[Gate-users] The gateCoincidengces.dat is empty

[cindy Dong]

Hi,
  I'm new to Gate.
I want to simulate a PET system which consists of two detector heads facing
each other ,but the output is that it has gateCoincidences.dat
(/gate/output/ascii/setOutFileCoincidencesFlag 1)but it's empty,while
gateSingles.dat&gateHits.dat are filled.Why?Is it because that
gateCoincidences.dat has rsectorID,moduleID, submoduleID,crystalID while the
flat panel scanner doesn't have such system geometry(I designed the
PETscanner consists of level1,level2)? If that,how should i design the flat
panel to get the coincidences information?
Thanks for your help,
Cindy