GB05/src/GB05BOptnSplitAndKillByCrossSection.cc

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0026 //
0027 /// \file GB05BOptnSplitAndKillByCrossSection.cc
0028 /// \brief Implementation of the GB05BOptnSplitAndKillByCrossSection class
0029
0030 #include "GB05BOptnSplitAndKillByCrossSection.hh"
0031
0032 #include "Randomize.hh"
0033
0034 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0035
0036 GB05BOptnSplitAndKillByCrossSection::GB05BOptnSplitAndKillByCrossSection(G4String name)
0037   : G4VBiasingOperation(name), fParticleChange(), fInteractionLength(-1.0)
0038 {}
0039
0040 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0041
0042 GB05BOptnSplitAndKillByCrossSection::~GB05BOptnSplitAndKillByCrossSection() = default;
0043
0044 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0045
0046 G4double GB05BOptnSplitAndKillByCrossSection::DistanceToApplyOperation(const G4Track*, G4double,
0047                                                                        G4ForceCondition* condition)
0048 {
0049   *condition = NotForced;
0050
0051   // -- Sample the exponential law using the total interaction length of processes
0052   // -- to couterbalance for:
0053   G4double proposedStepLength = -std::log(G4UniformRand()) * fInteractionLength;
0054
0055   return proposedStepLength;
0056 }
0057
0058 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
0059
0060 G4VParticleChange*
0061 GB05BOptnSplitAndKillByCrossSection::GenerateBiasingFinalState(const G4Track* track, const G4Step*)
0062 {
0063   // -- This method is called if we have limited the step.
0064   // -- We hence make the splitting or killing.
0065
0066   // Get track weight:
0067   G4double initialWeight = track->GetWeight();
0068
0069   // The "particle change" is the object to be used to communicate to
0070   // the tracking the update of the primary state and/or creation
0071   // secondary tracks.
0072   fParticleChange.Initialize(*track);
0073
0074   // -- Splitting and killing factors.
0075   // -- They are taken the same, but the killing factor can be make bigger.
0076   G4double splittingFactor = 2.0;
0077   G4double killingFactor = 2.0;
0078
0079   if (track->GetMomentumDirection().z() > 0) {
0080     // -- We split if the track is moving forward:
0081
0082     // Define the tracks weight:
0083     G4double weightOfTrack = initialWeight / splittingFactor;
0084
0085     // Ask currect track weight to be changed to new value:
0086     fParticleChange.ProposeParentWeight(weightOfTrack);
0087     // Now make clones of this track (this is the actual splitting):
0088     // we will then have the primary and clone of it, hence the
0089     // splitting by a factor 2:
0090     auto clone = new G4Track(*track);
0091     clone->SetWeight(weightOfTrack);
0092     fParticleChange.AddSecondary(clone);
0093     // -- Below's call added for safety & illustration : inform particle change to not
0094     // -- modify the clone (ie : daughter) weight to male it that of the
0095     // -- primary. Here call not mandatory and both tracks have same weights.
0096     fParticleChange.SetSecondaryWeightByProcess(true);
0097   }
0098   else {
0099     // -- We apply Russian roulette if the track is moving backward:
0100
0101     // Shoot a random number (in ]0,1[ segment):
0102     G4double random = G4UniformRand();
0103     G4double killingProbability = 1.0 - 1.0 / killingFactor;
0104     if (random < killingProbability) {
0105       // We ask for the the track to be killed:
0106       fParticleChange.ProposeTrackStatus(fStopAndKill);
0107     }
0108     else {
0109       // In this case, the track survives. We change its weight
0110       // to conserve weight among killed and survival tracks:
0111       fParticleChange.ProposeParentWeight(initialWeight * killingFactor);
0112     }
0113   }
0114
0115   return &fParticleChange;
0116 }
0117
0118 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......