Creating secondary electrons below 1 keV

Physics Lists
1

Dear forum,

I would like to simulate the creation of secondary electrons in various materials in the energy range down to 200 eV. I have read through the manuals and various posts on this forum which deals (atleast partially) with the subject, but I still dont manage to configure the simulations so that secondary electrons below 1 keV are generated (tracking below 1 kev is done correctly). Here are the relevant details of my simulation:

Geant4: 11.0.0
OS: Ubuntu 22.04
Settings in .mac file relevant for production and tracking:

  • /cuts/setLowEdge 300 eV
  • /run/setCut 10 fm (I have set it absurdly low to be sure that 1 kev electrons should pass)
  • /process/em/lowestElectronEnergy 10 eV
    Physics-list: QGSP_BIC_HP_EMZ (also tried with _PEN, _LIV)

The output shows that a 1 keV cut is applied nonetheless:

Material : G4_AIR
Range cuts : gamma 10 fm e- 10 fm e+ 10 fm proton 10 fm
Energy thresholds : gamma 1 keV e- 1 keV e+ 1 keV proton 0.001 meV

and looking through the saved data, I dont see any secondary electrons produce below 1.02 keV

Anyone has an idea what I am missing? Any help is appreciated

best
Phermi

2

Here a macro for example TestEm14, its printout, and the plot of histogram 3.
The key point is line ˜164 of PhysicsList.cc :
G4ProductionCutsTable::GetProductionCutsTable()-> SetEnergyRange(100eV, 1GeV)
which defines the range of the precomputed tables.

petter.mac.txt (375 Bytes)
petter.out.txt (1.9 KB)

petter
petter698×475 25.7 KB

3

Hello,

Thanks for the reply. I could reproduce the result using the example you suggested. I’m now building my own physicslist instead of using a reference one, and I set the energy cuts in the setcut function as you indicated. Looking at the output, the values takes effect

Electromagnetic Physics Parameters
Min kinetic energy for tables 109 eV
Max kinetic energy for tables 1 GeV

but the energy thresholds are still at 1 keV

Index : 0 used in the geometry : Yes
Material : G4_AIR
Range cuts : gamma 10 nm e- 10 nm e+ 10 nm proton 10 nm
Energy thresholds : gamma 1 keV e- 1 keV e+ 1 keV proton 1 eV

so there is an additional problem somewhere. I continue to work on it.

best
P.

4

for time being, I do not understand what can happen ! …