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27 // ------------------------------------------- 27 // ----------------------------------------------------------------------------
28 // 28 //
29 // GEANT4 Class implementation file 29 // GEANT4 Class implementation file
30 // 30 //
31 // File name: G4GoudsmitSaundersonMscModel 31 // File name: G4GoudsmitSaundersonMscModel
32 // 32 //
33 // Author: Mihaly Novak / (Omrane Kadri 33 // Author: Mihaly Novak / (Omrane Kadri)
34 // 34 //
35 // Creation date: 20.02.2009 35 // Creation date: 20.02.2009
36 // 36 //
37 // Modifications: 37 // Modifications:
38 // 04.03.2009 V.Ivanchenko cleanup and format 38 // 04.03.2009 V.Ivanchenko cleanup and format according to Geant4 EM style
39 // 12.05.2010 O.Kadri: adding Qn1 and Qn12 as 39 // 12.05.2010 O.Kadri: adding Qn1 and Qn12 as private doubles
40 // 18.05.2015 M. Novak provide PRELIMINARY ver 40 // 18.05.2015 M. Novak provide PRELIMINARY verison of the revised class
41 // This class has been revised and 41 // This class has been revised and updated, new methods added.
42 // A new version of Kawrakow-Bielaj 42 // A new version of Kawrakow-Bielajew Goudsmit-Saunderson MSC model
43 // based on the screened Rutherford 43 // based on the screened Rutherford DCS for elastic scattering of
44 // electrons/positrons has been int 44 // electrons/positrons has been introduced[1,2]. The corresponding MSC
45 // angular distributions over a 2D 45 // angular distributions over a 2D parameter grid have been recomputed
46 // and the CDFs are now stored in a 46 // and the CDFs are now stored in a variable transformed (smooth) form[2,3]
47 // together with the corresponding 47 // together with the corresponding rational interpolation parameters.
48 // These angular distributions are 48 // These angular distributions are handled by the new
49 // G4GoudsmitSaundersonTable class 49 // G4GoudsmitSaundersonTable class that is responsible to sample if
50 // it was no, single, few or multip 50 // it was no, single, few or multiple scattering case and delivers the
51 // angular deflection (i.e. cos(the 51 // angular deflection (i.e. cos(theta) and sin(theta)).
52 // Two screening options are provid 52 // Two screening options are provided:
53 // - if fIsUsePWATotalXsecData=TRU 53 // - if fIsUsePWATotalXsecData=TRUE i.e. SetOptionPWAScreening(TRUE)
54 // was called before initialisat 54 // was called before initialisation: screening parameter value A is
55 // determined such that the firs 55 // determined such that the first transport coefficient G1(A)
56 // computed according to the scr 56 // computed according to the screened Rutherford DCS for elastic
57 // scattering will reproduce the 57 // scattering will reproduce the one computed from the PWA elastic
58 // and first transport mean free 58 // and first transport mean free paths[4].
59 // - if fIsUsePWATotalXsecData=FAL 59 // - if fIsUsePWATotalXsecData=FALSE i.e. default value or
60 // SetOptionPWAScreening(FALSE) 60 // SetOptionPWAScreening(FALSE) was called before initialisation:
61 // screening parameter value A i 61 // screening parameter value A is computed according to Moliere's
62 // formula (by using material de 62 // formula (by using material dependent parameters \chi_cc2 and b_c
63 // precomputed for each material 63 // precomputed for each material used at initialization in
64 // G4GoudsmitSaundersonTable) [3 64 // G4GoudsmitSaundersonTable) [3]
65 // Elastic and first trasport mean 65 // Elastic and first trasport mean free paths are used consistently.
66 // The new version is self-consiste 66 // The new version is self-consistent, several times faster, more
67 // robust and accurate compared to 67 // robust and accurate compared to the earlier version.
68 // Spin effects as well as a more a 68 // Spin effects as well as a more accurate energy loss correction and
69 // computations of Lewis moments wi 69 // computations of Lewis moments will be implemented later on.
70 // 02.09.2015 M. Novak: first version of new s 70 // 02.09.2015 M. Novak: first version of new step limit is provided.
71 // fUseSafetyPlus corresponds to Ur 71 // fUseSafetyPlus corresponds to Urban fUseSafety (default)
72 // fUseDistanceToBoundary correspon 72 // fUseDistanceToBoundary corresponds to Urban fUseDistanceToBoundary
73 // fUseSafety corresponds to EGSnr 73 // fUseSafety corresponds to EGSnrc error-free stepping algorithm
74 // Range factor can be significantl 74 // Range factor can be significantly higher at each case than in Urban.
75 // 23.08.2017 M. Novak: added corrections to a 75 // 23.08.2017 M. Novak: added corrections to account spin effects (Mott-correction).
76 // It can be activated by setting t 76 // It can be activated by setting the fIsMottCorrection flag to be true
77 // before initialization using the 77 // before initialization using the SetOptionMottCorrection() public method.
78 // The fMottCorrection member is re 78 // The fMottCorrection member is responsible to handle pre-computed Mott
79 // correction (rejection) functions 79 // correction (rejection) functions obtained by numerically computing
80 // Goudsmit-Saunderson agnular dist 80 // Goudsmit-Saunderson agnular distributions based on a DCS accounting spin
81 // effects and screening correction 81 // effects and screening corrections. The DCS used to compute the accurate
82 // GS angular distributions is: DCS 82 // GS angular distributions is: DCS_{cor} = DCS_{SR}x[ DCS_{R}/DCS_{Mott}] where :
83 // # DCS_{SR} is the relativisti 83 // # DCS_{SR} is the relativistic Screened-Rutherford DCS (first Born approximate
84 // solution of the Klein-Gordo 84 // solution of the Klein-Gordon i.e. relativistic Schrodinger equation =>
85 // scattering of spinless e- o 85 // scattering of spinless e- on exponentially screened Coulomb potential)
86 // note: the default (without 86 // note: the default (without using Mott-correction) GS angular distributions
87 // are based on this DCS_{SR} 87 // are based on this DCS_{SR} with Moliere's screening parameter!
88 // # DCS_{R} is the Rutherford D 88 // # DCS_{R} is the Rutherford DCS which is the same as above but without
89 // screening 89 // screening
90 // # DCS_{Mott} is the Mott DCS 90 // # DCS_{Mott} is the Mott DCS i.e. solution of the Dirac equation with a bare
91 // Coulomb potential i.e. scat 91 // Coulomb potential i.e. scattering of particles with spin (e- or e+) on a
92 // point-like unscreened Coulo 92 // point-like unscreened Coulomb potential
93 // # moreover, the screening par 93 // # moreover, the screening parameter of the DCS_{cor} was determined such that
94 // the DCS_{cor} with this cor 94 // the DCS_{cor} with this corrected screening parameter reproduce the first
95 // transport cross sections ob 95 // transport cross sections obtained from the corresponding most accurate DCS
96 // (i.e. from elsepa [4]) 96 // (i.e. from elsepa [4])
97 // Unlike the default GS, the Mott- 97 // Unlike the default GS, the Mott-corrected angular distributions are particle type
98 // (different for e- and e+ <= the 98 // (different for e- and e+ <= the DCS_{Mott} and the screening correction) and target
99 // (Z and material) dependent. 99 // (Z and material) dependent.
100 // 27.10.2017 M. Novak: 100 // 27.10.2017 M. Novak:
101 // - Mott-correction flag is set no 101 // - Mott-correction flag is set now through the G4EmParameters
102 // - new form of PWA correction to 102 // - new form of PWA correction to integrated quantities and screening (default)
103 // - changed step limit flag conven 103 // - changed step limit flag conventions:
104 // # fUseSafety corresponds to U 104 // # fUseSafety corresponds to Urban's fUseSafety
105 // # fUseDistanceToBoundary corr 105 // # fUseDistanceToBoundary corresponds to Urban's fUseDistanceToBoundary
106 // # fUseSafetyPlus corresponds 106 // # fUseSafetyPlus corresponds to the error-free stepping algorithm
107 // 02.02.2018 M. Novak: implemented CrossSecti 107 // 02.02.2018 M. Novak: implemented CrossSectionPerVolume interface method (used only for testing)
108 // 108 //
109 // Class description: 109 // Class description:
110 // Kawrakow-Bielajew Goudsmit-Saunderson MSC 110 // Kawrakow-Bielajew Goudsmit-Saunderson MSC model based on the screened Rutherford DCS
111 // for elastic scattering of e-/e+. Option, 111 // for elastic scattering of e-/e+. Option, to include (Mott) correction (see above), is
112 // also available now (SetOptionMottCorrecti 112 // also available now (SetOptionMottCorrection(true)). An EGSnrc like error-free stepping
113 // algorithm (UseSafety) is available beyond 113 // algorithm (UseSafety) is available beyond the usual Geant4 step limitation algorithms
114 // and true to geomerty and geometry to true 114 // and true to geomerty and geometry to true step length computations that were adopted
115 // from the Urban model[5]. The most accurat 115 // from the Urban model[5]. The most accurate setting: error-free stepping i.e. the
116 // UseSafetyPlus MSC step limit with Mott-co 116 // UseSafetyPlus MSC step limit with Mott-correction (SetOptionMottCorrection(true)). Both
117 // are expected to be set through the G4EmPa 117 // are expected to be set through the G4EmParameters singleton before initialisation:
118 // # G4EmParameters::Instance()->SetMscStep 118 // # G4EmParameters::Instance()->SetMscStepLimitType(fUseSafetyPlus);
119 // # G4EmParameters::Instance()->SetUseMott 119 // # G4EmParameters::Instance()->SetUseMottCorrection(true);
120 // 120 //
121 // 121 //
122 // References: 122 // References:
123 // [1] A.F.Bielajew, NIMB 111 (1996) 195-208 123 // [1] A.F.Bielajew, NIMB 111 (1996) 195-208
124 // [2] I.Kawrakow, A.F.Bielajew, NIMB 134(19 124 // [2] I.Kawrakow, A.F.Bielajew, NIMB 134(1998) 325-336
125 // [3] I.Kawrakow, E.Mainegra-Hing, D.W.O.Ro 125 // [3] I.Kawrakow, E.Mainegra-Hing, D.W.O.Rogers, F.Tessier,B.R.B.Walters, NRCC
126 // Report PIRS-701 (2013) 126 // Report PIRS-701 (2013)
127 // [4] F.Salvat, A.Jablonski, C.J. Powell, C 127 // [4] F.Salvat, A.Jablonski, C.J. Powell, CPC 165(2005) 157-190
128 // [5] L.Urban, Preprint CERN-OPEN-2006-077 128 // [5] L.Urban, Preprint CERN-OPEN-2006-077 (2006)
129 // 129 //
130 // ------------------------------------------- 130 // -----------------------------------------------------------------------------
131 131
132 132
133 #include "G4GoudsmitSaundersonMscModel.hh" 133 #include "G4GoudsmitSaundersonMscModel.hh"
134 134
135 #include "G4GoudsmitSaundersonTable.hh" 135 #include "G4GoudsmitSaundersonTable.hh"
136 #include "G4GSPWACorrections.hh" 136 #include "G4GSPWACorrections.hh"
137 137
138 #include "G4PhysicalConstants.hh" 138 #include "G4PhysicalConstants.hh"
139 #include "G4SystemOfUnits.hh" 139 #include "G4SystemOfUnits.hh"
140 140
141 #include "G4ParticleChangeForMSC.hh" 141 #include "G4ParticleChangeForMSC.hh"
142 #include "G4DynamicParticle.hh" 142 #include "G4DynamicParticle.hh"
143 #include "G4Electron.hh" 143 #include "G4Electron.hh"
144 #include "G4Positron.hh" 144 #include "G4Positron.hh"
145 145
146 #include "G4LossTableManager.hh" 146 #include "G4LossTableManager.hh"
147 #include "G4EmParameters.hh" 147 #include "G4EmParameters.hh"
148 #include "G4Track.hh" 148 #include "G4Track.hh"
149 #include "G4PhysicsTable.hh" 149 #include "G4PhysicsTable.hh"
150 #include "Randomize.hh" 150 #include "Randomize.hh"
151 #include "G4Log.hh" 151 #include "G4Log.hh"
152 #include "G4Exp.hh" 152 #include "G4Exp.hh"
153 #include "G4Pow.hh" 153 #include "G4Pow.hh"
154 #include <fstream> 154 #include <fstream>
155 155
156 156
157 // set accurate energy loss and dispalcement s 157 // set accurate energy loss and dispalcement sampling to be always on now
158 G4bool G4GoudsmitSaundersonMscModel::gIsUseAcc 158 G4bool G4GoudsmitSaundersonMscModel::gIsUseAccurate = true;
159 // set the usual optimization to be always act 159 // set the usual optimization to be always active now
160 G4bool G4GoudsmitSaundersonMscModel::gIsOptimi 160 G4bool G4GoudsmitSaundersonMscModel::gIsOptimizationOn = true;
161 161
162 162
163 G4GoudsmitSaundersonMscModel::G4GoudsmitSaunde 163 G4GoudsmitSaundersonMscModel::G4GoudsmitSaundersonMscModel(const G4String& nam)
164 : G4VMscModel(nam) { 164 : G4VMscModel(nam) {
165 charge = 0; 165 charge = 0;
166 currentMaterialIndex = -1; 166 currentMaterialIndex = -1;
167 // 167 //
>> 168 lambdalimit = 1.*mm;
168 fr = 0.1; 169 fr = 0.1;
169 rangeinit = 1.e+21; 170 rangeinit = 1.e+21;
170 geombig = 1.e+50*mm; 171 geombig = 1.e+50*mm;
171 geomlimit = geombig; 172 geomlimit = geombig;
172 tgeom = geombig; 173 tgeom = geombig;
173 tlimit = 1.e+10*mm; 174 tlimit = 1.e+10*mm;
174 presafety = 0.*mm; 175 presafety = 0.*mm;
175 // 176 //
176 particle = nullptr; << 177 particle = 0;
177 theManager = G4LossTableManager: 178 theManager = G4LossTableManager::Instance();
178 firstStep = true; 179 firstStep = true;
179 currentKinEnergy = 0.0; 180 currentKinEnergy = 0.0;
180 currentRange = 0.0; 181 currentRange = 0.0;
181 // 182 //
182 tlimitminfix2 = 1.*nm; 183 tlimitminfix2 = 1.*nm;
183 tausmall = 1.e-16; 184 tausmall = 1.e-16;
184 mass = electron_mass_c2; 185 mass = electron_mass_c2;
185 taulim = 1.e-6; 186 taulim = 1.e-6;
186 // 187 //
>> 188 facsafety = 0.6;
>> 189
187 currentCouple = nullptr; 190 currentCouple = nullptr;
188 fParticleChange = nullptr; 191 fParticleChange = nullptr;
189 // 192 //
190 fZeff = 1.; 193 fZeff = 1.;
191 // 194 //
192 par1 = 0.; 195 par1 = 0.;
193 par2 = 0.; 196 par2 = 0.;
194 par3 = 0.; 197 par3 = 0.;
195 // 198 //
196 // Moliere screeing parameter will be used a 199 // Moliere screeing parameter will be used and (by default) corrections are
197 // appalied to the integrated quantities (sc 200 // appalied to the integrated quantities (screeing parameter, elastic mfp, first
198 // and second moments) derived from the corr 201 // and second moments) derived from the corresponding PWA quantities
199 // this PWA correction is ignored if Mott-co 202 // this PWA correction is ignored if Mott-correction is set to true because
200 // Mott-correction contains all these correc 203 // Mott-correction contains all these corrections as well
201 fIsUsePWACorrection = true; 204 fIsUsePWACorrection = true;
202 // 205 //
203 fIsUseMottCorrection = false; 206 fIsUseMottCorrection = false;
204 // 207 //
205 fLambda0 = 0.0; // elastic mea 208 fLambda0 = 0.0; // elastic mean free path
206 fLambda1 = 0.0; // first trans 209 fLambda1 = 0.0; // first transport mean free path
207 fScrA = 0.0; // screening p 210 fScrA = 0.0; // screening parameter
208 fG1 = 0.0; // first trans 211 fG1 = 0.0; // first transport coef.
209 // 212 //
210 fMCtoScrA = 1.0; 213 fMCtoScrA = 1.0;
211 fMCtoQ1 = 1.0; 214 fMCtoQ1 = 1.0;
212 fMCtoG2PerG1 = 1.0; 215 fMCtoG2PerG1 = 1.0;
213 // 216 //
214 fTheTrueStepLenght = 0.; 217 fTheTrueStepLenght = 0.;
215 fTheTransportDistance = 0.; 218 fTheTransportDistance = 0.;
216 fTheZPathLenght = 0.; 219 fTheZPathLenght = 0.;
217 // 220 //
218 fTheDisplacementVector.set(0.,0.,0.); 221 fTheDisplacementVector.set(0.,0.,0.);
219 fTheNewDirection.set(0.,0.,1.); 222 fTheNewDirection.set(0.,0.,1.);
220 // 223 //
221 fIsEverythingWasDone = false; 224 fIsEverythingWasDone = false;
222 fIsMultipleSacettring = false; 225 fIsMultipleSacettring = false;
223 fIsSingleScattering = false; 226 fIsSingleScattering = false;
224 fIsEndedUpOnBoundary = false; 227 fIsEndedUpOnBoundary = false;
225 fIsNoScatteringInMSC = false; 228 fIsNoScatteringInMSC = false;
226 fIsNoDisplace = false; 229 fIsNoDisplace = false;
227 fIsInsideSkin = false; 230 fIsInsideSkin = false;
228 fIsWasOnBoundary = false; 231 fIsWasOnBoundary = false;
229 fIsFirstRealStep = false; 232 fIsFirstRealStep = false;
230 rndmEngineMod = G4Random::getTheEng 233 rndmEngineMod = G4Random::getTheEngine();
231 // 234 //
232 fGSTable = nullptr; 235 fGSTable = nullptr;
233 fPWACorrection = nullptr; 236 fPWACorrection = nullptr;
234 } 237 }
235 238
236 239
237 G4GoudsmitSaundersonMscModel::~G4GoudsmitSaund 240 G4GoudsmitSaundersonMscModel::~G4GoudsmitSaundersonMscModel() {
238 if (IsMaster()) { 241 if (IsMaster()) {
239 if (fGSTable) { 242 if (fGSTable) {
240 delete fGSTable; 243 delete fGSTable;
241 fGSTable = nullptr; 244 fGSTable = nullptr;
242 } 245 }
243 if (fPWACorrection) { 246 if (fPWACorrection) {
244 delete fPWACorrection; 247 delete fPWACorrection;
245 fPWACorrection = nullptr; 248 fPWACorrection = nullptr;
246 } 249 }
247 } 250 }
248 } 251 }
249 252
250 253
251 void G4GoudsmitSaundersonMscModel::Initialise( 254 void G4GoudsmitSaundersonMscModel::Initialise(const G4ParticleDefinition* p, const G4DataVector&) {
252 SetParticle(p); 255 SetParticle(p);
253 InitialiseParameters(p); <<
254 // -create GoudsmitSaundersonTable and init 256 // -create GoudsmitSaundersonTable and init its Mott-correction member if
255 // Mott-correction was required 257 // Mott-correction was required
256 if (IsMaster()) { 258 if (IsMaster()) {
257 // get the Mott-correction flag from EmPar 259 // get the Mott-correction flag from EmParameters
258 if (G4EmParameters::Instance()->UseMottCor 260 if (G4EmParameters::Instance()->UseMottCorrection()) {
259 fIsUseMottCorrection = true; 261 fIsUseMottCorrection = true;
260 } 262 }
261 // Mott-correction includes other way of P 263 // Mott-correction includes other way of PWA x-section corrections so deactivate it even if it was true
262 // when Mott-correction is activated by th 264 // when Mott-correction is activated by the user
263 if (fIsUseMottCorrection) { 265 if (fIsUseMottCorrection) {
264 fIsUsePWACorrection = false; 266 fIsUsePWACorrection = false;
265 } 267 }
266 // clear GS-table 268 // clear GS-table
267 if (fGSTable) { 269 if (fGSTable) {
268 delete fGSTable; 270 delete fGSTable;
269 fGSTable = nullptr; 271 fGSTable = nullptr;
270 } 272 }
271 // clear PWA corrections table if any 273 // clear PWA corrections table if any
272 if (fPWACorrection) { 274 if (fPWACorrection) {
273 delete fPWACorrection; 275 delete fPWACorrection;
274 fPWACorrection = nullptr; 276 fPWACorrection = nullptr;
275 } 277 }
276 // create GS-table 278 // create GS-table
277 G4bool isElectron = true; 279 G4bool isElectron = true;
278 if (p->GetPDGCharge()>0.) { 280 if (p->GetPDGCharge()>0.) {
279 isElectron = false; 281 isElectron = false;
280 } 282 }
281 fGSTable = new G4GoudsmitSaundersonTable(i 283 fGSTable = new G4GoudsmitSaundersonTable(isElectron);
282 // G4GSTable will be initialised: 284 // G4GSTable will be initialised:
283 // - Screened-Rutherford DCS based GS angu 285 // - Screened-Rutherford DCS based GS angular distributions will be loaded only if they are not there yet
284 // - Mott-correction will be initialised i 286 // - Mott-correction will be initialised if Mott-correction was requested to be used
285 fGSTable->SetOptionMottCorrection(fIsUseMo 287 fGSTable->SetOptionMottCorrection(fIsUseMottCorrection);
286 // - set PWA correction (correction to int 288 // - set PWA correction (correction to integrated quantites from Dirac-PWA)
287 fGSTable->SetOptionPWACorrection(fIsUsePWA 289 fGSTable->SetOptionPWACorrection(fIsUsePWACorrection);
288 // init 290 // init
289 fGSTable->Initialise(LowEnergyLimit(),High 291 fGSTable->Initialise(LowEnergyLimit(),HighEnergyLimit());
290 // create PWA corrections table if it was 292 // create PWA corrections table if it was requested (and not disactivated because active Mott-correction)
291 if (fIsUsePWACorrection) { 293 if (fIsUsePWACorrection) {
292 fPWACorrection = new G4GSPWACorrections( 294 fPWACorrection = new G4GSPWACorrections(isElectron);
293 fPWACorrection->Initialise(); 295 fPWACorrection->Initialise();
294 } 296 }
295 } 297 }
296 fParticleChange = GetParticleChangeForMSC(p) 298 fParticleChange = GetParticleChangeForMSC(p);
297 } 299 }
298 300
299 301
300 void G4GoudsmitSaundersonMscModel::InitialiseL 302 void G4GoudsmitSaundersonMscModel::InitialiseLocal(const G4ParticleDefinition*, G4VEmModel* masterModel) {
301 fGSTable = static_cast<G4Goud 303 fGSTable = static_cast<G4GoudsmitSaundersonMscModel*>(masterModel)->GetGSTable();
302 fIsUseMottCorrection = static_cast<G4Goud 304 fIsUseMottCorrection = static_cast<G4GoudsmitSaundersonMscModel*>(masterModel)->GetOptionMottCorrection();
303 fIsUsePWACorrection = static_cast<G4Goud 305 fIsUsePWACorrection = static_cast<G4GoudsmitSaundersonMscModel*>(masterModel)->GetOptionPWACorrection();
304 fPWACorrection = static_cast<G4Goud 306 fPWACorrection = static_cast<G4GoudsmitSaundersonMscModel*>(masterModel)->GetPWACorrection();
305 } 307 }
306 308
307 309
308 // computes macroscopic first transport cross 310 // computes macroscopic first transport cross section: used only in testing not during mc transport
309 G4double G4GoudsmitSaundersonMscModel::CrossSe 311 G4double G4GoudsmitSaundersonMscModel::CrossSectionPerVolume(const G4Material* mat,
310 const 312 const G4ParticleDefinition*,
311 G4dou 313 G4double kineticEnergy,
312 G4dou 314 G4double,
313 G4dou 315 G4double) {
314 G4double xsecTr1 = 0.; // cross section per 316 G4double xsecTr1 = 0.; // cross section per volume i.e. macroscopic 1st transport cross section
>> 317 G4double efEnergy = kineticEnergy;
315 // 318 //
316 fLambda0 = 0.0; // elastic mean free path 319 fLambda0 = 0.0; // elastic mean free path
317 fLambda1 = 0.0; // first transport mean free 320 fLambda1 = 0.0; // first transport mean free path
318 fScrA = 0.0; // screening parameter 321 fScrA = 0.0; // screening parameter
319 fG1 = 0.0; // first transport coef. 322 fG1 = 0.0; // first transport coef.
320 // use Moliere's screening (with Mott-corret 323 // use Moliere's screening (with Mott-corretion if it was requested)
321 G4double efEnergy = std::max(kineticEnergy, << 324 if (efEnergy<10.*CLHEP::eV) efEnergy = 10.*CLHEP::eV;
322 // total mometum square 325 // total mometum square
323 G4double pt2 = efEnergy*(efEnergy+2.0*el 326 G4double pt2 = efEnergy*(efEnergy+2.0*electron_mass_c2);
324 // beta square 327 // beta square
325 G4double beta2 = pt2/(pt2+electron_mass_c2 328 G4double beta2 = pt2/(pt2+electron_mass_c2*electron_mass_c2);
326 // current material index 329 // current material index
327 G4int matindx = (G4int)mat->GetIndex(); << 330 G4int matindx = mat->GetIndex();
328 // Moliere's b_c 331 // Moliere's b_c
329 G4double bc = fGSTable->GetMoliereBc(ma 332 G4double bc = fGSTable->GetMoliereBc(matindx);
330 // get the Mott-correcton factors if Mott-co 333 // get the Mott-correcton factors if Mott-correcton was requested by the user
331 fMCtoScrA = 1.0; 334 fMCtoScrA = 1.0;
332 fMCtoQ1 = 1.0; 335 fMCtoQ1 = 1.0;
333 fMCtoG2PerG1 = 1.0; 336 fMCtoG2PerG1 = 1.0;
334 G4double scpCor = 1.0; 337 G4double scpCor = 1.0;
335 if (fIsUseMottCorrection) { 338 if (fIsUseMottCorrection) {
336 fGSTable->GetMottCorrectionFactors(G4Log(e 339 fGSTable->GetMottCorrectionFactors(G4Log(efEnergy), beta2, matindx, fMCtoScrA, fMCtoQ1, fMCtoG2PerG1);
337 // ! no scattering power correction since 340 // ! no scattering power correction since the current couple is not set before this interface method is called
338 // scpCor = fGSTable->ComputeScatteringPow 341 // scpCor = fGSTable->ComputeScatteringPowerCorrection(currentCouple, efEnergy);
339 } else if (fIsUsePWACorrection) { 342 } else if (fIsUsePWACorrection) {
340 fPWACorrection->GetPWACorrectionFactors(G4 343 fPWACorrection->GetPWACorrectionFactors(G4Log(efEnergy), beta2, matindx, fMCtoScrA, fMCtoQ1, fMCtoG2PerG1);
341 // scpCor = fGSTable->ComputeScatteringPow 344 // scpCor = fGSTable->ComputeScatteringPowerCorrection(currentCouple, efEnergy);
342 } 345 }
343 // screening parameter: 346 // screening parameter:
344 // - if Mott-corretioncorrection: the Screen 347 // - if Mott-corretioncorrection: the Screened-Rutherford times Mott-corretion DCS with this
345 // screening parameter gives back the (els 348 // screening parameter gives back the (elsepa) PWA first transport cross section
346 // - if PWA correction: he Screened-Rutherfo 349 // - if PWA correction: he Screened-Rutherford DCS with this screening parameter
347 // gives back the (elsepa) PWA first trans 350 // gives back the (elsepa) PWA first transport cross section
348 fScrA = fGSTable->GetMoliereXc2(matindx)/ 351 fScrA = fGSTable->GetMoliereXc2(matindx)/(4.0*pt2*bc)*fMCtoScrA;
349 // elastic mean free path in Geant4 internal 352 // elastic mean free path in Geant4 internal lenght units: the neglected (1+screening parameter) term is corrected
350 // (if Mott-corretion: the corrected screeni 353 // (if Mott-corretion: the corrected screening parameter is used for this (1+A) correction + Moliere b_c is also
351 // corrected with the screening parameter co 354 // corrected with the screening parameter correction)
352 fLambda0 = beta2*(1.+fScrA)*fMCtoScrA/bc/scp 355 fLambda0 = beta2*(1.+fScrA)*fMCtoScrA/bc/scpCor;
353 // first transport coefficient (if Mott-corr 356 // first transport coefficient (if Mott-corretion: the corrected screening parameter is used (it will be fully
354 // consistent with the one used during the p 357 // consistent with the one used during the pre-computation of the Mott-correted GS angular distributions))
355 fG1 = 2.0*fScrA*((1.0+fScrA)*G4Log(1.0/ 358 fG1 = 2.0*fScrA*((1.0+fScrA)*G4Log(1.0/fScrA+1.0)-1.0);
356 // first transport mean free path 359 // first transport mean free path
357 fLambda1 = fLambda0/fG1; 360 fLambda1 = fLambda0/fG1;
358 xsecTr1 = 1./fLambda1; 361 xsecTr1 = 1./fLambda1;
359 return xsecTr1; 362 return xsecTr1;
360 } 363 }
361 364
362 365
363 // gives back the first transport mean free pa 366 // gives back the first transport mean free path in internal G4 units
364 G4double 367 G4double
365 G4GoudsmitSaundersonMscModel::GetTransportMean 368 G4GoudsmitSaundersonMscModel::GetTransportMeanFreePath(const G4ParticleDefinition* /*partdef*/,
366 369 G4double kineticEnergy) {
367 // kinetic energy is assumed to be in Geant4 370 // kinetic energy is assumed to be in Geant4 internal energy unit which is MeV
368 G4double efEnergy = kineticEnergy; 371 G4double efEnergy = kineticEnergy;
369 // 372 //
370 const G4Material* mat = currentCouple->GetM 373 const G4Material* mat = currentCouple->GetMaterial();
371 // 374 //
372 fLambda0 = 0.0; // elastic mean free path 375 fLambda0 = 0.0; // elastic mean free path
373 fLambda1 = 0.0; // first transport mean free 376 fLambda1 = 0.0; // first transport mean free path
374 fScrA = 0.0; // screening parameter 377 fScrA = 0.0; // screening parameter
375 fG1 = 0.0; // first transport coef. 378 fG1 = 0.0; // first transport coef.
376 379
377 // use Moliere's screening (with Mott-corret 380 // use Moliere's screening (with Mott-corretion if it was requested)
378 if (efEnergy<10.*CLHEP::eV) efEnergy = 10.* 381 if (efEnergy<10.*CLHEP::eV) efEnergy = 10.*CLHEP::eV;
379 // total mometum square 382 // total mometum square
380 G4double pt2 = efEnergy*(efEnergy+2.0*el 383 G4double pt2 = efEnergy*(efEnergy+2.0*electron_mass_c2);
381 // beta square 384 // beta square
382 G4double beta2 = pt2/(pt2+electron_mass_c2 385 G4double beta2 = pt2/(pt2+electron_mass_c2*electron_mass_c2);
383 // current material index 386 // current material index
384 G4int matindx = (G4int)mat->GetIndex(); << 387 G4int matindx = mat->GetIndex();
385 // Moliere's b_c 388 // Moliere's b_c
386 G4double bc = fGSTable->GetMoliereBc(ma 389 G4double bc = fGSTable->GetMoliereBc(matindx);
387 // get the Mott-correcton factors if Mott-co 390 // get the Mott-correcton factors if Mott-correcton was requested by the user
388 fMCtoScrA = 1.0; 391 fMCtoScrA = 1.0;
389 fMCtoQ1 = 1.0; 392 fMCtoQ1 = 1.0;
390 fMCtoG2PerG1 = 1.0; 393 fMCtoG2PerG1 = 1.0;
391 G4double scpCor = 1.0; 394 G4double scpCor = 1.0;
392 if (fIsUseMottCorrection) { 395 if (fIsUseMottCorrection) {
393 fGSTable->GetMottCorrectionFactors(G4Log(e 396 fGSTable->GetMottCorrectionFactors(G4Log(efEnergy), beta2, matindx, fMCtoScrA, fMCtoQ1, fMCtoG2PerG1);
394 scpCor = fGSTable->ComputeScatteringPowerC 397 scpCor = fGSTable->ComputeScatteringPowerCorrection(currentCouple, efEnergy);
395 } else if (fIsUsePWACorrection) { 398 } else if (fIsUsePWACorrection) {
396 fPWACorrection->GetPWACorrectionFactors(G4 399 fPWACorrection->GetPWACorrectionFactors(G4Log(efEnergy), beta2, matindx, fMCtoScrA, fMCtoQ1, fMCtoG2PerG1);
397 // scpCor = fGSTable->ComputeScatteringPow 400 // scpCor = fGSTable->ComputeScatteringPowerCorrection(currentCouple, efEnergy);
398 } 401 }
399 // screening parameter: 402 // screening parameter:
400 // - if Mott-corretioncorrection: the Screen 403 // - if Mott-corretioncorrection: the Screened-Rutherford times Mott-corretion DCS with this
401 // screening parameter gives back the (els 404 // screening parameter gives back the (elsepa) PWA first transport cross section
402 // - if PWA correction: he Screened-Rutherfo 405 // - if PWA correction: he Screened-Rutherford DCS with this screening parameter
403 // gives back the (elsepa) PWA first trans 406 // gives back the (elsepa) PWA first transport cross section
404 fScrA = fGSTable->GetMoliereXc2(matindx)/ 407 fScrA = fGSTable->GetMoliereXc2(matindx)/(4.0*pt2*bc)*fMCtoScrA;
405 // elastic mean free path in Geant4 internal 408 // elastic mean free path in Geant4 internal lenght units: the neglected (1+screening parameter) term is corrected
406 // (if Mott-corretion: the corrected screeni 409 // (if Mott-corretion: the corrected screening parameter is used for this (1+A) correction + Moliere b_c is also
407 // corrected with the screening parameter co 410 // corrected with the screening parameter correction)
408 fLambda0 = beta2*(1.+fScrA)*fMCtoScrA/bc/scp 411 fLambda0 = beta2*(1.+fScrA)*fMCtoScrA/bc/scpCor;
409 // first transport coefficient (if Mott-corr 412 // first transport coefficient (if Mott-corretion: the corrected screening parameter is used (it will be fully
410 // consistent with the one used during the p 413 // consistent with the one used during the pre-computation of the Mott-correted GS angular distributions))
411 fG1 = 2.0*fScrA*((1.0+fScrA)*G4Log(1.0/ 414 fG1 = 2.0*fScrA*((1.0+fScrA)*G4Log(1.0/fScrA+1.0)-1.0);
412 // first transport mean free path 415 // first transport mean free path
413 fLambda1 = fLambda0/fG1; 416 fLambda1 = fLambda0/fG1;
414 417
415 return fLambda1; 418 return fLambda1;
416 } 419 }
417 420
418 421
419 G4double 422 G4double
420 G4GoudsmitSaundersonMscModel::GetTransportMean 423 G4GoudsmitSaundersonMscModel::GetTransportMeanFreePathOnly(const G4ParticleDefinition* /*partdef*/,
421 424 G4double kineticEnergy) {
422 // kinetic energy is assumed to be in Geant4 425 // kinetic energy is assumed to be in Geant4 internal energy unit which is MeV
423 G4double efEnergy = kineticEnergy; 426 G4double efEnergy = kineticEnergy;
424 // 427 //
425 const G4Material* mat = currentCouple->GetM 428 const G4Material* mat = currentCouple->GetMaterial();
426 // 429 //
427 G4double lambda0 = 0.0; // elastc mean free 430 G4double lambda0 = 0.0; // elastc mean free path
428 G4double lambda1 = 0.0; // first transport m 431 G4double lambda1 = 0.0; // first transport mean free path
429 G4double scrA = 0.0; // screening paramet 432 G4double scrA = 0.0; // screening parametr
430 G4double g1 = 0.0; // first transport m 433 G4double g1 = 0.0; // first transport mean free path
431 434
432 // use Moliere's screening (with Mott-corret 435 // use Moliere's screening (with Mott-corretion if it was requested)
433 if (efEnergy<10.*CLHEP::eV) efEnergy = 10.* 436 if (efEnergy<10.*CLHEP::eV) efEnergy = 10.*CLHEP::eV;
434 // total mometum square in Geant4 internal e 437 // total mometum square in Geant4 internal energy2 units which is MeV2
435 G4double pt2 = efEnergy*(efEnergy+2.0*el 438 G4double pt2 = efEnergy*(efEnergy+2.0*electron_mass_c2);
436 G4double beta2 = pt2/(pt2+electron_mass_c2 439 G4double beta2 = pt2/(pt2+electron_mass_c2*electron_mass_c2);
437 G4int matindx = (G4int)mat->GetIndex(); << 440 G4int matindx = mat->GetIndex();
438 G4double bc = fGSTable->GetMoliereBc(ma 441 G4double bc = fGSTable->GetMoliereBc(matindx);
439 // get the Mott-correcton factors if Mott-co 442 // get the Mott-correcton factors if Mott-correcton was requested by the user
440 G4double mctoScrA = 1.0; 443 G4double mctoScrA = 1.0;
441 G4double mctoQ1 = 1.0; 444 G4double mctoQ1 = 1.0;
442 G4double mctoG2PerG1 = 1.0; 445 G4double mctoG2PerG1 = 1.0;
443 G4double scpCor = 1.0; 446 G4double scpCor = 1.0;
444 if (fIsUseMottCorrection) { 447 if (fIsUseMottCorrection) {
445 fGSTable->GetMottCorrectionFactors(G4Log(e 448 fGSTable->GetMottCorrectionFactors(G4Log(efEnergy), beta2, matindx, mctoScrA, mctoQ1, mctoG2PerG1);
446 scpCor = fGSTable->ComputeScatteringPowerC 449 scpCor = fGSTable->ComputeScatteringPowerCorrection(currentCouple, efEnergy);
447 } else if (fIsUsePWACorrection) { 450 } else if (fIsUsePWACorrection) {
448 fPWACorrection->GetPWACorrectionFactors(G4 451 fPWACorrection->GetPWACorrectionFactors(G4Log(efEnergy), beta2, matindx, mctoScrA, mctoQ1, mctoG2PerG1);
449 // scpCor = fGSTable->ComputeScatteringPow 452 // scpCor = fGSTable->ComputeScatteringPowerCorrection(currentCouple, efEnergy);
450 } 453 }
451 scrA = fGSTable->GetMoliereXc2(matindx)/( 454 scrA = fGSTable->GetMoliereXc2(matindx)/(4.0*pt2*bc)*mctoScrA;
452 // total elastic mean free path in Geant4 in 455 // total elastic mean free path in Geant4 internal lenght units
453 lambda0 = beta2*(1.+scrA)*mctoScrA/bc/scpCor 456 lambda0 = beta2*(1.+scrA)*mctoScrA/bc/scpCor;
454 g1 = 2.0*scrA*((1.0+scrA)*G4Log(1.0/scr 457 g1 = 2.0*scrA*((1.0+scrA)*G4Log(1.0/scrA+1.0)-1.0);
455 lambda1 = lambda0/g1; 458 lambda1 = lambda0/g1;
456 459
457 return lambda1; 460 return lambda1;
458 } 461 }
459 462
460 463
461 void G4GoudsmitSaundersonMscModel::StartTracki 464 void G4GoudsmitSaundersonMscModel::StartTracking(G4Track* track) {
462 SetParticle(track->GetDynamicParticle()->Get 465 SetParticle(track->GetDynamicParticle()->GetDefinition());
463 firstStep = true; 466 firstStep = true;
464 tlimit = tgeom = rangeinit = geombig; 467 tlimit = tgeom = rangeinit = geombig;
465 rangeinit = 1.e+21; 468 rangeinit = 1.e+21;
466 } 469 }
467 470
468 471
469 G4double G4GoudsmitSaundersonMscModel::Compute 472 G4double G4GoudsmitSaundersonMscModel::ComputeTruePathLengthLimit(const G4Track& track,
470 473 G4double& currentMinimalStep) {
471 G4double skindepth = 0.; 474 G4double skindepth = 0.;
472 // 475 //
473 const G4DynamicParticle* dp = track.GetDynam 476 const G4DynamicParticle* dp = track.GetDynamicParticle();
474 G4StepPoint* sp = track.GetStep( 477 G4StepPoint* sp = track.GetStep()->GetPreStepPoint();
475 G4StepStatus stepStatus = sp->GetStepSta 478 G4StepStatus stepStatus = sp->GetStepStatus();
476 currentCouple = track.GetMater 479 currentCouple = track.GetMaterialCutsCouple();
477 SetCurrentCouple(currentCouple); 480 SetCurrentCouple(currentCouple);
478 currentMaterialIndex = (G4int)current << 481 currentMaterialIndex = currentCouple->GetMaterial()->GetIndex();
479 currentKinEnergy = dp->GetKinetic 482 currentKinEnergy = dp->GetKineticEnergy();
480 currentRange = GetRange(parti << 483 currentRange = GetRange(particle,currentKinEnergy,currentCouple);
481 dp->G <<
482 // elastic and first transport mfp, screenin 484 // elastic and first transport mfp, screening parameter and G1 are also set
483 // (Mott-correction will be used if it was r 485 // (Mott-correction will be used if it was requested by the user)
484 fLambda1 = GetTransportMeanFreePath(particle 486 fLambda1 = GetTransportMeanFreePath(particle,currentKinEnergy);
485 // Set initial values: 487 // Set initial values:
486 // : lengths are initialised to currentMini 488 // : lengths are initialised to currentMinimalStep which is the true, minimum
487 // step length from all other physics 489 // step length from all other physics
488 fTheTrueStepLenght = currentMinimalStep; 490 fTheTrueStepLenght = currentMinimalStep;
489 fTheTransportDistance = currentMinimalStep; 491 fTheTransportDistance = currentMinimalStep;
490 fTheZPathLenght = currentMinimalStep; 492 fTheZPathLenght = currentMinimalStep; // will need to be converted
491 fTheDisplacementVector.set(0.,0.,0.); 493 fTheDisplacementVector.set(0.,0.,0.);
492 fTheNewDirection.set(0.,0.,1.); 494 fTheNewDirection.set(0.,0.,1.);
493 495
494 // Can everything be done in the step limit 496 // Can everything be done in the step limit phase ?
495 fIsEverythingWasDone = false; 497 fIsEverythingWasDone = false;
496 // Multiple scattering needs to be sample ? 498 // Multiple scattering needs to be sample ?
497 fIsMultipleSacettring = false; 499 fIsMultipleSacettring = false;
498 // Single scattering needs to be sample ? 500 // Single scattering needs to be sample ?
499 fIsSingleScattering = false; 501 fIsSingleScattering = false;
500 // Was zero deflection in multiple scatterin 502 // Was zero deflection in multiple scattering sampling ?
501 fIsNoScatteringInMSC = false; 503 fIsNoScatteringInMSC = false;
502 // Do not care about displacement in MSC sam 504 // Do not care about displacement in MSC sampling
503 // ( used only in the case of gIsOptimizatio 505 // ( used only in the case of gIsOptimizationOn = true)
504 fIsNoDisplace = false; 506 fIsNoDisplace = false;
505 // get pre-step point safety 507 // get pre-step point safety
506 presafety = sp->GetSafety(); 508 presafety = sp->GetSafety();
507 // 509 //
508 fZeff = currentCouple->GetMaterial()->GetIon 510 fZeff = currentCouple->GetMaterial()->GetIonisation()->GetZeffective();
509 // distance will take into account max-fluct 511 // distance will take into account max-fluct.
510 G4double distance = currentRange; 512 G4double distance = currentRange;
511 distance *= (1.20-fZeff*(1.62e-2-9.22e-5*fZe 513 distance *= (1.20-fZeff*(1.62e-2-9.22e-5*fZeff));
512 // 514 //
513 // Possible optimization : if the distance i 515 // Possible optimization : if the distance is samller than the safety -> the
514 // particle will never leave this volume -> 516 // particle will never leave this volume -> dispalcement
515 // as the effect of multiple elastic scatter 517 // as the effect of multiple elastic scattering can be skipped
516 // Important : this optimization can cause p 518 // Important : this optimization can cause problems if one does scoring
517 // in a bigger volume since MSC won't be don 519 // in a bigger volume since MSC won't be done deep inside the volume when
518 // distance < safety so don't use optimized- 520 // distance < safety so don't use optimized-mode in such case.
519 if (gIsOptimizationOn && (distance<presafety 521 if (gIsOptimizationOn && (distance<presafety)) {
520 // Indicate that we need to do MSC after 522 // Indicate that we need to do MSC after transportation and no dispalcement.
521 fIsMultipleSacettring = true; 523 fIsMultipleSacettring = true;
522 fIsNoDisplace = true; 524 fIsNoDisplace = true;
523 } else if (steppingAlgorithm==fUseDistanceTo 525 } else if (steppingAlgorithm==fUseDistanceToBoundary) {
524 //Compute geomlimit (and presafety) : 526 //Compute geomlimit (and presafety) :
525 // - geomlimit will be: 527 // - geomlimit will be:
526 // == the straight line distance to the 528 // == the straight line distance to the boundary if currentRange is
527 // longer than that 529 // longer than that
528 // == a big value [geombig = 1.e50*mm] 530 // == a big value [geombig = 1.e50*mm] if currentRange is shorter than
529 // the straight line distance to the 531 // the straight line distance to the boundary
530 // - presafety will be updated as well 532 // - presafety will be updated as well
531 // So the particle can travell 'gemlimit' 533 // So the particle can travell 'gemlimit' distance (along a straight
532 // line!) in its current direction: 534 // line!) in its current direction:
533 // (1) before reaching a boundary (geomli 535 // (1) before reaching a boundary (geomlimit < geombig) OR
534 // (2) before reaching its current range 536 // (2) before reaching its current range (geomlimit == geombig)
535 geomlimit = ComputeGeomLimit(track, presaf 537 geomlimit = ComputeGeomLimit(track, presafety, currentRange);
536 // Record that the particle is on a bounda 538 // Record that the particle is on a boundary
537 if ( (stepStatus==fGeomBoundary) || (stepS 539 if ( (stepStatus==fGeomBoundary) || (stepStatus==fUndefined && presafety==0.0)) {
538 fIsWasOnBoundary = true; 540 fIsWasOnBoundary = true;
539 } 541 }
540 // Set skin depth = skin x elastic_mean_fr 542 // Set skin depth = skin x elastic_mean_free_path
541 skindepth = skin*fLambda0; 543 skindepth = skin*fLambda0;
542 // Init the flag that indicates that the p 544 // Init the flag that indicates that the particle are within a skindepth
543 // distance from a boundary 545 // distance from a boundary
544 fIsInsideSkin = false; 546 fIsInsideSkin = false;
545 // Check if we can try Single Scattering b 547 // Check if we can try Single Scattering because we are within skindepth
546 // distance from/to a boundary OR the curr 548 // distance from/to a boundary OR the current minimum true-step-length is
547 // shorter than skindepth. NOTICE: the lat 549 // shorter than skindepth. NOTICE: the latest has only efficieny reasons
548 // because the MSC angular sampling is fin 550 // because the MSC angular sampling is fine for any short steps but much
549 // faster to try single scattering in case 551 // faster to try single scattering in case of short steps.
550 if ((stepStatus==fGeomBoundary) || (presaf 552 if ((stepStatus==fGeomBoundary) || (presafety<skindepth) || (fTheTrueStepLenght<skindepth)) {
551 // check if we are within skindepth dist 553 // check if we are within skindepth distance from a boundary
552 if ((stepStatus == fGeomBoundary) || (pr 554 if ((stepStatus == fGeomBoundary) || (presafety < skindepth)) {
553 fIsInsideSkin = true; 555 fIsInsideSkin = true;
554 fIsWasOnBoundary = true; 556 fIsWasOnBoundary = true;
555 } 557 }
556 //Try single scattering: 558 //Try single scattering:
557 // - sample distance to next single scat 559 // - sample distance to next single scattering interaction (sslimit)
558 // - compare to current minimum length 560 // - compare to current minimum length
559 // == if sslimit is the shorter: 561 // == if sslimit is the shorter:
560 // - set the step length to ssl 562 // - set the step length to sslimit
561 // - indicate that single scatt 563 // - indicate that single scattering needs to be done
562 // == else : nothing to do 564 // == else : nothing to do
563 //- in both cases, the step length was v 565 //- in both cases, the step length was very short so geometrical and
564 // true path length are the same 566 // true path length are the same
565 G4double sslimit = -1.*fLambda0*G4Log(G4 567 G4double sslimit = -1.*fLambda0*G4Log(G4UniformRand());
566 // compare to current minimum step lengt 568 // compare to current minimum step length
567 if (sslimit<fTheTrueStepLenght) { 569 if (sslimit<fTheTrueStepLenght) {
568 fTheTrueStepLenght = sslimit; 570 fTheTrueStepLenght = sslimit;
569 fIsSingleScattering = true; 571 fIsSingleScattering = true;
570 } 572 }
571 // short step -> true step length equal 573 // short step -> true step length equal to geometrical path length
572 fTheZPathLenght = fTheTrueStepLeng 574 fTheZPathLenght = fTheTrueStepLenght;
573 // Set taht everything is done in step-l 575 // Set taht everything is done in step-limit phase so no MSC call
574 // We will check if we need to perform t 576 // We will check if we need to perform the single-scattering angular
575 // sampling i.e. if single elastic scatt 577 // sampling i.e. if single elastic scattering was the winer!
576 fIsEverythingWasDone = true; 578 fIsEverythingWasDone = true;
577 } else { 579 } else {
578 // After checking we know that we cannot 580 // After checking we know that we cannot try single scattering so we will
579 // need to make an MSC step 581 // need to make an MSC step
580 // Indicate that we need to make and MSC 582 // Indicate that we need to make and MSC step. We do not check if we can
581 // do it now i.e. if presafety>final_tru 583 // do it now i.e. if presafety>final_true_step_length so we let the
582 // fIsEverythingWasDone = false which in 584 // fIsEverythingWasDone = false which indicates that we will perform
583 // MSC after transportation. 585 // MSC after transportation.
584 fIsMultipleSacettring = true; 586 fIsMultipleSacettring = true;
585 // Init the first-real-step falg: it wil 587 // Init the first-real-step falg: it will indicate if we do the first
586 // non-single scattering step in this vo 588 // non-single scattering step in this volume with this particle
587 fIsFirstRealStep = false; 589 fIsFirstRealStep = false;
588 // If previously the partcile was on bou 590 // If previously the partcile was on boundary it was within skin as
589 // well. When it is not within skin anym 591 // well. When it is not within skin anymore it has just left the skin
590 // so we make the first real MSC step wi 592 // so we make the first real MSC step with the particle.
591 if (fIsWasOnBoundary && !fIsInsideSkin) 593 if (fIsWasOnBoundary && !fIsInsideSkin) {
592 // reset the 'was on boundary' indicat 594 // reset the 'was on boundary' indicator flag
593 fIsWasOnBoundary = false; 595 fIsWasOnBoundary = false;
594 fIsFirstRealStep = true; 596 fIsFirstRealStep = true;
595 } 597 }
596 // If this is the first-real msc step (t 598 // If this is the first-real msc step (the partcile has just left the
597 // skin) or this is the first step with 599 // skin) or this is the first step with the particle (was born or
598 // primary): 600 // primary):
599 // - set the initial range that will b 601 // - set the initial range that will be used later to limit its step
600 // (only in this volume, because aft 602 // (only in this volume, because after boundary crossing at the
601 // first-real MSC step we will reset 603 // first-real MSC step we will reset)
602 // - don't let the partcile to cross th 604 // - don't let the partcile to cross the volume just in one step
603 if (firstStep || fIsFirstRealStep || ran 605 if (firstStep || fIsFirstRealStep || rangeinit>1.e+20) {
604 rangeinit = currentRange; 606 rangeinit = currentRange;
605 // If geomlimit < geombig than the par 607 // If geomlimit < geombig than the particle might reach the boundary
606 // along its initial direction before 608 // along its initial direction before losing its energy (in this step)
607 // Otherwise we can be sure that the p 609 // Otherwise we can be sure that the particle will lose it energy
608 // before reaching the boundary along 610 // before reaching the boundary along a starigth line so there is no
609 // geometrical limit appalied. [Howeve 611 // geometrical limit appalied. [However, tgeom is set only in the
610 // first or the first-real MSC step. A 612 // first or the first-real MSC step. After the first or first real
611 // MSC step the direction will change 613 // MSC step the direction will change tgeom won't guaranty anything!
612 // But we will try to end up within sk 614 // But we will try to end up within skindepth from the boundary using
613 // the actual value of geomlimit(See l 615 // the actual value of geomlimit(See later at step reduction close to
614 // boundary).] 616 // boundary).]
615 if (geomlimit<geombig) { 617 if (geomlimit<geombig) {
616 // transfrom straight line distance 618 // transfrom straight line distance to the boundary to real step
617 // length based on the mean values ( 619 // length based on the mean values (using the prestep point
618 // first-transport mean free path i. 620 // first-transport mean free path i.e. no energy loss correction)
619 if ((1.-geomlimit/fLambda1)> 0.) { 621 if ((1.-geomlimit/fLambda1)> 0.) {
620 geomlimit = -fLambda1*G4Log(1.-geo 622 geomlimit = -fLambda1*G4Log(1.-geomlimit/fLambda1);
621 } 623 }
622 // the 2-different case that could l 624 // the 2-different case that could lead us here
623 if (firstStep) { 625 if (firstStep) {
624 tgeom = 2.*geomlimit/facgeom; 626 tgeom = 2.*geomlimit/facgeom;
625 } else { 627 } else {
626 tgeom = geomlimit/facgeom; 628 tgeom = geomlimit/facgeom;
627 } 629 }
628 } else { 630 } else {
629 tgeom = geombig; 631 tgeom = geombig;
630 } 632 }
631 } 633 }
632 // True step length limit from range fac 634 // True step length limit from range factor. Noteice, that the initial
633 // range is used that was set at the fir 635 // range is used that was set at the first step or first-real MSC step
634 // in this volume with this particle. 636 // in this volume with this particle.
635 tlimit = facrange*rangeinit; 637 tlimit = facrange*rangeinit;
636 // Take the minimum of the true step len 638 // Take the minimum of the true step length limits coming from
637 // geometrical constraint or range-facto 639 // geometrical constraint or range-factor limitation
638 tlimit = std::min(tlimit,tgeom); 640 tlimit = std::min(tlimit,tgeom);
639 // Step reduction close to boundary: we 641 // Step reduction close to boundary: we try to end up within skindepth
640 // from the boundary ( Notice: in case o 642 // from the boundary ( Notice: in case of mag. field it might not work
641 // because geomlimit is the straigth lin 643 // because geomlimit is the straigth line distance to the boundary in
642 // the currect direction (if geomlimit<g 644 // the currect direction (if geomlimit<geombig) and mag. field can
643 // change the initial direction. So te p 645 // change the initial direction. So te particle might hit some boundary
644 // before in a different direction. Howe 646 // before in a different direction. However, here we restrict the true
645 // path length to this (straight line) l 647 // path length to this (straight line) lenght so the corresponding
646 // transport distance (straight line) wi 648 // transport distance (straight line) will be even shorter than
647 // geomlimit-0.999*skindepth after the c 649 // geomlimit-0.999*skindepth after the change of true->geom.
648 if (geomlimit<geombig) { 650 if (geomlimit<geombig) {
649 tlimit = std::min(tlimit, geomlimit-0. 651 tlimit = std::min(tlimit, geomlimit-0.999*skindepth);
650 } 652 }
651 // randomize 1st step or 1st 'normal' st 653 // randomize 1st step or 1st 'normal' step in volume
652 if (firstStep || fIsFirstRealStep) { 654 if (firstStep || fIsFirstRealStep) {
653 fTheTrueStepLenght = std::min(fTheTrue 655 fTheTrueStepLenght = std::min(fTheTrueStepLenght, Randomizetlimit());
654 } else { 656 } else {
655 fTheTrueStepLenght = std::min(fTheTrue 657 fTheTrueStepLenght = std::min(fTheTrueStepLenght, tlimit);
656 } 658 }
657 } 659 }
658 } else if (steppingAlgorithm==fUseSafetyPlus 660 } else if (steppingAlgorithm==fUseSafetyPlus) { // THE ERROR_FREE stepping alg.
659 presafety = ComputeSafety(sp->GetPosition 661 presafety = ComputeSafety(sp->GetPosition(),fTheTrueStepLenght);
660 geomlimit = presafety; 662 geomlimit = presafety;
661 // Set skin depth = skin x elastic_mean_fr 663 // Set skin depth = skin x elastic_mean_free_path
662 skindepth = skin*fLambda0; 664 skindepth = skin*fLambda0;
663 // Check if we can try Single Scattering b 665 // Check if we can try Single Scattering because we are within skindepth
664 // distance from/to a boundary OR the curr 666 // distance from/to a boundary OR the current minimum true-step-length is
665 // shorter than skindepth. NOTICE: the lat 667 // shorter than skindepth. NOTICE: the latest has only efficieny reasons
666 // because the MSC angular sampling is fin 668 // because the MSC angular sampling is fine for any short steps but much
667 // faster to try single scattering in case 669 // faster to try single scattering in case of short steps.
668 if ((stepStatus==fGeomBoundary) || (presaf 670 if ((stepStatus==fGeomBoundary) || (presafety<skindepth) || (fTheTrueStepLenght<skindepth)) {
669 //Try single scattering: 671 //Try single scattering:
670 // - sample distance to next single scat 672 // - sample distance to next single scattering interaction (sslimit)
671 // - compare to current minimum length 673 // - compare to current minimum length
672 // == if sslimit is the shorter: 674 // == if sslimit is the shorter:
673 // - set the step length to ssl 675 // - set the step length to sslimit
674 // - indicate that single scatt 676 // - indicate that single scattering needs to be done
675 // == else : nothing to do 677 // == else : nothing to do
676 //- in both cases, the step length was v 678 //- in both cases, the step length was very short so geometrical and
677 // true path length are the same 679 // true path length are the same
678 G4double sslimit = -1.*fLambda0*G4Log(G4 680 G4double sslimit = -1.*fLambda0*G4Log(G4UniformRand());
679 // compare to current minimum step lengt 681 // compare to current minimum step length
680 if (sslimit<fTheTrueStepLenght) { 682 if (sslimit<fTheTrueStepLenght) {
681 fTheTrueStepLenght = sslimit; 683 fTheTrueStepLenght = sslimit;
682 fIsSingleScattering = true; 684 fIsSingleScattering = true;
683 } 685 }
684 // short step -> true step length equal 686 // short step -> true step length equal to geometrical path length
685 fTheZPathLenght = fTheTrueStepLeng 687 fTheZPathLenght = fTheTrueStepLenght;
686 // Set taht everything is done in step-l 688 // Set taht everything is done in step-limit phase so no MSC call
687 // We will check if we need to perform t 689 // We will check if we need to perform the single-scattering angular
688 // sampling i.e. if single elastic scatt 690 // sampling i.e. if single elastic scattering was the winer!
689 fIsEverythingWasDone = true; 691 fIsEverythingWasDone = true;
690 } else { 692 } else {
691 // After checking we know that we cannot 693 // After checking we know that we cannot try single scattering so we will
692 // need to make an MSC step 694 // need to make an MSC step
693 // Indicate that we need to make and MSC 695 // Indicate that we need to make and MSC step.
694 fIsMultipleSacettring = true; 696 fIsMultipleSacettring = true;
695 fIsEverythingWasDone = true; 697 fIsEverythingWasDone = true;
696 // limit from range factor 698 // limit from range factor
697 fTheTrueStepLenght = std::min(fTheTru 699 fTheTrueStepLenght = std::min(fTheTrueStepLenght, facrange*currentRange);
698 // never let the particle go further tha 700 // never let the particle go further than the safety if we are out of the skin
699 // if we are here we are out of the skin 701 // if we are here we are out of the skin, presafety > 0.
700 if (fTheTrueStepLenght>presafety) { 702 if (fTheTrueStepLenght>presafety) {
701 fTheTrueStepLenght = std::min(fTheTrue 703 fTheTrueStepLenght = std::min(fTheTrueStepLenght, presafety);
702 } 704 }
703 // make sure that we are still within th 705 // make sure that we are still within the aplicability of condensed histry model
704 // i.e. true step length is not longer t 706 // i.e. true step length is not longer than first transport mean free path.
705 // We schould take into account energy l 707 // We schould take into account energy loss along 0.5x lambda_transport1
706 // step length as well. So let it 0.5 x 708 // step length as well. So let it 0.5 x lambda_transport1
707 fTheTrueStepLenght = std::min(fTheTrueSt 709 fTheTrueStepLenght = std::min(fTheTrueStepLenght, fLambda1*0.5);
708 } 710 }
709 } else { 711 } else {
710 // This is the default stepping algorithm: 712 // This is the default stepping algorithm: the fastest but the least
711 // accurate that corresponds to fUseSafety 713 // accurate that corresponds to fUseSafety in Urban model. Note, that GS
712 // model can handle any short steps so we 714 // model can handle any short steps so we do not need the minimum limits
713 // 715 //
714 // NO single scattering in case of skin or 716 // NO single scattering in case of skin or short steps (by defult the MSC
715 // model will be single or even no scatter 717 // model will be single or even no scattering in case of short steps
716 // compared to the elastic mean free path. 718 // compared to the elastic mean free path.)
717 // 719 //
718 // indicate that MSC needs to be done (alw 720 // indicate that MSC needs to be done (always and always after transportation)
719 fIsMultipleSacettring = true; 721 fIsMultipleSacettring = true;
720 if (stepStatus!=fGeomBoundary) { 722 if (stepStatus!=fGeomBoundary) {
721 presafety = ComputeSafety(sp->GetPositio 723 presafety = ComputeSafety(sp->GetPosition(),fTheTrueStepLenght);
722 } 724 }
723 // Far from boundary-> in optimized mode d 725 // Far from boundary-> in optimized mode do not sample dispalcement.
724 if ((distance<presafety) && (gIsOptimizati 726 if ((distance<presafety) && (gIsOptimizationOn)) {
725 fIsNoDisplace = true; 727 fIsNoDisplace = true;
726 } else { 728 } else {
727 // Urban like 729 // Urban like
728 if (firstStep || (stepStatus==fGeomBound 730 if (firstStep || (stepStatus==fGeomBoundary) || rangeinit>1.e+20) {
729 rangeinit = currentRange; 731 rangeinit = currentRange;
730 fr = facrange; 732 fr = facrange;
731 // We don't use this: we won't converge to the 733 // We don't use this: we won't converge to the single scattering results with
732 // decreasing range-factor. 734 // decreasing range-factor.
733 // rangeinit = std::max(rangeinit 735 // rangeinit = std::max(rangeinit, fLambda1);
734 // if(fLambda1 > lambdalimit) { 736 // if(fLambda1 > lambdalimit) {
735 // fr *= (0.75+0.25*fLambda1/la 737 // fr *= (0.75+0.25*fLambda1/lambdalimit);
736 // } 738 // }
737 739
738 } 740 }
739 //step limit 741 //step limit
740 tlimit = std::max(fr*rangeinit, facsafet 742 tlimit = std::max(fr*rangeinit, facsafety*presafety);
741 // first step randomization 743 // first step randomization
742 if (firstStep || stepStatus==fGeomBounda 744 if (firstStep || stepStatus==fGeomBoundary) {
743 fTheTrueStepLenght = std::min(fTheTrue 745 fTheTrueStepLenght = std::min(fTheTrueStepLenght, Randomizetlimit());
744 } else { 746 } else {
745 fTheTrueStepLenght = std::min(fTheTrue 747 fTheTrueStepLenght = std::min(fTheTrueStepLenght, tlimit);
746 } 748 }
747 } 749 }
748 } 750 }
749 // 751 //
750 // unset first-step 752 // unset first-step
751 firstStep =false; 753 firstStep =false;
752 // performe single scattering, multiple scat 754 // performe single scattering, multiple scattering if this later can be done safely here
753 if (fIsEverythingWasDone) { 755 if (fIsEverythingWasDone) {
754 if (fIsSingleScattering) { 756 if (fIsSingleScattering) {
755 // sample single scattering 757 // sample single scattering
756 //G4double ekin = 0.5*(currentKinEnerg 758 //G4double ekin = 0.5*(currentKinEnergy + GetEnergy(particle,currentRange-fTheTrueStepLenght,currentCouple));
757 G4double lekin = G4Log(currentKinEnergy 759 G4double lekin = G4Log(currentKinEnergy);
758 G4double pt2 = currentKinEnergy*(curr 760 G4double pt2 = currentKinEnergy*(currentKinEnergy+2.0*CLHEP::electron_mass_c2);
759 G4double beta2 = pt2/(pt2+CLHEP::electr 761 G4double beta2 = pt2/(pt2+CLHEP::electron_mass_c2*CLHEP::electron_mass_c2);
760 G4double cost = fGSTable->SingleScatte 762 G4double cost = fGSTable->SingleScattering(1., fScrA, lekin, beta2, currentMaterialIndex);
761 // protection 763 // protection
762 if (cost<-1.) cost = -1.; 764 if (cost<-1.) cost = -1.;
763 if (cost> 1.) cost = 1.; 765 if (cost> 1.) cost = 1.;
764 // compute sint 766 // compute sint
765 G4double dum = 1.-cost; 767 G4double dum = 1.-cost;
766 G4double sint = std::sqrt(dum*(2.-dum) 768 G4double sint = std::sqrt(dum*(2.-dum));
767 G4double phi = CLHEP::twopi*G4Uniform 769 G4double phi = CLHEP::twopi*G4UniformRand();
768 G4double sinPhi = std::sin(phi); 770 G4double sinPhi = std::sin(phi);
769 G4double cosPhi = std::cos(phi); 771 G4double cosPhi = std::cos(phi);
770 fTheNewDirection.set(sint*cosPhi,sint*si 772 fTheNewDirection.set(sint*cosPhi,sint*sinPhi,cost);
771 } else if (fIsMultipleSacettring) { 773 } else if (fIsMultipleSacettring) {
772 // sample multiple scattering 774 // sample multiple scattering
773 SampleMSC(); // fTheZPathLenght, fTheDis 775 SampleMSC(); // fTheZPathLenght, fTheDisplacementVector and fTheNewDirection will be set
774 } // and if single scattering but it was l 776 } // and if single scattering but it was longer => nothing to do
775 } //else { do nothing here but after transpo 777 } //else { do nothing here but after transportation
776 // 778 //
777 return ConvertTrueToGeom(fTheTrueStepLenght, 779 return ConvertTrueToGeom(fTheTrueStepLenght,currentMinimalStep);
778 } 780 }
779 781
780 782
781 G4double G4GoudsmitSaundersonMscModel::Compute 783 G4double G4GoudsmitSaundersonMscModel::ComputeGeomPathLength(G4double) {
782 // convert true ->geom 784 // convert true ->geom
783 // It is called from the step limitation Com 785 // It is called from the step limitation ComputeTruePathLengthLimit if
784 // !fIsEverythingWasDone but protect: 786 // !fIsEverythingWasDone but protect:
785 par1 = -1.; 787 par1 = -1.;
786 par2 = par3 = 0.; 788 par2 = par3 = 0.;
787 // if fIsEverythingWasDone = TRUE => fTheZP 789 // if fIsEverythingWasDone = TRUE => fTheZPathLenght is already set
788 // so return with the already known value 790 // so return with the already known value
789 // Otherwise: 791 // Otherwise:
790 if (!fIsEverythingWasDone) { 792 if (!fIsEverythingWasDone) {
791 // this correction needed to run MSC with 793 // this correction needed to run MSC with eIoni and eBrem inactivated
792 // and makes no harm for a normal run 794 // and makes no harm for a normal run
793 fTheTrueStepLenght = std::min(fTheTrueStep 795 fTheTrueStepLenght = std::min(fTheTrueStepLenght,currentRange);
794 // do the true -> geom transformation 796 // do the true -> geom transformation
795 fTheZPathLenght = fTheTrueStepLenght; 797 fTheZPathLenght = fTheTrueStepLenght;
796 // z = t for very small true-path-length 798 // z = t for very small true-path-length
797 if (fTheTrueStepLenght<tlimitminfix2) { 799 if (fTheTrueStepLenght<tlimitminfix2) {
798 return fTheZPathLenght; 800 return fTheZPathLenght;
799 } 801 }
800 G4double tau = fTheTrueStepLenght/fLambda1 802 G4double tau = fTheTrueStepLenght/fLambda1;
801 if (tau<=tausmall) { 803 if (tau<=tausmall) {
802 fTheZPathLenght = std::min(fTheTrueStepL 804 fTheZPathLenght = std::min(fTheTrueStepLenght, fLambda1);
803 } else if (fTheTrueStepLenght<currentRang 805 } else if (fTheTrueStepLenght<currentRange*dtrl) {
804 if (tau<taulim) fTheZPathLenght = fTheTr 806 if (tau<taulim) fTheZPathLenght = fTheTrueStepLenght*(1.-0.5*tau) ;
805 else fTheZPathLenght = fLambd 807 else fTheZPathLenght = fLambda1*(1.-G4Exp(-tau));
806 } else if (currentKinEnergy<mass || fTheTr 808 } else if (currentKinEnergy<mass || fTheTrueStepLenght==currentRange) {
807 par1 = 1./currentRange ; // alpha =1 809 par1 = 1./currentRange ; // alpha =1/range_init for Ekin<mass
808 par2 = 1./(par1*fLambda1) ; // 1/(alpha 810 par2 = 1./(par1*fLambda1) ; // 1/(alphaxlambda01)
809 par3 = 1.+par2 ; // 1+1/ 811 par3 = 1.+par2 ; // 1+1/
810 if (fTheTrueStepLenght<currentRange) { 812 if (fTheTrueStepLenght<currentRange) {
811 fTheZPathLenght = 1./(par1*par3) * (1. 813 fTheZPathLenght = 1./(par1*par3) * (1.-std::pow(1.-par1*fTheTrueStepLenght,par3));
812 } else { 814 } else {
813 fTheZPathLenght = 1./(par1*par3); 815 fTheZPathLenght = 1./(par1*par3);
814 } 816 }
815 } else { 817 } else {
816 G4double rfin = std::max(currentRange 818 G4double rfin = std::max(currentRange-fTheTrueStepLenght, 0.01*currentRange);
817 G4double T1 = GetEnergy(particle,rf 819 G4double T1 = GetEnergy(particle,rfin,currentCouple);
818 G4double lambda1 = GetTransportMeanFreeP 820 G4double lambda1 = GetTransportMeanFreePathOnly(particle,T1);
819 // 821 //
820 par1 = (fLambda1-lambda1)/(fLambda1*fThe 822 par1 = (fLambda1-lambda1)/(fLambda1*fTheTrueStepLenght); // alpha
821 par2 = 1./(par1*fLambda1); 823 par2 = 1./(par1*fLambda1);
822 par3 = 1.+par2 ; 824 par3 = 1.+par2 ;
823 G4Pow *g4calc = G4Pow::GetInstance(); 825 G4Pow *g4calc = G4Pow::GetInstance();
824 fTheZPathLenght = 1./(par1*par3) * (1.-g 826 fTheZPathLenght = 1./(par1*par3) * (1.-g4calc->powA(1.-par1*fTheTrueStepLenght,par3));
825 } 827 }
826 } 828 }
827 fTheZPathLenght = std::min(fTheZPathLenght, 829 fTheZPathLenght = std::min(fTheZPathLenght, fLambda1);
828 // 830 //
829 return fTheZPathLenght; 831 return fTheZPathLenght;
830 } 832 }
831 833
832 834
833 G4double G4GoudsmitSaundersonMscModel::Compute 835 G4double G4GoudsmitSaundersonMscModel::ComputeTrueStepLength(G4double geomStepLength) {
834 // init 836 // init
835 fIsEndedUpOnBoundary = false; 837 fIsEndedUpOnBoundary = false;
836 // step defined other than transportation 838 // step defined other than transportation
837 if (geomStepLength==fTheZPathLenght) { 839 if (geomStepLength==fTheZPathLenght) {
838 return fTheTrueStepLenght; 840 return fTheTrueStepLenght;
839 } 841 }
840 // else :: 842 // else ::
841 // - set the flag that transportation was th 843 // - set the flag that transportation was the winer so DoNothin in DOIT !!
842 // - convert geom -> true by using the mean 844 // - convert geom -> true by using the mean value
843 fIsEndedUpOnBoundary = true; // OR LAST STEP 845 fIsEndedUpOnBoundary = true; // OR LAST STEP
844 fTheZPathLenght = geomStepLength; 846 fTheZPathLenght = geomStepLength;
845 // was a short single scattering step 847 // was a short single scattering step
846 if (fIsEverythingWasDone && !fIsMultipleSace 848 if (fIsEverythingWasDone && !fIsMultipleSacettring) {
847 fTheTrueStepLenght = geomStepLength; 849 fTheTrueStepLenght = geomStepLength;
848 return fTheTrueStepLenght; 850 return fTheTrueStepLenght;
849 } 851 }
850 // t = z for very small step 852 // t = z for very small step
851 if (geomStepLength<tlimitminfix2) { 853 if (geomStepLength<tlimitminfix2) {
852 fTheTrueStepLenght = geomStepLength; 854 fTheTrueStepLenght = geomStepLength;
853 // recalculation 855 // recalculation
854 } else { 856 } else {
855 G4double tlength = geomStepLength; 857 G4double tlength = geomStepLength;
856 if (geomStepLength>fLambda1*tausmall) { 858 if (geomStepLength>fLambda1*tausmall) {
857 if (par1< 0.) { 859 if (par1< 0.) {
858 tlength = -fLambda1*G4Log(1.-geomStepL 860 tlength = -fLambda1*G4Log(1.-geomStepLength/fLambda1) ;
859 } else { 861 } else {
860 if (par1*par3*geomStepLength<1.) { 862 if (par1*par3*geomStepLength<1.) {
861 G4Pow *g4calc = G4Pow::GetInstance() 863 G4Pow *g4calc = G4Pow::GetInstance();
862 tlength = (1.-g4calc->powA( 1.-par1* 864 tlength = (1.-g4calc->powA( 1.-par1*par3*geomStepLength,1./par3))/par1;
863 } else { 865 } else {
864 tlength = currentRange; 866 tlength = currentRange;
865 } 867 }
866 } 868 }
867 if (tlength<geomStepLength || tlength>fT 869 if (tlength<geomStepLength || tlength>fTheTrueStepLenght) {
868 tlength = geomStepLength; 870 tlength = geomStepLength;
869 } 871 }
870 } 872 }
871 fTheTrueStepLenght = tlength; 873 fTheTrueStepLenght = tlength;
872 } 874 }
873 // 875 //
874 return fTheTrueStepLenght; 876 return fTheTrueStepLenght;
875 } 877 }
876 878
877 G4ThreeVector& 879 G4ThreeVector&
878 G4GoudsmitSaundersonMscModel::SampleScattering 880 G4GoudsmitSaundersonMscModel::SampleScattering(const G4ThreeVector& oldDirection, G4double) {
879 if (steppingAlgorithm==fUseDistanceToBoundar 881 if (steppingAlgorithm==fUseDistanceToBoundary && fIsEverythingWasDone && fIsSingleScattering) {
880 // single scattering was and scattering ha 882 // single scattering was and scattering happend
881 fTheNewDirection.rotateUz(oldDirection); 883 fTheNewDirection.rotateUz(oldDirection);
882 fParticleChange->ProposeMomentumDirection( 884 fParticleChange->ProposeMomentumDirection(fTheNewDirection);
883 return fTheDisplacementVector; 885 return fTheDisplacementVector;
884 } else if (steppingAlgorithm==fUseSafetyPlus 886 } else if (steppingAlgorithm==fUseSafetyPlus) { // error-free stepping
885 if (fIsEndedUpOnBoundary) { // do nothing 887 if (fIsEndedUpOnBoundary) { // do nothing on the boundary
886 return fTheDisplacementVector; 888 return fTheDisplacementVector;
887 } else if (fIsEverythingWasDone) { // evry 889 } else if (fIsEverythingWasDone) { // evrything is done if not optimizations case !!!
888 // check single scattering and see if it 890 // check single scattering and see if it happened
889 if (fIsSingleScattering) { 891 if (fIsSingleScattering) {
890 fTheNewDirection.rotateUz(oldDirection 892 fTheNewDirection.rotateUz(oldDirection);
891 fParticleChange->ProposeMomentumDirect 893 fParticleChange->ProposeMomentumDirection(fTheNewDirection);
892 return fTheDisplacementVector; 894 return fTheDisplacementVector;
893 } 895 }
894 // check if multiple scattering happened 896 // check if multiple scattering happened and do things only if scattering was really happening
895 if (fIsMultipleSacettring && !fIsNoScatt 897 if (fIsMultipleSacettring && !fIsNoScatteringInMSC) {
896 fTheNewDirection.rotateUz(oldDirect 898 fTheNewDirection.rotateUz(oldDirection);
897 fTheDisplacementVector.rotateUz(old 899 fTheDisplacementVector.rotateUz(oldDirection);
898 fParticleChange->ProposeMomentumDir 900 fParticleChange->ProposeMomentumDirection(fTheNewDirection);
899 } 901 }
900 // The only thing that could happen if w 902 // The only thing that could happen if we are here (fUseSafety and fIsEverythingWasDone)
901 // is that single scattering was tried 903 // is that single scattering was tried but did not win so scattering did not happen.
902 // So no displacement and no scattering 904 // So no displacement and no scattering
903 return fTheDisplacementVector; 905 return fTheDisplacementVector;
904 } 906 }
905 // 907 //
906 // The only thing that could still happen 908 // The only thing that could still happen with fUseSafetyPlus is that we are in the
907 // optimization branch: so sample MSC angl 909 // optimization branch: so sample MSC angle here (no displacement)
908 } 910 }
909 //else MSC needs to be done here 911 //else MSC needs to be done here
910 SampleMSC(); 912 SampleMSC();
911 if (!fIsNoScatteringInMSC) { 913 if (!fIsNoScatteringInMSC) {
912 fTheNewDirection.rotateUz(oldDirection); 914 fTheNewDirection.rotateUz(oldDirection);
913 fParticleChange->ProposeMomentumDirection( 915 fParticleChange->ProposeMomentumDirection(fTheNewDirection);
914 if (!fIsNoDisplace) { 916 if (!fIsNoDisplace) {
915 fTheDisplacementVector.rotateUz(oldDirec 917 fTheDisplacementVector.rotateUz(oldDirection);
916 } 918 }
917 } 919 }
918 // 920 //
919 return fTheDisplacementVector; 921 return fTheDisplacementVector;
920 } 922 }
921 923
922 924
923 void G4GoudsmitSaundersonMscModel::SampleMSC() 925 void G4GoudsmitSaundersonMscModel::SampleMSC() {
924 fIsNoScatteringInMSC = false; 926 fIsNoScatteringInMSC = false;
925 // kinetic energy is assumed to be in Geant4 927 // kinetic energy is assumed to be in Geant4 internal energy unit which is MeV
926 G4double kineticEnergy = currentKinEnergy; 928 G4double kineticEnergy = currentKinEnergy;
927 // 929 //
928 // Energy loss correction: 2 version 930 // Energy loss correction: 2 version
929 G4double eloss = 0.0; 931 G4double eloss = 0.0;
930 // if (fTheTrueStepLenght > currentRange*dtrl 932 // if (fTheTrueStepLenght > currentRange*dtrl) {
931 eloss = kineticEnergy - GetEnergy(particle,c 933 eloss = kineticEnergy - GetEnergy(particle,currentRange-fTheTrueStepLenght,currentCouple);
932 // } else { 934 // } else {
933 // eloss = fTheTrueStepLenght*GetDEDX(parti 935 // eloss = fTheTrueStepLenght*GetDEDX(particle,kineticEnergy,currentCouple);
934 // } 936 // }
935 937
936 G4double tau = 0.;// = kineticEnergy/ele 938 G4double tau = 0.;// = kineticEnergy/electron_mass_c2; // where kinEnergy is the mean kinetic energy
937 G4double tau2 = 0.;// = tau*tau; 939 G4double tau2 = 0.;// = tau*tau;
938 G4double eps0 = 0.;// = eloss/kineticEnerg 940 G4double eps0 = 0.;// = eloss/kineticEnergy0; // energy loss fraction to the begin step energy
939 G4double epsm = 0.;// = eloss/kineticEnerg 941 G4double epsm = 0.;// = eloss/kineticEnergy; // energy loss fraction to the mean step energy
940 942
941 // - init. 943 // - init.
942 G4double efEnergy = kineticEnergy; 944 G4double efEnergy = kineticEnergy;
943 G4double efStep = fTheTrueStepLenght; 945 G4double efStep = fTheTrueStepLenght;
944 946
945 G4double kineticEnergy0 = kineticEnergy; 947 G4double kineticEnergy0 = kineticEnergy;
946 if (gIsUseAccurate) { // - use accurate e 948 if (gIsUseAccurate) { // - use accurate energy loss correction
947 kineticEnergy -= 0.5*eloss; // mean ener 949 kineticEnergy -= 0.5*eloss; // mean energy along the full step
948 // other parameters for energy loss correc 950 // other parameters for energy loss corrections
949 tau = kineticEnergy/electron_m 951 tau = kineticEnergy/electron_mass_c2; // where kinEnergy is the mean kinetic energy
950 tau2 = tau*tau; 952 tau2 = tau*tau;
951 eps0 = eloss/kineticEnergy0; // 953 eps0 = eloss/kineticEnergy0; // energy loss fraction to the begin step energy
952 epsm = eloss/kineticEnergy; // 954 epsm = eloss/kineticEnergy; // energy loss fraction to the mean step energy
953 955
954 efEnergy = kineticEnergy * (1.-epsm 956 efEnergy = kineticEnergy * (1.-epsm*epsm*(6.+10.*tau+5.*tau2)/(24.*tau2+48.*tau+72.));
955 G4double dum = 0.166666*(4.+tau*(6.+tau 957 G4double dum = 0.166666*(4.+tau*(6.+tau*(7.+tau*(4.+tau))))*(epsm/((tau+1.)*(tau+2.)))*(epsm/((tau+1.)*(tau+2.)));
956 efStep = fTheTrueStepLenght*(1.-d 958 efStep = fTheTrueStepLenght*(1.-dum);
957 } else { // - t 959 } else { // - take only mean energy
958 kineticEnergy -= 0.5*eloss; // mean ener 960 kineticEnergy -= 0.5*eloss; // mean energy along the full step
959 efEnergy = kineticEnergy; 961 efEnergy = kineticEnergy;
960 G4double factor = 1./(1.+0.9784671*kinetic 962 G4double factor = 1./(1.+0.9784671*kineticEnergy); //0.9784671 = 1/(2*m_e)
961 eps0 = eloss/kineticEnergy0; 963 eps0 = eloss/kineticEnergy0;
962 epsm = eps0/(1.-0.5*eps0); 964 epsm = eps0/(1.-0.5*eps0);
963 G4double temp = 0.3*(1 -factor*(1.-0.333 965 G4double temp = 0.3*(1 -factor*(1.-0.333333*factor))*eps0*eps0;
964 efStep = fTheTrueStepLenght*(1.+t 966 efStep = fTheTrueStepLenght*(1.+temp);
965 } 967 }
966 // 968 //
967 // compute elastic mfp, first transport mfp, 969 // compute elastic mfp, first transport mfp, screening parameter, and G1 (with Mott-correction
968 // if it was requested by the user) 970 // if it was requested by the user)
969 fLambda1 = GetTransportMeanFreePath(particle 971 fLambda1 = GetTransportMeanFreePath(particle, efEnergy);
970 // s/lambda_el 972 // s/lambda_el
971 G4double lambdan=0.; 973 G4double lambdan=0.;
972 if (fLambda0>0.0) { 974 if (fLambda0>0.0) {
973 lambdan=efStep/fLambda0; 975 lambdan=efStep/fLambda0;
974 } 976 }
975 if (lambdan<=1.0e-12) { 977 if (lambdan<=1.0e-12) {
976 if (fIsEverythingWasDone) { 978 if (fIsEverythingWasDone) {
977 fTheZPathLenght = fTheTrueStepLenght; 979 fTheZPathLenght = fTheTrueStepLenght;
978 } 980 }
979 fIsNoScatteringInMSC = true; 981 fIsNoScatteringInMSC = true;
980 return; 982 return;
981 } 983 }
982 // first moment: 2.* lambdan *scrA*((1.+scrA 984 // first moment: 2.* lambdan *scrA*((1.+scrA)*log(1.+1./scrA)-1.);
983 G4double Qn1 = lambdan *fG1; 985 G4double Qn1 = lambdan *fG1;
984 // sample scattering angles 986 // sample scattering angles
985 // new direction, relative to the orriginal 987 // new direction, relative to the orriginal one is in {uss,vss,wss}
986 G4double cosTheta1 = 1.0, sinTheta1 = 0.0, c 988 G4double cosTheta1 = 1.0, sinTheta1 = 0.0, cosTheta2 = 1.0, sinTheta2 = 0.0;
987 G4double cosPhi1 = 1.0, sinPhi1 = 0.0, c 989 G4double cosPhi1 = 1.0, sinPhi1 = 0.0, cosPhi2 = 1.0, sinPhi2 = 0.0;
988 G4double uss = 0.0, vss = 0.0, w 990 G4double uss = 0.0, vss = 0.0, wss = 1.0;
989 G4double x_coord = 0.0, y_coord = 0.0, z 991 G4double x_coord = 0.0, y_coord = 0.0, z_coord = 1.0;
990 G4double u2 = 0.0, v2 = 0.0; 992 G4double u2 = 0.0, v2 = 0.0;
991 // if we are above the upper grid limit with 993 // if we are above the upper grid limit with lambdaxG1=true-length/first-trans-mfp
992 // => izotropic distribution: lambG1_max =7. 994 // => izotropic distribution: lambG1_max =7.992 but set it to 7
993 if (0.5*Qn1 > 7.0){ 995 if (0.5*Qn1 > 7.0){
994 cosTheta1 = 1.-2.*G4UniformRand(); 996 cosTheta1 = 1.-2.*G4UniformRand();
995 sinTheta1 = std::sqrt((1.-cosTheta1)*(1.+c 997 sinTheta1 = std::sqrt((1.-cosTheta1)*(1.+cosTheta1));
996 cosTheta2 = 1.-2.*G4UniformRand(); 998 cosTheta2 = 1.-2.*G4UniformRand();
997 sinTheta2 = std::sqrt((1.-cosTheta2)*(1.+c 999 sinTheta2 = std::sqrt((1.-cosTheta2)*(1.+cosTheta2));
998 } else { 1000 } else {
999 // sample 2 scattering cost1, sint1, cost 1001 // sample 2 scattering cost1, sint1, cost2 and sint2 for half path
1000 G4double lekin = G4Log(efEnergy); 1002 G4double lekin = G4Log(efEnergy);
1001 G4double pt2 = efEnergy*(efEnergy+2.0 1003 G4double pt2 = efEnergy*(efEnergy+2.0*CLHEP::electron_mass_c2);
1002 G4double beta2 = pt2/(pt2+CLHEP::electr 1004 G4double beta2 = pt2/(pt2+CLHEP::electron_mass_c2*CLHEP::electron_mass_c2);
1003 // backup GS angular dtr pointer (kineti 1005 // backup GS angular dtr pointer (kinetic energy and delta index in case of Mott-correction)
1004 // if the first was an msc sampling (the 1006 // if the first was an msc sampling (the same will be used if the second is also an msc step)
1005 G4GoudsmitSaundersonTable::GSMSCAngularD 1007 G4GoudsmitSaundersonTable::GSMSCAngularDtr *gsDtr = nullptr;
1006 G4int mcEkinIdx = -1; 1008 G4int mcEkinIdx = -1;
1007 G4int mcDeltIdx = -1; 1009 G4int mcDeltIdx = -1;
1008 G4double transfPar = 0.; 1010 G4double transfPar = 0.;
1009 G4bool isMsc = fGSTable->Sampling(0.5*la 1011 G4bool isMsc = fGSTable->Sampling(0.5*lambdan, 0.5*Qn1, fScrA, cosTheta1, sinTheta1, lekin, beta2,
1010 curren 1012 currentMaterialIndex, &gsDtr, mcEkinIdx, mcDeltIdx, transfPar,
1011 true); 1013 true);
1012 fGSTable->Sampling(0.5*lambdan, 0.5*Qn1, 1014 fGSTable->Sampling(0.5*lambdan, 0.5*Qn1, fScrA, cosTheta2, sinTheta2, lekin, beta2,
1013 currentMaterialIndex, 1015 currentMaterialIndex, &gsDtr, mcEkinIdx, mcDeltIdx, transfPar, !isMsc);
1014 if (cosTheta1+cosTheta2==2.) { // no sca 1016 if (cosTheta1+cosTheta2==2.) { // no scattering happened
1015 if (fIsEverythingWasDone) 1017 if (fIsEverythingWasDone)
1016 fTheZPathLenght = fTheTrueStepLeng 1018 fTheZPathLenght = fTheTrueStepLenght;
1017 fIsNoScatteringInMSC = true; 1019 fIsNoScatteringInMSC = true;
1018 return; 1020 return;
1019 } 1021 }
1020 } 1022 }
1021 // sample 2 azimuthal angles 1023 // sample 2 azimuthal angles
1022 G4double phi1 = CLHEP::twopi*G4UniformRand( 1024 G4double phi1 = CLHEP::twopi*G4UniformRand();
1023 sinPhi1 = std::sin(phi1); 1025 sinPhi1 = std::sin(phi1);
1024 cosPhi1 = std::cos(phi1); 1026 cosPhi1 = std::cos(phi1);
1025 G4double phi2 = CLHEP::twopi*G4UniformRand( 1027 G4double phi2 = CLHEP::twopi*G4UniformRand();
1026 sinPhi2 = std::sin(phi2); 1028 sinPhi2 = std::sin(phi2);
1027 cosPhi2 = std::cos(phi2); 1029 cosPhi2 = std::cos(phi2);
1028 1030
1029 // compute final direction realtive to z-di 1031 // compute final direction realtive to z-dir
1030 u2 = sinTheta2*cosPhi2; 1032 u2 = sinTheta2*cosPhi2;
1031 v2 = sinTheta2*sinPhi2; 1033 v2 = sinTheta2*sinPhi2;
1032 G4double u2p = cosTheta1*u2 + sinTheta1*cos 1034 G4double u2p = cosTheta1*u2 + sinTheta1*cosTheta2;
1033 uss = u2p*cosPhi1 - v2*sinPhi1; 1035 uss = u2p*cosPhi1 - v2*sinPhi1;
1034 vss = u2p*sinPhi1 + v2*cosPhi1; 1036 vss = u2p*sinPhi1 + v2*cosPhi1;
1035 wss = cosTheta1*cosTheta2 - sinTheta1*u2; 1037 wss = cosTheta1*cosTheta2 - sinTheta1*u2;
1036 1038
1037 // set new direction (is scattering frame) 1039 // set new direction (is scattering frame)
1038 fTheNewDirection.set(uss,vss,wss); 1040 fTheNewDirection.set(uss,vss,wss);
1039 1041
1040 // set the fTheZPathLenght if we don't samp 1042 // set the fTheZPathLenght if we don't sample displacement and
1041 // we should do everything at the step-limi 1043 // we should do everything at the step-limit-phase before we return
1042 if(fIsNoDisplace && fIsEverythingWasDone) 1044 if(fIsNoDisplace && fIsEverythingWasDone)
1043 fTheZPathLenght = fTheTrueStepLenght; 1045 fTheZPathLenght = fTheTrueStepLenght;
1044 1046
1045 // in optimized-mode if the current-safety 1047 // in optimized-mode if the current-safety > current-range we do not use dispalcement
1046 if(fIsNoDisplace) 1048 if(fIsNoDisplace)
1047 return; 1049 return;
1048 1050
1049 /////////////////////////////////////////// 1051 //////////////////////////////////////////////////////////////////////
1050 // Compute final position 1052 // Compute final position
1051 Qn1 *= fMCtoQ1; 1053 Qn1 *= fMCtoQ1;
1052 if (gIsUseAccurate) { 1054 if (gIsUseAccurate) {
1053 // correction parameter 1055 // correction parameter
1054 G4double par =1.; 1056 G4double par =1.;
1055 if(Qn1<0.7) par = 1.; 1057 if(Qn1<0.7) par = 1.;
1056 else if (Qn1<7.0) par = -0.031376*Qn1+1. 1058 else if (Qn1<7.0) par = -0.031376*Qn1+1.01356;
1057 else par = 0.79; 1059 else par = 0.79;
1058 1060
1059 // Moments with energy loss correction 1061 // Moments with energy loss correction
1060 // --first the uncorrected (for energy l 1062 // --first the uncorrected (for energy loss) values of gamma, eta, a1=a2=0.5*(1-eta), delta
1061 // gamma = G_2/G_1 based on G2 computed 1063 // gamma = G_2/G_1 based on G2 computed from A by using the Wentzel DCS form of G2
1062 G4double loga = G4Log(1.0+1.0/fScrA); 1064 G4double loga = G4Log(1.0+1.0/fScrA);
1063 G4double gamma = 6.0*fScrA*(1.0 + fScrA 1065 G4double gamma = 6.0*fScrA*(1.0 + fScrA)*(loga*(1.0 + 2.0*fScrA) - 2.0)/fG1;
1064 gamma *= fMCtoG2PerG1; 1066 gamma *= fMCtoG2PerG1;
1065 // sample eta from p(eta)=2*eta i.e. P(e 1067 // sample eta from p(eta)=2*eta i.e. P(eta) = eta_square ;-> P(eta) = rand --> eta = sqrt(rand)
1066 G4double eta = std::sqrt(G4UniformRan 1068 G4double eta = std::sqrt(G4UniformRand());
1067 G4double eta1 = 0.5*(1 - eta); // use 1069 G4double eta1 = 0.5*(1 - eta); // used more than once
1068 // 0.5 +sqrt(6)/6 = 0.9082483; 1070 // 0.5 +sqrt(6)/6 = 0.9082483;
1069 // 1/(4*sqrt(6)) = 0.1020621; 1071 // 1/(4*sqrt(6)) = 0.1020621;
1070 // (4-sqrt(6)/(24*sqrt(6))) = 0.02637471 1072 // (4-sqrt(6)/(24*sqrt(6))) = 0.026374715
1071 // delta = 0.9082483-(0.1020621-0.026374 1073 // delta = 0.9082483-(0.1020621-0.0263747*gamma)*Qn1 without energy loss cor.
1072 G4double delta = 0.9082483-(0.1020621-0 1074 G4double delta = 0.9082483-(0.1020621-0.0263747*gamma)*Qn1;
1073 1075
1074 // compute alpha1 and alpha2 for energy 1076 // compute alpha1 and alpha2 for energy loss correction
1075 G4double temp1 = 2.0 + tau; 1077 G4double temp1 = 2.0 + tau;
1076 G4double temp = (2.0+tau*temp1)/((tau+1 1078 G4double temp = (2.0+tau*temp1)/((tau+1.0)*temp1);
1077 //Take logarithmic dependence 1079 //Take logarithmic dependence
1078 temp = temp - (tau+1.0)/((tau+2.0)*(loga 1080 temp = temp - (tau+1.0)/((tau+2.0)*(loga*(1.0+fScrA)-1.0));
1079 temp = temp * epsm; 1081 temp = temp * epsm;
1080 temp1 = 1.0 - temp; 1082 temp1 = 1.0 - temp;
1081 delta = delta + 0.40824829*(eps0*(tau+1. 1083 delta = delta + 0.40824829*(eps0*(tau+1.0)/((tau+2.0)*
1082 (loga*(1.0+fScrA)-1.0)*(loga*(1. 1084 (loga*(1.0+fScrA)-1.0)*(loga*(1.0+2.0*fScrA)-2.0)) - 0.25*temp*temp);
1083 G4double b = eta*delta; 1085 G4double b = eta*delta;
1084 G4double c = eta*(1.0-delta); 1086 G4double c = eta*(1.0-delta);
1085 1087
1086 //Calculate transport direction cosines: 1088 //Calculate transport direction cosines:
1087 // ut,vt,wt is the final position divide 1089 // ut,vt,wt is the final position divided by the true step length
1088 G4double w1v2 = cosTheta1*v2; 1090 G4double w1v2 = cosTheta1*v2;
1089 G4double ut = b*sinTheta1*cosPhi1 + c* 1091 G4double ut = b*sinTheta1*cosPhi1 + c*(cosPhi1*u2 - sinPhi1*w1v2) + eta1*uss*temp1;
1090 G4double vt = b*sinTheta1*sinPhi1 + c* 1092 G4double vt = b*sinTheta1*sinPhi1 + c*(sinPhi1*u2 + cosPhi1*w1v2) + eta1*vss*temp1;
1091 G4double wt = eta1*(1+temp) + b* 1093 G4double wt = eta1*(1+temp) + b*cosTheta1 + c*cosTheta2 + eta1*wss*temp1;
1092 1094
1093 // long step correction 1095 // long step correction
1094 ut *=par; 1096 ut *=par;
1095 vt *=par; 1097 vt *=par;
1096 wt *=par; 1098 wt *=par;
1097 1099
1098 // final position relative to the pre-st 1100 // final position relative to the pre-step point in the scattering frame
1099 // ut = x_f/s so needs to multiply by s 1101 // ut = x_f/s so needs to multiply by s
1100 x_coord = ut*fTheTrueStepLenght; 1102 x_coord = ut*fTheTrueStepLenght;
1101 y_coord = vt*fTheTrueStepLenght; 1103 y_coord = vt*fTheTrueStepLenght;
1102 z_coord = wt*fTheTrueStepLenght; 1104 z_coord = wt*fTheTrueStepLenght;
1103 1105
1104 if(fIsEverythingWasDone){ 1106 if(fIsEverythingWasDone){
1105 // We sample in the step limit so set 1107 // We sample in the step limit so set fTheZPathLenght = transportDistance
1106 // and lateral displacement (x_coord,y 1108 // and lateral displacement (x_coord,y_coord,z_coord-transportDistance)
1107 //Calculate transport distance 1109 //Calculate transport distance
1108 G4double transportDistance = std::sqr 1110 G4double transportDistance = std::sqrt(x_coord*x_coord+y_coord*y_coord+z_coord*z_coord);
1109 // protection 1111 // protection
1110 if(transportDistance>fTheTrueStepLengh 1112 if(transportDistance>fTheTrueStepLenght)
1111 transportDistance = fTheTrueStepLen 1113 transportDistance = fTheTrueStepLenght;
1112 fTheZPathLenght = transportDistance; 1114 fTheZPathLenght = transportDistance;
1113 } 1115 }
1114 // else:: we sample in the DoIt so 1116 // else:: we sample in the DoIt so
1115 // the fTheZPathLenght was already 1117 // the fTheZPathLenght was already set and was taken as transport along zet
1116 fTheDisplacementVector.set(x_coord,y_coo 1118 fTheDisplacementVector.set(x_coord,y_coord,z_coord-fTheZPathLenght);
1117 } else { 1119 } else {
1118 // compute zz = <z>/tPathLength 1120 // compute zz = <z>/tPathLength
1119 // s -> true-path-length 1121 // s -> true-path-length
1120 // z -> geom-path-length:: when PRESTA i 1122 // z -> geom-path-length:: when PRESTA is used z =(def.) <z>
1121 // r -> lateral displacement = s/2 sin(t 1123 // r -> lateral displacement = s/2 sin(theta) => x_f = r cos(phi); y_f = r sin(phi)
1122 G4double zz = 0.0; 1124 G4double zz = 0.0;
1123 if(fIsEverythingWasDone){ 1125 if(fIsEverythingWasDone){
1124 // We sample in the step limit so set 1126 // We sample in the step limit so set fTheZPathLenght = transportDistance
1125 // and lateral displacement (x_coord, 1127 // and lateral displacement (x_coord,y_coord,z_coord-transportDistance)
1126 if(Qn1<0.1) { // use 3-order Taylor a 1128 if(Qn1<0.1) { // use 3-order Taylor approximation of (1-exp(-x))/x around x=0
1127 zz = 1.0 - Qn1*(0.5 - Qn1*(0.166666 1129 zz = 1.0 - Qn1*(0.5 - Qn1*(0.166666667 - 0.041666667*Qn1)); // 1/6 =0.166..7 ; 1/24=0.041..
1128 } else { 1130 } else {
1129 zz = (1.-G4Exp(-Qn1))/Qn1; 1131 zz = (1.-G4Exp(-Qn1))/Qn1;
1130 } 1132 }
1131 } else { 1133 } else {
1132 // we sample in the DoIt so 1134 // we sample in the DoIt so
1133 // the fTheZPathLenght was already se 1135 // the fTheZPathLenght was already set and was taken as transport along zet
1134 zz = fTheZPathLenght/fTheTrueStepLeng 1136 zz = fTheZPathLenght/fTheTrueStepLenght;
1135 } 1137 }
1136 1138
1137 G4double rr = (1.-zz*zz)/(1.-wss*wss); / 1139 G4double rr = (1.-zz*zz)/(1.-wss*wss); // s^2 >= <z>^2+r^2 :: where r^2 = s^2/4 sin^2(theta)
1138 if(rr >= 0.25) rr = 0.25; // 1140 if(rr >= 0.25) rr = 0.25; // (1-<z>^2/s^2)/sin^2(theta) >= r^2/(s^2 sin^2(theta)) = 1/4 must hold
1139 G4double rperp = fTheTrueStepLenght*std: 1141 G4double rperp = fTheTrueStepLenght*std::sqrt(rr); // this is r/sint
1140 x_coord = rperp*uss; 1142 x_coord = rperp*uss;
1141 y_coord = rperp*vss; 1143 y_coord = rperp*vss;
1142 z_coord = zz*fTheTrueStepLenght; 1144 z_coord = zz*fTheTrueStepLenght;
1143 1145
1144 if(fIsEverythingWasDone){ 1146 if(fIsEverythingWasDone){
1145 G4double transportDistance = std::sqrt 1147 G4double transportDistance = std::sqrt(x_coord*x_coord + y_coord*y_coord + z_coord*z_coord);
1146 fTheZPathLenght = transportDistance; 1148 fTheZPathLenght = transportDistance;
1147 } 1149 }
1148 1150
1149 fTheDisplacementVector.set(x_coord,y_coo 1151 fTheDisplacementVector.set(x_coord,y_coord,z_coord- fTheZPathLenght);
1150 } 1152 }
1151 } 1153 }
1152 1154