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PrimaryGeneratorAction0.cc
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33 
34 #include "PrimaryGeneratorAction0.hh"
35 #include "PrimaryGeneratorAction.hh"
36 
37 #include "G4Event.hh"
38 #include "G4ParticleGun.hh"
39 #include "G4SystemOfUnits.hh"
40 #include "Randomize.hh"
41 
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44 PrimaryGeneratorAction0::PrimaryGeneratorAction0(G4ParticleGun* gun)
45 : fParticleGun(gun)
46 {
47  //solid angle
48  //
49  G4double alphaMin = 0*deg; //alpha in [0,pi]
50  G4double alphaMax = 60*deg;
51  fCosAlphaMin = std::cos(alphaMin);
52  fCosAlphaMax = std::cos(alphaMax);
53 
54  fPsiMin = 0*deg; //psi in [0, 2*pi]
55  fPsiMax = 360*deg;
56 }
57 
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60 PrimaryGeneratorAction0::~PrimaryGeneratorAction0()
61 { }
62 
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64 
65 void PrimaryGeneratorAction0::GeneratePrimaries(G4Event* anEvent)
66 {
67  //vertex position fixed
68  //
69  G4double x0 = 0*mm, y0 = 0*mm, z0 = 0*mm;
70  fParticleGun->SetParticlePosition(G4ThreeVector(x0,y0,z0));
71 
72  //direction uniform in solid angle
73  //
74  G4double cosAlpha = fCosAlphaMin-G4UniformRand()*(fCosAlphaMin-fCosAlphaMax);
75  G4double sinAlpha = std::sqrt(1. - cosAlpha*cosAlpha);
76  G4double psi = fPsiMin + G4UniformRand()*(fPsiMax - fPsiMin);
77 
78  G4double ux = sinAlpha*std::cos(psi),
79  uy = sinAlpha*std::sin(psi),
80  uz = cosAlpha;
81 
82  fParticleGun->SetParticleMomentumDirection(G4ThreeVector(ux,uy,uz));
83 
84  fParticleGun->GeneratePrimaryVertex(anEvent);
85 }
86 
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