| Geant4 Cross Reference |
1 //
2 // ********************************************************************
3 // * License and Disclaimer *
4 // * *
5 // * The Geant4 software is copyright of the Copyright Holders of *
6 // * the Geant4 Collaboration. It is provided under the terms and *
7 // * conditions of the Geant4 Software License, included in the file *
8 // * LICENSE and available at http://cern.ch/geant4/license . These *
9 // * include a list of copyright holders. *
10 // * *
11 // * Neither the authors of this software system, nor their employing *
12 // * institutes,nor the agencies providing financial support for this *
13 // * work make any representation or warranty, express or implied, *
14 // * regarding this software system or assume any liability for its *
15 // * use. Please see the license in the file LICENSE and URL above *
16 // * for the full disclaimer and the limitation of liability. *
17 // * *
18 // * This code implementation is the result of the scientific and *
19 // * technical work of the GEANT4 collaboration. *
20 // * By using, copying, modifying or distributing the software (or *
21 // * any work based on the software) you agree to acknowledge its *
22 // * use in resulting scientific publications, and indicate your *
23 // * acceptance of all terms of the Geant4 Software license. *
24 // ********************************************************************
25 //
26 // G4TransportationWithMsc
27 //
28 // Class Description:
29 //
30 // It is a generic process of transportation with multiple scattering included
31 // in the step limitation and propagation.
32 //
33 // Original author: Jonas Hahnfeld, 2022
34
35 // -------------------------------------------------------------------
36 //
37 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
38 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
39
40 #include "G4TransportationWithMsc.hh"
41
42 #include "G4DynamicParticle.hh"
43 #include "G4Electron.hh"
44 #include "G4EmConfigurator.hh"
45 #include "G4EmDataHandler.hh"
46 #include "G4LossTableBuilder.hh"
47 #include "G4LossTableManager.hh"
48 #include "G4ParticleChangeForGamma.hh"
49 #include "G4ParticleChangeForMSC.hh"
50 #include "G4PhysicalConstants.hh"
51 #include "G4PhysicsTableHelper.hh"
52 #include "G4PhysicsVector.hh"
53 #include "G4ProductionCutsTable.hh"
54 #include "G4Step.hh"
55 #include "G4StepPoint.hh"
56 #include "G4StepStatus.hh"
57 #include "G4Track.hh"
58 #include "G4TransportationProcessType.hh"
59 #include "G4VMscModel.hh"
60
61 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
62
63 static constexpr G4double kLowestKinEnergy = 10 * CLHEP::eV;
64 static constexpr G4double kGeomMin = 0.05 * CLHEP::nm;
65 static constexpr G4double kMinDisplacement2 = kGeomMin * kGeomMin;
66
67 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
68
69 G4TransportationWithMsc::G4TransportationWithMsc(ScatteringType type, G4int verbosity)
70 : G4Transportation(verbosity, "TransportationWithMsc"), fType(type)
71 {
72 SetProcessSubType(static_cast<G4int>(TRANSPORTATION_WITH_MSC));
73 SetVerboseLevel(1);
74
75 fEmManager = G4LossTableManager::Instance();
76 fModelManager = new G4EmModelManager;
77
78 if (type == ScatteringType::MultipleScattering) {
79 fParticleChangeForMSC = new G4ParticleChangeForMSC;
80 }
81 else if (type == ScatteringType::SingleScattering) {
82 fParticleChangeForSS = new G4ParticleChangeForGamma;
83 fSecondariesSS = new std::vector<G4DynamicParticle*>;
84 }
85
86 G4ThreeVector zero;
87 fSubStepDynamicParticle = new G4DynamicParticle(G4Electron::Definition(), zero);
88 fSubStepTrack = new G4Track(fSubStepDynamicParticle, 0, zero);
89 fSubStep = new G4Step;
90 fSubStepTrack->SetStep(fSubStep);
91 }
92
93 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
94
95 G4TransportationWithMsc::~G4TransportationWithMsc()
96 {
97 delete fModelManager;
98 delete fParticleChangeForMSC;
99 delete fEmData;
100 delete fParticleChangeForSS;
101 delete fSecondariesSS;
102
103 // fSubStepDynamicParticle is owned and also deleted by fSubStepTrack!
104 delete fSubStepTrack;
105 delete fSubStep;
106 }
107
108 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
109
110 void G4TransportationWithMsc::AddMscModel(G4VMscModel* mscModel, G4int order,
111 const G4Region* region)
112 {
113 if (fType != ScatteringType::MultipleScattering) {
114 G4Exception("G4TransportationWithMsc::AddMscModel", "em0051", FatalException,
115 "not allowed unless type == MultipleScattering");
116 }
117
118 fModelManager->AddEmModel(order, mscModel, nullptr, region);
119 mscModel->SetParticleChange(fParticleChangeForMSC);
120 }
121
122 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
123
124 void G4TransportationWithMsc::AddSSModel(G4VEmModel* model, G4int order, const G4Region* region)
125 {
126 if (fType != ScatteringType::SingleScattering) {
127 G4Exception("G4TransportationWithMsc::AddSSModel", "em0051", FatalException,
128 "not allowed unless type == SingleScattering");
129 }
130
131 fModelManager->AddEmModel(order, model, nullptr, region);
132 model->SetPolarAngleLimit(0.0);
133 model->SetParticleChange(fParticleChangeForSS);
134 }
135
136 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
137
138 void G4TransportationWithMsc::PreparePhysicsTable(const G4ParticleDefinition& part)
139 {
140 if (nullptr == fFirstParticle) {
141 fFirstParticle = ∂
142 G4VMultipleScattering* ptr = nullptr;
143 auto emConfigurator = fEmManager->EmConfigurator();
144 emConfigurator->PrepareModels(&part, ptr, this);
145 }
146
147 if (fFirstParticle == &part) {
148 G4bool master = fEmManager->IsMaster();
149 G4LossTableBuilder* bld = fEmManager->GetTableBuilder();
150 G4bool baseMat = bld->GetBaseMaterialFlag();
151 const auto* theParameters = G4EmParameters::Instance();
152
153 if (master) {
154 SetVerboseLevel(theParameters->Verbose());
155 }
156 else {
157 SetVerboseLevel(theParameters->WorkerVerbose());
158 }
159
160 const G4int numberOfModels = fModelManager->NumberOfModels();
161 if (fType == ScatteringType::MultipleScattering) {
162 for (G4int i = 0; i < numberOfModels; ++i) {
163 auto msc = static_cast<G4VMscModel*>(fModelManager->GetModel(i));
164 msc->SetPolarAngleLimit(theParameters->MscThetaLimit());
165 G4double emax = std::min(msc->HighEnergyLimit(), theParameters->MaxKinEnergy());
166 msc->SetHighEnergyLimit(emax);
167 msc->SetUseBaseMaterials(baseMat);
168 }
169 }
170 else if (fType == ScatteringType::SingleScattering) {
171 if (master) {
172 if (fEmData == nullptr) {
173 fEmData = new G4EmDataHandler(2);
174 }
175
176 fLambdaTable = fEmData->MakeTable(0);
177 bld->InitialiseBaseMaterials(fLambdaTable);
178 }
179 }
180
181 fCuts = fModelManager->Initialise(fFirstParticle, G4Electron::Electron(), verboseLevel);
182 }
183 }
184
185 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
186
187 void G4TransportationWithMsc::BuildPhysicsTable(const G4ParticleDefinition& part)
188 {
189 if (fFirstParticle == &part) {
190 fEmManager->BuildPhysicsTable(fFirstParticle);
191
192 if (fEmManager->IsMaster()) {
193 if (fType == ScatteringType::SingleScattering) {
194 const auto* theParameters = G4EmParameters::Instance();
195 G4LossTableBuilder* bld = fEmManager->GetTableBuilder();
196 const G4ProductionCutsTable* theCoupleTable =
197 G4ProductionCutsTable::GetProductionCutsTable();
198 std::size_t numOfCouples = theCoupleTable->GetTableSize();
199
200 G4double emin = theParameters->MinKinEnergy();
201 G4double emax = theParameters->MaxKinEnergy();
202
203 G4double scale = emax / emin;
204 G4int nbin = theParameters->NumberOfBinsPerDecade() * G4lrint(std::log10(scale));
205 scale = nbin / G4Log(scale);
206
207 G4int bin = G4lrint(scale * G4Log(emax / emin));
208 bin = std::max(bin, 5);
209
210 for (std::size_t i = 0; i < numOfCouples; ++i) {
211 if (!bld->GetFlag(i)) continue;
212
213 // Create physics vector and fill it
214 const G4MaterialCutsCouple* couple = theCoupleTable->GetMaterialCutsCouple((G4int)i);
215
216 auto* aVector = new G4PhysicsLogVector(emin, emax, bin, /*splineFlag*/ true);
217 fModelManager->FillLambdaVector(aVector, couple, /*startNull*/ false);
218 aVector->FillSecondDerivatives();
219 G4PhysicsTableHelper::SetPhysicsVector(fLambdaTable, i, aVector);
220 }
221 }
222 }
223 else {
224 const auto masterProcess = static_cast<const G4TransportationWithMsc*>(GetMasterProcess());
225
226 // Initialisation of models.
227 const G4int numberOfModels = fModelManager->NumberOfModels();
228 if (fType == ScatteringType::MultipleScattering) {
229 for (G4int i = 0; i < numberOfModels; ++i) {
230 auto msc = static_cast<G4VMscModel*>(fModelManager->GetModel(i));
231 auto msc0 = static_cast<G4VMscModel*>(masterProcess->fModelManager->GetModel(i));
232 msc->SetCrossSectionTable(msc0->GetCrossSectionTable(), false);
233 msc->InitialiseLocal(fFirstParticle, msc0);
234 }
235 }
236 else if (fType == ScatteringType::SingleScattering) {
237 this->fLambdaTable = masterProcess->fLambdaTable;
238 }
239 }
240 }
241
242 if (!G4EmParameters::Instance()->IsPrintLocked() && verboseLevel > 0) {
243 G4cout << G4endl;
244 G4cout << GetProcessName() << ": for " << part.GetParticleName();
245 if (fMultipleSteps) {
246 G4cout << " (multipleSteps: 1)";
247 }
248 G4cout << G4endl;
249 fModelManager->DumpModelList(G4cout, verboseLevel);
250 }
251 }
252
253 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
254
255 void G4TransportationWithMsc::StartTracking(G4Track* track)
256 {
257 auto* currParticle = track->GetParticleDefinition();
258 fIonisation = fEmManager->GetEnergyLossProcess(currParticle);
259
260 fSubStepDynamicParticle->SetDefinition(currParticle);
261
262 const G4int numberOfModels = fModelManager->NumberOfModels();
263 if (fType == ScatteringType::MultipleScattering) {
264 for (G4int i = 0; i < numberOfModels; ++i) {
265 auto msc = static_cast<G4VMscModel*>(fModelManager->GetModel(i));
266 msc->StartTracking(track);
267 msc->SetIonisation(fIonisation, currParticle);
268 }
269 }
270
271 // Ensure that field propagation state is also cleared / prepared
272 G4Transportation::StartTracking(track);
273 }
274
275 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
276
277 G4double G4TransportationWithMsc::AlongStepGetPhysicalInteractionLength(const G4Track& track,
278 G4double previousStepSize,
279 G4double currentMinimumStep,
280 G4double& proposedSafety,
281 G4GPILSelection* selection)
282 {
283 *selection = NotCandidateForSelection;
284
285 const G4double physStepLimit = currentMinimumStep;
286
287 switch (fType) {
288 case ScatteringType::MultipleScattering: {
289 // Select the MSC model for the current kinetic energy.
290 G4VMscModel* mscModel = nullptr;
291 const G4double ekin = track.GetKineticEnergy();
292 const auto* couple = track.GetMaterialCutsCouple();
293 const auto* particleDefinition = track.GetParticleDefinition();
294 if (physStepLimit > kGeomMin) {
295 G4double ekinForSelection = ekin;
296 G4double pdgMass = particleDefinition->GetPDGMass();
297 if (pdgMass > CLHEP::GeV) {
298 ekinForSelection *= proton_mass_c2 / pdgMass;
299 }
300
301 if (ekinForSelection >= kLowestKinEnergy) {
302 mscModel = static_cast<G4VMscModel*>(
303 fModelManager->SelectModel(ekinForSelection, couple->GetIndex()));
304 if (mscModel == nullptr) {
305 G4Exception("G4TransportationWithMsc::AlongStepGPIL", "em0052", FatalException,
306 "no MSC model found");
307 }
308 if (!mscModel->IsActive(ekinForSelection)) {
309 mscModel = nullptr;
310 }
311 }
312 }
313
314 // Call the MSC model to potentially limit the step and convert to
315 // geometric path length.
316 if (mscModel != nullptr) {
317 mscModel->SetCurrentCouple(couple);
318
319 // Use the provided track for the first step.
320 const G4Track* currentTrackPtr = &track;
321
322 G4double currentSafety = proposedSafety;
323 G4double currentEnergy = ekin;
324
325 G4double stepLimitLeft = physStepLimit;
326 G4double totalGeometryStepLength = 0, totalTruePathLength = 0;
327 G4bool firstStep = true, continueStepping = fMultipleSteps;
328
329 do {
330 G4double gPathLength = stepLimitLeft;
331 G4double tPathLength =
332 mscModel->ComputeTruePathLengthLimit(*currentTrackPtr, gPathLength);
333 G4bool mscLimitsStep = (tPathLength < stepLimitLeft);
334 if (!fMultipleSteps && mscLimitsStep) {
335 // MSC limits the step.
336 *selection = CandidateForSelection;
337 }
338
339 if (!firstStep) {
340 // Move the navigator to where the previous step ended.
341 fLinearNavigator->LocateGlobalPointWithinVolume(fTransportEndPosition);
342 }
343
344 G4GPILSelection transportSelection;
345 G4double geometryStepLength = G4Transportation::AlongStepGetPhysicalInteractionLength(
346 *currentTrackPtr, previousStepSize, gPathLength, currentSafety, &transportSelection);
347 if (geometryStepLength < gPathLength) {
348 // Transportation limits the step, ie the track hit a boundary.
349 *selection = CandidateForSelection;
350 continueStepping = false;
351 }
352 if (fTransportEndKineticEnergy != currentEnergy) {
353 // Field propagation changed the energy, it's not possible to
354 // estimate the continuous energy loss and continue stepping.
355 continueStepping = false;
356 }
357
358 if (firstStep) {
359 proposedSafety = currentSafety;
360 }
361 totalGeometryStepLength += geometryStepLength;
362
363 // Sample MSC direction change and displacement.
364 const G4double range = mscModel->GetRange(particleDefinition, currentEnergy, couple);
365
366 tPathLength = mscModel->ComputeTrueStepLength(geometryStepLength);
367
368 // Protect against wrong t->g->t conversion.
369 tPathLength = std::min(tPathLength, stepLimitLeft);
370
371 totalTruePathLength += tPathLength;
372 if (*selection != CandidateForSelection && !mscLimitsStep) {
373 // If neither MSC nor transportation limits the step, we got the
374 // distance we want - make sure we exit the loop.
375 continueStepping = false;
376 }
377 else if (tPathLength >= range) {
378 // The particle will stop, exit the loop.
379 continueStepping = false;
380 }
381 else {
382 stepLimitLeft -= tPathLength;
383 }
384
385 // Do not sample scattering at the last or at a small step.
386 if (tPathLength < range && tPathLength > kGeomMin) {
387 static constexpr G4double minSafety = 1.20 * CLHEP::nm;
388 static constexpr G4double sFact = 0.99;
389
390 // The call to SampleScattering() *may* directly fill in the changed
391 // direction into fParticleChangeForMSC, so we have to:
392 // 1) Make sure the momentum direction is initialized.
393 fParticleChangeForMSC->ProposeMomentumDirection(fTransportEndMomentumDir);
394 // 2) Call SampleScattering(), which *may* change it.
395 const G4ThreeVector displacement =
396 mscModel->SampleScattering(fTransportEndMomentumDir, minSafety);
397 // 3) Get the changed direction.
398 fTransportEndMomentumDir = *fParticleChangeForMSC->GetProposedMomentumDirection();
399
400 const G4double r2 = displacement.mag2();
401 if (r2 > kMinDisplacement2) {
402 G4bool positionChanged = true;
403 G4double dispR = std::sqrt(r2);
404 G4double postSafety =
405 sFact * fpSafetyHelper->ComputeSafety(fTransportEndPosition, dispR);
406
407 // Far away from geometry boundary
408 if (postSafety > 0.0 && dispR <= postSafety) {
409 fTransportEndPosition += displacement;
410
411 // Near the boundary
412 }
413 else {
414 // displaced point is definitely within the volume
415 if (dispR < postSafety) {
416 fTransportEndPosition += displacement;
417
418 // reduced displacement
419 }
420 else if (postSafety > kGeomMin) {
421 fTransportEndPosition += displacement * (postSafety / dispR);
422
423 // very small postSafety
424 }
425 else {
426 positionChanged = false;
427 }
428 }
429 if (positionChanged) {
430 fpSafetyHelper->ReLocateWithinVolume(fTransportEndPosition);
431 }
432 }
433 }
434
435 if (continueStepping) {
436 // Update safety according to the geometry distance.
437 if (currentSafety < fEndPointDistance) {
438 currentSafety = 0;
439 }
440 else {
441 currentSafety -= fEndPointDistance;
442 }
443
444 // Update the kinetic energy according to the continuous loss.
445 currentEnergy = mscModel->GetEnergy(particleDefinition, range - tPathLength, couple);
446
447 // From now on, use the track that we can update below.
448 currentTrackPtr = fSubStepTrack;
449
450 fSubStepDynamicParticle->SetKineticEnergy(currentEnergy);
451 fSubStepDynamicParticle->SetMomentumDirection(fTransportEndMomentumDir);
452 fSubStepTrack->SetPosition(fTransportEndPosition);
453
454 G4StepPoint& subPreStepPoint = *fSubStep->GetPreStepPoint();
455 subPreStepPoint.SetMaterialCutsCouple(couple);
456 subPreStepPoint.SetPosition(fTransportEndPosition);
457 subPreStepPoint.SetSafety(currentSafety);
458 subPreStepPoint.SetStepStatus(fAlongStepDoItProc);
459 }
460 firstStep = false;
461 } while (continueStepping);
462
463 // Note: currentEnergy is only updated if continueStepping is true.
464 // In case field propagation changed the energy, this flag is
465 // immediately set to false and currentEnergy is still equal to the
466 // initial kinetic energy stored in ekin.
467 if (currentEnergy != ekin) {
468 // If field propagation didn't change the energy and we potentially
469 // did multiple steps, reset the energy that G4Transportation will
470 // propose to not subtract the energy loss twice.
471 fTransportEndKineticEnergy = ekin;
472 // Also ask for the range again with the initial energy so it is
473 // correctly cached in the G4VEnergyLossProcess.
474 // FIXME: Asking for a range should never change the cached values!
475 (void)mscModel->GetRange(particleDefinition, ekin, couple);
476 }
477
478 fParticleChange.ProposeTrueStepLength(totalTruePathLength);
479
480 // Inform G4Transportation that the momentum might have changed due
481 // to scattering. We do this unconditionally to avoid the situation
482 // where the last step is done without MSC and G4Transportation reset
483 // the flag, for example when running without field.
484 fMomentumChanged = true;
485
486 return totalGeometryStepLength;
487 }
488 break;
489 }
490
491 case ScatteringType::SingleScattering: {
492 // Select the model for the current kinetic energy.
493 const G4double ekin = track.GetKineticEnergy();
494 const auto* couple = track.GetMaterialCutsCouple();
495 const auto* particleDefinition = track.GetParticleDefinition();
496
497 G4double ekinForSelection = ekin;
498 G4double pdgMass = particleDefinition->GetPDGMass();
499 if (pdgMass > CLHEP::GeV) {
500 ekinForSelection *= proton_mass_c2 / pdgMass;
501 }
502
503 G4VEmModel* currentModel = fModelManager->SelectModel(ekinForSelection, couple->GetIndex());
504 if (currentModel == nullptr) {
505 G4Exception("G4TransportationWithMsc::AlongStepGPIL", "em0052", FatalException,
506 "no scattering model found");
507 }
508 if (!currentModel->IsActive(ekinForSelection)) {
509 currentModel = nullptr;
510 }
511
512 if (currentModel != nullptr) {
513 currentModel->SetCurrentCouple(couple);
514 G4int coupleIndex = couple->GetIndex();
515
516 // Compute mean free path.
517 G4double logEkin = track.GetDynamicParticle()->GetLogKineticEnergy();
518 G4double lambda = ((*fLambdaTable)[coupleIndex])->LogVectorValue(ekin, logEkin);
519 if (lambda > 0.0) {
520 // Assume that the mean free path and dE/dx are constant along the
521 // step, which is a valid approximation for most cases.
522 G4double meanFreePath = 1.0 / lambda;
523 G4double dedx = fIonisation->GetDEDX(ekin, couple);
524
525 G4double currentSafety = proposedSafety;
526 G4double currentEnergy = ekin;
527
528 // Use the provided track for the first step.
529 const G4Track* currentTrackPtr = &track;
530
531 G4double stepLimitLeft = physStepLimit;
532 G4double totalStepLength = 0;
533 G4bool firstStep = true, continueStepping = fMultipleSteps;
534
535 do {
536 G4double interactionLength = meanFreePath * -G4Log(G4UniformRand());
537
538 G4bool ssLimitsStep = (interactionLength < stepLimitLeft);
539 G4double gPathLength = stepLimitLeft;
540 if (ssLimitsStep) {
541 if (!fMultipleSteps) {
542 // Scattering limits the step.
543 *selection = CandidateForSelection;
544 }
545 gPathLength = interactionLength;
546 }
547
548 if (!firstStep) {
549 // Move the navigator to where the previous step ended.
550 fLinearNavigator->LocateGlobalPointWithinVolume(fTransportEndPosition);
551 }
552
553 G4GPILSelection transportSelection;
554 G4double geometryStepLength = G4Transportation::AlongStepGetPhysicalInteractionLength(
555 *currentTrackPtr, previousStepSize, gPathLength, currentSafety, &transportSelection);
556 if (geometryStepLength < gPathLength) {
557 // Transportation limits the step, ie the track hit a boundary.
558 *selection = CandidateForSelection;
559 ssLimitsStep = false;
560 continueStepping = false;
561 }
562 if (fTransportEndKineticEnergy != currentEnergy) {
563 // Field propagation changed the energy, it's not possible to
564 // estimate the continuous energy loss and continue stepping.
565 continueStepping = false;
566 }
567
568 if (firstStep) {
569 proposedSafety = currentSafety;
570 }
571 totalStepLength += geometryStepLength;
572
573 if (*selection != CandidateForSelection && !ssLimitsStep) {
574 // If neither scattering nor transportation limits the step, we
575 // got the distance we want - make sure we exit the loop.
576 continueStepping = false;
577 }
578 else {
579 stepLimitLeft -= geometryStepLength;
580 }
581
582 // Update the kinetic energy according to the continuous loss.
583 G4double energyAfterLinearLoss =
584 fTransportEndKineticEnergy - geometryStepLength * dedx;
585
586 if (ssLimitsStep) {
587 fSubStepDynamicParticle->SetKineticEnergy(energyAfterLinearLoss);
588
589 // The call to SampleSecondaries() directly fills in the changed
590 // direction into fParticleChangeForSS, so we have to:
591 // 1) Set the momentum direction in dynamic particle.
592 fSubStepDynamicParticle->SetMomentumDirection(fTransportEndMomentumDir);
593 // 2) Call SampleSecondaries(), which changes the direction.
594 currentModel->SampleSecondaries(fSecondariesSS, couple, fSubStepDynamicParticle,
595 (*fCuts)[coupleIndex]);
596 // 3) Get the changed direction.
597 fTransportEndMomentumDir = fParticleChangeForSS->GetProposedMomentumDirection();
598
599 // Check that the model neither created secondaries nor proposed
600 // a local energy deposit because this process does not know how
601 // to handle these cases.
602 if (fSecondariesSS->size() > 0) {
603 G4Exception("G4TransportationWithMsc::AlongStepGPIL", "em0053", FatalException,
604 "scattering model created secondaries");
605 }
606 if (fParticleChangeForSS->GetLocalEnergyDeposit() > 0) {
607 G4Exception("G4TransportationWithMsc::AlongStepGPIL", "em0053", FatalException,
608 "scattering model proposed energy deposit");
609 }
610 }
611
612 if (continueStepping) {
613 // Update safety according to the geometry distance.
614 if (currentSafety < fEndPointDistance) {
615 currentSafety = 0;
616 }
617 else {
618 currentSafety -= fEndPointDistance;
619 }
620
621 // Update the energy taking continuous loss into account.
622 currentEnergy = energyAfterLinearLoss;
623
624 // From now on, use the track that we can update below.
625 currentTrackPtr = fSubStepTrack;
626
627 fSubStepDynamicParticle->SetKineticEnergy(currentEnergy);
628 fSubStepDynamicParticle->SetMomentumDirection(fTransportEndMomentumDir);
629 fSubStepTrack->SetPosition(fTransportEndPosition);
630
631 G4StepPoint& subPreStepPoint = *fSubStep->GetPreStepPoint();
632 subPreStepPoint.SetMaterialCutsCouple(couple);
633 subPreStepPoint.SetPosition(fTransportEndPosition);
634 subPreStepPoint.SetSafety(currentSafety);
635 subPreStepPoint.SetStepStatus(fAlongStepDoItProc);
636 }
637 firstStep = false;
638 } while (continueStepping);
639
640 // Note: currentEnergy is only updated if continueStepping is true.
641 // In case field propagation changed the energy, this flag is
642 // immediately set to false and currentEnergy is still equal to the
643 // initial kinetic energy stored in ekin.
644 if (currentEnergy != ekin) {
645 // If field propagation didn't change the energy and we potentially
646 // did multiple steps, reset the energy that G4Transportation will
647 // propose to not subtract the energy loss twice.
648 fTransportEndKineticEnergy = ekin;
649 }
650
651 fParticleChange.ProposeTrueStepLength(totalStepLength);
652
653 // Inform G4Transportation that the momentum might have changed due
654 // to scattering, even if there is no field.
655 fMomentumChanged = true;
656
657 return totalStepLength;
658 }
659 }
660 break;
661 }
662 }
663
664 // If we get here, no scattering has happened.
665 return G4Transportation::AlongStepGetPhysicalInteractionLength(
666 track, previousStepSize, currentMinimumStep, proposedSafety, selection);
667 }
668
669 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
670