[Gate-users] generic trapezoid volume (pinhole)

[Débora Salvado]

Thanks for your reply John, but the shape is not the same for all the
pinholes (same volume, different shape), as they need to focus on different
parts of the object.

My main issue is on how to define the theta and phi angles of the generic
trapezoid. Also, is there a way to mirror a volume?

Meanwhile I found this presentation:
http://ipnweb.in2p3.fr/~detect/publications/meeting_step_gdml_geant4_23032010.pdf
which really helped me understand what each parameter of the generic
trapezoid meant, so I'll share it with you GATE users.

Regards,

Débora Salvado


2014-05-27 18:24 GMT+01:00 John Apostolakis <John.Apostolakis at cern.ch>:

>  I am not sure if this will help:
>
>  If all your pinholes are the same shape (or can be created by
> subtracting the same "generic trapezoid" shape from the bigger shape) then
> in Geant4 at least you only need to define one 'solid'.
>
>  Then you subtract it multiple times, with each copy positioned at a
> different location and/or with a different orientation.  ( The orientation
> will be governed by the rotation matrix and the translation that you give
> it.)
>
>  I hope that I understood your issue - or that someone else can add the
> specialised GATE knowledge necessary to give better advice.
>
>  Regards,
>       John
>    ===================================================
>
>  On May 27, 2014, at 5:50 PM, Débora Salvado wrote:
>
>    Dear GATE users,
>
>  I'm trying to use the "generic trapezoid" volume to define a
> multi-pinhole collimator, with each pinhole focusing different parts of the
> FOV.
>  Consider the following set-up:
>
> /gate/world/daughters/name trap1
> /gate/world/daughters/insert  trap
> /gate/trap1/geometry/setDx1   26. mm
> /gate/trap1/geometry/setDx2   26. mm
> /gate/trap1/geometry/setDz    5. mm
> /gate/trap1/geometry/setTheta 0. deg
> /gate/trap1/geometry/setDy1   26. mm
> /gate/trap1/geometry/setDy2   21. mm
> /gate/trap1/geometry/setDx3   21. mm
> /gate/trap1/geometry/setDx4   21. mm
> /gate/trap1/geometry/setPhi   90. deg
> /gate/trap1/geometry/setAlp1  0. deg
> /gate/trap1/geometry/setAlp2  0. deg
> /gate/trap1/setMaterial  Air
> /gate/trap1/placement/setTranslation  0. 0. 0. mm
>
>  When I change the "theta" parameter, the face at +pDz goes up or down in
> the Y direction.
>  How can I make that same face move in the X direction (right or left)?
>  I tried to modify the phi/Alp1/Alp2 parameters, but the visualization
> either stays the same or it gives me an error...
>
>  Thank you in advance,
>
>    Debora Salvado
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>
>
>
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