I would like to add TOF into my GEANT4 simulation, but I want to get TOF for each radiation detector.
I know that TOF can be done through GetGlobalTime function, but I do not understand well the physics behind.
I employed GetGlobalTime in the Stepping Action Class, and a counter (k). I understand that Stepping is called several times around a whole event, so to avoid count again the same particle I used counter (k). I saved the TOF and plot it for a run in different ntuples.
I did something like this:
if (volume == fScoringVolume1 && k1==0) {
G4StepPoint *preStepPoint = step->GetPreStepPoint();
G4double tof1 = preStepPoint->GetGlobalTime();
k1+=1;
fEventAction->AddTOF1(tof1); }
I got a TOF of 10 ns for a gamma source at 10 cm from the detector's cover; however, I am not quite sure if my simulation works properly.
Perhaps, someone who can help me with a GEANT4 example which does something similar or a GitHub repository.
GetGlobalTime will provide the amount of time elapsed from the beginning of the simulation. For time of flight, you may need to compute the difference in time between two events. You should thus have at least 2 detectors that are operating in coincidence.
Guillem Pratx I wanted a GEANT4 example which do similar things. For instance, dose deposition is done in example B1, while energy deposition is done in example B3. I have been searching an example which specifies clearly time of fligth measurements, but I couldn't find one. Currently, I am not able to measure TOF experimentally to validate results. I wanted to simulated to in order to determine wheter this variable is representative or not.
What I've been doing is getting the TOF with GetGlobalTime(), but only when particle makes its first step in the sensitive volume with IsFirstStepVolume().
Maybe I misunderstood your question. Unless you know for certain that the gamma photons are all emitted at t = 0, you should compute the TOF by taking the difference between (1) the detection time of the gamma ray and (2) the time at which the gamma ray was emitted. 10 ns for 10 cm is longer than it should. It should be on the order of 0.3 ns.
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