source: trunk/source/processes/hadronic/models/low_energy/src/G4LENeutronInelastic.cc@ 1201

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27//
28// Hadronic Process: Low Energy Neutron Inelastic Process
29// J.L. Chuma, TRIUMF, 04-Feb-1997
30
31#include "G4LENeutronInelastic.hh"
32#include "Randomize.hh"
33#include "G4Electron.hh"
34// #include "DumpFrame.hh"
35
36 G4HadFinalState *
37 G4LENeutronInelastic::ApplyYourself( const G4HadProjectile &aTrack,
38 G4Nucleus &targetNucleus )
39 {
40 theParticleChange.Clear();
41 const G4HadProjectile *originalIncident = &aTrack;
42 //
43 // create the target particle
44 //
45 G4DynamicParticle *originalTarget = targetNucleus.ReturnTargetParticle();
46
47 if( verboseLevel > 1 )
48 {
49 const G4Material *targetMaterial = aTrack.GetMaterial();
50 G4cout << "G4LENeutronInelastic::ApplyYourself called" << G4endl;
51 G4cout << "kinetic energy = " << originalIncident->GetKineticEnergy()/MeV << "MeV, ";
52 G4cout << "target material = " << targetMaterial->GetName() << ", ";
53 G4cout << "target particle = " << originalTarget->GetDefinition()->GetParticleName()
54 << G4endl;
55 }
56/* not true, for example for Fe56, etc..
57 if( originalIncident->GetKineticEnergy()/MeV < 0.000001 )
58 throw G4HadronicException(__FILE__, __LINE__, "G4LENeutronInelastic: should be capture process!");
59 if( originalIncident->Get4Momentum().vect().mag()/MeV < 0.000001 )
60 throw G4HadronicException(__FILE__, __LINE__, "G4LENeutronInelastic: should be capture process!");
61*/
62
63 G4ReactionProduct modifiedOriginal;
64 modifiedOriginal = *originalIncident;
65 G4ReactionProduct targetParticle;
66 targetParticle = *originalTarget;
67 if( originalIncident->GetKineticEnergy()/GeV < 0.01 + 2.*G4UniformRand()/9. )
68 {
69 SlowNeutron( originalIncident, modifiedOriginal, targetParticle, targetNucleus );
70 delete originalTarget;
71 return &theParticleChange;
72 }
73 //
74 // Fermi motion and evaporation
75 // As of Geant3, the Fermi energy calculation had not been Done
76 //
77 G4double ek = originalIncident->GetKineticEnergy()/MeV;
78 G4double amas = originalIncident->GetDefinition()->GetPDGMass()/MeV;
79
80 G4double tkin = targetNucleus.Cinema( ek );
81 ek += tkin;
82 modifiedOriginal.SetKineticEnergy( ek*MeV );
83 G4double et = ek + amas;
84 G4double p = std::sqrt( std::abs((et-amas)*(et+amas)) );
85 G4double pp = modifiedOriginal.GetMomentum().mag()/MeV;
86 if( pp > 0.0 )
87 {
88 G4ThreeVector momentum = modifiedOriginal.GetMomentum();
89 modifiedOriginal.SetMomentum( momentum * (p/pp) );
90 }
91 //
92 // calculate black track energies
93 //
94 tkin = targetNucleus.EvaporationEffects( ek );
95 ek -= tkin;
96 modifiedOriginal.SetKineticEnergy( ek*MeV );
97 et = ek + amas;
98 p = std::sqrt( std::abs((et-amas)*(et+amas)) );
99 pp = modifiedOriginal.GetMomentum().mag()/MeV;
100 if( pp > 0.0 )
101 {
102 G4ThreeVector momentum = modifiedOriginal.GetMomentum();
103 modifiedOriginal.SetMomentum( momentum * (p/pp) );
104 }
105 const G4double cutOff = 0.1;
106 if( modifiedOriginal.GetKineticEnergy()/MeV <= cutOff )
107 {
108 SlowNeutron( originalIncident, modifiedOriginal, targetParticle, targetNucleus );
109 delete originalTarget;
110 return &theParticleChange;
111 }
112 G4ReactionProduct currentParticle = modifiedOriginal;
113 currentParticle.SetSide( 1 ); // incident always goes in forward hemisphere
114 targetParticle.SetSide( -1 ); // target always goes in backward hemisphere
115 G4bool incidentHasChanged = false;
116 G4bool targetHasChanged = false;
117 G4bool quasiElastic = false;
118 G4FastVector<G4ReactionProduct,GHADLISTSIZE> vec; // vec will contain the secondary particles
119 G4int vecLen = 0;
120 vec.Initialize( 0 );
121
122 Cascade( vec, vecLen,
123 originalIncident, currentParticle, targetParticle,
124 incidentHasChanged, targetHasChanged, quasiElastic );
125
126 CalculateMomenta( vec, vecLen,
127 originalIncident, originalTarget, modifiedOriginal,
128 targetNucleus, currentParticle, targetParticle,
129 incidentHasChanged, targetHasChanged, quasiElastic );
130
131 SetUpChange( vec, vecLen,
132 currentParticle, targetParticle,
133 incidentHasChanged );
134
135 delete originalTarget;
136 return &theParticleChange;
137 }
138
139 void
140 G4LENeutronInelastic::SlowNeutron(
141 const G4HadProjectile *originalIncident,
142 G4ReactionProduct &modifiedOriginal,
143 G4ReactionProduct &targetParticle,
144 G4Nucleus &targetNucleus )
145 {
146 const G4double A = targetNucleus.GetN(); // atomic weight
147 const G4double Z = targetNucleus.GetZ(); // atomic number
148
149 G4double currentKinetic = modifiedOriginal.GetKineticEnergy()/MeV;
150 G4double currentMass = modifiedOriginal.GetMass()/MeV;
151 if( A < 1.5 ) // Hydrogen
152 {
153 //
154 // very simple simulation of scattering angle and energy
155 // nonrelativistic approximation with isotropic angular
156 // distribution in the cms system
157 //
158 G4double cost1, eka = 0.0;
159 while (eka <= 0.0)
160 {
161 cost1 = -1.0 + 2.0*G4UniformRand();
162 eka = 1.0 + 2.0*cost1*A + A*A;
163 }
164 G4double cost = std::min( 1.0, std::max( -1.0, (A*cost1+1.0)/std::sqrt(eka) ) );
165 eka /= (1.0+A)*(1.0+A);
166 G4double ek = currentKinetic*MeV/GeV;
167 G4double amas = currentMass*MeV/GeV;
168 ek *= eka;
169 G4double en = ek + amas;
170 G4double p = std::sqrt(std::abs(en*en-amas*amas));
171 G4double sint = std::sqrt(std::abs(1.0-cost*cost));
172 G4double phi = G4UniformRand()*twopi;
173 G4double px = sint*std::sin(phi);
174 G4double py = sint*std::cos(phi);
175 G4double pz = cost;
176 targetParticle.SetMomentum( px*GeV, py*GeV, pz*GeV );
177 G4double pxO = originalIncident->Get4Momentum().x()/GeV;
178 G4double pyO = originalIncident->Get4Momentum().y()/GeV;
179 G4double pzO = originalIncident->Get4Momentum().z()/GeV;
180 G4double ptO = pxO*pxO + pyO+pyO;
181 if( ptO > 0.0 )
182 {
183 G4double pO = std::sqrt(pxO*pxO+pyO*pyO+pzO*pzO);
184 cost = pzO/pO;
185 sint = 0.5*(std::sqrt(std::abs((1.0-cost)*(1.0+cost)))+std::sqrt(ptO)/pO);
186 G4double ph = pi/2.0;
187 if( pyO < 0.0 )ph = ph*1.5;
188 if( std::abs(pxO) > 0.000001 )ph = std::atan2(pyO,pxO);
189 G4double cosp = std::cos(ph);
190 G4double sinp = std::sin(ph);
191 px = cost*cosp*px - sinp*py+sint*cosp*pz;
192 py = cost*sinp*px + cosp*py+sint*sinp*pz;
193 pz = -sint*px + cost*pz;
194 }
195 else
196 {
197 if( pz < 0.0 )pz *= -1.0;
198 }
199 G4double pu = std::sqrt(px*px+py*py+pz*pz);
200 modifiedOriginal.SetMomentum( targetParticle.GetMomentum() * (p/pu) );
201 modifiedOriginal.SetKineticEnergy( ek*GeV );
202
203 targetParticle.SetMomentum(
204 originalIncident->Get4Momentum().vect() - modifiedOriginal.GetMomentum() );
205 G4double pp = targetParticle.GetMomentum().mag();
206 G4double tarmas = targetParticle.GetMass();
207 targetParticle.SetTotalEnergy( std::sqrt( pp*pp + tarmas*tarmas ) );
208
209 theParticleChange.SetEnergyChange( modifiedOriginal.GetKineticEnergy() );
210 G4DynamicParticle *pd = new G4DynamicParticle;
211 pd->SetDefinition( targetParticle.GetDefinition() );
212 pd->SetMomentum( targetParticle.GetMomentum() );
213 theParticleChange.AddSecondary( pd );
214 return;
215 }
216 G4FastVector<G4ReactionProduct,4> vec; // vec will contain the secondary particles
217 G4int vecLen = 0;
218 vec.Initialize( 0 );
219
220 G4double theAtomicMass = targetNucleus.AtomicMass( A, Z );
221 G4double massVec[9];
222 massVec[0] = targetNucleus.AtomicMass( A+1.0, Z );
223 massVec[1] = theAtomicMass;
224 massVec[2] = 0.;
225 if (Z > 1.0)
226 massVec[2] = targetNucleus.AtomicMass( A , Z-1.0 );
227 massVec[3] = 0.;
228 if (Z > 1.0 && A > 1.0)
229 massVec[3] = targetNucleus.AtomicMass( A-1.0, Z-1.0 );
230 massVec[4] = 0.;
231 if (Z > 1.0 && A > 2.0 && A-2.0 > Z-1.0)
232 massVec[4] = targetNucleus.AtomicMass( A-2.0, Z-1.0 );
233 massVec[5] = 0.;
234 if (Z > 2.0 && A > 3.0 && A-3.0 > Z-2.0)
235 massVec[5] = targetNucleus.AtomicMass( A-3.0, Z-2.0 );
236 massVec[6] = 0.;
237 if (A > 1.0 && A-1.0 > Z)
238 massVec[6] = targetNucleus.AtomicMass( A-1.0, Z );
239 massVec[7] = massVec[3];
240 massVec[8] = 0.;
241 if (Z > 2.0 && A > 1.0)
242 massVec[8] = targetNucleus.AtomicMass( A-1.0, Z-2.0 );
243
244 theReactionDynamics.NuclearReaction( vec, vecLen, originalIncident,
245 targetNucleus, theAtomicMass, massVec );
246
247 theParticleChange.SetStatusChange( stopAndKill );
248 theParticleChange.SetEnergyChange( 0.0 );
249
250 G4DynamicParticle * pd;
251 for( G4int i=0; i<vecLen; ++i )
252 {
253 pd = new G4DynamicParticle();
254 pd->SetDefinition( vec[i]->GetDefinition() );
255 pd->SetMomentum( vec[i]->GetMomentum() );
256 theParticleChange.AddSecondary( pd );
257 delete vec[i];
258 }
259 }
260
261 void
262 G4LENeutronInelastic::Cascade(
263 G4FastVector<G4ReactionProduct,GHADLISTSIZE> &vec,
264 G4int& vecLen,
265 const G4HadProjectile *originalIncident,
266 G4ReactionProduct &currentParticle,
267 G4ReactionProduct &targetParticle,
268 G4bool &incidentHasChanged,
269 G4bool &targetHasChanged,
270 G4bool &quasiElastic )
271 {
272 // derived from original FORTRAN code CASN by H. Fesefeldt (13-Sep-1987)
273 //
274 // Neutron undergoes interaction with nucleon within a nucleus. Check if it is
275 // energetically possible to produce pions/kaons. In not, assume nuclear excitation
276 // occurs and input particle is degraded in energy. No other particles are produced.
277 // If reaction is possible, find the correct number of pions/protons/neutrons
278 // produced using an interpolation to multiplicity data. Replace some pions or
279 // protons/neutrons by kaons or strange baryons according to the average
280 // multiplicity per Inelastic reaction.
281 //
282 const G4double mOriginal = originalIncident->GetDefinition()->GetPDGMass()/MeV;
283 const G4double etOriginal = originalIncident->GetTotalEnergy()/MeV;
284 const G4double targetMass = targetParticle.GetMass()/MeV;
285 G4double centerofmassEnergy = std::sqrt( mOriginal*mOriginal +
286 targetMass*targetMass +
287 2.0*targetMass*etOriginal );
288 G4double availableEnergy = centerofmassEnergy-(targetMass+mOriginal);
289 if( availableEnergy <= G4PionPlus::PionPlus()->GetPDGMass()/MeV )
290 {
291 quasiElastic = true;
292 return;
293 }
294 static G4bool first = true;
295 const G4int numMul = 1200;
296 const G4int numSec = 60;
297 static G4double protmul[numMul], protnorm[numSec]; // proton constants
298 static G4double neutmul[numMul], neutnorm[numSec]; // neutron constants
299 // np = number of pi+, nm = number of pi-, nz = number of pi0
300 G4int counter, nt=0, np=0, nm=0, nz=0;
301 const G4double c = 1.25;
302 const G4double b[] = { 0.35, 0.0 };
303 if( first ) // compute normalization constants, this will only be Done once
304 {
305 first = false;
306 G4int i;
307 for( i=0; i<numMul; ++i )protmul[i] = 0.0;
308 for( i=0; i<numSec; ++i )protnorm[i] = 0.0;
309 counter = -1;
310 for( np=0; np<numSec/3; ++np )
311 {
312 for( nm=std::max(0,np-1); nm<=(np+1); ++nm )
313 {
314 for( nz=0; nz<numSec/3; ++nz )
315 {
316 if( ++counter < numMul )
317 {
318 nt = np+nm+nz;
319 if( nt > 0 )
320 {
321 protmul[counter] = Pmltpc(np,nm,nz,nt,b[0],c) /
322 ( theReactionDynamics.Factorial(1-np+nm)*
323 theReactionDynamics.Factorial(1+np-nm) );
324 protnorm[nt-1] += protmul[counter];
325 }
326 }
327 }
328 }
329 }
330 for( i=0; i<numMul; ++i )neutmul[i] = 0.0;
331 for( i=0; i<numSec; ++i )neutnorm[i] = 0.0;
332 counter = -1;
333 for( np=0; np<(numSec/3); ++np )
334 {
335 for( nm=np; nm<=(np+2); ++nm )
336 {
337 for( nz=0; nz<numSec/3; ++nz )
338 {
339 if( ++counter < numMul )
340 {
341 nt = np+nm+nz;
342 if( (nt>0) && (nt<=numSec) )
343 {
344 neutmul[counter] = Pmltpc(np,nm,nz,nt,b[1],c) /
345 ( theReactionDynamics.Factorial(nm-np)*
346 theReactionDynamics.Factorial(2-nm+np) );
347 neutnorm[nt-1] += neutmul[counter];
348 }
349 }
350 }
351 }
352 }
353 for( i=0; i<numSec; ++i )
354 {
355 if( protnorm[i] > 0.0 )protnorm[i] = 1.0/protnorm[i];
356 if( neutnorm[i] > 0.0 )neutnorm[i] = 1.0/neutnorm[i];
357 }
358 } // end of initialization
359
360 const G4double expxu = 82.; // upper bound for arg. of exp
361 const G4double expxl = -expxu; // lower bound for arg. of exp
362 G4ParticleDefinition *aNeutron = G4Neutron::Neutron();
363 G4ParticleDefinition *aProton = G4Proton::Proton();
364 G4int ieab = static_cast<G4int>(availableEnergy*5.0/GeV);
365 const G4double supp[] = {0.,0.4,0.55,0.65,0.75,0.82,0.86,0.90,0.94,0.98};
366 G4double test, w0, wp, wt, wm;
367 if( (availableEnergy < 2.0*GeV) && (G4UniformRand() >= supp[ieab]) )
368 {
369 // suppress high multiplicity events at low momentum
370 // only one pion will be produced
371
372 nm = np = nz = 0;
373 if( targetParticle.GetDefinition() == aNeutron )
374 {
375 test = std::exp( std::min( expxu, std::max( expxl, -(1.0+b[1])*(1.0+b[1])/(2.0*c*c) ) ) );
376 w0 = test/2.0;
377 wm = test;
378 if( G4UniformRand() < w0/(w0+wm) )
379 nz = 1;
380 else
381 nm = 1;
382 } else { // target is a proton
383 test = std::exp( std::min( expxu, std::max( expxl, -(1.0+b[0])*(1.0+b[0])/(2.0*c*c) ) ) );
384 w0 = test;
385 wp = test/2.0;
386 test = std::exp( std::min( expxu, std::max( expxl, -(-1.0+b[0])*(-1.0+b[0])/(2.0*c*c) ) ) );
387 wm = test/2.0;
388 wt = w0+wp+wm;
389 wp += w0;
390 G4double ran = G4UniformRand();
391 if( ran < w0/wt )
392 nz = 1;
393 else if( ran < wp/wt )
394 np = 1;
395 else
396 nm = 1;
397 }
398 } else { // (availableEnergy >= 2.0*GeV) || (random number < supp[ieab])
399 G4double n, anpn;
400 GetNormalizationConstant( availableEnergy, n, anpn );
401 G4double ran = G4UniformRand();
402 G4double dum, excs = 0.0;
403 if( targetParticle.GetDefinition() == aProton )
404 {
405 counter = -1;
406 for( np=0; np<numSec/3 && ran>=excs; ++np )
407 {
408 for( nm=std::max(0,np-1); nm<=(np+1) && ran>=excs; ++nm )
409 {
410 for( nz=0; nz<numSec/3 && ran>=excs; ++nz )
411 {
412 if( ++counter < numMul )
413 {
414 nt = np+nm+nz;
415 if( nt > 0 )
416 {
417 test = std::exp( std::min( expxu, std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
418 dum = (pi/anpn)*nt*protmul[counter]*protnorm[nt-1]/(2.0*n*n);
419 if( std::fabs(dum) < 1.0 ) {
420 if( test >= 1.0e-10 )excs += dum*test;
421 } else {
422 excs += dum*test;
423 }
424 }
425 }
426 }
427 }
428 }
429 if( ran >= excs ) // 3 previous loops continued to the end
430 {
431 quasiElastic = true;
432 return;
433 }
434 np--; nm--; nz--;
435 } else { // target must be a neutron
436 counter = -1;
437 for( np=0; np<numSec/3 && ran>=excs; ++np )
438 {
439 for( nm=np; nm<=(np+2) && ran>=excs; ++nm )
440 {
441 for( nz=0; nz<numSec/3 && ran>=excs; ++nz )
442 {
443 if( ++counter < numMul )
444 {
445 nt = np+nm+nz;
446 if( (nt>=1) && (nt<=numSec) )
447 {
448 test = std::exp( std::min( expxu, std::max( expxl, -(pi/4.0)*(nt*nt)/(n*n) ) ) );
449 dum = (pi/anpn)*nt*neutmul[counter]*neutnorm[nt-1]/(2.0*n*n);
450 if( std::fabs(dum) < 1.0 ) {
451 if( test >= 1.0e-10 )excs += dum*test;
452 } else {
453 excs += dum*test;
454 }
455 }
456 }
457 }
458 }
459 }
460 if( ran >= excs ) // 3 previous loops continued to the end
461 {
462 quasiElastic = true;
463 return;
464 }
465 np--; nm--; nz--;
466 }
467 }
468 if( targetParticle.GetDefinition() == aProton )
469 {
470 switch( np-nm )
471 {
472 case 0:
473 if( G4UniformRand() < 0.33 )
474 {
475 currentParticle.SetDefinitionAndUpdateE( aProton );
476 targetParticle.SetDefinitionAndUpdateE( aNeutron );
477 incidentHasChanged = true;
478 targetHasChanged = true;
479 }
480 break;
481 case 1:
482 targetParticle.SetDefinitionAndUpdateE( aNeutron );
483 targetHasChanged = true;
484 break;
485 default:
486 currentParticle.SetDefinitionAndUpdateE( aProton );
487 incidentHasChanged = true;
488 break;
489 }
490 } else { // target must be a neutron
491 switch( np-nm )
492 {
493 case -1: // changed from +1 by JLC, 7Jul97
494 if( G4UniformRand() < 0.5 )
495 {
496 currentParticle.SetDefinitionAndUpdateE( aProton );
497 incidentHasChanged = true;
498 } else {
499 targetParticle.SetDefinitionAndUpdateE( aProton );
500 targetHasChanged = true;
501 }
502 break;
503 case 0:
504 break;
505 default:
506 currentParticle.SetDefinitionAndUpdateE( aProton );
507 targetParticle.SetDefinitionAndUpdateE( aProton );
508 incidentHasChanged = true;
509 targetHasChanged = true;
510 break;
511 }
512 }
513 SetUpPions( np, nm, nz, vec, vecLen );
514// DEBUG --> DumpFrames::DumpFrame(vec, vecLen);
515 return;
516 }
517
518 /* end of file */
519
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