exMPI04/src/MedicalBeam.cc

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0026 //
0027 /// @file MedicalBeam.cc
0028 /// @brief Define beam profile as primary generator
0029
0030 #include "MedicalBeam.hh"
0031
0032 #include "G4Event.hh"
0033 #include "G4ParticleTable.hh"
0034 #include "G4PrimaryVertex.hh"
0035 #include "Randomize.hh"
0036
0037 #include <cmath>
0038
0039 using namespace CLHEP;
0040
0041 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0042 MedicalBeam::MedicalBeam()
0043   : fparticle(0),
0044     fkineticE(1. * MeV),
0045     fsourcePosition(G4ThreeVector()),
0046     fSSD(1. * m),
0047     ffieldShape(MedicalBeam::kSQUARE),
0048     ffieldR(10. * cm)
0049 {
0050   G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
0051   fparticle = particleTable->FindParticle("proton");
0052
0053   fkineticE = 200. * MeV;
0054   fsourcePosition = G4ThreeVector(0., 0., -125. * cm);
0055   fSSD = 100. * cm;
0056   ffieldXY[0] = ffieldXY[1] = 5. * cm;
0057 }
0058
0059 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0060 MedicalBeam::~MedicalBeam() {}
0061
0062 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0063 G4ThreeVector MedicalBeam::GenerateBeamDirection() const
0064 {
0065   // uniform distribution in a limitted solid angle
0066   G4double dr;
0067   if (ffieldShape == MedicalBeam::kSQUARE) {
0068     dr = std::sqrt(sqr(ffieldXY[0] / 2.) + sqr(ffieldXY[1] / 2.));
0069   }
0070   else {
0071     dr = ffieldR;
0072   }
0073
0074   G4double sin0 = dr / fSSD;
0075   G4double cos0 = std::sqrt(1. - sqr(sin0));
0076
0077   G4double dcos = 0.;
0078   G4double dsin, dphi, z;
0079
0080   G4double x = DBL_MAX;
0081   G4double y = DBL_MAX;
0082
0083   G4double xmax, ymax;
0084   if (ffieldShape == MedicalBeam::kSQUARE) {
0085     xmax = ffieldXY[0] / 2. / fSSD;
0086     ymax = ffieldXY[1] / 2. / fSSD;
0087   }
0088   else {
0089     xmax = ymax = DBL_MAX - 1.;
0090   }
0091
0092   while (!(std::abs(x) < xmax && std::abs(y) < ymax)) {
0093     dcos = G4RandFlat::shoot(cos0, 1.);
0094     dsin = std::sqrt(1. - sqr(dcos));
0095     dphi = G4RandFlat::shoot(0., twopi);
0096
0097     x = std::cos(dphi) * dsin * dcos;
0098     y = std::sin(dphi) * dsin * dcos;
0099   }
0100   z = dcos;
0101
0102   return G4ThreeVector(x, y, z);
0103 }
0104
0105 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0106 void MedicalBeam::GeneratePrimaries(G4Event* anEvent)
0107 {
0108   if (fparticle == NULL) return;
0109
0110   // create a new vertex
0111   G4PrimaryVertex* vertex = new G4PrimaryVertex(fsourcePosition, 0. * ns);
0112
0113   // momentum
0114   G4double mass = fparticle->GetPDGMass();
0115   G4double p = std::sqrt(sqr(mass + fkineticE) - sqr(mass));
0116   G4ThreeVector pmon = p * GenerateBeamDirection();
0117   G4PrimaryParticle* primary = new G4PrimaryParticle(fparticle, pmon.x(), pmon.y(), pmon.z());
0118
0119   // set primary to vertex
0120   vertex->SetPrimary(primary);
0121
0122   // set vertex to event
0123   anEvent->AddPrimaryVertex(vertex);
0124 }