[Gate-users] Converging, diverging collimator in 2 directions (Milad Mesri)

Milad Mesri milad.mesri at surgiceye.com
Wed Oct 26 12:05:18 CEST 2016

Dear GATE users,

As part of my bachelor thesis, I'm currently modelling few different collimators to verify the best one for our system. (regarding spatial resolution and geometric efficiency)

I am stuck at the last one, which is the converging (or diverging, depending on the size of the object) in two dimensions, meaning e.g. fan-beam in x-y direction.
I have tried many things without success.
The main problem is the overlap of two daughters and the logic of the spherical repeater which GATE offers.
However when trying this (see textfile in the dropbox) I found out, that using more than 1 repeat in phi direction, the first copy is shifted with certain offset from the y-z plane.

Does anyone had made any experiences with modelling this type of collimator? Is there another option to create a collimator with a spherical centered focalpoint?
Why does the spherical repeater start with a off set (= exactly the angle set) but only in one direction (eg. If phi has an off set, theta won't, see screenshot "PhiAngle 10deg, 1 repeat Phi, ThetaAngle 10 with no offset")?

Please find some screenshots regarding this issue in my dropbox:

Thanks a lot for your help

Best regards

Milad Mesri

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