source: trunk/source/processes/hadronic/models/rpg/src/G4RPGNeutronInelastic.cc@ 819

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26// $Id: G4RPGNeutronInelastic.cc,v 1.1 2007/07/18 21:04:20 dennis Exp $
27// GEANT4 tag $Name: geant4-09-01-patch-02 $
28//
29
30#include "G4RPGNeutronInelastic.hh"
31#include "Randomize.hh"
32#include "G4Electron.hh"
33// #include "DumpFrame.hh"
34
35 G4HadFinalState *
36 G4RPGNeutronInelastic::ApplyYourself( const G4HadProjectile &aTrack,
37 G4Nucleus &targetNucleus )
38 {
39 theParticleChange.Clear();
40 const G4HadProjectile *originalIncident = &aTrack;
41 //
42 // create the target particle
43 //
44 G4DynamicParticle *originalTarget = targetNucleus.ReturnTargetParticle();
45
46 if( verboseLevel > 1 )
47 {
48 const G4Material *targetMaterial = aTrack.GetMaterial();
49 G4cout << "G4RPGNeutronInelastic::ApplyYourself called" << G4endl;
50 G4cout << "kinetic energy = " << originalIncident->GetKineticEnergy()/MeV << "MeV, ";
51 G4cout << "target material = " << targetMaterial->GetName() << ", ";
52 G4cout << "target particle = " << originalTarget->GetDefinition()->GetParticleName()
53 << G4endl;
54 }
55/* not true, for example for Fe56, etc..
56 if( originalIncident->GetKineticEnergy()/MeV < 0.000001 )
57 throw G4HadronicException(__FILE__, __LINE__, "G4RPGNeutronInelastic: should be capture process!");
58 if( originalIncident->Get4Momentum().vect().mag()/MeV < 0.000001 )
59 throw G4HadronicException(__FILE__, __LINE__, "G4RPGNeutronInelastic: should be capture process!");
60*/
61
62 G4ReactionProduct modifiedOriginal;
63 modifiedOriginal = *originalIncident;
64 G4ReactionProduct targetParticle;
65 targetParticle = *originalTarget;
66 if( originalIncident->GetKineticEnergy()/GeV < 0.01 + 2.*G4UniformRand()/9. )
67 {
68 SlowNeutron( originalIncident, modifiedOriginal, targetParticle, targetNucleus );
69 delete originalTarget;
70 return &theParticleChange;
71 }
72 //
73 // Fermi motion and evaporation
74 // As of Geant3, the Fermi energy calculation had not been Done
75 //
76 G4double ek = originalIncident->GetKineticEnergy()/MeV;
77 G4double amas = originalIncident->GetDefinition()->GetPDGMass()/MeV;
78
79 G4double tkin = targetNucleus.Cinema( ek );
80 ek += tkin;
81 modifiedOriginal.SetKineticEnergy( ek*MeV );
82 G4double et = ek + amas;
83 G4double p = std::sqrt( std::abs((et-amas)*(et+amas)) );
84 G4double pp = modifiedOriginal.GetMomentum().mag()/MeV;
85 if( pp > 0.0 )
86 {
87 G4ThreeVector momentum = modifiedOriginal.GetMomentum();
88 modifiedOriginal.SetMomentum( momentum * (p/pp) );
89 }
90 //
91 // calculate black track energies
92 //
93 tkin = targetNucleus.EvaporationEffects( ek );
94 ek -= tkin;
95 modifiedOriginal.SetKineticEnergy( ek*MeV );
96 et = ek + amas;
97 p = std::sqrt( std::abs((et-amas)*(et+amas)) );
98 pp = modifiedOriginal.GetMomentum().mag()/MeV;
99 if( pp > 0.0 )
100 {
101 G4ThreeVector momentum = modifiedOriginal.GetMomentum();
102 modifiedOriginal.SetMomentum( momentum * (p/pp) );
103 }
104 const G4double cutOff = 0.1;
105 if( modifiedOriginal.GetKineticEnergy()/MeV <= cutOff )
106 {
107 SlowNeutron( originalIncident, modifiedOriginal, targetParticle, targetNucleus );
108 delete originalTarget;
109 return &theParticleChange;
110 }
111 G4ReactionProduct currentParticle = modifiedOriginal;
112 currentParticle.SetSide( 1 ); // incident always goes in forward hemisphere
113 targetParticle.SetSide( -1 ); // target always goes in backward hemisphere
114 G4bool incidentHasChanged = false;
115 G4bool targetHasChanged = false;
116 G4bool quasiElastic = false;
117 G4FastVector<G4ReactionProduct,256> vec; // vec will contain the secondary particles
118 G4int vecLen = 0;
119 vec.Initialize( 0 );
120
121 Cascade( vec, vecLen,
122 originalIncident, currentParticle, targetParticle,
123 incidentHasChanged, targetHasChanged, quasiElastic );
124
125 CalculateMomenta( vec, vecLen,
126 originalIncident, originalTarget, modifiedOriginal,
127 targetNucleus, currentParticle, targetParticle,
128 incidentHasChanged, targetHasChanged, quasiElastic );
129
130 SetUpChange( vec, vecLen,
131 currentParticle, targetParticle,
132 incidentHasChanged );
133
134 delete originalTarget;
135 return &theParticleChange;
136 }
137
138 void
139 G4RPGNeutronInelastic::SlowNeutron(
140 const G4HadProjectile *originalIncident,
141 G4ReactionProduct &modifiedOriginal,
142 G4ReactionProduct &targetParticle,
143 G4Nucleus &targetNucleus )
144 {
145 const G4double A = targetNucleus.GetN(); // atomic weight
146 const G4double Z = targetNucleus.GetZ(); // atomic number
147
148 G4double currentKinetic = modifiedOriginal.GetKineticEnergy()/MeV;
149 G4double currentMass = modifiedOriginal.GetMass()/MeV;
150 if( A < 1.5 ) // Hydrogen
151 {
152 //
153 // very simple simulation of scattering angle and energy
154 // nonrelativistic approximation with isotropic angular
155 // distribution in the cms system
156 //
157 G4double cost1, eka = 0.0;
158 while (eka <= 0.0)
159 {
160 cost1 = -1.0 + 2.0*G4UniformRand();
161 eka = 1.0 + 2.0*cost1*A + A*A;
162 }
163 G4double cost = std::min( 1.0, std::max( -1.0, (A*cost1+1.0)/std::sqrt(eka) ) );
164 eka /= (1.0+A)*(1.0+A);
165 G4double ek = currentKinetic*MeV/GeV;
166 G4double amas = currentMass*MeV/GeV;
167 ek *= eka;
168 G4double en = ek + amas;
169 G4double p = std::sqrt(std::abs(en*en-amas*amas));
170 G4double sint = std::sqrt(std::abs(1.0-cost*cost));
171 G4double phi = G4UniformRand()*twopi;
172 G4double px = sint*std::sin(phi);
173 G4double py = sint*std::cos(phi);
174 G4double pz = cost;
175 targetParticle.SetMomentum( px*GeV, py*GeV, pz*GeV );
176 G4double pxO = originalIncident->Get4Momentum().x()/GeV;
177 G4double pyO = originalIncident->Get4Momentum().y()/GeV;
178 G4double pzO = originalIncident->Get4Momentum().z()/GeV;
179 G4double ptO = pxO*pxO + pyO+pyO;
180 if( ptO > 0.0 )
181 {
182 G4double pO = std::sqrt(pxO*pxO+pyO*pyO+pzO*pzO);
183 cost = pzO/pO;
184 sint = 0.5*(std::sqrt(std::abs((1.0-cost)*(1.0+cost)))+std::sqrt(ptO)/pO);
185 G4double ph = pi/2.0;
186 if( pyO < 0.0 )ph = ph*1.5;
187 if( std::abs(pxO) > 0.000001 )ph = std::atan2(pyO,pxO);
188 G4double cosp = std::cos(ph);
189 G4double sinp = std::sin(ph);
190 px = cost*cosp*px - sinp*py+sint*cosp*pz;
191 py = cost*sinp*px + cosp*py+sint*sinp*pz;
192 pz = -sint*px + cost*pz;
193 }
194 else
195 {
196 if( pz < 0.0 )pz *= -1.0;
197 }
198 G4double pu = std::sqrt(px*px+py*py+pz*pz);
199 modifiedOriginal.SetMomentum( targetParticle.GetMomentum() * (p/pu) );
200 modifiedOriginal.SetKineticEnergy( ek*GeV );
201
202 targetParticle.SetMomentum(
203 originalIncident->Get4Momentum().vect() - modifiedOriginal.GetMomentum() );
204 G4double pp = targetParticle.GetMomentum().mag();
205 G4double tarmas = targetParticle.GetMass();
206 targetParticle.SetTotalEnergy( std::sqrt( pp*pp + tarmas*tarmas ) );
207
208 theParticleChange.SetEnergyChange( modifiedOriginal.GetKineticEnergy() );
209 G4DynamicParticle *pd = new G4DynamicParticle;
210 pd->SetDefinition( targetParticle.GetDefinition() );
211 pd->SetMomentum( targetParticle.GetMomentum() );
212 theParticleChange.AddSecondary( pd );
213 return;
214 }
215 G4FastVector<G4ReactionProduct,4> vec; // vec will contain the secondary particles
216 G4int vecLen = 0;
217 vec.Initialize( 0 );
218
219 G4double theAtomicMass = targetNucleus.AtomicMass( A, Z );
220 G4double massVec[9];
221 massVec[0] = targetNucleus.AtomicMass( A+1.0, Z );
222 massVec[1] = theAtomicMass;
223 massVec[2] = 0.;
224 if (Z > 1.0)
225 massVec[2] = targetNucleus.AtomicMass( A , Z-1.0 );
226 massVec[3] = 0.;
227 if (Z > 1.0 && A > 1.0)
228 massVec[3] = targetNucleus.AtomicMass( A-1.0, Z-1.0 );
229 massVec[4] = 0.;
230 if (Z > 1.0 && A > 2.0 && A-2.0 > Z-1.0)
231 massVec[4] = targetNucleus.AtomicMass( A-2.0, Z-1.0 );
232 massVec[5] = 0.;
233 if (Z > 2.0 && A > 3.0 && A-3.0 > Z-2.0)
234 massVec[5] = targetNucleus.AtomicMass( A-3.0, Z-2.0 );
235 massVec[6] = 0.;
236 if (A > 1.0 && A-1.0 > Z)
237 massVec[6] = targetNucleus.AtomicMass( A-1.0, Z );
238 massVec[7] = massVec[3];
239 massVec[8] = 0.;
240 if (Z > 2.0 && A > 1.0)
241 massVec[8] = targetNucleus.AtomicMass( A-1.0, Z-2.0 );
242
243 twoBody.NuclearReaction(vec, vecLen, originalIncident,
244 targetNucleus, theAtomicMass, massVec );
245
246 theParticleChange.SetStatusChange( stopAndKill );
247 theParticleChange.SetEnergyChange( 0.0 );
248
249 G4DynamicParticle * pd;
250 for( G4int i=0; i<vecLen; ++i )
251 {
252 pd = new G4DynamicParticle();
253 pd->SetDefinition( vec[i]->GetDefinition() );
254 pd->SetMomentum( vec[i]->GetMomentum() );
255 theParticleChange.AddSecondary( pd );
256 delete vec[i];
257 }
258 }
259
260 void
261 G4RPGNeutronInelastic::Cascade(
262 G4FastVector<G4ReactionProduct,256> &vec,
263 G4int& vecLen,
264 const G4HadProjectile *originalIncident,
265 G4ReactionProduct &currentParticle,
266 G4ReactionProduct &targetParticle,
267 G4bool &incidentHasChanged,
268 G4bool &targetHasChanged,
269 G4bool &quasiElastic )
270 {
271 // derived from original FORTRAN code CASN by H. Fesefeldt (13-Sep-1987)
272 //
273 // Neutron undergoes interaction with nucleon within a nucleus. Check if it is
274 // energetically possible to produce pions/kaons. In not, assume nuclear excitation
275 // occurs and input particle is degraded in energy. No other particles are produced.
276 // If reaction is possible, find the correct number of pions/protons/neutrons
277 // produced using an interpolation to multiplicity data. Replace some pions or
278 // protons/neutrons by kaons or strange baryons according to the average
279 // multiplicity per Inelastic reaction.
280 //
281 const G4double mOriginal = originalIncident->GetDefinition()->GetPDGMass()/MeV;
282 const G4double etOriginal = originalIncident->GetTotalEnergy()/MeV;
283 const G4double targetMass = targetParticle.GetMass()/MeV;
284 G4double centerofmassEnergy = std::sqrt( mOriginal*mOriginal +
285 targetMass*targetMass +
286 2.0*targetMass*etOriginal );
287 G4double availableEnergy = centerofmassEnergy-(targetMass+mOriginal);
288 if( availableEnergy <= G4PionPlus::PionPlus()->GetPDGMass()/MeV )
289 {
290 quasiElastic = true;
291 return;
292 }
293 static G4bool first = true;
294 const G4int numMul = 1200;
295 const G4int numSec = 60;
296 static G4double protmul[numMul], protnorm[numSec]; // proton constants
297 static G4double neutmul[numMul], neutnorm[numSec]; // neutron constants
298 // np = number of pi+, nm = number of pi-, nz = number of pi0
299 G4int counter, nt=0, np=0, nm=0, nz=0;
300 const G4double c = 1.25;
301 const G4double b[] = { 0.35, 0.0 };
302 if( first ) // compute normalization constants, this will only be Done once
303 {
304 first = false;
305 G4int i;
306 for( i=0; i<numMul; ++i )protmul[i] = 0.0;
307 for( i=0; i<numSec; ++i )protnorm[i] = 0.0;
308 counter = -1;
309 for( np=0; np<numSec/3; ++np )
310 {
311 for( nm=std::max(0,np-1); nm<=(np+1); ++nm )
312 {
313 for( nz=0; nz<numSec/3; ++nz )
314 {
315 if( ++counter < numMul )
316 {
317 nt = np+nm+nz;
318 if( nt > 0 )
319 {
320 protmul[counter] = Pmltpc(np,nm,nz,nt,b[0],c) /
321 (Factorial(1-np+nm)*Factorial(1+np-nm) );
322 protnorm[nt-1] += protmul[counter];
323 }
324 }
325 }
326 }
327 }
328 for( i=0; i<numMul; ++i )neutmul[i] = 0.0;
329 for( i=0; i<numSec; ++i )neutnorm[i] = 0.0;
330 counter = -1;
331 for( np=0; np<(numSec/3); ++np )
332 {
333 for( nm=np; nm<=(np+2); ++nm )
334 {
335 for( nz=0; nz<numSec/3; ++nz )
336 {
337 if( ++counter < numMul )
338 {
339 nt = np+nm+nz;
340 if( (nt>0) && (nt<=numSec) )
341 {
342 neutmul[counter] = Pmltpc(np,nm,nz,nt,b[1],c) /
343 (Factorial(nm-np)*Factorial(2-nm+np) );
344 neutnorm[nt-1] += neutmul[counter];
345 }
346 }
347 }
348 }
349 }
350 for( i=0; i<numSec; ++i )
351 {
352 if( protnorm[i] > 0.0 )protnorm[i] = 1.0/protnorm[i];
353 if( neutnorm[i] > 0.0 )neutnorm[i] = 1.0/neutnorm[i];
354 }
355 } // end of initialization
356
357 const G4double expxu = 82.; // upper bound for arg. of exp
358 const G4double expxl = -expxu; // lower bound for arg. of exp
359 G4ParticleDefinition *aNeutron = G4Neutron::Neutron();
360 G4ParticleDefinition *aProton = G4Proton::Proton();
361 G4int ieab = static_cast<G4int>(availableEnergy*5.0/GeV);
362 const G4double supp[] = {0.,0.4,0.55,0.65,0.75,0.82,0.86,0.90,0.94,0.98};
363 G4double test, w0, wp, wt, wm;
364 if( (availableEnergy < 2.0*GeV) && (G4UniformRand() >= supp[ieab]) )
365 {
366 // suppress high multiplicity events at low momentum
367 // only one pion will be produced
368
369 nm = np = nz = 0;
370 if( targetParticle.GetDefinition() == aNeutron )
371 {
372 test = std::exp( std::min( expxu, std::max( expxl, -(1.0+b[1])*(1.0+b[1])/(2.0*c*c) ) ) );
373 w0 = test/2.0;
374 wm = test;
375 if( G4UniformRand() < w0/(w0+wm) )
376 nz = 1;
377 else
378 nm = 1;
379 } else { // target is a proton
380 test = std::exp( std::min( expxu, std::max( expxl, -(1.0+b[0])*(1.0+b[0])/(2.0*c*c) ) ) );
381 w0 = test;
382 wp = test/2.0;
383 test = std::exp( std::min( expxu, std::max( expxl, -(-1.0+b[0])*(-1.0+b[0])/(2.0*c*c) ) ) );
384 wm = test/2.0;
385 wt = w0+wp+wm;
386 wp += w0;
387 G4double ran = G4UniformRand();
388 if( ran < w0/wt )
389 nz = 1;
390 else if( ran < wp/wt )
391 np = 1;
392 else
393 nm = 1;
394 }
395 } else { // (availableEnergy >= 2.0*GeV) || (random number < supp[ieab])
396 G4double n, anpn;
397 GetNormalizationConstant( availableEnergy, n, anpn );
398 G4double ran = G4UniformRand();
399 G4double dum, excs = 0.0;
400 if( targetParticle.GetDefinition() == aProton )
401 {
402 counter = -1;
403 for( np=0; np<numSec/3 && ran>=excs; ++np )
404 {
405 for( nm=std::max(0,np-1); nm<=(np+1) && ran>=excs; ++nm )
406 {
407 for( nz=0; nz<numSec/3 && ran>=excs; ++nz )
408 {
409 if( ++counter < numMul )
410 {
411 nt = np+nm+nz;
412 if( nt > 0 )
413 {
414 test = std::exp( std::min( expxu, std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
415 dum = (pi/anpn)*nt*protmul[counter]*protnorm[nt-1]/(2.0*n*n);
416 if( std::fabs(dum) < 1.0 ) {
417 if( test >= 1.0e-10 )excs += dum*test;
418 } else {
419 excs += dum*test;
420 }
421 }
422 }
423 }
424 }
425 }
426 if( ran >= excs ) // 3 previous loops continued to the end
427 {
428 quasiElastic = true;
429 return;
430 }
431 np--; nm--; nz--;
432 } else { // target must be a neutron
433 counter = -1;
434 for( np=0; np<numSec/3 && ran>=excs; ++np )
435 {
436 for( nm=np; nm<=(np+2) && ran>=excs; ++nm )
437 {
438 for( nz=0; nz<numSec/3 && ran>=excs; ++nz )
439 {
440 if( ++counter < numMul )
441 {
442 nt = np+nm+nz;
443 if( (nt>=1) && (nt<=numSec) )
444 {
445 test = std::exp( std::min( expxu, std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
446 dum = (pi/anpn)*nt*neutmul[counter]*neutnorm[nt-1]/(2.0*n*n);
447 if( std::fabs(dum) < 1.0 ) {
448 if( test >= 1.0e-10 )excs += dum*test;
449 } else {
450 excs += dum*test;
451 }
452 }
453 }
454 }
455 }
456 }
457 if( ran >= excs ) // 3 previous loops continued to the end
458 {
459 quasiElastic = true;
460 return;
461 }
462 np--; nm--; nz--;
463 }
464 }
465 if( targetParticle.GetDefinition() == aProton )
466 {
467 switch( np-nm )
468 {
469 case 0:
470 if( G4UniformRand() < 0.33 )
471 {
472 currentParticle.SetDefinitionAndUpdateE( aProton );
473 targetParticle.SetDefinitionAndUpdateE( aNeutron );
474 incidentHasChanged = true;
475 targetHasChanged = true;
476 }
477 break;
478 case 1:
479 targetParticle.SetDefinitionAndUpdateE( aNeutron );
480 targetHasChanged = true;
481 break;
482 default:
483 currentParticle.SetDefinitionAndUpdateE( aProton );
484 incidentHasChanged = true;
485 break;
486 }
487 } else { // target must be a neutron
488 switch( np-nm )
489 {
490 case -1: // changed from +1 by JLC, 7Jul97
491 if( G4UniformRand() < 0.5 )
492 {
493 currentParticle.SetDefinitionAndUpdateE( aProton );
494 incidentHasChanged = true;
495 } else {
496 targetParticle.SetDefinitionAndUpdateE( aProton );
497 targetHasChanged = true;
498 }
499 break;
500 case 0:
501 break;
502 default:
503 currentParticle.SetDefinitionAndUpdateE( aProton );
504 targetParticle.SetDefinitionAndUpdateE( aProton );
505 incidentHasChanged = true;
506 targetHasChanged = true;
507 break;
508 }
509 }
510 SetUpPions( np, nm, nz, vec, vecLen );
511// DEBUG --> DumpFrames::DumpFrame(vec, vecLen);
512 return;
513 }
514
515 /* end of file */
516
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