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Forum: Geometry
Re: None Wrong Copy ID of replicated/parametrised volumes (valentina)
Date: 15 Jan, 2015
From: Gabriele Cosmo <Gabriele Cosmo>

Hi Valentina,

for replicas and parameterised volumes, copy-numbers are assigned by Geant4
always starting from 0 in sequential order, this means in your analysis you need
to consider the copy-no associated to the parent volume 'SiTopDetector_phys'
eventually summed to the replica number, in order to identify uniquely the pixel
in the layer of interest!

Cheers, Gabriele

-------------
On Thu, 15 Jan 2015 13:58:21 GMT, valentina wrote:
> Dear All,
> 
> I need to build a set of pixellated layers (a Gamma-ray tracker). More
> precisely, about 2000x2000 pixels in about 100 layers.
> 
> I tried to use both the (i) replicated and the (ii) parametrised volumes
> for the pixels, while the 100 layers are physically built in a loop.
> The replica volume IDs (the pixels) start from 0 for each layer, while
> the layer volume ID is assigned in the G4PVPlacement().
> 
> My problem is that the copy ID of the replica/parametrised volumes for
> the secondaries is wrong, while the position seems to be correct (the
> physical track is correct).
> The problem occurs both with replica and parametrised volumes, which are
> built in a complete different way.
> 
> Could the problem arise from the loop?
> 
> Thank you very much for any suggestion.
> Cheers,
> Valentina
> 
> Example:
> When simulating a muon (for example), the volume IDs are all correct
> until Geant4 starts to track its secondaries. At this point, when the
> particle crosses the vertical layers, sometimes the copy ID of the
> replica (the pixels) is repeated, i.e. the pixel ID is the same of the
> crossed pixel of the previous layer. The effect is the creation of fake
> vertical tracks (see image).
> 
> Code (SiTopDetector_phys is the layer mother volume created in the
> loop):
> i) Replica:
> //Creation of Silicon pixels
> PixelTop_sol = new G4Box("sPixelTop", Pixel_side/2., Pixel_side/2.,
> SiDetector_t/2.);
> PixelTop_log = new G4LogicalVolume(PixelTop_sol,
> SiPixel_mat,"lPixelTop",0,0,0);
> 
> //Creation of Silicon strips
> PixelTopLine_sol = new G4Box("sPixelTopLine", Pixel_side/2.,
> Tray_side/2., SiDetector_t/2.);
> PixelTopLine_log = new G4LogicalVolume(PixelTopLine_sol,
> SiDetector_mat,"lPixelTopLine",0,0,0);
> 
> PixelTop_phys = new G4PVReplica(
> "pPixelPos",PixelTop_log,PixelTopLine_log, kYAxis, Pixel_NY, Pixel_side,
> 0);
> PixelTopLine_phys = new G4PVReplica(
> "pPixelPosTopLine",PixelTopLine_log,SiTopDetector_log, kXAxis, Pixel_NX,
> Pixel_side, 0);
> 
> for (G4int nt = 0; nt < N_layers; nt++)
> {
> 
> SiTopDetector_phys = new
> G4PVPlacement(0,SiUpperModulePos,SiTopDetector_log,"pSiTopDetector",World_log,false,copyM
> + 9*10000);
> 
> }
> 
> ii) Parametrised:
> 
> SiTopParamDetector_sol = new G4Box("sSiTopParamDetector", Pixel_side/2.,
> Pixel_side/2., SiDetector_t/2.);
> SiTopParamDetector_log = new G4LogicalVolume(SiTopParamDetector_sol,
> SiPixel_mat,"lSiTopParamDetector",0,0,0);
> 
> //Pixel physical volumes
> pixelParam = new GeometryST_TrackerParameterisation( Pixel_N,
>                               Pixel_NX,
>                startX,
>                                startY,
>                                Pixel_side );
>  SiTopParamDetector_phys = new
> G4PVParameterised("pixelPhysical",SiTopParamDetector_log,SiTopDetector_log,kUndefined,Pixel_N,pixelParam);
> 
> 
> for (G4int nt = 0; nt < N_layers; nt++)
> {
> 
>  SiTopDetector_phys = new
> G4PVPlacement(0,SiUpperModulePos,SiTopDetector_log,"pSiTopDetector",World_log,false,copyM
> + 9*10000);
> 
> 
> }
> 
>    Attachment:
>       
> http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2015/01/15/05.52-63971-WrongCopyID_tracker.png
> 

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1 None: Re: Wrong Copy ID of replicated/parametrised volumes   (valentina - 15 Jan, 2015)
1 None: Re: Wrong Copy ID of replicated/parametrised volumes   (valentina - 15 Jan, 2015)
2 Feedback: Re: Wrong Copy ID of replicated/parametrised volumes   (Gabriele Cosmo - 15 Jan, 2015)
1 Ok: Re: Wrong Copy ID of replicated/parametrised volumes   (valentina - 15 Jan, 2015)
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