Radioactive source decay at origin instead of radioactive source

Particles, Track, Event, Run and Biasing
1

Hi, I am new and am trying to learn geant, I am producing a radioactive decay for Bi-207 making a simple geometry and placing a Bismuth source at location [0.0,0.0,0.0] but when I try to decay it unexpectedly decay at origin (0.0,0.0,0.0), I feel like I am missing on something small but crucial but I am not being able to debug the issue.

    G4Tubs* solidTiFoil = new G4Tubs("TiFoil", 0., biRadius+biThickness, 0.5 * biThickness, 0., 360. * deg);
    G4LogicalVolume* logicTiFoil = new G4LogicalVolume(solidTiFoil, matTi, "TiFoil");
    new G4PVPlacement(nullptr, biPosition, logicTiFoil, "TiFoil", logicCathode, false, 0, true);

  
    G4Tubs* solidBi207 = new G4Tubs("Bi207Source", 0., biRadius, 0.5 * biThickness, 0., 360. * deg);
    G4LogicalVolume* logicBi207 = new G4LogicalVolume(solidBi207, matBi207, "Bi207Source");
    new G4PVPlacement(nullptr, biPosition, logicBi207, "Bi207Source", logicTiFoil, false, 0, true);

To debug the issue I try to replace the source position in my PrimaryGenerator.cc but it still did not allow made any difference to where the radioactivity is occurring.

   particleSource->SetParticleDefinition(GetBi207());
   particleSource->SetParticlePosition(G4ThreeVector(0, 0, -3.25*cm));
   particleSource->GeneratePrimaryVertex(anEvent);

While Debugging: Debugging117 Cathode Position: -32.495 Anode Position: 32.5 Bi207 position: (0,0,0)
This position is with respect to mother volume which is at cathode position

_Geant4 Version:11.3.0
_Operating System:MacOS Sequoia 15.3
_Compiler/Version: Apple clang version 16.0.0
_CMake Version:3.29.5

Radioactivity at center of active Volume (1)
Radioactivity at center of active Volume (1)1738×1098 129 KB

Bismuth is clearly visible in different location then where radioactivity is observed
Bismuth is clearly visible in different location then where radioactivity is observed1368×1008 30.4 KB

2

Hello rraut,

I’m not sure I understand your problem.
If you put your primary track at (0,0,0) with 0 kinetic energy it is correct that it decays at the same point. When you change position, the decay should occur at the new position.

I suggest you use the /tracking/verbose command to see what is happening.
If you set the verbosity to 2 or 3 you can get a lot of information about all the tracks in your simulation.

Andrea