source: trunk/source/processes/electromagnetic/standard/src/G4HeatedKleinNishinaCompton.cc @ 1058

Last change on this file since 1058 was 1058, checked in by garnier, 15 years ago

file release beta
File size: 9.7 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: G4HeatedKleinNishinaCompton.cc,v 1.5 2009/04/12 17:09:57 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-03-beta-cand-01 $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class file
32//
33//
34// File name:     G4HeatedKleinNishinaCompton
35//
36// Author:        Vladimir Grichine on base of M. Maire and V. Ivanchenko code
37//
38// Creation date: 15.03.2009
39//
40// Modifications:
41//
42//
43// Class Description:
44//
45// -------------------------------------------------------------------
46//
47//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
48//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
49
50#include <CLHEP/Random/RandGamma.h>
51#include "globals.hh"
52#include "G4RandomDirection.hh"
53#include "Randomize.hh"
54
55#include "G4HeatedKleinNishinaCompton.hh"
56#include "G4Electron.hh"
57#include "G4Gamma.hh"
58#include "Randomize.hh"
59#include "G4DataVector.hh"
60#include "G4ParticleChangeForGamma.hh"
61
62//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
63
64using namespace std;
65
66G4HeatedKleinNishinaCompton::G4HeatedKleinNishinaCompton(const G4ParticleDefinition*,
67                                             const G4String& nam)
68  : G4VEmModel(nam)
69{
70  theGamma = G4Gamma::Gamma();
71  theElectron = G4Electron::Electron();
72  lowestGammaEnergy = 1.0*eV;
73  fTemperature = 1.0*keV;
74  fParticleChange = 0;
75}
76
77//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
78
79G4HeatedKleinNishinaCompton::~G4HeatedKleinNishinaCompton()
80{}
81
82//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
83
84void G4HeatedKleinNishinaCompton::Initialise(const G4ParticleDefinition*,
85                                       const G4DataVector&)
86{
87  if(!fParticleChange) fParticleChange = GetParticleChangeForGamma();
88}
89
90////////////////////////////////////////////////////////////////////////////
91//
92//
93
94G4double G4HeatedKleinNishinaCompton::ComputeCrossSectionPerAtom(
95                                       const G4ParticleDefinition*,
96                                             G4double GammaEnergy,
97                                             G4double Z, G4double,
98                                             G4double, G4double)
99{
100  G4double CrossSection = 0.0 ;
101  if ( Z < 0.9999 )                 return CrossSection;
102  if ( GammaEnergy < 0.01*keV      ) return CrossSection;
103  //  if ( GammaEnergy > (100.*GeV/Z) ) return CrossSection;
104
105  static const G4double a = 20.0 , b = 230.0 , c = 440.0;
106 
107  static const G4double
108    d1= 2.7965e-1*barn, d2=-1.8300e-1*barn, d3= 6.7527   *barn, d4=-1.9798e+1*barn,
109    e1= 1.9756e-5*barn, e2=-1.0205e-2*barn, e3=-7.3913e-2*barn, e4= 2.7079e-2*barn,
110    f1=-3.9178e-7*barn, f2= 6.8241e-5*barn, f3= 6.0480e-5*barn, f4= 3.0274e-4*barn;
111     
112  G4double p1Z = Z*(d1 + e1*Z + f1*Z*Z), p2Z = Z*(d2 + e2*Z + f2*Z*Z),
113           p3Z = Z*(d3 + e3*Z + f3*Z*Z), p4Z = Z*(d4 + e4*Z + f4*Z*Z);
114
115  G4double T0  = 15.0*keV; 
116  if (Z < 1.5) T0 = 40.0*keV; 
117
118  G4double X   = max(GammaEnergy, T0) / electron_mass_c2;
119  CrossSection = p1Z*std::log(1.+2.*X)/X
120               + (p2Z + p3Z*X + p4Z*X*X)/(1. + a*X + b*X*X + c*X*X*X);
121               
122  //  modification for low energy. (special case for Hydrogen)
123  if (GammaEnergy < T0) {
124    G4double dT0 = 1.*keV;
125    X = (T0+dT0) / electron_mass_c2 ;
126    G4double sigma = p1Z*log(1.+2*X)/X
127                    + (p2Z + p3Z*X + p4Z*X*X)/(1. + a*X + b*X*X + c*X*X*X);
128    G4double   c1 = -T0*(sigma-CrossSection)/(CrossSection*dT0);             
129    G4double   c2 = 0.150; 
130    if (Z > 1.5) c2 = 0.375-0.0556*log(Z);
131    G4double    y = log(GammaEnergy/T0);
132    CrossSection *= exp(-y*(c1+c2*y));         
133  }
134  //  G4cout << "e= " << GammaEnergy << " Z= " << Z << " cross= " << CrossSection << G4endl;
135  return CrossSection;
136}
137
138//////////////////////////////////////////////////////////////////////////
139//
140//
141
142void G4HeatedKleinNishinaCompton::SampleSecondaries(std::vector<G4DynamicParticle*>* fvect,
143                                              const G4MaterialCutsCouple*,
144                                              const G4DynamicParticle* aDynamicGamma,
145                                              G4double,
146                                              G4double)
147{
148  // The scattered gamma energy is sampled according to Klein - Nishina formula.
149  // The random number techniques of Butcher & Messel are used
150  // (Nuc Phys 20(1960),15).
151  // Note : Effects due to binding of atomic electrons are negliged.
152
153  // We start to prepare a heated electron from Maxwell distribution.
154  // Then we try to boost to the electron rest frame and make scattering.
155  // The final step is to recover new gamma 4momentum in the lab frame
156
157  G4double eMomentumC2   = CLHEP::RandGamma::shoot(1.5,1.);
158  eMomentumC2          *= 2*electron_mass_c2*fTemperature; // electron (pc)^2
159  G4ThreeVector eMomDir = G4RandomDirection();
160  eMomDir              *= std::sqrt(eMomentumC2);
161  G4double eEnergy      = std::sqrt(eMomentumC2+electron_mass_c2*electron_mass_c2);
162  G4LorentzVector electron4v = G4LorentzVector(eMomDir,eEnergy);
163  G4ThreeVector bst = electron4v.boostVector();
164
165  G4LorentzVector gamma4v = aDynamicGamma->Get4Momentum();
166  gamma4v.boost(-bst);
167
168  G4ThreeVector gammaMomV = gamma4v.vect();
169  G4double  gamEnergy0    = gammaMomV.mag();
170 
171 
172  // G4double gamEnergy0 = aDynamicGamma->GetKineticEnergy();
173  G4double E0_m = gamEnergy0 / electron_mass_c2 ;
174
175  // G4ThreeVector gamDirection0 = /aDynamicGamma->GetMomentumDirection();
176
177  G4ThreeVector gamDirection0 = gammaMomV/gamEnergy0;
178 
179  // sample the energy rate of the scattered gamma in the electron rest frame
180  //
181
182  G4double epsilon, epsilonsq, onecost, sint2, greject ;
183
184  G4double epsilon0   = 1./(1. + 2.*E0_m);
185  G4double epsilon0sq = epsilon0*epsilon0;
186  G4double alpha1     = - log(epsilon0);
187  G4double alpha2     = 0.5*(1.- epsilon0sq);
188
189  do 
190  {
191    if ( alpha1/(alpha1+alpha2) > G4UniformRand() ) 
192    {
193      epsilon   = exp(-alpha1*G4UniformRand());   // epsilon0**r
194      epsilonsq = epsilon*epsilon; 
195
196    } 
197    else 
198    {
199      epsilonsq = epsilon0sq + (1.- epsilon0sq)*G4UniformRand();
200      epsilon   = sqrt(epsilonsq);
201    };
202
203    onecost = (1.- epsilon)/(epsilon*E0_m);
204    sint2   = onecost*(2.-onecost);
205    greject = 1. - epsilon*sint2/(1.+ epsilonsq);
206
207  } while (greject < G4UniformRand());
208 
209  //
210  // scattered gamma angles. ( Z - axis along the parent gamma)
211  //
212
213  G4double cosTeta = 1. - onecost; 
214  G4double sinTeta = sqrt (sint2);
215  G4double Phi     = twopi * G4UniformRand();
216  G4double dirx    = sinTeta*cos(Phi), diry = sinTeta*sin(Phi), dirz = cosTeta;
217
218  //
219  // update G4VParticleChange for the scattered gamma
220  //
221   
222  G4ThreeVector gamDirection1 ( dirx,diry,dirz );
223  gamDirection1.rotateUz(gamDirection0);
224  G4double gamEnergy1  = epsilon*gamEnergy0;
225  gamDirection1       *= gamEnergy1;
226
227  G4LorentzVector gamma4vfinal = G4LorentzVector(gamDirection1,gamEnergy1);
228
229 
230  // kinematic of the scattered electron
231  //
232
233  G4double eKinEnergy = gamEnergy0 - gamEnergy1;
234  G4ThreeVector eDirection = gamEnergy0*gamDirection0 - gamEnergy1*gamDirection1;
235  eDirection = eDirection.unit();
236  G4double eFinalMom = std::sqrt(eKinEnergy*(eKinEnergy+2*electron_mass_c2));
237  eDirection *= eFinalMom;
238  G4LorentzVector e4vfinal = G4LorentzVector(eDirection,gamEnergy1+electron_mass_c2);
239 
240  gamma4vfinal.boost(bst);
241  e4vfinal.boost(bst);
242
243  gamDirection1 = gamma4vfinal.vect();
244  gamEnergy1 = gamDirection1.mag(); 
245  gamDirection1 /= gamEnergy1;
246
247
248
249
250  fParticleChange->SetProposedKineticEnergy(gamEnergy1);
251
252  if( gamEnergy1 > lowestGammaEnergy ) 
253  {
254    gamDirection1 /= gamEnergy1;
255    fParticleChange->ProposeMomentumDirection(gamDirection1);
256  } 
257  else 
258  { 
259    fParticleChange->ProposeTrackStatus(fStopAndKill);
260    gamEnergy1 += fParticleChange->GetLocalEnergyDeposit();
261    fParticleChange->ProposeLocalEnergyDeposit(gamEnergy1);
262  }
263
264  eKinEnergy = e4vfinal.t()-electron_mass_c2;
265
266  if( eKinEnergy > DBL_MIN ) 
267  {
268    // create G4DynamicParticle object for the electron.
269    eDirection = e4vfinal.vect();
270    G4double eFinMomMag = eDirection.mag();
271    eDirection /= eFinMomMag;
272    G4DynamicParticle* dp = new G4DynamicParticle(theElectron,eDirection,eKinEnergy);
273    fvect->push_back(dp);
274  }
275}
276
277//////////////////////////////////////////////////////////////////////////
278
279
Note: See TracBrowser for help on using the repository browser.