G4StatMFMicroCanonical.cc

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// Hadronic Process: Nuclear De-excitations
// by V. Lara
 
#include <numeric>
 
#include "G4StatMFMicroCanonical.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "G4HadronicException.hh"
#include "G4Pow.hh"
 
// constructor
G4StatMFMicroCanonical::G4StatMFMicroCanonical(G4Fragment const & theFragment) 
{
  // Perform class initialization
  Initialize(theFragment);
}
 
// destructor
G4StatMFMicroCanonical::~G4StatMFMicroCanonical() 
{
  // garbage collection
  if (!_ThePartitionManagerVector.empty()) {
    std::for_each(_ThePartitionManagerVector.begin(),
            _ThePartitionManagerVector.end(),
            DeleteFragment());
  }
}
 
void G4StatMFMicroCanonical::Initialize(const G4Fragment & theFragment) 
{
  
  std::vector<G4StatMFMicroManager*>::iterator it;
 
  // Excitation Energy 
  G4double U = theFragment.GetExcitationEnergy();
 
  G4int A = theFragment.GetA_asInt();
  G4int Z = theFragment.GetZ_asInt();
  G4double x = 1.0 - 2.0*Z/G4double(A);
  G4Pow* g4calc = G4Pow::GetInstance();
    
  // Configuration temperature
  G4double TConfiguration = std::sqrt(8.0*U/G4double(A));
  
  // Free internal energy at Temperature T = 0
  __FreeInternalE0 = A*( 
            // Volume term (for T = 0)
            -G4StatMFParameters::GetE0() +  
            // Symmetry term
            G4StatMFParameters::GetGamma0()*x*x 
            ) + 
    // Surface term (for T = 0)
    G4StatMFParameters::GetBeta0()*g4calc->Z23(A) + 
    // Coulomb term 
    elm_coupling*0.6*Z*Z/(G4StatMFParameters::Getr0()*g4calc->Z13(A));
  
  // Statistical weight
  G4double W = 0.0;
  
  // Mean breakup multiplicity
  __MeanMultiplicity = 0.0;
  
  // Mean channel temperature
  __MeanTemperature = 0.0;
  
  // Mean channel entropy
  __MeanEntropy = 0.0;
  
  // Calculate entropy of compound nucleus
  G4double SCompoundNucleus = CalcEntropyOfCompoundNucleus(theFragment,TConfiguration);
  
  // Statistical weight of compound nucleus
  _WCompoundNucleus = 1.0; 
  
  W += _WCompoundNucleus;
    
  // Maximal fragment multiplicity allowed in direct simulation
  G4int MaxMult = G4StatMFMicroCanonical::MaxAllowedMultiplicity;
  if (A > 110) MaxMult -= 1;
  
  for (G4int im = 2; im <= MaxMult; im++) {
    G4StatMFMicroManager * aMicroManager = 
      new G4StatMFMicroManager(theFragment,im,__FreeInternalE0,SCompoundNucleus);
    _ThePartitionManagerVector.push_back(aMicroManager);
  }
  
  // W is the total probability
  W = std::accumulate(_ThePartitionManagerVector.begin(),
              _ThePartitionManagerVector.end(),
              W, [](const G4double& running_total,
                            G4StatMFMicroManager*& manager)
                         {
                   return running_total + manager->GetProbability();
                 } );
  
  // Normalization of statistical weights
  for (it =  _ThePartitionManagerVector.begin(); it !=  _ThePartitionManagerVector.end(); ++it) 
    {
      (*it)->Normalize(W);
    }
 
  _WCompoundNucleus /= W;
  
  __MeanMultiplicity += 1.0 * _WCompoundNucleus;
  __MeanTemperature += TConfiguration * _WCompoundNucleus;
  __MeanEntropy += SCompoundNucleus * _WCompoundNucleus;
  
  for (it =  _ThePartitionManagerVector.begin(); it !=  _ThePartitionManagerVector.end(); ++it) 
    {
      __MeanMultiplicity += (*it)->GetMeanMultiplicity();
      __MeanTemperature += (*it)->GetMeanTemperature();
      __MeanEntropy += (*it)->GetMeanEntropy();
    }
  
  return;
}
 
G4double G4StatMFMicroCanonical::CalcFreeInternalEnergy(const G4Fragment & theFragment, 
                            G4double T)
{
  G4int A = theFragment.GetA_asInt();
  G4int Z = theFragment.GetZ_asInt();
  G4double A13 = G4Pow::GetInstance()->Z13(A);
  
  G4double InvLevelDensityPar = G4StatMFParameters::GetEpsilon0()
    *(1.0 + 3.0/G4double(A-1));
  
  G4double VolumeTerm = (-G4StatMFParameters::GetE0()+T*T/InvLevelDensityPar)*A;
  
  G4double SymmetryTerm = G4StatMFParameters::GetGamma0()
    *(A - 2*Z)*(A - 2*Z)/G4double(A);
  
  G4double SurfaceTerm = (G4StatMFParameters::Beta(T)
              - T*G4StatMFParameters::DBetaDT(T))*A13*A13;
  
  G4double CoulombTerm = elm_coupling*0.6*Z*Z/(G4StatMFParameters::Getr0()*A13);
  
  return VolumeTerm + SymmetryTerm + SurfaceTerm + CoulombTerm;
}
 
G4double 
G4StatMFMicroCanonical::CalcEntropyOfCompoundNucleus(const G4Fragment & theFragment,
                             G4double & TConf)
  // Calculates Temperature and Entropy of compound nucleus
{
  G4int A = theFragment.GetA_asInt();
  G4double U = theFragment.GetExcitationEnergy();
  G4double A13 = G4Pow::GetInstance()->Z13(A);
  
  G4double Ta = std::max(std::sqrt(U/(0.125*A)),0.0012*MeV); 
  G4double Tb = Ta;
  
  G4double ECompoundNucleus = CalcFreeInternalEnergy(theFragment,Ta);
  G4double Da = (U+__FreeInternalE0-ECompoundNucleus)/U;
  G4double Db = 0.0;
    
  G4double InvLevelDensity = CalcInvLevelDensity(A);
  
  // bracketing the solution
  if (Da == 0.0) {
    TConf = Ta;
    return 2*Ta*A/InvLevelDensity - G4StatMFParameters::DBetaDT(Ta)*A13*A13;
  } else if (Da < 0.0) {
    do {
      Tb -= 0.5*Tb;
      ECompoundNucleus = CalcFreeInternalEnergy(theFragment,Tb);
      Db = (U+__FreeInternalE0-ECompoundNucleus)/U;
    } while (Db < 0.0);
  } else {
    do {
      Tb += 0.5*Tb;
      ECompoundNucleus = CalcFreeInternalEnergy(theFragment,Tb);
      Db = (U+__FreeInternalE0-ECompoundNucleus)/U;
    } while (Db > 0.0);
  }
  
  G4double eps = 1.0e-14 * std::abs(Tb-Ta);
  
  for (G4int i = 0; i < 1000; i++) {
    G4double Tc = (Ta+Tb)*0.5;
    if (std::abs(Ta-Tb) <= eps) {
      TConf = Tc;
      return 2*Tc*A/InvLevelDensity - G4StatMFParameters::DBetaDT(Tc)*A13*A13;
    }
    ECompoundNucleus = CalcFreeInternalEnergy(theFragment,Tc);
    G4double Dc = (U+__FreeInternalE0-ECompoundNucleus)/U;
    
    if (Dc == 0.0) {
      TConf = Tc;
      return 2*Tc*A/InvLevelDensity - G4StatMFParameters::DBetaDT(Tc)*A13*A13;
    }
    
    if (Da*Dc < 0.0) {
      Tb = Tc;
      Db = Dc;
    } else {
      Ta = Tc;
      Da = Dc;
    } 
  }
  
  G4cout << 
    "G4StatMFMicrocanoncal::CalcEntropyOfCompoundNucleus: I can't calculate the temperature" 
     << G4endl;
  
  return 0.0;
}
 
G4StatMFChannel *  G4StatMFMicroCanonical::ChooseAandZ(const G4Fragment & theFragment)
  // Choice of fragment atomic numbers and charges 
{
  // We choose a multiplicity (1,2,3,...) and then a channel
  G4double RandNumber = G4UniformRand();
 
  if (RandNumber < _WCompoundNucleus) { 
    
    G4StatMFChannel * aChannel = new G4StatMFChannel;
    aChannel->CreateFragment(theFragment.GetA_asInt(),theFragment.GetZ_asInt());
    return aChannel;
    
  } else {
    
    G4double AccumWeight = _WCompoundNucleus;
    std::vector<G4StatMFMicroManager*>::iterator it;
    for (it = _ThePartitionManagerVector.begin(); it != _ThePartitionManagerVector.end(); ++it) {
      AccumWeight += (*it)->GetProbability();
      if (RandNumber < AccumWeight) {
    return (*it)->ChooseChannel(theFragment.GetA_asInt(),theFragment.GetZ_asInt(),__MeanTemperature);
      }
    }
    throw G4HadronicException(__FILE__, __LINE__, "G4StatMFMicroCanonical::ChooseAandZ: wrong normalization!");
  }
 
  return 0; 
}
 
G4double G4StatMFMicroCanonical::CalcInvLevelDensity(G4int anA)
{
  G4double res = 0.0;
  if (anA > 1) {
    res = G4StatMFParameters::GetEpsilon0()*(1.0+3.0/(anA - 1.0));
  }
  return res;
}