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Forum: Geometry
Re: Question Particle is skipping or stucked in certain region during the tracking (Nahee Park)
Re: Feedback Re: Particle is skipping or stucked in certain region during the tracking (Gabriele Cosmo)
Date: 05 Feb, 2009
From: Nahee Park <Nahee Park>

Hi, Gabriele.

Thank you very much for your comments. I added the geometrical tolerance - I got the surface tolerance of 0.15 mm (by "G4GeometryTolerance::GetInstance()->GetSurfaceTolerance()") after setting the world maximum extent. But, I still have the "skipping" problem.

Analytically there should not be any overlapping volumes or shared surfaces - I checked the semi-axes of each ellipsoids several times. (The minimum altitude difference from one ellipsoid to the other is 450.1 meter which, I think, reasonably separated.)

Also I checked the geometry by using "/geometry/test/grid_test" command. After the long list of errors which is partially shown below, I got the message of "GeomTest: no daughter volume extending outside mother detected. GeomTest: no overlapping daughters detected."

>> Part of error messages from geometry check
--------------------------------------------
 ....
GeomTest Error: SolidProblem
    Spurious exiting intersection point
    Solid name = air_layer_solid268
    Local position =    6.64212e+08   7.38014e+07  -3.11735e+08 cm
GeomTest Error: SolidProblem
    Solid has odd number of intersection points
    Solid name = air_layer_solid268
    Local position =    6.64212e+08   7.38014e+07             0 cm
GeomTest Error: SolidProblem
    Unmatched intersection point
    Solid name = air_layer_solid268
    Local position =    6.64212e+08   7.38014e+07   3.11735e+08 cm
----------------------------------------------

I tried to check whether these GeomTest Errors are from my geometry setting or somewhere else. So I put a single Ellipsoid like below.

----------------------------------------------
  Rearth_equator = 6378137 * m ;
  Rearth_pole    = 6356752.3 * m ;

  LpxSemiAxis = Rearth_equator + 36*km ;
  LpySemiAxis = Rearth_equator + 36*km;
  LpzSemiAxis = Rearth_pole    + 36*km ;

  G4Ellipsoid* sAirLayert = new G4Ellipsoid("air_layer_solid0",
                         LpxSemiAxis,      //pxSemiAxis
                         LpySemiAxis,      //pySemiAxis
                         LpzSemiAxis,      //pzSemiAxis
                         -LpzSemiAxis,      //pzBottomCut
                         LpzSemiAxis   ); //pzTopCut
----------------------------------------------------

With this single ellipsoid, I got similar list of errors. (below is the last 3 errors from grid_test.)

----------------------------------------------------
GeomTest Error: SolidProblem
    Spurious exiting intersection point
    Solid name = air_layer_solid0
    Local position =    5.90411e+08   1.62363e+08  -1.90321e+08 cm
GeomTest Error: SolidProblem
    Solid has odd number of intersection points
    Solid name = air_layer_solid0
    Local position =    5.90411e+08   1.62363e+08             0 cm
GeomTest Error: SolidProblem
    Unmatched intersection point
    Solid name = air_layer_solid0
    Local position =    5.90411e+08   1.62363e+08   1.90321e+08 cm
-------------------------------------------------------

When I tried with single G4Orb or G4Sphere, no error was shown.So I guess this happens for the ellipsoid.

Summarizing the status.

- "SetWorldMaximumExtent" didn't change the status of skipping geometry.

- Speaking from the numbers used for the setting, I don't think there is any overlapping or shared surface in my geometry.

- grid_test report no overlapping of geometry. But, it shows other errors about the solid problem which seems to be related to the ellipsoidal solid shape.

I found the "skipping" problem seems to have energy dependence at least for the electron injection case.

-------------------------------------------------------------------
energy of electron         number of events with skipping problem
 (vertical down)            (5k events were tested)
-------------------------------------------------------------------
   1 TeV                              0
   5 TeV                              3
   10 TeV                             10
   20 TeV                             157
--------------------------------------------------------------------

Only skipping of one particular layer was checked - so this would be the minimum number of events with skipping problem.

Thank you.

                                    Nahee

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1 Feedback: Re: Particle is skipping or stucked in certain region during the tracking   (Gabriele Cosmo - 05 Feb, 2009)
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