[Gate-users] Strange Axes Offset

[John Apostolakis]

Hi Chris,

I think that what you are seeing is an artifact that originates in the visualisation system.  To be sure that this is the case I suggest two potential ways:
  - Use a different visualisation system that uses ray tracing - which will demonstrate whether there are gaps;
  - Shoot ‘geantino’ test particles (which have no interactions) in a thin ring around the hole where you suspect that there is a problem.  If you encounter the expected surfaces, all is good. I suggest to use a ring that is at least 10^-8 mm larger in the inner radius, and up to 10^-3 mm maybe (or a bit larger).

Best regards,
John Apostolakis
===================================================
John Apostolakis,  EP Department, CERN
SFT (SoFTware for Experiments) Group
Office: Building 32/ room R-003 (ground floor),  Mail: J27210
Email:  john.apostolakis at cern.ch<mailto:john.apostolakis at cern.ch>       Office Tel:  +41-22-767-7239
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On 8 Nov 2019, at 16:06, Christopher Watanabe <chris.r.watanabe at gmail.com<mailto:chris.r.watanabe at gmail.com>> wrote:

Hello all,

I was visualizing a pinhole collimator I'm designing, and I noticed something strange that could effect experiments I run. I've defined my camera system and collimator as being aligned to the y-axis, where the pinhole is centered at (0,0,0). When I visualize though, the axes are off by just the slightest amount, see below.

<axes_offput.JPG>
The ball in the middle is defined with the same radius as the pinhole, and since they are both aligned at (0,0,0), I expect the sphere to sit right inside the pinhole. However, there's a small offset. The strangest part is that every piece of the collimator / camera system has 0 x or z translation (red and blue), which means this shouldn't be the case...

Has anyone else experienced this? And should I be worried?

Thanks!

Chris
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