Dear Community,

Beginner with Geant4, we are trying to simulate 4 slabs (infinite planar medium) with infinite gamma source.

Other codes, e.g. in nuclear reactor physics, already have this simple geometry ready. I have to be most compliant with these codes for the purpose of comparison of the implemented physics.

From what I understand, to simulate this kind of geometry in Geant-4, we have to go through G4Box.

**Am I Right ?** To make it really infinite, **can I mention y and z dimensions that are infinite?**

e.g.

new G4Box(â€śSlab1â€ť ,0.5*(x2-x1),1E+28 * cm,1E+28 * cm) ;

new G4Box(â€śSlab2â€ť ,0.5*(x3-x2),1E+28 * cm,1E+28 * cm) ;

new G4Box(â€śSlab3â€ť ,0.5*(x4-x3),1E+28 * cm,1E+28 * cm) ;

new G4Box(â€śSlab4â€ť ,0.5*(x5-x4),1E+28 * cm,1E+28 * cm) ;

new G4Box(â€śWorldâ€ť ,1E+28*cm ,1E+28 * cm,1E+28 * cm) ;

Then, we define our logical volumes, followed by the physical volumes. This â€ś**1E + 28 * cm**â€ť corresponds exactly to what the code in reactor physics recognizes as infinite.

I tried a simulation going with this methodology, but I have overlapping issues between slab 2 and 4 which appear at infinite positionsâ€¦

Checking overlaps for volume Slab1 (G4Box) â€¦ OK!

Checking overlaps for volume Slab2 (G4Box) â€¦ OK!

Checking overlaps for volume Slab3 (G4Box) â€¦ OK!

Checking overlaps for volume Slab4 (G4Box) â€¦

-------- WWWW ------- G4Exception-START -------- WWWW -------

*** G4Exception : GeomVol1002

issued by : G4PVPlacement::CheckOverlaps()

Overlap with volume already placed !

Overlap is detected for volume Slab4:0 (G4Box)

with Slab2:0 (G4Box) volumeâ€™s

local point (0,-2.40287e+28,3.5745e+28), overlapping by at least: 1 cm

NOTE: Reached maximum fixed number -1- of overlaps reports for this volume !

*** This is just a warning message. ***

Unfortunately, at the moment, I donâ€™t have the visualization capabilities to see further. So your response will help a lot.

Any advice is welcome.