G4StatMF.cc

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// Hadronic Process: Nuclear De-excitations
// by V. Lara
 
#include "G4StatMF.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "G4Pow.hh"
#include "G4PhysicsModelCatalog.hh"
 
G4StatMF::G4StatMF()
{
  _secID = G4PhysicsModelCatalog::GetModelID("model_G4StatMF");
}
 
G4StatMF::~G4StatMF() {}
 
G4FragmentVector* G4StatMF::BreakItUp(const G4Fragment &theFragment)
{
  if (theFragment.GetExcitationEnergy() <= 0.0) {
    return nullptr;
  }
 
  // Maximun average multiplicity: M_0 = 2.6 for A ~ 200 
  // and M_0 = 3.3 for A <= 110
  G4double MaxAverageMultiplicity = 
    G4StatMFParameters::GetMaxAverageMultiplicity(theFragment.GetA_asInt());
 
    
    // We'll use two kinds of ensembles
  G4StatMFMicroCanonical * theMicrocanonicalEnsemble = 0;
  G4StatMFMacroCanonical * theMacrocanonicalEnsemble = 0;
    
  //-------------------------------------------------------
  // Direct simulation part (Microcanonical ensemble)
  //-------------------------------------------------------
  
  // Microcanonical ensemble initialization 
  theMicrocanonicalEnsemble = new G4StatMFMicroCanonical(theFragment);
 
  G4int Iterations = 0;
  G4int IterationsLimit = 100000;
  G4double Temperature = 0.0;
  
  G4bool FirstTime = true;
  G4StatMFChannel * theChannel = 0;
 
  G4bool ChannelOk;
  do {  // Try to de-excite as much as IterationLimit permits
    do {
      
      G4double theMeanMult = theMicrocanonicalEnsemble->GetMeanMultiplicity();
      if (theMeanMult <= MaxAverageMultiplicity) {
    // G4cout << "MICROCANONICAL" << G4endl;
    // Choose fragments atomic numbers and charges from direct simulation
    theChannel = theMicrocanonicalEnsemble->ChooseAandZ(theFragment);
    _theEnsemble = theMicrocanonicalEnsemble;
      } else {
    //-----------------------------------------------------
    // Non direct simulation part (Macrocanonical Ensemble)
    //-----------------------------------------------------
    if (FirstTime) {
      // Macrocanonical ensemble initialization 
      theMacrocanonicalEnsemble = new G4StatMFMacroCanonical(theFragment);
      _theEnsemble = theMacrocanonicalEnsemble;
      FirstTime = false;
    }
    // G4cout << "MACROCANONICAL" << G4endl;
    // Select calculated fragment total multiplicity, 
    // fragment atomic numbers and fragment charges.
    theChannel = theMacrocanonicalEnsemble->ChooseAandZ(theFragment);
      }
      
      ChannelOk = theChannel->CheckFragments();
      if (!ChannelOk) delete theChannel; 
      
      // Loop checking, 05-Aug-2015, Vladimir Ivanchenko
    } while (!ChannelOk);
    
    
    if (theChannel->GetMultiplicity() <= 1) {
      G4FragmentVector * theResult = new G4FragmentVector;
      theResult->push_back(new G4Fragment(theFragment));
      delete theMicrocanonicalEnsemble;
      if (theMacrocanonicalEnsemble != 0) delete theMacrocanonicalEnsemble;
      delete theChannel;
      return theResult;
    }
    
    //--------------------------------------
    // Second part of simulation procedure.
    //--------------------------------------
    
    // Find temperature of breaking channel.
    Temperature = _theEnsemble->GetMeanTemperature(); // Initial guess for Temperature 
 
    if (FindTemperatureOfBreakingChannel(theFragment,theChannel,Temperature)) break;
 
    // Do not forget to delete this unusable channel, for which we failed to find the temperature,
    // otherwise for very proton-reach nuclei it would lead to memory leak due to large 
    // number of iterations. N.B. "theChannel" is created in G4StatMFMacroCanonical::ChooseZ()
 
    // G4cout << " Iteration # " << Iterations << " Mean Temperature = " << Temperature << G4endl;    
 
    delete theChannel;    
 
    // Loop checking, 05-Aug-2015, Vladimir Ivanchenko
  } while (Iterations++ < IterationsLimit );
 
  // If Iterations >= IterationsLimit means that we couldn't solve for temperature
  if (Iterations >= IterationsLimit) 
    throw G4HadronicException(__FILE__, __LINE__, "G4StatMF::BreakItUp: Was not possible to solve for temperature of breaking channel");
 
  G4FragmentVector * theResult = theChannel->
    GetFragments(theFragment.GetA_asInt(),theFragment.GetZ_asInt(),Temperature);
    
  // ~~~~~~ Energy conservation Patch !!!!!!!!!!!!!!!!!!!!!!
  // Original nucleus 4-momentum in CM system
  G4LorentzVector InitialMomentum(theFragment.GetMomentum());
  InitialMomentum.boost(-InitialMomentum.boostVector());
  G4double ScaleFactor = 0.0;
  G4double SavedScaleFactor = 0.0;
  do {
    G4double FragmentsEnergy = 0.0;
    for (auto const & ptr : *theResult) {
      FragmentsEnergy += ptr->GetMomentum().e();
    }
    if (0.0 == FragmentsEnergy) { break; } 
    SavedScaleFactor = ScaleFactor;
    ScaleFactor = InitialMomentum.e()/FragmentsEnergy;
    G4ThreeVector ScaledMomentum(0.0,0.0,0.0);
    for (auto const & ptr : *theResult) {
      ScaledMomentum = ScaleFactor * ptr->GetMomentum().vect();
      G4double Mass = ptr->GetMomentum().mag();
      G4LorentzVector NewMomentum;
      NewMomentum.setVect(ScaledMomentum);
      NewMomentum.setE(std::sqrt(ScaledMomentum.mag2()+Mass*Mass));
      ptr->SetMomentum(NewMomentum);        
    }
    // Loop checking, 05-Aug-2015, Vladimir Ivanchenko
  } while (ScaleFactor > 1.0+1.e-5 && std::abs(ScaleFactor-SavedScaleFactor)/ScaleFactor > 1.e-10);
  // ~~~~~~ End of patch !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
  
  // Perform Lorentz boost
  G4FragmentVector::iterator i;
  for (i = theResult->begin(); i != theResult->end(); i++) {
    G4LorentzVector FourMom = (*i)->GetMomentum();
    FourMom.boost(theFragment.GetMomentum().boostVector());
    (*i)->SetMomentum(FourMom);
    (*i)->SetCreatorModelID(_secID);
  }
  
  // garbage collection
  delete theMicrocanonicalEnsemble;
  if (theMacrocanonicalEnsemble != 0) delete theMacrocanonicalEnsemble;
  delete theChannel;
  
  return theResult;
}
 
 
G4bool G4StatMF::FindTemperatureOfBreakingChannel(const G4Fragment & theFragment,
                          const G4StatMFChannel * aChannel,
                          G4double & Temperature)
  // This finds temperature of breaking channel.
{
  G4int A = theFragment.GetA_asInt();
  G4int Z = theFragment.GetZ_asInt();
  G4double U = theFragment.GetExcitationEnergy();
  
  G4double T = std::max(Temperature,0.0012*MeV);  
  G4double Ta = T;
  G4double TotalEnergy = CalcEnergy(A,Z,aChannel,T);
  
  G4double Da = (U - TotalEnergy)/U;
  G4double Db = 0.0;
  
  // bracketing the solution
  if (Da == 0.0) {
    Temperature = T;
    return true;
  } else if (Da < 0.0) {
    do {
      T *= 0.5;
      if (T < 0.001*MeV) return false;
      
      TotalEnergy = CalcEnergy(A,Z,aChannel,T);
      
      Db = (U - TotalEnergy)/U;
      // Loop checking, 05-Aug-2015, Vladimir Ivanchenko
    } while (Db < 0.0);
    
  } else {
    do {
      T *= 1.5;
      
      TotalEnergy = CalcEnergy(A,Z,aChannel,T);
      
      Db = (U - TotalEnergy)/U;
      // Loop checking, 05-Aug-2015, Vladimir Ivanchenko
    } while (Db > 0.0); 
  }
  
  G4double eps = 1.0e-14 * std::abs(T-Ta);
  //G4double eps = 1.0e-3 ;
  
  // Start the bisection method
  for (G4int j = 0; j < 1000; j++) {
    G4double Tc =  (Ta+T)*0.5;
    if (std::abs(Ta-Tc) <= eps) {
      Temperature = Tc;
      return true;
    }
    
    T = Tc;    
    TotalEnergy = CalcEnergy(A,Z,aChannel,T);
    G4double Dc = (U - TotalEnergy)/U; 
    
    if (Dc == 0.0) {
      Temperature  = Tc;
      return true;
    }
    if (Da*Dc < 0.0) {
      T  = Tc;
      Db = Dc;
    } else {
      Ta = Tc;
      Da = Dc;
    }
  }
  
  Temperature  = (Ta+T)*0.5;
  return false;
}
 
G4double G4StatMF::CalcEnergy(G4int A, G4int Z, const G4StatMFChannel * aChannel,
                  G4double T)
{
  G4double MassExcess0 = G4NucleiProperties::GetMassExcess(A,Z);
  G4double ChannelEnergy = aChannel->GetFragmentsEnergy(T);
  return -MassExcess0 + G4StatMFParameters::GetCoulomb() + ChannelEnergy;
}