Inconsistent range cuts for secondary electrons from a gamma photon

Physics Processes, Models and Cross Sections
1

Hello all,

I set the production cut for electrons using.

/run/setCutForAGivenParticle e- 1.5 mm

From germanium, this corresponds to 1.22 MeV (from the verbosez0

Index : 2     used in the geometry : Yes
 Material : ge
 Range cuts        :  gamma  1 mm     e-  1.5 mm     e+  1 mm  proton 1 mm 
 Energy thresholds :  gamma  20.6438 keV    e-  1.22809 MeV    e+  831.682 keV proton 100 keV
 Region(s) which use this couple : 
    DefaultRegionForTheWorld

But from the step output, I can see the electrons of energy, which are much less than 1.22 MeV, being produced in germanium.

ParentID: 1, TrackID: 3, t: 0.744423, Particle Name: gamma, Energy: 160.8 eV , Crystal: 1
ParentID: 3, TrackID: 17, t: 0.767117, Particle Name: e-, Energy: 16.91 eV , Crystal: 1
ParentID: 3, TrackID: 16, t: 0.767117, Particle Name: e-, Energy: 16.91 eV , Crystal: 1
ParentID: 3, TrackID: 15, t: 0.767117, Particle Name: e-, Energy: 9.26 eV , Crystal: 1
ParentID: 3, TrackID: 14, t: 0.767117, Particle Name: e-, Energy: 9.26 eV , Crystal: 1
ParentID: 3, TrackID: 13, t: 0.767117, Particle Name: e-, Energy: 48.6 eV , Crystal: 1
ParentID: 3, TrackID: 12, t: 0.767117, Particle Name: e-, Energy: 47.34 eV , Crystal: 1
ParentID: 3, TrackID: 11, t: 0.767117, Particle Name: e-, Energy: 8.63 eV , Crystal: 1
ParentID: 3, TrackID: 10, t: 0.767117, Particle Name: e-, Energy: 9.26 eV , Crystal: 1
ParentID: 3, TrackID: 9, t: 0.767117, Particle Name: e-, Energy: 972.84 eV , Crystal: 1
ParentID: 3, TrackID: 8, t: 0.767117, Particle Name: e-, Energy: 1.14579 keV, Crystal: 1
ParentID: 3, TrackID: 7, t: 0.767117, Particle Name: e-, Energy: 8.6214 keV, Crystal: 1
ParentID: 3, TrackID: 6, t: 0.767117, Particle Name: e-, Energy: 285.693 keV, Crystal: 1
ParentID: 3, TrackID: 5, t: 0.744423, Particle Name: e-, Energy: 85.776 keV, Crystal: 1
ParentID: 3, TrackID: 4, t: 0.623102, Particle Name: e-, Energy: 80.4791 keV, Crystal: 1

I am sure I am doing something silly or unclear with the production cuts. Do I need to set this production cut to gammas to see the effect on elections?

Since the electrons are being produced as secondaries from primary gamma tracks, they should not be produced at 1.22 MeV, and their energy deposited should go in the step.

Can anyone please offer any help in this regard . Thank You.

2

No, the cuts apply to the particle to be tracked (here, your secondary electrons). In addition to setting the cut values, as you have done, in our simulation we some additional flags we set (which might be redundant). In our code, we have

  thePL->SetApplyCuts(doApply, "all");
  G4EmParameters::Instance()->SetApplyCuts(doApply);

(where thePL is our internal variable pointing to the physics list in use, your code will have a different variable name, of course).

Then, we have a macro command

/process/em/deexcitationIgnoreCut false

This is the one I expect will get rid of those little eV-scale electrons.

1 Like
3

Thanks a lot, I’ll try to implement it.

4

To confirm Michael answer :
By default, production threshold is applied only to e- produced by ionisation, because those e- are too abundant at low energies (say below ~1 keV).
To force to apply production threshold to all electromagnetic processes, add :
/process/em/applyCuts true
/process/em/deexcitationIgnoreCut false

1 Like
5

Thank You for the valuable input, I will try using this command.