[Gate-users] Sudden drop in recorded coincidences

[Ida Häggström]

Hello!

I'm simulating a static, homogenous cylinder (F-18) for a 0-3600 sec
acquisition time. I've created a bash script that portions the simulation
onto 40 different processors. I've not included physical decay in my
source, so I simply divide the simulation time into 90 sec acquisitions,
i.e. the first processor simulates acquisition between 0-90 sec, the second
90-180 sec and so on up to 3510-3600 sec (yielding 40 root-files). My
problem is that between the acquisition 2250-2340 sec to the one 2340- 2430
sec, there's a sudden drop in recorded coincidences (the later root-files
are less than half in size)! I use the exact same setup for everything
(camera, phantom, suorce etc), the only thing I change is the start and end
time of the dynamic aquisition (as well as the output file names of
course).

I've attached an image of the recorded coincidences vs. time for the entire
0-3600 aquisition where the drop is obvious. I also attached the raw image
text files, and logs for the Gate-run for the two border aquisitions. Any
input is appreciated! Thanks!
Ida

----------- Aliases I send to the macro from my bash-script -------
/control/alias StartTime "2250"
       <----- For the other file, this is "2340"
/control/alias EndTime "2340"
      <----- For the other file, this is "2430"
/control/alias RootOutputName "rootOutput_Prompts_t2250-2340" <----- For
the other file, this is "..._t2340-2430"
/control/alias RawOutputName "rawOutput_t2250-2340"                <-----
For the other file, this is "..._t2340-2430"
/control/alias unstableflag "false"
/control/alias activity "1000000"
/control/alias halfz "125"
/control/alias fullz "250"
/control/alias radius "100"

----------- Part of main macro
-------------------------------------------------
#  S T A R T   A C Q U I S I T I O N
#
/gate/application/setTimeSlice     1.  s
/gate/application/setTimeStart     {StartTime}.  s
/gate/application/setTimeStop      {EndTime}. s
/gate/application/startDAQ

----------- Source macro
--------------------------------------------------------
#     S O U R C E
#
/gate/source/addSource twogamma
/gate/source/twogamma/setActivity {activity} becquerel
/gate/source/twogamma/setType backtoback
/gate/source/twogamma/gps/particle gamma
/gate/source/twogamma/gps/energytype Mono
/gate/source/twogamma/gps/monoenergy 511. keV
/gate/source/twogamma/setForcedUnstableFlag {unstableflag}
/gate/source/twogamma/setForcedHalfLife 6586.2 s #Fluor-18

/gate/source/twogamma/gps/type Volume
/gate/source/twogamma/gps/shape Cylinder
/gate/source/twogamma/gps/radius {radius} mm
/gate/source/twogamma/gps/halfz {halfz} mm
/gate/source/twogamma/gps/centre 0. 0. 0. mm
/gate/source/twogamma/gps/angtype iso
/gate/source/twogamma/gps/mintheta 0. deg
/gate/source/twogamma/gps/maxtheta 180. deg
/gate/source/twogamma/gps/minphi     0. deg
/gate/source/twogamma/gps/maxphi   360. deg
/gate/source/twogamma/gps/confine NULL #phantom_P

#/gate/source/twogamma/visualize 5000 red 2
/gate/source/list
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