Turning off some phenomenons

Beginner with Geant-4.

In my simulation, I am using the G4EmLivermorePhysics and G4EmPenelopePhysics library. Say I want to turn on or off a particular phenomenon, say fluoresence. Do I just in the macro (run.mac) turn off the following fluoresence like:

/process/em/fluo false

More so, does this way:

G4VAtomDeexcitation * de = new G4UAtomicDeexcitation ();
G4LossTableManager :: Instance () -> SetAtomDeexcitation (de);
from -> SetFluo (false);

is equivalent to the previous one.

Or, even if I turn off fluoresence, Geant-4 will continue to consider the fluoresence phenomenon ?

Thank you!

Hi, if you turn off fluorescence in either way, the fluo will not be modelled.

Dear @guatelli,

Thank you so much for your response.

I tested both of these methods (for 1.0, 2.0 3.0 and 6.0 MeV), but it made no difference to the dose distribution, exactly the same dose “numbers” everywhere.

Note, I have no doubts about my Geant benchmark and results since I validated it with another Monte-Carlo code with less than 0.2% difference everywhere.

I find it weird that turning off these phenomena (in my case fluorescence, Auger, Cascades and bremsstrahlung) doesn’t make any difference. Whereas, for example, activating the Pixe (with G4EmParameters::Instance()-> SetPixe(false); or /process/em/pixe true ) makes a difference.

If you have an explanation of why this is observed and how to proceed to achieve this goal, will be appreciated.

Ma source is a gamma source. My simulation is a coupled photon-electron-positron simulation.

Thank you.

my understanding is that you are modelling an X-ray beam with energy 1, 2, 3 6 MeV on water. Correct? if this is the case, if you adopt a mm voxel size, you will not see any dose effect due to Auger or fluorescence. This is my impression because you are averaging the dose in large voxels. You need to reduce the voxel size a lot to be able to eventually see these effects on the calculation of the energy deposition (e.g. voxels with sub-micrometer dimensions). For what concerns brem, I did a rapid, rough calculation. Let’s suppose you have a 6 MeV electron, the radiation yield in oxygen is about 2%, lower in hydrogen (0.3%). Therefore the contribution of brem to the dose in the cases that you studied is not significant. Again, this is in the hypothesis that we are talking about X-rays in water.

I ran TestEm11 with attached macro.
Histo 6 shows that Auger e- are effectively created.
We can also double check this fact with few events in tracking/verbose 2
Histo 1 shows that they have negligible effect on edep profile.

If you have Geant4 10.7, you can also play with TestEm14 or rdecay01, macro atomicDeexcitation.mac

naceur.mac.txt (724 Bytes)


Thanks a lot for your answers (@guatelli & @maire). Thank you @maire for your example.

I was able to find the error. I am able to see the effect of turning on and off the bremsstrahlung, fluoresence, pixe, augers, cascades correctly for 1mm voxels.

The problem was an error I had in my

 SetCutValue(defaultCutValue_g, "gamma");
 SetCutValue(defaultCutValue_e, "e-");
 SetCutValue(defaultCutValue_p, "e+");

CutValues were too high. It automatically killed all secondary particles in the latest version (was a misinterpretation by our team).

Now it’s corrected and everything is perfect.

Thank you so much.