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28 //
29 ////////////////////////////////////////////////////////////////////////
30 // Optical Photon Rayleigh Scattering Class Implementation
31 ////////////////////////////////////////////////////////////////////////
32 //
33 // File: G4OpRayleigh.cc
34 // Description: Discrete Process -- Rayleigh scattering of optical
35 // photons
36 // Version: 1.0
37 // Created: 1996-05-31
38 // Author: Juliet Armstrong
39 // Updated: 2014-10-10 - This version calculates the Rayleigh scattering
40 // length for more materials than just Water (although the Water
41 // default is kept). To do this the user would need to specify the
42 // ISOTHERMAL_COMPRESSIBILITY as a material property and
43 // optionally an RS_SCALE_LENGTH (useful for testing). Code comes
44 // from Philip Graham (Queen Mary University of London).
45 // 2010-06-11 - Fix Bug 207; Thanks to Xin Qian
46 // (Kellogg Radiation Lab of Caltech)
47 // 2005-07-28 - add G4ProcessType to constructor
48 // 2001-10-18 by Peter Gumplinger
49 // eliminate unused variable warning on Linux (gcc-2.95.2)
50 // 2001-09-18 by mma
51 // >numOfMaterials=G4Material::GetNumberOfMaterials() in BuildPhy
52 // 2001-01-30 by Peter Gumplinger
53 // > allow for positiv and negative CosTheta and force the
54 // > new momentum direction to be in the same plane as the
55 // > new and old polarization vectors
56 // 2001-01-29 by Peter Gumplinger
57 // > fix calculation of SinTheta (from CosTheta)
58 // 1997-04-09 by Peter Gumplinger
59 // > new physics/tracking scheme
60 //
61 ////////////////////////////////////////////////////////////////////////
62
63 #include "G4OpRayleigh.hh"
64 #include "G4ios.hh"
65 #include "G4PhysicalConstants.hh"
66 #include "G4SystemOfUnits.hh"
67 #include "G4OpticalParameters.hh"
68 #include "G4OpProcessSubType.hh"
69
70 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
71 G4OpRayleigh::G4OpRayleigh(const G4String& processName, G4ProcessType type)
72 : G4VDiscreteProcess(processName, type)
73 {
74 Initialise();
75 SetProcessSubType(fOpRayleigh);
76 thePhysicsTable = nullptr;
77
78 if(verboseLevel > 0)
79 {
80 G4cout << GetProcessName() << " is created " << G4endl;
81 }
82 }
83
84 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
85 G4OpRayleigh::~G4OpRayleigh()
86 {
87 // VI: inside this PhysicsTable all properties are unique
88 // it is not possible to destroy
89 delete thePhysicsTable;
90 }
91
92 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
93 void G4OpRayleigh::PreparePhysicsTable(const G4ParticleDefinition&)
94 {
95 Initialise();
96 }
97
98 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
99 void G4OpRayleigh::Initialise()
100 {
101 SetVerboseLevel(G4OpticalParameters::Instance()->GetRayleighVerboseLevel());
102 }
103
104 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
105 G4VParticleChange* G4OpRayleigh::PostStepDoIt(const G4Track& aTrack,
106 const G4Step& aStep)
107 {
108 aParticleChange.Initialize(aTrack);
109 const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle();
110
111 if(verboseLevel > 1)
112 {
113 G4cout << "OpRayleigh: Scattering Photon!" << G4endl
114 << "Old Momentum Direction: " << aParticle->GetMomentumDirection()
115 << G4endl << "Old Polarization: " << aParticle->GetPolarization()
116 << G4endl;
117 }
118
119 G4double cosTheta;
120 G4ThreeVector oldMomDir, newMomDir;
121 G4ThreeVector oldPol, newPol;
122 G4double rand;
123 G4double cost, sint, sinphi, cosphi;
124
125 do
126 {
127 // Try to simulate the scattered photon momentum direction
128 // w.r.t. the initial photon momentum direction
129 cost = G4UniformRand();
130 sint = std::sqrt(1. - cost * cost);
131 // consider for the angle 90-180 degrees
132 if(G4UniformRand() < 0.5)
133 cost = -cost;
134
135 // simulate the phi angle
136 rand = twopi * G4UniformRand();
137 sinphi = std::sin(rand);
138 cosphi = std::cos(rand);
139
140 // construct the new momentum direction
141 newMomDir.set(sint * cosphi, sint * sinphi, cost);
142 oldMomDir = aParticle->GetMomentumDirection();
143 newMomDir.rotateUz(oldMomDir);
144
145 // calculate the new polarization direction
146 // The new polarization needs to be in the same plane as the new
147 // momentum direction and the old polarization direction
148 oldPol = aParticle->GetPolarization();
149 newPol = (oldPol - newMomDir.dot(oldPol) * newMomDir).unit();
150
151 // There is a corner case, where the new momentum direction
152 // is the same as old polarization direction:
153 // random generate the azimuthal angle w.r.t. new momentum direction
154 if(newPol.mag() == 0.)
155 {
156 rand = G4UniformRand() * twopi;
157 newPol.set(std::cos(rand), std::sin(rand), 0.);
158 newPol.rotateUz(newMomDir);
159 }
160 else
161 {
162 // There are two directions perpendicular to the new momentum direction
163 if(G4UniformRand() < 0.5)
164 newPol = -newPol;
165 }
166
167 // simulate according to the distribution cos^2(theta)
168 cosTheta = newPol.dot(oldPol);
169 // Loop checking, 13-Aug-2015, Peter Gumplinger
170 } while(std::pow(cosTheta, 2) < G4UniformRand());
171
172 aParticleChange.ProposePolarization(newPol);
173 aParticleChange.ProposeMomentumDirection(newMomDir);
174
175 if(verboseLevel > 1)
176 {
177 G4cout << "New Polarization: " << newPol << G4endl
178 << "Polarization Change: " << *(aParticleChange.GetPolarization())
179 << G4endl << "New Momentum Direction: " << newMomDir << G4endl
180 << "Momentum Change: " << *(aParticleChange.GetMomentumDirection())
181 << G4endl;
182 }
183
184 return G4VDiscreteProcess::PostStepDoIt(aTrack, aStep);
185 }
186
187 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
188 void G4OpRayleigh::BuildPhysicsTable(const G4ParticleDefinition&)
189 {
190 if(thePhysicsTable)
191 {
192 // thePhysicsTable->clearAndDestroy();
193 delete thePhysicsTable;
194 thePhysicsTable = nullptr;
195 }
196
197 const G4MaterialTable* theMaterialTable = G4Material::GetMaterialTable();
198 const size_t numOfMaterials = G4Material::GetNumberOfMaterials();
199 thePhysicsTable = new G4PhysicsTable(numOfMaterials);
200
201 for(size_t i = 0; i < numOfMaterials; ++i)
202 {
203 G4Material* material = (*theMaterialTable)[i];
204 G4MaterialPropertiesTable* matProp = material->GetMaterialPropertiesTable();
205 G4PhysicsFreeVector* rayleigh = nullptr;
206 if(matProp)
207 {
208 rayleigh = matProp->GetProperty(kRAYLEIGH);
209 if(rayleigh == nullptr)
210 rayleigh = CalculateRayleighMeanFreePaths(material);
211 }
212 thePhysicsTable->insertAt(i, rayleigh);
213 }
214 }
215
216 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
217 G4double G4OpRayleigh::GetMeanFreePath(const G4Track& aTrack, G4double,
218 G4ForceCondition*)
219 {
220 auto rayleigh = static_cast<G4PhysicsFreeVector*>(
221 (*thePhysicsTable)(aTrack.GetMaterial()->GetIndex()));
222
223 G4double rsLength = DBL_MAX;
224 if(rayleigh)
225 {
226 rsLength = rayleigh->Value(aTrack.GetDynamicParticle()->GetTotalMomentum(),
227 idx_rslength);
228 }
229 return rsLength;
230 }
231
232 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
233 G4PhysicsFreeVector* G4OpRayleigh::CalculateRayleighMeanFreePaths(
234 const G4Material* material) const
235 {
236 G4MaterialPropertiesTable* MPT = material->GetMaterialPropertiesTable();
237
238 // Retrieve the beta_T or isothermal compressibility value. For backwards
239 // compatibility use a constant if the material is "Water". If the material
240 // doesn't have an ISOTHERMAL_COMPRESSIBILITY constant then return
241 G4double betat;
242 if(material->GetName() == "Water")
243 {
244 betat = 7.658e-23 * m3 / MeV;
245 }
246 else if(MPT->ConstPropertyExists(kISOTHERMAL_COMPRESSIBILITY))
247 {
248 betat = MPT->GetConstProperty(kISOTHERMAL_COMPRESSIBILITY);
249 }
250 else
251 {
252 return nullptr;
253 }
254
255 // If the material doesn't have a RINDEX property vector then return
256 G4MaterialPropertyVector* rIndex = MPT->GetProperty(kRINDEX);
257 if(rIndex == nullptr)
258 return nullptr;
259
260 // Retrieve the optional scale factor (scales the scattering length)
261 G4double scaleFactor = 1.0;
262 if(MPT->ConstPropertyExists(kRS_SCALE_FACTOR))
263 {
264 scaleFactor = MPT->GetConstProperty(kRS_SCALE_FACTOR);
265 }
266
267 // Retrieve the material temperature. For backwards compatibility use a
268 // constant if the material is "Water"
269 G4double temperature;
270 if(material->GetName() == "Water")
271 {
272 temperature =
273 283.15 * kelvin; // Temperature of water is 10 degrees celsius
274 }
275 else
276 {
277 temperature = material->GetTemperature();
278 }
279
280 auto rayleighMFPs = new G4PhysicsFreeVector();
281 // This calculates the meanFreePath via the Einstein-Smoluchowski formula
282 const G4double c1 =
283 scaleFactor * betat * temperature * k_Boltzmann / (6.0 * pi);
284
285 for(size_t uRIndex = 0; uRIndex < rIndex->GetVectorLength(); ++uRIndex)
286 {
287 const G4double energy = rIndex->Energy(uRIndex);
288 const G4double rIndexSquared = (*rIndex)[uRIndex] * (*rIndex)[uRIndex];
289 const G4double xlambda = h_Planck * c_light / energy;
290 const G4double c2 = std::pow(twopi / xlambda, 4);
291 const G4double c3 =
292 std::pow(((rIndexSquared - 1.0) * (rIndexSquared + 2.0) / 3.0), 2);
293
294 const G4double meanFreePath = 1.0 / (c1 * c2 * c3);
295
296 if(verboseLevel > 0)
297 {
298 G4cout << energy << "MeV\t" << meanFreePath << "mm" << G4endl;
299 }
300
301 rayleighMFPs->InsertValues(energy, meanFreePath);
302 }
303
304 return rayleighMFPs;
305 }
306
307 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
308 void G4OpRayleigh::SetVerboseLevel(G4int verbose)
309 {
310 verboseLevel = verbose;
311 G4OpticalParameters::Instance()->SetRayleighVerboseLevel(verboseLevel);
312 }
313