source: trunk/source/processes/electromagnetic/standard/src/G4MollerBhabhaModel.cc@ 1005

Last change on this file since 1005 was 1005, checked in by garnier, 17 years ago

fichier oublies
File size: 13.7 KB
Line 
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// $Id: G4MollerBhabhaModel.cc,v 1.31 2009/02/20 12:06:37 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-02-ref-02 $
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),
76 particle(0),
77 isElectron(true),
78 twoln10(2.0*log(10.0)),
79 lowLimit(0.2*keV),
80 isInitialised(false)
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*,
94 const G4MaterialCutsCouple* couple)
95{
96 G4double electronDensity = couple->GetMaterial()->GetElectronDensity();
97 G4double Zeff = electronDensity/couple->GetMaterial()->GetTotNbOfAtomsPerVolume();
98 return 0.25*sqrt(Zeff)*keV;
99}
100
101//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
102
103G4double G4MollerBhabhaModel::MaxSecondaryEnergy(const G4ParticleDefinition*,
104 G4double kinEnergy)
105{
106 G4double tmax = kinEnergy;
107 if(isElectron) tmax *= 0.5;
108 return tmax;
109}
110
111//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
112
113void G4MollerBhabhaModel::Initialise(const G4ParticleDefinition* p,
114 const G4DataVector&)
115{
116 if(!particle) SetParticle(p);
117 SetDeexcitationFlag(false);
118
119 if(isInitialised) return;
120
121 isInitialised = true;
122 if(pParticleChange) {
123 fParticleChange = reinterpret_cast<G4ParticleChangeForLoss*>
124 (pParticleChange);
125 } else {
126 fParticleChange = new G4ParticleChangeForLoss();
127 }
128}
129
130//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
131
132G4double G4MollerBhabhaModel::ComputeCrossSectionPerElectron(
133 const G4ParticleDefinition* p,
134 G4double kineticEnergy,
135 G4double cutEnergy,
136 G4double maxEnergy)
137{
138 if(!particle) SetParticle(p);
139
140 G4double cross = 0.0;
141 G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
142 tmax = min(maxEnergy, tmax);
143
144 if(cutEnergy < tmax) {
145
146 G4double xmin = cutEnergy/kineticEnergy;
147 G4double xmax = tmax/kineticEnergy;
148 G4double gam = kineticEnergy/electron_mass_c2 + 1.0;
149 G4double gamma2= gam*gam;
150 G4double beta2 = 1.0 - 1.0/gamma2;
151
152 //Moller (e-e-) scattering
153 if (isElectron) {
154
155 G4double g = (2.0*gam - 1.0)/gamma2;
156 cross = ((xmax - xmin)*(1.0 - g + 1.0/(xmin*xmax)
157 + 1.0/((1.0-xmin)*(1.0 - xmax)))
158 - g*log( xmax*(1.0 - xmin)/(xmin*(1.0 - xmax)) ) ) / beta2;
159
160 //Bhabha (e+e-) scattering
161 } else {
162
163 G4double y = 1.0/(1.0 + gam);
164 G4double y2 = y*y;
165 G4double y12 = 1.0 - 2.0*y;
166 G4double b1 = 2.0 - y2;
167 G4double b2 = y12*(3.0 + y2);
168 G4double y122= y12*y12;
169 G4double b4 = y122*y12;
170 G4double b3 = b4 + y122;
171
172 cross = (xmax - xmin)*(1.0/(beta2*xmin*xmax) + b2
173 - 0.5*b3*(xmin + xmax)
174 + b4*(xmin*xmin + xmin*xmax + xmax*xmax)/3.0)
175 - b1*log(xmax/xmin);
176 }
177
178 cross *= twopi_mc2_rcl2/kineticEnergy;
179 }
180 return cross;
181}
182
183//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
184
185G4double G4MollerBhabhaModel::ComputeCrossSectionPerAtom(
186 const G4ParticleDefinition* p,
187 G4double kineticEnergy,
188 G4double Z, G4double,
189 G4double cutEnergy,
190 G4double maxEnergy)
191{
192 G4double cross = Z*ComputeCrossSectionPerElectron
193 (p,kineticEnergy,cutEnergy,maxEnergy);
194 return cross;
195}
196
197//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
198
199G4double G4MollerBhabhaModel::CrossSectionPerVolume(
200 const G4Material* material,
201 const G4ParticleDefinition* p,
202 G4double kineticEnergy,
203 G4double cutEnergy,
204 G4double maxEnergy)
205{
206 G4double eDensity = material->GetElectronDensity();
207 G4double cross = eDensity*ComputeCrossSectionPerElectron
208 (p,kineticEnergy,cutEnergy,maxEnergy);
209 return cross;
210}
211
212//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
213
214G4double G4MollerBhabhaModel::ComputeDEDXPerVolume(
215 const G4Material* material,
216 const G4ParticleDefinition* p,
217 G4double kineticEnergy,
218 G4double cutEnergy)
219{
220 if(!particle) SetParticle(p);
221 // calculate the dE/dx due to the ionization by Seltzer-Berger formula
222
223 G4double electronDensity = material->GetElectronDensity();
224 G4double Zeff = electronDensity/material->GetTotNbOfAtomsPerVolume();
225 G4double th = 0.25*sqrt(Zeff)*keV;
226 G4double tkin = kineticEnergy;
227 G4bool lowEnergy = false;
228 if (kineticEnergy < th) {
229 tkin = th;
230 lowEnergy = true;
231 }
232 G4double tau = tkin/electron_mass_c2;
233 G4double gam = tau + 1.0;
234 G4double gamma2= gam*gam;
235 G4double beta2 = 1. - 1./gamma2;
236 G4double bg2 = beta2*gamma2;
237
238 G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy();
239 eexc /= electron_mass_c2;
240 G4double eexc2 = eexc*eexc;
241
242 G4double d = min(cutEnergy, MaxSecondaryEnergy(p, tkin))/electron_mass_c2;
243 G4double dedx;
244
245 // electron
246 if (isElectron) {
247
248 dedx = log(2.0*(tau + 2.0)/eexc2) - 1.0 - beta2
249 + log((tau-d)*d) + tau/(tau-d)
250 + (0.5*d*d + (2.0*tau + 1.)*log(1. - d/tau))/gamma2;
251
252 //positron
253 } else {
254
255 G4double d2 = d*d*0.5;
256 G4double d3 = d2*d/1.5;
257 G4double d4 = d3*d*3.75;
258 G4double y = 1.0/(1.0 + gam);
259 dedx = log(2.0*(tau + 2.0)/eexc2) + log(tau*d)
260 - beta2*(tau + 2.0*d - y*(3.0*d2
261 + y*(d - d3 + y*(d2 - tau*d3 + d4))))/tau;
262 }
263
264 //density correction
265 G4double cden = material->GetIonisation()->GetCdensity();
266 G4double mden = material->GetIonisation()->GetMdensity();
267 G4double aden = material->GetIonisation()->GetAdensity();
268 G4double x0den = material->GetIonisation()->GetX0density();
269 G4double x1den = material->GetIonisation()->GetX1density();
270 G4double x = log(bg2)/twoln10;
271
272 if (x >= x0den) {
273 dedx -= twoln10*x - cden;
274 if (x < x1den) dedx -= aden*pow(x1den-x, mden);
275 }
276
277 // now you can compute the total ionization loss
278 dedx *= twopi_mc2_rcl2*electronDensity/beta2;
279 if (dedx < 0.0) dedx = 0.0;
280
281 // lowenergy extrapolation
282
283 if (lowEnergy) {
284
285 if (kineticEnergy >= lowLimit) dedx *= sqrt(tkin/kineticEnergy);
286 else dedx *= sqrt(tkin*kineticEnergy)/lowLimit;
287
288 }
289 return dedx;
290}
291
292//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
293
294void G4MollerBhabhaModel::SampleSecondaries(std::vector<G4DynamicParticle*>* vdp,
295 const G4MaterialCutsCouple*,
296 const G4DynamicParticle* dp,
297 G4double tmin,
298 G4double maxEnergy)
299{
300 G4double tmax = std::min(maxEnergy, MaxSecondaryKinEnergy(dp));
301 if(tmin >= tmax) return;
302
303 G4double kineticEnergy = dp->GetKineticEnergy();
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
350 y = xmax*xmax;
351 grej = -xmin*b1;
352 grej += y*b2;
353 grej -= xmin*xmin*xmin*b3;
354 grej += y*y*b4;
355 grej *= beta2;
356 grej += 1.0;
357 do {
358 q = G4UniformRand();
359 x = xmin*xmax/(xmin*(1.0 - q) + xmax*q);
360 z = -x*b1;
361 y = x*x;
362 z += y*b2;
363 y *= x;
364 z -= y*b3;
365 y *= x;
366 z += y*b4;
367 z *= beta2;
368 z += 1.0;
369 /*
370 if(z > grej) {
371 G4cout << "G4MollerBhabhaModel::SampleSecondary Warning! "
372 << "Majorant " << grej << " < "
373 << z << " for x= " << x
374 << " e+e- scattering"
375 << G4endl;
376 }
377 */
378 } while(grej * G4UniformRand() > z);
379 }
380
381 G4double deltaKinEnergy = x * kineticEnergy;
382
383 G4double deltaMomentum =
384 sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
385 G4double cost = deltaKinEnergy * (energy + electron_mass_c2) /
386 (deltaMomentum * totalMomentum);
387 G4double sint = 1.0 - cost*cost;
388 if(sint > 0.0) sint = sqrt(sint);
389
390 G4double phi = twopi * G4UniformRand() ;
391
392 G4ThreeVector deltaDirection(sint*cos(phi),sint*sin(phi), cost) ;
393 deltaDirection.rotateUz(direction);
394
395 // primary change
396 kineticEnergy -= deltaKinEnergy;
397 fParticleChange->SetProposedKineticEnergy(kineticEnergy);
398
399 if(kineticEnergy > DBL_MIN) {
400 G4ThreeVector dir = totalMomentum*direction - deltaMomentum*deltaDirection;
401 direction = dir.unit();
402 fParticleChange->SetProposedMomentumDirection(direction);
403 }
404
405 // create G4DynamicParticle object for delta ray
406 G4DynamicParticle* delta = new G4DynamicParticle(theElectron,
407 deltaDirection,deltaKinEnergy);
408 vdp->push_back(delta);
409}
410
411//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
Note: See TracBrowser for help on using the repository browser.