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Warning Infinite tracking loop 

Keywords: tracking, geometry
Forum: Event and Track Management
Date: 04 Apr, 2004
From: Marc Kippen <Marc Kippen>

Myself and others have experienced many problems with particles getting stuck when two volumes share a common boundary. Okay, well the developers claim that this is a FEATURE, and that one should always place little gaps between such volumes. Not exacly satisfying, but it does seem to solve the problem.

Recently, however, I experienced the same problem with two volumes that DO NOT share any common boundaries. The geometry is simple:

World volume = Sphere, 10 cm radius, filled with vacuum Daughter volume = Sphere, 2.7 cm radius, filled with aluminum Common origin for positioning

Using the standard EM physics routines, I start 2 MeV electrons randomly on a sphereical shell just larger than the aluminum shell (2.71 cm radius). Under certain circumstances, the electron tracking goes into an infinite loop as it enters the aluminum.

Anyone know if there is a way around this problem. If not, I will submit it as a bug report.

Cheers,

Marc

For the record, /tracking/verbose = 1 yields:

*********************************************************************************************************
* G4Track Information:   Particle = e-,   Track ID = 1,   Parent ID = 0
*********************************************************************************************************

Step#    X(mm)    Y(mm)    Z(mm) KinE(MeV)  dE(MeV) StepLeng TrackLeng  NextVolume ProcName
    0        9     23.7     9.64         2        0        0         0        Orig initStep
    1     8.76     23.6     9.68         2 6.49e-27    0.244     0.244          D1 Transportation
    2     8.36     23.6     9.64      1.51    0.124    0.404     0.648          D1 eIoni
    :----- List of 2ndaries - #SpawnInStep=  1(Rest= 0,Along= 0,Post= 1), #SpawnTotal=  1 ---------------
    :      8.36      23.6      9.64      0.37                 e-
    :----------------------------------------------------------------- EndOf2ndaries Info ---------------
    3     7.88     23.8     9.97      1.31    0.194    0.714      1.36        Orig Transportation
    4     7.88     23.8     9.97      1.31        0        0      1.36          D1 Transportation
    5     7.88     23.8     9.97      1.31        0        0      1.36        Orig Transportation
    6     7.88     23.8     9.97      1.31        0        0      1.36          D1 Transportation
    7     7.88     23.8     9.97      1.31        0        0      1.36        Orig Transportation
    8     7.88     23.8     9.97      1.31        0        0      1.36          D1 Transportation
    9     7.88     23.8     9.97      1.31        0        0      1.36        Orig Transportation
   10     7.88     23.8     9.97      1.31        0        0      1.36          D1 Transportation
   11     7.88     23.8     9.97      1.31        0        0      1.36        Orig Transportation
.
.
.
ad infinitum

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1 None: Re: Infinite tracking loop   (Vladimir Grichine - 05 Apr, 2004)
1 None: Re: Infinite tracking loop   (liuhm@mail.ihep.ac.cn - 05 Apr, 2004)
(_ None: Re: Infinite tracking loop   (Vladimir Grichine - 06 Apr, 2004)
(_ None: Re: Infinite tracking loop   (Marc Kippen - 13 Apr, 2004)
1 None: Re: Infinite tracking loop   (liuhm@mail.ihep.ac.cn - 13 Apr, 2004)
...
2 None: Re: Infinite tracking loop   (liuhm@mail.ihep.ac.cn - 13 Apr, 2004)
... 1 Message(s)
2 News: Re: Infinite tracking loop   (Marc Kippen - 03 May, 2004)
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