G4IonFluctuations Class Reference

#include <G4IonFluctuations.hh>

Inheritance diagram for G4IonFluctuations:

Collaboration diagram for G4IonFluctuations:

Public Member Functions
	G4IonFluctuations (const G4String &nam="IonFluc")
virtual	~G4IonFluctuations ()
G4double	SampleFluctuations (const G4MaterialCutsCouple *, const G4DynamicParticle *, G4double tmax, G4double length, G4double meanLoss)
G4double	Dispersion (const G4Material *, const G4DynamicParticle *, G4double tmax, G4double length)
void	InitialiseMe (const G4ParticleDefinition *)
void	SetParticleAndCharge (const G4ParticleDefinition *, G4double q2)
Public Member Functions inherited from G4VEmFluctuationModel
	G4VEmFluctuationModel (const G4String &nam)
virtual	~G4VEmFluctuationModel ()
const G4String &	GetName () const

Private Member Functions
G4double	Factor (const G4Material *, G4double Zeff)
G4double	RelativisticFactor (const G4Material *, G4double Zeff)
G4IonFluctuations &	operator= (const G4IonFluctuations &right)
	G4IonFluctuations (const G4IonFluctuations &)

Private Attributes
G4UniversalFluctuation	uniFluct
const G4ParticleDefinition *	particle
G4Pow *	g4pow
G4double	particleMass
G4double	charge
G4double	chargeSquare
G4double	effChargeSquare
G4double	parameter
G4double	minNumberInteractionsBohr
G4double	theBohrBeta2
G4double	minFraction
G4double	xmin
G4double	minLoss
G4double	kineticEnergy
G4double	beta2

Detailed Description

Definition at line 61 of file G4IonFluctuations.hh.

Constructor & Destructor Documentation

G4IonFluctuations() [1/2]

G4IonFluctuations::G4IonFluctuations

(

const G4String &

nam = "IonFluc"

)

Definition at line 73 of file G4IonFluctuations.cc.

  : G4VEmFluctuationModel(nam),
    particle(0),
    particleMass(proton_mass_c2),
    charge(1.0),
    chargeSquare(1.0),
    effChargeSquare(1.0),
    parameter(10.0*CLHEP::MeV/CLHEP::proton_mass_c2),
    minNumberInteractionsBohr(0.0),
    theBohrBeta2(50.0*keV/CLHEP::proton_mass_c2),
    minFraction(0.2),
    xmin(0.2),
    minLoss(0.001*eV)
{
  kineticEnergy = 0.0;
  beta2 = 0.0;
  g4pow = G4Pow::GetInstance();
}

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~G4IonFluctuations()

G4IonFluctuations::~G4IonFluctuations ( )

virtual

Definition at line 94 of file G4IonFluctuations.cc.

{}

G4IonFluctuations() [2/2]

G4IonFluctuations::G4IonFluctuations ( const G4IonFluctuations &  )

private

Member Function Documentation

Dispersion()

G4double G4IonFluctuations::Dispersion ( const G4Material *  material, const G4DynamicParticle *  dp, G4double  tmax, G4double  length  )

virtual

Implements G4VEmFluctuationModel.

Definition at line 179 of file G4IonFluctuations.cc.

{
  kineticEnergy = dp->GetKineticEnergy();
  G4double etot = kineticEnergy + particleMass;
  beta2 = kineticEnergy*(kineticEnergy + 2.*particleMass)/(etot*etot);

  G4double electronDensity = material->GetElectronDensity();

  /*
  G4cout << "e= " <<  kineticEnergy << " m= " << particleMass
     << " tmax= " << tmax << " l= " << length 
     << " q^2= " << effChargeSquare << " beta2=" << beta2<< G4endl;
  */
  G4double siga = (1. - beta2*0.5)*tmax*length*electronDensity*
    twopi_mc2_rcl2*chargeSquare/beta2;

  // Low velocity - additional ion charge fluctuations according to
  // Q.Yang et al., NIM B61(1991)149-155.
  //G4cout << "sigE= " << sqrt(siga) << " charge= " << charge <<G4endl;

  G4double Z = material->GetIonisation()->GetZeffective();
 
  G4double fac = Factor(material, Z);

  // heavy ion correction
  //  G4double f1 = 1.065e-4*chargeSquare;
  //  if(beta2 > theBohrBeta2)  f1/= beta2;
  //  else                      f1/= theBohrBeta2;
  //  if(f1 > 2.5) f1 = 2.5;
  //  fac *= (1.0 + f1);

  // taking into account the cut
  G4double fac_cut = 1.0 + (fac - 1.0)*2.0*electron_mass_c2*beta2
    /(tmax*(1.0 - beta2));
  if(fac_cut > 0.01 && fac > 0.01) {
    siga *= fac_cut;
  }

  //G4cout << "siga(keV)= " << sqrt(siga)/keV << " fac= " << fac 
  //     << "  f1= " << f1 << G4endl;

  return siga;
}

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Factor()

G4double G4IonFluctuations::Factor ( const G4Material *  material, G4double  Zeff  )

private

Definition at line 228 of file G4IonFluctuations.cc.

{
  // The aproximation of energy loss fluctuations
  // Q.Yang et al., NIM B61(1991)149-155.

  // Reduced energy in MeV/AMU
  G4double energy = kineticEnergy *amu_c2/(particleMass*MeV) ;

  // simple approximation for higher beta2
  G4double s1 = RelativisticFactor(material, Z);

  // tabulation for lower beta2
  if( beta2 < 3.0*theBohrBeta2*Z ) {

  static const G4double a[96][4] = {
 {-0.3291, -0.8312,  0.2460, -1.0220},
 {-0.5615, -0.5898,  0.5205, -0.7258},
 {-0.5280, -0.4981,  0.5519, -0.5865},
 {-0.5125, -0.4625,  0.5660, -0.5190},
 {-0.5127, -0.8595,  0.5626, -0.8721},
 {-0.5174, -1.1930,  0.5565, -1.1980},
 {-0.5179, -1.1850,  0.5560, -1.2070},
 {-0.5209, -0.9355,  0.5590, -1.0250},
 {-0.5255, -0.7766,  0.5720, -0.9412},

 {-0.5776, -0.6665,  0.6598, -0.8484},
 {-0.6013, -0.6045,  0.7321, -0.7671},
 {-0.5781, -0.5518,  0.7605, -0.6919},
 {-0.5587, -0.4981,  0.7835, -0.6195},
 {-0.5466, -0.4656,  0.7978, -0.5771},
 {-0.5406, -0.4690,  0.8031, -0.5718},
 {-0.5391, -0.5061,  0.8024, -0.5974},
 {-0.5380, -0.6483,  0.7962, -0.6970},
 {-0.5355, -0.7722,  0.7962, -0.7839},
 {-0.5329, -0.7720,  0.7988, -0.7846},

 {-0.5335, -0.7671,  0.7984, -0.7933},
 {-0.5324, -0.7612,  0.7998, -0.8031},
 {-0.5305, -0.7300,  0.8031, -0.7990},
 {-0.5307, -0.7178,  0.8049, -0.8216},
 {-0.5248, -0.6621,  0.8165, -0.7919},
 {-0.5180, -0.6502,  0.8266, -0.7986},
 {-0.5084, -0.6408,  0.8396, -0.8048},
 {-0.4967, -0.6331,  0.8549, -0.8093},
 {-0.4861, -0.6508,  0.8712, -0.8432},
 {-0.4700, -0.6186,  0.8961, -0.8132},

 {-0.4545, -0.5720,  0.9227, -0.7710},
 {-0.4404, -0.5226,  0.9481, -0.7254},
 {-0.4288, -0.4778,  0.9701, -0.6850},
 {-0.4199, -0.4425,  0.9874, -0.6539},
 {-0.4131, -0.4188,  0.9998, -0.6332},
 {-0.4089, -0.4057,  1.0070, -0.6218},
 {-0.4039, -0.3913,  1.0150, -0.6107},
 {-0.3987, -0.3698,  1.0240, -0.5938},
 {-0.3977, -0.3608,  1.0260, -0.5852},
 {-0.3972, -0.3600,  1.0260, -0.5842},

 {-0.3985, -0.3803,  1.0200, -0.6013},
 {-0.3985, -0.3979,  1.0150, -0.6168},
 {-0.3968, -0.3990,  1.0160, -0.6195},
 {-0.3971, -0.4432,  1.0050, -0.6591},
 {-0.3944, -0.4665,  1.0010, -0.6825},
 {-0.3924, -0.5109,  0.9921, -0.7235},
 {-0.3882, -0.5158,  0.9947, -0.7343},
 {-0.3838, -0.5125,  0.9999, -0.7370},
 {-0.3786, -0.4976,  1.0090, -0.7310},
 {-0.3741, -0.4738,  1.0200, -0.7155},

 {-0.3969, -0.4496,  1.0320, -0.6982},
 {-0.3663, -0.4297,  1.0430, -0.6828},
 {-0.3630, -0.4120,  1.0530, -0.6689},
 {-0.3597, -0.3964,  1.0620, -0.6564},
 {-0.3555, -0.3809,  1.0720, -0.6454},
 {-0.3525, -0.3607,  1.0820, -0.6289},
 {-0.3505, -0.3465,  1.0900, -0.6171},
 {-0.3397, -0.3570,  1.1020, -0.6384},
 {-0.3314, -0.3552,  1.1130, -0.6441},
 {-0.3235, -0.3531,  1.1230, -0.6498},

 {-0.3150, -0.3483,  1.1360, -0.6539},
 {-0.3060, -0.3441,  1.1490, -0.6593},
 {-0.2968, -0.3396,  1.1630, -0.6649},
 {-0.2935, -0.3225,  1.1760, -0.6527},
 {-0.2797, -0.3262,  1.1940, -0.6722},
 {-0.2704, -0.3202,  1.2100, -0.6770},
 {-0.2815, -0.3227,  1.2480, -0.6775},
 {-0.2880, -0.3245,  1.2810, -0.6801},
 {-0.3034, -0.3263,  1.3270, -0.6778},
 {-0.2936, -0.3215,  1.3430, -0.6835},

 {-0.3282, -0.3200,  1.3980, -0.6650},
 {-0.3260, -0.3070,  1.4090, -0.6552},
 {-0.3511, -0.3074,  1.4470, -0.6442},
 {-0.3501, -0.3064,  1.4500, -0.6442},
 {-0.3490, -0.3027,  1.4550, -0.6418},
 {-0.3487, -0.3048,  1.4570, -0.6447},
 {-0.3478, -0.3074,  1.4600, -0.6483},
 {-0.3501, -0.3283,  1.4540, -0.6669},
 {-0.3494, -0.3373,  1.4550, -0.6765},
 {-0.3485, -0.3373,  1.4570, -0.6774},

 {-0.3462, -0.3300,  1.4630, -0.6728},
 {-0.3462, -0.3225,  1.4690, -0.6662},
 {-0.3453, -0.3094,  1.4790, -0.6553},
 {-0.3844, -0.3134,  1.5240, -0.6412},
 {-0.3848, -0.3018,  1.5310, -0.6303},
 {-0.3862, -0.2955,  1.5360, -0.6237},
 {-0.4262, -0.2991,  1.5860, -0.6115},
 {-0.4278, -0.2910,  1.5900, -0.6029},
 {-0.4303, -0.2817,  1.5940, -0.5927},
 {-0.4315, -0.2719,  1.6010, -0.5829},

 {-0.4359, -0.2914,  1.6050, -0.6010},
 {-0.4365, -0.2982,  1.6080, -0.6080},
 {-0.4253, -0.3037,  1.6120, -0.6150},
 {-0.4335, -0.3245,  1.6160, -0.6377},
 {-0.4307, -0.3292,  1.6210, -0.6447},
 {-0.4284, -0.3204,  1.6290, -0.6380},
 {-0.4227, -0.3217,  1.6360, -0.6438}
    } ;

    G4int iz = G4lrint(Z) - 2;
    if( 0 > iz )      { iz = 0; }
    else if(95 < iz ) { iz = 95; }

    //    G4double ss = 1.0 + a[iz][0]*pow(energy,a[iz][1])+
    //  + a[iz][2]*pow(energy,a[iz][3]);
    G4double ss = 1.0 + a[iz][0]*g4pow->powA(energy,a[iz][1])+
      + a[iz][2]*g4pow->powA(energy,a[iz][3]);
  
    // protection for the validity range for low beta
    static const G4double slim = 0.001;
    if(ss < slim) { s1 = 1.0/slim; }
    // for high value of beta
    else if(s1*ss < 1.0) { s1 = 1.0/ss; }
  }
  G4int i = 0 ;
  G4double factor = 1.0 ;

  // The index of set of parameters i = 0 for protons(hadrons) in gases
  //                                    1 for protons(hadrons) in solids
  //                                    2 for ions in atomic gases
  //                                    3 for ions in molecular gases
  //                                    4 for ions in solids
  static const G4double b[5][4] = {
  {0.1014,  0.3700,  0.9642,  3.987},
  {0.1955,  0.6941,  2.522,   1.040},
  {0.05058, 0.08975, 0.1419, 10.80},
  {0.05009, 0.08660, 0.2751,  3.787},
  {0.01273, 0.03458, 0.3951,  3.812}
  } ;

  // protons (hadrons)
  if(1.5 > charge) {
    if( kStateGas != material->GetState() ) i = 1 ;

  // ions
  } else {

    //    factor = charge * pow(charge/Z, 0.33333333);
    factor = charge * g4pow->A13(charge/Z);

    if( kStateGas == material->GetState() ) {
      energy /= (charge * sqrt(charge)) ;

      if(1 == (material->GetNumberOfElements())) {
        i = 2 ;
      } else {
        i = 3 ;
      }

    } else {
      energy /= (charge * sqrt(charge*Z)) ;
      i = 4 ;
    }
  }

  G4double x = b[i][2];
  G4double y = energy * b[i][3];
  if(y <= 0.2) x *= (y*(1.0 - 0.5*y));
  else         x *= (1.0 - g4pow->expA(-y));
  //  else         x *= (1.0 - exp(-y));

  y = energy - b[i][1];

  G4double s2 = factor * x * b[i][0] / (y*y + x*x);
  /*  
  G4cout << "s1= " << s1 << " s2= " << s2 << " q^2= " << effChargeSquare 
     << " e= " << energy << G4endl;
  */
  return s1*effChargeSquare/chargeSquare + s2;
}

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InitialiseMe()

void G4IonFluctuations::InitialiseMe ( const G4ParticleDefinition *  part )

virtual

Reimplemented from G4VEmFluctuationModel.

Definition at line 99 of file G4IonFluctuations.cc.

{
  particle       = part;
  particleMass   = part->GetPDGMass();
  charge         = part->GetPDGCharge()/eplus;
  chargeSquare   = charge*charge;
  effChargeSquare= chargeSquare;
  uniFluct.InitialiseMe(part);
}

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operator=()

G4IonFluctuations& G4IonFluctuations::operator= ( const G4IonFluctuations &  right )

private

RelativisticFactor()

G4double G4IonFluctuations::RelativisticFactor ( const G4Material *  mat, G4double  Zeff  )

private

Definition at line 424 of file G4IonFluctuations.cc.

{
  G4double eF = mat->GetIonisation()->GetFermiEnergy();
  G4double I  = mat->GetIonisation()->GetMeanExcitationEnergy();

  // H.Geissel et al. NIM B, 195 (2002) 3.
  G4double bF2= 2.0*eF/electron_mass_c2;
  G4double f  = 0.4*(1.0 - beta2)/((1.0 - 0.5*beta2)*Z);
  if(beta2 > bF2) f *= G4Log(2.0*electron_mass_c2*beta2/I)*bF2/beta2;
  else            f *= G4Log(4.0*eF/I);

  //  G4cout << "f= " << f << " beta2= " << beta2 
  //     << " bf2= " << bF2 << " q^2= " << chargeSquare << G4endl;

  return 1.0 + f;
}

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SampleFluctuations()

G4double G4IonFluctuations::SampleFluctuations ( const G4MaterialCutsCouple *  couple, const G4DynamicParticle *  dp, G4double  tmax, G4double  length, G4double  meanLoss  )

virtual

Implements G4VEmFluctuationModel.

Definition at line 112 of file G4IonFluctuations.cc.

{
  //  G4cout << "### meanLoss= " << meanLoss << G4endl;
  if(meanLoss <= minLoss) return meanLoss;

  //G4cout << "G4IonFluctuations::SampleFluctuations E(MeV)= " 
  //     << dp->GetKineticEnergy()
  //     << "  Elim(MeV)= " << parameter*charge*particleMass << G4endl; 

  // Vavilov fluctuations
  if(dp->GetKineticEnergy() > parameter*charge*particleMass) {
    return uniFluct.SampleFluctuations(couple,dp,tmax,length,meanLoss);
  }

  const G4Material* material = couple->GetMaterial();
  G4double siga = Dispersion(material,dp,tmax,length);
  G4double loss = meanLoss;
  
  //G4cout << "### siga= " << sqrt(siga) << "  navr= " << navr << G4endl;

  // Gaussian fluctuation

  // Increase fluctuations for big fractional energy loss
  //G4cout << "siga= " << siga << G4endl;
  if ( meanLoss > minFraction*kineticEnergy ) {
    G4double gam = (kineticEnergy - meanLoss)/particleMass + 1.0;
    G4double b2  = 1.0 - 1.0/(gam*gam);
    if(b2 < xmin*beta2) b2 = xmin*beta2;
    G4double x   = b2/beta2;
    G4double x3  = 1.0/(x*x*x);
    siga *= 0.25*(1.0 + x)*(x3 + (1.0/b2 - 0.5)/(1.0/beta2 - 0.5) );
  }
  siga = sqrt(siga);
  G4double sn = meanLoss/siga;
  G4double twomeanLoss = meanLoss + meanLoss;
  //  G4cout << "siga= " << siga << "  sn= " << sn << G4endl;
  
  CLHEP::HepRandomEngine* rndmEngine = G4Random::getTheEngine();
  // thick target case  
  if (sn >= 2.0) {

    do {
      loss = G4RandGauss::shoot(rndmEngine,meanLoss,siga);
      // Loop checking, 03-Aug-2015, Vladimir Ivanchenko
    } while (0.0 > loss || twomeanLoss < loss);

    // Gamma distribution
  } else if(sn > 0.1) {

    G4double neff = sn*sn;
    loss = meanLoss*G4RandGamma::shoot(rndmEngine,neff,1.0)/neff;

    // uniform distribution for very small steps
  } else {
    loss = twomeanLoss*rndmEngine->flat();
  }

  //G4cout << "meanLoss= " << meanLoss << " loss= " << loss << G4endl;
  return loss;
}

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SetParticleAndCharge()

void G4IonFluctuations::SetParticleAndCharge ( const G4ParticleDefinition *  part, G4double  q2  )

virtual

Reimplemented from G4VEmFluctuationModel.

Definition at line 444 of file G4IonFluctuations.cc.

{
  if(part != particle) {
    particle       = part;
    particleMass   = part->GetPDGMass();
    charge         = part->GetPDGCharge()/eplus;
    chargeSquare   = charge*charge;
  }
  effChargeSquare  = q2;
  uniFluct.SetParticleAndCharge(part, q2);
}

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Member Data Documentation

beta2

G4double G4IonFluctuations::beta2

private

Definition at line 117 of file G4IonFluctuations.hh.

charge

G4double G4IonFluctuations::charge

private

Definition at line 104 of file G4IonFluctuations.hh.

chargeSquare

G4double G4IonFluctuations::chargeSquare

private

Definition at line 105 of file G4IonFluctuations.hh.

effChargeSquare

G4double G4IonFluctuations::effChargeSquare

private

Definition at line 106 of file G4IonFluctuations.hh.

g4pow

G4Pow* G4IonFluctuations::g4pow

private

Definition at line 101 of file G4IonFluctuations.hh.

kineticEnergy

G4double G4IonFluctuations::kineticEnergy

private

Definition at line 116 of file G4IonFluctuations.hh.

minFraction

G4double G4IonFluctuations::minFraction

private

Definition at line 112 of file G4IonFluctuations.hh.

minLoss

G4double G4IonFluctuations::minLoss

private

Definition at line 114 of file G4IonFluctuations.hh.

minNumberInteractionsBohr

G4double G4IonFluctuations::minNumberInteractionsBohr

private

Definition at line 110 of file G4IonFluctuations.hh.

parameter

G4double G4IonFluctuations::parameter

private

Definition at line 109 of file G4IonFluctuations.hh.

particle

const G4ParticleDefinition* G4IonFluctuations::particle

private

Definition at line 99 of file G4IonFluctuations.hh.

particleMass

G4double G4IonFluctuations::particleMass

private

Definition at line 103 of file G4IonFluctuations.hh.

theBohrBeta2

G4double G4IonFluctuations::theBohrBeta2

private

Definition at line 111 of file G4IonFluctuations.hh.

uniFluct

G4UniversalFluctuation G4IonFluctuations::uniFluct

private

Definition at line 98 of file G4IonFluctuations.hh.

xmin

G4double G4IonFluctuations::xmin

private

Definition at line 113 of file G4IonFluctuations.hh.

---

The documentation for this class was generated from the following files:

• G4IonFluctuations.hh
• G4IonFluctuations.cc