Break geometry, world volume and smaller volume

Geometry, Fields and Transportation
1

Hello, dear all, i have a problem.

I need to build PMTS into a different volume (smaller than the world volume) in my detector, but for some amazing reason, in my loop (10 times) I have 10 times more PMTS if I put the PMTs into the world volume, why is that?

first foto - break geometry

second - normal geometry

Geant4 Version: Geant4-10.7.3
Operating System: mint
Compiler/Version: gcc version 7.5.0
CMake Version: cmake version 3.10.2

Π‘Π½ΠΈΠΌΠΎΠΊ экрана ΠΎΡ‚ 2025-09-18 16-35-47
Π‘Π½ΠΈΠΌΠΎΠΊ экрана ΠΎΡ‚ 2025-09-18 16-35-47976Γ—875 95.1 KB

Π‘Π½ΠΈΠΌΠΎΠΊ экрана ΠΎΡ‚ 2025-09-18 16-34-52
Π‘Π½ΠΈΠΌΠΎΠΊ экрана ΠΎΡ‚ 2025-09-18 16-34-521059Γ—911 66.4 KB

2

Hi,

I am not sure I follow what the different conditions are but in general you ALWAYS have to place any daughter volumes INSIDE the mother volume.

When you change your mother volume you might be placing 10 PMTs for each intended position instead of 1.

When you place a PMT into a logical volume, you can then place this β€œfull” logical volume and it would contain its own β€œalready placed” PMT.

Hope this helps,

/Pico

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