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25 //
26 //
27 // -------------------------------------------------------------------
28 //
29 //
30 // GEANT4 Class header file
31 //
32 //
33 // File name: G4UrbanMscModel
34 //
35 // Author: Laszlo Urban
36 //
37 // Creation date: 19.02.2013
38 //
39 // Created from G4UrbanMscModel96
40 //
41 // New parametrization for theta0
42 // Correction for very small step length
43 //
44 // Class Description:
45 //
46 // Implementation of the model of multiple scattering based on
47 // H.W.Lewis Phys Rev 78 (1950) 526 and L.Urban model
48
49 // -------------------------------------------------------------------
50 //
51
52 #ifndef G4UrbanMscModel_h
53 #define G4UrbanMscModel_h 1
54
55 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
56
57 #include <CLHEP/Units/SystemOfUnits.h>
58
59 #include "G4VMscModel.hh"
60 #include "G4MscStepLimitType.hh"
61 #include "G4Log.hh"
62 #include "G4Exp.hh"
63
64 class G4ParticleChangeForMSC;
65 class G4SafetyHelper;
66
67 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
68
69 class G4UrbanMscModel : public G4VMscModel
70 {
71
72 public:
73
74 explicit G4UrbanMscModel(const G4String& nam = "UrbanMsc");
75
76 ~G4UrbanMscModel() override;
77
78 void Initialise(const G4ParticleDefinition*,
79 const G4DataVector&) override;
80
81 void StartTracking(G4Track*) override;
82
83 G4double
84 ComputeCrossSectionPerAtom(const G4ParticleDefinition* particle,
85 G4double KineticEnergy,
86 G4double AtomicNumber,
87 G4double AtomicWeight=0.,
88 G4double cut =0.,
89 G4double emax=DBL_MAX) override;
90
91 G4ThreeVector& SampleScattering(const G4ThreeVector&,
92 G4double safety) override;
93
94 G4double ComputeTruePathLengthLimit(const G4Track& track,
95 G4double& currentMinimalStep) override;
96
97 G4double ComputeGeomPathLength(G4double truePathLength) override;
98
99 G4double ComputeTrueStepLength(G4double geomStepLength) override;
100
101 G4double ComputeTheta0(G4double truePathLength, G4double KineticEnergy);
102
103 inline void SetDisplacementAlgorithm96(const G4bool val);
104
105 inline void SetPositronCorrection(const G4bool val);
106
107 // hide assignment operator
108 G4UrbanMscModel & operator=(const G4UrbanMscModel &right) = delete;
109 G4UrbanMscModel(const G4UrbanMscModel&) = delete;
110
111 private:
112
113 G4double SampleCosineTheta(G4double trueStepLength, G4double KineticEnergy);
114
115 void SampleDisplacement(G4double sinTheta, G4double phi);
116
117 void SampleDisplacementNew(G4double sinTheta, G4double phi);
118
119 void InitialiseModelCache();
120
121 inline void SetParticle(const G4ParticleDefinition*);
122
123 inline G4double Randomizetlimit();
124
125 inline G4double SimpleScattering();
126
127 inline G4double ComputeStepmin();
128
129 inline G4double ComputeTlimitmin();
130
131 CLHEP::HepRandomEngine* rndmEngineMod;
132
133 const G4ParticleDefinition* particle = nullptr;
134 const G4ParticleDefinition* positron;
135 G4ParticleChangeForMSC* fParticleChange = nullptr;
136 const G4MaterialCutsCouple* couple = nullptr;
137
138 G4double mass;
139 G4double charge,chargeSquare;
140 G4double masslimite,fr;
141
142 G4double taubig;
143 G4double tausmall;
144 G4double taulim;
145 G4double currentTau;
146 G4double tlimit;
147 G4double tlimitmin;
148 G4double tlimitminfix,tlimitminfix2;
149 G4double tgeom;
150
151 G4double geombig;
152 G4double geommin;
153 G4double geomlimit;
154 G4double skindepth;
155 G4double smallstep;
156
157 G4double presafety;
158
159 G4double lambda0;
160 G4double lambdaeff;
161 G4double tPathLength;
162 G4double zPathLength;
163 G4double par1,par2,par3;
164
165 G4double stepmin;
166
167 G4double currentKinEnergy;
168 G4double currentLogKinEnergy;
169 G4double currentRange;
170 G4double rangeinit;
171 G4double currentRadLength;
172
173 G4double drr,finalr;
174
175 G4double tlow;
176 G4double invmev;
177 G4double xmeanth = 0.0;
178 G4double x2meanth = 1./3.;
179 G4double rndmarray[2];
180
181 struct mscData {
182 G4double Z23, sqrtZ, factmin;
183 G4double coeffth1, coeffth2;
184 G4double coeffc1, coeffc2, coeffc3, coeffc4;
185 G4double stepmina, stepminb;
186 G4double doverra, doverrb;
187 G4double posa, posb, posc, posd, pose;
188 };
189 static std::vector<mscData*> msc;
190
191 // index of G4MaterialCutsCouple
192 G4int idx = 0;
193
194 G4bool firstStep = true;
195 G4bool insideskin = false;
196
197 G4bool latDisplasmentbackup = false;
198 G4bool dispAlg96 = true;
199 G4bool fPosiCorrection = true;
200 G4bool isFirstInstance = false;
201 };
202
203 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
204 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
205
206 inline
207 void G4UrbanMscModel::SetParticle(const G4ParticleDefinition* p)
208 {
209 if (p != particle) {
210 particle = p;
211 mass = p->GetPDGMass();
212 charge = p->GetPDGCharge()/CLHEP::eplus;
213 chargeSquare = charge*charge;
214 }
215 }
216
217 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
218
219 inline G4double G4UrbanMscModel::Randomizetlimit()
220 {
221 G4double res = tlimitmin;
222 if(tlimit > tlimitmin)
223 {
224 res = G4RandGauss::shoot(rndmEngineMod,tlimit,0.1*(tlimit-tlimitmin));
225 res = std::max(res, tlimitmin);
226 }
227 return res;
228 }
229
230 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
231
232 inline G4double G4UrbanMscModel::SimpleScattering()
233 {
234 // 'large angle scattering'
235 // 2 model functions with correct xmean and x2mean
236 const G4double a = (2.*xmeanth+9.*x2meanth-3.)/(2.*xmeanth-3.*x2meanth+1.);
237 const G4double prob = (a+2.)*xmeanth/a;
238
239 // sampling
240 rndmEngineMod->flatArray(2, rndmarray);
241 return (rndmarray[1] < prob) ?
242 -1.+2.*G4Exp(G4Log(rndmarray[0])/(a+1.)) : -1.+2.*rndmarray[0];
243 }
244
245 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
246
247 inline G4double G4UrbanMscModel::ComputeStepmin()
248 {
249 // define stepmin using estimation of the ratio
250 // of lambda_elastic/lambda_transport
251 const G4double rat = currentKinEnergy*invmev;
252 return lambda0*msc[idx]->factmin/
253 (0.002 + rat*(msc[idx]->stepmina + msc[idx]->stepminb*rat));
254 }
255
256 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
257
258 inline G4double G4UrbanMscModel::ComputeTlimitmin()
259 {
260 G4double x = (particle == positron) ?
261 0.7*msc[idx]->sqrtZ*stepmin : 0.87*msc[idx]->Z23*stepmin;
262 if(currentKinEnergy < tlow) { x *= 0.5*(1.+currentKinEnergy/tlow); }
263 return std::max(x, tlimitminfix);
264 }
265
266 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
267
268 inline void G4UrbanMscModel::SetDisplacementAlgorithm96(const G4bool val)
269 {
270 dispAlg96 = val;
271 }
272
273 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
274
275 inline void G4UrbanMscModel::SetPositronCorrection(const G4bool val)
276 {
277 fPosiCorrection = val;
278 }
279
280 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
281
282 #endif
283
284