GlobalTime Tracking Challenges for Short Reactions of Secondary Particles from Long Half-Life Decay Isotopes

[Seungwoo_Son]

I am currently conducting simulations to track the time stamps of each step for secondary particles generated from the decay of Cf-252 (e.g., alpha, e-, etc.).
According to various explanations in forums, I found that the pre and post global times are automatically derived from the decay global time of Cf-252, which is near its half-life (2.645 years). As a result, the global time values in Geant4 are not effective for tracking the timing of each step, because the local times of secondary particles (ranging from 1e-3 to 1e3 ns) are significantly shorter than the decay time of Cf-252 (on the order of 1e14 to 1e15 ns).

So, I attempted to correlate and inherit the post-local time of the primary particle (Cf-252) to the pre-local time of secondary particles for each step where the primary particle generates a secondary particle. However, I was unable to effectively inherit the post-local time of the primary particle to the secondary particles.

To resolve this issue, is there an effective way to remove or bypass the decay time of Cf-252? Alternatively, is there a way to correctly inherit the primary particle’s post-local time to the pre-local time of the secondary particles on a step-by-step basis?

I always appreciate to the devotion of Geant4 forum.

[jrellin]

This should really just be in the user manual. The way I have done (and seen this done) is in TrackingAction and hopefully works for all radioactive decays in which the first daughter is of interest:

void TrackingAction::PostUserTrackingAction(const G4Track* track)
{

    // Reset global time on first decay (to avoid waiting for half life of first decay)
    if (track->GetParentID() == 0) { // This track belongs to a primary vertex
       
            // ============Setting secondary tracks to zero global time==============
            G4TrackVector* secondaries = fpTrackingManager->GimmeSecondaries();
            size_t nSeco = secondaries->size();

            if (nSeco > 0){
                for(size_t i=0; i < nSeco; i++) {
                    (*secondaries)[i]->SetGlobalTime(0.);
                    }
     }
}
              

You’ll need to include G4RunManger to get access to fpTrackingManager.