No electrons created in ionization process

Hi!

I am quite new to Geant4 so apologies if this question is somewhat unclear :slight_smile:

In my simulation I am trying to build a neutron detector in which neutrons react with B-10 to create Li-7 and alpha particles. However, the detection system relies on the alpha particles and the Li nuclei to ionize the gas in the chamber, so that we get electrons and ions that can then be detected as a current. But when I run this simulation I only get Li-7 and alpha particles which undergo some ionization process, but the simulation does not track any free electrons from here. If I lower the threshold energy for electron generation I only get new electrons from Compton scattering. What could I be doing wrong?


_Geant4 Version: 11.3.0
_Operating System: Alma Linux 9.5
_Compiler/Version: gcc 13.3.0
_CMake Version: 3.31.5

What do you mean by threshold energy? You should be using production/range cuts as that is the paradigm used in Geant. And the point is that you will need to set this variable very low for gas ionization.

You can use Geant4 Regions to define production cuts exclusive to the gas (also in those slides in the url) to avoid excessive computations for particles outside of the gas. I also suspect you might need to turn on “low energy” em physics. If your gas logical region is called “GasLogReg” then:

G4EmParameters* emOptions = G4EmParameters::Instance(); 
emOptions->SetDeexActiveRegion("GasLogReg", true, true, true); // deexc., auger, pixe

This will turn on (atomic) deexcitation, auger emission, and proton induced x-ray emission (pixe).