source: trunk/source/processes/electromagnetic/highenergy/src/G4mplIonisationModel.cc @ 1231

Last change on this file since 1231 was 1228, checked in by garnier, 15 years ago

update geant4.9.3 tag
File size: 7.8 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: G4mplIonisationModel.cc,v 1.7 2009/04/12 17:35:41 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-03 $
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  fParticleChange = 0;
82}
83
84//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
85
86G4mplIonisationModel::~G4mplIonisationModel()
87{}
88
89//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
90
91void G4mplIonisationModel::Initialise(const G4ParticleDefinition* p,
92                                      const G4DataVector&)
93{
94  monopole = p;
95  mass     = monopole->GetPDGMass();
96  if(!fParticleChange) fParticleChange = GetParticleChangeForLoss();
97}
98
99//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
100
101G4double G4mplIonisationModel::ComputeDEDXPerVolume(const G4Material* material,
102                                                    const G4ParticleDefinition*,
103                                                    G4double kineticEnergy,
104                                                    G4double)
105{
106  G4double tau   = kineticEnergy / mass;
107  G4double gam   = tau + 1.0;
108  G4double bg2   = tau * (tau + 2.0);
109  G4double beta2 = bg2 / (gam * gam);
110  G4double beta  = sqrt(beta2);
111
112  // low-energy asymptotic formula
113  G4double dedx  = dedxlim*beta*material->GetDensity();
114
115  // above asymptotic
116  if(beta > betalow) {
117
118    // high energy
119    if(beta >= betalim) {
120      dedx = ComputeDEDXAhlen(material, bg2);
121
122    } else {
123
124      G4double dedx1 = dedxlim*betalow*material->GetDensity();
125      G4double dedx2 = ComputeDEDXAhlen(material, bg2lim);
126
127      // extrapolation between two formula
128      G4double kapa2 = beta - betalow;
129      G4double kapa1 = betalim - beta;
130      dedx = (kapa1*dedx1 + kapa2*dedx2)/(kapa1 + kapa2);
131    }
132  }
133  return dedx;
134}
135
136//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
137
138G4double G4mplIonisationModel::ComputeDEDXAhlen(const G4Material* material, 
139                                                G4double bg2)
140{
141  G4double eDensity = material->GetElectronDensity();
142  G4double eexc  = material->GetIonisation()->GetMeanExcitationEnergy();
143  G4double cden  = material->GetIonisation()->GetCdensity();
144  G4double mden  = material->GetIonisation()->GetMdensity();
145  G4double aden  = material->GetIonisation()->GetAdensity();
146  G4double x0den = material->GetIonisation()->GetX0density();
147  G4double x1den = material->GetIonisation()->GetX1density();
148
149  // Ahlen's formula for nonconductors, [1]p157, f(5.7)
150  G4double dedx = log(2.0 * electron_mass_c2 * bg2 / eexc) - 0.5;
151
152  // Kazama et al. cross-section correction
153  G4double  k = 0.406;
154  if(nmpl > 1) k = 0.346;
155
156  // Bloch correction
157  const G4double B[7] = { 0.0, 0.248, 0.672, 1.022, 1.243, 1.464, 1.685}; 
158
159  dedx += 0.5 * k - B[nmpl];
160
161  // density effect correction
162  G4double deltam;
163  G4double x = log(bg2) / twoln10;
164  if ( x >= x0den ) {
165    deltam = twoln10 * x - cden;
166    if ( x < x1den ) deltam += aden * pow((x1den-x), mden);
167    dedx -= 0.5 * deltam;
168  }
169
170  // now compute the total ionization loss
171  dedx *=  pi_hbarc2_over_mc2 * eDensity * nmpl * nmpl;
172
173  if (dedx < 0.0) dedx = 0;
174  return dedx;
175}
176
177//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
178
179void G4mplIonisationModel::SampleSecondaries(std::vector<G4DynamicParticle*>*,
180                                             const G4MaterialCutsCouple*,
181                                             const G4DynamicParticle*,
182                                             G4double,
183                                             G4double)
184{}
185
186//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
187
188G4double G4mplIonisationModel::SampleFluctuations(
189                                       const G4Material* material,
190                                       const G4DynamicParticle* dp,
191                                       G4double& tmax,
192                                       G4double& length,
193                                       G4double& meanLoss)
194{
195  G4double siga = Dispersion(material,dp,tmax,length);
196  G4double loss = meanLoss;
197  siga = sqrt(siga);
198  G4double twomeanLoss = meanLoss + meanLoss;
199
200  if(twomeanLoss < siga) {
201    G4double x;
202    do {
203      loss = twomeanLoss*G4UniformRand();
204      x = (loss - meanLoss)/siga;
205    } while (1.0 - 0.5*x*x < G4UniformRand());
206  } else {
207    do {
208      loss = G4RandGauss::shoot(meanLoss,siga);
209    } while (0.0 > loss || loss > twomeanLoss);
210  }
211  return loss;
212}
213
214//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
215
216G4double G4mplIonisationModel::Dispersion(const G4Material* material,
217                                          const G4DynamicParticle* dp,
218                                          G4double& tmax,
219                                          G4double& length)
220{
221  G4double siga = 0.0;
222  G4double tau   = dp->GetKineticEnergy()/mass;
223  if(tau > 0.0) { 
224    G4double electronDensity = material->GetElectronDensity();
225    G4double gam   = tau + 1.0;
226    G4double invbeta2 = (gam*gam)/(tau * (tau+2.0));
227    siga  = (invbeta2 - 0.5) * twopi_mc2_rcl2 * tmax * length
228      * electronDensity * chargeSquare;
229  }
230  return siga;
231}
232
233//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
Note: See TracBrowser for help on using the repository browser.