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Dear John and Michael, thanks for the suggestions. Suppose I have a G4Tubs object with radius R=6cm and thickness dR = 4um (very thin layer). I am trying to imagine how it would be possible to subtract something from it (a mask) that would leave only 50 um holes in it. The other method Jon suggested (creating multiple sub-volumes and fill it up with vacuum) is also not trivial because given the dimension of my G4Tubs (R~6 cm, length ~ 60 cm, thickness 4 um) it would amount to creating a huge amount of very small sub-volumes, because the holes would have diameter of r = 25 um (but of course the same 'thickness' of 4 um). Do you think it is realistic? Thanks for help, Balint On Dec 5, 2012, at 6:42 PM, John Apostolakis <John.Apostolakis@cern.ch> wrote: > > *** Discussion title: Geometry > > Dear Balint, > > The most performant method for creating multiple holes in one volume is to create sub-volumes. You will have to fill them up with the material of the surroundings (or thin vacuum if relevant). > > If you use this method, you can create as many sub-volumes as you like (within the memory of your machine) - the G4 geometry modeler will handle the navigation efficiently by creating an optimization grid ('smart voxels'). > > If your holes could go between different tubes, then there are two alternatives: > > 1) Manually place the hole volumes: > - locate yourself which volumes a hole is in ( it should be easy if your geometry is regular - and potentially you could get some help from the Navigator if not) > - if one hole H_k spans two or more tubes, then for each tube T_i in which it must appear, create a new volume S_i which is the intersection of T_i and the Hole H_k and subtract that (intersection) volume from the tube T_i; > > 2) Use the new capability of Geant4 9.5 (and 9.6) that allows you to create a "Layered Mass Geometry". This allow you to superimpose new elements of a geometry (the holes) in the existing complicated geometry (the layers made of thin tubes) > > Please search the documentation for information how to register a parallel geometry for this option. > > I expect that these two options should be roughly competitive in simulation time, but the first option is the best tested one. If you gain experience using the LMG and have feedback, we will be pleased to hear from you. > > Best regards, > John > > On Dec 5, 2012, at 3:32 PM, Balint Radics wrote: > >> *** Discussion title: Geometry >> >> Hello, >> >> I have some layers of G4Tubs tube thin objects. I would like to make small holes in it (e.g. 50 um size holes with 50 um distance from each other). Would you please give an example how to do that? >> >> Thanks a lot, >> Balint > > ------------------------------------------------------------- > Visit this GEANT4 at hypernews.slac.stanford.edu message (to reply or unsubscribe) at: > http://hypernews.slac.stanford.edu/HyperNews/geant4/get/geometry/1246/2.html
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