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26 // $Id: G4mplIonisationWithDeltaModel.cc 97391 2016-06-02 10:08:45Z gcosmo $
27 //
28 // -------------------------------------------------------------------
29 //
30 // GEANT4 Class header file
31 //
32 //
33 // File name: G4mplIonisationWithDeltaModel
34 //
35 // Author: Vladimir Ivanchenko
36 //
37 // Creation date: 06.09.2005
38 //
39 // Modifications:
40 // 12.08.2007 Changing low energy approximation and extrapolation.
41 // Small bug fixing and refactoring (M. Vladymyrov)
42 // 13.11.2007 Use low-energy asymptotic from [3] (V.Ivanchenko)
43 //
44 //
45 // -------------------------------------------------------------------
46 // References
47 // [1] Steven P. Ahlen: Energy loss of relativistic heavy ionizing particles,
48 // S.P. Ahlen, Rev. Mod. Phys 52(1980), p121
49 // [2] K.A. Milton arXiv:hep-ex/0602040
50 // [3] S.P. Ahlen and K. Kinoshita, Phys. Rev. D26 (1982) 2347
51
52
53 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
54 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
55
56 #include "G4mplIonisationWithDeltaModel.hh"
57 #include "Randomize.hh"
58 #include "G4PhysicalConstants.hh"
59 #include "G4SystemOfUnits.hh"
60 #include "G4ParticleChangeForLoss.hh"
61 #include "G4Electron.hh"
62 #include "G4DynamicParticle.hh"
63 #include "G4ProductionCutsTable.hh"
64 #include "G4MaterialCutsCouple.hh"
65 #include "G4Log.hh"
66
67 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
68
69 using namespace std;
70
71 std::vector<G4double>* G4mplIonisationWithDeltaModel::dedx0 = nullptr;
72
73 G4mplIonisationWithDeltaModel::G4mplIonisationWithDeltaModel(G4double mCharge,
74 const G4String& nam)
75 : G4VEmModel(nam),G4VEmFluctuationModel(nam),
76 magCharge(mCharge),
77 twoln10(log(100.0)),
78 betalow(0.01),
79 betalim(0.1),
80 beta2lim(betalim*betalim),
81 bg2lim(beta2lim*(1.0 + beta2lim))
82 {
83 nmpl = G4lrint(std::fabs(magCharge) * 2 * fine_structure_const);
84 if(nmpl > 6) { nmpl = 6; }
85 else if(nmpl < 1) { nmpl = 1; }
86 pi_hbarc2_over_mc2 = pi * hbarc * hbarc / electron_mass_c2;
87 chargeSquare = magCharge * magCharge;
88 dedxlim = 45.*nmpl*nmpl*GeV*cm2/g;
89 fParticleChange = nullptr;
90 theElectron = G4Electron::Electron();
91 G4cout << "### Monopole ionisation model with d-electron production, Gmag= "
92 << magCharge/eplus << G4endl;
93 monopole = nullptr;
94 mass = 0.0;
95 }
96
97 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
98
99 G4mplIonisationWithDeltaModel::~G4mplIonisationWithDeltaModel()
100 {
101 if(IsMaster()) { delete dedx0; }
102 }
103
104 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
105
106 void G4mplIonisationWithDeltaModel::SetParticle(const G4ParticleDefinition* p)
107 {
108 monopole = p;
109 mass = monopole->GetPDGMass();
110 G4double emin =
111 std::min(LowEnergyLimit(),0.1*mass*(1./sqrt(1. - betalow*betalow) - 1.));
112 G4double emax =
113 std::max(HighEnergyLimit(),10*mass*(1./sqrt(1. - beta2lim) - 1.));
114 SetLowEnergyLimit(emin);
115 SetHighEnergyLimit(emax);
116 }
117
118 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
119
120 void
121 G4mplIonisationWithDeltaModel::Initialise(const G4ParticleDefinition* p,
122 const G4DataVector&)
123 {
124 if(!monopole) { SetParticle(p); }
125 if(!fParticleChange) { fParticleChange = GetParticleChangeForLoss(); }
126 if(IsMaster()) {
127 if(!dedx0) { dedx0 = new std::vector<G4double>; }
128 G4ProductionCutsTable* theCoupleTable=
129 G4ProductionCutsTable::GetProductionCutsTable();
130 G4int numOfCouples = theCoupleTable->GetTableSize();
131 G4int n = dedx0->size();
132 if(n < numOfCouples) { dedx0->resize(numOfCouples); }
133
134 // initialise vector
135 for(G4int i=0; i<numOfCouples; ++i) {
136
137 const G4Material* material =
138 theCoupleTable->GetMaterialCutsCouple(i)->GetMaterial();
139 G4double eDensity = material->GetElectronDensity();
140 G4double vF = electron_Compton_length*pow(3.*pi*pi*eDensity,0.3333333333);
141 (*dedx0)[i] = pi_hbarc2_over_mc2*eDensity*nmpl*nmpl*
142 (G4Log(2*vF/fine_structure_const) - 0.5)/vF;
143 }
144 }
145 }
146
147 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
148
149 G4double
150 G4mplIonisationWithDeltaModel::ComputeDEDXPerVolume(const G4Material* material,
151 const G4ParticleDefinition* p,
152 G4double kineticEnergy,
153 G4double maxEnergy)
154 {
155 if(!monopole) { SetParticle(p); }
156 G4double tmax = MaxSecondaryEnergy(p,kineticEnergy);
157 G4double cutEnergy = std::min(tmax, maxEnergy);
158 cutEnergy = std::max(LowEnergyLimit(), cutEnergy);
159 G4double tau = kineticEnergy / mass;
160 G4double gam = tau + 1.0;
161 G4double bg2 = tau * (tau + 2.0);
162 G4double beta2 = bg2 / (gam * gam);
163 G4double beta = sqrt(beta2);
164
165 // low-energy asymptotic formula
166 //G4double dedx = dedxlim*beta*material->GetDensity();
167 G4double dedx = (*dedx0)[CurrentCouple()->GetIndex()]*beta;
168
169 // above asymptotic
170 if(beta > betalow) {
171
172 // high energy
173 if(beta >= betalim) {
174 dedx = ComputeDEDXAhlen(material, bg2, cutEnergy);
175
176 } else {
177
178 //G4double dedx1 = dedxlim*betalow*material->GetDensity();
179 G4double dedx1 = (*dedx0)[CurrentCouple()->GetIndex()]*betalow;
180 G4double dedx2 = ComputeDEDXAhlen(material, bg2lim, cutEnergy);
181
182 // extrapolation between two formula
183 G4double kapa2 = beta - betalow;
184 G4double kapa1 = betalim - beta;
185 dedx = (kapa1*dedx1 + kapa2*dedx2)/(kapa1 + kapa2);
186 }
187 }
188 return dedx;
189 }
190
191 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
192
193 G4double
194 G4mplIonisationWithDeltaModel::ComputeDEDXAhlen(const G4Material* material,
195 G4double bg2,
196 G4double cutEnergy)
197 {
198 G4double eDensity = material->GetElectronDensity();
199 G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy();
200
201 // Ahlen's formula for nonconductors, [1]p157, f(5.7)
202 G4double dedx =
203 0.5*(log(2.0 * electron_mass_c2 * bg2*cutEnergy / (eexc*eexc)) - 1.0);
204
205 // Kazama et al. cross-section correction
206 G4double k = 0.406;
207 if(nmpl > 1) { k = 0.346; }
208
209 // Bloch correction
210 const G4double B[7] = { 0.0, 0.248, 0.672, 1.022, 1.243, 1.464, 1.685};
211
212 dedx += 0.5 * k - B[nmpl];
213
214 // density effect correction
215 G4double x = G4Log(bg2)/twoln10;
216 dedx -= material->GetIonisation()->DensityCorrection(x);
217
218 // now compute the total ionization loss
219 dedx *= pi_hbarc2_over_mc2 * eDensity * nmpl * nmpl;
220
221 if (dedx < 0.0) { dedx = 0.; }
222 return dedx;
223 }
224
225 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
226
227 G4double
228 G4mplIonisationWithDeltaModel::ComputeCrossSectionPerElectron(
229 const G4ParticleDefinition* p,
230 G4double kineticEnergy,
231 G4double cut,
232 G4double maxKinEnergy)
233 {
234 if(!monopole) { SetParticle(p); }
235 G4double cross = 0.0;
236 G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
237 G4double maxEnergy = std::min(tmax,maxKinEnergy);
238 G4double cutEnergy = std::max(LowEnergyLimit(), cut);
239 if(cutEnergy < maxEnergy) {
240 cross = (0.5/cutEnergy - 0.5/maxEnergy)*pi_hbarc2_over_mc2 * nmpl * nmpl;
241 }
242 return cross;
243 }
244
245 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
246
247 G4double
248 G4mplIonisationWithDeltaModel::ComputeCrossSectionPerAtom(
249 const G4ParticleDefinition* p,
250 G4double kineticEnergy,
251 G4double Z, G4double,
252 G4double cutEnergy,
253 G4double maxEnergy)
254 {
255 G4double cross =
256 Z*ComputeCrossSectionPerElectron(p,kineticEnergy,cutEnergy,maxEnergy);
257 return cross;
258 }
259
260 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
261
262 void
263 G4mplIonisationWithDeltaModel::SampleSecondaries(vector<G4DynamicParticle*>* vdp,
264 const G4MaterialCutsCouple*,
265 const G4DynamicParticle* dp,
266 G4double minKinEnergy,
267 G4double maxEnergy)
268 {
269 G4double kineticEnergy = dp->GetKineticEnergy();
270 G4double tmax = MaxSecondaryEnergy(dp->GetDefinition(),kineticEnergy);
271
272 G4double maxKinEnergy = std::min(maxEnergy,tmax);
273 if(minKinEnergy >= maxKinEnergy) { return; }
274
275 //G4cout << "G4mplIonisationWithDeltaModel::SampleSecondaries: E(GeV)= "
276 // << kineticEnergy/GeV << " M(GeV)= " << mass/GeV
277 // << " tmin(MeV)= " << minKinEnergy/MeV << G4endl;
278
279 G4double totEnergy = kineticEnergy + mass;
280 G4double etot2 = totEnergy*totEnergy;
281 G4double beta2 = kineticEnergy*(kineticEnergy + 2.0*mass)/etot2;
282
283 // sampling without nuclear size effect
284 G4double q = G4UniformRand();
285 G4double deltaKinEnergy = minKinEnergy*maxKinEnergy
286 /(minKinEnergy*(1.0 - q) + maxKinEnergy*q);
287
288 // delta-electron is produced
289 G4double totMomentum = totEnergy*sqrt(beta2);
290 G4double deltaMomentum =
291 sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
292 G4double cost = deltaKinEnergy * (totEnergy + electron_mass_c2) /
293 (deltaMomentum * totMomentum);
294 if(cost > 1.0) { cost = 1.0; }
295
296 G4double sint = sqrt((1.0 - cost)*(1.0 + cost));
297
298 G4double phi = twopi * G4UniformRand() ;
299
300 G4ThreeVector deltaDirection(sint*cos(phi),sint*sin(phi), cost);
301 G4ThreeVector direction = dp->GetMomentumDirection();
302 deltaDirection.rotateUz(direction);
303
304 // create G4DynamicParticle object for delta ray
305 G4DynamicParticle* delta =
306 new G4DynamicParticle(theElectron,deltaDirection,deltaKinEnergy);
307
308 vdp->push_back(delta);
309
310 // Change kinematics of primary particle
311 kineticEnergy -= deltaKinEnergy;
312 G4ThreeVector finalP = direction*totMomentum - deltaDirection*deltaMomentum;
313 finalP = finalP.unit();
314
315 fParticleChange->SetProposedKineticEnergy(kineticEnergy);
316 fParticleChange->SetProposedMomentumDirection(finalP);
317 }
318
319 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
320
321 G4double G4mplIonisationWithDeltaModel::SampleFluctuations(
322 const G4MaterialCutsCouple* couple,
323 const G4DynamicParticle* dp,
324 G4double tmax,
325 G4double length,
326 G4double meanLoss)
327 {
328 G4double siga = Dispersion(couple->GetMaterial(),dp,tmax,length);
329 G4double loss = meanLoss;
330 siga = sqrt(siga);
331 G4double twomeanLoss = meanLoss + meanLoss;
332
333 if(twomeanLoss < siga) {
334 G4double x;
335 do {
336 loss = twomeanLoss*G4UniformRand();
337 x = (loss - meanLoss)/siga;
338 // Loop checking, 07-Aug-2015, Vladimir Ivanchenko
339 } while (1.0 - 0.5*x*x < G4UniformRand());
340 } else {
341 do {
342 loss = G4RandGauss::shoot(meanLoss,siga);
343 // Loop checking, 07-Aug-2015, Vladimir Ivanchenko
344 } while (0.0 > loss || loss > twomeanLoss);
345 }
346 return loss;
347 }
348
349 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
350
351 G4double
352 G4mplIonisationWithDeltaModel::Dispersion(const G4Material* material,
353 const G4DynamicParticle* dp,
354 G4double tmax,
355 G4double length)
356 {
357 G4double siga = 0.0;
358 G4double tau = dp->GetKineticEnergy()/mass;
359 if(tau > 0.0) {
360 G4double electronDensity = material->GetElectronDensity();
361 G4double gam = tau + 1.0;
362 G4double invbeta2 = (gam*gam)/(tau * (tau+2.0));
363 siga = (invbeta2 - 0.5) * twopi_mc2_rcl2 * tmax * length
364 * electronDensity * chargeSquare;
365 }
366 return siga;
367 }
368
369 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
370
371 G4double
372 G4mplIonisationWithDeltaModel::MaxSecondaryEnergy(const G4ParticleDefinition*,
373 G4double kinEnergy)
374 {
375 G4double tau = kinEnergy/mass;
376 return 2.0*electron_mass_c2*tau*(tau + 2.);
377 }
378
379 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
380