G4LindhardSorensenIonModel.cc

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// $Id: G4LindhardSorensenIonModel.cc 108805 2018-03-07 18:58:45Z vnivanch $
//
// -------------------------------------------------------------------
//
// GEANT4 Class header file
//
//
// File name:     G4LindhardSorensenIonModel
//
// Author:        Alexander Bagulya & Vladimir Ivanchenko
//
// Creation date: 16.04.2018
//
//
// -------------------------------------------------------------------
//


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#include "G4LindhardSorensenIonModel.hh"
#include "Randomize.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "G4Electron.hh"
#include "G4LossTableManager.hh"
#include "G4EmCorrections.hh"
#include "G4ParticleChangeForLoss.hh"
#include "G4Log.hh"
#include "G4DeltaAngle.hh"
#include "G4LindhardSorensenData.hh"

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using namespace std;

G4LindhardSorensenData* G4LindhardSorensenIonModel::lsdata = nullptr;

G4LindhardSorensenIonModel::G4LindhardSorensenIonModel(const G4ParticleDefinition*, 
                                                       const G4String& nam)
  : G4VEmModel(nam),
    particle(nullptr),
    tlimit(DBL_MAX),
    twoln10(2.0*G4Log(10.0))
{
  fParticleChange = nullptr;
  theElectron = G4Electron::Electron();
  SetParticle(theElectron);
  corr = G4LossTableManager::Instance()->EmCorrections();  
  nist = G4NistManager::Instance();
  SetLowEnergyLimit(2.0*MeV);
}

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G4LindhardSorensenIonModel::~G4LindhardSorensenIonModel()
{}

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void G4LindhardSorensenIonModel::Initialise(const G4ParticleDefinition* p,
                                            const G4DataVector&)
{
  SetParticle(p);

  //G4cout << "G4LindhardSorensenIonModel::Initialise for " << p->GetParticleName()
  //         << G4endl;

  // always false before the run
  SetDeexcitationFlag(false);

  if(nullptr == fParticleChange) {
    fParticleChange = GetParticleChangeForLoss();
    if(UseAngularGeneratorFlag() && !GetAngularDistribution()) {
      SetAngularDistribution(new G4DeltaAngle());
    }
  }
  if(IsMaster() && !lsdata) { 
    lsdata = new G4LindhardSorensenData();
  }
}

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G4double 
G4LindhardSorensenIonModel::GetChargeSquareRatio(const G4ParticleDefinition*,
                                                 const G4Material*,
                                                 G4double)
{
  return chargeSquare;
}

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G4double 
G4LindhardSorensenIonModel::GetParticleCharge(const G4ParticleDefinition*,
                                              const G4Material*,
                                              G4double)
{
  return charge;
}

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void G4LindhardSorensenIonModel::SetupParameters()
{
  mass = particle->GetPDGMass();
  spin = particle->GetPDGSpin();
  charge = particle->GetPDGCharge()*inveplus;
  Zin = G4lrint(charge);
  chargeSquare = charge*charge;
  ratio = electron_mass_c2/mass;
  static const G4double aMag = 1./(0.5*eplus*hbar_Planck*c_squared);
  G4double magmom = particle->GetPDGMagneticMoment()*mass*aMag;
  magMoment2 = magmom*magmom - 1.0;
  if(Zin <= 1) {
    formfact = (spin == 0.0 && mass < GeV) ? 1.181e-6 : 1.548e-6; 
  } else {
    G4double x = nist->GetA27(Zin);
    formfact = 3.969e-6*x*x;
  }
  tlimit = std::sqrt(0.414/formfact +
         electron_mass_c2*electron_mass_c2) - electron_mass_c2;
}

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G4double G4LindhardSorensenIonModel::MinEnergyCut(const G4ParticleDefinition*,
                                         const G4MaterialCutsCouple* couple)
{
  return couple->GetMaterial()->GetIonisation()->GetMeanExcitationEnergy();
}

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G4double 
G4LindhardSorensenIonModel::ComputeCrossSectionPerElectron(
                                                  const G4ParticleDefinition* p,
                                                  G4double kineticEnergy,
                                                  G4double cutEnergy,
                                                  G4double maxKinEnergy)        
{
  G4double cross = 0.0;
  G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
  G4double maxEnergy = std::min(tmax,maxKinEnergy);
  if(cutEnergy < maxEnergy) {

    G4double totEnergy = kineticEnergy + mass;
    G4double energy2   = totEnergy*totEnergy;
    G4double beta2     = kineticEnergy*(kineticEnergy + 2.0*mass)/energy2;

    cross = (maxEnergy - cutEnergy)/(cutEnergy*maxEnergy) 
      - beta2*G4Log(maxEnergy/cutEnergy)/tmax;

    // +term for spin=1/2 particle
    if( 0.0 < spin ) { cross += 0.5*(maxEnergy - cutEnergy)/energy2; }

    cross *= twopi_mc2_rcl2*chargeSquare/beta2;
  }
  
   // G4cout << "BB: e= " << kineticEnergy << " tmin= " << cutEnergy 
   //        << " tmax= " << tmax << " cross= " << cross << G4endl;
  
  return cross;
}

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G4double G4LindhardSorensenIonModel::ComputeCrossSectionPerAtom(
                                           const G4ParticleDefinition* p,
                                                 G4double kineticEnergy,
                                                 G4double Z, G4double,
                                                 G4double cutEnergy,
                                                 G4double maxEnergy)
{
  G4double cross = Z*ComputeCrossSectionPerElectron
                                         (p,kineticEnergy,cutEnergy,maxEnergy);
  return cross;
}

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G4double G4LindhardSorensenIonModel::CrossSectionPerVolume(
                                           const G4Material* material,
                                           const G4ParticleDefinition* p,
                                                 G4double kineticEnergy,
                                                 G4double cutEnergy,
                                                 G4double maxEnergy)
{
  G4double eDensity = material->GetElectronDensity();
  G4double cross = eDensity*ComputeCrossSectionPerElectron
                                         (p,kineticEnergy,cutEnergy,maxEnergy);
  return cross;
}

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G4double 
G4LindhardSorensenIonModel::ComputeDEDXPerVolume(const G4Material* material,
                                                 const G4ParticleDefinition* p,
                                                 G4double kineticEnergy,
                                                 G4double cut)
{
  G4double tmax      = MaxSecondaryEnergy(p, kineticEnergy);
  G4double cutEnergy = std::min(cut,tmax);

  G4double tau   = kineticEnergy/mass;
  G4double gam   = tau + 1.0;
  G4double bg2   = tau * (tau+2.0);
  G4double beta2 = bg2/(gam*gam);

  G4double eexc  = material->GetIonisation()->GetMeanExcitationEnergy();
  G4double eexc2 = eexc*eexc;

  G4double eDensity = material->GetElectronDensity();

  G4double dedx = G4Log(2.0*electron_mass_c2*bg2*cutEnergy/eexc2)
                - (1.0 + cutEnergy/tmax)*beta2;

  if(0.0 < spin) {
    G4double del = 0.5*cutEnergy/(kineticEnergy + mass);
    dedx += del*del;
  }

  // density correction
  G4double x = G4Log(bg2)/twoln10;
  dedx -= material->GetIonisation()->DensityCorrection(x);

  // shell correction
  dedx -= 2.0*corr->ShellCorrection(p,material,kineticEnergy);

  //High order correction different for hadrons and ions
  dedx += 2.0*corr->BarkasCorrection(p,material,kineticEnergy);
  dedx = std::max(dedx, 0.0); 

  // now compute the total ionization loss
  dedx *= twopi_mc2_rcl2*chargeSquare*eDensity/beta2;

  //G4cout << "E(MeV)= " << kineticEnergy/MeV << " dedx= " << dedx 
  //         << "  " << material->GetName() << G4endl;

  return dedx;
}

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void 
G4LindhardSorensenIonModel::CorrectionsAlongStep(const G4MaterialCutsCouple* couple,
                                                 const G4DynamicParticle* dp,
                                                 G4double& eloss,
                                                 G4double&,
                                                 G4double length)
{
  const G4ParticleDefinition* p = dp->GetDefinition();
  SetParticle(p);
  G4double eDensity = couple->GetMaterial()->GetElectronDensity();
  G4double preKinEnergy = dp->GetKineticEnergy();
  G4double e = preKinEnergy - eloss*0.5;
  GetModelOfFluctuations()->SetParticleAndCharge(p, chargeSquare);

  G4double tau   = e/mass;
  G4double gam   = tau + 1.0;
  G4double beta2 = tau * (tau+2.0)/(gam*gam);
  G4double deltaL0 = 
    2.0*corr->BarkasCorrection (p, couple->GetMaterial(), e)*(charge-1.)/charge;
  G4double deltaL = lsdata->GetDeltaL(Zin, tau); 

  G4double elossnew = 
    eloss + twopi_mc2_rcl2*chargeSquare*eDensity*(deltaL+deltaL0)*length/beta2;
  /*
  G4cout << "G4LindhardSorensenIonModel::CorrectionsAlongStep: E(GeV)= " 
         << preKinEnergy/GeV << " eloss(MeV)= " << eloss
   << " L= " << eloss*beta2/(twopi_mc2_rcl2*chargeSquare*eDensity*length)
   << " dL0= " << deltaL0
   << " dL= " << deltaL << G4endl;
  */
  if(elossnew > preKinEnergy)   { elossnew = preKinEnergy; }
  else if(elossnew < 0.0)       { elossnew = eloss*0.5; }

  eloss = elossnew;
}

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void G4LindhardSorensenIonModel::SampleSecondaries(
                                          vector<G4DynamicParticle*>* vdp,
                                          const G4MaterialCutsCouple* couple,
                                          const G4DynamicParticle* dp,
                                          G4double minKinEnergy,
                                          G4double maxEnergy)
{
  G4double kineticEnergy = dp->GetKineticEnergy();
  G4double tmax = MaxSecondaryEnergy(dp->GetDefinition(),kineticEnergy);

  G4double maxKinEnergy = std::min(maxEnergy,tmax);
  if(minKinEnergy >= maxKinEnergy) { return; }

  //G4cout << "G4LindhardSorensenIonModel::SampleSecondaries Emin= " << minKinEnergy
  //         << " Emax= " << maxKinEnergy << G4endl;

  G4double totEnergy     = kineticEnergy + mass;
  G4double etot2         = totEnergy*totEnergy;
  G4double beta2         = kineticEnergy*(kineticEnergy + 2.0*mass)/etot2;

  G4double deltaKinEnergy, f; 
  G4double f1 = 0.0;
  G4double fmax = 1.0;
  if( 0.0 < spin ) { fmax += 0.5*maxKinEnergy*maxKinEnergy/etot2; }

  CLHEP::HepRandomEngine* rndmEngineMod = G4Random::getTheEngine();
  G4double rndm[2];

  // sampling without nuclear size effect
  do {
    rndmEngineMod->flatArray(2, rndm);
    deltaKinEnergy = minKinEnergy*maxKinEnergy
                    /(minKinEnergy*(1.0 - rndm[0]) + maxKinEnergy*rndm[0]);

    f = 1.0 - beta2*deltaKinEnergy/tmax;
    if( 0.0 < spin ) {
      f1 = 0.5*deltaKinEnergy*deltaKinEnergy/etot2;
      f += f1;
    }

    // Loop checking, 03-Aug-2015, Vladimir Ivanchenko
  } while( fmax*rndm[1] > f);

  // projectile formfactor - suppresion of high energy
  // delta-electron production at high energy
  
  G4double x = formfact*deltaKinEnergy*(deltaKinEnergy + 2*electron_mass_c2);
  if(x > 1.e-6) {

    G4double x1 = 1.0 + x;
    G4double grej  = 1.0/(x1*x1);
    if( 0.0 < spin ) {
      G4double x2 = 0.5*electron_mass_c2*deltaKinEnergy/(mass*mass);
      grej *= (1.0 + magMoment2*(x2 - f1/f)/(1.0 + x2));
    }
    if(grej > 1.1) {
      G4cout << "### G4LindhardSorensenIonModel WARNING: grej= " << grej
             << "  " << dp->GetDefinition()->GetParticleName()
             << " Ekin(MeV)= " <<  kineticEnergy
             << " delEkin(MeV)= " << deltaKinEnergy
             << G4endl;
    }
    if(rndmEngineMod->flat() > grej) { return; }
  }

  G4ThreeVector deltaDirection;

  if(UseAngularGeneratorFlag()) {

    const G4Material* mat =  couple->GetMaterial();
    G4int Z = SelectRandomAtomNumber(mat);

    deltaDirection = 
      GetAngularDistribution()->SampleDirection(dp, deltaKinEnergy, Z, mat);

  } else {
 
    G4double deltaMomentum =
      sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
    G4double cost = deltaKinEnergy * (totEnergy + electron_mass_c2) /
      (deltaMomentum * dp->GetTotalMomentum());
    if(cost > 1.0) { cost = 1.0; }
    G4double sint = sqrt((1.0 - cost)*(1.0 + cost));

    G4double phi = twopi*rndmEngineMod->flat();

    deltaDirection.set(sint*cos(phi),sint*sin(phi), cost) ;
    deltaDirection.rotateUz(dp->GetMomentumDirection());
  }  
  /*
    G4cout << "### G4LindhardSorensenIonModel " 
           << dp->GetDefinition()->GetParticleName()
           << " Ekin(MeV)= " <<  kineticEnergy
           << " delEkin(MeV)= " << deltaKinEnergy
           << " tmin(MeV)= " << minKinEnergy
           << " tmax(MeV)= " << maxKinEnergy
           << " dir= " << dp->GetMomentumDirection()
           << " dirDelta= " << deltaDirection
           << G4endl;
  */
  // create G4DynamicParticle object for delta ray
  G4DynamicParticle* delta = 
    new G4DynamicParticle(theElectron,deltaDirection,deltaKinEnergy);

  vdp->push_back(delta);

  // Change kinematics of primary particle
  kineticEnergy -= deltaKinEnergy;
  G4ThreeVector finalP = dp->GetMomentum() - delta->GetMomentum();
  finalP               = finalP.unit();
  
  fParticleChange->SetProposedKineticEnergy(kineticEnergy);
  fParticleChange->SetProposedMomentumDirection(finalP);
}

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G4double 
G4LindhardSorensenIonModel::MaxSecondaryEnergy(const G4ParticleDefinition* pd,
                                               G4double kinEnergy) 
{
  // here particle type is checked for any method
  SetParticle(pd);
  G4double tau  = kinEnergy/mass;
  G4double tmax = 2.0*electron_mass_c2*tau*(tau + 2.) /
                  (1. + 2.0*(tau + 1.)*ratio + ratio*ratio);
  return std::min(tmax,tlimit);
}

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