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Question Step Length 

Forum: Physics List
Date: 21 Aug, 2012
From: Michael Douglass <Michael Douglass>

Hi,

I am having some problems with my Physics list. I am using a Modular physics list (G4EmDNAPhysics()). In my geometry I have several small boxes inside each other which are then placed in a water medium. When I place my isotropic radiation source in the center of the inner most box, the particles appear to transport directly to the edge of the next box without interactions. Then, when the particle leaves the boxes and enters the water medium, the step length changes and starts interacting on micron scales (see output below).

Can anyone tell me why the step length is so large in the boxes and so small in the water?

Thanks

******************************************************************************** G4Track Information:   Particle = proton,   Track ID = 1,   Parent ID = 0 
******************************************************************************* 
Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName 
    0        0        0        0         1        0        0         0     Nucleus initStep 
    1 -0.00167 -0.00108 -0.000207         1        0    0.002     0.002   Box1 Transportation 
    2  -0.0025 -0.00163 -0.00031         1        0    0.001     0.003   Box2 Transportation 
    3 -0.00334 -0.00217 -0.000414         1        0    0.001     0.004   Box3 Transportation 
    4 -0.00417 -0.00271 -0.000517         1        0    0.001     0.005   Box4 Transportation 
    5  -0.0834  -0.0542  -0.0103         1        0    0.095       0.1    Box5 Transportation 
    6  -0.0834  -0.0542  -0.0103         1        0    1e-05       0.1 OuterWaterBox Transportation 
    7  -0.0834  -0.0542  -0.0103         1 1.08e-05 1.31e-06       0.1 OuterWaterBox proton_G4DNAIonisation 
    8  -0.0834  -0.0542  -0.0103         1 1.34e-05 1.63e-06       0.1 OuterWaterBox proton_G4DNAIonisation 
    9  -0.0834  -0.0542  -0.0103         1 1.08e-05 8.51e-06       0.1 OuterWaterBox proton_G4DNAIonisation 
   10  -0.0834  -0.0542  -0.0103         1 1.08e-05 1.18e-06       0.1 OuterWaterBox proton_G4DNAIonisation 
   11  -0.0834  -0.0542  -0.0103         1 1.61e-05 1.71e-06       0.1 OuterWaterBox proton_G4DNAIonisation 
   12  -0.0834  -0.0542  -0.0103         1    1e-05 2.23e-06       0.1 OuterWaterBox proton_G4DNAExcitation 
   13  -0.0834  -0.0542  -0.0103         1 1.34e-05 1.63e-06       0.1 OuterWaterBox proton_G4DNAIonisation 
   14  -0.0834  -0.0542  -0.0103         1 1.61e-05 8.76e-07       0.1 OuterWaterBox proton_G4DNAIonisation 
   15  -0.0834  -0.0542  -0.0103         1 1.61e-05 1.24e-06       0.1 OuterWaterBox proton_G4DNAIonisation 
   16  -0.0834  -0.0542  -0.0103     0.999 1.61e-05 1.31e-06       0.1 OuterWaterBox proton_G4DNAIonisation 
   17  -0.0834  -0.0542  -0.0103     0.999 1.08e-05 9.12e-06       0.1 OuterWaterBox proton_G4DNAIonisation 
   18  -0.0834  -0.0542  -0.0103     0.999 1.08e-05 1.39e-07       0.1 OuterWaterBox proton_G4DNAIonisation 
   19  -0.0834  -0.0542  -0.0103     0.999 1.08e-05 6.85e-07       0.1 OuterWaterBox proton_G4DNAIonisation 
   20  -0.0834  -0.0542  -0.0103     0.999 1.08e-05 3.67e-07       0.1 OuterWaterBox proton_G4DNAIonisation 
   21  -0.0834  -0.0542  -0.0103     0.999 1.61e-05 1.11e-07       0.1 OuterWaterBox proton_G4DNAIonisation 
   22  -0.0834  -0.0542  -0.0103     0.999 1.61e-05 4.46e-07       0.1 OuterWaterBox proton_G4DNAIonisation 
   23  -0.0834  -0.0542  -0.0103     0.999 1.08e-05 9.72e-08       0.1 OuterWaterBox proton_G4DNAIonisation 
   24  -0.0835  -0.0542  -0.0103     0.999  1.6e-05 1.23e-05       0.1 OuterWaterBox proton_G4DNAIonisation 
   25  -0.0835  -0.0542  -0.0103     0.999 1.61e-05 3.52e-06       0.1 OuterWaterBox proton_G4DNAIonisation 

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1 Idea: Re: Step Length   (Vladimir Ivanchenko - 27 Aug, 2012)
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