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source: trunk/source/processes/electromagnetic/xrays/src/G4Cerenkov.cc @ 961

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26	//
27	// $Id: G4Cerenkov.cc,v 1.26 2008/11/14 20:16:51 gum Exp $
28	// GEANT4 tag $Name: geant4-09-02-ref-02 $
29	//
30	////////////////////////////////////////////////////////////////////////
31	// Cerenkov Radiation Class Implementation
32	////////////////////////////////////////////////////////////////////////
33	//
34	// File: G4Cerenkov.cc
35	// Description: Discrete Process -- Generation of Cerenkov Photons
36	// Version: 2.1
37	// Created: 1996-02-21
38	// Author: Juliet Armstrong
39	// Updated: 2007-09-30 by Peter Gumplinger
40	// > change inheritance to G4VDiscreteProcess
41	// GetContinuousStepLimit -> GetMeanFreePath (StronglyForced)
42	// AlongStepDoIt -> PostStepDoIt
43	// 2005-08-17 by Peter Gumplinger
44	// > change variable name MeanNumPhotons -> MeanNumberOfPhotons
45	// 2005-07-28 by Peter Gumplinger
46	// > add G4ProcessType to constructor
47	// 2001-09-17, migration of Materials to pure STL (mma)
48	// 2000-11-12 by Peter Gumplinger
49	// > add check on CerenkovAngleIntegrals->IsFilledVectorExist()
50	// in method GetAverageNumberOfPhotons
51	// > and a test for MeanNumberOfPhotons <= 0.0 in DoIt
52	// 2000-09-18 by Peter Gumplinger
53	// > change: aSecondaryPosition=x0+rand*aStep.GetDeltaPosition();
54	// aSecondaryTrack->SetTouchable(0);
55	// 1999-10-29 by Peter Gumplinger
56	// > change: == into <= in GetContinuousStepLimit
57	// 1997-08-08 by Peter Gumplinger
58	// > add protection against /0
59	// > G4MaterialPropertiesTable; new physics/tracking scheme
60	//
61	// mail: gum@triumf.ca
62	//
63	////////////////////////////////////////////////////////////////////////
64
65	#include "G4ios.hh"
66	#include "G4Poisson.hh"
67	#include "G4EmProcessSubType.hh"
68
69	#include "G4LossTableManager.hh"
70	#include "G4MaterialCutsCouple.hh"
71	#include "G4ParticleDefinition.hh"
72
73	#include "G4Cerenkov.hh"
74
75	using namespace std;
76
77	/////////////////////////
78	// Class Implementation
79	/////////////////////////
80
81	//////////////
82	// Operators
83	//////////////
84
85	// G4Cerenkov::operator=(const G4Cerenkov &right)
86	// {
87	// }
88
89	/////////////////
90	// Constructors
91	/////////////////
92
93	G4Cerenkov::G4Cerenkov(const G4String& processName, G4ProcessType type)
94	: G4VProcess(processName, type)
95	{
96	G4cout << "G4Cerenkov::G4Cerenkov constructor" << G4endl;
97	G4cout << "NOTE: this is now a G4VProcess!" << G4endl;
98	G4cout << "Required change in UserPhysicsList: " << G4endl;
99	G4cout << "change: pmanager->AddContinuousProcess(theCerenkovProcess);" << G4endl;
100	G4cout << "to: pmanager->AddProcess(theCerenkovProcess);" << G4endl;
101	G4cout << " pmanager->SetProcessOrdering(theCerenkovProcess,idxPostStep);" << G4endl;
102
103	SetProcessSubType(fCerenkov);
104
105	fTrackSecondariesFirst = false;
106	fMaxBetaChange = 0.;
107	fMaxPhotons = 0;
108
109	thePhysicsTable = NULL;
110
111	if (verboseLevel>0) {
112	G4cout << GetProcessName() << " is created " << G4endl;
113	}
114
115	BuildThePhysicsTable();
116	}
117
118	// G4Cerenkov::G4Cerenkov(const G4Cerenkov &right)
119	// {
120	// }
121
122	////////////////
123	// Destructors
124	////////////////
125
126	G4Cerenkov::~G4Cerenkov()
127	{
128	if (thePhysicsTable != NULL) {
129	thePhysicsTable->clearAndDestroy();
130	delete thePhysicsTable;
131	}
132	}
133
134	////////////
135	// Methods
136	////////////
137
138	// PostStepDoIt
139	// -------------
140	//
141	G4VParticleChange*
142	G4Cerenkov::PostStepDoIt(const G4Track& aTrack, const G4Step& aStep)
143
144	// This routine is called for each tracking Step of a charged particle
145	// in a radiator. A Poisson-distributed number of photons is generated
146	// according to the Cerenkov formula, distributed evenly along the track
147	// segment and uniformly azimuth w.r.t. the particle direction. The
148	// parameters are then transformed into the Master Reference System, and
149	// they are added to the particle change.
150
151	{
152	//////////////////////////////////////////////////////
153	// Should we ensure that the material is dispersive?
154	//////////////////////////////////////////////////////
155
156	aParticleChange.Initialize(aTrack);
157
158	const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle();
159	const G4Material* aMaterial = aTrack.GetMaterial();
160
161	G4StepPoint* pPreStepPoint = aStep.GetPreStepPoint();
162	G4StepPoint* pPostStepPoint = aStep.GetPostStepPoint();
163
164	G4ThreeVector x0 = pPreStepPoint->GetPosition();
165	G4ThreeVector p0 = aStep.GetDeltaPosition().unit();
166	G4double t0 = pPreStepPoint->GetGlobalTime();
167
168	G4MaterialPropertiesTable* aMaterialPropertiesTable =
169	aMaterial->GetMaterialPropertiesTable();
170	if (!aMaterialPropertiesTable) return pParticleChange;
171
172	const G4MaterialPropertyVector* Rindex =
173	aMaterialPropertiesTable->GetProperty("RINDEX");
174	if (!Rindex) return pParticleChange;
175
176	// particle charge
177	const G4double charge = aParticle->GetDefinition()->GetPDGCharge();
178
179	// particle beta
180	const G4double beta = (pPreStepPoint ->GetBeta() +
181	pPostStepPoint->GetBeta())/2.;
182
183	G4double MeanNumberOfPhotons =
184	GetAverageNumberOfPhotons(charge,beta,aMaterial,Rindex);
185
186	if (MeanNumberOfPhotons <= 0.0) {
187
188	// return unchanged particle and no secondaries
189
190	aParticleChange.SetNumberOfSecondaries(0);
191
192	return pParticleChange;
193
194	}
195
196	G4double step_length;
197	step_length = aStep.GetStepLength();
198
199	MeanNumberOfPhotons = MeanNumberOfPhotons * step_length;
200
201	G4int NumPhotons = (G4int) G4Poisson(MeanNumberOfPhotons);
202
203	if (NumPhotons <= 0) {
204
205	// return unchanged particle and no secondaries
206
207	aParticleChange.SetNumberOfSecondaries(0);
208
209	return pParticleChange;
210	}
211
212	////////////////////////////////////////////////////////////////
213
214	aParticleChange.SetNumberOfSecondaries(NumPhotons);
215
216	if (fTrackSecondariesFirst) {
217	if (aTrack.GetTrackStatus() == fAlive )
218	aParticleChange.ProposeTrackStatus(fSuspend);
219	}
220
221	////////////////////////////////////////////////////////////////
222
223	G4double Pmin = Rindex->GetMinPhotonEnergy();
224	G4double Pmax = Rindex->GetMaxPhotonEnergy();
225	G4double dp = Pmax - Pmin;
226
227	G4double nMax = Rindex->GetMaxProperty();
228
229	G4double BetaInverse = 1./beta;
230
231	G4double maxCos = BetaInverse / nMax;
232	G4double maxSin2 = (1.0 - maxCos) * (1.0 + maxCos);
233
234	const G4double beta1 = pPreStepPoint ->GetBeta();
235	const G4double beta2 = pPostStepPoint->GetBeta();
236
237	G4double MeanNumberOfPhotons1 =
238	GetAverageNumberOfPhotons(charge,beta1,aMaterial,Rindex);
239	G4double MeanNumberOfPhotons2 =
240	GetAverageNumberOfPhotons(charge,beta2,aMaterial,Rindex);
241
242	for (G4int i = 0; i < NumPhotons; i++) {
243
244	// Determine photon energy
245
246	G4double rand;
247	G4double sampledEnergy, sampledRI;
248	G4double cosTheta, sin2Theta;
249
250	// sample an energy
251
252	do {
253	rand = G4UniformRand();
254	sampledEnergy = Pmin + rand * dp;
255	sampledRI = Rindex->GetProperty(sampledEnergy);
256	cosTheta = BetaInverse / sampledRI;
257
258	sin2Theta = (1.0 - cosTheta)*(1.0 + cosTheta);
259	rand = G4UniformRand();
260
261	} while (rand*maxSin2 > sin2Theta);
262
263	// Generate random position of photon on cone surface
264	// defined by Theta
265
266	rand = G4UniformRand();
267
268	G4double phi = twopi*rand;
269	G4double sinPhi = sin(phi);
270	G4double cosPhi = cos(phi);
271
272	// calculate x,y, and z components of photon energy
273	// (in coord system with primary particle direction
274	// aligned with the z axis)
275
276	G4double sinTheta = sqrt(sin2Theta);
277	G4double px = sinTheta*cosPhi;
278	G4double py = sinTheta*sinPhi;
279	G4double pz = cosTheta;
280
281	// Create photon momentum direction vector
282	// The momentum direction is still with respect
283	// to the coordinate system where the primary
284	// particle direction is aligned with the z axis
285
286	G4ParticleMomentum photonMomentum(px, py, pz);
287
288	// Rotate momentum direction back to global reference
289	// system
290
291	photonMomentum.rotateUz(p0);
292
293	// Determine polarization of new photon
294
295	G4double sx = cosTheta*cosPhi;
296	G4double sy = cosTheta*sinPhi;
297	G4double sz = -sinTheta;
298
299	G4ThreeVector photonPolarization(sx, sy, sz);
300
301	// Rotate back to original coord system
302
303	photonPolarization.rotateUz(p0);
304
305	// Generate a new photon:
306
307	G4DynamicParticle* aCerenkovPhoton =
308	new G4DynamicParticle(G4OpticalPhoton::OpticalPhoton(),
309	photonMomentum);
310	aCerenkovPhoton->SetPolarization
311	(photonPolarization.x(),
312	photonPolarization.y(),
313	photonPolarization.z());
314
315	aCerenkovPhoton->SetKineticEnergy(sampledEnergy);
316
317	// Generate new G4Track object:
318
319	G4double delta, NumberOfPhotons, N;
320
321	do {
322	rand = G4UniformRand();
323	delta = rand * aStep.GetStepLength();
324	NumberOfPhotons = MeanNumberOfPhotons1 - delta *
325	(MeanNumberOfPhotons1-MeanNumberOfPhotons2)/
326	aStep.GetStepLength();
327	N = G4UniformRand() *
328	std::max(MeanNumberOfPhotons1,MeanNumberOfPhotons2);
329	} while (N > NumberOfPhotons);
330
331	G4double deltaTime = delta /
332	((pPreStepPoint->GetVelocity()+
333	pPostStepPoint->GetVelocity())/2.);
334
335	G4double aSecondaryTime = t0 + deltaTime;
336
337	G4ThreeVector aSecondaryPosition =
338	x0 + rand * aStep.GetDeltaPosition();
339
340	G4Track* aSecondaryTrack =
341	new G4Track(aCerenkovPhoton,aSecondaryTime,aSecondaryPosition);
342
343	aSecondaryTrack->SetTouchableHandle(
344	aStep.GetPreStepPoint()->GetTouchableHandle());
345
346	aSecondaryTrack->SetParentID(aTrack.GetTrackID());
347
348	aParticleChange.AddSecondary(aSecondaryTrack);
349	}
350
351	if (verboseLevel>0) {
352	G4cout << "\n Exiting from G4Cerenkov::DoIt -- NumberOfSecondaries = "
353	<< aParticleChange.GetNumberOfSecondaries() << G4endl;
354	}
355
356	return pParticleChange;
357	}
358
359	// BuildThePhysicsTable for the Cerenkov process
360	// ---------------------------------------------
361	//
362
363	void G4Cerenkov::BuildThePhysicsTable()
364	{
365	if (thePhysicsTable) return;
366
367	const G4MaterialTable* theMaterialTable=
368	G4Material::GetMaterialTable();
369	G4int numOfMaterials = G4Material::GetNumberOfMaterials();
370
371	// create new physics table
372
373	thePhysicsTable = new G4PhysicsTable(numOfMaterials);
374
375	// loop for materials
376
377	for (G4int i=0 ; i < numOfMaterials; i++)
378	{
379	G4PhysicsOrderedFreeVector* aPhysicsOrderedFreeVector =
380	new G4PhysicsOrderedFreeVector();
381
382	// Retrieve vector of refraction indices for the material
383	// from the material's optical properties table
384
385	G4Material* aMaterial = (*theMaterialTable)[i];
386
387	G4MaterialPropertiesTable* aMaterialPropertiesTable =
388	aMaterial->GetMaterialPropertiesTable();
389
390	if (aMaterialPropertiesTable) {
391
392	G4MaterialPropertyVector* theRefractionIndexVector =
393	aMaterialPropertiesTable->GetProperty("RINDEX");
394
395	if (theRefractionIndexVector) {
396
397	// Retrieve the first refraction index in vector
398	// of (photon energy, refraction index) pairs
399
400	theRefractionIndexVector->ResetIterator();
401	++(*theRefractionIndexVector); // advance to 1st entry
402
403	G4double currentRI = theRefractionIndexVector->
404	GetProperty();
405
406	if (currentRI > 1.0) {
407
408	// Create first (photon energy, Cerenkov Integral)
409	// pair
410
411	G4double currentPM = theRefractionIndexVector->
412	GetPhotonEnergy();
413	G4double currentCAI = 0.0;
414
415	aPhysicsOrderedFreeVector->
416	InsertValues(currentPM , currentCAI);
417
418	// Set previous values to current ones prior to loop
419
420	G4double prevPM = currentPM;
421	G4double prevCAI = currentCAI;
422	G4double prevRI = currentRI;
423
424	// loop over all (photon energy, refraction index)
425	// pairs stored for this material
426
427	while(++(*theRefractionIndexVector))
428	{
429	currentRI=theRefractionIndexVector->
430	GetProperty();
431
432	currentPM = theRefractionIndexVector->
433	GetPhotonEnergy();
434
435	currentCAI = 0.5(1.0/(prevRIprevRI) +
436	1.0/(currentRI*currentRI));
437
438	currentCAI = prevCAI +
439	(currentPM - prevPM) * currentCAI;
440
441	aPhysicsOrderedFreeVector->
442	InsertValues(currentPM, currentCAI);
443
444	prevPM = currentPM;
445	prevCAI = currentCAI;
446	prevRI = currentRI;
447	}
448
449	}
450	}
451	}
452
453	// The Cerenkov integral for a given material
454	// will be inserted in thePhysicsTable
455	// according to the position of the material in
456	// the material table.
457
458	thePhysicsTable->insertAt(i,aPhysicsOrderedFreeVector);
459
460	}
461	}
462
463	// GetMeanFreePath
464	// ---------------
465	//
466
467	G4double G4Cerenkov::GetMeanFreePath(const G4Track&,
468	G4double,
469	G4ForceCondition*)
470	{
471	return 1.;
472	}
473
474	G4double G4Cerenkov::PostStepGetPhysicalInteractionLength(
475	const G4Track& aTrack,
476	G4double,
477	G4ForceCondition* condition)
478	{
479	*condition = NotForced;
480	G4double StepLimit = DBL_MAX;
481
482	const G4DynamicParticle* aParticle = aTrack.GetDynamicParticle();
483	const G4Material* aMaterial = aTrack.GetMaterial();
484	const G4MaterialCutsCouple* couple = aTrack.GetMaterialCutsCouple();
485
486	const G4double kineticEnergy = aParticle->GetKineticEnergy();
487	const G4ParticleDefinition* particleType = aParticle->GetDefinition();
488	const G4double mass = particleType->GetPDGMass();
489
490	// particle beta
491	const G4double beta = aParticle->GetTotalMomentum() /
492	aParticle->GetTotalEnergy();
493	// particle gamma
494	const G4double gamma = 1./std::sqrt(1.-beta*beta);
495
496	G4MaterialPropertiesTable* aMaterialPropertiesTable =
497	aMaterial->GetMaterialPropertiesTable();
498
499	const G4MaterialPropertyVector* Rindex = NULL;
500
501	if (aMaterialPropertiesTable)
502	Rindex = aMaterialPropertiesTable->GetProperty("RINDEX");
503
504	G4double nMax;
505	if (Rindex) {
506	nMax = Rindex->GetMaxProperty();
507	} else {
508	return StepLimit;
509	}
510
511	G4double BetaMin = 1./nMax;
512	if ( BetaMin >= 1. ) return StepLimit;
513
514	G4double GammaMin = 1./std::sqrt(1.-BetaMin*BetaMin);
515
516	if (gamma < GammaMin ) return StepLimit;
517
518	G4double kinEmin = mass*(GammaMin-1.);
519
520	G4double RangeMin = G4LossTableManager::Instance()->
521	GetRange(particleType,
522	kinEmin,
523	couple);
524	G4double Range = G4LossTableManager::Instance()->
525	GetRange(particleType,
526	kineticEnergy,
527	couple);
528
529	G4double Step = Range - RangeMin;
530	if (Step < 1.*um ) return StepLimit;
531
532	if (Step > 0. && Step < StepLimit) StepLimit = Step;
533
534	// If user has defined an average maximum number of photons to
535	// be generated in a Step, then calculate the Step length for
536	// that number of photons.
537
538	if (fMaxPhotons > 0) {
539
540	// particle charge
541	const G4double charge = aParticle->
542	GetDefinition()->GetPDGCharge();
543
544	G4double MeanNumberOfPhotons =
545	GetAverageNumberOfPhotons(charge,beta,aMaterial,Rindex);
546
547	G4double Step = 0.;
548	if (MeanNumberOfPhotons > 0.0) Step = fMaxPhotons /
549	MeanNumberOfPhotons;
550
551	if (Step > 0. && Step < StepLimit) StepLimit = Step;
552	}
553
554	// If user has defined an maximum allowed change in beta per step
555	if (fMaxBetaChange > 0.) {
556
557	G4double dedx = G4LossTableManager::Instance()->
558	GetDEDX(particleType,
559	kineticEnergy,
560	couple);
561
562	G4double deltaGamma = gamma -
563	1./std::sqrt(1.-betabeta
564	(1.-fMaxBetaChange)*
565	(1.-fMaxBetaChange));
566
567	G4double Step = mass * deltaGamma / dedx;
568
569	if (Step > 0. && Step < StepLimit) StepLimit = Step;
570
571	}
572
573	*condition = StronglyForced;
574	return StepLimit;
575	}
576
577	// GetAverageNumberOfPhotons
578	// -------------------------
579	// This routine computes the number of Cerenkov photons produced per
580	// GEANT-unit (millimeter) in the current medium.
581	// ^^^^^^^^^^
582
583	G4double
584	G4Cerenkov::GetAverageNumberOfPhotons(const G4double charge,
585	const G4double beta,
586	const G4Material* aMaterial,
587	const G4MaterialPropertyVector* Rindex) const
588	{
589	const G4double Rfact = 369.81/(eV * cm);
590
591	if(beta <= 0.0)return 0.0;
592
593	G4double BetaInverse = 1./beta;
594
595	// Vectors used in computation of Cerenkov Angle Integral:
596	// - Refraction Indices for the current material
597	// - new G4PhysicsOrderedFreeVector allocated to hold CAI's
598
599	G4int materialIndex = aMaterial->GetIndex();
600
601	// Retrieve the Cerenkov Angle Integrals for this material
602
603	G4PhysicsOrderedFreeVector* CerenkovAngleIntegrals =
604	(G4PhysicsOrderedFreeVector)((thePhysicsTable)(materialIndex));
605
606	if(!(CerenkovAngleIntegrals->IsFilledVectorExist()))return 0.0;
607
608	// Min and Max photon energies
609	G4double Pmin = Rindex->GetMinPhotonEnergy();
610	G4double Pmax = Rindex->GetMaxPhotonEnergy();
611
612	// Min and Max Refraction Indices
613	G4double nMin = Rindex->GetMinProperty();
614	G4double nMax = Rindex->GetMaxProperty();
615
616	// Max Cerenkov Angle Integral
617	G4double CAImax = CerenkovAngleIntegrals->GetMaxValue();
618
619	G4double dp, ge;
620
621	// If n(Pmax) < 1/Beta -- no photons generated
622
623	if (nMax < BetaInverse) {
624	dp = 0;
625	ge = 0;
626	}
627
628	// otherwise if n(Pmin) >= 1/Beta -- photons generated
629
630	else if (nMin > BetaInverse) {
631	dp = Pmax - Pmin;
632	ge = CAImax;
633	}
634
635	// If n(Pmin) < 1/Beta, and n(Pmax) >= 1/Beta, then
636	// we need to find a P such that the value of n(P) == 1/Beta.
637	// Interpolation is performed by the GetPhotonEnergy() and
638	// GetProperty() methods of the G4MaterialPropertiesTable and
639	// the GetValue() method of G4PhysicsVector.
640
641	else {
642	Pmin = Rindex->GetPhotonEnergy(BetaInverse);
643	dp = Pmax - Pmin;
644
645	// need boolean for current implementation of G4PhysicsVector
646	// ==> being phased out
647	G4bool isOutRange;
648	G4double CAImin = CerenkovAngleIntegrals->
649	GetValue(Pmin, isOutRange);
650	ge = CAImax - CAImin;
651
652	if (verboseLevel>0) {
653	G4cout << "CAImin = " << CAImin << G4endl;
654	G4cout << "ge = " << ge << G4endl;
655	}
656	}
657
658	// Calculate number of photons
659	G4double NumPhotons = Rfact * charge/eplus * charge/eplus *
660	(dp - ge * BetaInverse*BetaInverse);
661
662	return NumPhotons;
663	}

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