[Gate-users] the consequences of interface in particle tracking

[Chiavassa Sophie]

Hello,

Using GateV6.2 we obtained strange results for geometries with interfaces (like voxelized geometry).
To investigate this point, we performed very simple simulation (main.mac):


-          Mono energetic photon source (80 keV) and a dose actor in a box of water (cuve)

We compare results with the same box adding a second water box (Interface), daughter of the first water box (cuve) (interface water/water).
Theoretically, results should be similar. In fact we obtain a peak in each interface (results.jpg).

Various hypothesis were explored:

-          Same results were obtain for all Electromagnetic processes and models.

-          Global Edep is similar with and without interfaces.

-          Same results were obtain with Geant4 (geant4.zip)

Moreover, when max step size parameter is reduced, we obtain similar peak at each step. It seems that interface create an artificial step in the simulation process.

Could you reproduce this behavior from your side ?
Results obtained with and without interfaces should be similar for homogeneous media.
What do you think about that ?

Best regards


Sophie Chiavassa
Radiophysicienne
Service de physique médicale
Centre de Lutte Contre le Cancer Nantes Atlantiques -
René Gauducheau
Site Hospitalier Nord Bd J. Monod
44805 ST HERBLAIN CEDEX
0240679963
 [cid:193052914 at 09082012-3151]



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