[Gate-users] TOF - Cherenkov Photons coincidences - More primary events vs Gate simulation doesn't end....

[Dania Consuegra]

Dear gate users,

I'm using a PETscanner system in order to study the TOF of the Cherenkov
Photons coincidences.

I get acceptable results for the TOF with 15 000 primary events, different
materials (LSO, LYSO, BGO and PbF2) but now I'm looking for more statistics
in the simulation with the aim of comparing my results with the
experimental ones….

My simulation at some point stops when I use more primary events and I can'
*t* understand why….

As I said in a previous email for different seeds (1, 2 and 3) in my
output.root I get 14 000 Singles and 2 000 Coincidences using PbF2 crystals.
The number of primary events in which the simulation stops is different in
each case….

For this simulations I used:

# a simple back-back annigilation gamma source

/gate/source/addSource PencilBeam

/gate/source/PencilBeam/setType backtoback

/gate/source/PencilBeam/gps/particle gamma

/gate/source/PencilBeam/gps/energytype Mono

/gate/source/PencilBeam/gps/monoenergy 511. keV

# position

/gate/source/PencilBeam/gps/centre 0. 0. 0. cm

# angular distribution approximately! covering entry window in current
geometry!

/gate/source/PencilBeam/gps/angtype iso

/gate/source/PencilBeam/gps/mintheta 65. deg

/gate/source/PencilBeam/gps/maxtheta 115. deg

/gate/source/PencilBeam/gps/minphi -10. deg

/gate/source/PencilBeam/gps/maxphi 10. deg

If I comment the last 4 lines of my source definition turning it into a
source that emits in a backtoback isotropically my simulation stops using
seed 1 in 395 725 (almost 400 000) primary events (1 h) when complete 15
000 Singles (1 000 more than before) and the same 2 000 Coincidences….

If I also comment the coincidences information in the output.root my
simulation stops again using seed 1 in the same amount of primary events
(395 725) when complete again, 15 000 Singles….

So, I do not think that my real problem be in the amount of initial
particles with which I run my simulation. Maybe is more related with the
way in which the Singles are stored in Gate for a PETscanner system in
order to calculate which events are or not in coincidence….

Maybe there is some cut-off somewhere that doesn'*t *allow my simulation to
continue when i*t**'*s initiated with more primary events and many Cherenkov
Photons are produced. I'm also using the RoughTeflon_LUT surface for the
crystals....

I would like to point out that as I'm working with Cherenkov Photons I'm using
the opticaladder:

/gate/digitizer/Singles/insert opticaladder

/gate/digitizer/Singles/insert readout

/gate/digitizer/Singles/readout/setDepth 3


Any help I would really appreciate it….

Best regards,

Dania Consuegra Rodríguez

Phd student *Jožef Stefan Institute*

PD> With my analysis of the root output information I can get the TOF or
from the information of the Singles tree or from the information of the
Coincidences tree with differences of less than 1 ps between both methods.
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