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28 //
29 // GEANT4 Class file
30 //
31 //
32 // File name: G4IonFluctuation
33 //
34 // Author: Vladimir Ivanchenko
35 //
36 // Creation date: 03.01.2002
37 //
38 // Modifications:
39 //
40 // 28-12-02 add method Dispersion (V.Ivanchenko)
41 // 07-02-03 change signature (V.Ivanchenko)
42 // 13-02-03 Add name (V.Ivanchenko)
43 // 23-05-03 Add control on parthalogical cases (V.Ivanchenko)
44 // 16-10-03 Changed interface to Initialisation (V.Ivanchenko)
45 // 27-09-07 Use FermiEnergy from material, add cut dependence (V.Ivanchenko)
46 // 01-02-08 Add protection for small energies and optimise the code (V.Ivanchenko)
47 // 01-06-08 Added initialisation of effective charge prestep (V.Ivanchenko)
48 //
49 // Class Description:
50 //
51 // -------------------------------------------------------------------
52 //
53
54 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
55 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
56
57 #include "G4IonFluctuations.hh"
58 #include "G4UniversalFluctuation.hh"
59 #include "G4PhysicalConstants.hh"
60 #include "G4SystemOfUnits.hh"
61 #include "Randomize.hh"
62 #include "G4Poisson.hh"
63 #include "G4MaterialCutsCouple.hh"
64 #include "G4Material.hh"
65 #include "G4DynamicParticle.hh"
66 #include "G4Pow.hh"
67 #include "G4Log.hh"
68
69 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
70
71 using namespace std;
72
73 G4IonFluctuations::G4IonFluctuations(const G4String& nam)
74 : G4VEmFluctuationModel(nam),
75 particleMass(CLHEP::proton_mass_c2),
76 parameter(10.0*CLHEP::MeV/CLHEP::proton_mass_c2),
77 theBohrBeta2(50.0*keV/CLHEP::proton_mass_c2),
78 minLoss(0.001*CLHEP::eV)
79 {
80 uniFluct = new G4UniversalFluctuation();
81 g4calc = G4Pow::GetInstance();
82 }
83
84 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
85
86 G4IonFluctuations::~G4IonFluctuations() = default;
87
88 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
89
90 void G4IonFluctuations::InitialiseMe(const G4ParticleDefinition* part)
91 {
92 particle = part;
93 particleMass = part->GetPDGMass();
94 charge = part->GetPDGCharge()/eplus;
95 effChargeSquare = chargeSquare = charge*charge;
96 uniFluct->InitialiseMe(part);
97 }
98
99 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
100
101 G4double
102 G4IonFluctuations::SampleFluctuations(const G4MaterialCutsCouple* couple,
103 const G4DynamicParticle* dp,
104 const G4double tcut,
105 const G4double tmax,
106 const G4double length,
107 const G4double meanLoss)
108 {
109 // G4cout << "### meanLoss= " << meanLoss << G4endl;
110 if(meanLoss <= minLoss) return meanLoss;
111
112 //G4cout << "G4IonFluctuations::SampleFluctuations E(MeV)= "
113 // << dp->GetKineticEnergy()
114 // << " Elim(MeV)= " << parameter*charge*particleMass << G4endl;
115
116 // Vavilov fluctuations above energy threshold
117 if(dp->GetKineticEnergy() > parameter*charge*particleMass) {
118 return uniFluct->SampleFluctuations(couple,dp,tcut,tmax,length,meanLoss);
119 }
120
121 const G4Material* material = couple->GetMaterial();
122 G4double siga = Dispersion(material,dp,tcut,tmax,length);
123 G4double loss = meanLoss;
124
125 //G4cout << "### siga= " << sqrt(siga) << " navr= " << navr << G4endl;
126
127 // Gaussian fluctuation
128
129 // Increase fluctuations for big fractional energy loss
130 //G4cout << "siga= " << siga << G4endl;
131 if ( meanLoss > minFraction*kineticEnergy ) {
132 G4double gam = (kineticEnergy - meanLoss)/particleMass + 1.0;
133 G4double b2 = 1.0 - 1.0/(gam*gam);
134 if(b2 < xmin*beta2) b2 = xmin*beta2;
135 G4double x = b2/beta2;
136 G4double x3 = 1.0/(x*x*x);
137 siga *= 0.25*(1.0 + x)*(x3 + (1.0/b2 - 0.5)/(1.0/beta2 - 0.5) );
138 }
139 siga = std::sqrt(siga);
140 G4double sn = meanLoss/siga;
141 G4double twomeanLoss = meanLoss + meanLoss;
142 // G4cout << "siga= " << siga << " sn= " << sn << G4endl;
143
144 CLHEP::HepRandomEngine* rndmEngine = G4Random::getTheEngine();
145 // thick target case
146 if (sn >= 2.0) {
147
148 do {
149 loss = G4RandGauss::shoot(rndmEngine,meanLoss,siga);
150 // Loop checking, 03-Aug-2015, Vladimir Ivanchenko
151 } while (0.0 > loss || twomeanLoss < loss);
152
153 // Gamma distribution
154 } else if(sn > 0.1) {
155
156 G4double neff = sn*sn;
157 loss = meanLoss*G4RandGamma::shoot(rndmEngine,neff,1.0)/neff;
158
159 // uniform distribution for very small steps
160 } else {
161 loss = twomeanLoss*rndmEngine->flat();
162 }
163
164 //G4cout << "meanLoss= " << meanLoss << " loss= " << loss << G4endl;
165 return loss;
166 }
167
168 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
169
170 G4double G4IonFluctuations::Dispersion(const G4Material* material,
171 const G4DynamicParticle* dp,
172 const G4double tcut,
173 const G4double tmax,
174 const G4double length)
175 {
176 if(dp->GetDefinition() != particle) { InitialiseMe(dp->GetDefinition()); }
177
178 const G4double beta = dp->GetBeta();
179 kineticEnergy = dp->GetKineticEnergy();
180 beta2 = beta*beta;
181
182 G4double siga = (tmax/beta2 - 0.5*tcut)*CLHEP::twopi_mc2_rcl2*length*
183 material->GetElectronDensity()*effChargeSquare;
184
185 // Low velocity - additional ion charge fluctuations according to
186 // Q.Yang et al., NIM B61(1991)149-155.
187 //G4cout << "sigE= " << sqrt(siga) << " charge= " << charge <<G4endl;
188
189 G4double Z = material->GetIonisation()->GetZeffective();
190 G4double fac = Factor(material, Z);
191
192 // heavy ion correction
193 // G4double f1 = 1.065e-4*chargeSquare;
194 // if(beta2 > theBohrBeta2) f1/= beta2;
195 // else f1/= theBohrBeta2;
196 // if(f1 > 2.5) f1 = 2.5;
197 // fac *= (1.0 + f1);
198
199 // taking into account the cutg
200 G4double fac_cut = 1.0 + (fac - 1.0)*2.0*CLHEP::electron_mass_c2*beta2
201 /(tmax*(1.0 - beta2));
202 if(fac_cut > 0.01 && fac > 0.01) {
203 siga *= fac_cut;
204 }
205 /*
206 G4cout << "siga(keV)= " << sqrt(siga)/keV << " fac= " << fac
207 << " f1= " << fac_cut << G4endl;
208 */
209 return siga;
210 }
211
212 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
213
214 G4double G4IonFluctuations::Factor(const G4Material* material, G4double Z)
215 {
216 // The aproximation of energy loss fluctuations
217 // Q.Yang et al., NIM B61(1991)149-155.
218
219 // Reduced energy in MeV/AMU
220 G4double energy = kineticEnergy*CLHEP::amu_c2/(particleMass*CLHEP::MeV);
221
222 // simple approximation for higher beta2
223 G4double s1 = RelativisticFactor(material, Z);
224
225 // tabulation for lower beta2
226 if( beta2 < 3.0*theBohrBeta2*Z ) {
227
228 static const G4double a[96][4] = {
229 {-0.3291, -0.8312, 0.2460, -1.0220},
230 {-0.5615, -0.5898, 0.5205, -0.7258},
231 {-0.5280, -0.4981, 0.5519, -0.5865},
232 {-0.5125, -0.4625, 0.5660, -0.5190},
233 {-0.5127, -0.8595, 0.5626, -0.8721},
234 {-0.5174, -1.1930, 0.5565, -1.1980},
235 {-0.5179, -1.1850, 0.5560, -1.2070},
236 {-0.5209, -0.9355, 0.5590, -1.0250},
237 {-0.5255, -0.7766, 0.5720, -0.9412},
238
239 {-0.5776, -0.6665, 0.6598, -0.8484},
240 {-0.6013, -0.6045, 0.7321, -0.7671},
241 {-0.5781, -0.5518, 0.7605, -0.6919},
242 {-0.5587, -0.4981, 0.7835, -0.6195},
243 {-0.5466, -0.4656, 0.7978, -0.5771},
244 {-0.5406, -0.4690, 0.8031, -0.5718},
245 {-0.5391, -0.5061, 0.8024, -0.5974},
246 {-0.5380, -0.6483, 0.7962, -0.6970},
247 {-0.5355, -0.7722, 0.7962, -0.7839},
248 {-0.5329, -0.7720, 0.7988, -0.7846},
249
250 {-0.5335, -0.7671, 0.7984, -0.7933},
251 {-0.5324, -0.7612, 0.7998, -0.8031},
252 {-0.5305, -0.7300, 0.8031, -0.7990},
253 {-0.5307, -0.7178, 0.8049, -0.8216},
254 {-0.5248, -0.6621, 0.8165, -0.7919},
255 {-0.5180, -0.6502, 0.8266, -0.7986},
256 {-0.5084, -0.6408, 0.8396, -0.8048},
257 {-0.4967, -0.6331, 0.8549, -0.8093},
258 {-0.4861, -0.6508, 0.8712, -0.8432},
259 {-0.4700, -0.6186, 0.8961, -0.8132},
260
261 {-0.4545, -0.5720, 0.9227, -0.7710},
262 {-0.4404, -0.5226, 0.9481, -0.7254},
263 {-0.4288, -0.4778, 0.9701, -0.6850},
264 {-0.4199, -0.4425, 0.9874, -0.6539},
265 {-0.4131, -0.4188, 0.9998, -0.6332},
266 {-0.4089, -0.4057, 1.0070, -0.6218},
267 {-0.4039, -0.3913, 1.0150, -0.6107},
268 {-0.3987, -0.3698, 1.0240, -0.5938},
269 {-0.3977, -0.3608, 1.0260, -0.5852},
270 {-0.3972, -0.3600, 1.0260, -0.5842},
271
272 {-0.3985, -0.3803, 1.0200, -0.6013},
273 {-0.3985, -0.3979, 1.0150, -0.6168},
274 {-0.3968, -0.3990, 1.0160, -0.6195},
275 {-0.3971, -0.4432, 1.0050, -0.6591},
276 {-0.3944, -0.4665, 1.0010, -0.6825},
277 {-0.3924, -0.5109, 0.9921, -0.7235},
278 {-0.3882, -0.5158, 0.9947, -0.7343},
279 {-0.3838, -0.5125, 0.9999, -0.7370},
280 {-0.3786, -0.4976, 1.0090, -0.7310},
281 {-0.3741, -0.4738, 1.0200, -0.7155},
282
283 {-0.3969, -0.4496, 1.0320, -0.6982},
284 {-0.3663, -0.4297, 1.0430, -0.6828},
285 {-0.3630, -0.4120, 1.0530, -0.6689},
286 {-0.3597, -0.3964, 1.0620, -0.6564},
287 {-0.3555, -0.3809, 1.0720, -0.6454},
288 {-0.3525, -0.3607, 1.0820, -0.6289},
289 {-0.3505, -0.3465, 1.0900, -0.6171},
290 {-0.3397, -0.3570, 1.1020, -0.6384},
291 {-0.3314, -0.3552, 1.1130, -0.6441},
292 {-0.3235, -0.3531, 1.1230, -0.6498},
293
294 {-0.3150, -0.3483, 1.1360, -0.6539},
295 {-0.3060, -0.3441, 1.1490, -0.6593},
296 {-0.2968, -0.3396, 1.1630, -0.6649},
297 {-0.2935, -0.3225, 1.1760, -0.6527},
298 {-0.2797, -0.3262, 1.1940, -0.6722},
299 {-0.2704, -0.3202, 1.2100, -0.6770},
300 {-0.2815, -0.3227, 1.2480, -0.6775},
301 {-0.2880, -0.3245, 1.2810, -0.6801},
302 {-0.3034, -0.3263, 1.3270, -0.6778},
303 {-0.2936, -0.3215, 1.3430, -0.6835},
304
305 {-0.3282, -0.3200, 1.3980, -0.6650},
306 {-0.3260, -0.3070, 1.4090, -0.6552},
307 {-0.3511, -0.3074, 1.4470, -0.6442},
308 {-0.3501, -0.3064, 1.4500, -0.6442},
309 {-0.3490, -0.3027, 1.4550, -0.6418},
310 {-0.3487, -0.3048, 1.4570, -0.6447},
311 {-0.3478, -0.3074, 1.4600, -0.6483},
312 {-0.3501, -0.3283, 1.4540, -0.6669},
313 {-0.3494, -0.3373, 1.4550, -0.6765},
314 {-0.3485, -0.3373, 1.4570, -0.6774},
315
316 {-0.3462, -0.3300, 1.4630, -0.6728},
317 {-0.3462, -0.3225, 1.4690, -0.6662},
318 {-0.3453, -0.3094, 1.4790, -0.6553},
319 {-0.3844, -0.3134, 1.5240, -0.6412},
320 {-0.3848, -0.3018, 1.5310, -0.6303},
321 {-0.3862, -0.2955, 1.5360, -0.6237},
322 {-0.4262, -0.2991, 1.5860, -0.6115},
323 {-0.4278, -0.2910, 1.5900, -0.6029},
324 {-0.4303, -0.2817, 1.5940, -0.5927},
325 {-0.4315, -0.2719, 1.6010, -0.5829},
326
327 {-0.4359, -0.2914, 1.6050, -0.6010},
328 {-0.4365, -0.2982, 1.6080, -0.6080},
329 {-0.4253, -0.3037, 1.6120, -0.6150},
330 {-0.4335, -0.3245, 1.6160, -0.6377},
331 {-0.4307, -0.3292, 1.6210, -0.6447},
332 {-0.4284, -0.3204, 1.6290, -0.6380},
333 {-0.4227, -0.3217, 1.6360, -0.6438}
334 } ;
335
336 G4int iz = G4lrint(Z) - 2;
337 if( 0 > iz ) { iz = 0; }
338 else if(95 < iz ) { iz = 95; }
339
340 const G4double ss = 1.0 + a[iz][0]*g4calc->powA(energy,a[iz][1])+
341 + a[iz][2]*g4calc->powA(energy,a[iz][3]);
342
343 // protection for the validity range for low beta
344 static const G4double slim = 0.001;
345 if(ss < slim) { s1 = 1.0/slim; }
346 // for high value of beta
347 else if(s1*ss < 1.0) { s1 = 1.0/ss; }
348 }
349 G4int i = 0 ;
350 G4double factor = 1.0 ;
351
352 // The index of set of parameters i = 0 for protons(hadrons) in gases
353 // 1 for protons(hadrons) in solids
354 // 2 for ions in atomic gases
355 // 3 for ions in molecular gases
356 // 4 for ions in solids
357 static const G4double b[5][4] = {
358 {0.1014, 0.3700, 0.9642, 3.987},
359 {0.1955, 0.6941, 2.522, 1.040},
360 {0.05058, 0.08975, 0.1419, 10.80},
361 {0.05009, 0.08660, 0.2751, 3.787},
362 {0.01273, 0.03458, 0.3951, 3.812}
363 } ;
364
365 // protons (hadrons)
366 if(1.5 > charge) {
367 if( kStateGas != material->GetState() ) { i = 1; }
368
369 // ions
370 } else {
371
372 factor = charge * g4calc->A13(charge/Z);
373
374 if( kStateGas == material->GetState() ) {
375 energy /= (charge * std::sqrt(charge)) ;
376
377 if(1 == (material->GetNumberOfElements())) {
378 i = 2 ;
379 } else {
380 i = 3 ;
381 }
382
383 } else {
384 energy /= (charge * std::sqrt(charge*Z)) ;
385 i = 4 ;
386 }
387 }
388
389 G4double x = b[i][2];
390 G4double y = energy * b[i][3];
391 if(y <= 0.2) x *= (y*(1.0 - 0.5*y));
392 else x *= (1.0 - g4calc->expA(-y));
393
394 y = energy - b[i][1];
395
396 const G4double s2 = factor * x * b[i][0] / (y*y + x*x);
397 /*
398 G4cout << "s1= " << s1 << " s2= " << s2 << " q^2= " << effChargeSquare
399 << " e= " << energy << G4endl;
400 */
401 return s1*effChargeSquare/chargeSquare + s2;
402 }
403
404 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
405
406 G4double G4IonFluctuations::RelativisticFactor(const G4Material* mat,
407 G4double Z)
408 {
409 G4double eF = mat->GetIonisation()->GetFermiEnergy();
410 G4double I = mat->GetIonisation()->GetMeanExcitationEnergy();
411
412 // H.Geissel et al. NIM B, 195 (2002) 3.
413 G4double bF2= 2.0*eF/CLHEP::electron_mass_c2;
414 G4double f = 0.4*(1.0 - beta2)/((1.0 - 0.5*beta2)*Z);
415 if(beta2 > bF2) f *= G4Log(2.0*CLHEP::electron_mass_c2*beta2/I)*bF2/beta2;
416 else f *= G4Log(4.0*eF/I);
417
418 // G4cout << "f= " << f << " beta2= " << beta2
419 // << " bf2= " << bF2 << " q^2= " << chargeSquare << G4endl;
420
421 return 1.0 + f;
422 }
423
424 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
425
426 void G4IonFluctuations::SetParticleAndCharge(const G4ParticleDefinition* part,
427 G4double q2)
428 {
429 if(part != particle) {
430 particle = part;
431 particleMass = part->GetPDGMass();
432 charge = part->GetPDGCharge()/eplus;
433 chargeSquare = charge*charge;
434 }
435 effChargeSquare = q2;
436 uniFluct->SetParticleAndCharge(part, q2);
437 }
438
439 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
440