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Question Peaks in PhotoPeak Efficiency 

Forum: Biasing and Scoring
Date: 26 Oct, 2009
From: KUKI <KUKI>

I have recently started work in geant4. I am trying to calculate the efficiency of the NaI detector and HPGe detector.

I have defined the detector geometry, a simple cylinder. The total Efficiency has a normal decreasing trend with increasing gamma energy. However,Photo peak efficiency with gamma ray energy has certain peaks at about 1 MeV, 2 MeV, 4 Mev and 8 MeV from 0.5 to 10 MeV gamma energy range. This behavior is independent of detector's material. I am unable to sort the problem out. I would be grateful if you could help me in this regard. Following are the relevant portions of the code.

void SteppingAction::UserSteppingAction(const G4Step* aStep)
{
        G4StepPoint* prePoint = aStep->GetPreStepPoint();
 
 {
 const G4VPhysicalVolume* logvol = aStep->GetPreStepPoint()->GetTouchableHandle()->GetVolume();
 if (logvol==detector->GetphysiAbsorber())
  {
  G4double EdepStep = aStep->GetTotalEnergyDeposit();
 
  if (EdepStep > 0.)
 
  evtAct -> AddEdeposit(EdepStep);
  }
 }
 
}

void EventAction::EndOfEventAction(const G4Event* evt)
{
 
        if (Edeposit > 0.)
 {
 myRunAction -> TotalCounts(Edeposit);
 }
 ......
 ......
}

void RunAction::TotalCounts(G4double Ed)
{
 G4ParticleDefinition* particle =
                            primary->GetParticleGun()->GetParticleDefinition();
 Particle = particle->GetParticleName();   
 energy = primary->GetParticleGun()->GetParticleEnergy();
 Total ++;
 if (Ed==energy){
 pphoton++;
 }
}

void RunAction::EndOfRunAction(const G4Run* aRun)
{
        G4double PhotonEffic = pphoton/NbOfEvents;

 G4double TotalEffic = Total/NbOfEvents;
}


looking forward
best regards
 
Kuki

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