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25 //
26 // --------------------------------------------------------------
27 // GEANT 4 class implementation file
28 //
29 // History: first implementation,
30 // 21-5-98 V.Grichine
31 // 28-05-01, V.Ivanchenko minor changes to provide ANSI -wall compilation
32 // 04.03.05, V.Grichine: get local field interface
33 // 18-05-06 H. Burkhardt: Energy spectrum from function rather than table
34 //
35 ///////////////////////////////////////////////////////////////////////////
36
37 #include "G4SynchrotronRadiation.hh"
38
39 #include "G4DipBustGenerator.hh"
40 #include "G4Electron.hh"
41 #include "G4EmProcessSubType.hh"
42 #include "G4Log.hh"
43 #include "G4LossTableManager.hh"
44 #include "G4Gamma.hh"
45 #include "G4PhysicalConstants.hh"
46 #include "G4PropagatorInField.hh"
47 #include "G4SystemOfUnits.hh"
48 #include "G4TransportationManager.hh"
49 #include "G4UnitsTable.hh"
50 #include "G4PhysicsModelCatalog.hh"
51
52 ///////////////////////////////////////////////////////////////////////
53 // Constructor
54 G4SynchrotronRadiation::G4SynchrotronRadiation(const G4String& processName,
55 G4ProcessType type)
56 : G4VDiscreteProcess(processName, type)
57 , theGamma(G4Gamma::Gamma())
58 {
59 G4TransportationManager* transportMgr =
60 G4TransportationManager::GetTransportationManager();
61
62 fFieldPropagator = transportMgr->GetPropagatorInField();
63
64 secID = G4PhysicsModelCatalog::GetModelID("model_SynRad");
65 SetProcessSubType(fSynchrotronRadiation);
66 verboseLevel = 1;
67 FirstTime = true;
68 FirstTime1 = true;
69 genAngle = nullptr;
70 SetAngularGenerator(new G4DipBustGenerator());
71 theManager = G4LossTableManager::Instance();
72 theManager->Register(this);
73 }
74
75 /////////////////////////////////////////////////////////////////////////
76 // Destructor
77 G4SynchrotronRadiation::~G4SynchrotronRadiation()
78 {
79 delete genAngle;
80 theManager->DeRegister(this);
81 }
82
83 /////////////////////////////// METHODS /////////////////////////////////
84
85 void G4SynchrotronRadiation::SetAngularGenerator(G4VEmAngularDistribution* p)
86 {
87 if(p != genAngle)
88 {
89 delete genAngle;
90 genAngle = p;
91 }
92 }
93
94 G4bool G4SynchrotronRadiation::IsApplicable(
95 const G4ParticleDefinition& particle)
96 {
97 return (particle.GetPDGCharge() != 0.0 && !particle.IsShortLived());
98 }
99
100 /////////////////////////////////////////////////////////////////////////
101 // Production of synchrotron X-ray photon
102 // Geant4 internal units.
103 G4double G4SynchrotronRadiation::GetMeanFreePath(const G4Track& trackData,
104 G4double,
105 G4ForceCondition* condition)
106 {
107 // gives the MeanFreePath in Geant4 internal units
108 G4double MeanFreePath = DBL_MAX;
109
110 const G4DynamicParticle* aDynamicParticle = trackData.GetDynamicParticle();
111
112 *condition = NotForced;
113
114 G4double gamma =
115 aDynamicParticle->GetTotalEnergy() / aDynamicParticle->GetMass();
116
117 G4double particleCharge = aDynamicParticle->GetDefinition()->GetPDGCharge();
118
119 if(gamma < 1.0e3 || 0.0 == particleCharge)
120 {
121 MeanFreePath = DBL_MAX;
122 }
123 else
124 {
125 G4ThreeVector FieldValue;
126 const G4Field* pField = nullptr;
127 G4bool fieldExertsForce = false;
128
129 G4FieldManager* fieldMgr =
130 fFieldPropagator->FindAndSetFieldManager(trackData.GetVolume());
131
132 if(fieldMgr != nullptr)
133 {
134 // If the field manager has no field, there is no field !
135 fieldExertsForce = (fieldMgr->GetDetectorField() != nullptr);
136 }
137
138 if(fieldExertsForce)
139 {
140 pField = fieldMgr->GetDetectorField();
141 G4ThreeVector globPosition = trackData.GetPosition();
142
143 G4double globPosVec[4], FieldValueVec[6];
144
145 globPosVec[0] = globPosition.x();
146 globPosVec[1] = globPosition.y();
147 globPosVec[2] = globPosition.z();
148 globPosVec[3] = trackData.GetGlobalTime();
149
150 pField->GetFieldValue(globPosVec, FieldValueVec);
151
152 FieldValue =
153 G4ThreeVector(FieldValueVec[0], FieldValueVec[1], FieldValueVec[2]);
154
155 G4ThreeVector unitMomentum = aDynamicParticle->GetMomentumDirection();
156 G4ThreeVector unitMcrossB = FieldValue.cross(unitMomentum);
157 G4double perpB = unitMcrossB.mag();
158
159 static const G4double fLambdaConst =
160 std::sqrt(3.0) * eplus / (2.5 * fine_structure_const * c_light);
161
162 if(perpB > 0.0)
163 {
164 MeanFreePath = fLambdaConst *
165 aDynamicParticle->GetDefinition()->GetPDGMass() /
166 (perpB * particleCharge * particleCharge);
167 }
168 if(verboseLevel > 0 && FirstTime)
169 {
170 G4cout << "G4SynchrotronRadiation::GetMeanFreePath "
171 << " for particle "
172 << aDynamicParticle->GetDefinition()->GetParticleName() << ":"
173 << '\n'
174 << " MeanFreePath = " << G4BestUnit(MeanFreePath, "Length")
175 << G4endl;
176 if(verboseLevel > 1)
177 {
178 G4ThreeVector pvec = aDynamicParticle->GetMomentum();
179 G4double Btot = FieldValue.getR();
180 G4double ptot = pvec.getR();
181 G4double rho = ptot / (MeV * c_light * Btot);
182 // full bending radius
183 G4double Theta = unitMomentum.theta(FieldValue);
184 // angle between particle and field
185 G4cout << " B = " << Btot / tesla << " Tesla"
186 << " perpB = " << perpB / tesla << " Tesla"
187 << " Theta = " << Theta
188 << " std::sin(Theta)=" << std::sin(Theta) << '\n'
189 << " ptot = " << G4BestUnit(ptot, "Energy")
190 << " rho = " << G4BestUnit(rho, "Length") << G4endl;
191 }
192 FirstTime = false;
193 }
194 }
195 }
196 return MeanFreePath;
197 }
198
199 ///////////////////////////////////////////////////////////////////////////////
200 G4VParticleChange* G4SynchrotronRadiation::PostStepDoIt(
201 const G4Track& trackData, const G4Step& stepData)
202
203 {
204 aParticleChange.Initialize(trackData);
205
206 const G4DynamicParticle* aDynamicParticle = trackData.GetDynamicParticle();
207
208 G4double gamma = aDynamicParticle->GetTotalEnergy() /
209 (aDynamicParticle->GetDefinition()->GetPDGMass());
210
211 G4double particleCharge = aDynamicParticle->GetDefinition()->GetPDGCharge();
212 if(gamma <= 1.0e3 || 0.0 == particleCharge)
213 {
214 return G4VDiscreteProcess::PostStepDoIt(trackData, stepData);
215 }
216
217 G4ThreeVector FieldValue;
218 const G4Field* pField = nullptr;
219
220 G4bool fieldExertsForce = false;
221 G4FieldManager* fieldMgr =
222 fFieldPropagator->FindAndSetFieldManager(trackData.GetVolume());
223
224 if(fieldMgr != nullptr)
225 {
226 // If the field manager has no field, there is no field !
227 fieldExertsForce = (fieldMgr->GetDetectorField() != nullptr);
228 }
229
230 if(fieldExertsForce)
231 {
232 pField = fieldMgr->GetDetectorField();
233 G4ThreeVector globPosition = trackData.GetPosition();
234 G4double globPosVec[4], FieldValueVec[6];
235 globPosVec[0] = globPosition.x();
236 globPosVec[1] = globPosition.y();
237 globPosVec[2] = globPosition.z();
238 globPosVec[3] = trackData.GetGlobalTime();
239
240 pField->GetFieldValue(globPosVec, FieldValueVec);
241 FieldValue =
242 G4ThreeVector(FieldValueVec[0], FieldValueVec[1], FieldValueVec[2]);
243
244 G4ThreeVector unitMomentum = aDynamicParticle->GetMomentumDirection();
245 G4ThreeVector unitMcrossB = FieldValue.cross(unitMomentum);
246 G4double perpB = unitMcrossB.mag();
247 if(perpB > 0.0)
248 {
249 // M-C of synchrotron photon energy
250 G4double energyOfSR = GetRandomEnergySR(
251 gamma, perpB, aDynamicParticle->GetDefinition()->GetPDGMass());
252
253 // check against insufficient energy
254 if(energyOfSR <= 0.0)
255 {
256 return G4VDiscreteProcess::PostStepDoIt(trackData, stepData);
257 }
258 G4double kineticEnergy = aDynamicParticle->GetKineticEnergy();
259 G4ThreeVector gammaDirection =
260 genAngle->SampleDirection(aDynamicParticle, energyOfSR, 1, nullptr);
261
262 G4ThreeVector gammaPolarization = FieldValue.cross(gammaDirection);
263 gammaPolarization = gammaPolarization.unit();
264
265 // create G4DynamicParticle object for the SR photon
266 auto aGamma =
267 new G4DynamicParticle(theGamma, gammaDirection, energyOfSR);
268 aGamma->SetPolarization(gammaPolarization.x(), gammaPolarization.y(),
269 gammaPolarization.z());
270
271 aParticleChange.SetNumberOfSecondaries(1);
272
273 // Update the incident particle
274 G4double newKinEnergy = kineticEnergy - energyOfSR;
275
276 if(newKinEnergy > 0.)
277 {
278 aParticleChange.ProposeEnergy(newKinEnergy);
279 }
280 else
281 {
282 aParticleChange.ProposeEnergy(0.);
283 }
284
285 // Create the G4Track
286 G4Track* aSecondaryTrack = new G4Track(aGamma, trackData.GetGlobalTime(), trackData.GetPosition());
287 aSecondaryTrack->SetTouchableHandle(stepData.GetPostStepPoint()->GetTouchableHandle());
288 aSecondaryTrack->SetParentID(trackData.GetTrackID());
289 aSecondaryTrack->SetCreatorModelID(secID);
290 aParticleChange.AddSecondary(aSecondaryTrack);
291
292 }
293 }
294 return G4VDiscreteProcess::PostStepDoIt(trackData, stepData);
295 }
296
297 ///////////////////////////////////////////////////////////////////////////////
298 G4double G4SynchrotronRadiation::InvSynFracInt(G4double x)
299 // direct generation
300 {
301 // from 0 to 0.7
302 static constexpr G4double aa1 = 0;
303 static constexpr G4double aa2 = 0.7;
304 static constexpr G4int ncheb1 = 27;
305 static constexpr G4double cheb1[ncheb1] = {
306 1.22371665676046468821, 0.108956475422163837267,
307 0.0383328524358594396134, 0.00759138369340257753721,
308 0.00205712048644963340914, 0.000497810783280019308661,
309 0.000130743691810302187818, 0.0000338168760220395409734,
310 8.97049680900520817728e-6, 2.38685472794452241466e-6,
311 6.41923109149104165049e-7, 1.73549898982749277843e-7,
312 4.72145949240790029153e-8, 1.29039866111999149636e-8,
313 3.5422080787089834182e-9, 9.7594757336403784905e-10,
314 2.6979510184976065731e-10, 7.480422622550977077e-11,
315 2.079598176402699913e-11, 5.79533622220841193e-12,
316 1.61856011449276096e-12, 4.529450993473807e-13,
317 1.2698603951096606e-13, 3.566117394511206e-14,
318 1.00301587494091e-14, 2.82515346447219e-15,
319 7.9680747949792e-16
320 };
321 // from 0.7 to 0.9132260271183847
322 static constexpr G4double aa3 = 0.9132260271183847;
323 static constexpr G4int ncheb2 = 27;
324 static constexpr G4double cheb2[ncheb2] = {
325 1.1139496701107756, 0.3523967429328067, 0.0713849171926623,
326 0.01475818043595387, 0.003381255637322462, 0.0008228057599452224,
327 0.00020785506681254216, 0.00005390169253706556, 0.000014250571923902464,
328 3.823880733161044e-6, 1.0381966089136036e-6, 2.8457557457837253e-7,
329 7.86223332179956e-8, 2.1866609342508474e-8, 6.116186259857143e-9,
330 1.7191233618437565e-9, 4.852755117740807e-10, 1.3749966961763457e-10,
331 3.908961987062447e-11, 1.1146253766895824e-11, 3.1868887323415814e-12,
332 9.134319791300977e-13, 2.6211077371181566e-13, 7.588643377757906e-14,
333 2.1528376972619e-14, 6.030906040404772e-15, 1.9549163926819867e-15
334 };
335 // Chebyshev with exp/log scale
336 // a = -Log[1 - SynFracInt[1]]; b = -Log[1 - SynFracInt[7]];
337 static constexpr G4double aa4 = 2.4444485538746025480;
338 static constexpr G4double aa5 = 9.3830728608909477079;
339 static constexpr G4int ncheb3 = 28;
340 static constexpr G4double cheb3[ncheb3] = {
341 1.2292683840435586977, 0.160353449247864455879,
342 -0.0353559911947559448721, 0.00776901561223573936985,
343 -0.00165886451971685133259, 0.000335719118906954279467,
344 -0.0000617184951079161143187, 9.23534039743246708256e-6,
345 -6.06747198795168022842e-7, -3.07934045961999778094e-7,
346 1.98818772614682367781e-7, -8.13909971567720135413e-8,
347 2.84298174969641838618e-8, -9.12829766621316063548e-9,
348 2.77713868004820551077e-9, -8.13032767247834023165e-10,
349 2.31128525568385247392e-10, -6.41796873254200220876e-11,
350 1.74815310473323361543e-11, -4.68653536933392363045e-12,
351 1.24016595805520752748e-12, -3.24839432979935522159e-13,
352 8.44601465226513952994e-14, -2.18647276044246803998e-14,
353 5.65407548745690689978e-15, -1.46553625917463067508e-15,
354 3.82059606377570462276e-16, -1.00457896653436912508e-16
355 };
356 static constexpr G4double aa6 = 33.122936966163038145;
357 static constexpr G4int ncheb4 = 27;
358 static constexpr G4double cheb4[ncheb4] = {
359 1.69342658227676741765, 0.0742766400841232319225,
360 -0.019337880608635717358, 0.00516065527473364110491,
361 -0.00139342012990307729473, 0.000378549864052022522193,
362 -0.000103167085583785340215, 0.0000281543441271412178337,
363 -7.68409742018258198651e-6, 2.09543221890204537392e-6,
364 -5.70493140367526282946e-7, 1.54961164548564906446e-7,
365 -4.19665599629607704794e-8, 1.13239680054166507038e-8,
366 -3.04223563379021441863e-9, 8.13073745977562957997e-10,
367 -2.15969415476814981374e-10, 5.69472105972525594811e-11,
368 -1.48844799572430829499e-11, 3.84901514438304484973e-12,
369 -9.82222575944247161834e-13, 2.46468329208292208183e-13,
370 -6.04953826265982691612e-14, 1.44055805710671611984e-14,
371 -3.28200813577388740722e-15, 6.96566359173765367675e-16,
372 -1.294122794852896275e-16
373 };
374
375 if(x < aa2)
376 return x * x * x * Chebyshev(aa1, aa2, cheb1, ncheb1, x);
377 else if(x < aa3)
378 return Chebyshev(aa2, aa3, cheb2, ncheb2, x);
379 else if(x < 1 - 0.0000841363)
380 {
381 G4double y = -G4Log(1 - x);
382 return y * Chebyshev(aa4, aa5, cheb3, ncheb3, y);
383 }
384 else
385 {
386 G4double y = -G4Log(1 - x);
387 return y * Chebyshev(aa5, aa6, cheb4, ncheb4, y);
388 }
389 }
390
391 G4double G4SynchrotronRadiation::GetRandomEnergySR(G4double gamma,
392 G4double perpB,
393 G4double mass_c2)
394 {
395 static const G4double fEnergyConst =
396 1.5 * c_light * c_light * eplus * hbar_Planck;
397 G4double Ecr = fEnergyConst * gamma * gamma * perpB / mass_c2;
398
399 if(verboseLevel > 0 && FirstTime1)
400 {
401 // mean and rms of photon energy
402 G4double Emean = 8. / (15. * std::sqrt(3.)) * Ecr;
403 G4double E_rms = std::sqrt(211. / 675.) * Ecr;
404 G4long prec = G4cout.precision();
405 G4cout << "G4SynchrotronRadiation::GetRandomEnergySR :" << '\n'
406 << std::setprecision(4) << " Ecr = " << G4BestUnit(Ecr, "Energy")
407 << '\n'
408 << " Emean = " << G4BestUnit(Emean, "Energy") << '\n'
409 << " E_rms = " << G4BestUnit(E_rms, "Energy") << G4endl;
410 FirstTime1 = false;
411 G4cout.precision(prec);
412 }
413
414 G4double energySR = Ecr * InvSynFracInt(G4UniformRand());
415 return energySR;
416 }
417
418 ///////////////////////////////////////////////////////////////////////////////
419 void G4SynchrotronRadiation::BuildPhysicsTable(const G4ParticleDefinition& part)
420 {
421 if(0 < verboseLevel && &part == G4Electron::Electron())
422 ProcessDescription(G4cout);
423 // same for all particles, print only for one (electron)
424 }
425
426 ///////////////////////////////////////////////////////////////////////////////
427 void G4SynchrotronRadiation::ProcessDescription(std::ostream& out) const
428 {
429 out << GetProcessName()
430 << ": Incoherent Synchrotron Radiation\n"
431 "Good description for long magnets at all energies.\n";
432 }
433