Gabriele Cosmo
693 lines
22 KiB
C++
693 lines
22 KiB
C++
//
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// ********************************************************************
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// * License and Disclaimer *
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// * *
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// * The Geant4 software is copyright of the Copyright Holders of *
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// * the Geant4 Collaboration. It is provided under the terms and *
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// * conditions of the Geant4 Software License, included in the file *
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// * LICENSE and available at http://cern.ch/geant4/license . These *
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// * include a list of copyright holders. *
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// * *
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// * Neither the authors of this software system, nor their employing *
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// * institutes,nor the agencies providing financial support for this *
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// * work make any representation or warranty, express or implied, *
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// * regarding this software system or assume any liability for its *
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// * use. Please see the license in the file LICENSE and URL above *
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// * for the full disclaimer and the limitation of liability. *
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// * *
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// * This code implementation is the result of the scientific and *
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// * technical work of the GEANT4 collaboration. *
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// * By using, copying, modifying or distributing the software (or *
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// * any work based on the software) you agree to acknowledge its *
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// * use in resulting scientific publications, and indicate your *
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// * acceptance of all terms of the Geant4 Software license. *
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// ********************************************************************
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//
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//
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// $Id: G4Cerenkov.cc 85355 2014-10-28 09:58:59Z gcosmo $
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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: Discrete 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: 2007-09-30 by Peter Gumplinger
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// > change inheritance to G4VDiscreteProcess
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// GetContinuousStepLimit -> GetMeanFreePath (StronglyForced)
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// AlongStepDoIt -> PostStepDoIt
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// 2005-08-17 by Peter Gumplinger
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// > change variable name MeanNumPhotons -> MeanNumberOfPhotons
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// 2005-07-28 by Peter Gumplinger
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// > add G4ProcessType to constructor
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// 2001-09-17, migration of Materials to pure STL (mma)
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// 2000-11-12 by Peter Gumplinger
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// > add check on CerenkovAngleIntegrals->IsFilledVectorExist()
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// in method GetAverageNumberOfPhotons
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// > and a test for MeanNumberOfPhotons <= 0.0 in DoIt
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// 2000-09-18 by Peter Gumplinger
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// > change: aSecondaryPosition=x0+rand*aStep.GetDeltaPosition();
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// aSecondaryTrack->SetTouchable(0);
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// 1999-10-29 by Peter Gumplinger
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// > change: == into <= in GetContinuousStepLimit
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// 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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//
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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 "G4PhysicalConstants.hh"
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#include "G4SystemOfUnits.hh"
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#include "G4Poisson.hh"
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#include "G4EmProcessSubType.hh"
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#include "G4LossTableManager.hh"
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#include "G4MaterialCutsCouple.hh"
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#include "G4ParticleDefinition.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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// static data members
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//////////////////////
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//G4bool G4Cerenkov::fTrackSecondariesFirst = false;
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//G4double G4Cerenkov::fMaxBetaChange = 0.;
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//G4int G4Cerenkov::fMaxPhotons = 0;
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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, G4ProcessType type)
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: G4VProcess(processName, type) ,
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fTrackSecondariesFirst(false),
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fMaxBetaChange(0),
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fMaxPhotons(0)
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{
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SetProcessSubType(fCerenkov);
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thePhysicsTable = NULL;
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if (verboseLevel>0) {
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G4cout << GetProcessName() << " is created " << G4endl;
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}
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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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G4bool G4Cerenkov::IsApplicable(const G4ParticleDefinition& aParticleType)
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{
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G4bool result = false;
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if (aParticleType.GetPDGCharge() != 0.0 &&
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aParticleType.GetPDGMass() != 0.0 &&
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aParticleType.GetParticleName() != "chargedgeantino" &&
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!aParticleType.IsShortLived() ) { result = true; }
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return result;
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}
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void G4Cerenkov::SetTrackSecondariesFirst(const G4bool state)
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{
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fTrackSecondariesFirst = state;
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}
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void G4Cerenkov::SetMaxBetaChangePerStep(const G4double value)
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{
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fMaxBetaChange = value*CLHEP::perCent;
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}
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void G4Cerenkov::SetMaxNumPhotonsPerStep(const G4int NumPhotons)
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{
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fMaxPhotons = NumPhotons;
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}
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void G4Cerenkov::BuildPhysicsTable(const G4ParticleDefinition&)
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{
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if (!thePhysicsTable) BuildThePhysicsTable();
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}
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// PostStepDoIt
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// -------------
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//
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G4VParticleChange*
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G4Cerenkov::PostStepDoIt(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 = aStep.GetDeltaPosition().unit();
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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) return pParticleChange;
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G4MaterialPropertyVector* Rindex =
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aMaterialPropertiesTable->GetProperty("RINDEX");
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if (!Rindex) return pParticleChange;
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// particle charge
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const G4double charge = aParticle->GetDefinition()->GetPDGCharge();
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// particle beta
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const G4double beta = (pPreStepPoint ->GetBeta() +
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pPostStepPoint->GetBeta())/2.;
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G4double MeanNumberOfPhotons =
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GetAverageNumberOfPhotons(charge,beta,aMaterial,Rindex);
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if (MeanNumberOfPhotons <= 0.0) {
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// return unchanged particle and no secondaries
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aParticleChange.SetNumberOfSecondaries(0);
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return pParticleChange;
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}
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G4double step_length;
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step_length = aStep.GetStepLength();
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MeanNumberOfPhotons = MeanNumberOfPhotons * step_length;
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G4int NumPhotons = (G4int) G4Poisson(MeanNumberOfPhotons);
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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 pParticleChange;
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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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if (aTrack.GetTrackStatus() == fAlive )
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aParticleChange.ProposeTrackStatus(fSuspend);
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}
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////////////////////////////////////////////////////////////////
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G4double Pmin = Rindex->GetMinLowEdgeEnergy();
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G4double Pmax = Rindex->GetMaxLowEdgeEnergy();
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G4double dp = Pmax - Pmin;
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G4double nMax = Rindex->GetMaxValue();
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G4double BetaInverse = 1./beta;
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G4double maxCos = BetaInverse / nMax;
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G4double maxSin2 = (1.0 - maxCos) * (1.0 + maxCos);
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const G4double beta1 = pPreStepPoint ->GetBeta();
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const G4double beta2 = pPostStepPoint->GetBeta();
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G4double MeanNumberOfPhotons1 =
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GetAverageNumberOfPhotons(charge,beta1,aMaterial,Rindex);
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G4double MeanNumberOfPhotons2 =
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GetAverageNumberOfPhotons(charge,beta2,aMaterial,Rindex);
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for (G4int i = 0; i < NumPhotons; i++) {
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// Determine photon energy
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G4double rand;
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G4double sampledEnergy, sampledRI;
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G4double cosTheta, sin2Theta;
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// sample an energy
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do {
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rand = G4UniformRand();
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sampledEnergy = Pmin + rand * dp;
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sampledRI = Rindex->Value(sampledEnergy);
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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 = twopi*rand;
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G4double sinPhi = std::sin(phi);
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G4double cosPhi = std::cos(phi);
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// calculate x,y, and z components of photon energy
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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 = std::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(sampledEnergy);
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// Generate new G4Track object:
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G4double delta, NumberOfPhotons, N;
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do {
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rand = G4UniformRand();
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delta = rand * aStep.GetStepLength();
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NumberOfPhotons = MeanNumberOfPhotons1 - delta *
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(MeanNumberOfPhotons1-MeanNumberOfPhotons2)/
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aStep.GetStepLength();
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N = G4UniformRand() *
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std::max(MeanNumberOfPhotons1,MeanNumberOfPhotons2);
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} while (N > NumberOfPhotons);
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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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G4ThreeVector aSecondaryPosition =
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x0 + rand * aStep.GetDeltaPosition();
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G4Track* aSecondaryTrack =
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new G4Track(aCerenkovPhoton,aSecondaryTime,aSecondaryPosition);
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aSecondaryTrack->SetTouchableHandle(
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aStep.GetPreStepPoint()->GetTouchableHandle());
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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() << G4endl;
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}
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return pParticleChange;
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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 = G4Material::GetNumberOfMaterials();
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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 = 0;
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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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aPhysicsOrderedFreeVector = new G4PhysicsOrderedFreeVector();
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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 energy, refraction index) pairs
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G4double currentRI = (*theRefractionIndexVector)[0];
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if (currentRI > 1.0) {
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// Create first (photon energy, Cerenkov Integral)
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// pair
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G4double currentPM = theRefractionIndexVector->
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Energy(0);
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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 energy, refraction index)
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// pairs stored for this material
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for (size_t ii = 1;
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ii < theRefractionIndexVector->GetVectorLength();
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++ii)
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{
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currentRI = (*theRefractionIndexVector)[ii];
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currentPM = theRefractionIndexVector->Energy(ii);
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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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// GetMeanFreePath
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// ---------------
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//
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G4double G4Cerenkov::GetMeanFreePath(const G4Track&,
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G4double,
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G4ForceCondition*)
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{
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return 1.;
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}
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G4double G4Cerenkov::PostStepGetPhysicalInteractionLength(
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const G4Track& aTrack,
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G4double,
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G4ForceCondition* condition)
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{
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*condition = NotForced;
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G4double StepLimit = DBL_MAX;
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const G4Material* aMaterial = aTrack.GetMaterial();
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G4int materialIndex = aMaterial->GetIndex();
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// If Physics Vector is not defined no Cerenkov photons
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// this check avoid string comparison below
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if(!(*thePhysicsTable)[materialIndex]) { return StepLimit; }
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const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle();
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const G4MaterialCutsCouple* couple = aTrack.GetMaterialCutsCouple();
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G4double kineticEnergy = aParticle->GetKineticEnergy();
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const G4ParticleDefinition* particleType = aParticle->GetDefinition();
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G4double mass = particleType->GetPDGMass();
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// particle beta
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G4double beta = aParticle->GetTotalMomentum() /
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aParticle->GetTotalEnergy();
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// particle gamma
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G4double gamma = aParticle->GetTotalEnergy()/mass;
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G4MaterialPropertiesTable* aMaterialPropertiesTable =
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aMaterial->GetMaterialPropertiesTable();
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G4MaterialPropertyVector* Rindex = NULL;
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if (aMaterialPropertiesTable)
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Rindex = aMaterialPropertiesTable->GetProperty("RINDEX");
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G4double nMax;
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if (Rindex) {
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nMax = Rindex->GetMaxValue();
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} else {
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return StepLimit;
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}
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G4double BetaMin = 1./nMax;
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if ( BetaMin >= 1. ) return StepLimit;
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G4double GammaMin = 1./std::sqrt(1.-BetaMin*BetaMin);
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if (gamma < GammaMin ) return StepLimit;
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G4double kinEmin = mass*(GammaMin-1.);
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G4double RangeMin = G4LossTableManager::Instance()->
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GetRange(particleType,
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kinEmin,
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couple);
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G4double Range = G4LossTableManager::Instance()->
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GetRange(particleType,
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kineticEnergy,
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couple);
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G4double Step = Range - RangeMin;
|
|
if (Step < 1.*um ) return StepLimit;
|
|
|
|
if (Step > 0. && Step < StepLimit) StepLimit = Step;
|
|
|
|
// If user has defined an average maximum number of photons to
|
|
// be generated in a Step, then calculate the Step length for
|
|
// that number of photons.
|
|
|
|
if (fMaxPhotons > 0) {
|
|
|
|
// particle charge
|
|
const G4double charge = aParticle->
|
|
GetDefinition()->GetPDGCharge();
|
|
|
|
G4double MeanNumberOfPhotons =
|
|
GetAverageNumberOfPhotons(charge,beta,aMaterial,Rindex);
|
|
|
|
Step = 0.;
|
|
if (MeanNumberOfPhotons > 0.0) Step = fMaxPhotons /
|
|
MeanNumberOfPhotons;
|
|
|
|
if (Step > 0. && Step < StepLimit) StepLimit = Step;
|
|
}
|
|
|
|
// If user has defined an maximum allowed change in beta per step
|
|
if (fMaxBetaChange > 0.) {
|
|
|
|
G4double dedx = G4LossTableManager::Instance()->
|
|
GetDEDX(particleType,
|
|
kineticEnergy,
|
|
couple);
|
|
|
|
G4double deltaGamma = gamma -
|
|
1./std::sqrt(1.-beta*beta*
|
|
(1.-fMaxBetaChange)*
|
|
(1.-fMaxBetaChange));
|
|
|
|
Step = mass * deltaGamma / dedx;
|
|
|
|
if (Step > 0. && Step < StepLimit) StepLimit = Step;
|
|
|
|
}
|
|
|
|
*condition = StronglyForced;
|
|
return StepLimit;
|
|
}
|
|
|
|
// GetAverageNumberOfPhotons
|
|
// -------------------------
|
|
// This routine computes the number of Cerenkov photons produced per
|
|
// GEANT-unit (millimeter) in the current medium.
|
|
// ^^^^^^^^^^
|
|
|
|
G4double
|
|
G4Cerenkov::GetAverageNumberOfPhotons(const G4double charge,
|
|
const G4double beta,
|
|
const G4Material* aMaterial,
|
|
G4MaterialPropertyVector* Rindex) const
|
|
{
|
|
const G4double Rfact = 369.81/(eV * cm);
|
|
|
|
if(beta <= 0.0)return 0.0;
|
|
|
|
G4double BetaInverse = 1./beta;
|
|
|
|
// Vectors used in computation of Cerenkov Angle Integral:
|
|
// - Refraction Indices for the current material
|
|
// - new G4PhysicsOrderedFreeVector allocated to hold CAI's
|
|
|
|
G4int materialIndex = aMaterial->GetIndex();
|
|
|
|
// Retrieve the Cerenkov Angle Integrals for this material
|
|
|
|
G4PhysicsOrderedFreeVector* CerenkovAngleIntegrals =
|
|
(G4PhysicsOrderedFreeVector*)((*thePhysicsTable)(materialIndex));
|
|
|
|
if(!(CerenkovAngleIntegrals->IsFilledVectorExist()))return 0.0;
|
|
|
|
// Min and Max photon energies
|
|
G4double Pmin = Rindex->GetMinLowEdgeEnergy();
|
|
G4double Pmax = Rindex->GetMaxLowEdgeEnergy();
|
|
|
|
// Min and Max Refraction Indices
|
|
G4double nMin = Rindex->GetMinValue();
|
|
G4double nMax = Rindex->GetMaxValue();
|
|
|
|
// Max Cerenkov Angle Integral
|
|
G4double CAImax = CerenkovAngleIntegrals->GetMaxValue();
|
|
|
|
G4double dp, ge;
|
|
|
|
// If n(Pmax) < 1/Beta -- no photons generated
|
|
|
|
if (nMax < BetaInverse) {
|
|
dp = 0;
|
|
ge = 0;
|
|
}
|
|
|
|
// otherwise if n(Pmin) >= 1/Beta -- photons generated
|
|
|
|
else if (nMin > BetaInverse) {
|
|
dp = Pmax - Pmin;
|
|
ge = CAImax;
|
|
}
|
|
|
|
// If n(Pmin) < 1/Beta, and n(Pmax) >= 1/Beta, then
|
|
// we need to find a P such that the value of n(P) == 1/Beta.
|
|
// Interpolation is performed by the GetEnergy() and
|
|
// Value() methods of the G4MaterialPropertiesTable and
|
|
// the GetValue() method of G4PhysicsVector.
|
|
|
|
else {
|
|
Pmin = Rindex->GetEnergy(BetaInverse);
|
|
dp = Pmax - Pmin;
|
|
|
|
// need boolean for current implementation of G4PhysicsVector
|
|
// ==> being phased out
|
|
G4bool isOutRange;
|
|
G4double CAImin = CerenkovAngleIntegrals->
|
|
GetValue(Pmin, isOutRange);
|
|
ge = CAImax - CAImin;
|
|
|
|
if (verboseLevel>0) {
|
|
G4cout << "CAImin = " << CAImin << G4endl;
|
|
G4cout << "ge = " << ge << G4endl;
|
|
}
|
|
}
|
|
|
|
// Calculate number of photons
|
|
G4double NumPhotons = Rfact * charge/eplus * charge/eplus *
|
|
(dp - ge * BetaInverse*BetaInverse);
|
|
|
|
return NumPhotons;
|
|
}
|