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Forum: Event and Track Management
Date: Apr 24, 05:22
From: Jincai <Jincai>

Hi, All!

I have been trying to simulate neutron transportation using Geant4 , but I encountered some difficulties. I appreciate any suggestion and help.

My model consists of several tubes (i.e. cylinder shells), whose centers are located in the same point. My neutron source is one of those tubes(My model is shown in the attachment 1 and 2).

Now I want to have all top and bottom boundaries of the tubes set as reflecting surfaces (i.e., a particle track that hits a reflecting surface is reflected specularly.). Then I added following lines in the SteppingAction.cc:

G4StepPoint* p1 = step->GetPostStepPoint();
G4ThreeVector p1pos= p1->GetPosition();
G4double p1z = p1pos.getZ();                      
if ((p1z >= 500)||(p1z <= -500))                 
    {

  G4double momentumX =  step->GetTrack()->GetMomentumDirection().x();
  G4double momentumY =  step->GetTrack()->GetMomentumDirection().y();
  G4double momentumZ =  step->GetTrack()->GetMomentumDirection().z();
  G4double momentumZ2 = -momentumZ;
          theTrack->SetMomentumDirection(G4ThreeVector(momentumX,momentumY,momentumZ2));

    }

However, I found out that some particles would moving out of these tubes through the top or bottom boundries after they are reflected some times, which can be seen in the attachment 3, 4 and 5.

 I greatly appreciate it if anyone can give me some advice.
Thank you sincerely,
Jincai.

   Attachment:
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2019/04/24/05.20-8239-1.jpg
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2019/04/24/05.20-11716-2.jpg
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2019/04/24/05.20-36653-33.png
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2019/04/24/05.20-12881-44.png
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2019/04/24/05.20-74925-55.png

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1 None: Re: Set   (Makoto Asai - Apr 24, 05:49)
(_ Question: Re: Set   (Jincai - Apr 24, 06:41)
(_ None: Re: Set   (Makoto Asai - Apr 24, 06:48)
1 Question: Re: Set   (Jincai - Apr 24, 08:02)
1 None: Re: Set   (Makoto Asai - Apr 24, 08:38)
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2 Question: Re: Set   (Jincai - Apr 24, 17:23)
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