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27 // -------------------------------------------------------------------
28 //
29 // GEANT4 Class file
30 //
31 //
32 // File name: G4Generator2BN
33 //
34 // Author: Andreia Trindade (andreia@lip.pt)
35 // Pedro Rodrigues (psilva@lip.pt)
36 // Luis Peralta (luis@lip.pt)
37 //
38 // Creation date: 21 June 2003
39 //
40 // Modifications:
41 // 21 Jun 2003 First implementation acording with new design
42 // 05 Nov 2003 MGP Fixed compilation warning
43 // 14 Mar 2004 Code optimization
44 //
45 // Class Description:
46 //
47 // Concrete base class for Bremsstrahlung Angular Distribution Generation
48 // 2BN Distribution
49 //
50 // Class Description: End
51 //
52 // -------------------------------------------------------------------
53 //
54
55 #include "G4Generator2BN.hh"
56 #include "Randomize.hh"
57 #include "G4PhysicalConstants.hh"
58 #include "G4SystemOfUnits.hh"
59 #include "G4Exp.hh"
60
61 //
62
63 G4double G4Generator2BN::Atab[320] =
64 { 0.0264767, 0.0260006, 0.0257112, 0.0252475, 0.024792, 0.0243443, 0.0240726, 0.0236367,
65 0.023209, 0.0227892, 0.0225362, 0.0221284, 0.0217282,0.0214894, 0.0211005, 0.0207189,
66 0.0204935, 0.0201227, 0.0197588, 0.019546, 0.0191923,0.0188454, 0.0186445, 0.0183072,
67 0.0179763, 0.0177866, 0.0174649, 0.0172828, 0.0169702,0.0166634, 0.0164915, 0.0161933,
68 0.0160283, 0.0157384, 0.0155801, 0.0152981, 0.0151463,0.0148721, 0.0147263, 0.0144598,
69 0.01432, 0.0140607, 0.0139267, 0.0136744, 0.0135459,0.0133005, 0.0131773, 0.0129385,
70 0.0128205, 0.0125881, 0.012475, 0.0122488, 0.0121406,0.0119204, 0.0118167, 0.0117158,
71 0.0115032, 0.0114067, 0.0111995, 0.0111072, 0.0110175,0.0108173, 0.0107316, 0.0105365,
72 0.0104547, 0.0102646, 0.0101865, 0.010111, 0.00992684,0.0098548,0.00967532,0.00960671,
73 0.00943171,0.00936643,0.00930328,0.0091337, 0.00907372,0.00890831,0.00885141,0.00869003,
74 0.00863611,0.00858428,0.00842757,0.00837854,0.0082256,0.00817931,0.00803,0.00798639,
75 0.00784058,0.00779958,0.00776046,0.00761866,0.00758201,0.00744346,0.00740928,0.00727384,
76 0.00724201,0.00710969,0.00708004,0.00695074,0.00692333,0.00679688,0.00677166,0.00664801,
77 0.00662484,0.00650396,0.00648286,0.00636458,0.00634545,0.00622977,0.00621258,0.00609936,
78 0.00608412,0.00597331,0.00595991,0.00585143,0.00583988,0.0057337,0.0057239,0.00561991,
79 0.0056119, 0.00551005,0.00550377,0.00540399,0.00539938,0.00530162,0.00529872,0.00520292,
80 0.0051091, 0.00510777,0.00501582,0.00501608,0.00492594,0.00492781,0.00483942,0.0048429,
81 0.00475622,0.00476127,0.00467625,0.00468287,0.00459947,0.00451785,0.00452581,0.00444573,
82 0.00445522,0.00437664,0.00438768,0.00431057,0.00432316,0.00424745,0.0042616,0.00418726,
83 0.004203, 0.00413, 0.00405869,0.00407563,0.00400561,0.00402414,0.00395536,0.00397553,
84 0.00390795,0.00392975,0.00386339,0.00379862,0.00382167,0.00375805,0.00378276,0.00372031,
85 0.00374678,0.00368538,0.00371363,0.00365335,0.00359463,0.0036242, 0.00356653,0.003598,
86 0.00354139,0.00357481,0.00351921,0.00355464,0.00350005,0.0034471,0.00348403,0.00343208,
87 0.0034712, 0.00342026,0.00346165,0.00341172,0.00345548,0.00340657,0.00335944,0.00340491,
88 0.00335885,0.00340692,0.00336191,0.00341273,0.00336879,0.00342249,0.00337962,0.00333889,
89 0.00339463,0.00335506,0.00341401,0.00337558,0.00343797,0.00340067,0.00336584,0.00343059,
90 0.0033969, 0.00346557,0.00343302,0.00350594,0.00347448,0.00344563,0.00352163,0.00349383,
91 0.00357485,0.00354807,0.00352395,0.00360885,0.00358571,0.00367661,0.00365446,0.00375194,
92 0.00373078,0.00371234,0.00381532,0.00379787,0.00390882,0.00389241,0.00387881,0.00399675,
93 0.00398425,0.00411183,0.00410042,0.00409197,0.00422843,0.00422123,0.00436974,0.0043637,
94 0.00436082,0.00452075,0.00451934,0.00452125,0.00469406,0.00469756,0.00488741,0.00489221,
95 0.00490102,0.00510782,0.00511801,0.00513271,0.0053589, 0.00537524,0.00562643,0.00564452,
96 0.0056677, 0.00594482,0.00596999,0.0059999, 0.00630758,0.00634014,0.00637849,0.00672136,
97 0.00676236,0.00680914,0.00719407,0.0072439, 0.00730063,0.0077349, 0.00779494,0.00786293,
98 0.00835577,0.0084276, 0.00850759,0.00907162,0.00915592,0.00924925,0.00935226,0.00999779,
99 0.0101059, 0.0102249, 0.0109763, 0.0111003, 0.0112367, 0.0113862, 0.0122637, 0.0124196,
100 0.0125898, 0.0136311, 0.0138081, 0.0140011, 0.0142112, 0.0154536, 0.0156723, 0.0159099,
101 0.016168, 0.0176664, 0.0179339, 0.0182246, 0.0185396, 0.020381, 0.0207026, 0.0210558,
102 0.0214374, 0.0237377, 0.0241275, 0.0245528, 0.0250106, 0.0255038, 0.0284158, 0.0289213,
103 0.0294621, 0.0300526, 0.0338619, 0.0344537, 0.0351108, 0.0358099, 0.036554, 0.0416399
104 };
105
106 G4double G4Generator2BN::ctab[320] =
107 { 0.482253, 0.482253, 0.489021, 0.489021, 0.489021, 0.489021, 0.495933,
108 0.495933, 0.495933, 0.495933, 0.502993, 0.502993, 0.502993, 0.510204,
109 0.510204, 0.510204, 0.517572, 0.517572, 0.517572, 0.5251, 0.5251,
110 0.5251, 0.532793, 0.532793, 0.532793, 0.540657, 0.540657, 0.548697,
111 0.548697, 0.548697, 0.556917, 0.556917, 0.565323, 0.565323, 0.573921,
112 0.573921, 0.582717, 0.582717, 0.591716, 0.591716, 0.600925, 0.600925,
113 0.610352, 0.610352, 0.620001, 0.620001, 0.629882, 0.629882, 0.64,
114 0.64, 0.650364, 0.650364, 0.660982, 0.660982, 0.671862, 0.683013,
115 0.683013, 0.694444, 0.694444, 0.706165, 0.718184, 0.718184, 0.730514,
116 0.730514, 0.743163, 0.743163, 0.756144, 0.769468, 0.769468, 0.783147,
117 0.783147, 0.797194, 0.797194, 0.811622, 0.826446, 0.826446, 0.84168,
118 0.84168, 0.857339, 0.857339, 0.873439, 0.889996, 0.889996, 0.907029,
119 0.907029, 0.924556, 0.924556, 0.942596, 0.942596, 0.961169, 0.980296,
120 0.980296, 1, 1, 1.0203, 1.0203, 1.04123, 1.04123,
121 1.06281, 1.06281, 1.08507, 1.08507, 1.10803, 1.10803, 1.13173,
122 1.13173, 1.1562, 1.1562, 1.18147, 1.18147, 1.20758, 1.20758,
123 1.23457, 1.23457, 1.26247, 1.26247, 1.29132, 1.29132, 1.32118,
124 1.32118, 1.35208, 1.35208, 1.38408, 1.38408, 1.41723, 1.41723,
125 1.45159, 1.45159, 1.45159, 1.48721, 1.48721, 1.52416, 1.52416,
126 1.5625, 1.5625, 1.60231, 1.60231, 1.64366, 1.64366, 1.68663,
127 1.68663, 1.68663, 1.7313, 1.7313, 1.77778, 1.77778, 1.82615,
128 1.82615, 1.87652, 1.87652, 1.92901, 1.92901, 1.98373, 1.98373,
129 1.98373, 2.04082, 2.04082, 2.1004, 2.1004, 2.16263, 2.16263,
130 2.22767, 2.22767, 2.22767, 2.29568, 2.29568, 2.36686, 2.36686,
131 2.44141, 2.44141, 2.51953, 2.51953, 2.51953, 2.60146, 2.60146,
132 2.68745, 2.68745, 2.77778, 2.77778, 2.87274, 2.87274, 2.87274,
133 2.97265, 2.97265, 3.07787, 3.07787, 3.18878, 3.18878, 3.30579,
134 3.30579, 3.30579, 3.42936, 3.42936, 3.55999, 3.55999, 3.69822,
135 3.69822, 3.84468, 3.84468, 3.84468, 4, 4, 4.16493,
136 4.16493, 4.34028, 4.34028, 4.34028, 4.52694, 4.52694, 4.7259,
137 4.7259, 4.93827, 4.93827, 4.93827, 5.16529, 5.16529, 5.40833,
138 5.40833, 5.40833, 5.66893, 5.66893, 5.94884, 5.94884, 6.25,
139 6.25, 6.25, 6.57462, 6.57462, 6.92521, 6.92521, 6.92521,
140 7.3046, 7.3046, 7.71605, 7.71605, 7.71605, 8.16327, 8.16327,
141 8.65052, 8.65052, 8.65052, 9.18274, 9.18274, 9.18274, 9.76562,
142 9.76562, 10.4058, 10.4058, 10.4058, 11.1111, 11.1111, 11.1111,
143 11.8906, 11.8906, 12.7551, 12.7551, 12.7551, 13.7174, 13.7174,
144 13.7174, 14.7929, 14.7929, 14.7929, 16, 16, 16,
145 17.3611, 17.3611, 17.3611, 18.9036, 18.9036, 18.9036, 20.6612,
146 20.6612, 20.6612, 22.6757, 22.6757, 22.6757, 22.6757, 25,
147 25, 25, 27.7008, 27.7008, 27.7008, 27.7008, 30.8642,
148 30.8642, 30.8642, 34.6021, 34.6021, 34.6021, 34.6021, 39.0625,
149 39.0625, 39.0625, 39.0625, 44.4444, 44.4444, 44.4444, 44.4444,
150 51.0204, 51.0204, 51.0204, 51.0204, 59.1716, 59.1716, 59.1716,
151 59.1716, 59.1716, 69.4444, 69.4444, 69.4444, 69.4444, 82.6446,
152 82.6446, 82.6446, 82.6446, 82.6446, 100
153 };
154
155 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
156
157 G4Generator2BN::G4Generator2BN(const G4String&)
158 : G4VEmAngularDistribution("AngularGen2BN")
159 {
160 b = 1.2;
161 index_min = -300;
162 index_max = 319;
163
164 // Set parameters minimum limits Ekelectron = 250 eV and kphoton = 100 eV
165 kmin = 100*eV;
166 Ekmin = 250*eV;
167 kcut = 100*eV;
168
169 // Increment Theta value for surface interpolation
170 dtheta = 0.1*rad;
171
172 nwarn = 0;
173
174 // Construct Majorant Surface to 2BN cross-section
175 // (we dont need this. Pre-calculated values are used instead due to performance issues
176 // ConstructMajorantSurface();
177 }
178
179 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
180
181 G4ThreeVector& G4Generator2BN::SampleDirection(const G4DynamicParticle* dp,
182 G4double out_energy,
183 G4int,
184 const G4Material*)
185 {
186 G4double Ek = dp->GetKineticEnergy();
187 G4double Eel = dp->GetTotalEnergy();
188 if(Eel > 2*MeV) {
189 return fGenerator2BS.SampleDirection(dp, out_energy, 0);
190 }
191
192 G4double k = Eel - out_energy;
193
194 G4double t;
195 G4double cte2;
196 G4double y, u;
197 G4double ds;
198 G4double dmax;
199
200 // find table index
201 G4int index = G4int(std::log10(Ek/MeV)*100) - index_min;
202 if(index > index_max) { index = index_max; }
203 else if(index < 0) { index = 0; }
204
205 G4double c = ctab[index];
206 G4double A = Atab[index];
207 if(index < index_max) { A = std::max(A, Atab[index+1]); }
208
209 do{
210 // generate k accordimg to std::pow(k,-b)
211
212 // normalization constant
213 // cte1 = (1-b)/(std::pow(kmax,(1-b))-std::pow(kmin2,(1-b)));
214 // y = G4UniformRand();
215 // k = std::pow(((1-b)/cte1*y+std::pow(kmin2,(1-b))),(1/(1-b)));
216
217 // generate theta accordimg to theta/(1+c*std::pow(theta,2)
218 // Normalization constant
219 cte2 = 2*c/std::log(1+c*pi2);
220
221 y = G4UniformRand();
222 t = std::sqrt((G4Exp(2*c*y/cte2)-1)/c);
223 u = G4UniformRand();
224
225 // point acceptance algorithm
226 //fk = std::pow(k,-b);
227 //ft = t/(1+c*t*t);
228 dmax = A*std::pow(k,-b)*t/(1+c*t*t);
229 ds = Calculatedsdkdt(k,t,Eel);
230
231 // violation point
232 if(ds > dmax && nwarn >= 20) {
233 ++nwarn;
234 G4cout << "### WARNING in G4Generator2BN: Ekin(MeV)= " << Ek/MeV
235 << " D(Ekin,k)/Dmax-1= " << (ds/dmax - 1)
236 << " results are not reliable!"
237 << G4endl;
238 if(20 == nwarn) {
239 G4cout << " WARNING in G4Generator2BN is closed" << G4endl;
240 }
241 }
242
243 } while(u*dmax > ds || t > CLHEP::pi);
244
245 G4double sint = std::sin(t);
246 G4double phi = twopi*G4UniformRand();
247
248 fLocalDirection.set(sint*std::cos(phi), sint*std::sin(phi),std::cos(t));
249 fLocalDirection.rotateUz(dp->GetMomentumDirection());
250
251 return fLocalDirection;
252 }
253
254 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
255
256 G4double G4Generator2BN::CalculateFkt(G4double k, G4double theta, G4double A, G4double c) const
257 {
258 G4double Fkt_value = 0;
259 Fkt_value = A*std::pow(k,-b)*theta/(1+c*theta*theta);
260 return Fkt_value;
261 }
262
263 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
264
265 G4double G4Generator2BN::Calculatedsdkdt(G4double kout, G4double theta, G4double Eel) const
266 {
267 G4double dsdkdt_value = 0.;
268 G4double Z = 1;
269 // classic radius (in cm)
270 G4double r0 = 2.82E-13;
271 //squared classic radius (in barn)
272 G4double r02 = r0*r0*1.0E+24;
273
274 // Photon energy cannot be greater than electron kinetic energy
275 if(kout > (Eel-electron_mass_c2)){
276 dsdkdt_value = 0;
277 return dsdkdt_value;
278 }
279
280 G4double E0 = Eel/electron_mass_c2;
281 G4double k = kout/electron_mass_c2;
282 G4double E = E0 - k;
283
284 if(E <= 1*MeV ){ // Kinematic limit at 1 MeV !!
285 dsdkdt_value = 0;
286 return dsdkdt_value;
287 }
288
289 G4double p0 = std::sqrt(E0*E0-1);
290 G4double p = std::sqrt(E*E-1);
291 G4double LL = std::log((E*E0-1+p*p0)/(E*E0-1-p*p0));
292 G4double delta0 = E0 - p0*std::cos(theta);
293 G4double epsilon = std::log((E+p)/(E-p));
294 G4double Z2 = Z*Z;
295 G4double sintheta2 = std::sin(theta)*std::sin(theta);
296 G4double E02 = E0*E0;
297 G4double E2 = E*E;
298 G4double p02 = E0*E0-1;
299 G4double k2 = k*k;
300 G4double delta02 = delta0*delta0;
301 G4double delta04 = delta02* delta02;
302 G4double Q = std::sqrt(p02+k2-2*k*p0*std::cos(theta));
303 G4double Q2 = Q*Q;
304 G4double epsilonQ = std::log((Q+p)/(Q-p));
305
306
307 dsdkdt_value = Z2 * (r02/(8*pi*137)) * (1/k) * (p/p0) *
308 ( (8 * (sintheta2*(2*E02+1))/(p02*delta04)) -
309 ((2*(5*E02+2*E*E0+3))/(p02 * delta02)) -
310 ((2*(p02-k2))/((Q2*delta02))) +
311 ((4*E)/(p02*delta0)) +
312 (LL/(p*p0))*(
313 ((4*E0*sintheta2*(3*k-p02*E))/(p02*delta04)) +
314 ((4*E02*(E02+E2))/(p02*delta02)) +
315 ((2-2*(7*E02-3*E*E0+E2))/(p02*delta02)) +
316 (2*k*(E02+E*E0-1))/((p02*delta0))
317 ) -
318 ((4*epsilon)/(p*delta0)) +
319 ((epsilonQ)/(p*Q))*
320 (4/delta02-(6*k/delta0)-(2*k*(p02-k2))/(Q2*delta0))
321 );
322
323 dsdkdt_value = dsdkdt_value*std::sin(theta);
324 return dsdkdt_value;
325 }
326
327 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
328
329 void G4Generator2BN::ConstructMajorantSurface()
330 {
331 G4double Eel;
332 G4int vmax;
333 G4double Ek;
334 G4double k, theta, k0, theta0, thetamax;
335 G4double ds, df, dsmax, dk, dt;
336 G4double ratmin;
337 G4double ratio = 0;
338 G4double Vds, Vdf;
339 G4double A, c;
340
341 G4cout << "**** Constructing Majorant Surface for 2BN Distribution ****" << G4endl;
342
343 if(kcut > kmin) kmin = kcut;
344
345 G4int i = 0;
346 // Loop on energy index
347 for(G4int index = index_min; index < index_max; index++){
348
349 G4double fraction = index/100.;
350 Ek = std::pow(10.,fraction);
351 Eel = Ek + electron_mass_c2;
352
353 // find x-section maximum at k=kmin
354 dsmax = 0.;
355 thetamax = 0.;
356
357 for(theta = 0.; theta < pi; theta = theta + dtheta){
358
359 ds = Calculatedsdkdt(kmin, theta, Eel);
360
361 if(ds > dsmax){
362 dsmax = ds;
363 thetamax = theta;
364 }
365 }
366
367 // Compute surface paremeters at kmin
368 if(Ek < kmin || thetamax == 0){
369 c = 0;
370 A = 0;
371 }else{
372 c = 1/(thetamax*thetamax);
373 A = 2*std::sqrt(c)*dsmax/(std::pow(kmin,-b));
374 }
375
376 // look for correction factor to normalization at kmin
377 ratmin = 1.;
378
379 // Volume under surfaces
380 Vds = 0.;
381 Vdf = 0.;
382 k0 = 0.;
383 theta0 = 0.;
384
385 vmax = G4int(100.*std::log10(Ek/kmin));
386
387 for(G4int v = 0; v < vmax; v++){
388 G4double fractionLocal = (v/100.);
389 k = std::pow(10.,fractionLocal)*kmin;
390
391 for(theta = 0.; theta < pi; theta = theta + dtheta){
392 dk = k - k0;
393 dt = theta - theta0;
394 ds = Calculatedsdkdt(k,theta, Eel);
395 Vds = Vds + ds*dk*dt;
396 df = CalculateFkt(k,theta, A, c);
397 Vdf = Vdf + df*dk*dt;
398
399 if(ds != 0.){
400 if(df != 0.) ratio = df/ds;
401 }
402
403 if(ratio < ratmin && ratio != 0.){
404 ratmin = ratio;
405 }
406 }
407 }
408
409 // sampling efficiency
410 Atab[i] = A/ratmin * 1.04;
411 ctab[i] = c;
412
413 // G4cout << Ek << " " << i << " " << index << " " << Atab[i] << " " << ctab[i] << " " << G4endl;
414 i++;
415 }
416 }
417
418 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
419
420 void G4Generator2BN::PrintGeneratorInformation() const
421 {
422 G4cout << "\n" << G4endl;
423 G4cout << "Bremsstrahlung Angular Generator is 2BN Generator from 2BN Koch & Motz distribution (Rev Mod Phys 31(4), 920 (1959))" << G4endl;
424 G4cout << "\n" << G4endl;
425 }
426