source: trunk/source/processes/electromagnetic/highenergy/src/G4mplIonisationModel.cc @ 968

Last change on this file since 968 was 961, checked in by garnier, 15 years ago

update processes
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25//
26// $Id: G4mplIonisationModel.cc,v 1.6 2009/02/20 16:38:33 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-02-ref-02 $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class header file
32//
33//
34// File name:     G4mplIonisationModel
35//
36// Author:        Vladimir Ivanchenko
37//
38// Creation date: 06.09.2005
39//
40// Modifications:
41// 12.08.2007 Changing low energy approximation and extrapolation.
42//            Small bug fixing and refactoring (M. Vladymyrov)
43// 13.11.2007 Use low-energy asymptotic from [3] (V.Ivanchenko)
44//
45//
46// -------------------------------------------------------------------
47// References
48// [1] Steven P. Ahlen: Energy loss of relativistic heavy ionizing particles,
49//     S.P. Ahlen, Rev. Mod. Phys 52(1980), p121
50// [2] K.A. Milton arXiv:hep-ex/0602040
51// [3] S.P. Ahlen and K. Kinoshita, Phys. Rev. D26 (1982) 2347
52
53
54//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
55//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
56
57#include "G4mplIonisationModel.hh"
58#include "Randomize.hh"
59#include "G4LossTableManager.hh"
60#include "G4ParticleChangeForLoss.hh"
61
62//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
63
64using namespace std;
65
66G4mplIonisationModel::G4mplIonisationModel(G4double mCharge, const G4String& nam)
67  : G4VEmModel(nam),G4VEmFluctuationModel(nam),
68  magCharge(mCharge),
69  twoln10(log(100.0)),
70  betalow(0.01),
71  betalim(0.1),
72  beta2lim(betalim*betalim),
73  bg2lim(beta2lim*(1.0 + beta2lim))
74{
75  nmpl         = G4int(abs(magCharge) * 2 * fine_structure_const + 0.5);
76  if(nmpl > 6)      nmpl = 6;
77  else if(nmpl < 1) nmpl = 1;
78  pi_hbarc2_over_mc2 = pi * hbarc * hbarc / electron_mass_c2;
79  chargeSquare = magCharge * magCharge;
80  dedxlim = 45.*nmpl*nmpl*GeV*cm2/g;
81}
82
83//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
84
85G4mplIonisationModel::~G4mplIonisationModel()
86{}
87
88//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
89
90void G4mplIonisationModel::Initialise(const G4ParticleDefinition* p,
91                                      const G4DataVector&)
92{
93  monopole = p;
94  mass     = monopole->GetPDGMass();
95
96  if(pParticleChange) 
97    fParticleChange = reinterpret_cast<G4ParticleChangeForLoss*>(pParticleChange);
98  else 
99    fParticleChange = new G4ParticleChangeForLoss();
100}
101
102//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
103
104G4double G4mplIonisationModel::ComputeDEDXPerVolume(const G4Material* material,
105                                                    const G4ParticleDefinition*,
106                                                    G4double kineticEnergy,
107                                                    G4double)
108{
109  G4double tau   = kineticEnergy / mass;
110  G4double gam   = tau + 1.0;
111  G4double bg2   = tau * (tau + 2.0);
112  G4double beta2 = bg2 / (gam * gam);
113  G4double beta  = sqrt(beta2);
114
115  // low-energy asymptotic formula
116  G4double dedx  = dedxlim*beta*material->GetDensity();
117
118  // above asymptotic
119  if(beta > betalow) {
120
121    // high energy
122    if(beta >= betalim) {
123      dedx = ComputeDEDXAhlen(material, bg2);
124
125    } else {
126
127      G4double dedx1 = dedxlim*betalow*material->GetDensity();
128      G4double dedx2 = ComputeDEDXAhlen(material, bg2lim);
129
130      // extrapolation between two formula
131      G4double kapa2 = beta - betalow;
132      G4double kapa1 = betalim - beta;
133      dedx = (kapa1*dedx1 + kapa2*dedx2)/(kapa1 + kapa2);
134    }
135  }
136  return dedx;
137}
138
139//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
140
141G4double G4mplIonisationModel::ComputeDEDXAhlen(const G4Material* material, 
142                                                G4double bg2)
143{
144  G4double eDensity = material->GetElectronDensity();
145  G4double eexc  = material->GetIonisation()->GetMeanExcitationEnergy();
146  G4double cden  = material->GetIonisation()->GetCdensity();
147  G4double mden  = material->GetIonisation()->GetMdensity();
148  G4double aden  = material->GetIonisation()->GetAdensity();
149  G4double x0den = material->GetIonisation()->GetX0density();
150  G4double x1den = material->GetIonisation()->GetX1density();
151
152  // Ahlen's formula for nonconductors, [1]p157, f(5.7)
153  G4double dedx = log(2.0 * electron_mass_c2 * bg2 / eexc) - 0.5;
154
155  // Kazama et al. cross-section correction
156  G4double  k = 0.406;
157  if(nmpl > 1) k = 0.346;
158
159  // Bloch correction
160  const G4double B[7] = { 0.0, 0.248, 0.672, 1.022, 1.243, 1.464, 1.685}; 
161
162  dedx += 0.5 * k - B[nmpl];
163
164  // density effect correction
165  G4double deltam;
166  G4double x = log(bg2) / twoln10;
167  if ( x >= x0den ) {
168    deltam = twoln10 * x - cden;
169    if ( x < x1den ) deltam += aden * pow((x1den-x), mden);
170    dedx -= 0.5 * deltam;
171  }
172
173  // now compute the total ionization loss
174  dedx *=  pi_hbarc2_over_mc2 * eDensity * nmpl * nmpl;
175
176  if (dedx < 0.0) dedx = 0;
177  return dedx;
178}
179
180//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
181
182void G4mplIonisationModel::SampleSecondaries(std::vector<G4DynamicParticle*>*,
183                                             const G4MaterialCutsCouple*,
184                                             const G4DynamicParticle*,
185                                             G4double,
186                                             G4double)
187{}
188
189//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
190
191G4double G4mplIonisationModel::SampleFluctuations(
192                                       const G4Material* material,
193                                       const G4DynamicParticle* dp,
194                                       G4double& tmax,
195                                       G4double& length,
196                                       G4double& meanLoss)
197{
198  G4double siga = Dispersion(material,dp,tmax,length);
199  G4double loss = meanLoss;
200  siga = sqrt(siga);
201  G4double twomeanLoss = meanLoss + meanLoss;
202
203  if(twomeanLoss < siga) {
204    G4double x;
205    do {
206      loss = twomeanLoss*G4UniformRand();
207      x = (loss - meanLoss)/siga;
208    } while (1.0 - 0.5*x*x < G4UniformRand());
209  } else {
210    do {
211      loss = G4RandGauss::shoot(meanLoss,siga);
212    } while (0.0 > loss || loss > twomeanLoss);
213  }
214  return loss;
215}
216
217//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
218
219G4double G4mplIonisationModel::Dispersion(const G4Material* material,
220                                          const G4DynamicParticle* dp,
221                                          G4double& tmax,
222                                          G4double& length)
223{
224  G4double siga = 0.0;
225  G4double tau   = dp->GetKineticEnergy()/mass;
226  if(tau > 0.0) { 
227    G4double electronDensity = material->GetElectronDensity();
228    G4double gam   = tau + 1.0;
229    G4double invbeta2 = (gam*gam)/(tau * (tau+2.0));
230    siga  = (invbeta2 - 0.5) * twopi_mc2_rcl2 * tmax * length
231      * electronDensity * chargeSquare;
232  }
233  return siga;
234}
235
236//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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