[Gate-users] Strange pile up effects with Cylindrical PET system

[K B]

Hello Simon,

   I did check to make sure that the children are totally included in the
mother volume ie. the thickness of the Rsector, module and cylindricalPET
change accordingly to accommodate a 16 or 17 mm crystal. For all the various
crystal thickness, I run a geometry check using
 /geometry/test/recursive_test  and get :

          GeomTest: no daughter volume extending outside mother detected.
          GeomTest: no overlapping daughters detected.

Attached is another plot showing the total number of singles with energy
greater than a certain value. On the yaxis I plot the total number of
singles (normalized individually to 1 in each case) above a certain energy
value (plotted on the y axis). The same plot is here as well :
http://img7.imageshack.us/img7/1014/intgml.png. It is unusual to see that
there are no tails past the 511 peak in the 17 mm case.


KB


>Hi,
>
>I have not really an idea to explain this physically speaking. But maybe
>some suggestions about your simulation design.
>Do your crystals are totally included in their mother volume ? I mean when
>you make them grow to 17 mm, did you anticipate the size of the mother
>volume.
>In case of a child volume bigger than its mother volume, results are not
>predictable at all !
>Same thing when volumes are overlapping.
>So maybe it comes from that.
>
>Cheers,
>Simon
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