[Gate-users] Interpretation of volumeID variable in root file in optical simulation

[Paweł Kowalski]

Hello,

I have a question about volumeID variable.

In my simulation I have a system of two plastic scintillating strips. At
both ends of each strip, there are photomultipliers.

System looks like that:

PMT1==========PMT2 - strip with two PMTs

                  S           - point source of back-to-back gamma in the
middle of the system

PMT3==========PMT4

In my case, coincidence is a situation when I have optical photons at each
of 4 photomultipliers at both strips.

When I analyze root output, I check if in single event there were hits with
different volumeID[1]. Unfortunately for each event volumeID[1] has the
same value for all hits so it gives me no coincidences.

But when I analyze positions of hits in each event and numbers of photons
at each of four PMTs, I have many coincidences. Results of analysis looks
like that:

Nr of photons at PMT1 || PMT2 || PMT3 || PMT4 || Nr of photons with
volumeID[1]==0 || volumeID[1]==1
...
412 163 63 49 892 0
339 455 475 295 0 2314
184 82 599 696 2305 0
588 423 293 375 2487 0
553 478 51 56 0 1685
212 266 85 151 0 1045
269 345 79 81 1127 0
491 692 32 39 1876 0
387 602 31 8 1476 0
522 625 34 58 0 1825
587 722 46 57 2097 0
485 452 163 277 2060 0
89 144 619 640 2170 0
9 17 59 51 197 0
52 96 376 91 788 0
...

All photons from all photomultipliers has only one value of volumeID[1]
though they are from different volumes.

Is this a problem with my interpretation of volumeID variable or there is
an error in GATE software?
It looks like GATE gives value of volumeID[1] of first hit in event for all
hits in an event.

Thank you in advance for your help.

Best regards,
Paweł Kowalski,
National Centre for Nuclear Research,
Świerk Computing Centre
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