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25 //
26 // INCL++ intra-nuclear cascade model
27 // Alain Boudard, CEA-Saclay, France
28 // Joseph Cugnon, University of Liege, Belgium
29 // Jean-Christophe David, CEA-Saclay, France
30 // Pekka Kaitaniemi, CEA-Saclay, France, and Helsinki Institute of Physics, Finland
31 // Sylvie Leray, CEA-Saclay, France
32 // Davide Mancusi, CEA-Saclay, France
33 //
34 #define INCLXX_IN_GEANT4_MODE 1
35
36 #include "globals.hh"
37
38 /** \file G4INCLCoulombNonRelativistic.cc
39 * \brief Class for non-relativistic Coulomb distortion.
40 *
41 * \date 14 February 2011
42 * \author Davide Mancusi
43 */
44
45 #include "G4INCLCoulombNonRelativistic.hh"
46 #include "G4INCLGlobals.hh"
47
48 namespace G4INCL {
49
50 ParticleEntryAvatar *CoulombNonRelativistic::bringToSurface(Particle * const p, Nucleus * const n) const {
51 // No distortion for neutral particles
52 if(p->getZ()!=0) {
53 const G4bool success = coulombDeviation(p, n);
54 if(!success) // transparent
55 return NULL;
56 }
57
58 // Rely on the CoulombNone slave to compute the straight-line intersection
59 // and actually bring the particle to the surface of the nucleus
60 return theCoulombNoneSlave.bringToSurface(p,n);
61 }
62
63 IAvatarList CoulombNonRelativistic::bringToSurface(Cluster * const c, Nucleus * const n) const {
64 // Neutral clusters?!
65 // assert(c->getZ()>0);
66
67 // Perform the actual Coulomb deviation
68 const G4bool success = coulombDeviation(c, n);
69 if(!success) {
70 return IAvatarList();
71 }
72
73 // Rely on the CoulombNone slave to compute the straight-line intersection
74 // and actually bring the particle to the surface of the nucleus
75 return theCoulombNoneSlave.bringToSurface(c,n);
76 }
77
78 void CoulombNonRelativistic::distortOut(ParticleList const &pL,
79 Nucleus const * const nucleus) const {
80
81 for(ParticleIter particle=pL.begin(), e=pL.end(); particle!=e; ++particle) {
82
83 const G4int Z = (*particle)->getZ();
84 if(Z == 0) continue;
85
86 const G4double tcos=1.-0.000001;
87
88 const G4double et1 = PhysicalConstants::eSquared * nucleus->getZ();
89 const G4double transmissionRadius =
90 nucleus->getDensity()->getTransmissionRadius(*particle);
91
92 const ThreeVector position = (*particle)->getPosition();
93 ThreeVector momentum = (*particle)->getMomentum();
94 const G4double r = position.mag();
95 const G4double p = momentum.mag();
96 const G4double cosTheta = position.dot(momentum)/(r*p);
97 if(cosTheta < 0.999999) {
98 const G4double sinTheta = std::sqrt(1.-cosTheta*cosTheta);
99 const G4double eta = et1 * Z / (*particle)->getKineticEnergy();
100 if(eta > transmissionRadius-0.0001) {
101 // If below the Coulomb barrier, radial emission:
102 momentum = position * (p/r);
103 (*particle)->setMomentum(momentum);
104 } else {
105 const G4double b0 = 0.5 * (eta + std::sqrt(eta*eta +
106 4. * std::pow(transmissionRadius*sinTheta,2)
107 * (1.-eta/transmissionRadius)));
108 const G4double bInf = std::sqrt(b0*(b0-eta));
109 const G4double thr = std::atan(eta/(2.*bInf));
110 G4double uTemp = (1.-b0/transmissionRadius) * std::sin(thr) +
111 b0/transmissionRadius;
112 if(uTemp>tcos) uTemp=tcos;
113 const G4double thd = Math::arcCos(cosTheta)-Math::piOverTwo + thr +
114 Math::arcCos(uTemp);
115 const G4double c1 = std::sin(thd)*cosTheta/sinTheta + std::cos(thd);
116 const G4double c2 = -p*std::sin(thd)/(r*sinTheta);
117 const ThreeVector newMomentum = momentum*c1 + position*c2;
118 (*particle)->setMomentum(newMomentum);
119 }
120 }
121 }
122 }
123
124 G4double CoulombNonRelativistic::maxImpactParameter(ParticleSpecies const &p, const G4double kinE,
125 Nucleus const * const n) const {
126 const G4double theMinimumDistance = minimumDistance(p, kinE, n);
127 G4double rMax = n->getUniverseRadius();
128 if(p.theType == Composite)
129 rMax += 2.*ParticleTable::getLargestNuclearRadius(p.theA, p.theZ);
130 const G4double theMaxImpactParameterSquared = rMax*(rMax-theMinimumDistance);
131 if(theMaxImpactParameterSquared<=0.)
132 return 0.;
133 const G4double theMaxImpactParameter = std::sqrt(theMaxImpactParameterSquared);
134 return theMaxImpactParameter;
135 }
136
137 G4bool CoulombNonRelativistic::coulombDeviation(Particle * const p, Nucleus const * const n) const {
138 // Determine the rotation angle and the new impact parameter
139 ThreeVector positionTransverse = p->getTransversePosition();
140 const G4double impactParameterSquared = positionTransverse.mag2();
141 const G4double impactParameter = std::sqrt(impactParameterSquared);
142
143 // Some useful variables
144 const G4double theMinimumDistance = minimumDistance(p, n);
145 // deltaTheta2 = (pi - Rutherford scattering angle)/2
146 G4double deltaTheta2 = std::atan(2.*impactParameter/theMinimumDistance);
147 if(deltaTheta2<0.)
148 deltaTheta2 += Math::pi;
149 const G4double eccentricity = 1./std::cos(deltaTheta2);
150
151 G4double newImpactParameter, alpha; // Parameters that must be determined by the deviation
152
153 const G4double radius = getCoulombRadius(p->getSpecies(), n);
154 const G4double impactParameterTangentSquared = radius*(radius-theMinimumDistance);
155 if(impactParameterSquared >= impactParameterTangentSquared) {
156 // The particle trajectory misses the Coulomb sphere
157 // In this case the new impact parameter is the minimum distance of
158 // approach of the hyperbola
159 // assert(std::abs(1. + 2.*impactParameter*impactParameter/(radius*theMinimumDistance))>=eccentricity);
160 newImpactParameter = 0.5 * theMinimumDistance * (1.+eccentricity); // the minimum distance of approach
161 alpha = Math::piOverTwo - deltaTheta2; // half the Rutherford scattering angle
162 } else {
163 // The particle trajectory intersects the Coulomb sphere
164
165 // Compute the entrance angle
166 const G4double argument = -(1. + 2.*impactParameter*impactParameter/(radius*theMinimumDistance))
167 / eccentricity;
168 const G4double thetaIn = Math::twoPi - Math::arcCos(argument) - deltaTheta2;
169
170 // Velocity angle at the entrance point
171 alpha = std::atan((1+std::cos(thetaIn))
172 / (std::sqrt(eccentricity*eccentricity-1.) - std::sin(thetaIn)))
173 * Math::sign(theMinimumDistance);
174 // New impact parameter
175 newImpactParameter = radius * std::sin(thetaIn - alpha);
176 }
177
178 // Modify the impact parameter of the particle
179 positionTransverse *= newImpactParameter/positionTransverse.mag();
180 const ThreeVector theNewPosition = p->getLongitudinalPosition() + positionTransverse;
181 p->setPosition(theNewPosition);
182
183 // Determine the rotation axis for the incoming particle
184 const ThreeVector &momentum = p->getMomentum();
185 ThreeVector rotationAxis = momentum.vector(positionTransverse);
186 const G4double axisLength = rotationAxis.mag();
187 // Apply the rotation
188 if(axisLength>1E-20) {
189 rotationAxis /= axisLength;
190 p->rotatePositionAndMomentum(alpha, rotationAxis);
191 }
192
193 return true;
194 }
195
196 G4double CoulombNonRelativistic::getCoulombRadius(ParticleSpecies const &p, Nucleus const * const n) const {
197 if(p.theType == Composite) {
198 const G4int Zp = p.theZ;
199 const G4int Ap = p.theA;
200 const G4int Zt = n->getZ();
201 const G4int At = n->getA();
202 G4double barr, radius = 0.;
203 if(Zp==1 && Ap==2) { // d
204 barr = 0.2565*Math::pow23((G4double)At)-0.78;
205 radius = PhysicalConstants::eSquared*Zp*Zt/barr - 2.5;
206 } else if(Zp==1 && Ap==3) { // t
207 barr = 0.5*(0.5009*Math::pow23((G4double)At)-1.16);
208 radius = PhysicalConstants::eSquared*Zt/barr - 0.5;
209 } else if(Zp==2) { // alpha, He3
210 barr = 0.5939*Math::pow23((G4double)At)-1.64;
211 radius = PhysicalConstants::eSquared*Zp*Zt/barr - 0.5;
212 } else if(Zp>2) {
213 // Coulomb radius from the Shen model
214 const G4double Ap13 = Math::pow13((G4double)Ap);
215 const G4double At13 = Math::pow13((G4double)At);
216 const G4double rp = 1.12*Ap13 - 0.94/Ap13;
217 const G4double rt = 1.12*At13 - 0.94/At13;
218 const G4double someRadius = rp+rt+3.2;
219 const G4double theShenBarrier = PhysicalConstants::eSquared*Zp*Zt/someRadius - rt*rp/(rt+rp);
220 radius = PhysicalConstants::eSquared*Zp*Zt/theShenBarrier;
221 }
222 if(radius<=0.) {
223 radius = ParticleTable::getLargestNuclearRadius(Ap,Zp) + ParticleTable::getLargestNuclearRadius(At, Zt);
224 INCL_ERROR("Negative Coulomb radius! Using the sum of nuclear radii = " << radius << '\n');
225 }
226 INCL_DEBUG("Coulomb radius for particle "
227 << ParticleTable::getShortName(p) << " in nucleus A=" << At <<
228 ", Z=" << Zt << ": " << radius << '\n');
229 return radius;
230 } else
231 return n->getUniverseRadius();
232 }
233
234 }
235