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Question Emission from isotropic point source that exits a rectangular window 

Forum: Particles
Date: 19 Aug, 2009
From: Ioannis Sechopoulos <Ioannis Sechopoulos>

Hello, I need to simulate photons that are emitted from an isotropic point source, but I only need to simulate the ones that are emitted in a direction so that they travel through a rectangular window. I know that GPS has an isotropic angular distribution and that you can limit the angles, but that would give me the equivalent of the exit window being a portion of a sphere centered on the source, not of a flat exit window. Also, I've seen the C++ version of having an isotropic source:

  G4double cosTheta = 2*G4UniformRand() - 1., phi = twopi*G4UniformRand();
  G4double sinTheta = std::sqrt(1. - cosTheta*cosTheta);
  G4double ux = sinTheta*std::cos(phi),
           uy = sinTheta*std::sin(phi),
           uz = cosTheta;
  particleGun->SetParticleMomentumDirection(G4ThreeVector(ux,uy,uz));

and I understand I could limit cosTheta and phi to a specific range of values, but again I would get whatever exits a portion of the sphere. Does anybody know how I can limit the isotropic source photons to those that cover a certain delta X and delta Y at a certain R distance from the source? I don't mind having to code it in the PrimaryGeneratorAction and not using GPS, I'm actually more used to the former.

Thanks!

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1 Feedback: Re: Emission from isotropic point source that exits a rectangular window   (Gumplinger Peter - 20 Aug, 2009)
(_ Agree: Re: Emission from isotropic point source that exits a rectangular window   (Ioannis Sechopoulos - 21 Aug, 2009)
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