JMARKOV::JMarkovPhotonTracker Class Reference

The JMarkovPhotonTracker generates ensembles of photon paths by tracking photons from a source to a target. More...

#include <JMarkovPhotonTracker.hh>

Public Member Functions
	JMarkovPhotonTracker ()
	standard constructor More...
std::vector< JPhotonPath >	trackPhotons (unsigned long int n, JSourceModel *src, JScatteringModel *sm, JTargetModel *trg, double lambda_abs)
	Track n photons. More...

Detailed Description

The JMarkovPhotonTracker generates ensembles of photon paths by tracking photons from a source to a target.

The target is modelled as a sphere with finite radius r.

Random numbers are drawn from gRandom.

Definition at line 35 of file JMarkovPhotonTracker.hh.

Constructor & Destructor Documentation

JMARKOV::JMarkovPhotonTracker::JMarkovPhotonTracker ( )

inline

standard constructor

Definition at line 39 of file JMarkovPhotonTracker.hh.

{}

Member Function Documentation

std::vector< JPhotonPath > JMARKOV::JMarkovPhotonTracker::trackPhotons	(	unsigned long int	n,
		JSourceModel *	src,
		JScatteringModel *	sm,
		JTargetModel *	trg,
		double	lambda_abs
	)

Track n photons.

The tracks of all photons that hit the target are returned.

Definition at line 50 of file JMarkovPhotonTracker.hh.

                                                                                                                                                                {
    const double lambda_scat = sm->getScatteringLength() ;
    std::vector<JPhotonPath> ensemble ;

    for( unsigned long int i=0 ; i<n ; ++i ) {
      // how long until the photon is absorbed
      double Lmax = gRandom->Exp(lambda_abs) ;
      // initial direction
      JVersor3D dir = src->generateDirection() ;

      // current length of the photon path
      double L = 0 ;
      // how often the photon has scattered so far
      int nscat = 0 ;

      // initialize path
      JPhotonPath p(0) ;
      p[0] = src->getPosition() ;
      p[1] = src->getPosition() ; // temporary placeholder

      while( true ) {
        // distance until next scattering (or absorption)
        double stepsize = gRandom->Exp( lambda_scat ) ;
        // whether this is going to be the last step
        bool isAbsorbed = false ;
        if( stepsize > Lmax-L ) {
          stepsize = Lmax-L ;
          isAbsorbed = true ;
        }

        // set new vertex position
        p[1+nscat] = p[nscat] + stepsize * JPosition3D(dir) ;

        // check whether the photon hits the target
        JPhotonPath lastvertex(0) ;
        lastvertex[0] = p[p.size()-2] ;
        lastvertex[1] = p[p.size()-1] ;
        if( lastvertex.hitsSphere(trg->getPosition(),trg->getRadius()) ) {
          const JPosition3D hit_position = lastvertex.getSphereHitPosition( trg->getPosition(), trg->getRadius() ) ;

          // correct the position of the final vertex
          p[p.size()-1] = hit_position  ;
          // weigh the photon path with the target efficiency
          p.weight = trg->getEfficiency( p[p.size()-1]-p[p.size()-2] ) ;
          // add to the ensemble
          ensemble.push_back(p) ;
          break ;
        }

        if( isAbsorbed ) break ;

        L += lastvertex.getLength() ;

        // scatter
        ++nscat ;
        JRotation3D rot(dir) ;
        dir = sm->generateDirection() ;
        dir = dir.rotate_back(rot) ;
        p.addVertex() ;
      }
    }

    return ensemble ;
  }

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The documentation for this class was generated from the following file:

• JMarkovPhotonTracker.hh