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Forum: Event and Track Management
Re: Question tracking problem? (Dennis Haggerty)
Date: 18 Oct, 2007
From: Makoto Asai <Makoto Asai>

Hi Dennis,

 What happened here is the following. A track (typically electron
with rather low momentum) comes to a volume boundary and
G4Transportation limits its step. Then, multiple scattering process
changes the direction of the momentum inward. Thus, the track is
actually not getting out from the volume. But, with the current
implementation of G4SteppingManager, the track gets out of the
volume once and then takes zero-length additional step to get back.

 This is a known issue for us, and actually it causes miscount of
the surface flux, for example. We do not have immediate cure of
this issue.

Makoto

> -----Original Message-----
> From: Dennis Haggerty [mailto:Dennis.Haggerty@jhuapl.edu] 
> Sent: Thursday, October 18, 2007 8:15 AM
> To: publichypernews
> Subject: tracking problem?
> 
> *** Discussion title: Event and Track Management
> Email replies to PublicHyperNews@slac.stanford.edu must include:
>   In-Reply-To: <"/eventtrackmanage/722"@geant4-hn.slac.stanford.edu>
>   Subject: ...change this to be about your reply.
> 
> I'm having what I think is a tracking problem. I'm running a 
> very simple
> shield simulation using G4Box. When I run electrons into the material
> sometimes they come out of the material and then reenter the 
> material. I
> have two slabs, the first is very thin with material set to 
> Vacuum. The
> second slab is WCu (but I get the same thing if I use a pure Al slab).
> There is no energy loss in this process. I also get the same 
> answer if I
> use the first slab and set the second slab to Vacuum. I cannot figure
> out what is turning them around. I'm running 4.9.0.p01
> 
> Note step 25 in the tracking log below.
> 
> Any suggestions?
> 
> Regards,
> 
> Dennis
> 
> **************************************************************
> *******************************************
> * G4Track Information:   Particle = e-,   Track ID = 1,   
> Parent ID = 0
> **************************************************************
> *******************************************
> 
> Step#      X         Y         Z        KineE    dEStep   
> StepLeng  TrakLeng    Volume     Process
>     0     -5 cm   -2.2 Ang   5.3 Ang  1.47 MeV     0 eV      
> 0 fm      0 fm        Layer    initStep
>     1 -5e+03 fm   -2.2 Ang   5.3 Ang  1.47 MeV     0 eV      
> 5 cm      5 cm        Layer  Transportation
>     2  5e+03 fm   -2.2 Ang   5.3 Ang  1.47 MeV     0 eV  
> 1e+04 fm      5 cm           D1  Transportation
>     3   1.73 mm   -2.2 Ang   5.3 Ang  1.47 MeV     0 eV   
> 1.73 mm   5.17 cm        Layer  Transportation
>     4   1.75 mm  -2.54 um  -5.46 um   1.44 MeV  26.9 keV  
> 19.2 um   5.17 cm           D2         msc
>     5   1.75 mm  -1.06 um  -5.37 um   1.42 MeV  4.08 keV  
> 3.41 um   5.18 cm           D2   LowEnBrem
>     6   1.76 mm     12 um   -107 nm    1.4 MeV  20.9 keV  
> 19.2 um   5.18 cm           D2         msc
>     7   1.77 mm   17.2 um   3.79 um   1.37 MeV  10.6 keV  
> 8.71 um   5.18 cm           D2  LowEnergyIoni
>     8   1.77 mm   19.8 um   10.3 um   1.35 MeV  8.06 keV  
> 8.08 um   5.18 cm           D2   LowEnBrem
>     9   1.78 mm   33.7 um   16.7 um   1.32 MeV  26.3 keV  
> 19.2 um   5.18 cm           D2         msc
>    10    1.8 mm     39 um   24.2 um   1.31 MeV  11.3 keV  
> 19.2 um   5.18 cm           D2         msc
>    11   1.81 mm     52 um     21 um   1.29 MeV  27.5 keV  
> 19.2 um   5.18 cm           D2         msc
>    12   1.81 mm   69.1 um   27.2 um   1.26 MeV  22.4 keV  
> 19.2 um   5.19 cm           D2         msc
>    13   1.81 mm     87 um   26.9 um   1.24 MeV  23.7 keV  
> 19.2 um   5.19 cm           D2         msc
>    14   1.82 mm    103 um     34 um   1.21 MeV  33.6 keV  
> 19.2 um   5.19 cm           D2         msc
>    15   1.83 mm    110 um   40.1 um   1.19 MeV  19.3 keV  
> 19.2 um   5.19 cm           D2         msc
>    16   1.85 mm    121 um   38.9 um   1.16 MeV  21.6 keV  
> 19.2 um   5.19 cm           D2         msc
>    17   1.86 mm    137 um   37.5 um   1.14 MeV  28.2 keV  
> 19.2 um    5.2 cm           D2         msc
>    18   1.85 mm    146 um   25.4 um   1.11 MeV  24.4 keV  
> 19.2 um    5.2 cm           D2         msc
>    19   1.82 mm    142 um   26.2 um   1.07 MeV  37.1 keV  
> 25.4 um    5.2 cm           D2         msc
>    20   1.81 mm    159 um     22 um   1.05 MeV    27 keV  
> 25.4 um    5.2 cm           D2         msc
>    21   1.79 mm    168 um   18.3 um  1e+03 keV  48.4 keV  
> 25.4 um   5.21 cm           D2         msc
>    22   1.76 mm    168 um   21.8 um    973 keV  26.4 keV  
> 25.4 um   5.21 cm           D2         msc
>    23   1.74 mm    162 um   30.7 um    940 keV  33.1 keV  
> 25.4 um   5.21 cm           D2         msc
>    24   1.73 mm    160 um   41.7 um    912 keV  28.4 keV  
> 23.5 um   5.21 cm           D2  Transportation
>    25   1.73 mm    160 um   41.7 um    912 keV     0 eV      
> 0 fm   5.21 cm        Layer  Transportation
>    26   1.73 mm    162 um   48.7 um    879 keV  8.49 keV  
> 8.01 um   5.21 cm           D2  LowEnergyIoni
>    27   1.73 mm    163 um   49.9 um    878 keV  1.36 keV  
> 1.38 um   5.21 cm           D2  Transportation
>    28  5e+03 fm   2.01 mm   4.96 mm    878 keV     0 eV   
> 5.52 mm   5.77 cm        Layer  Transportation
>    29 -5e+03 fm   2.01 mm   4.96 mm    878 keV     0 eV 
> 3.19e+04 fm   5.77 cm           D1  Transportation
>    30  -17.4 cm   18.8 cm     50 cm    878 keV     0 eV   
> 55.7 cm   61.5 cm        Layer  Transportation
>    31  -17.6 cm     19 cm   50.5 cm    878 keV     0 eV   
> 5.63 mm     62 cm   Calorimeter  Transportation
>    32  -17.8 cm   19.2 cm     51 cm    878 keV     0 eV   
> 5.63 mm   62.6 cm   OutOfWorld  Transportation
> 
> 

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1 Question: RE: tracking problem?   (Dennis Haggerrty - 18 Oct, 2007)
(_ None: RE: tracking problem?   (Makoto Asai - 18 Oct, 2007)
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