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This commit is contained in:
Gabriele Cosmo
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// This code implementation is the intellectual property of
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// the RD44 GEANT4 collaboration.
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//
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// By copying, distributing or modifying the Program (or any work
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// based on the Program) you indicate your acceptance of this statement,
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// and all its terms.
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//
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// $Id: G4Cerenkov.cc,v 2.4 1998/08/25 22:06:03 gum Exp $
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// GEANT4 tag $Name: geant4-00 $
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//
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////////////////////////////////////////////////////////////////////////
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// Cerenkov Radiation Class Implementation
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////////////////////////////////////////////////////////////////////////
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//
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// File: G4Cerenkov.cc
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// Description: Continuous Process -- Generation of Cerenkov Photons
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// Version: 2.1
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// Created: 1996-02-21
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// Author: Juliet Armstrong
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// Updated: 1997-08-08 by Peter Gumplinger
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// > add protection against /0
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// > G4MaterialPropertiesTable; new physics/tracking scheme
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// mail: gum@triumf.ca
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//
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////////////////////////////////////////////////////////////////////////
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#include "G4ios.hh"
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#include "G4Cerenkov.hh"
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/////////////////////////
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// Class Implementation
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/////////////////////////
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//////////////
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// Operators
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//////////////
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// G4Cerenkov::operator=(const G4Cerenkov &right)
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// {
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// }
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/////////////////
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// Constructors
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/////////////////
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G4Cerenkov::G4Cerenkov(const G4String& processName)
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: G4VContinuousProcess(processName)
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{
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fTrackSecondariesFirst = false;
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fMaxPhotons = 0;
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thePhysicsTable = NULL;
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if (verboseLevel>0) {
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G4cout << GetProcessName() << " is created " << endl;
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}
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BuildThePhysicsTable();
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}
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// G4Cerenkov::G4Cerenkov(const G4Cerenkov &right)
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// {
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// }
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////////////////
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// Destructors
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////////////////
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G4Cerenkov::~G4Cerenkov()
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{
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if (thePhysicsTable!= NULL) {
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thePhysicsTable->clearAndDestroy();
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delete thePhysicsTable;
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}
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}
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////////////
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// Methods
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////////////
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// AlongStepDoIt
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// -------------
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//
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G4VParticleChange*
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G4Cerenkov::AlongStepDoIt(const G4Track& aTrack, const G4Step& aStep)
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// This routine is called for each tracking Step of a charged particle
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// in a radiator. A Poisson-distributed number of photons is generated
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// according to the Cerenkov formula, distributed evenly along the track
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// segment and uniformly azimuth w.r.t. the particle direction. The
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// parameters are then transformed into the Master Reference System, and
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// they are added to the particle change.
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{
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//////////////////////////////////////////////////////
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// Should we ensure that the material is dispersive?
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//////////////////////////////////////////////////////
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aParticleChange.Initialize(aTrack);
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const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle();
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const G4Material* aMaterial = aTrack.GetMaterial();
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G4StepPoint* pPreStepPoint = aStep.GetPreStepPoint();
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G4StepPoint* pPostStepPoint = aStep.GetPostStepPoint();
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G4ThreeVector x0 = pPreStepPoint->GetPosition();
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G4ThreeVector p0 = pPreStepPoint->GetMomentumDirection();
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G4double t0 = pPreStepPoint->GetGlobalTime();
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G4MaterialPropertiesTable* aMaterialPropertiesTable =
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aMaterial->GetMaterialPropertiesTable();
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if (!aMaterialPropertiesTable)
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return G4VContinuousProcess::AlongStepDoIt(aTrack, aStep);
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const G4MaterialPropertyVector* Rindex =
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aMaterialPropertiesTable->GetProperty("RINDEX");
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if (!Rindex)
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return G4VContinuousProcess::AlongStepDoIt(aTrack, aStep);
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G4double MeanNumPhotons =
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GetAverageNumberOfPhotons(aParticle,aMaterial,Rindex);
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G4double step_length;
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step_length = aStep.GetStepLength();
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if(step_length == 0.0)step_length = aStep.GetStepLength();
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MeanNumPhotons = MeanNumPhotons * step_length;
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// RandPoisson is a utility class. It provides functions
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// that act on HepRandom
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G4int NumPhotons = (G4int) RandPoisson::shoot(MeanNumPhotons);
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if (NumPhotons == 0) {
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// return unchanged particle and no secondaries
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aParticleChange.SetNumberOfSecondaries(0);
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return G4VContinuousProcess::AlongStepDoIt(aTrack, aStep);
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}
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////////////////////////////////////////////////////////////////
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aParticleChange.SetNumberOfSecondaries(NumPhotons);
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if (fTrackSecondariesFirst)
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aParticleChange.SetStatusChange(fSuspend);
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////////////////////////////////////////////////////////////////
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G4double Pmin = Rindex->GetMinPhotonMomentum();
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G4double Pmax = Rindex->GetMaxPhotonMomentum();
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G4double dp = Pmax - Pmin;
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G4double nMax = Rindex->GetMaxProperty();
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G4double BetaInverse = aParticle->GetTotalEnergy() /
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aParticle->GetTotalMomentum();
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G4double maxCos = BetaInverse / nMax;
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G4double maxSin2 = (1.0 - maxCos) * (1.0 + maxCos);
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for (G4int i = 0; i < NumPhotons; i++) {
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// Determine photon momentum
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G4double rand;
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G4double sampledMomentum, sampledRI;
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G4double cosTheta, sin2Theta;
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// sample a momentum
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do {
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rand = G4UniformRand();
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sampledMomentum = Pmin + rand * dp;
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sampledRI = Rindex->GetProperty(sampledMomentum);
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cosTheta = BetaInverse / sampledRI;
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sin2Theta = (1.0 - cosTheta)*(1.0 + cosTheta);
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rand = G4UniformRand();
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} while (rand*maxSin2 > sin2Theta);
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// Generate random position of photon on cone surface
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// defined by Theta
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rand = G4UniformRand();
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G4double phi = 2*M_PI*rand;
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G4double sinPhi = sin(phi);
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G4double cosPhi = cos(phi);
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// calculate x,y, and z components of photon momentum
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// (in coord system with primary particle direction
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// aligned with the z axis)
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G4double sinTheta = sqrt(sin2Theta);
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G4double px = sinTheta*cosPhi;
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G4double py = sinTheta*sinPhi;
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G4double pz = cosTheta;
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// Create photon momentum direction vector
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// The momentum direction is still with respect
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// to the coordinate system where the primary
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// particle direction is aligned with the z axis
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G4ParticleMomentum photonMomentum(px, py, pz);
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// Rotate momentum direction back to global reference
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// system
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photonMomentum.rotateUz(p0);
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// Determine polarization of new photon
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G4double sx = cosTheta*cosPhi;
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G4double sy = cosTheta*sinPhi;
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G4double sz = -sinTheta;
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G4ThreeVector photonPolarization(sx, sy, sz);
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// Rotate back to original coord system
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photonPolarization.rotateUz(p0);
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// Generate a new photon:
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G4DynamicParticle* aCerenkovPhoton =
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new G4DynamicParticle(G4OpticalPhoton::OpticalPhoton(),
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photonMomentum);
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aCerenkovPhoton->SetPolarization
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(photonPolarization.x(),
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photonPolarization.y(),
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photonPolarization.z());
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aCerenkovPhoton->SetKineticEnergy(sampledMomentum);
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// Generate new G4Track object:
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rand = G4UniformRand();
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G4double delta = rand * aStep.GetStepLength();
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G4ThreeVector aSecondaryPosition = x0 + delta * p0;
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G4double deltaTime = delta /
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((pPreStepPoint->GetVelocity()+
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pPostStepPoint->GetVelocity())/2.);
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G4double aSecondaryTime = t0 + deltaTime;
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G4Track* aSecondaryTrack =
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new G4Track(aCerenkovPhoton,aSecondaryTime,aSecondaryPosition);
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aSecondaryTrack->SetTouchable(pPreStepPoint->
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GetTouchable());
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aSecondaryTrack->SetParentID(aTrack.GetTrackID());
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aParticleChange.AddSecondary(aSecondaryTrack);
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}
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if (verboseLevel>0) {
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G4cout << "\n Exiting from G4Cerenkov::DoIt -- NumberOfSecondaries = "
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<< aParticleChange.GetNumberOfSecondaries() << endl;
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}
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return G4VContinuousProcess::AlongStepDoIt(aTrack, aStep);
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}
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// BuildThePhysicsTable for the Cerenkov process
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// ---------------------------------------------
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//
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void G4Cerenkov::BuildThePhysicsTable()
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{
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if (thePhysicsTable) return;
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const G4MaterialTable* theMaterialTable=
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G4Material::GetMaterialTable();
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G4int numOfMaterials = theMaterialTable->length();
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// create new physics table
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thePhysicsTable = new G4PhysicsTable(numOfMaterials);
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// loop for materials
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for (G4int i=0 ; i < numOfMaterials; i++)
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{
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G4PhysicsOrderedFreeVector* aPhysicsOrderedFreeVector =
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new G4PhysicsOrderedFreeVector();
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// Retrieve vector of refraction indices for the material
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// from the material's optical properties table
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G4Material* aMaterial = (*theMaterialTable)(i);
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G4MaterialPropertiesTable* aMaterialPropertiesTable =
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aMaterial->GetMaterialPropertiesTable();
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if (aMaterialPropertiesTable) {
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G4MaterialPropertyVector* theRefractionIndexVector =
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aMaterialPropertiesTable->GetProperty("RINDEX");
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if (theRefractionIndexVector) {
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// Retrieve the first refraction index in vector
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// of (photon momentum, refraction index) pairs
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theRefractionIndexVector->ResetIterator();
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++(*theRefractionIndexVector); // advance to 1st entry
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G4double currentRI = theRefractionIndexVector->
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GetProperty();
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if (currentRI > 1.0) {
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// Create first (photon momentum, Cerenkov Integral)
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// pair
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G4double currentPM = theRefractionIndexVector->
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GetPhotonMomentum();
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G4double currentCAI = 0.0;
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aPhysicsOrderedFreeVector->
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InsertValues(currentPM , currentCAI);
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// Set previous values to current ones prior to loop
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G4double prevPM = currentPM;
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G4double prevCAI = currentCAI;
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G4double prevRI = currentRI;
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// loop over all (photon momentum, refraction index)
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// pairs stored for this material
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while(++(*theRefractionIndexVector))
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{
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currentRI=theRefractionIndexVector->
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GetProperty();
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currentPM = theRefractionIndexVector->
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GetPhotonMomentum();
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currentCAI = 0.5*(1.0/(prevRI*prevRI) +
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1.0/(currentRI*currentRI));
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currentCAI = prevCAI +
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(currentPM - prevPM) * currentCAI;
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aPhysicsOrderedFreeVector->
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InsertValues(currentPM, currentCAI);
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prevPM = currentPM;
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prevCAI = currentCAI;
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prevRI = currentRI;
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}
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}
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}
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}
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// The Cerenkov integral for a given material
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// will be inserted in thePhysicsTable
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// according to the position of the material in
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// the material table.
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thePhysicsTable->insertAt(i,aPhysicsOrderedFreeVector);
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}
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}
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// GetContinuousStepLimit
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// ----------------------
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//
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G4double
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G4Cerenkov::GetContinuousStepLimit(const G4Track& aTrack,
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G4double ,
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G4double ,
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G4double& )
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{
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// If user has defined an average maximum number of photons to
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// be generated in a Step, then return the Step length for that
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// number of photons.
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if (fMaxPhotons == 0) return DBL_MAX;
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const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle();
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const G4Material* aMaterial = aTrack.GetMaterial();
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G4MaterialPropertiesTable* aMaterialPropertiesTable =
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aMaterial->GetMaterialPropertiesTable();
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if (!aMaterialPropertiesTable) return DBL_MAX;
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const G4MaterialPropertyVector* Rindex =
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aMaterialPropertiesTable->GetProperty("RINDEX");
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if (!Rindex) return DBL_MAX;
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G4double MeanNumPhotons =
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GetAverageNumberOfPhotons(aParticle,aMaterial,Rindex);
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if(MeanNumPhotons == 0.0) return DBL_MAX;
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G4double StepLimit = fMaxPhotons / MeanNumPhotons;
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return StepLimit;
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}
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// GetAverageNumberOfPhotons
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// -------------------------
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// This routine computes the number of Cerenkov photons produced per
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// GEANT-unit (millimeter) in the current medium.
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// ^^^^^^^^^^
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G4double
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G4Cerenkov::GetAverageNumberOfPhotons(const G4DynamicParticle* aParticle,
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const G4Material* aMaterial,
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const G4MaterialPropertyVector* Rindex) const
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{
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const G4double Rfact = 369.81/(eV * cm);
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if(aParticle->GetTotalMomentum() == 0.0)return 0.0;
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G4double BetaInverse = aParticle->GetTotalEnergy() /
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aParticle->GetTotalMomentum();
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// Vectors used in computation of Cerenkov Angle Integral:
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// - Refraction Indices for the current material
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// - new G4PhysicsOrderedFreeVector allocated to hold CAI's
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G4int materialIndex = G4Material::GetMaterialTable()->index(aMaterial);
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// Retrieve the Cerenkov Angle Integrals for this material
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G4PhysicsOrderedFreeVector* CerenkovAngleIntegrals =
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(G4PhysicsOrderedFreeVector*)((*thePhysicsTable)(materialIndex));
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// Min and Max photon momenta
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G4double Pmin = Rindex->GetMinPhotonMomentum();
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G4double Pmax = Rindex->GetMaxPhotonMomentum();
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// Min and Max Refraction Indices
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G4double nMin = Rindex->GetMinProperty();
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G4double nMax = Rindex->GetMaxProperty();
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// Max Cerenkov Angle Integral
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G4double CAImax = CerenkovAngleIntegrals->GetMaxValue();
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G4double dp, ge;
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// If n(Pmax) < 1/Beta -- no photons generated
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if (nMax < BetaInverse) {
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dp = 0;
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ge = 0;
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}
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// otherwise if n(Pmin) >= 1/Beta -- photons generated
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else if (nMin > BetaInverse) {
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dp = Pmax - Pmin;
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ge = CAImax;
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}
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// If n(Pmin) < 1/Beta, and n(Pmax) >= 1/Beta, then
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// we need to find a P such that the value of n(P) == 1/Beta.
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// Interpolation is performed by the GetPhotonMomentum() and
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// GetProperty() methods of the G4MaterialPropertiesTable and
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// the GetValue() method of G4PhysicsVector.
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else {
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Pmin = Rindex->GetPhotonMomentum(BetaInverse);
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dp = Pmax - Pmin;
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// need boolean for current implementation of G4PhysicsVector
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// ==> being phased out
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G4bool isOutRange;
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G4double CAImin = CerenkovAngleIntegrals->
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GetValue(Pmin, isOutRange);
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ge = CAImax - CAImin;
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if (verboseLevel>0) {
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G4cout << "CAImin = " << CAImin << endl;
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G4cout << "ge = " << ge << endl;
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}
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}
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// particle charge
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G4double charge = aParticle->GetDefinition()->GetPDGCharge();
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// Calculate number of photons
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G4double NumPhotons =
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Rfact * charge*charge * (dp - ge * BetaInverse*BetaInverse);
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return NumPhotons / cm;
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}
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