Is it possible to allow all the primary radioactive nucleus inside the target to decay while they are irradiated by an external particle beam?

Hi everyone,
I’m wondering if I can acquire the radioactive decay data of the original target materials, and at the same time, of the activation products produced from nuclear reactions caused by an incident particle beam. I suppose it would require some specific setup of the primary event generator, but I have no idea how to right now. Your suggestions and help are greatly apprecieated. : )


_Geant4 Version: 4.11.beta
_Operating System: Ubuntu 21.04

Big picture: “materials” don’t decay. When you create your geometry, you specify G4Materials made of G4Element and G4Isotope instances. Those are all “materials,” and they just sit there getting hit by your primaries.

As you know (noted above), when you irradiate your geometry, you can get activation products as secondaries from interaction. Those G4Track objects are identified by particle types which are G4Ions instances, different from G4Isotope above.

It sounds like you want to get event data that includes both beam effects and contaminant backgrounds. That’s not easy, because Geant4 operates on a “particle event” level, not an “activity” level. If you added an atom (G4ions) of one of the radiological contaminants to your event it would certainly decay, but the decay would have a timestamp set by the half-life, probably much later in time than your beam particles.

A better solution would be to construct a background spectrum for each of your known contaminants as separate jobs. Then you can weight each of those spectra according to the measured activity of your target (e.g., from assays of the components), and sum or compare that spectrum with the beam data.

Thank you for your kind suggestion. As the materials are set as un-decayable, I think the adopting parrellel world mode might be a solution to a one-stop simulation.
Regarding the ions, another question comes to my mind. How do Geant4 handle the ionic charge state of the activation products, are they defaultly set as fully ionized right after they are produced from a nuclear reaction?