source: trunk/source/processes/electromagnetic/standard/src/G4MollerBhabhaModel.cc @ 1250

Last change on this file since 1250 was 1228, checked in by garnier, 15 years ago

update geant4.9.3 tag
File size: 13.5 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 1.35 2009/11/09 19:16:13 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-03 $
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  fParticleChange = GetParticleChangeForLoss();
123}
124
125//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
126
127G4double G4MollerBhabhaModel::ComputeCrossSectionPerElectron(
128                                           const G4ParticleDefinition* p,
129                                                 G4double kineticEnergy,
130                                                 G4double cutEnergy,
131                                                 G4double maxEnergy)
132{
133  if(!particle) SetParticle(p);
134
135  G4double cross = 0.0;
136  G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
137  tmax = min(maxEnergy, tmax);
138
139  if(cutEnergy < tmax) {
140
141    G4double xmin  = cutEnergy/kineticEnergy;
142    G4double xmax  = tmax/kineticEnergy;
143    G4double gam   = kineticEnergy/electron_mass_c2 + 1.0;
144    G4double gamma2= gam*gam;
145    G4double beta2 = 1.0 - 1.0/gamma2;
146
147    //Moller (e-e-) scattering
148    if (isElectron) {
149
150      G4double g     = (2.0*gam - 1.0)/gamma2;
151      cross = ((xmax - xmin)*(1.0 - g + 1.0/(xmin*xmax)
152                              + 1.0/((1.0-xmin)*(1.0 - xmax)))
153            - g*log( xmax*(1.0 - xmin)/(xmin*(1.0 - xmax)) ) ) / beta2;
154
155    //Bhabha (e+e-) scattering
156    } else {
157
158      G4double y   = 1.0/(1.0 + gam);
159      G4double y2  = y*y;
160      G4double y12 = 1.0 - 2.0*y;
161      G4double b1  = 2.0 - y2;
162      G4double b2  = y12*(3.0 + y2);
163      G4double y122= y12*y12;
164      G4double b4  = y122*y12;
165      G4double b3  = b4 + y122;
166
167      cross = (xmax - xmin)*(1.0/(beta2*xmin*xmax) + b2
168            - 0.5*b3*(xmin + xmax)
169            + b4*(xmin*xmin + xmin*xmax + xmax*xmax)/3.0)
170            - b1*log(xmax/xmin);
171    }
172
173    cross *= twopi_mc2_rcl2/kineticEnergy;
174  }
175  return cross;
176}
177
178//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
179
180G4double G4MollerBhabhaModel::ComputeCrossSectionPerAtom(
181                                           const G4ParticleDefinition* p,
182                                                 G4double kineticEnergy,
183                                                 G4double Z, G4double,
184                                                 G4double cutEnergy,
185                                                 G4double maxEnergy)
186{
187  G4double cross = Z*ComputeCrossSectionPerElectron
188                                         (p,kineticEnergy,cutEnergy,maxEnergy);
189  return cross;
190}
191
192//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
193
194G4double G4MollerBhabhaModel::CrossSectionPerVolume(
195                                           const G4Material* material,
196                                           const G4ParticleDefinition* p,
197                                                 G4double kineticEnergy,
198                                                 G4double cutEnergy,
199                                                 G4double maxEnergy)
200{
201  G4double eDensity = material->GetElectronDensity();
202  G4double cross = eDensity*ComputeCrossSectionPerElectron
203                                         (p,kineticEnergy,cutEnergy,maxEnergy);
204  return cross;
205}
206
207//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
208
209G4double G4MollerBhabhaModel::ComputeDEDXPerVolume(
210                                          const G4Material* material,
211                                          const G4ParticleDefinition* p,
212                                                G4double kineticEnergy,
213                                                G4double cutEnergy)
214{
215  if(!particle) SetParticle(p);
216  // calculate the dE/dx due to the ionization by Seltzer-Berger formula
217 
218  G4double electronDensity = material->GetElectronDensity();
219  G4double Zeff  = electronDensity/material->GetTotNbOfAtomsPerVolume();
220  G4double th    = 0.25*sqrt(Zeff)*keV;
221  G4double tkin  = kineticEnergy;
222  G4bool   lowEnergy = false;
223  if (kineticEnergy < th) {
224    tkin = th;
225    lowEnergy = true;
226  }
227  G4double tau   = tkin/electron_mass_c2;
228  G4double gam   = tau + 1.0;
229  G4double gamma2= gam*gam;
230  G4double beta2 = 1. - 1./gamma2;
231  G4double bg2   = beta2*gamma2;
232
233  G4double eexc  = material->GetIonisation()->GetMeanExcitationEnergy();
234  eexc          /= electron_mass_c2;
235  G4double eexc2 = eexc*eexc; 
236
237  G4double d = min(cutEnergy, MaxSecondaryEnergy(p, tkin))/electron_mass_c2;
238  G4double dedx;
239
240  // electron
241  if (isElectron) {
242
243    dedx = log(2.0*(tau + 2.0)/eexc2) - 1.0 - beta2
244         + log((tau-d)*d) + tau/(tau-d)
245         + (0.5*d*d + (2.0*tau + 1.)*log(1. - d/tau))/gamma2;
246   
247  //positron
248  } else {
249
250    G4double d2 = d*d*0.5;
251    G4double d3 = d2*d/1.5;
252    G4double d4 = d3*d*3.75;
253    G4double y  = 1.0/(1.0 + gam);
254    dedx = log(2.0*(tau + 2.0)/eexc2) + log(tau*d)
255         - beta2*(tau + 2.0*d - y*(3.0*d2
256         + y*(d - d3 + y*(d2 - tau*d3 + d4))))/tau;
257  } 
258
259  //density correction
260  //G4double cden  = material->GetIonisation()->GetCdensity();
261  //G4double mden  = material->GetIonisation()->GetMdensity();
262  //G4double aden  = material->GetIonisation()->GetAdensity();
263  //G4double x0den = material->GetIonisation()->GetX0density();
264  //G4double x1den = material->GetIonisation()->GetX1density();
265  G4double x     = log(bg2)/twoln10;
266
267  //if (x >= x0den) {
268  //  dedx -= twoln10*x - cden;
269  //  if (x < x1den) dedx -= aden*pow(x1den-x, mden);
270  //}
271  dedx -= material->GetIonisation()->DensityCorrection(x); 
272
273  // now you can compute the total ionization loss
274  dedx *= twopi_mc2_rcl2*electronDensity/beta2;
275  if (dedx < 0.0) dedx = 0.0;
276
277  // lowenergy extrapolation
278
279  if (lowEnergy) {
280
281    if (kineticEnergy >= lowLimit) dedx *= sqrt(tkin/kineticEnergy);
282    else                           dedx *= sqrt(tkin*kineticEnergy)/lowLimit;
283
284  }
285  return dedx;
286}
287
288//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
289
290void G4MollerBhabhaModel::SampleSecondaries(std::vector<G4DynamicParticle*>* vdp,
291                                            const G4MaterialCutsCouple*,
292                                            const G4DynamicParticle* dp,
293                                            G4double tmin,
294                                            G4double maxEnergy)
295{
296  G4double kineticEnergy = dp->GetKineticEnergy();
297  G4double tmax = kineticEnergy;
298  if(isElectron) tmax *= 0.5;
299  if(maxEnergy < tmax) tmax = maxEnergy;
300  if(tmin >= tmax) return;
301
302  G4double energy = kineticEnergy + electron_mass_c2;
303  G4double totalMomentum = sqrt(kineticEnergy*(energy + electron_mass_c2));
304  G4double xmin   = tmin/kineticEnergy;
305  G4double xmax   = tmax/kineticEnergy;
306  G4double gam    = energy/electron_mass_c2;
307  G4double gamma2 = gam*gam;
308  G4double beta2  = 1.0 - 1.0/gamma2;
309  G4double x, z, q, grej;
310
311  G4ThreeVector direction = dp->GetMomentumDirection();
312
313  //Moller (e-e-) scattering
314  if (isElectron) {
315
316    G4double g = (2.0*gam - 1.0)/gamma2;
317    G4double y = 1.0 - xmax;
318    grej = 1.0 - g*xmax + xmax*xmax*(1.0 - g + (1.0 - g*y)/(y*y));
319
320    do {
321      q = G4UniformRand();
322      x = xmin*xmax/(xmin*(1.0 - q) + xmax*q);
323      y = 1.0 - x;
324      z = 1.0 - g*x + x*x*(1.0 - g + (1.0 - g*y)/(y*y));
325      /*
326      if(z > grej) {
327        G4cout << "G4MollerBhabhaModel::SampleSecondary Warning! "
328               << "Majorant " << grej << " < "
329               << z << " for x= " << x
330               << " e-e- scattering"
331               << G4endl;
332      }
333      */
334    } while(grej * G4UniformRand() > z);
335
336  //Bhabha (e+e-) scattering
337  } else {
338
339    G4double y   = 1.0/(1.0 + gam);
340    G4double y2  = y*y;
341    G4double y12 = 1.0 - 2.0*y;
342    G4double b1  = 2.0 - y2;
343    G4double b2  = y12*(3.0 + y2);
344    G4double y122= y12*y12;
345    G4double b4  = y122*y12;
346    G4double b3  = b4 + y122;
347
348    y    = xmax*xmax;
349    grej = 1.0 + (y*y*b4 - xmin*xmin*xmin*b3 + y*b2 - xmin*b1)*beta2; 
350    do {
351      q = G4UniformRand();
352      x = xmin*xmax/(xmin*(1.0 - q) + xmax*q);
353      y = x*x;
354      z = 1.0 + (y*y*b4 - x*y*b3 + y*b2 - x*b1)*beta2; 
355      /*
356      if(z > grej) {
357        G4cout << "G4MollerBhabhaModel::SampleSecondary Warning! "
358               << "Majorant " << grej << " < "
359               << z << " for x= " << x
360               << " e+e- scattering"
361               << G4endl;
362      }
363      */
364    } while(grej * G4UniformRand() > z);
365  }
366
367  G4double deltaKinEnergy = x * kineticEnergy;
368
369  G4double deltaMomentum =
370           sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
371  G4double cost = deltaKinEnergy * (energy + electron_mass_c2) /
372                                   (deltaMomentum * totalMomentum);
373  G4double sint = 1.0 - cost*cost;
374  if(sint > 0.0) sint = sqrt(sint);
375
376  G4double phi = twopi * G4UniformRand() ;
377
378  G4ThreeVector deltaDirection(sint*cos(phi),sint*sin(phi), cost) ;
379  deltaDirection.rotateUz(direction);
380
381  // primary change
382  kineticEnergy -= deltaKinEnergy;
383  fParticleChange->SetProposedKineticEnergy(kineticEnergy);
384
385  if(kineticEnergy > DBL_MIN) {
386    G4ThreeVector dir = totalMomentum*direction - deltaMomentum*deltaDirection;
387    direction = dir.unit();
388    fParticleChange->SetProposedMomentumDirection(direction);
389  }
390
391  // create G4DynamicParticle object for delta ray
392  G4DynamicParticle* delta = new G4DynamicParticle(theElectron,
393                                                   deltaDirection,deltaKinEnergy);
394  vdp->push_back(delta);
395}
396
397//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
Note: See TracBrowser for help on using the repository browser.