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G4SynchrotronRadiation.cc
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27 // $Id$
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30 // GEANT 4 class implementation file
31 // CERN Geneva Switzerland
32 //
33 // History: first implementation,
34 // 21-5-98 V.Grichine
35 // 28-05-01, V.Ivanchenko minor changes to provide ANSI -wall compilation
36 // 04.03.05, V.Grichine: get local field interface
37 // 18-05-06 H. Burkhardt: Energy spectrum from function rather than table
38 //
39 //
40 //
41 //
43 
44 #include "G4SynchrotronRadiation.hh"
45 #include "G4PhysicalConstants.hh"
46 #include "G4SystemOfUnits.hh"
47 #include "G4UnitsTable.hh"
48 #include "G4EmProcessSubType.hh"
49 
51 //
52 // Constructor
53 //
54 
55 G4SynchrotronRadiation::G4SynchrotronRadiation(const G4String& processName,
56  G4ProcessType type):G4VDiscreteProcess (processName, type),
57  theGamma (G4Gamma::Gamma() ),
58  theElectron ( G4Electron::Electron() ),
59  thePositron ( G4Positron::Positron() )
60 {
61  G4TransportationManager* transportMgr =
62  G4TransportationManager::GetTransportationManager();
63 
64  fFieldPropagator = transportMgr->GetPropagatorInField();
65 
66  fLambdaConst = std::sqrt(3.0)*electron_mass_c2/
67  (2.5*fine_structure_const*eplus*c_light);
68  fEnergyConst = 1.5*c_light*c_light*eplus*hbar_Planck/electron_mass_c2 ;
69 
70  SetProcessSubType(fSynchrotronRadiation);
71  verboseLevel=1;
72 }
73 
75 //
76 // Destructor
77 //
78 
79 G4SynchrotronRadiation::~G4SynchrotronRadiation()
80 {}
81 
83 //
84 //
85 // Production of synchrotron X-ray photon
86 // GEANT4 internal units.
87 //
88 
89 
90 G4double
91 G4SynchrotronRadiation::GetMeanFreePath( const G4Track& trackData,
92  G4double,
93  G4ForceCondition* condition)
94 {
95  // gives the MeanFreePath in GEANT4 internal units
96  G4double MeanFreePath;
97 
98  const G4DynamicParticle* aDynamicParticle = trackData.GetDynamicParticle();
99 
100  *condition = NotForced;
101 
102  G4double gamma = aDynamicParticle->GetTotalEnergy()/
103  aDynamicParticle->GetMass();
104 
105  G4double particleCharge = aDynamicParticle->GetDefinition()->GetPDGCharge();
106 
107  if ( gamma < 1.0e3 ) MeanFreePath = DBL_MAX;
108  else
109  {
110 
111  G4ThreeVector FieldValue;
112  const G4Field* pField = 0;
113 
114  G4FieldManager* fieldMgr=0;
115  G4bool fieldExertsForce = false;
116 
117  if( (particleCharge != 0.0) )
118  {
119  fieldMgr = fFieldPropagator->FindAndSetFieldManager( trackData.GetVolume() );
120 
121  if ( fieldMgr != 0 )
122  {
123  // If the field manager has no field, there is no field !
124 
125  fieldExertsForce = ( fieldMgr->GetDetectorField() != 0 );
126  }
127  }
128  if ( fieldExertsForce )
129  {
130  pField = fieldMgr->GetDetectorField();
131  G4ThreeVector globPosition = trackData.GetPosition();
132 
133  G4double globPosVec[4], FieldValueVec[6];
134 
135  globPosVec[0] = globPosition.x();
136  globPosVec[1] = globPosition.y();
137  globPosVec[2] = globPosition.z();
138  globPosVec[3] = trackData.GetGlobalTime();
139 
140  pField->GetFieldValue( globPosVec, FieldValueVec );
141 
142  FieldValue = G4ThreeVector( FieldValueVec[0],
143  FieldValueVec[1],
144  FieldValueVec[2] );
145 
146 
147 
148  G4ThreeVector unitMomentum = aDynamicParticle->GetMomentumDirection();
149  G4ThreeVector unitMcrossB = FieldValue.cross(unitMomentum);
150  G4double perpB = unitMcrossB.mag();
151 
152  if( perpB > 0.0 ) MeanFreePath = fLambdaConst/perpB;
153  else MeanFreePath = DBL_MAX;
154 
155  static G4bool FirstTime=true;
156  if(verboseLevel > 0 && FirstTime)
157  {
158  G4cout << "G4SynchrotronRadiation::GetMeanFreePath :" << '\n'
159  << " MeanFreePath = " << G4BestUnit(MeanFreePath, "Length")
160  << G4endl;
161  if(verboseLevel > 1)
162  {
163  G4ThreeVector pvec=aDynamicParticle->GetMomentum();
164  G4double Btot=FieldValue.getR();
165  G4double ptot=pvec.getR();
166  G4double rho= ptot / (MeV * c_light * Btot ); // full bending radius
167  G4double Theta=unitMomentum.theta(FieldValue); // angle between particle and field
168  G4cout
169  << " B = " << Btot/tesla << " Tesla"
170  << " perpB = " << perpB/tesla << " Tesla"
171  << " Theta = " << Theta << " std::sin(Theta)=" << std::sin(Theta) << '\n'
172  << " ptot = " << G4BestUnit(ptot,"Energy")
173  << " rho = " << G4BestUnit(rho,"Length")
174  << G4endl;
175  }
176  FirstTime=false;
177  }
178  }
179  else MeanFreePath = DBL_MAX;
180 
181 
182  }
183 
184  return MeanFreePath;
185 }
186 
188 //
189 //
190 
191 G4VParticleChange*
192 G4SynchrotronRadiation::PostStepDoIt(const G4Track& trackData,
193  const G4Step& stepData )
194 
195 {
196  aParticleChange.Initialize(trackData);
197 
198  const G4DynamicParticle* aDynamicParticle=trackData.GetDynamicParticle();
199 
200  G4double gamma = aDynamicParticle->GetTotalEnergy()/
201  (aDynamicParticle->GetMass() );
202 
203  if(gamma <= 1.0e3 )
204  {
205  return G4VDiscreteProcess::PostStepDoIt(trackData,stepData);
206  }
207  G4double particleCharge = aDynamicParticle->GetDefinition()->GetPDGCharge();
208 
209  G4ThreeVector FieldValue;
210  const G4Field* pField = 0;
211 
212  G4FieldManager* fieldMgr=0;
213  G4bool fieldExertsForce = false;
214 
215  if( (particleCharge != 0.0) )
216  {
217  fieldMgr = fFieldPropagator->FindAndSetFieldManager( trackData.GetVolume() );
218  if ( fieldMgr != 0 )
219  {
220  // If the field manager has no field, there is no field !
221 
222  fieldExertsForce = ( fieldMgr->GetDetectorField() != 0 );
223  }
224  }
225  if ( fieldExertsForce )
226  {
227  pField = fieldMgr->GetDetectorField();
228  G4ThreeVector globPosition = trackData.GetPosition();
229  G4double globPosVec[4], FieldValueVec[6];
230  globPosVec[0] = globPosition.x();
231  globPosVec[1] = globPosition.y();
232  globPosVec[2] = globPosition.z();
233  globPosVec[3] = trackData.GetGlobalTime();
234 
235  pField->GetFieldValue( globPosVec, FieldValueVec );
236  FieldValue = G4ThreeVector( FieldValueVec[0],
237  FieldValueVec[1],
238  FieldValueVec[2] );
239 
240  G4ThreeVector unitMomentum = aDynamicParticle->GetMomentumDirection();
241  G4ThreeVector unitMcrossB = FieldValue.cross(unitMomentum);
242  G4double perpB = unitMcrossB.mag();
243  if(perpB > 0.0)
244  {
245  // M-C of synchrotron photon energy
246 
247  G4double energyOfSR = GetRandomEnergySR(gamma,perpB);
248 
249  // check against insufficient energy
250 
251  if( energyOfSR <= 0.0 )
252  {
253  return G4VDiscreteProcess::PostStepDoIt(trackData,stepData);
254  }
255  G4double kineticEnergy = aDynamicParticle->GetKineticEnergy();
256  G4ParticleMomentum
257  particleDirection = aDynamicParticle->GetMomentumDirection();
258 
259  // M-C of its direction, simplified dipole boosted approach
260 
261  // G4double Teta, fteta; // = G4UniformRand()/gamma; // Very roughly
262 
263  G4double cosTheta, sinTheta, fcos, beta;
264 
265  do
266  {
267  cosTheta = 1. - 2.*G4UniformRand();
268  fcos = (1 + cosTheta*cosTheta)*0.5;
269  }
270  while( fcos < G4UniformRand() );
271 
272  beta = std::sqrt(1. - 1./(gamma*gamma));
273 
274  cosTheta = (cosTheta + beta)/(1. + beta*cosTheta);
275 
276  if( cosTheta > 1. ) cosTheta = 1.;
277  if( cosTheta < -1. ) cosTheta = -1.;
278 
279  sinTheta = std::sqrt(1. - cosTheta*cosTheta );
280 
281  G4double Phi = twopi * G4UniformRand();
282 
283  G4double dirx = sinTheta*std::cos(Phi) ,
284  diry = sinTheta*std::sin(Phi) ,
285  dirz = cosTheta;
286 
287  G4ThreeVector gammaDirection ( dirx, diry, dirz);
288  gammaDirection.rotateUz(particleDirection);
289 
290  // polarization of new gamma
291 
292  // G4double sx = std::cos(Teta)*std::cos(Phi);
293  // G4double sy = std::cos(Teta)*std::sin(Phi);
294  // G4double sz = -std::sin(Teta);
295 
296  G4ThreeVector gammaPolarization = FieldValue.cross(gammaDirection);
297  gammaPolarization = gammaPolarization.unit();
298 
299  // (sx, sy, sz);
300  // gammaPolarization.rotateUz(particleDirection);
301 
302  // create G4DynamicParticle object for the SR photon
303 
304  G4DynamicParticle* aGamma= new G4DynamicParticle ( theGamma,
305  gammaDirection,
306  energyOfSR );
307  aGamma->SetPolarization( gammaPolarization.x(),
308  gammaPolarization.y(),
309  gammaPolarization.z() );
310 
311 
312  aParticleChange.SetNumberOfSecondaries(1);
313  aParticleChange.AddSecondary(aGamma);
314 
315  // Update the incident particle
316 
317  G4double newKinEnergy = kineticEnergy - energyOfSR;
318  aParticleChange.ProposeLocalEnergyDeposit (0.);
319 
320  if (newKinEnergy > 0.)
321  {
322  aParticleChange.ProposeMomentumDirection( particleDirection );
323  aParticleChange.ProposeEnergy( newKinEnergy );
324  }
325  else
326  {
327  aParticleChange.ProposeEnergy( 0. );
328  }
329  }
330  }
331  return G4VDiscreteProcess::PostStepDoIt(trackData,stepData);
332 }
333 
334 
336 //
337 //
338 
339 G4double G4SynchrotronRadiation::InvSynFracInt(G4double x)
340 // direct generation
341 {
342  // from 0 to 0.7
343  const G4double aa1=0 ,aa2=0.7;
344  const G4int ncheb1=27;
345  static const G4double cheb1[] =
346  { 1.22371665676046468821,0.108956475422163837267,0.0383328524358594396134,0.00759138369340257753721,
347  0.00205712048644963340914,0.000497810783280019308661,0.000130743691810302187818,0.0000338168760220395409734,
348  8.97049680900520817728e-6,2.38685472794452241466e-6,6.41923109149104165049e-7,1.73549898982749277843e-7,
349  4.72145949240790029153e-8,1.29039866111999149636e-8,3.5422080787089834182e-9,9.7594757336403784905e-10,
350  2.6979510184976065731e-10,7.480422622550977077e-11,2.079598176402699913e-11,5.79533622220841193e-12,
351  1.61856011449276096e-12,4.529450993473807e-13,1.2698603951096606e-13,3.566117394511206e-14,1.00301587494091e-14,
352  2.82515346447219e-15,7.9680747949792e-16};
353  // from 0.7 to 0.9132260271183847
354  const G4double aa3=0.9132260271183847;
355  const G4int ncheb2=27;
356  static const G4double cheb2[] =
357  { 1.1139496701107756,0.3523967429328067,0.0713849171926623,0.01475818043595387,0.003381255637322462,
358  0.0008228057599452224,0.00020785506681254216,0.00005390169253706556,0.000014250571923902464,3.823880733161044e-6,
359  1.0381966089136036e-6,2.8457557457837253e-7,7.86223332179956e-8,2.1866609342508474e-8,6.116186259857143e-9,
360  1.7191233618437565e-9,4.852755117740807e-10,1.3749966961763457e-10,3.908961987062447e-11,1.1146253766895824e-11,
361  3.1868887323415814e-12,9.134319791300977e-13,2.6211077371181566e-13,7.588643377757906e-14,2.1528376972619e-14,
362  6.030906040404772e-15,1.9549163926819867e-15};
363  // Chebyshev with exp/log scale
364  // a = -Log[1 - SynFracInt[1]]; b = -Log[1 - SynFracInt[7]];
365  const G4double aa4=2.4444485538746025480,aa5=9.3830728608909477079;
366  const G4int ncheb3=28;
367  static const G4double cheb3[] =
368  { 1.2292683840435586977,0.160353449247864455879,-0.0353559911947559448721,0.00776901561223573936985,
369  -0.00165886451971685133259,0.000335719118906954279467,-0.0000617184951079161143187,9.23534039743246708256e-6,
370  -6.06747198795168022842e-7,-3.07934045961999778094e-7,1.98818772614682367781e-7,-8.13909971567720135413e-8,
371  2.84298174969641838618e-8,-9.12829766621316063548e-9,2.77713868004820551077e-9,-8.13032767247834023165e-10,
372  2.31128525568385247392e-10,-6.41796873254200220876e-11,1.74815310473323361543e-11,-4.68653536933392363045e-12,
373  1.24016595805520752748e-12,-3.24839432979935522159e-13,8.44601465226513952994e-14,-2.18647276044246803998e-14,
374  5.65407548745690689978e-15,-1.46553625917463067508e-15,3.82059606377570462276e-16,-1.00457896653436912508e-16};
375  const G4double aa6=33.122936966163038145;
376  const G4int ncheb4=27;
377  static const G4double cheb4[] =
378  {1.69342658227676741765,0.0742766400841232319225,-0.019337880608635717358,0.00516065527473364110491,
379  -0.00139342012990307729473,0.000378549864052022522193,-0.000103167085583785340215,0.0000281543441271412178337,
380  -7.68409742018258198651e-6,2.09543221890204537392e-6,-5.70493140367526282946e-7,1.54961164548564906446e-7,
381  -4.19665599629607704794e-8,1.13239680054166507038e-8,-3.04223563379021441863e-9,8.13073745977562957997e-10,
382  -2.15969415476814981374e-10,5.69472105972525594811e-11,-1.48844799572430829499e-11,3.84901514438304484973e-12,
383  -9.82222575944247161834e-13,2.46468329208292208183e-13,-6.04953826265982691612e-14,1.44055805710671611984e-14,
384  -3.28200813577388740722e-15,6.96566359173765367675e-16,-1.294122794852896275e-16};
385 
386  if(x<aa2) return x*x*x*Chebyshev(aa1,aa2,cheb1,ncheb1,x);
387  else if(x<aa3) return Chebyshev(aa2,aa3,cheb2,ncheb2,x);
388  else if(x<1-0.0000841363)
389  { G4double y=-std::log(1-x);
390  return y*Chebyshev(aa4,aa5,cheb3,ncheb3,y);
391  }
392  else
393  { G4double y=-std::log(1-x);
394  return y*Chebyshev(aa5,aa6,cheb4,ncheb4,y);
395  }
396 }
397 
398 G4double G4SynchrotronRadiation::GetRandomEnergySR(G4double gamma, G4double perpB)
399 {
400 
401  G4double Ecr=fEnergyConst*gamma*gamma*perpB;
402 
403  static G4bool FirstTime=true;
404  if(verboseLevel > 0 && FirstTime)
405  { G4double Emean=8./(15.*std::sqrt(3.))*Ecr; // mean photon energy
406  G4double E_rms=std::sqrt(211./675.)*Ecr; // rms of photon energy distribution
407  G4int prec = G4cout.precision();
408  G4cout << "G4SynchrotronRadiation::GetRandomEnergySR :" << '\n' << std::setprecision(4)
409  << " Ecr = " << G4BestUnit(Ecr,"Energy") << '\n'
410  << " Emean = " << G4BestUnit(Emean,"Energy") << '\n'
411  << " E_rms = " << G4BestUnit(E_rms,"Energy") << G4endl;
412  FirstTime=false;
413  G4cout.precision(prec);
414  }
415 
416  G4double energySR=Ecr*InvSynFracInt(G4UniformRand());
417  return energySR;
418 }
419 
420 
421 void G4SynchrotronRadiation::BuildPhysicsTable(const G4ParticleDefinition& part)
422 {
423  if(0 < verboseLevel && &part==theElectron ) PrintInfoDefinition();
424 }
425 
426 void G4SynchrotronRadiation::PrintInfoDefinition() // not yet called, usually called from BuildPhysicsTable
427 {
428  G4String comments ="Incoherent Synchrotron Radiation\n";
429  G4cout << G4endl << GetProcessName() << ": " << comments
430  << " good description for long magnets at all energies" << G4endl;
431 }
432 
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