source: trunk/source/processes/electromagnetic/highenergy/src/G4mplIonisationWithDeltaModel.cc @ 1350

Last change on this file since 1350 was 1350, checked in by garnier, 13 years ago

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26// $Id: G4mplIonisationWithDeltaModel.cc,v 1.1 2010/10/26 15:40:03 vnivanch Exp $
27// GEANT4 tag $Name: emhighenergy-V09-03-02 $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class header file
32//
33//
34// File name:     G4mplIonisationWithDeltaModel
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 "G4mplIonisationWithDeltaModel.hh"
58#include "Randomize.hh"
59#include "G4LossTableManager.hh"
60#include "G4ParticleChangeForLoss.hh"
61#include "G4Electron.hh"
62#include "G4DynamicParticle.hh"
63
64//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
65
66using namespace std;
67
68G4mplIonisationWithDeltaModel::G4mplIonisationWithDeltaModel(G4double mCharge, const G4String& nam)
69  : G4VEmModel(nam),G4VEmFluctuationModel(nam),
70  magCharge(mCharge),
71  twoln10(log(100.0)),
72  betalow(0.01),
73  betalim(0.1),
74  beta2lim(betalim*betalim),
75  bg2lim(beta2lim*(1.0 + beta2lim))
76{
77  nmpl = G4int(abs(magCharge) * 2 * fine_structure_const + 0.5);
78  if(nmpl > 6)      { nmpl = 6; }
79  else if(nmpl < 1) { nmpl = 1; }
80  pi_hbarc2_over_mc2 = pi * hbarc * hbarc / electron_mass_c2;
81  chargeSquare = magCharge * magCharge;
82  dedxlim = 45.*nmpl*nmpl*GeV*cm2/g;
83  fParticleChange = 0;
84  theElectron = G4Electron::Electron();
85  G4cout << "### Monopole ionisation model with d-electron production, Gmag= " 
86         << magCharge/eplus << G4endl;
87  mass = 0.0;
88}
89
90//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
91
92G4mplIonisationWithDeltaModel::~G4mplIonisationWithDeltaModel()
93{}
94
95//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
96
97void 
98G4mplIonisationWithDeltaModel::Initialise(const G4ParticleDefinition* p,
99                                          const G4DataVector&)
100{
101  monopole = p;
102  mass     = monopole->GetPDGMass();
103  if(!fParticleChange) { fParticleChange = GetParticleChangeForLoss(); }
104}
105
106//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
107
108G4double
109G4mplIonisationWithDeltaModel::ComputeDEDXPerVolume(const G4Material* material,
110                                                    const G4ParticleDefinition* p,
111                                                    G4double kineticEnergy,
112                                                    G4double maxEnergy)
113{
114  G4double tmax = MaxSecondaryEnergy(p,kineticEnergy);
115  G4double cutEnergy = std::min(tmax, maxEnergy);
116  G4double tau   = kineticEnergy / mass;
117  G4double gam   = tau + 1.0;
118  G4double bg2   = tau * (tau + 2.0);
119  G4double beta2 = bg2 / (gam * gam);
120  G4double beta  = sqrt(beta2);
121
122  // low-energy asymptotic formula
123  G4double dedx  = dedxlim*beta*material->GetDensity();
124
125  // above asymptotic
126  if(beta > betalow) {
127
128    // high energy
129    if(beta >= betalim) {
130      dedx = ComputeDEDXAhlen(material, bg2, cutEnergy);
131
132    } else {
133
134      G4double dedx1 = dedxlim*betalow*material->GetDensity();
135      G4double dedx2 = ComputeDEDXAhlen(material, bg2lim, cutEnergy);
136
137      // extrapolation between two formula
138      G4double kapa2 = beta - betalow;
139      G4double kapa1 = betalim - beta;
140      dedx = (kapa1*dedx1 + kapa2*dedx2)/(kapa1 + kapa2);
141    }
142  }
143  return dedx;
144}
145
146//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
147
148G4double
149G4mplIonisationWithDeltaModel::ComputeDEDXAhlen(const G4Material* material, 
150                                                G4double bg2, 
151                                                G4double cutEnergy)
152{
153  G4double eDensity = material->GetElectronDensity();
154  G4double eexc  = material->GetIonisation()->GetMeanExcitationEnergy();
155
156  // Ahlen's formula for nonconductors, [1]p157, f(5.7)
157  G4double dedx = 
158    0.5*(log(2.0 * electron_mass_c2 * bg2*cutEnergy / (eexc*eexc)) - 1.0);
159
160  // Kazama et al. cross-section correction
161  G4double  k = 0.406;
162  if(nmpl > 1) { k = 0.346; }
163
164  // Bloch correction
165  const G4double B[7] = { 0.0, 0.248, 0.672, 1.022, 1.243, 1.464, 1.685}; 
166
167  dedx += 0.5 * k - B[nmpl];
168
169  // density effect correction
170  G4double x = log(bg2)/twoln10;
171  dedx -= material->GetIonisation()->DensityCorrection(x);
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
182G4double
183G4mplIonisationWithDeltaModel::ComputeCrossSectionPerElectron(
184                                           const G4ParticleDefinition* p,
185                                           G4double kineticEnergy,
186                                           G4double cutEnergy,
187                                           G4double maxKinEnergy)
188{
189  G4double cross = 0.0;
190  G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
191  G4double maxEnergy = min(tmax,maxKinEnergy);
192  if(cutEnergy < maxEnergy) {
193    cross = (1.0/cutEnergy - 1.0/maxEnergy)*twopi_mc2_rcl2*chargeSquare;
194  }
195  return cross;
196}
197
198//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
199
200G4double
201G4mplIonisationWithDeltaModel::ComputeCrossSectionPerAtom(
202                                          const G4ParticleDefinition* p,
203                                          G4double kineticEnergy,
204                                          G4double Z, G4double,
205                                          G4double cutEnergy,
206                                          G4double maxEnergy)
207{
208  G4double cross = 
209    Z*ComputeCrossSectionPerElectron(p,kineticEnergy,cutEnergy,maxEnergy);
210  return cross;
211}
212
213//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
214
215void 
216G4mplIonisationWithDeltaModel::SampleSecondaries(vector<G4DynamicParticle*>* vdp,
217                                                 const G4MaterialCutsCouple*,
218                                                 const G4DynamicParticle* dp,
219                                                 G4double minKinEnergy,
220                                                 G4double maxEnergy)
221{
222  G4double kineticEnergy = dp->GetKineticEnergy();
223  G4double tmax = MaxSecondaryEnergy(dp->GetDefinition(),kineticEnergy);
224
225  G4double maxKinEnergy = std::min(maxEnergy,tmax);
226  if(minKinEnergy >= maxKinEnergy) { return; }
227
228  //G4cout << "G4mplIonisationWithDeltaModel::SampleSecondaries: E(GeV)= "
229  //     << kineticEnergy/GeV << " M(GeV)= " << mass/GeV
230  //     << " tmin(MeV)= " << minKinEnergy/MeV << G4endl;
231
232  G4double totEnergy     = kineticEnergy + mass;
233  G4double etot2         = totEnergy*totEnergy;
234  G4double beta2         = kineticEnergy*(kineticEnergy + 2.0*mass)/etot2;
235 
236  // sampling without nuclear size effect
237  G4double q = G4UniformRand();
238  G4double deltaKinEnergy = minKinEnergy*maxKinEnergy
239    /(minKinEnergy*(1.0 - q) + maxKinEnergy*q);
240
241  // delta-electron is produced
242  G4double totMomentum = totEnergy*sqrt(beta2);
243  G4double deltaMomentum =
244           sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
245  G4double cost = deltaKinEnergy * (totEnergy + electron_mass_c2) /
246                                   (deltaMomentum * totMomentum);
247  if(cost > 1.0) { cost = 1.0; }
248
249  G4double sint = sqrt((1.0 - cost)*(1.0 + cost));
250
251  G4double phi = twopi * G4UniformRand() ;
252
253  G4ThreeVector deltaDirection(sint*cos(phi),sint*sin(phi), cost);
254  G4ThreeVector direction = dp->GetMomentumDirection();
255  deltaDirection.rotateUz(direction);
256
257  // create G4DynamicParticle object for delta ray
258  G4DynamicParticle* delta = 
259    new G4DynamicParticle(theElectron,deltaDirection,deltaKinEnergy);
260
261  vdp->push_back(delta);
262
263  // Change kinematics of primary particle
264  kineticEnergy       -= deltaKinEnergy;
265  G4ThreeVector finalP = direction*totMomentum - deltaDirection*deltaMomentum;
266  finalP               = finalP.unit();
267
268  fParticleChange->SetProposedKineticEnergy(kineticEnergy);
269  fParticleChange->SetProposedMomentumDirection(finalP);
270}
271
272//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
273
274G4double G4mplIonisationWithDeltaModel::SampleFluctuations(
275                                       const G4Material* material,
276                                       const G4DynamicParticle* dp,
277                                       G4double& tmax,
278                                       G4double& length,
279                                       G4double& meanLoss)
280{
281  G4double siga = Dispersion(material,dp,tmax,length);
282  G4double loss = meanLoss;
283  siga = sqrt(siga);
284  G4double twomeanLoss = meanLoss + meanLoss;
285
286  if(twomeanLoss < siga) {
287    G4double x;
288    do {
289      loss = twomeanLoss*G4UniformRand();
290      x = (loss - meanLoss)/siga;
291    } while (1.0 - 0.5*x*x < G4UniformRand());
292  } else {
293    do {
294      loss = G4RandGauss::shoot(meanLoss,siga);
295    } while (0.0 > loss || loss > twomeanLoss);
296  }
297  return loss;
298}
299
300//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
301
302G4double
303G4mplIonisationWithDeltaModel::Dispersion(const G4Material* material,
304                                          const G4DynamicParticle* dp,
305                                          G4double& tmax,
306                                          G4double& length)
307{
308  G4double siga = 0.0;
309  G4double tau   = dp->GetKineticEnergy()/mass;
310  if(tau > 0.0) { 
311    G4double electronDensity = material->GetElectronDensity();
312    G4double gam   = tau + 1.0;
313    G4double invbeta2 = (gam*gam)/(tau * (tau+2.0));
314    siga  = (invbeta2 - 0.5) * twopi_mc2_rcl2 * tmax * length
315      * electronDensity * chargeSquare;
316  }
317  return siga;
318}
319
320//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
321
322G4double
323G4mplIonisationWithDeltaModel::MaxSecondaryEnergy(const G4ParticleDefinition*,
324                                                  G4double kinEnergy)
325{
326  G4double tau = kinEnergy/mass;
327  return 2.0*electron_mass_c2*tau*(tau + 2.);
328}
329
330//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
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