[Gate-users] half size or full size for trpd ?

[Didier Benoit]

Hi Anne,

On May 14, 2010, at 12:39 AM, Anne Sauve wrote:

> Hello the collaboration,
> 
> I am designing a pinhole SPECT camera and to model the pinhole collimator I am using
> a trpd.
> You specify in the user manual that I should define for this trpd the half length along X ,Y and Z.
> I also define a box that just fits this trpd and since you specify in the user manual to define for a box
> the full length along X,Y and Z that's what I did.
> I find that the box is twice as big as the trpd. 
> What should I believe are the right dimensions ? the ones for the trpd or for the box ?

For the box you give the full length not the half-length, for the trpd is the same thing. For historical reasons, you had to give the half-length for the volumes in Geant4. It's the same thing if you want to give a dimension for your source.

> I want to believe that the box's dimensions are right  but could you confirm that for me.
> 
> Also when you do a translation of a box it is done from the center of the box right ?
> 

Yes, the translation is done from the center of the box, not from a surface (for instance).

> below is my code.
> 
> Thanks
> 
> Anne.
> 
> 
> /gate/world/daughters/name Boxhead
> /gate/world/daughters/insert box
> /gate/Boxhead/geometry/setXLength  10.0 cm
> /gate/Boxhead/geometry/setYLength 16.25 cm
> /gate/Boxhead/geometry/setZLength 22.75 cm
> /gate/Boxhead/placement/setTranslation  8. 0. 0. cm
> /gate/Boxhead/setMaterial Air
> /gate/Boxhead/vis/setColor black
> #/gate/Boxhead/vis/setDaughtersInvisible
> /gate/Boxhead/vis/forceWireframe
> 
> /gate/Boxhead/daughters/name SPECThead
> /gate/Boxhead/daughters/insert trpd
> /gate/SPECThead/geometry/setX1Length  22.75 cm
> /gate/SPECThead/geometry/setY1Length  16.25 cm
> /gate/SPECThead/geometry/setX2Length 0.8 cm
> /gate/SPECThead/geometry/setY2Length 0.8 cm
> /gate/SPECThead/geometry/setZLength 10. cm
> /gate/SPECThead/setMaterial Lead
> /gate/SPECThead/placement/setRotationAxis 0 1 0
> /gate/SPECThead/placement/setRotationAngle -90 deg
> /gate/SPECThead/placement/setTranslation  0.0 0. 0. cm
> /gate/SPECThead/vis/setColor red
> 
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Kind Regards,
Didier

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Didier BENOIT, Ingénieur GATE
Imagerie et Modélisation en Neurobiologie et Cancérologie (IMNC)
IMNC – UMR 8165 CNRS – Université Paris 7 – Université Paris 11
Campus d’Orsay
Bâtiment 440
91406 ORSAY Cedex
 
Tél : (33) 1 69 15 68 76
E-mail : benoit at imnc.in2p3.fr
http://www.imnc.in2p3.fr
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