Dear, G4 User
I am analysing the detector signal using the X-ray histogram from the RG as the source term.
I used to use PhysicsList Factory but switched to defining my own PhysicsList and when I added ‘G4RadioacticeDecayPhysics’, I noticed that unlike before, a large number of secondary electrons occurred in a single event. I don’t understand this result from my knowledge. Can anyone tell me why this happens when I am not simulating radioactive decay? ‘G4RadioacticeDecayPhysics’ seems to be a commonly used physics model. The results I expect are similar when I define only ‘G4EmStandardPhysics_option3’.
Please let me know if you have a reference for the physics model.
Geant4 Version: geant4-10-07-patch-03
Operating System: window-WSL
Compiler/Version: 11.3.0
CMake Version: 3.22.1
Hi @Junsung
I think Radioactive decay enables several processes which are not enabled by EM3, and that could lead to creation of secondary electrons of very low energy (such as electron conversion, Auger process). You can check the process that create those electrons by enabling /tracking/verbose 2. May I ask what is the energy of such electrons?
As a rule of thumb, it is better to start with the most complete physics list (eg, hadronic+EM4+radioactive decay) and use it as reference. Then, one can try removing some parts (eg, if after removing the radioactive decay module the results are still comparable with the experimental data)
If your experimental setup consist in detectors for charged particles or x-rays at low (~<1 MeV) energy, it is likely that only electromagnetic physics list is enough. You may want to try with EM4 (or EMZ) which are the most accurate physics lists for EM processes.
At the end of the beginers course there is a short explanation of the difference between EM0 and EM4, and its impact in the simulation accuracy:
Best,
Alvaro
Dear, @atolosad
First of all, thank you for your reply.
I am currently using the energy spectrum under 170 keV (RG).
As you mentioned I thought that EM physics would be sufficient due to the low energy, but I am trying to understand why the results are so different when decay physics is added.
I will compare the results of different physics models based on the ‘most complete physics list’ you provided.
Best,
Junsung
Dear @Junsung
I think Radioactive decay enable atomic relaxation models (ARM), which may lead production of low energy electrons. You can switch off the ARM using the UI commands or C++:
https://geant4-userdoc.web.cern.ch/UsersGuides/ForApplicationDeveloper/html/TrackingAndPhysics/physicsProcess.html?highlight=auger#atomic-deexcitation
Best,
Alvaro
Dear @atolosad
I am looking at results with and without Atomic Relaxation Models (ARM).
Thank U for your help!
Best,
Junsung