source: trunk/source/processes/electromagnetic/standard/src/G4BetheBlochModel.cc@ 900

Last change on this file since 900 was 819, checked in by garnier, 17 years ago

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25//
26// $Id: G4BetheBlochModel.cc,v 1.13 2007/05/22 17:34:36 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-01-patch-02 $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class header file
32//
33//
34// File name: G4BetheBlochModel
35//
36// Author: Vladimir Ivanchenko on base of Laszlo Urban code
37//
38// Creation date: 03.01.2002
39//
40// Modifications:
41//
42// 04-12-02 Fix problem of G4DynamicParticle constructor (V.Ivanchenko)
43// 23-12-02 Change interface in order to move to cut per region (V.Ivanchenko)
44// 27-01-03 Make models region aware (V.Ivanchenko)
45// 13-02-03 Add name (V.Ivanchenko)
46// 24-03-05 Add G4EmCorrections (V.Ivanchenko)
47// 11-04-05 Major optimisation of internal interfaces (V.Ivantchenko)
48// 11-02-06 ComputeCrossSectionPerElectron, ComputeCrossSectionPerAtom (mma)
49// 12-02-06 move G4LossTableManager::Instance()->EmCorrections()
50// in constructor (mma)
51//
52// -------------------------------------------------------------------
53//
54
55
56//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
57//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
58
59#include "G4BetheBlochModel.hh"
60#include "Randomize.hh"
61#include "G4Electron.hh"
62#include "G4LossTableManager.hh"
63#include "G4EmCorrections.hh"
64#include "G4ParticleChangeForLoss.hh"
65
66//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
67
68using namespace std;
69
70G4BetheBlochModel::G4BetheBlochModel(const G4ParticleDefinition* p,
71 const G4String& nam)
72 : G4VEmModel(nam),
73 particle(0),
74 tlimit(DBL_MAX),
75 twoln10(2.0*log(10.0)),
76 bg2lim(0.0169),
77 taulim(8.4146e-3),
78 isIon(false)
79{
80 if(p) SetParticle(p);
81 theElectron = G4Electron::Electron();
82 corr = G4LossTableManager::Instance()->EmCorrections();
83}
84
85//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
86
87G4BetheBlochModel::~G4BetheBlochModel()
88{}
89
90//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
91
92G4double G4BetheBlochModel::MinEnergyCut(const G4ParticleDefinition*,
93 const G4MaterialCutsCouple* couple)
94{
95 return couple->GetMaterial()->GetIonisation()->GetMeanExcitationEnergy();
96}
97
98//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
99
100void G4BetheBlochModel::Initialise(const G4ParticleDefinition* p,
101 const G4DataVector&)
102{
103 if (!particle) SetParticle(p);
104 G4String pname = particle->GetParticleName();
105 if (particle->GetParticleType() == "nucleus" &&
106 pname != "deuteron" && pname != "triton") isIon = true;
107
108 if (pParticleChange)
109 fParticleChange = reinterpret_cast<G4ParticleChangeForLoss*>
110 (pParticleChange);
111 else
112 fParticleChange = new G4ParticleChangeForLoss();
113}
114
115//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
116
117G4double G4BetheBlochModel::ComputeCrossSectionPerElectron(
118 const G4ParticleDefinition* p,
119 G4double kineticEnergy,
120 G4double cutEnergy,
121 G4double maxKinEnergy)
122{
123 G4double cross = 0.0;
124 G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
125 G4double maxEnergy = min(tmax,maxKinEnergy);
126 if(cutEnergy < maxEnergy) {
127
128 G4double totEnergy = kineticEnergy + mass;
129 G4double energy2 = totEnergy*totEnergy;
130 G4double beta2 = kineticEnergy*(kineticEnergy + 2.0*mass)/energy2;
131
132 cross = 1.0/cutEnergy - 1.0/maxEnergy - beta2*log(maxEnergy/cutEnergy)/tmax;
133
134 // +term for spin=1/2 particle
135 if( 0.5 == spin ) cross += 0.5*(maxEnergy - cutEnergy)/energy2;
136
137 cross *= twopi_mc2_rcl2*chargeSquare/beta2;
138 }
139
140 // G4cout << "BB: e= " << kineticEnergy << " tmin= " << cutEnergy
141 // << " tmax= " << tmax << " cross= " << cross << G4endl;
142
143 return cross;
144}
145
146//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
147
148G4double G4BetheBlochModel::ComputeCrossSectionPerAtom(
149 const G4ParticleDefinition* p,
150 G4double kineticEnergy,
151 G4double Z, G4double,
152 G4double cutEnergy,
153 G4double maxEnergy)
154{
155 G4double cross = Z*ComputeCrossSectionPerElectron
156 (p,kineticEnergy,cutEnergy,maxEnergy);
157 return cross;
158}
159
160//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
161
162G4double G4BetheBlochModel::CrossSectionPerVolume(
163 const G4Material* material,
164 const G4ParticleDefinition* p,
165 G4double kineticEnergy,
166 G4double cutEnergy,
167 G4double maxEnergy)
168{
169 G4double eDensity = material->GetElectronDensity();
170 G4double cross = eDensity*ComputeCrossSectionPerElectron
171 (p,kineticEnergy,cutEnergy,maxEnergy);
172 return cross;
173}
174
175//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
176
177G4double G4BetheBlochModel::ComputeDEDXPerVolume(const G4Material* material,
178 const G4ParticleDefinition* p,
179 G4double kineticEnergy,
180 G4double cut)
181{
182 G4double tmax = MaxSecondaryEnergy(p, kineticEnergy);
183 G4double cutEnergy = min(cut,tmax);
184
185 G4double tau = kineticEnergy/mass;
186 G4double gam = tau + 1.0;
187 G4double bg2 = tau * (tau+2.0);
188 G4double beta2 = bg2/(gam*gam);
189
190 G4double eexc = material->GetIonisation()->GetMeanExcitationEnergy();
191 G4double eexc2 = eexc*eexc;
192 G4double cden = material->GetIonisation()->GetCdensity();
193 G4double mden = material->GetIonisation()->GetMdensity();
194 G4double aden = material->GetIonisation()->GetAdensity();
195 G4double x0den = material->GetIonisation()->GetX0density();
196 G4double x1den = material->GetIonisation()->GetX1density();
197
198 G4double eDensity = material->GetElectronDensity();
199
200 G4double dedx = log(2.0*electron_mass_c2*bg2*cutEnergy/eexc2)
201 - (1.0 + cutEnergy/tmax)*beta2;
202
203 if(0.5 == spin) {
204 G4double del = 0.5*cutEnergy/(kineticEnergy + mass);
205 dedx += del*del;
206 }
207
208 // density correction
209 G4double x = log(bg2)/twoln10;
210 if ( x >= x0den ) {
211 dedx -= twoln10*x - cden ;
212 if ( x < x1den ) dedx -= aden*pow((x1den-x),mden) ;
213 }
214
215 // shell correction
216 dedx -= 2.0*corr->ShellCorrection(p,material,kineticEnergy);
217
218 // now compute the total ionization loss
219
220 if (dedx < 0.0) dedx = 0.0 ;
221
222 dedx *= twopi_mc2_rcl2*chargeSquare*eDensity/beta2;
223
224 //High order correction only for hadrons
225 if(!isIon) dedx += corr->HighOrderCorrections(p,material,kineticEnergy);
226
227 return dedx;
228}
229
230//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
231
232void G4BetheBlochModel::SampleSecondaries(vector<G4DynamicParticle*>* vdp,
233 const G4MaterialCutsCouple*,
234 const G4DynamicParticle* dp,
235 G4double minKinEnergy,
236 G4double maxEnergy)
237{
238 G4double kineticEnergy = dp->GetKineticEnergy();
239 G4double tmax = MaxSecondaryEnergy(dp->GetDefinition(),kineticEnergy);
240
241 G4double maxKinEnergy = min(maxEnergy,tmax);
242 if(minKinEnergy >= maxKinEnergy) return;
243
244 G4double totEnergy = kineticEnergy + mass;
245 G4double etot2 = totEnergy*totEnergy;
246 G4double beta2 = kineticEnergy*(kineticEnergy + 2.0*mass)/etot2;
247
248 G4double deltaKinEnergy, f;
249
250 // sampling follows ...
251 do {
252 G4double q = G4UniformRand();
253 deltaKinEnergy = minKinEnergy*maxKinEnergy
254 /(minKinEnergy*(1.0 - q) + maxKinEnergy*q);
255
256 f = 1.0 - beta2*deltaKinEnergy/tmax;
257 if( 0.5 == spin ) f += 0.5*deltaKinEnergy*deltaKinEnergy/etot2;
258
259 if(f > 1.0) {
260 G4cout << "G4BetheBlochModel::SampleSecondary Warning! "
261 << "Majorant 1.0 < "
262 << f << " for Edelta= " << deltaKinEnergy
263 << G4endl;
264 }
265
266 } while( G4UniformRand() > f );
267
268 G4double totMomentum = totEnergy*sqrt(beta2);
269 G4double deltaMomentum =
270 sqrt(deltaKinEnergy * (deltaKinEnergy + 2.0*electron_mass_c2));
271 G4double cost = deltaKinEnergy * (totEnergy + electron_mass_c2) /
272 (deltaMomentum * totMomentum);
273 if(cost > 1.0) {
274 G4cout << "### G4BetheBlochModel WARNING: cost= "
275 << cost << " > 1 for "
276 << dp->GetDefinition()->GetParticleName()
277 << " Ekin(MeV)= " << kineticEnergy
278 << " p(MeV/c)= " << totMomentum
279 << " delEkin(MeV)= " << deltaKinEnergy
280 << " delMom(MeV/c)= " << deltaMomentum
281 << " tmin(MeV)= " << minKinEnergy
282 << " tmax(MeV)= " << maxKinEnergy
283 << " dir= " << dp->GetMomentumDirection()
284 << G4endl;
285 cost = 1.0;
286 }
287 G4double sint = sqrt((1.0 - cost)*(1.0 + cost));
288
289 G4double phi = twopi * G4UniformRand() ;
290
291
292 G4ThreeVector deltaDirection(sint*cos(phi),sint*sin(phi), cost);
293 G4ThreeVector direction = dp->GetMomentumDirection();
294 deltaDirection.rotateUz(direction);
295
296 // create G4DynamicParticle object for delta ray
297 G4DynamicParticle* delta = new G4DynamicParticle(theElectron,
298 deltaDirection,deltaKinEnergy);
299
300 vdp->push_back(delta);
301
302 // Change kinematics of primary particle
303 kineticEnergy -= deltaKinEnergy;
304 G4ThreeVector finalP = direction*totMomentum - deltaDirection*deltaMomentum;
305 finalP = finalP.unit();
306
307 fParticleChange->SetProposedKineticEnergy(kineticEnergy);
308 fParticleChange->SetProposedMomentumDirection(finalP);
309}
310
311//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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