Geometry and radiation source

Geometry, Fields and Transportation
1

Dear all

I am modeling 3 spheres inside a cuboidal world volume.
Geometry is as follows:

  1. Cuboidal world volume with sides 4 cm x 4 cm x 8 cm.

  2. Sphere with radius 4 cm positioned at (0, 0, 4. cm).

  3. Two concentric spheres named as Source (radius = 4. mm) and Target (radius 2. cm). The center of source is dislocated by 4. mm from the center of Target volume The code for this part is a below
    // Spherical shell for Target
    //
    G4Sphere*
    sTarget = new G4Sphere(“sTarget”,
    0.,
    fProstateRadius,
    0.,
    360.*deg,
    0.,
    180.*deg);

    fLogicalTarget = new G4LogicalVolume(sTarget,
    TISSUE,
    “Target”);

    fTarget = new G4PVPlacement(nullptr,
    G4ThreeVector(0., 0., -2.0*cm),
    “Target”,
    fLogicalTarget,
    fWorld,
    false,
    0);

    // Spherical shell for Source
    //
    G4Sphere*
    sSource = new G4Sphere(“sSource”,
    0.*micrometer,
    fTumorRadius,
    0.,
    360.*deg,
    0.,
    180.*deg);

    fLogicalSource = new G4LogicalVolume(sTumor,
    TISSUE,
    “Tumor”);

    fSource = new G4PVPlacement(nullptr,
    G4ThreeVector(0., 0.4*cm, 0.),
    “Source”,
    fLogicalSource,
    fTarget,
    false,
    0);

I am also attaching the image from the viewer. Please find the attachment. Blue is the largest sphere. Green is the Target volume and red is the Source volume.
Now, my question is:

  1. Is this geometry fine if I want to calculate the dose deposited inside the Source and Target region separately?
  2. Since Source volume is not positioned at (0,0,0) and I am interested to uniformly sample the 1 MeV electron sources inside the source volume. How can I get it done with GeneralParticleGun? Currently I am using GPS to get this distribution. But I am interested to use GeneralParticleGun.

Geometry
Geometry.png1068×615 24.7 KB

2

Few remarks on the geometry setup:

  • The world volume should include everything with some margin, i.e. no coincident surfaces;
  • Possibly avoid coincident surfaces between the spheres;
  • You may want to use G4Orb instead of G4Sphere in this case.

For anything related to the particle-gun, please post in the proper Forum “Particle, Track, Event, Run…”

3

Thank-you very much for your response. Do you have any comment about the geometry of red and green sphere? I am interested to compute dose deposition in the green and red sphere separately. The results I am getting shows that energy deposited in green sphere is more then the red sphere. But actually according to my intuition it should be other way around since I am using low energy electrons as source here.

4

There’s not much to comment on such simple geometry. You may want to discuss the results you get for energy deposition on the proper Forum, as it may well depend on the sampling and particle-gun you use…