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25 //
26 //
27 // -------------------------------------------------------------------
28 //
29 // GEANT4 Class file
30 //
31 //
32 // File name: G4ionEffectiveCharge
33 //
34 // Author: Vladimir Ivanchenko
35 //
36 // Creation date: 07.05.2002
37 //
38 // Modifications:
39 // 12.09.2004 Set low energy limit to 1 keV (V.Ivanchenko)
40 // 25.01.2005 Add protection - min Charge 0.1 eplus (V.Ivanchenko)
41 // 28.04.2006 Set upper energy limit to 50 MeV (V.Ivanchenko)
42 // 23.05.2006 Set upper energy limit to Z*10 MeV (V.Ivanchenko)
43 // 15.08.2006 Add protection for not defined material (V.Ivanchenko)
44 // 27-09-2007 Use Fermi energy from material, optimazed formulas (V.Ivanchenko)
45 //
46
47 // -------------------------------------------------------------------
48 //
49 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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51
52 #include "G4ionEffectiveCharge.hh"
53 #include "G4PhysicalConstants.hh"
54 #include "G4SystemOfUnits.hh"
55 #include "G4UnitsTable.hh"
56 #include "G4Material.hh"
57 #include "G4NistManager.hh"
58 #include "G4Log.hh"
59 #include "G4Exp.hh"
60 #include "G4Pow.hh"
61
62 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
63
64 G4ionEffectiveCharge::G4ionEffectiveCharge()
65 {
66 chargeCorrection = 1.0;
67 energyHighLimit = 20.0*CLHEP::MeV;
68 energyLowLimit = 1.0*CLHEP::keV;
69 energyBohr = 25.*CLHEP::keV;
70 massFactor = CLHEP::amu_c2/(CLHEP::proton_mass_c2*CLHEP::keV);
71 minCharge = 1.0;
72 lastKinEnergy = 0.0;
73 effCharge = CLHEP::eplus;
74 inveplus = 1.0/CLHEP::eplus;
75 g4calc = G4Pow::GetInstance();
76 }
77
78 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
79
80 G4double G4ionEffectiveCharge::EffectiveCharge(const G4ParticleDefinition* p,
81 const G4Material* material,
82 G4double kineticEnergy)
83 {
84 if(p == lastPart && material == lastMat && kineticEnergy == lastKinEnergy)
85 return effCharge;
86
87 lastPart = p;
88 lastMat = material;
89 lastKinEnergy = kineticEnergy;
90
91 G4double mass = p->GetPDGMass();
92 effCharge = p->GetPDGCharge();
93 G4int Zi = G4lrint(effCharge*inveplus);
94 chargeCorrection = 1.0;
95 if(Zi <= 1) { return effCharge; }
96
97 // The aproximation of ion effective charge from:
98 // J.F.Ziegler, J.P. Biersack, U. Littmark
99 // The Stopping and Range of Ions in Matter,
100 // Vol.1, Pergamon Press, 1985
101 // Fast ions or hadrons
102 G4double reducedEnergy = kineticEnergy * CLHEP::proton_mass_c2/mass;
103
104 //G4cout << "e= " << reducedEnergy << " Zi= " << Zi << " "
105 //<< material->GetName() << G4endl;
106
107 if(reducedEnergy > effCharge*energyHighLimit ) {
108 return effCharge;
109 }
110 G4double z = material->GetIonisation()->GetZeffective();
111 reducedEnergy = std::max(reducedEnergy,energyLowLimit);
112
113 // Helium ion case
114 if( Zi <= 2 ) {
115
116 static const G4double c[6] =
117 {0.2865,0.1266,-0.001429,0.02402,-0.01135,0.001475};
118
119 G4double Q = std::max(0.0,G4Log(reducedEnergy*massFactor));
120 G4double x = c[0];
121 G4double y = 1.0;
122 for (G4int i=1; i<6; ++i) {
123 y *= Q;
124 x += y * c[i] ;
125 }
126 G4double ex = (x < 0.2) ? x * (1 - 0.5*x) : 1. - G4Exp(-x);
127
128 G4double tq = 7.6 - Q;
129 G4double tq2= tq*tq;
130 G4double tt = ( 0.007 + 0.00005 * z );
131 if(tq2 < 0.2) { tt *= (1.0 - tq2 + 0.5*tq2*tq2); }
132 else { tt *= G4Exp(-tq2); }
133
134 effCharge *= (1.0 + tt) * std::sqrt(ex);
135
136 // Heavy ion case
137 } else {
138
139 G4double zi13 = g4calc->Z13(Zi);
140 G4double zi23 = zi13*zi13;
141
142 // v1 is ion velocity in vF unit
143 G4double eF = material->GetIonisation()->GetFermiEnergy();
144 G4double v1sq = reducedEnergy/eF;
145 G4double vFsq = eF/energyBohr;
146 G4double vF = std::sqrt(vFsq);
147
148 G4double y = ( v1sq > 1.0 )
149 // Faster than Fermi velocity
150 ? vF * std::sqrt(v1sq) * ( 1.0 + 0.2/v1sq ) / zi23
151 // Slower than Fermi velocity
152 : 0.692308 * vF * (1.0 + 0.666666*v1sq + v1sq*v1sq/15.0) / zi23;
153
154 G4double y3 = G4Exp(0.3*G4Log(y));
155 // G4cout<<"y= "<<y<<" y3= "<<y3<<" v1= "<<v1<<" vF= "<<vF<<G4endl;
156 G4double q = std::max(1.0 - G4Exp( 0.803*y3 - 1.3167*y3*y3 - 0.38157*y
157 - 0.008983*y*y), minCharge/effCharge);
158
159 // compute charge correction
160 G4double tq = 7.6 - G4Log(reducedEnergy/CLHEP::keV);
161 G4double tq2= tq*tq;
162 G4double sq = 1.0 + ( 0.18 + 0.0015 * z )*G4Exp(-tq2)/ (Zi*Zi);
163 // G4cout << "sq= " << sq << G4endl;
164
165 // Screen length according to
166 // J.F.Ziegler and J.M.Manoyan, The stopping of ions in compaunds,
167 // Nucl. Inst. & Meth. in Phys. Res. B35 (1988) 215-228.
168
169 G4double lambda = 10.0 * vF *g4calc->A23(1.0 - q)/ (zi13 * (6.0 + q));
170 G4double lambda2 = lambda*lambda;
171 G4double xx = (0.5/q - 0.5)*G4Log(1.0 + lambda2)/vFsq;
172
173 effCharge *= q;
174 chargeCorrection = sq * (1.0 + xx);
175 }
176 // G4cout << "G4ionEffectiveCharge: charge= " << charge << " q= " << q
177 // << " chargeCor= " << chargeCorrection
178 // << " e(MeV)= " << kineticEnergy/MeV << G4endl;
179 return effCharge;
180 }
181
182 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
183