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## Re: Simulating and calculating Geometric Factors in GEANT4

Forum: Space Applications
Re: Simulating and calculating Geometric Factors in GEANT4 (Bruno Morgado)
Date: 02 Oct, 2012
From: Laurent Desorgher <Laurent Desorgher>

 Dear Bruno, I think that your normalization formula is wrong. What puzzled me is the 8 and pi^2 factors. Indeed if you define the geometrical factor as the factor by which the omnidirectional isotropic flux ( flux and not current!) should be multiplied to get your normalized counts then your normalized signal SN should be SN=(Source_surface/4.)*nb_detected_particles/nb_generated_particles =pi*R^2*nb_detected_particles/nb_generated_particles It is always usefull to make a normalization test with geantino where you do register the n.b. of geantino entering your sensitive detector. Your normalized signal or geometric factor should be the external surface of your sensitive detector divided by 4. Best Regards Laurent On Tue, 26 Jun 2012 11:53:20 GMT, Bruno Morgado wrote: ```> Hello, > I'm trying to calculate the "real" Geometric Factor (GF) of an instrument in Geant, but I'm having some problems with the results. > > My macro file is: > # Set GPS spherical source > /gps/particle e- # particle type > /gps/pos/type Surface > /gps/pos/shape Sphere > /gps/centre 0 0 0 m # source centre > /gps/pos/radius 10 cm > /gps/ang/type cos > /gps/ene/mono 52. keV > /run/beamOn 200000000 > > And I finish calculating the GF with: > double geometryFactor(double numberDetectedParticles, double numberEmitedParticles, const double sourceRadius) { > return ((8 * numberDetectedParticles * pow(TMath::Pi(), 2) * pow(sourceRadius, 2)) / numberEmitedParticles); > } > > Still, like I said the results don't seem to add up. Can you direct me to some place where I can check if these are the correct calculations or if there is some mistake? > ```

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1 Re: Simulating and calculating Geometric Factors in GEANT4   (Bruno Morgado - 08 Oct, 2012)
Re: Simulating and calculating Geometric Factors in GEANT4   (Laurent Desorgher - 08 Oct, 2012)
 to: "Re: Simulating and calculating Geometric Factors in GEANT4"
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