source: trunk/source/processes/electromagnetic/highenergy/src/G4mplIonisationModel.cc@ 1036

Last change on this file since 1036 was 1007, checked in by garnier, 17 years ago

update to geant4.9.2
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[819]1//
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25//
[1007]26// $Id: G4mplIonisationModel.cc,v 1.5 2007/11/13 18:36:29 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-02 $
[819]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
[1007]141G4double G4mplIonisationModel::ComputeDEDXAhlen(const G4Material* material, G4double bg2)
[819]142{
143 G4double eDensity = material->GetElectronDensity();
144 G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy();
145 G4double cden = material->GetIonisation()->GetCdensity();
146 G4double mden = material->GetIonisation()->GetMdensity();
147 G4double aden = material->GetIonisation()->GetAdensity();
148 G4double x0den = material->GetIonisation()->GetX0density();
149 G4double x1den = material->GetIonisation()->GetX1density();
150
151 // Ahlen's formula for nonconductors, [1]p157, f(5.7)
152 G4double dedx = log(2.0 * electron_mass_c2 * bg2 / eexc) - 0.5;
153
154 // Kazama et al. cross-section correction
155 G4double k = 0.406;
156 if(nmpl > 1) k = 0.346;
157
158 // Bloch correction
159 const G4double B[7] = { 0.0, 0.248, 0.672, 1.022, 1.243, 1.464, 1.685};
160
161 dedx += 0.5 * k - B[nmpl];
162
163 // density effect correction
164 G4double deltam;
165 G4double x = log(bg2) / twoln10;
166 if ( x >= x0den ) {
167 deltam = twoln10 * x - cden;
168 if ( x < x1den ) deltam += aden * pow((x1den-x), mden);
169 dedx -= 0.5 * deltam;
170 }
171
172 // now compute the total ionization loss
173 dedx *= pi_hbarc2_over_mc2 * eDensity * nmpl * nmpl;
174
175 if (dedx < 0.0) dedx = 0;
176 return dedx;
177}
178
179//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
180
181G4double G4mplIonisationModel::SampleFluctuations(
182 const G4Material* material,
183 const G4DynamicParticle* dp,
184 G4double& tmax,
185 G4double& length,
186 G4double& meanLoss)
187{
188 G4double siga = Dispersion(material,dp,tmax,length);
189 G4double loss = meanLoss;
190 siga = sqrt(siga);
191 G4double twomeanLoss = meanLoss + meanLoss;
192
193 if(twomeanLoss < siga) {
194 G4double x;
195 do {
196 loss = twomeanLoss*G4UniformRand();
197 x = (loss - meanLoss)/siga;
198 } while (1.0 - 0.5*x*x < G4UniformRand());
199 } else {
200 do {
201 loss = G4RandGauss::shoot(meanLoss,siga);
202 } while (0.0 > loss || loss > twomeanLoss);
203 }
204 return loss;
205}
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