Dears would give me a clue please how to find G4ThreeVectors()? for the given geometry below? for example for stainless steel capsule?

What do you mean by “how to find G4ThreeVectors()”? You define the geometry with volumes, not vectors. It looks pretty simple. Two cylinders and a half sphere for the source.

Figure out the relative placements from the dimensions shown (you can use a ruler and pen if you don’t like the math). The Ir-192 insert would be placed as a daughter of the capsule cylinder.

If you want to include the cable in the geometry, since it’s made of the same material, just make the capsule as long as you want.

Thank you a lot for your quick response. What is mean is to determining the position of the geometry is it considering the distance from the origin or the distance and thickness of that geometry? for example
// shape 2

G4ThreeVector pos2 = G4ThreeVector(0, 0, -2.344mm); shape2 is lies these coordinates. here the value of z is -2.44mm. Now is this value is the distance from the origin to the geometry?

Each cylinder has its local origin at the center of the cylinder (the length Z runs from -Z/2 to +Z/2 in local coordinates). When you place a daughter volume, what you’re specifying is the position of the center of the daughter with respect to the center of the mother.

I suggest reading the geometry chapter of the Geant4 Developers’ Guide: Geometry — Book For Application Developers 10.7 documentation

Thank you very much!