//secondary energy dep
  const G4Track* track = aStep->GetTrack();
  if (track->GetParentID() > 0)   // this step belongs to a secondary
  {
      G4double edep = aStep->GetTotalEnergyDeposit();

      if (edep > 0)
	G4cout << "ParentID: " << track->GetParentID()
    << " edep: " << aStep->GetTotalEnergyDeposit() / keV
    << G4endl;