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/// @file MedicalBeam.cc
/// @brief Define beam profile as primary generator

#include "MedicalBeam.hh"

#include "G4Event.hh"
#include "G4ParticleTable.hh"
#include "G4PrimaryVertex.hh"
#include "Randomize.hh"

#include <cmath>

using namespace CLHEP;

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
MedicalBeam::MedicalBeam()
  : fparticle(0),
    fkineticE(1. * MeV),
    fsourcePosition(G4ThreeVector()),
    fSSD(1. * m),
    ffieldShape(MedicalBeam::kSQUARE),
    ffieldR(10. * cm)
{
  G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
  fparticle = particleTable->FindParticle("proton");

  fkineticE = 200. * MeV;
  fsourcePosition = G4ThreeVector(0., 0., -125. * cm);
  fSSD = 100. * cm;
  ffieldXY[0] = ffieldXY[1] = 5. * cm;
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
MedicalBeam::~MedicalBeam() {}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
G4ThreeVector MedicalBeam::GenerateBeamDirection() const
{
  // uniform distribution in a limitted solid angle
  G4double dr;
  if (ffieldShape == MedicalBeam::kSQUARE) {
    dr = std::sqrt(sqr(ffieldXY[0] / 2.) + sqr(ffieldXY[1] / 2.));
  }
  else {
    dr = ffieldR;
  }

  G4double sin0 = dr / fSSD;
  G4double cos0 = std::sqrt(1. - sqr(sin0));

  G4double dcos = 0.;
  G4double dsin, dphi, z;

  G4double x = DBL_MAX;
  G4double y = DBL_MAX;

  G4double xmax, ymax;
  if (ffieldShape == MedicalBeam::kSQUARE) {
    xmax = ffieldXY[0] / 2. / fSSD;
    ymax = ffieldXY[1] / 2. / fSSD;
  }
  else {
    xmax = ymax = DBL_MAX - 1.;
  }

  while (!(std::abs(x) < xmax && std::abs(y) < ymax)) {
    dcos = G4RandFlat::shoot(cos0, 1.);
    dsin = std::sqrt(1. - sqr(dcos));
    dphi = G4RandFlat::shoot(0., twopi);

    x = std::cos(dphi) * dsin * dcos;
    y = std::sin(dphi) * dsin * dcos;
  }
  z = dcos;

  return G4ThreeVector(x, y, z);
}

//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
void MedicalBeam::GeneratePrimaries(G4Event* anEvent)
{
  if (fparticle == NULL) return;

  // create a new vertex
  G4PrimaryVertex* vertex = new G4PrimaryVertex(fsourcePosition, 0. * ns);

  // momentum
  G4double mass = fparticle->GetPDGMass();
  G4double p = std::sqrt(sqr(mass + fkineticE) - sqr(mass));
  G4ThreeVector pmon = p * GenerateBeamDirection();
  G4PrimaryParticle* primary = new G4PrimaryParticle(fparticle, pmon.x(), pmon.y(), pmon.z());

  // set primary to vertex
  vertex->SetPrimary(primary);

  // set vertex to event
  anEvent->AddPrimaryVertex(vertex);
}