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27 // -------------------------------------------------------------------
28 //
29 // GEANT4 Class header file
30 //
31 //
32 // File name: G4mplIonisationModel
33 //
34 // Author: Vladimir Ivanchenko
35 //
36 // Creation date: 06.09.2005
37 //
38 // Modifications:
39 // 12.08.2007 Changing low energy approximation and extrapolation.
40 // Small bug fixing and refactoring (M. Vladymyrov)
41 // 13.11.2007 Use low-energy asymptotic from [3] (V.Ivanchenko)
42 //
43 //
44 // -------------------------------------------------------------------
45 // References
46 // [1] Steven P. Ahlen: Energy loss of relativistic heavy ionizing particles,
47 // S.P. Ahlen, Rev. Mod. Phys 52(1980), p121
48 // [2] K.A. Milton arXiv:hep-ex/0602040
49 // [3] S.P. Ahlen and K. Kinoshita, Phys. Rev. D26 (1982) 2347
50
51
52 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
53 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
54
55 #include "G4mplIonisationModel.hh"
56 #include "Randomize.hh"
57 #include "G4PhysicalConstants.hh"
58 #include "G4SystemOfUnits.hh"
59 #include "G4ParticleChangeForLoss.hh"
60 #include "G4ProductionCutsTable.hh"
61 #include "G4MaterialCutsCouple.hh"
62 #include "G4Log.hh"
63 #include "G4Pow.hh"
64
65 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
66
67 std::vector<G4double>* G4mplIonisationModel::dedx0 = nullptr;
68
69 G4mplIonisationModel::G4mplIonisationModel(G4double mCharge, const G4String& nam)
70 : G4VEmModel(nam),G4VEmFluctuationModel(nam),
71 magCharge(mCharge),
72 twoln10(G4Log(100.0)),
73 betalow(0.01),
74 betalim(0.1),
75 beta2lim(betalim*betalim),
76 bg2lim(beta2lim*(1.0 + beta2lim))
77 {
78 nmpl = G4int(std::abs(magCharge) * 2 * CLHEP::fine_structure_const + 0.5);
79 if(nmpl > 6) { nmpl = 6; }
80 else if(nmpl < 1) { nmpl = 1; }
81 pi_hbarc2_over_mc2 = CLHEP::pi*CLHEP::hbarc*CLHEP::hbarc/CLHEP::electron_mass_c2;
82 chargeSquare = magCharge * magCharge;
83 dedxlim = 45.*nmpl*nmpl*CLHEP::GeV*CLHEP::cm2/CLHEP::g;
84 }
85
86 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
87
88 G4mplIonisationModel::~G4mplIonisationModel()
89 {
90 if(IsMaster()) { delete dedx0; }
91 }
92
93 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
94
95 void G4mplIonisationModel::SetParticle(const G4ParticleDefinition* p)
96 {
97 monopole = p;
98 mass = monopole->GetPDGMass();
99 G4double emin =
100 std::min(LowEnergyLimit(),0.1*mass*(1./std::sqrt(1. - betalow*betalow) - 1.));
101 G4double emax =
102 std::max(HighEnergyLimit(),10.*mass*(1./std::sqrt(1. - beta2lim) - 1.));
103 SetLowEnergyLimit(emin);
104 SetHighEnergyLimit(emax);
105 }
106
107 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
108
109 void G4mplIonisationModel::Initialise(const G4ParticleDefinition* p,
110 const G4DataVector&)
111 {
112 if(nullptr == monopole) { SetParticle(p); }
113 if(nullptr == fParticleChange) { fParticleChange = GetParticleChangeForLoss(); }
114 if(IsMaster()) {
115 if(nullptr == dedx0) { dedx0 = new std::vector<G4double>; }
116 G4ProductionCutsTable* theCoupleTable=
117 G4ProductionCutsTable::GetProductionCutsTable();
118 G4int numOfCouples = (G4int)theCoupleTable->GetTableSize();
119 G4int n = (G4int)dedx0->size();
120 if(n < numOfCouples) { dedx0->resize(numOfCouples); }
121
122 G4Pow* g4calc = G4Pow::GetInstance();
123
124 // initialise vector assuming low conductivity
125 for(G4int i=0; i<numOfCouples; ++i) {
126
127 const G4Material* material =
128 theCoupleTable->GetMaterialCutsCouple(i)->GetMaterial();
129 G4double eDensity = material->GetElectronDensity();
130 G4double vF2 = 2*electron_Compton_length*g4calc->A13(3.*pi*pi*eDensity);
131 (*dedx0)[i] = pi_hbarc2_over_mc2*eDensity*nmpl*nmpl*
132 (G4Log(vF2/fine_structure_const) - 0.5)/vF2;
133 }
134 }
135 }
136
137 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
138
139 G4double G4mplIonisationModel::ComputeDEDXPerVolume(const G4Material* material,
140 const G4ParticleDefinition* p,
141 G4double kineticEnergy,
142 G4double)
143 {
144 if(nullptr == monopole) { SetParticle(p); }
145 G4double tau = kineticEnergy / mass;
146 G4double gam = tau + 1.0;
147 G4double bg2 = tau * (tau + 2.0);
148 G4double beta2 = bg2 / (gam * gam);
149 G4double beta = std::sqrt(beta2);
150
151 // low-energy asymptotic formula
152 //G4double dedx = dedxlim*beta*material->GetDensity();
153 G4double dedx = (*dedx0)[CurrentCouple()->GetIndex()]*beta;
154
155 // above asymptotic
156 if(beta > betalow) {
157
158 // high energy
159 if(beta >= betalim) {
160 dedx = ComputeDEDXAhlen(material, bg2);
161
162 } else {
163
164 //G4double dedx1 = dedxlim*betalow*material->GetDensity();
165 G4double dedx1 = (*dedx0)[CurrentCouple()->GetIndex()]*betalow;
166 G4double dedx2 = ComputeDEDXAhlen(material, bg2lim);
167
168 // extrapolation between two formula
169 G4double kapa2 = beta - betalow;
170 G4double kapa1 = betalim - beta;
171 dedx = (kapa1*dedx1 + kapa2*dedx2)/(kapa1 + kapa2);
172 }
173 }
174 return dedx;
175 }
176
177 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
178
179 G4double G4mplIonisationModel::ComputeDEDXAhlen(const G4Material* material,
180 G4double bg2)
181 {
182 G4double eDensity = material->GetElectronDensity();
183 G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy();
184 G4double cden = material->GetIonisation()->GetCdensity();
185 G4double mden = material->GetIonisation()->GetMdensity();
186 G4double aden = material->GetIonisation()->GetAdensity();
187 G4double x0den = material->GetIonisation()->GetX0density();
188 G4double x1den = material->GetIonisation()->GetX1density();
189
190 // Ahlen's formula for nonconductors, [1]p157, f(5.7)
191 G4double dedx = std::log(2.0 * electron_mass_c2 * bg2 / eexc) - 0.5;
192
193 // Kazama et al. cross-section correction
194 G4double k = 0.406;
195 if(nmpl > 1) k = 0.346;
196
197 // Bloch correction
198 const G4double B[7] = { 0.0, 0.248, 0.672, 1.022, 1.243, 1.464, 1.685};
199
200 dedx += 0.5 * k - B[nmpl];
201
202 // density effect correction
203 G4double deltam;
204 G4double x = std::log(bg2) / twoln10;
205 if ( x >= x0den ) {
206 deltam = twoln10 * x - cden;
207 if ( x < x1den ) deltam += aden * std::pow((x1den-x), mden);
208 dedx -= 0.5 * deltam;
209 }
210
211 // now compute the total ionization loss
212 dedx *= pi_hbarc2_over_mc2 * eDensity * nmpl * nmpl;
213
214 if (dedx < 0.0) dedx = 0.;
215 return dedx;
216 }
217
218 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
219
220 void G4mplIonisationModel::SampleSecondaries(std::vector<G4DynamicParticle*>*,
221 const G4MaterialCutsCouple*,
222 const G4DynamicParticle*,
223 G4double,
224 G4double)
225 {}
226
227 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
228
229 G4double G4mplIonisationModel::SampleFluctuations(
230 const G4MaterialCutsCouple* couple,
231 const G4DynamicParticle* dp,
232 const G4double tcut,
233 const G4double tmax,
234 const G4double length,
235 const G4double meanLoss)
236 {
237 G4double siga = Dispersion(couple->GetMaterial(),dp,tcut,tmax,length);
238 G4double loss = meanLoss;
239 siga = std::sqrt(siga);
240 G4double twomeanLoss = meanLoss + meanLoss;
241
242 if(twomeanLoss < siga) {
243 G4double x;
244 do {
245 loss = twomeanLoss*G4UniformRand();
246 x = (loss - meanLoss)/siga;
247 // Loop checking, 07-Aug-2015, Vladimir Ivanchenko
248 } while (1.0 - 0.5*x*x < G4UniformRand());
249 } else {
250 do {
251 loss = G4RandGauss::shoot(meanLoss,siga);
252 // Loop checking, 07-Aug-2015, Vladimir Ivanchenko
253 } while (0.0 > loss || loss > twomeanLoss);
254 }
255 return loss;
256 }
257
258 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
259
260 G4double G4mplIonisationModel::Dispersion(const G4Material* material,
261 const G4DynamicParticle* dp,
262 const G4double tcut,
263 const G4double tmax,
264 const G4double length)
265 {
266 G4double siga = 0.0;
267 G4double tau = dp->GetKineticEnergy()/mass;
268 if(tau > 0.0) {
269 const G4double beta = dp->GetBeta();
270 siga = (tmax/(beta*beta) - 0.5*tcut) * twopi_mc2_rcl2 * length
271 * material->GetElectronDensity() * chargeSquare;
272 }
273 return siga;
274 }
275
276 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
277