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Question Low boundary of Energy threshold? 

Forum: Physics List
Date: 08 Jun, 2005
From: luhao <luhao>

Hello

I am trying to simulate the physical procedure in an ionization chamber.
I found that the number of produced electrons is much less than the theory
expected. So I use "/tracking/verbose 1" to see the exact tracking process,
I found that there are no secondary electons tracks after LowEnergyIoni/eIoni
 process.
For Example:
----------------------START OUTPUT------------------------------
*********************************************************************************************************
* G4Track Information:   Particle = e-,   Track ID = 2,   Parent ID = 1
*********************************************************************************************************

Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName
    0     2.43     1.15    -2.17   0.00269        0        0         0     ExpHall initStep
    1     2.48     1.18    -2.13         0  0.00471    0.222     0.222     ExpHall eIoni <===============Here,Where is the new electrons? 
------Event 0 ends
----------------------END OUTPUT------------------------------
I thought that might be caused by the energy threshold. I tried to 
set cuts with less value and found there is a low boundary of energy 
threshold:

cutsvalue energy threshold(e-) 0.1*um 990ev 1*um 990ev 10*um 990ev 1*m 449.547keV

My questions are: 1.Is it because of the threshold of energy that cause geant4 not to track the secondary electrons after LowEnergyIoni?(I think the LowEnergyIoni should produce secondary electrons).

2.Is 990ev really the low boundary of energy threshold? I saw the words:
--------------------------
These models are implemented in the toolkit to extend the coverage of 
electromagnetic interactions of photons and electrons down to 250 eV, 
                                                              ^^^^^^^
and of protons, ions and antiprotons down to <1  keV.
--------------------------
from http://www.ge.infn.it/geant4/lowE/

Thanks!

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