How to add gamma source instead of setting particle gun

Particles, Track, Event, Run and Biasing
1

Geant4 Version: 11.3.2
Operating System: Windows
Compiler/Version: VS 2022
CMake Version: CMake 4.1.0

I am trying to get spectra of some isotopes, using my scintillation detector simulation which i have made. For example i have just used absolute energy of Cs-137 and use particle gun for it but how should I add real decay process for isotopes like Ba-133 or Eu-152. I just want to know way to simulate these gamma emitter isotopes.

2

You have to add radioactive decay physics. There is an entire set of examples here. Then in your macro if you place these at rest they will decay in expected ways.

Since you have geant 11.3 you probably will need this command somewhere in the macro after initializing the run but before running particles:

/process/had/rdm/thresholdForVeryLongDecayTime 1.0e+60 year

Geant4 will follow all the decays down to the stable isotopes unless confied with

/process/had/rdm/nucleusLimits [Amin] [Amax] [Zmin] [Zmax]

The examples in the link also include Co60, Na22, etc.

3

Thanks a lot ,It worked by adding this command before running particle gun. Now I am getting gamma decay by adding radioactive element from G4IonTable and using radioactive decay physics.