I was having issues with low energy electrons being generated in my scintillator and shielding materials which were around 0.25keV. This was puzzling because I had set a minEnergyRangeProductionCuts of 1keV in my physics list so it should not happen.
As you can see there is some process msc with corresponds to multiple scattering (a lot of elastic scatters merged into one) which generates very low energy electrons.
Should we try to include this kind of processes into our production cuts? In my case they generate a very high number of useless tracks which really slows visualization among other things.
Why are these electrons being produced by MSC mostly inside my scintillator (plastic BC408)? Shouldn’t they be produced by ionization (muonIoni or similar process name)?
But these electrons were not produced in my simulations (the ones I showed you) in the very same material. It is something weird. Have you checked this simulation in a different REST version?
My definition of BC408 material is the one Javier has mentioned.
I am not able to run this simulations with lower versions of REST because they take too much time (maybe more than 100x more than with today’s dev version) because inefficient track indexing in previous versions which has running time with polynomial dependence of the number of tracks and these kind of simulations generate over 20000 tracks per event so its not possible to run them, which makes me wonder if I am doing something wrong…
edit: my definition of BC408 is as Javier’s too.
This is an image of a simulation where the only active volume is the gas. I believe there should not be electrons on the outside of the sensitive volume am I correct? maybe this can point towards the explanation @jgalan@luzon
No, there should be electrons in any volume, but “energy depositions” only in the active volumes, as happens in your simulation, Have you tried defining only the Veto as both “active” and sensitive" volumen? It could be related to the fact that you are imposing same “step” and cuts in very different materials.
This is what I get after setting the top very as the only active and sensitive volume. I get electrons everywhere but only energy deposits in the veto.
Yes, if you are using the “official” materials.xml file it should be the same. But my question was if you change the material of the VETO for any other material, the problem dissapears?
Also, I was wondering if MEE value affects your results.
I see fewer electrons and with different energies, but they also seem to be produced by MSC process:
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ SubEvent ID : 0 Global timestamp : 1.525317984e-10 seconds Track ID : 13658 Parent ID : 1 Particle : e- Time track length : 3.5603e-11 us Origin : X = 157.85mm Y = 313.5mm Z = -200.75mm Ekin : 0.03331 keV ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Hit 0 process : msc volume : 0 X : 157.85 Y : 313.5 Z : -200.75 mm Edep : 0.03331 keV ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ SubEvent ID : 0 Global timestamp : 1.525317984e-10 seconds Track ID : 13659 Parent ID : 1 Particle : e- Time track length : 3.5819e-11 us Origin : X = 157.85mm Y = 313.5mm Z = -200.75mm Ekin : 0.02735 keV ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Hit 0 process : msc volume : 0 X : 157.85 Y : 313.5 Z : -200.75 mm Edep : 0.02735 keV ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ SubEvent ID : 0 Global timestamp : 1.525317984e-10 seconds Track ID : 13660 Parent ID : 1 Particle : e- Time track length : 1.6218e-09 us Origin : X = 157.85mm Y = 313.5mm Z = -200.75mm Ekin : 7.7358 keV ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Hit 0 process : msc volume : 0 X : 157.85 Y : 313.5 Z : -200.75 mm Edep : 0.26263 keV Hit 1 process : eIoni volume : 0 X : 157.85 Y : 313.5 Z : -200.75 mm Edep : 7.3573 keV ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ SubEvent ID : 0 Global timestamp : 1.525332789e-10 seconds Track ID : 13661 Parent ID : 13660 Particle : e- Time track length : 3.2084e-11 us Origin : X = 157.85mm Y = 313.5mm Z = -200.75mm Ekin : 0.05768 keV ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Hit 0 process : msc volume : 0 X : 157.85 Y : 313.5 Z : -200.75 mm Edep : 0.05768 keV ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ SubEvent ID : 0 Global timestamp : 1.525329692e-10 seconds Track ID : 13662 Parent ID : 13660 Particle : e- Time track length : 3.2045e-11 us Origin : X = 157.85mm Y = 313.5mm Z = -200.75mm Ekin : 0.05826 keV ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Hit 0 process : msc volume : 0 X : 157.85 Y : 313.5 Z : -200.75 mm Edep : 0.05826 keV
Then it seems this is something related with the MSC process. It looks like the production cuts have no effect on the generation of those electrons. Perhaps the issue could be raised to the Geant4 forum.
I am not sure if in other EM PhysicsLists the MSC process is replaced by something else. You could try to switch the EM list by Penelope or Standard and check the result.
We have discovered these electrons appear on geant4 version 10.6.0 but not on version 10.4.1 so we recommend downgrading to version 10.4 in order to avoid unnecessary tracks (this can reduce the number of tracks in a factor of 10-100
