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35 //
36 // %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
37 //
38 // MODULE: G4EMDissociationCrossSection.cc
39 //
40 // Version: B.1
41 // Date: 15/04/04
42 // Author: P R Truscott
43 // Organisation: QinetiQ Ltd, UK
44 // Customer: ESA/ESTEC, NOORDWIJK
45 // Contract: 17191/03/NL/LvH
46 //
47 // %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
48 //
49 // CHANGE HISTORY
50 // --------------
51 //
52 // 17 October 2003, P R Truscott, QinetiQ Ltd, UK
53 // Created.
54 //
55 // 15 March 2004, P R Truscott, QinetiQ Ltd, UK
56 // Beta release
57 //
58 // 30 May 2005, J.P. Wellisch removed a compilation warning on gcc 3.4 for
59 // geant4 7.1.
60 // 09 November 2010, V.Ivanchenko make class applicable for Hydrogen but
61 // set cross section for Hydrogen to zero
62 //
63 // 17 August 2011, V.Ivanchenko, provide migration to new design of cross
64 // sections considering this cross section as element-wise
65 //
66 // %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
67 //////////////////////////////////////////////////////////////////////////////
68 //
69 #include "G4EMDissociationCrossSection.hh"
70 #include "G4PhysicalConstants.hh"
71 #include "G4SystemOfUnits.hh"
72 #include "G4ParticleTable.hh"
73 #include "G4IonTable.hh"
74 #include "G4HadTmpUtil.hh"
75 #include "globals.hh"
76 #include "G4NistManager.hh"
77
78
79 G4EMDissociationCrossSection::G4EMDissociationCrossSection ()
80 : G4VCrossSectionDataSet("Electromagnetic dissociation")
81 {
82 // This function makes use of the class which can sample the virtual photon
83 // spectrum, G4EMDissociationSpectrum.
84
85 thePhotonSpectrum = new G4EMDissociationSpectrum();
86
87 // Define other constants.
88
89 r0 = 1.18 * fermi;
90 J = 36.8 * MeV;
91 Qprime = 17.0 * MeV;
92 epsilon = 0.0768;
93 xd = 0.25;
94 }
95
96 //////////////////////////////////////////////////////////////////////////////
97
98 G4EMDissociationCrossSection::~G4EMDissociationCrossSection()
99 {
100 delete thePhotonSpectrum;
101 }
102 /////////////////////////////////////////////////////////////////////////////
103 //
104 G4bool
105 G4EMDissociationCrossSection::IsElementApplicable(const G4DynamicParticle* part,
106 G4int /*ZZ*/, const G4Material*)
107 {
108 //
109 // The condition for the applicability of this class is that the projectile
110 // must be an ion and the target must have more than one nucleon. In reality
111 // the value of A for either the projectile or target could be much higher,
112 // since for cases where both he projectile and target are medium to small
113 // Z, the probability of the EMD process is, I think, VERY small.
114 //
115 if (G4ParticleTable::GetParticleTable()->GetIonTable()->IsIon(part->GetDefinition())) {
116 return true;
117 } else {
118 return false;
119 }
120 }
121
122 //////////////////////////////////////////////////////////////////////////////
123 //
124 G4double G4EMDissociationCrossSection::GetElementCrossSection
125 (const G4DynamicParticle* theDynamicParticle, G4int Z,
126 const G4Material*)
127 {
128 // VI protection for Hydrogen
129 if(1 >= Z) { return 0.0; }
130
131 // Zero cross-section for particles with kinetic energy less than 2 MeV to prevent
132 // possible abort signal from bad arithmetic in GetCrossSectionForProjectile
133 if ( theDynamicParticle->GetKineticEnergy() < 2.0*CLHEP::MeV ) { return 0.0; }
134
135 //
136 // Get relevant information about the projectile and target (A, Z) and
137 // velocity of the projectile.
138 //
139 const G4ParticleDefinition *definitionP = theDynamicParticle->GetDefinition();
140 G4double AP = definitionP->GetBaryonNumber();
141 G4double ZP = definitionP->GetPDGCharge();
142 G4double b = theDynamicParticle->GetBeta();
143 if (b <= 0.0 && b >= 1.0) { return 0.0; }
144
145 G4double AT = G4NistManager::Instance()->GetAtomicMassAmu(Z);
146 G4double ZT = (G4double)Z;
147 G4double bmin = thePhotonSpectrum->GetClosestApproach(AP, ZP, AT, ZT, b);
148 //
149 //
150 // Calculate the cross-section for the projectile and then the target. The
151 // information is returned in a G4PhysicsFreeVector, which separates out the
152 // cross-sections for the E1 and E2 moments of the virtual photon field, and
153 // the energies (GDR and GQR).
154 //
155 G4PhysicsFreeVector *theProjectileCrossSections =
156 GetCrossSectionForProjectile (AP, ZP, AT, ZT, b, bmin);
157 G4double crossSection =
158 (*theProjectileCrossSections)[0]+(*theProjectileCrossSections)[1];
159 delete theProjectileCrossSections;
160 G4PhysicsFreeVector *theTargetCrossSections =
161 GetCrossSectionForTarget (AP, ZP, AT, ZT, b, bmin);
162 crossSection +=
163 (*theTargetCrossSections)[0]+(*theTargetCrossSections)[1];
164 delete theTargetCrossSections;
165 return crossSection;
166 }
167 ////////////////////////////////////////////////////////////////////////////////
168 //
169 G4PhysicsFreeVector *
170 G4EMDissociationCrossSection::GetCrossSectionForProjectile (G4double AP,
171 G4double ZP, G4double /* AT */, G4double ZT, G4double b, G4double bmin)
172 {
173 //
174 //
175 // Use Wilson et al's approach to calculate the cross-sections due to the E1
176 // and E2 moments of the field at the giant dipole and quadrupole resonances
177 // respectively, Note that the algorithm is traditionally applied to the
178 // EMD break-up of the projectile in the field of the target, as is implemented
179 // here.
180 //
181 // Initialise variables and calculate the energies for the GDR and GQR.
182 //
183 G4double AProot3 = G4Pow::GetInstance()->A13(AP);
184 G4double u = 3.0 * J / Qprime / AProot3;
185 G4double R0 = r0 * AProot3;
186 G4double E_GDR = hbarc / std::sqrt(0.7*amu_c2*R0*R0/8.0/J*
187 (1.0 + u - (1.0 + epsilon + 3.0*u)/(1.0 + epsilon + u)*epsilon));
188 G4double E_GQR = 63.0 * MeV / AProot3;
189 //
190 //
191 // Determine the virtual photon spectra at these energies.
192 //
193 G4double ZTsq = ZT * ZT;
194 G4double nE1 = ZTsq *
195 thePhotonSpectrum->GetGeneralE1Spectrum(E_GDR, b, bmin);
196 G4double nE2 = ZTsq *
197 thePhotonSpectrum->GetGeneralE2Spectrum(E_GQR, b, bmin);
198 //
199 //
200 // Now calculate the cross-section of the projectile for interaction with the
201 // E1 and E2 fields.
202 //
203 G4double sE1 = 60.0 * millibarn * MeV * (AP-ZP)*ZP/AP;
204 G4double sE2 = 0.22 * microbarn / MeV * ZP * AProot3 * AProot3;
205 if (AP > 100.0) sE2 *= 0.9;
206 else if (AP > 40.0) sE2 *= 0.6;
207 else sE2 *= 0.3;
208 //
209 //
210 // ... and multiply with the intensity of the virtual photon spectra to get
211 // the probability of interaction.
212 //
213 G4PhysicsFreeVector *theCrossSectionVector = new G4PhysicsFreeVector(2);
214 theCrossSectionVector->PutValue(0, E_GDR, sE1*nE1);
215 theCrossSectionVector->PutValue(1, E_GQR, sE2*nE2*E_GQR*E_GQR);
216
217 return theCrossSectionVector;
218 }
219
220 ////////////////////////////////////////////////////////////////////////////////
221 //
222 G4PhysicsFreeVector *
223 G4EMDissociationCrossSection::GetCrossSectionForTarget (G4double AP,
224 G4double ZP, G4double AT, G4double ZT, G4double b, G4double bmin)
225 {
226 //
227 // This is a cheaky little member function to calculate the probability of
228 // EMD for the target in the field of the projectile ... just by reversing the
229 // A and Z's for the participants.
230 //
231 return GetCrossSectionForProjectile (AT, ZT, AP, ZP, b, bmin);
232 }
233
234 ////////////////////////////////////////////////////////////////////////////////
235 //
236 G4double
237 G4EMDissociationCrossSection::GetWilsonProbabilityForProtonDissociation(G4double A,
238 G4double Z)
239 {
240 //
241 // This is a simple algorithm to choose whether a proton or neutron is ejected
242 // from the nucleus in the EMD interaction.
243 //
244 G4double p = 0.0;
245 if (Z < 2.0)
246 p = 0.0; // To avoid to remove one proton from hydrogen isotopes
247 else if (Z < 6.0)
248 p = 0.5;
249 else if (Z < 8.0)
250 p = 0.6;
251 else if (Z < 14.0)
252 p = 0.7;
253 else
254 {
255 G4double p1 = (G4double) Z / (G4double) A;
256 G4double p2 = 1.95*G4Exp(-0.075*Z);
257 if (p1 < p2) p = p1;
258 else p = p2;
259 }
260
261 return p;
262 }
263