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Forum: Geometry
Re: Question Tracking problem with concentric tori (Emanuele Leonardi)
Date: 08 Nov, 2005
From: Emanuele Leonardi <Emanuele Leonardi>

I did not get any reaction to my message from october 26th, so I am
posting a new request for help. If some expert wants to test the effect
described in my previous message, here is some simple code to use
for DetectorConstruction:

@--------------------------------------------------------@
  //--------- Sizes of the principal geometrical components (solids)  ---------
  
  G4double fWorldLength= 100.*m;
      
  //--------- Definitions of Solids, Logical Volumes, Physical Volumes --------
  
  //------------------------------ 
  // World
  //------------------------------ 

  G4double HalfWorldLength = 0.5*fWorldLength;
  G4Box* solidWorld =
    new G4Box("world",HalfWorldLength,HalfWorldLength,HalfWorldLength);
  G4LogicalVolume* logicWorld =
    new G4LogicalVolume(solidWorld,Vacuum,"World",0,0,0);
  logicWorld->SetVisAttributes(G4VisAttributes::Invisible);  
  physiWorld = new G4PVPlacement(0,0,logicWorld,"World",0,false,0);

  //-------------------------
  // Toroidal fiber
  //-------------------------

  G4Torus* solidFiber =
    new G4Torus("clad",0.,1.*cm,10.*cm,0.*deg,180.*deg);
  G4LogicalVolume* logicFiber =
    new G4LogicalVolume(solidFiber,Glue,"FiberClad",0,0,0);
  new G4PVPlacement(0,0,logicFiber,"FiberClad",logicWorld,false,0);

  //-------------------------
  // Toroidal fiber core
  //-------------------------

  G4Torus* solidCore =
    new G4Torus("core",0.,0.5*cm,10.*cm,0.*deg,180.*deg);
  G4LogicalVolume* logicCore =
    new G4LogicalVolume(solidCore,Scintillator,"FiberCore",0,0,0);
  new G4PVPlacement(0,0,logicCore,"FiberCore",logicFiber,false,0);
@-------------------------------------------------------------@

I then shoot an up-going geantino from 0,0,0 with

@-------------------------------------------------------------@
  G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
  G4ParticleDefinition* particle = particleTable->FindParticle("geantino");
  particleGun->SetParticleDefinition(particle);
  particleGun->SetParticlePosition(G4ThreeVector(0.*cm,0.*cm,0.*cm));
  particleGun->SetParticleMomentumDirection(G4ThreeVector(0.,1.,0.));
  particleGun->SetParticleEnergy(100.*MeV);
@-------------------------------------------------------------@

The tracking output gives:

@-------------------------------------------------------------@
#Step# 0
--- Pre-Step status
          World     0 fm       0 fm       0 fm 
--- Post-Step status
          World     0 fm       0 fm       0 fm 
--- Step quantities
Step Length  0 fm 
Track Length 0 fm 
Process      initStep

#Step# 1
--- Pre-Step status
          World     0 fm       0 fm       0 fm 
--- Post-Step status
      FiberClad     0 fm       9 cm       0 fm 
--- Step quantities
Step Length  9 cm 
Track Length 9 cm 
Process Transportation

#Step# 2
--- Pre-Step status
      FiberClad     0 fm       9 cm       0 fm 
--- Post-Step status
      FiberCore     0 fm     9.5 cm       0 fm 
--- Step quantities
Step Length  5 mm 
Track Length 9.5 cm 
Process Transportation

#Step# 3
--- Pre-Step status
      FiberCore     0 fm     9.5 cm       0 fm 
--- Post-Step status
          World     0 fm    10.5 cm       0 fm 
--- Step quantities
Step Length  1 cm 
Track Length 10.5 cm 
Process Transportation

#Step# 4
--- Pre-Step status
          World     0 fm    10.5 cm       0 fm 
--- Post-Step status
      FiberClad     0 fm      11 cm       0 fm 
--- Step quantities
Step Length  5 mm 
Track Length 11 cm 
Process Transportation

#Step# 5
--- Pre-Step status
      FiberClad     0 fm      11 cm       0 fm 
--- Post-Step status
          World     0 fm      11 cm       0 fm 
--- Step quantities
Step Length  0 fm 
Track Length 11 cm 
Process Transportation

#Step# 6
--- Pre-Step status
          World     0 fm      11 cm       0 fm 
--- Post-Step status
     OutOfWorld     0 fm      50 m        0 fm 
--- Step quantities
Step Length  49.9 m  
Track Length 50 m  
Process Transportation
@-------------------------------------------------------------@

I am worried about the 0-length step number 5 and about the fact that
step number 3 ends in the "World" volume rather than the expected
"FiberClad" (or "FiberCore"?).

Could someone please clarify if what I see is correct and why?

Thank you

               Emanuele Leonardi

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1 More: Re: Tracking problem with concentric tori   (Gabriele Cosmo - 08 Nov, 2005)
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