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None GDML and Optical Photons 

Forum: Processes Involving Optical Photons
Date: 09 Oct, 2009
From: Edward Alvarado <Edward Alvarado>

Hi,

 I have successfully imported, from a 3D modeling CAD, a complex geometry description and added optical properties to it within Geant4.

 I am currently having problems during optical simulations, when the volume in use is imported and described as a tessellated volume in a GDML file there are incorrect reflections at boundaries. What happens is that Optical Photons only bounce once correctly on the inner surface of a closed tube, on the second interaction with the border the photon always escape.

 To test problem I have made a simple test: I made the same geometry description in geant4 with G4Tube and with the CAD (and then imported into geant4). I get the expected results with only the G4Tube, the imported volume always has optical boundaries problem. To make the test simpler I am currently only using the optical boundary process, and defining refractive indexes into the material description.

I add an a image of typical optical event. Due the refractive indexes the ray should not escape in neither case. The first image is from the tessellated solid, and the second one is a G4Tube.

http://img53.imageshack.us/img53/8935/volumeimported.jpg
http://img183.imageshack.us/img183/8238/volumeg4tube.jpg

Just ask if more information is needed.
Thanks in advance for any help or advice.

Cheers,

Edward Alvarado,
SiLab UTFSM, Chile.
 

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