G4INCLReflectionChannel.cc

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//
// INCL++ intra-nuclear cascade model
// Pekka Kaitaniemi, CEA and Helsinki Institute of Physics
// Davide Mancusi, CEA
// Alain Boudard, CEA
// Sylvie Leray, CEA
// Joseph Cugnon, University of Liege
//
#define INCLXX_IN_GEANT4_MODE 1

#include "globals.hh"

#include "G4INCLReflectionChannel.hh"
#include "G4INCLFinalState.hh"
#include "G4INCLRandom.hh"
#include "G4INCLINuclearPotential.hh"

#include <cmath>

namespace G4INCL {
  const G4double ReflectionChannel::sinMinReflectionAngleSquaredOverFour = std::pow(std::sin(2.*Math::pi/200.),2.);
  const G4double ReflectionChannel::positionScalingFactor = 0.99;

  ReflectionChannel::ReflectionChannel(Nucleus *n, Particle *p)
    :theNucleus(n),theParticle(p)
  {
  }

  ReflectionChannel::~ReflectionChannel()
  {
  }

  FinalState* ReflectionChannel::getFinalState()
  {
    FinalState *fs = new FinalState(); // Create final state for the output
    fs->setTotalEnergyBeforeInteraction(theParticle->getEnergy() - theParticle->getPotentialEnergy());

    const ThreeVector &oldMomentum = theParticle->getMomentum();
    G4double pspr = theParticle->getPosition().dot(oldMomentum);
    if(pspr>=0) { // This means that the particle is trying to leave; perform a reflection
      const G4double x2cour = theParticle->getPosition().mag2();
      const ThreeVector newMomentum = oldMomentum - (theParticle->getPosition() * (2.0 * pspr/x2cour));
      const G4double deltaP2 = (newMomentum-oldMomentum).mag2();
      theParticle->setMomentum(newMomentum);
      const G4double minDeltaP2 = sinMinReflectionAngleSquaredOverFour * newMomentum.mag2();
      if(deltaP2 < minDeltaP2) { // Avoid extremely small reflection angles
        theParticle->setPosition(theParticle->getPosition() * positionScalingFactor);
        INCL_DEBUG("Reflection angle for particle " << theParticle->getID() << " was too tangential: " << std::endl
            << "  " << deltaP2 << "=deltaP2<minDeltaP2=" << minDeltaP2 << std::endl
            << "  Resetting the particle position to ("
            << theParticle->getPosition().getX() << ", "
            << theParticle->getPosition().getY() << ", "
            << theParticle->getPosition().getZ() << ")" << std::endl);
      }
      theNucleus->updatePotentialEnergy(theParticle);
    } else { // The particle momentum is already directed towards the inside of the nucleus; do nothing
      // ...but make sure this only happened because of the frozen propagation
// assert(theParticle->getPosition().dot(theParticle->getPropagationVelocity())>0.);
    }

    theParticle->thawPropagation();
    fs->addModifiedParticle(theParticle);
    return fs;
  }
}