DetectorBox" is within a mother volume "CalibZone" (sphere made of air).

-"CalibZone" is a sphere within a mother volume "SubWorld" (box) which is within a mother "World" (box) (all filled with air).

-NaI cylinder and Ag disc (photon detector) are both sensitive volumes created by following the LXe and WLS examples.

Other notes:

-I am using unix version of geant4.9.6.

-I checked all the volumes and there are no overlapping volumes as well as all daughter volumes are within its mother volumes.

-The surfaces of NaI cylinder and photon detector (metallic disc) are defined via G4LogicalBorderSurface. Refractive index is defined for AlHousing, NaI scintillator and photon detector. Reflectivity of the NaI surface is set to 94%. The only non-zero efficiency is set to photon detector (thin metallic disc) and averages to 20% across 350-525nm. G4OpticalSurface for NaI and photon detector is defined as glisur (model), polished (finish), dielectric_metal (type) and 1.0 (sigma alpha).

-Energy deposition (GetTotalEnergyDeposit) is called in SensitiveDetector.cc and written out into an output file in RunAction.cc

-Photon hits are counted whenever an optical photon hits the Ag disc (photon detector) and G4OpBoundaryProcessStatus is equal to 'Detection' as written in SteppingAction.cc. 'ProcessHits_constStep' in PhotonDet.cc is called that counts the hits and writes it to an output file when an event is complete.

-Selection of relevant cc files and ScreenOutput.txt are attached.

Thank you very much for your help in advance.

Best regards,

Martin.

   Attachment:
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2014/01/27/19.07-60224-DetectorConstruction.cc
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2014/01/27/19.07-56627-SensitiveDetector.cc
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2014/01/27/19.07-89009-PhotonDet.cc
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2014/01/27/19.07-79638-SteppingAction.cc
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2014/01/27/19.07-35462-RunAction.cc
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2014/01/27/19.07-20345-PhysicsList.cc
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2014/01/27/19.07-63504-PrimaryGeneratorAction.cc
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2014/01/27/19.07-91144-ScreenOutput.txt

Inline Depth:
 1 1
 All All
Outline Depth:
 1 1
 2 2
 All All
Add message: (add)

1 Feedback: Re: Energy deposited is larger than the energy of the primary gamma beam   (Gumplinger Peter - 28 Jan, 2014)
(_ None: Re: Energy deposited is larger than the energy of the primary gamma beam   (Martin Kocan - 30 Jan, 2014)
(_ Agree: Re: Energy deposited is larger than the energy of the primary gamma beam   (Gumplinger Peter - 31 Jan, 2014)
 Add Message Add Message
to: "Energy deposited is larger than the energy of the primary gamma beam"

 Subscribe Subscribe

This site runs SLAC HyperNews version 1.11-slac-98, derived from the original HyperNews