45// Stacking action used in the adjoint simulation. It is responsible to kill a primary forward particle before it is traked in the forwrad phase
46// if the last adjoint particle did not reach the adjoint surface. Was needed for the new design where the G4AdjointSimManager is no more an extension
47// of the G4RunManager. If the primary particles is not killed before being tracked in the sensitive geometry, the User Stacking action
48// can be used duiring the forward phase if specified by the method G4AdjointSimManager::UseUserStackingAction(Bool).