[Gate-users] ion source timestamp bug, Gate 7.1

[Gergely Patay]

Dear Gaters,

I installed the latest version of Gate from git. Everything went fine 
(benchmarks etc), until I tried to use the 'generic ion' source for a PET 
simulation.

The timestamps of the hits (and consequently, of the singles and coincidences) 
are weird. They should be distributed uniformly in the [0,1] s interval (as seen 
on the ion_timestamp_gate7.0.png figure), but in 7.1 they are distributed 
exponentially over a much-much larger time interval with an exponent which 
equals to the decay rate of the ion, in this case Na-22.

The macro files were identical, and the corresponding software versions were
- Gate7.0, Geant4.9.6.p03, root5.34.18
- Gate7.1, Geant4.10.01, root5.34.26

This bug is actually the very same to that was reported on March 31, 2011 for 
Gate 6.0.1 
(http://lists.opengatecollaboration.org/mailman/private/gate-users/2011-March/004895.html) 
which somehow disappeared from 7.0 but re-emerged in 7.1.

The bug does not affect the backtoback or e+ sources, and energy spectra are fine.
It might be buried somewhere deep in Geant4.

Do you have any idea what went wrong?

thanks,
  Gergely

--
Gergely Patay
Mediso Ltd.
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