source: trunk/source/processes/electromagnetic/standard/src/G4eCoulombScatteringModel.cc@ 955

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25//
26// $Id: G4eCoulombScatteringModel.cc,v 1.40 2008/01/07 08:32:01 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-01-patch-02 $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class file
32//
33//
34// File name: G4eCoulombScatteringModel
35//
36// Author: Vladimir Ivanchenko
37//
38// Creation date: 22.08.2005
39//
40// Modifications:
41// 01.08.06 V.Ivanchenko extend upper limit of table to TeV and review the
42// logic of building - only elements from G4ElementTable
43// 08.08.06 V.Ivanchenko build internal table in ekin scale, introduce faclim
44// 19.08.06 V.Ivanchenko add inline function ScreeningParameter
45// 09.10.07 V.Ivanchenko reorganized methods, add cut dependence in scattering off e-
46//
47// Class Description:
48//
49// -------------------------------------------------------------------
50//
51//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
52//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
53
54#include "G4eCoulombScatteringModel.hh"
55#include "Randomize.hh"
56#include "G4DataVector.hh"
57#include "G4ElementTable.hh"
58#include "G4PhysicsLogVector.hh"
59#include "G4ParticleChangeForGamma.hh"
60#include "G4Electron.hh"
61#include "G4Positron.hh"
62#include "G4Proton.hh"
63
64//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
65
66using namespace std;
67
68G4eCoulombScatteringModel::G4eCoulombScatteringModel(
69 G4double thetaMin, G4double thetaMax, G4bool build,
70 G4double tlim, const G4String& nam)
71 : G4VEmModel(nam),
72 cosThetaMin(cos(thetaMin)),
73 cosThetaMax(cos(thetaMax)),
74 q2Limit(tlim),
75 theCrossSectionTable(0),
76 lowKEnergy(keV),
77 highKEnergy(TeV),
78 alpha2(fine_structure_const*fine_structure_const),
79 faclim(100.0),
80 nbins(12),
81 nmax(100),
82 buildTable(build),
83 isInitialised(false)
84{
85 fNistManager = G4NistManager::Instance();
86 theElectron = G4Electron::Electron();
87 thePositron = G4Positron::Positron();
88 theProton = G4Proton::Proton();
89 a0 = alpha2*electron_mass_c2*electron_mass_c2/(0.885*0.885);
90 G4double p0 = electron_mass_c2*classic_electr_radius;
91 coeff = twopi*p0*p0;
92 constn = 6.937e-6/(MeV*MeV);
93 tkin = targetZ = targetA = mom2 = DBL_MIN;
94 elecXSection = nucXSection = 0.0;
95 ecut = DBL_MAX;
96 particle = 0;
97 for(size_t j=0; j<100; j++) {index[j] = -1;}
98}
99
100//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
101
102G4eCoulombScatteringModel::~G4eCoulombScatteringModel()
103{
104 if(theCrossSectionTable) {
105 theCrossSectionTable->clearAndDestroy();
106 delete theCrossSectionTable;
107 }
108}
109
110//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
111
112void G4eCoulombScatteringModel::Initialise(const G4ParticleDefinition* p,
113 const G4DataVector&)
114{
115 // G4cout << "!!! G4eCoulombScatteringModel::Initialise for "
116 // << p->GetParticleName() << " cos(TetMin)= " << cosThetaMin
117 // << " cos(TetMax)= " << cosThetaMax <<G4endl;
118 if(!isInitialised) {
119 isInitialised = true;
120
121 if(pParticleChange)
122 fParticleChange =
123 reinterpret_cast<G4ParticleChangeForGamma*>(pParticleChange);
124 else
125 fParticleChange = new G4ParticleChangeForGamma();
126 } else {
127 return;
128 }
129
130 if(p->GetParticleType() == "nucleus") buildTable = false;
131 if(!buildTable) return;
132
133 // Compute log cross section table per atom
134 if(!theCrossSectionTable) theCrossSectionTable = new G4PhysicsTable();
135
136 nbins = 2*G4int(log10(highKEnergy/lowKEnergy));
137}
138
139//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
140
141G4double G4eCoulombScatteringModel::ComputeCrossSectionPerAtom(
142 const G4ParticleDefinition* p,
143 G4double kinEnergy,
144 G4double Z, G4double A,
145 G4double cutEnergy, G4double)
146{
147 if(p == particle && kinEnergy == tkin && Z == targetZ &&
148 A == targetA && cutEnergy == ecut) return nucXSection;
149
150 //G4cout << "### G4eCoulombScatteringModel::ComputeCrossSectionPerAtom for "
151 // << p->GetParticleName() << " Z= " << Z << " A= " << A
152 // << " e= " << kinEnergy << G4endl;
153
154 nucXSection = ComputeElectronXSectionPerAtom(p,kinEnergy,Z,A,cutEnergy);
155
156 // nuclear cross section
157 if(theCrossSectionTable) {
158 G4bool b;
159 G4int iz = G4int(Z);
160 G4int idx = index[iz];
161
162 // compute table for given Z
163 if(-1 == idx) {
164 idx = theCrossSectionTable->size();
165 index[iz] = idx;
166 G4PhysicsLogVector* ptrVector
167 = new G4PhysicsLogVector(lowKEnergy, highKEnergy, nbins);
168 // G4cout << "New vector Z= " << iz << " A= " << A << " idx= " << idx << G4endl;
169 G4double e, value;
170 for(G4int i=0; i<=nbins; i++) {
171 e = ptrVector->GetLowEdgeEnergy( i ) ;
172 value = CalculateCrossSectionPerAtom(p, e, Z, A);
173 ptrVector->PutValue( i, log(value) );
174 }
175 theCrossSectionTable->push_back(ptrVector);
176 }
177
178 // take value from the table
179 nucXSection +=
180 std::exp((((*theCrossSectionTable)[idx]))->GetValue(kinEnergy, b));
181
182 // compute value from scratch
183 } else nucXSection += CalculateCrossSectionPerAtom(p, kinEnergy, Z, A);
184
185 // G4cout << " cross(bn)= " << nucXSection/barn << G4endl;
186
187 if(nucXSection < 0.0) nucXSection = 0.0;
188 return nucXSection;
189}
190
191//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
192
193G4double G4eCoulombScatteringModel::ComputeElectronXSectionPerAtom(
194 const G4ParticleDefinition* p,
195 G4double kinEnergy,
196 G4double Z,
197 G4double A,
198 G4double cutEnergy)
199{
200 if(p == particle && kinEnergy == tkin && Z == targetZ &&
201 cutEnergy == ecut) return elecXSection;
202 ecut = cutEnergy;
203 elecXSection = 0.0;
204 SetupParticle(p);
205 G4double ekin = std::max(keV, kinEnergy);
206 //G4double ekin = kinEnergy;
207 SetupTarget(Z, A, ekin);
208
209 G4double tmax = tkin;
210 if(p == theElectron) tmax *= 0.5;
211 else if(p != thePositron) {
212 G4double ratio = electron_mass_c2/mass;
213 G4double tau = tkin/mass;
214 tmax = 2.0*electron_mass_c2*tau*(tau + 2.)/
215 (1.0 + 2.0*ratio*(tau + 1.0) + ratio*ratio);
216 }
217
218 cosTetMaxElec = cosTetMaxNuc;
219 G4double t = std::min(cutEnergy, tmax);
220 G4double mom21 = t*(t + 2.0*electron_mass_c2);
221 G4double t1 = tkin - t;
222 if(t1 > 0.0) {
223 G4double mom22 = t1*(t1 + 2.0*mass);
224 G4double ctm = (mom2 + mom22 - mom21)*0.5/sqrt(mom2*mom22);
225 if(ctm > cosTetMaxElec && ctm <= 1.0) cosTetMaxElec = ctm;
226 }
227
228 if(cosTetMaxElec < cosThetaMin) {
229 G4double x1 = 1.0 - cosThetaMin + screenZ;
230 G4double x2 = 1.0 - cosTetMaxElec + screenZ;
231 elecXSection = coeff*Z*chargeSquare*invbeta2*
232 (cosThetaMin - cosTetMaxElec)/(x1*x2*mom2);
233 }
234 // G4cout << "cut= " << ecut << " e= " << tkin
235 // << " croosE(barn)= " << elecXSection/barn
236 // << " cosEl= " << cosTetMaxElec << " costmin= " << cosThetaMin << G4endl;
237 return elecXSection;
238}
239
240//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
241
242G4double G4eCoulombScatteringModel::CalculateCrossSectionPerAtom(
243 const G4ParticleDefinition* p,
244 G4double kinEnergy,
245 G4double Z, G4double A)
246{
247 G4double cross = 0.0;
248 SetupParticle(p);
249 G4double ekin = std::max(keV, kinEnergy);
250 //G4double ekin = kinEnergy;
251 SetupTarget(Z, A, ekin);
252
253 if(cosTetMaxNuc < cosThetaMin) {
254 G4double x1 = 1.0 - cosThetaMin;
255 G4double x2 = 1.0 - cosTetMaxNuc;
256 G4double x3 = cosThetaMin - cosTetMaxNuc;
257 G4double z1 = x1 + screenZ;
258 G4double z2 = x2 + screenZ;
259 G4double d = 1.0/formfactA - screenZ;
260 G4double d1 = 1.0 - formfactA*screenZ;
261 G4double zn1= x1 + d;
262 G4double zn2= x2 + d;
263 cross = coeff*Z*Z*chargeSquare*invbeta2
264 *(x3/(z1*z2) + x3/(zn1*zn2) +
265 2.0*std::log(z1*zn2/(z2*zn1))/d) / (mom2*d1*d1);
266 }
267
268 // G4cout << "CalculateCrossSectionPerAtom: e(MeV)= " << tkin
269 // << " cross(b)= " << cross/barn << " ctmin= " << cosThetaMin
270 // << " ctmax= " << cosTetMaxNuc << G4endl;
271
272 return cross;
273}
274
275//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
276
277void G4eCoulombScatteringModel::SampleSecondaries(
278 std::vector<G4DynamicParticle*>*,
279 const G4MaterialCutsCouple* couple,
280 const G4DynamicParticle* dp,
281 G4double cutEnergy,
282 G4double maxEnergy)
283{
284 const G4Material* aMaterial = couple->GetMaterial();
285 const G4ParticleDefinition* p = dp->GetDefinition();
286 G4double kinEnergy = dp->GetKineticEnergy();
287
288 // Select atom and setup
289 SetupParticle(p);
290 const G4Element* elm =
291 SelectRandomAtom(aMaterial,p,kinEnergy,cutEnergy,maxEnergy);
292 G4double Z = elm->GetZ();
293 G4double A = elm->GetN();
294
295 G4double cross =
296 ComputeCrossSectionPerAtom(p,kinEnergy,Z,A,cutEnergy,maxEnergy);
297
298 G4double costm = cosTetMaxNuc;
299 G4double formf = formfactA;
300 if(G4UniformRand()*cross < elecXSection) {
301 costm = cosTetMaxElec;
302 formf = 0.0;
303 }
304 /*
305 G4cout << "G4eCoul...SampleSecondaries: e(MeV)= " << tkin
306 << " ctmin= " << cosThetaMin
307 << " ctmaxN= " << cosTetMaxNuc
308 << " ctmax= " << costm
309 << " Z= " << Z << " A= " << A
310 << " cross= " << cross/barn << " crossE= " << elecXSection/barn
311 << G4endl;
312 */
313 if(costm >= cosThetaMin) return;
314
315 G4double x1 = 1. - cosThetaMin + screenZ;
316 G4double x2 = 1. - costm;
317 G4double x3 = cosThetaMin - costm;
318 G4double grej, z, z1;
319 do {
320 z = G4UniformRand()*x3;
321 z1 = (x1*x2 - screenZ*z)/(x1 + z);
322 if(z1 < 0.0) z1 = 0.0;
323 else if(z1 > 2.0) z1 = 2.0;
324 grej = 1.0/(1.0 + formf*z1);
325 } while ( G4UniformRand() > grej*grej );
326
327 G4double cost = 1.0 - z1;
328 G4double sint= sqrt(z1*(2.0 - z1));
329 /*
330 if(sint > 0.1)
331 G4cout<<"## SampleSecondaries: e(MeV)= " << kinEnergy
332 << " sint= " << sint << " Z= " << Z << " screenZ= " << screenZ
333 << " cn= " << formf
334 << G4endl;
335 */
336 G4double phi = twopi * G4UniformRand();
337
338 G4ThreeVector direction = dp->GetMomentumDirection();
339 G4ThreeVector newDirection(cos(phi)*sint,sin(phi)*sint,cost);
340 newDirection.rotateUz(direction);
341
342 fParticleChange->ProposeMomentumDirection(newDirection);
343
344 return;
345}
346
347//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
348
349
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