1 | // |
---|
2 | // ******************************************************************** |
---|
3 | // * License and Disclaimer * |
---|
4 | // * * |
---|
5 | // * The Geant4 software is copyright of the Copyright Holders of * |
---|
6 | // * the Geant4 Collaboration. It is provided under the terms and * |
---|
7 | // * conditions of the Geant4 Software License, included in the file * |
---|
8 | // * LICENSE and available at http://cern.ch/geant4/license . These * |
---|
9 | // * include a list of copyright holders. * |
---|
10 | // * * |
---|
11 | // * Neither the authors of this software system, nor their employing * |
---|
12 | // * institutes,nor the agencies providing financial support for this * |
---|
13 | // * work make any representation or warranty, express or implied, * |
---|
14 | // * regarding this software system or assume any liability for its * |
---|
15 | // * use. Please see the license in the file LICENSE and URL above * |
---|
16 | // * for the full disclaimer and the limitation of liability. * |
---|
17 | // * * |
---|
18 | // * This code implementation is the result of the scientific and * |
---|
19 | // * technical work of the GEANT4 collaboration. * |
---|
20 | // * By using, copying, modifying or distributing the software (or * |
---|
21 | // * any work based on the software) you agree to acknowledge its * |
---|
22 | // * use in resulting scientific publications, and indicate your * |
---|
23 | // * acceptance of all terms of the Geant4 Software license. * |
---|
24 | // ******************************************************************** |
---|
25 | // |
---|
26 | // |
---|
27 | // $Id: G4FermiConfiguration.cc,v 1.9 2006/06/29 20:12:52 gunter Exp $ |
---|
28 | // GEANT4 tag $Name: geant4-09-02-ref-02 $ |
---|
29 | // |
---|
30 | // Hadronic Process: Nuclear De-excitations |
---|
31 | // by V. Lara (Nov 1998) |
---|
32 | // |
---|
33 | // |
---|
34 | |
---|
35 | |
---|
36 | #include "G4FermiConfiguration.hh" |
---|
37 | #include "G4FermiPhaseSpaceDecay.hh" |
---|
38 | #include <set> |
---|
39 | |
---|
40 | // Kappa = V/V_0 it is used in calculation of Coulomb energy |
---|
41 | // Kappa is adimensional |
---|
42 | const G4double G4FermiConfiguration::Kappa = 1.0; |
---|
43 | |
---|
44 | // r0 is the nuclear radius |
---|
45 | const G4double G4FermiConfiguration::r0 = 1.3*fermi; |
---|
46 | |
---|
47 | |
---|
48 | G4double G4FermiConfiguration::CoulombBarrier(void) |
---|
49 | { |
---|
50 | // Calculates Coulomb Barrier (MeV) for given channel with K fragments. |
---|
51 | const G4double Coef = (3./5.)*(elm_coupling/r0)*std::pow(1./(1.+Kappa), 1./3.); |
---|
52 | |
---|
53 | G4double SumA = 0; |
---|
54 | G4double SumZ = 0; |
---|
55 | G4double CoulombEnergy = 0.; |
---|
56 | for (std::vector<const G4VFermiFragment*>::iterator i = Configuration.begin(); |
---|
57 | i != Configuration.end(); i++) |
---|
58 | { |
---|
59 | G4double z = static_cast<G4double>((*i)->GetZ()); |
---|
60 | G4double a = static_cast<G4double>((*i)->GetA()); |
---|
61 | CoulombEnergy += (z*z) / std::pow(a, 1./3.); |
---|
62 | SumA += a; |
---|
63 | SumZ += z; |
---|
64 | } |
---|
65 | CoulombEnergy -= SumZ*SumZ/std::pow(SumA, 1./3.); |
---|
66 | return -Coef * CoulombEnergy; |
---|
67 | } |
---|
68 | |
---|
69 | |
---|
70 | |
---|
71 | |
---|
72 | G4double G4FermiConfiguration::DecayProbability(const G4int A, const G4double TotalE) |
---|
73 | // Decay probability for a given channel with K fragments |
---|
74 | { |
---|
75 | // A: Atomic Weight |
---|
76 | // TotalE: Total energy of nucleus |
---|
77 | |
---|
78 | |
---|
79 | G4double KineticEnergy = TotalE; // MeV |
---|
80 | G4double ProdMass = 1.0; |
---|
81 | G4double SumMass = 0.0; |
---|
82 | G4double S_n = 1.0; |
---|
83 | std::set<G4int> combSet; |
---|
84 | std::multiset<G4int> combmSet; |
---|
85 | |
---|
86 | for (std::vector<const G4VFermiFragment*>::iterator i = Configuration.begin(); |
---|
87 | i != Configuration.end(); i++) |
---|
88 | { |
---|
89 | G4int a = (*i)->GetA(); |
---|
90 | combSet.insert(a); |
---|
91 | combmSet.insert(a); |
---|
92 | G4double m = (*i)->GetFragmentMass(); |
---|
93 | ProdMass *= m; |
---|
94 | SumMass += m; |
---|
95 | // Spin factor S_n |
---|
96 | S_n *= (*i)->GetPolarization(); |
---|
97 | KineticEnergy -= m + (*i)->GetExcitationEnergy(); |
---|
98 | } |
---|
99 | |
---|
100 | // Check that there is enough energy to produce K fragments |
---|
101 | if (KineticEnergy <= 0.0) return 0.0; |
---|
102 | if ((KineticEnergy -= this->CoulombBarrier()) <= 0.0) return 0.0; |
---|
103 | |
---|
104 | |
---|
105 | G4double MassFactor = ProdMass/SumMass; |
---|
106 | MassFactor *= std::sqrt(MassFactor); |
---|
107 | |
---|
108 | // Number of fragments |
---|
109 | G4int K = Configuration.size(); |
---|
110 | |
---|
111 | // This is the constant (doesn't depend on nucleus) part |
---|
112 | const G4double ConstCoeff = std::pow(r0/hbarc,3.0)*Kappa*std::sqrt(2.0/pi)/3.0; |
---|
113 | G4double Coeff = std::pow(ConstCoeff*A,K-1); |
---|
114 | |
---|
115 | |
---|
116 | // Calculation of 1/Gamma(3(k-1)/2) |
---|
117 | G4double Gamma = 1.0; |
---|
118 | G4double arg = 3.0*(K-1)/2.0 - 1.0; |
---|
119 | while (arg > 1.1) |
---|
120 | { |
---|
121 | Gamma *= arg; |
---|
122 | arg--; |
---|
123 | } |
---|
124 | if ((K-1)%2 == 1) Gamma *= std::sqrt(pi); |
---|
125 | |
---|
126 | |
---|
127 | |
---|
128 | // Permutation Factor G_n |
---|
129 | G4double G_n = 1.0; |
---|
130 | for (std::set<G4int>::iterator s = combSet.begin(); s != combSet.end(); ++s) |
---|
131 | { |
---|
132 | for (G4int ni = combmSet.count(*s); ni > 1; ni--) G_n *= ni; |
---|
133 | } |
---|
134 | |
---|
135 | G4double Weight = Coeff * MassFactor * (S_n / G_n) / Gamma; |
---|
136 | Weight *= std::pow(KineticEnergy,3.0*(K-1)/2.0)/KineticEnergy; |
---|
137 | |
---|
138 | return Weight; |
---|
139 | } |
---|
140 | |
---|
141 | |
---|
142 | G4FragmentVector * G4FermiConfiguration::GetFragments(const G4Fragment & theNucleus) |
---|
143 | { |
---|
144 | |
---|
145 | G4FermiPhaseSpaceDecay thePhaseSpace; |
---|
146 | |
---|
147 | // Calculate Momenta of K fragments |
---|
148 | G4double M = theNucleus.GetMomentum().m(); |
---|
149 | std::vector<G4double> m; |
---|
150 | m.reserve(Configuration.size()); |
---|
151 | std::vector<const G4VFermiFragment*>::iterator i; |
---|
152 | for (i = Configuration.begin(); i != Configuration.end(); ++i) |
---|
153 | { |
---|
154 | m.push_back( (*i)->GetTotalEnergy() ); |
---|
155 | } |
---|
156 | std::vector<G4LorentzVector*>* MomentumComponents = |
---|
157 | thePhaseSpace.Decay(M,m); |
---|
158 | |
---|
159 | G4FragmentVector * theResult = new G4FragmentVector; |
---|
160 | |
---|
161 | G4ThreeVector boostVector = theNucleus.GetMomentum().boostVector(); |
---|
162 | |
---|
163 | |
---|
164 | // Go back to the Lab Frame |
---|
165 | for (i = Configuration.begin(); i != Configuration.end(); ++i) |
---|
166 | { |
---|
167 | #ifdef G4NO_ISO_VECDIST |
---|
168 | std::vector<const G4VFermiFragment*>::difference_type n = 0; |
---|
169 | std::distance(Configuration.begin(), i, n); |
---|
170 | G4LorentzVector FourMomentum(*(MomentumComponents->operator[](n))); |
---|
171 | #else |
---|
172 | G4LorentzVector FourMomentum(*(MomentumComponents-> |
---|
173 | operator[](std::distance(Configuration.begin(),i)))); |
---|
174 | #endif |
---|
175 | |
---|
176 | // Lorentz boost |
---|
177 | FourMomentum.boost(boostVector); |
---|
178 | |
---|
179 | G4FragmentVector * fragment = (*i)->GetFragment(FourMomentum); |
---|
180 | |
---|
181 | |
---|
182 | for (G4FragmentVector::reverse_iterator ri = fragment->rbegin(); |
---|
183 | ri != fragment->rend(); ++ri) |
---|
184 | { |
---|
185 | theResult->push_back(*ri); |
---|
186 | } |
---|
187 | delete fragment; |
---|
188 | } |
---|
189 | |
---|
190 | if (!MomentumComponents->empty()) |
---|
191 | { |
---|
192 | std::for_each(MomentumComponents->begin(),MomentumComponents->end(), |
---|
193 | DeleteFragment()); |
---|
194 | } |
---|
195 | |
---|
196 | delete MomentumComponents; |
---|
197 | |
---|
198 | return theResult; |
---|
199 | } |
---|
200 | |
---|
201 | |
---|
202 | G4ParticleMomentum G4FermiConfiguration::IsotropicVector(const G4double Magnitude) |
---|
203 | // Samples a isotropic random vectorwith a magnitud given by Magnitude. |
---|
204 | // By default Magnitude = 1.0 |
---|
205 | { |
---|
206 | G4double CosTheta = 1.0 - 2.0*G4UniformRand(); |
---|
207 | G4double SinTheta = std::sqrt(1.0 - CosTheta*CosTheta); |
---|
208 | G4double Phi = twopi*G4UniformRand(); |
---|
209 | G4ParticleMomentum Vector(Magnitude*std::cos(Phi)*SinTheta, |
---|
210 | Magnitude*std::sin(Phi)*SinTheta, |
---|
211 | Magnitude*CosTheta); |
---|
212 | return Vector; |
---|
213 | } |
---|