source: trunk/source/processes/electromagnetic/standard/src/G4MollerBhabhaModel.cc@ 1330

Last change on this file since 1330 was 1315, checked in by garnier, 15 years ago

update geant4-09-04-beta-cand-01 interfaces-V09-03-09 vis-V09-03-08
File size: 13.6 KB
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[819]1//
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25//
[1315]26// $Id: G4MollerBhabhaModel.cc,v 1.38 2010/04/06 17:10:16 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-04-beta-cand-01 $
[819]28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class file
32//
33//
34// File name: G4MollerBhabhaModel
35//
36// Author: Vladimir Ivanchenko on base of Laszlo Urban code
37//
38// Creation date: 03.01.2002
39//
40// Modifications:
41//
42// 13-11-02 Minor fix - use normalised direction (V.Ivanchenko)
43// 04-12-02 Change G4DynamicParticle constructor in PostStepDoIt (V.Ivanchenko)
44// 23-12-02 Change interface in order to move to cut per region (V.Ivanchenko)
45// 27-01-03 Make models region aware (V.Ivanchenko)
46// 13-02-03 Add name (V.Ivanchenko)
47// 08-04-05 Major optimisation of internal interfaces (V.Ivantchenko)
48// 25-07-05 Add protection in calculation of recoil direction for the case
49// of complete energy transfer from e+ to e- (V.Ivanchenko)
50// 06-02-06 ComputeCrossSectionPerElectron, ComputeCrossSectionPerAtom (mma)
51// 15-05-06 Fix MinEnergyCut (V.Ivanchenko)
52//
53//
54// Class Description:
55//
56// Implementation of energy loss and delta-electron production by e+/e-
57//
58// -------------------------------------------------------------------
59//
60//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
61//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
62
63#include "G4MollerBhabhaModel.hh"
64#include "G4Electron.hh"
65#include "G4Positron.hh"
66#include "Randomize.hh"
67#include "G4ParticleChangeForLoss.hh"
68
69//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
70
71using namespace std;
72
73G4MollerBhabhaModel::G4MollerBhabhaModel(const G4ParticleDefinition* p,
74 const G4String& nam)
75 : G4VEmModel(nam),
[1055]76 particle(0),
77 isElectron(true),
78 twoln10(2.0*log(10.0)),
79 lowLimit(0.2*keV),
80 isInitialised(false)
[819]81{
82 theElectron = G4Electron::Electron();
83 if(p) SetParticle(p);
84}
85
86//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
87
88G4MollerBhabhaModel::~G4MollerBhabhaModel()
89{}
90
91//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
92
93G4double G4MollerBhabhaModel::MinEnergyCut(const G4ParticleDefinition*,
[1315]94 const G4MaterialCutsCouple* /*couple*/)
[819]95{
[1315]96 // G4double electronDensity = couple->GetMaterial()->GetElectronDensity();
97 //G4double Zeff = electronDensity/couple->GetMaterial()->GetTotNbOfAtomsPerVolume();
98 //return 0.25*sqrt(Zeff)*keV;
99 //return couple->GetMaterial()->GetIonisation()->GetMeanExcitationEnergy();
100 return 0.1*keV;
[819]101}
102
103//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
104
[1055]105G4double G4MollerBhabhaModel::MaxSecondaryEnergy(const G4ParticleDefinition*,
106 G4double kinEnergy)
107{
108 G4double tmax = kinEnergy;
109 if(isElectron) tmax *= 0.5;
110 return tmax;
111}
112
113//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
114
[819]115void G4MollerBhabhaModel::Initialise(const G4ParticleDefinition* p,
116 const G4DataVector&)
117{
118 if(!particle) SetParticle(p);
[1055]119 SetDeexcitationFlag(false);
120
121 if(isInitialised) return;
122
123 isInitialised = true;
124 fParticleChange = GetParticleChangeForLoss();
[819]125}
126
127//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
128
129G4double G4MollerBhabhaModel::ComputeCrossSectionPerElectron(
130 const G4ParticleDefinition* p,
131 G4double kineticEnergy,
132 G4double cutEnergy,
133 G4double maxEnergy)
134{
135 if(!particle) SetParticle(p);
136
137 G4double cross = 0.0;
138 G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
139 tmax = min(maxEnergy, tmax);
140
141 if(cutEnergy < tmax) {
142
143 G4double xmin = cutEnergy/kineticEnergy;
144 G4double xmax = tmax/kineticEnergy;
145 G4double gam = kineticEnergy/electron_mass_c2 + 1.0;
146 G4double gamma2= gam*gam;
147 G4double beta2 = 1.0 - 1.0/gamma2;
148
149 //Moller (e-e-) scattering
150 if (isElectron) {
151
152 G4double g = (2.0*gam - 1.0)/gamma2;
153 cross = ((xmax - xmin)*(1.0 - g + 1.0/(xmin*xmax)
154 + 1.0/((1.0-xmin)*(1.0 - xmax)))
155 - g*log( xmax*(1.0 - xmin)/(xmin*(1.0 - xmax)) ) ) / beta2;
156
157 //Bhabha (e+e-) scattering
158 } else {
159
160 G4double y = 1.0/(1.0 + gam);
161 G4double y2 = y*y;
162 G4double y12 = 1.0 - 2.0*y;
163 G4double b1 = 2.0 - y2;
164 G4double b2 = y12*(3.0 + y2);
165 G4double y122= y12*y12;
166 G4double b4 = y122*y12;
167 G4double b3 = b4 + y122;
168
169 cross = (xmax - xmin)*(1.0/(beta2*xmin*xmax) + b2
170 - 0.5*b3*(xmin + xmax)
171 + b4*(xmin*xmin + xmin*xmax + xmax*xmax)/3.0)
172 - b1*log(xmax/xmin);
173 }
174
175 cross *= twopi_mc2_rcl2/kineticEnergy;
176 }
177 return cross;
178}
179
180//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
181
182G4double G4MollerBhabhaModel::ComputeCrossSectionPerAtom(
183 const G4ParticleDefinition* p,
184 G4double kineticEnergy,
185 G4double Z, G4double,
186 G4double cutEnergy,
187 G4double maxEnergy)
188{
189 G4double cross = Z*ComputeCrossSectionPerElectron
190 (p,kineticEnergy,cutEnergy,maxEnergy);
191 return cross;
192}
193
194//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
195
196G4double G4MollerBhabhaModel::CrossSectionPerVolume(
197 const G4Material* material,
198 const G4ParticleDefinition* p,
199 G4double kineticEnergy,
200 G4double cutEnergy,
201 G4double maxEnergy)
202{
203 G4double eDensity = material->GetElectronDensity();
204 G4double cross = eDensity*ComputeCrossSectionPerElectron
205 (p,kineticEnergy,cutEnergy,maxEnergy);
206 return cross;
207}
208
209//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
210
211G4double G4MollerBhabhaModel::ComputeDEDXPerVolume(
212 const G4Material* material,
213 const G4ParticleDefinition* p,
214 G4double kineticEnergy,
215 G4double cutEnergy)
216{
217 if(!particle) SetParticle(p);
218 // calculate the dE/dx due to the ionization by Seltzer-Berger formula
219
220 G4double electronDensity = material->GetElectronDensity();
221 G4double Zeff = electronDensity/material->GetTotNbOfAtomsPerVolume();
222 G4double th = 0.25*sqrt(Zeff)*keV;
223 G4double tkin = kineticEnergy;
224 G4bool lowEnergy = false;
225 if (kineticEnergy < th) {
226 tkin = th;
227 lowEnergy = true;
228 }
229 G4double tau = tkin/electron_mass_c2;
230 G4double gam = tau + 1.0;
231 G4double gamma2= gam*gam;
232 G4double beta2 = 1. - 1./gamma2;
233 G4double bg2 = beta2*gamma2;
234
235 G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy();
236 eexc /= electron_mass_c2;
237 G4double eexc2 = eexc*eexc;
238
239 G4double d = min(cutEnergy, MaxSecondaryEnergy(p, tkin))/electron_mass_c2;
240 G4double dedx;
241
242 // electron
243 if (isElectron) {
244
245 dedx = log(2.0*(tau + 2.0)/eexc2) - 1.0 - beta2
246 + log((tau-d)*d) + tau/(tau-d)
247 + (0.5*d*d + (2.0*tau + 1.)*log(1. - d/tau))/gamma2;
248
249 //positron
250 } else {
251
252 G4double d2 = d*d*0.5;
253 G4double d3 = d2*d/1.5;
254 G4double d4 = d3*d*3.75;
255 G4double y = 1.0/(1.0 + gam);
256 dedx = log(2.0*(tau + 2.0)/eexc2) + log(tau*d)
257 - beta2*(tau + 2.0*d - y*(3.0*d2
258 + y*(d - d3 + y*(d2 - tau*d3 + d4))))/tau;
259 }
260
261 //density correction
[1196]262 //G4double cden = material->GetIonisation()->GetCdensity();
263 //G4double mden = material->GetIonisation()->GetMdensity();
264 //G4double aden = material->GetIonisation()->GetAdensity();
265 //G4double x0den = material->GetIonisation()->GetX0density();
266 //G4double x1den = material->GetIonisation()->GetX1density();
[819]267 G4double x = log(bg2)/twoln10;
268
[1196]269 //if (x >= x0den) {
270 // dedx -= twoln10*x - cden;
271 // if (x < x1den) dedx -= aden*pow(x1den-x, mden);
272 //}
273 dedx -= material->GetIonisation()->DensityCorrection(x);
[819]274
275 // now you can compute the total ionization loss
276 dedx *= twopi_mc2_rcl2*electronDensity/beta2;
277 if (dedx < 0.0) dedx = 0.0;
278
279 // lowenergy extrapolation
280
281 if (lowEnergy) {
282
283 if (kineticEnergy >= lowLimit) dedx *= sqrt(tkin/kineticEnergy);
284 else dedx *= sqrt(tkin*kineticEnergy)/lowLimit;
285
286 }
287 return dedx;
288}
289
290//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
291
292void G4MollerBhabhaModel::SampleSecondaries(std::vector<G4DynamicParticle*>* vdp,
293 const G4MaterialCutsCouple*,
294 const G4DynamicParticle* dp,
295 G4double tmin,
296 G4double maxEnergy)
297{
[1055]298 G4double kineticEnergy = dp->GetKineticEnergy();
299 G4double tmax = kineticEnergy;
300 if(isElectron) tmax *= 0.5;
301 if(maxEnergy < tmax) tmax = maxEnergy;
[819]302 if(tmin >= tmax) return;
303
304 G4double energy = kineticEnergy + electron_mass_c2;
305 G4double totalMomentum = sqrt(kineticEnergy*(energy + electron_mass_c2));
306 G4double xmin = tmin/kineticEnergy;
307 G4double xmax = tmax/kineticEnergy;
308 G4double gam = energy/electron_mass_c2;
309 G4double gamma2 = gam*gam;
310 G4double beta2 = 1.0 - 1.0/gamma2;
311 G4double x, z, q, grej;
312
313 G4ThreeVector direction = dp->GetMomentumDirection();
314
315 //Moller (e-e-) scattering
316 if (isElectron) {
317
318 G4double g = (2.0*gam - 1.0)/gamma2;
319 G4double y = 1.0 - xmax;
320 grej = 1.0 - g*xmax + xmax*xmax*(1.0 - g + (1.0 - g*y)/(y*y));
321
322 do {
323 q = G4UniformRand();
324 x = xmin*xmax/(xmin*(1.0 - q) + xmax*q);
325 y = 1.0 - x;
326 z = 1.0 - g*x + x*x*(1.0 - g + (1.0 - g*y)/(y*y));
327 /*
328 if(z > grej) {
329 G4cout << "G4MollerBhabhaModel::SampleSecondary Warning! "
330 << "Majorant " << grej << " < "
331 << z << " for x= " << x
332 << " e-e- scattering"
333 << G4endl;
334 }
335 */
336 } while(grej * G4UniformRand() > z);
337
338 //Bhabha (e+e-) scattering
339 } else {
340
341 G4double y = 1.0/(1.0 + gam);
342 G4double y2 = y*y;
343 G4double y12 = 1.0 - 2.0*y;
344 G4double b1 = 2.0 - y2;
345 G4double b2 = y12*(3.0 + y2);
346 G4double y122= y12*y12;
347 G4double b4 = y122*y12;
348 G4double b3 = b4 + y122;
349
[1055]350 y = xmax*xmax;
351 grej = 1.0 + (y*y*b4 - xmin*xmin*xmin*b3 + y*b2 - xmin*b1)*beta2;
[819]352 do {
[1055]353 q = G4UniformRand();
354 x = xmin*xmax/(xmin*(1.0 - q) + xmax*q);
355 y = x*x;
356 z = 1.0 + (y*y*b4 - x*y*b3 + y*b2 - x*b1)*beta2;
[819]357 /*
358 if(z > grej) {
359 G4cout << "G4MollerBhabhaModel::SampleSecondary Warning! "
360 << "Majorant " << grej << " < "
361 << z << " for x= " << x
362 << " e+e- scattering"
363 << G4endl;
364 }
365 */
366 } while(grej * G4UniformRand() > z);
367 }
368
369 G4double deltaKinEnergy = x * kineticEnergy;
370
371 G4double deltaMomentum =
372 sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
373 G4double cost = deltaKinEnergy * (energy + electron_mass_c2) /
374 (deltaMomentum * totalMomentum);
375 G4double sint = 1.0 - cost*cost;
376 if(sint > 0.0) sint = sqrt(sint);
377
378 G4double phi = twopi * G4UniformRand() ;
379
380 G4ThreeVector deltaDirection(sint*cos(phi),sint*sin(phi), cost) ;
381 deltaDirection.rotateUz(direction);
382
383 // primary change
384 kineticEnergy -= deltaKinEnergy;
385 fParticleChange->SetProposedKineticEnergy(kineticEnergy);
386
387 if(kineticEnergy > DBL_MIN) {
388 G4ThreeVector dir = totalMomentum*direction - deltaMomentum*deltaDirection;
389 direction = dir.unit();
390 fParticleChange->SetProposedMomentumDirection(direction);
391 }
392
393 // create G4DynamicParticle object for delta ray
394 G4DynamicParticle* delta = new G4DynamicParticle(theElectron,
[1055]395 deltaDirection,deltaKinEnergy);
[819]396 vdp->push_back(delta);
397}
398
399//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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