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25 //
26 // G4IonCoulombCrossSection.cc
27 //-------------------------------------------------------------------
28 //
29 // GEANT4 Class header file
30 //
31 // File name: G4IonCoulombCrossSection
32 //
33 // Author: Cristina Consolandi
34 //
35 // Creation date: 05.10.2010 from G4eCoulombScatteringModel
36 //
37 // Class Description:
38 // Computation of Screen-Coulomb Cross Section
39 // for protons, alpha and heavy Ions
40 //
41 //
42 // Reference:
43 // M.J. Boschini et al. "Nuclear and Non-Ionizing Energy-Loss
44 // for Coulomb Scattered Particles from Low Energy up to Relativistic
45 // Regime in Space Radiation Environment"
46 // Accepted for publication in the Proceedings of the ICATPP Conference
47 // on Cosmic Rays for Particle and Astroparticle Physics, Villa Olmo, 7-8
48 // October, 2010, to be published by World Scientific (Singapore).
49 //
50 // Available for downloading at:
51 // http://arxiv.org/abs/1011.4822
52 //
53 // -------------------------------------------------------------------
54 //
55 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
56
57 #include "G4IonCoulombCrossSection.hh"
58 #include "G4PhysicalConstants.hh"
59 #include "Randomize.hh"
60 #include "G4Proton.hh"
61 #include "G4Exp.hh"
62 #include "G4Log.hh"
63
64 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
65
66 using namespace std;
67
68 const G4double a0 = CLHEP::electron_mass_c2/0.88534;
69
70 G4IonCoulombCrossSection::G4IonCoulombCrossSection():
71 cosThetaMin(1.0),
72 cosThetaMax(-1.0),
73 alpha2(fine_structure_const*fine_structure_const)
74 {
75 fNistManager = G4NistManager::Instance();
76 fG4pow = G4Pow::GetInstance();
77 theProton = G4Proton::Proton();
78 particle = nullptr;
79
80 G4double p0 = electron_mass_c2*classic_electr_radius;
81 coeff = twopi*p0*p0;
82
83 cosTetMinNuc=0;
84 cosTetMaxNuc=0;
85 nucXSection =0;
86
87 chargeSquare = spin = mass = 0.0;
88 tkinLab = momLab2 = invbetaLab2 = tkin = mom2 = invbeta2 = 0.0;
89
90 targetZ = targetMass = screenZ = ScreenRSquare = etag = 0.0;
91 }
92
93 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
94
95 void G4IonCoulombCrossSection::Initialise(const G4ParticleDefinition* p,
96 G4double CosThetaLim)
97 {
98 SetupParticle(p);
99 nucXSection = tkin = targetZ = mom2 = 0.0;
100 etag = DBL_MAX;
101 particle = p;
102 cosThetaMin = CosThetaLim;
103 }
104
105 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
106
107 void G4IonCoulombCrossSection::SetupKinematic(G4double ekin, G4double tmass)
108 {
109 if(ekin != tkinLab || tmass != targetMass) {
110
111 // lab
112 tkinLab = ekin;
113 momLab2 = tkinLab*(tkinLab + 2.0*mass);
114 invbetaLab2 = 1.0 + mass*mass/momLab2;
115
116 G4double etot = tkinLab + mass;
117 G4double ptot = sqrt(momLab2);
118 G4double m12 = mass*mass;
119 // relativistic reduced mass from publucation
120 // A.P. Martynenko, R.N. Faustov, Teoret. mat. Fiz. 64 (1985) 179
121
122 //incident particle & target nucleus
123 targetMass = tmass;
124 G4double Ecm=sqrt(m12 + targetMass*targetMass + 2.0*etot*targetMass);
125 G4double mu_rel=mass*targetMass/Ecm;
126 G4double momCM= ptot*targetMass/Ecm;
127 // relative system
128 mom2 = momCM*momCM;
129 invbeta2 = 1.0 + mu_rel*mu_rel/mom2;
130 tkin = momCM*sqrt(invbeta2) - mu_rel;//Ekin of mu_rel
131
132 cosTetMinNuc = cosThetaMin;
133 cosTetMaxNuc = cosThetaMax;
134 }
135 }
136
137 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
138
139 void G4IonCoulombCrossSection::SetupTarget(G4double Z, G4double e,
140 G4int)
141 {
142 if(Z != targetZ || e != etag) {
143 etag = e;
144 targetZ = Z;
145 G4int iz= G4lrint(Z);
146
147 SetScreenRSquare(iz);
148 screenZ = 0;
149 screenZ = ScreenRSquare/mom2;
150 //heavycorr = 0;
151 // G4cout<< "heavycorr "<<heavycorr<<G4endl;
152
153 G4double corr=5.*twopi*Z*std::sqrt(chargeSquare*alpha2);
154 corr=G4Exp(G4Log(corr)*0.04);
155 screenZ *=0.5*(1.13 + corr*3.76*Z*Z*chargeSquare*invbeta2*alpha2);
156 // G4cout<<" heavycorr Z e corr....2As "<< heavycorr << "\t"
157 // <<Z <<"\t"<<e/MeV <<"\t"<<screenZ<<G4endl;
158
159 if(1 == iz && particle == theProton && cosTetMaxNuc < 0.0) {
160 cosTetMaxNuc = 0.0;
161 }
162 }
163 }
164
165 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
166
167 void G4IonCoulombCrossSection::SetScreenRSquare(G4int iz)
168 {
169 //for proton Thomas-Fermi screening length
170 G4int Z1 = G4lrint(std::sqrt(chargeSquare));
171 G4double Z113 = fG4pow->Z13(iz);
172 G4double Z1023 = fG4pow->powZ(Z1,0.23);
173 G4double Z2023 = fG4pow->powZ(iz,0.23);
174 G4double x=a0*(Z1023+Z2023);
175
176 // Universal screening length
177 if(particle == theProton){
178 x = a0*Z113;
179 }
180
181 ScreenRSquare = alpha2*x*x;
182 }
183
184 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
185
186 G4double G4IonCoulombCrossSection::NuclearCrossSection()
187 {
188 // This method needs initialisation before be called
189 // scattering with target nucleus
190 G4double fac = coeff*targetZ*(targetZ)*chargeSquare*invbeta2/mom2;
191
192 nucXSection = 0.0;
193
194 G4double x = 1.0 - cosTetMinNuc;
195 G4double x1 = x + screenZ;
196
197 // scattering with nucleus
198 if(cosTetMaxNuc < cosTetMinNuc) {
199 nucXSection = fac*(cosTetMinNuc - cosTetMaxNuc)/
200 (x1*(1.0 - cosTetMaxNuc + screenZ));
201 }
202
203 return nucXSection;
204 }
205
206 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
207
208 G4double G4IonCoulombCrossSection::SampleCosineTheta()
209 {
210 G4double z1 = 0.0;
211 if(cosTetMaxNuc < cosTetMinNuc) {
212
213 G4double x1 = 1. - cosTetMinNuc + screenZ;
214 G4double x2 = 1. - cosTetMaxNuc + screenZ;
215 G4double dx = cosTetMinNuc - cosTetMaxNuc;
216 z1 = x1*x2/(x1 + G4UniformRand()*dx) - screenZ;
217 }
218 return z1;
219 }
220
221 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
222
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