geant4/examples/advanced/gammaray_telescope/src/GammaRayTelPrimaryGeneratorAction.cc

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// $Id: GammaRayTelPrimaryGeneratorAction.cc,v 1.11 2007/11/09 16:33:34 flongo Exp $
// GEANT4 tag $Name: geant4-09-02 $
// ------------------------------------------------------------
//      GEANT 4 class implementation file
//      CERN Geneva Switzerland
//
//
//      ------------ GammaRayTelPrimaryGeneratorAction  ------
//           by  G.Santin, F.Longo & R.Giannitrapani (13 nov 2000)
//
// ************************************************************

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#include "G4RunManager.hh"
#include "GammaRayTelPrimaryGeneratorAction.hh"

#include "GammaRayTelDetectorConstruction.hh"
#include "GammaRayTelPrimaryGeneratorMessenger.hh"

#include "G4Event.hh"
#include "G4ParticleGun.hh"
#include "G4GeneralParticleSource.hh"
#include "G4ParticleTable.hh"
#include "G4ParticleDefinition.hh"
#include "Randomize.hh"

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GammaRayTelPrimaryGeneratorAction::GammaRayTelPrimaryGeneratorAction()
  :rndmFlag("off"),nSourceType(0),nSpectrumType(0)
{
  G4RunManager* runManager = G4RunManager::GetRunManager();
  GammaRayTelDetector =
    (GammaRayTelDetectorConstruction*)(runManager->GetUserDetectorConstruction());


  //create a messenger for this class
  
  gunMessenger = new GammaRayTelPrimaryGeneratorMessenger(this);

  G4int n_particle = 1;

  particleGun  = new G4ParticleGun(n_particle);     
      // default particle kinematic
  
  G4ParticleTable* particleTable = G4ParticleTable::GetParticleTable();
  G4String particleName;
  G4ParticleDefinition* particle
    = particleTable->FindParticle(particleName="e-");
  particleGun->SetParticleDefinition(particle);
  particleGun->SetParticleMomentumDirection(G4ThreeVector(0.,0.,-1.));
  particleGun->SetParticleEnergy(30.*MeV);
  G4double position = 0.5*(GammaRayTelDetector->GetWorldSizeZ());
  particleGun->SetParticlePosition(G4ThreeVector(0.*cm,0.*cm,position));
  particleSource = new G4GeneralParticleSource();
   
}

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GammaRayTelPrimaryGeneratorAction::~GammaRayTelPrimaryGeneratorAction()
{
  if (sourceGun)
    delete particleGun;
  else
    delete particleSource;

  delete gunMessenger;
}

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void GammaRayTelPrimaryGeneratorAction::GeneratePrimaries(G4Event* anEvent)
{
   if (sourceGun)
    {

      //this function is called at the begining of event
      // 
      G4double z0 = 0.5*(GammaRayTelDetector->GetWorldSizeZ());
      G4double x0 = 0.*cm, y0 = 0.*cm;
  
      G4ThreeVector pos0;
      G4ThreeVector dir0;
      G4ThreeVector vertex0 = G4ThreeVector(x0,y0,z0);
      
      dir0 = G4ThreeVector(0.,0.,-1.);
      
      G4double theta, phi, y, f;
      G4double theta0=0.;
      G4double phi0=0.;
      
      switch(nSourceType) {
      case 0:
	particleGun->SetParticlePosition(vertex0);
	particleGun->SetParticleMomentumDirection(dir0);
	break;
      case 1:
	// GS: Generate random position on the 4PIsphere to create a unif. distrib.
	// GS: on the sphere
	phi = G4UniformRand() * twopi;
	do {
	  y = G4UniformRand()*1.0;
	  theta = G4UniformRand() * pi;
	  f = std::sin(theta);
	} while (y > f);
	vertex0 = G4ThreeVector(1.,0.,0.);
	vertex0.setMag(dVertexRadius);
	vertex0.setTheta(theta);
	vertex0.setPhi(phi);
	particleGun->SetParticlePosition(vertex0);
	
	dir0 = G4ThreeVector(1.,0.,0.);
	do {
	  phi = G4UniformRand() * twopi;
	  do {
	    y = G4UniformRand()*1.0;
	    theta = G4UniformRand() * pi;
	    f = std::sin(theta);
	  } while (y > f);
	  dir0.setPhi(phi);
	  dir0.setTheta(theta);
	} while (vertex0.dot(dir0) >= -0.7 * vertex0.mag());
	particleGun->SetParticleMomentumDirection((G4ParticleMomentum)dir0);
	
	break;
      case 2:
	// GS: Generate random position on the upper semi-sphere z>0 to create a unif. distrib.
	// GS: on a plane
	phi = G4UniformRand() * twopi;
	do {
	  y = G4UniformRand()*1.0;
	  theta = G4UniformRand() * halfpi;
	  f = std::sin(theta) * std::cos(theta);
	} while (y > f);
	vertex0 = G4ThreeVector(1.,0.,0.);
	
	G4double xy = GammaRayTelDetector->GetWorldSizeXY();
	G4double z = GammaRayTelDetector->GetWorldSizeZ();
	
	if (dVertexRadius > xy*0.5)
	  { 
	    G4cout << "vertexRadius too big " << G4endl;
	    G4cout << "vertexRadius setted to " << xy*0.45 << G4endl;
	    dVertexRadius = xy*0.45;
	  }
	
	if (dVertexRadius > z*0.5)
	  { 
	    G4cout << "vertexRadius too high " << G4endl;
	    G4cout << "vertexRadius setted to " << z*0.45 << G4endl;
	    dVertexRadius = z*0.45;
	  }
	
	
	vertex0.setMag(dVertexRadius);
	vertex0.setTheta(theta);
	vertex0.setPhi(phi);
	
	// GS: Get the user defined direction for the primaries and
	// GS: Rotate the random position according to the user defined direction for the particle
	
	dir0 = particleGun->GetParticleMomentumDirection();
	if (dir0.mag() > 0.001) 
	  {
	    theta0 = dir0.theta();
	    phi0   = dir0.phi();   
	  }
	
	if (theta0!=0.) 
	  {
	    G4ThreeVector rotationAxis(1.,0.,0.);
	    rotationAxis.setPhi(phi0+halfpi);
	    vertex0.rotate(theta0+pi,rotationAxis);
	  }
	particleGun->SetParticlePosition(vertex0);
	break;
      }
      
      
      G4double pEnergy;
      
      switch(nSpectrumType) {
      case 0:
	break;
      case 1:
	break;
      case 2:
	do {
	  y = G4UniformRand()*100000.0;
	  pEnergy = G4UniformRand() * 10. * GeV;
	  f = std::pow(pEnergy * (1/GeV), -4.);
	} while (y > f);
	
	particleGun->SetParticleEnergy(pEnergy);
	
	break;
      case 3:
	break;
      }
      
      particleGun->GeneratePrimaryVertex(anEvent);
    }
   else
     {
       particleSource->GeneratePrimaryVertex(anEvent);
     }
   
}

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