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26 //
27 // -----------------------------------------------------------------------------
28 //
29 // GEANT4 Class implementation file
30 //
31 // File name: G4GoudsmitSaundersonTable
32 //
33 // Author: Mihaly Novak / (Omrane Kadri)
34 //
35 // Creation date: 20.02.2009
36 //
37 // Class description:
38 // Class to handle multiple scattering angular distributions precomputed by
39 // using Kawrakow-Bielajew Goudsmit-Saunderson MSC model based on the screened
40 // Rutherford DCS for elastic scattering of electrons/positrons [1,2]. This
41 // class is used by G4GoudsmitSaundersonMscModel to sample the angular
42 // deflection of electrons/positrons after travelling a given path.
43 //
44 // Modifications:
45 // 04.03.2009 V.Ivanchenko cleanup and format according to Geant4 EM style
46 // 26.08.2009 O.Kadri: avoiding unuseful calculations and optimizing the root
47 // finding parameter error's within SampleTheta method
48 // 08.02.2010 O.Kadri: reduce delared variables; reduce error of finding root
49 // in secant method
50 // 26.03.2010 O.Kadri: minimum of used arrays in computation within the dichotomie
51 // finding method the error was the lowest value of uvalues
52 // 12.05.2010 O.Kadri: changing of sqrt((b-a)*(b-a)) with fabs(b-a)
53 // 18.05.2015 M. Novak This class has been completely replaced (only the original
54 // class name was kept; class description was also inserted):
55 // A new version of Kawrakow-Bielajew Goudsmit-Saunderson MSC model
56 // based on the screened Rutherford DCS for elastic scattering of
57 // electrons/positrons has been introduced[1,2]. The corresponding MSC
58 // angular distributions over a 2D parameter grid have been recomputed
59 // and the CDFs are now stored in a variable transformed (smooth) form
60 // together with the corresponding rational interpolation parameters.
61 // The new version is several times faster, more robust and accurate
62 // compared to the earlier version (G4GoudsmitSaundersonMscModel class
63 // that use these data has been also completely replaced)
64 // 28.04.2017 M. Novak: New representation of the angular distribution data with
65 // significantly reduced data size.
66 // 23.08.2017 M. Novak: Added funtionality to handle Mott-correction to the
67 // base GS angular distributions and some other factors (screening
68 // parameter, first and second moments) when Mott-correction is
69 // activated in the GS-MSC model.
70 //
71 // References:
72 // [1] A.F.Bielajew, NIMB, 111 (1996) 195-208
73 // [2] I.Kawrakow, A.F.Bielajew, NIMB 134(1998) 325-336
74 //
75 // -----------------------------------------------------------------------------
76
77 #include "G4GoudsmitSaundersonTable.hh"
78
79
80 #include "G4PhysicalConstants.hh"
81 #include "Randomize.hh"
82 #include "G4Log.hh"
83 #include "G4Exp.hh"
84
85 #include "G4GSMottCorrection.hh"
86 #include "G4MaterialTable.hh"
87 #include "G4Material.hh"
88 #include "G4MaterialCutsCouple.hh"
89 #include "G4ProductionCutsTable.hh"
90 #include "G4EmParameters.hh"
91
92 #include "G4String.hh"
93
94 #include <fstream>
95 #include <cstdlib>
96 #include <cmath>
97
98 #include <iostream>
99 #include <iomanip>
100
101 // perecomputed GS angular distributions, based on the Screened-Rutherford DCS
102 // are the same for e- and e+ so make sure we load them only onece
103 G4bool G4GoudsmitSaundersonTable::gIsInitialised = false;
104 //
105 std::vector<G4GoudsmitSaundersonTable::GSMSCAngularDtr*> G4GoudsmitSaundersonTable::gGSMSCAngularDistributions1;
106 std::vector<G4GoudsmitSaundersonTable::GSMSCAngularDtr*> G4GoudsmitSaundersonTable::gGSMSCAngularDistributions2;
107 //
108 std::vector<double> G4GoudsmitSaundersonTable::gMoliereBc;
109 std::vector<double> G4GoudsmitSaundersonTable::gMoliereXc2;
110
111
112 G4GoudsmitSaundersonTable::G4GoudsmitSaundersonTable(G4bool iselectron) {
113 fIsElectron = iselectron;
114 // set initial values: final values will be set in the Initialize method
115 fLogLambda0 = 0.; // will be set properly at init.
116 fLogDeltaLambda = 0.; // will be set properly at init.
117 fInvLogDeltaLambda = 0.; // will be set properly at init.
118 fInvDeltaQ1 = 0.; // will be set properly at init.
119 fDeltaQ2 = 0.; // will be set properly at init.
120 fInvDeltaQ2 = 0.; // will be set properly at init.
121 //
122 fLowEnergyLimit = 0.1*CLHEP::keV; // will be set properly at init.
123 fHighEnergyLimit = 100.0*CLHEP::MeV; // will be set properly at init.
124 //
125 fIsMottCorrection = false; // will be set properly at init.
126 fIsPWACorrection = false; // will be set properly at init.
127 fMottCorrection = nullptr;
128 //
129 fNumSPCEbinPerDec = 3;
130 }
131
132 G4GoudsmitSaundersonTable::~G4GoudsmitSaundersonTable() {
133 for (std::size_t i=0; i<gGSMSCAngularDistributions1.size(); ++i) {
134 if (gGSMSCAngularDistributions1[i]) {
135 delete [] gGSMSCAngularDistributions1[i]->fUValues;
136 delete [] gGSMSCAngularDistributions1[i]->fParamA;
137 delete [] gGSMSCAngularDistributions1[i]->fParamB;
138 delete gGSMSCAngularDistributions1[i];
139 }
140 }
141 gGSMSCAngularDistributions1.clear();
142 for (std::size_t i=0; i<gGSMSCAngularDistributions2.size(); ++i) {
143 if (gGSMSCAngularDistributions2[i]) {
144 delete [] gGSMSCAngularDistributions2[i]->fUValues;
145 delete [] gGSMSCAngularDistributions2[i]->fParamA;
146 delete [] gGSMSCAngularDistributions2[i]->fParamB;
147 delete gGSMSCAngularDistributions2[i];
148 }
149 }
150 gGSMSCAngularDistributions2.clear();
151 if (fMottCorrection) {
152 delete fMottCorrection;
153 fMottCorrection = nullptr;
154 }
155 // clear scp correction data
156 for (std::size_t imc=0; imc<fSCPCPerMatCuts.size(); ++imc) {
157 if (fSCPCPerMatCuts[imc]) {
158 fSCPCPerMatCuts[imc]->fVSCPC.clear();
159 delete fSCPCPerMatCuts[imc];
160 }
161 }
162 fSCPCPerMatCuts.clear();
163 //
164 gIsInitialised = false;
165 }
166
167 void G4GoudsmitSaundersonTable::Initialise(G4double lownergylimit, G4double highenergylimit) {
168 fLowEnergyLimit = lownergylimit;
169 fHighEnergyLimit = highenergylimit;
170 G4double lLambdaMin = G4Log(gLAMBMIN);
171 G4double lLambdaMax = G4Log(gLAMBMAX);
172 fLogLambda0 = lLambdaMin;
173 fLogDeltaLambda = (lLambdaMax-lLambdaMin)/(gLAMBNUM-1.);
174 fInvLogDeltaLambda = 1./fLogDeltaLambda;
175 fInvDeltaQ1 = 1./((gQMAX1-gQMIN1)/(gQNUM1-1.));
176 fDeltaQ2 = (gQMAX2-gQMIN2)/(gQNUM2-1.);
177 fInvDeltaQ2 = 1./fDeltaQ2;
178 // load precomputed angular distributions and set up several values used during the sampling
179 // these are particle independet => they go to static container: load them only onece
180 if (!gIsInitialised) {
181 // load pre-computed GS angular distributions (computed based on Screened-Rutherford DCS)
182 LoadMSCData();
183 gIsInitialised = true;
184 }
185 InitMoliereMSCParams();
186 // Mott-correction: particle(e- or e+) dependet so init them
187 if (fIsMottCorrection) {
188 if (!fMottCorrection) {
189 fMottCorrection = new G4GSMottCorrection(fIsElectron);
190 }
191 fMottCorrection->Initialise();
192 }
193 // init scattering power correction data; used only together with Mott-correction
194 // (Moliere's parameters must be initialised before)
195 if (fMottCorrection) {
196 InitSCPCorrection();
197 }
198 }
199
200
201 // samplig multiple scattering angles cos(theta) and sin(thata)
202 // - including no-scattering, single, "few" scattering cases as well
203 // - Mott-correction will be included if it was requested by the user (i.e. if fIsMottCorrection=true)
204 // lambdaval : s/lambda_el
205 // qval : s/lambda_el G1
206 // scra : screening parameter
207 // cost : will be the smapled cos(theta)
208 // sint : will be the smapled sin(theta)
209 // lekin : logarithm of the current kinetic energy
210 // beta2 : the corresponding beta square
211 // matindx : index of the current material
212 // returns true if it was msc
213 G4bool G4GoudsmitSaundersonTable::Sampling(G4double lambdaval, G4double qval, G4double scra, G4double &cost,
214 G4double &sint, G4double lekin, G4double beta2, G4int matindx,
215 GSMSCAngularDtr **gsDtr, G4int &mcekini, G4int &mcdelti,
216 G4double &transfPar, G4bool isfirst) {
217 G4double rand0 = G4UniformRand();
218 G4double expn = G4Exp(-lambdaval);
219 //
220 // no scattering case
221 if (rand0<expn) {
222 cost = 1.0;
223 sint = 0.0;
224 return false;
225 }
226 //
227 // single scattering case : sample from the single scattering PDF
228 // - Mott-correction will be included if it was requested by the user (i.e. if fIsMottCorrection=true)
229 if (rand0<(1.+lambdaval)*expn) {
230 // cost is sampled in SingleScattering()
231 cost = SingleScattering(lambdaval, scra, lekin, beta2, matindx);
232 // add protections
233 if (cost<-1.0) cost = -1.0;
234 if (cost>1.0) cost = 1.0;
235 // compute sin(theta) from the sampled cos(theta)
236 G4double dum0 = 1.-cost;
237 sint = std::sqrt(dum0*(2.0-dum0));
238 return false;
239 }
240 //
241 // handle this case:
242 // -lambdaval < 1 i.e. mean #elastic events along the step is < 1 but
243 // the currently sampled case is not 0 or 1 scattering. [Our minimal
244 // lambdaval (that we have precomputed, transformed angular distributions
245 // stored in a form of equally probabe intervalls together with rational
246 // interp. parameters) is 1.]
247 // -probability of having n elastic events follows Poisson stat. with
248 // lambdaval parameter.
249 // -the max. probability (when lambdaval=1) of having more than one
250 // elastic events is 0.2642411 and the prob of having 2,3,..,n elastic
251 // events decays rapidly with n. So set a max n to 10.
252 // -sampling of this cases is done in a one-by-one single elastic event way
253 // where the current #elastic event is sampled from the Poisson distr.
254 if (lambdaval<1.0) {
255 G4double prob, cumprob;
256 prob = cumprob = expn;
257 G4double curcost,cursint;
258 // init cos(theta) and sin(theta) to the zero scattering values
259 cost = 1.0;
260 sint = 0.0;
261 for (G4int iel=1; iel<10; ++iel) {
262 // prob of having iel scattering from Poisson
263 prob *= lambdaval/(G4double)iel;
264 cumprob += prob;
265 //
266 //sample cos(theta) from the singe scattering pdf:
267 // - Mott-correction will be included if it was requested by the user (i.e. if fIsMottCorrection=true)
268 curcost = SingleScattering(lambdaval, scra, lekin, beta2, matindx);
269 G4double dum0 = 1.-curcost;
270 cursint = dum0*(2.0-dum0); // sin^2(theta)
271 //
272 // if we got current deflection that is not too small
273 // then update cos(theta) sin(theta)
274 if (cursint>1.0e-20) {
275 cursint = std::sqrt(cursint);
276 G4double curphi = CLHEP::twopi*G4UniformRand();
277 cost = cost*curcost-sint*cursint*std::cos(curphi);
278 sint = std::sqrt(std::max(0.0, (1.0-cost)*(1.0+cost)));
279 }
280 //
281 // check if we have done enough scattering i.e. sampling from the Poisson
282 if (rand0<cumprob) {
283 return false;
284 }
285 }
286 // if reached the max iter i.e. 10
287 return false;
288 }
289 //
290 // multiple scattering case with lambdavalue >= 1:
291 // - use the precomputed and transformed Goudsmit-Saunderson angular
292 // distributions to sample cos(theta)
293 // - Mott-correction will be included if it was requested by the user (i.e. if fIsMottCorrection=true)
294 cost = SampleCosTheta(lambdaval, qval, scra, lekin, beta2, matindx, gsDtr, mcekini, mcdelti, transfPar, isfirst);
295 // add protections
296 if (cost<-1.0) cost = -1.0;
297 if (cost> 1.0) cost = 1.0;
298 // compute cos(theta) and sin(theta) from the sampled 1-cos(theta)
299 G4double dum0 = 1.0-cost;
300 sint = std::sqrt(dum0*(2.0-dum0));
301 // return true if it was msc
302 return true;
303 }
304
305
306 G4double G4GoudsmitSaundersonTable::SampleCosTheta(G4double lambdaval, G4double qval, G4double scra,
307 G4double lekin, G4double beta2, G4int matindx,
308 GSMSCAngularDtr **gsDtr, G4int &mcekini,G4int &mcdelti,
309 G4double &transfPar, G4bool isfirst) {
310 G4double cost = 1.;
311 // determine the base GS angular distribution if it is the first call (when sub-step sampling is used)
312 if (isfirst) {
313 *gsDtr = GetGSAngularDtr(scra, lambdaval, qval, transfPar);
314 }
315 // sample cost from the GS angular distribution (computed based on Screened-Rutherford DCS)
316 cost = SampleGSSRCosTheta(*gsDtr, transfPar);
317 // Mott-correction if it was requested by the user
318 if (fIsMottCorrection && *gsDtr) { // no Mott-correction in case of izotropic theta
319 static const G4int nlooplim = 1000;
320 G4int nloop = 0 ; // rejection loop counter
321 // G4int ekindx = -1; // evaluate only in the first call
322 // G4int deltindx = -1 ; // evaluate only in the first call
323 G4double val = fMottCorrection->GetMottRejectionValue(lekin, beta2, qval, cost, matindx, mcekini, mcdelti);
324 while (G4UniformRand()>val && ++nloop<nlooplim) {
325 // sampling cos(theta)
326 cost = SampleGSSRCosTheta(*gsDtr, transfPar);
327 val = fMottCorrection->GetMottRejectionValue(lekin, beta2, qval, cost, matindx, mcekini, mcdelti);
328 };
329 }
330 return cost;
331 }
332
333
334 // returns with cost sampled from the GS angular distribution computed based on Screened-Rutherford DCS
335 G4double G4GoudsmitSaundersonTable::SampleGSSRCosTheta(const GSMSCAngularDtr *gsDtr, G4double transfpar) {
336 // check if isotropic theta (i.e. cost is uniform on [-1:1])
337 if (!gsDtr) {
338 return 1.-2.0*G4UniformRand();
339 }
340 //
341 // sampling form the selected distribution
342 G4double ndatm1 = gsDtr->fNumData-1.;
343 G4double delta = 1.0/ndatm1;
344 // determine lower cumulative bin inidex
345 G4double rndm = G4UniformRand();
346 G4int indxl = rndm*ndatm1;
347 G4double aval = rndm-indxl*delta;
348 G4double dum0 = delta*aval;
349
350 G4double dum1 = (1.0+gsDtr->fParamA[indxl]+gsDtr->fParamB[indxl])*dum0;
351 G4double dum2 = delta*delta + gsDtr->fParamA[indxl]*dum0 + gsDtr->fParamB[indxl]*aval*aval;
352 G4double sample = gsDtr->fUValues[indxl] + dum1/dum2 *(gsDtr->fUValues[indxl+1]-gsDtr->fUValues[indxl]);
353 // transform back u to cos(theta) :
354 // this is the sampled cos(theta) = (2.0*para*sample)/(1.0-sample+para)
355 return 1.-(2.0*transfpar*sample)/(1.0-sample+transfpar);
356 }
357
358
359 // determine the GS angular distribution we need to sample from: will set other things as well ...
360 G4GoudsmitSaundersonTable::GSMSCAngularDtr* G4GoudsmitSaundersonTable::GetGSAngularDtr(G4double scra,
361 G4double &lambdaval, G4double &qval, G4double &transfpar) {
362 GSMSCAngularDtr *dtr = nullptr;
363 G4bool first = false;
364 // isotropic cost above gQMAX2 (i.e. dtr stays nullptr)
365 if (qval<gQMAX2) {
366 G4int lamIndx = -1; // lambda value index
367 G4int qIndx = -1; // lambda value index
368 // init to second grid Q values
369 G4int numQVal = gQNUM2;
370 G4double minQVal = gQMIN2;
371 G4double invDelQ = fInvDeltaQ2;
372 G4double pIndxH = 0.; // probability of taking higher index
373 // check if first or second grid needs to be used
374 if (qval<gQMIN2) { // first grid
375 first = true;
376 // protect against qval<gQMIN1
377 if (qval<gQMIN1) {
378 qval = gQMIN1;
379 qIndx = 0;
380 //pIndxH = 0.;
381 }
382 // set to first grid Q values
383 numQVal = gQNUM1;
384 minQVal = gQMIN1;
385 invDelQ = fInvDeltaQ1;
386 }
387 // make sure that lambda = s/lambda_el is in [gLAMBMIN,gLAMBMAX)
388 // lambda<gLAMBMIN=1 is already handeled before so lambda>= gLAMBMIN for sure
389 if (lambdaval>=gLAMBMAX) {
390 lambdaval = gLAMBMAX-1.e-8;
391 lamIndx = gLAMBNUM-1;
392 }
393 G4double lLambda = G4Log(lambdaval);
394 //
395 // determine lower lambda (=s/lambda_el) index: linear interp. on log(lambda) scale
396 if (lamIndx<0) {
397 pIndxH = (lLambda-fLogLambda0)*fInvLogDeltaLambda;
398 lamIndx = (G4int)(pIndxH); // lower index of the lambda bin
399 pIndxH = pIndxH-lamIndx; // probability of taking the higher index distribution
400 if (G4UniformRand()<pIndxH) {
401 ++lamIndx;
402 }
403 }
404 //
405 // determine lower Q (=s/lambda_el G1) index: linear interp. on Q
406 if (qIndx<0) {
407 pIndxH = (qval-minQVal)*invDelQ;
408 qIndx = (G4int)(pIndxH); // lower index of the Q bin
409 pIndxH = pIndxH-qIndx;
410 if (G4UniformRand()<pIndxH) {
411 ++qIndx;
412 }
413 }
414 // set indx
415 G4int indx = lamIndx*numQVal+qIndx;
416 if (first) {
417 dtr = gGSMSCAngularDistributions1[indx];
418 } else {
419 dtr = gGSMSCAngularDistributions2[indx];
420 }
421 // dtr might be nullptr that indicates isotropic cot distribution because:
422 // - if the selected lamIndx, qIndx correspond to L(=s/lambda_el) and Q(=s/lambda_el G1) such that G1(=Q/L) > 1
423 // G1 should always be < 1 and if G1 is ~1 -> the dtr is isotropic (this can only happen in case of the 2. grid)
424 //
425 // compute the transformation parameter
426 if (lambdaval>10.0) {
427 transfpar = 0.5*(-2.77164+lLambda*( 2.94874-lLambda*(0.1535754-lLambda*0.00552888) ));
428 } else {
429 transfpar = 0.5*(1.347+lLambda*(0.209364-lLambda*(0.45525-lLambda*(0.50142-lLambda*0.081234))));
430 }
431 transfpar *= (lambdaval+4.0)*scra;
432 }
433 // return with the selected GS angular distribution that we need to sample cost from (if nullptr => isotropic cost)
434 return dtr;
435 }
436
437
438 void G4GoudsmitSaundersonTable::LoadMSCData() {
439 gGSMSCAngularDistributions1.resize(gLAMBNUM*gQNUM1,nullptr);
440 const G4String str1 = G4EmParameters::Instance()->GetDirLEDATA() + "/msc_GS/GSGrid_1/gsDistr_";
441 for (G4int il=0; il<gLAMBNUM; ++il) {
442 G4String fname = str1 + std::to_string(il);
443 std::ifstream infile(fname,std::ios::in);
444 if (!infile.is_open()) {
445 G4String msgc = "Cannot open file: " + fname;
446 G4Exception("G4GoudsmitSaundersonTable::LoadMSCData()","em0006",
447 FatalException, msgc.c_str());
448 return;
449 }
450 for (G4int iq=0; iq<gQNUM1; ++iq) {
451 auto gsd = new GSMSCAngularDtr();
452 infile >> gsd->fNumData;
453 gsd->fUValues = new G4double[gsd->fNumData]();
454 gsd->fParamA = new G4double[gsd->fNumData]();
455 gsd->fParamB = new G4double[gsd->fNumData]();
456 G4double ddummy;
457 infile >> ddummy; infile >> ddummy;
458 for (G4int i=0; i<gsd->fNumData; ++i) {
459 infile >> gsd->fUValues[i];
460 infile >> gsd->fParamA[i];
461 infile >> gsd->fParamB[i];
462 }
463 gGSMSCAngularDistributions1[il*gQNUM1+iq] = gsd;
464 }
465 infile.close();
466 }
467 //
468 // second grid
469 gGSMSCAngularDistributions2.resize(gLAMBNUM*gQNUM2,nullptr);
470 const G4String str2 = G4EmParameters::Instance()->GetDirLEDATA() + "/msc_GS/GSGrid_2/gsDistr_";
471 for (G4int il=0; il<gLAMBNUM; ++il) {
472 G4String fname = str2 + std::to_string(il);
473 std::ifstream infile(fname,std::ios::in);
474 if (!infile.is_open()) {
475 G4String msgc = "Cannot open file: " + fname;
476 G4Exception("G4GoudsmitSaundersonTable::LoadMSCData()","em0006",
477 FatalException, msgc.c_str());
478 return;
479 }
480 for (G4int iq=0; iq<gQNUM2; ++iq) {
481 G4int numData;
482 infile >> numData;
483 if (numData>1) {
484 auto gsd = new GSMSCAngularDtr();
485 gsd->fNumData = numData;
486 gsd->fUValues = new G4double[gsd->fNumData]();
487 gsd->fParamA = new G4double[gsd->fNumData]();
488 gsd->fParamB = new G4double[gsd->fNumData]();
489 double ddummy;
490 infile >> ddummy; infile >> ddummy;
491 for (G4int i=0; i<gsd->fNumData; ++i) {
492 infile >> gsd->fUValues[i];
493 infile >> gsd->fParamA[i];
494 infile >> gsd->fParamB[i];
495 }
496 gGSMSCAngularDistributions2[il*gQNUM2+iq] = gsd;
497 } else {
498 gGSMSCAngularDistributions2[il*gQNUM2+iq] = nullptr;
499 }
500 }
501 infile.close();
502 }
503 }
504
505 // samples cost in single scattering based on Screened-Rutherford DCS
506 // (with Mott-correction if it was requested)
507 G4double G4GoudsmitSaundersonTable::SingleScattering(G4double /*lambdaval*/, G4double scra,
508 G4double lekin, G4double beta2,
509 G4int matindx) {
510 G4double rand1 = G4UniformRand();
511 // sample cost from the Screened-Rutherford DCS
512 G4double cost = 1.-2.0*scra*rand1/(1.0-rand1+scra);
513 // Mott-correction if it was requested by the user
514 if (fIsMottCorrection) {
515 static const G4int nlooplim = 1000; // rejection loop limit
516 G4int nloop = 0 ; // loop counter
517 G4int ekindx = -1 ; // evaluate only in the first call
518 G4int deltindx = 0 ; // single scattering case
519 G4double q1 = 0.; // not used when deltindx = 0;
520 // computing Mott rejection function value
521 G4double val = fMottCorrection->GetMottRejectionValue(lekin, beta2, q1, cost,
522 matindx, ekindx, deltindx);
523 while (G4UniformRand()>val && ++nloop<nlooplim) {
524 // sampling cos(theta) from the Screened-Rutherford DCS
525 rand1 = G4UniformRand();
526 cost = 1.-2.0*scra*rand1/(1.0-rand1+scra);
527 // computing Mott rejection function value
528 val = fMottCorrection->GetMottRejectionValue(lekin, beta2, q1, cost, matindx,
529 ekindx, deltindx);
530 };
531 }
532 return cost;
533 }
534
535
536 void G4GoudsmitSaundersonTable::GetMottCorrectionFactors(G4double logekin, G4double beta2,
537 G4int matindx, G4double &mcToScr,
538 G4double &mcToQ1, G4double &mcToG2PerG1) {
539 if (fIsMottCorrection) {
540 fMottCorrection->GetMottCorrectionFactors(logekin, beta2, matindx, mcToScr, mcToQ1, mcToG2PerG1);
541 }
542 }
543
544
545 // compute material dependent Moliere MSC parameters at initialisation
546 void G4GoudsmitSaundersonTable::InitMoliereMSCParams() {
547 const G4double const1 = 7821.6; // [cm2/g]
548 const G4double const2 = 0.1569; // [cm2 MeV2 / g]
549 const G4double finstrc2 = 5.325135453E-5; // fine-structure const. square
550
551 G4MaterialTable* theMaterialTable = G4Material::GetMaterialTable();
552 // get number of materials in the table
553 std::size_t numMaterials = theMaterialTable->size();
554 // make sure that we have long enough vectors
555 if(gMoliereBc.size()<numMaterials) {
556 gMoliereBc.resize(numMaterials);
557 gMoliereXc2.resize(numMaterials);
558 }
559 G4double xi = 1.0;
560 G4int maxZ = 200;
561 if (fIsMottCorrection || fIsPWACorrection) {
562 // xi = 1.0; <= always set to 1 from now on
563 maxZ = G4GSMottCorrection::GetMaxZet();
564 }
565 //
566 for (std::size_t imat=0; imat<numMaterials; ++imat) {
567 const G4Material* theMaterial = (*theMaterialTable)[imat];
568 const G4ElementVector* theElemVect = theMaterial->GetElementVector();
569 const G4int numelems = (G4int)theMaterial->GetNumberOfElements();
570 //
571 const G4double* theNbAtomsPerVolVect = theMaterial->GetVecNbOfAtomsPerVolume();
572 G4double theTotNbAtomsPerVol = theMaterial->GetTotNbOfAtomsPerVolume();
573 //
574 G4double zs = 0.0;
575 G4double zx = 0.0;
576 G4double ze = 0.0;
577 G4double sa = 0.0;
578 //
579 for(G4int ielem = 0; ielem < numelems; ielem++) {
580 G4double zet = (*theElemVect)[ielem]->GetZ();
581 if (zet>maxZ) {
582 zet = (G4double)maxZ;
583 }
584 G4double iwa = (*theElemVect)[ielem]->GetN();
585 G4double ipz = theNbAtomsPerVolVect[ielem]/theTotNbAtomsPerVol;
586 G4double dum = ipz*zet*(zet+xi);
587 zs += dum;
588 ze += dum*(-2.0/3.0)*G4Log(zet);
589 zx += dum*G4Log(1.0+3.34*finstrc2*zet*zet);
590 sa += ipz*iwa;
591 }
592 G4double density = theMaterial->GetDensity()*CLHEP::cm3/CLHEP::g; // [g/cm3]
593 //
594 gMoliereBc[theMaterial->GetIndex()] = const1*density*zs/sa*G4Exp(ze/zs)/G4Exp(zx/zs); //[1/cm]
595 gMoliereXc2[theMaterial->GetIndex()] = const2*density*zs/sa; // [MeV2/cm]
596 // change to Geant4 internal units of 1/length and energ2/length
597 gMoliereBc[theMaterial->GetIndex()] *= 1.0/CLHEP::cm;
598 gMoliereXc2[theMaterial->GetIndex()] *= CLHEP::MeV*CLHEP::MeV/CLHEP::cm;
599 }
600 }
601
602
603 // this method is temporary, will be removed/replaced with a more effictien solution after 10.3.ref09
604 G4double G4GoudsmitSaundersonTable::ComputeScatteringPowerCorrection(const G4MaterialCutsCouple *matcut, G4double ekin) {
605 G4int imc = matcut->GetIndex();
606 G4double corFactor = 1.0;
607 if (!(fSCPCPerMatCuts[imc]->fIsUse) || ekin<=fSCPCPerMatCuts[imc]->fPrCut) {
608 return corFactor;
609 }
610 // get the scattering power correction factor
611 G4double lekin = G4Log(ekin);
612 G4double remaining = (lekin-fSCPCPerMatCuts[imc]->fLEmin)*fSCPCPerMatCuts[imc]->fILDel;
613 std::size_t lindx = (std::size_t)remaining;
614 remaining -= lindx;
615 std::size_t imax = fSCPCPerMatCuts[imc]->fVSCPC.size()-1;
616 if (lindx>=imax) {
617 corFactor = fSCPCPerMatCuts[imc]->fVSCPC[imax];
618 } else {
619 corFactor = fSCPCPerMatCuts[imc]->fVSCPC[lindx] + remaining*(fSCPCPerMatCuts[imc]->fVSCPC[lindx+1]-fSCPCPerMatCuts[imc]->fVSCPC[lindx]);
620 }
621 return corFactor;
622 }
623
624
625 void G4GoudsmitSaundersonTable::InitSCPCorrection() {
626 // get the material-cuts table
627 G4ProductionCutsTable *thePCTable = G4ProductionCutsTable::GetProductionCutsTable();
628 std::size_t numMatCuts = thePCTable->GetTableSize();
629 // clear container if any
630 for (std::size_t imc=0; imc<fSCPCPerMatCuts.size(); ++imc) {
631 if (fSCPCPerMatCuts[imc]) {
632 fSCPCPerMatCuts[imc]->fVSCPC.clear();
633 delete fSCPCPerMatCuts[imc];
634 fSCPCPerMatCuts[imc] = nullptr;
635 }
636 }
637 //
638 // set size of the container and create the corresponding data structures
639 fSCPCPerMatCuts.resize(numMatCuts,nullptr);
640 // loop over the material-cuts and create scattering power correction data structure for each
641 for (G4int imc=0; imc<(G4int)numMatCuts; ++imc) {
642 const G4MaterialCutsCouple *matCut = thePCTable->GetMaterialCutsCouple(imc);
643 // get e- production cut in the current material-cuts in energy
644 G4double limit;
645 G4double ecut;
646 if (fIsElectron) {
647 ecut = (*(thePCTable->GetEnergyCutsVector(idxG4ElectronCut)))[matCut->GetIndex()];
648 limit = 2.*ecut;
649 } else {
650 ecut = (*(thePCTable->GetEnergyCutsVector(idxG4PositronCut)))[matCut->GetIndex()];
651 limit = ecut;
652 }
653 G4double min = std::max(limit,fLowEnergyLimit);
654 G4double max = fHighEnergyLimit;
655 if (min>=max) {
656 fSCPCPerMatCuts[imc] = new SCPCorrection();
657 fSCPCPerMatCuts[imc]->fIsUse = false;
658 fSCPCPerMatCuts[imc]->fPrCut = min;
659 continue;
660 }
661 G4int numEbins = fNumSPCEbinPerDec*G4lrint(std::log10(max/min));
662 numEbins = std::max(numEbins,3);
663 G4double lmin = G4Log(min);
664 G4double ldel = G4Log(max/min)/(numEbins-1.0);
665 fSCPCPerMatCuts[imc] = new SCPCorrection();
666 fSCPCPerMatCuts[imc]->fVSCPC.resize(numEbins,1.0);
667 fSCPCPerMatCuts[imc]->fIsUse = true;
668 fSCPCPerMatCuts[imc]->fPrCut = min;
669 fSCPCPerMatCuts[imc]->fLEmin = lmin;
670 fSCPCPerMatCuts[imc]->fILDel = 1./ldel;
671 for (G4int ie=0; ie<numEbins; ++ie) {
672 G4double ekin = G4Exp(lmin+ie*ldel);
673 G4double scpCorr = 1.0;
674 // compute correction factor: I.Kawrakow NIMB 114(1996)307-326 (Eqs(32-37))
675 if (ie>0) {
676 G4double tau = ekin/CLHEP::electron_mass_c2;
677 G4double tauCut = ecut/CLHEP::electron_mass_c2;
678 // Moliere's screening parameter
679 G4int matindx = (G4int)matCut->GetMaterial()->GetIndex();
680 G4double A = GetMoliereXc2(matindx)/(4.0*tau*(tau+2.)*GetMoliereBc(matindx));
681 G4double gr = (1.+2.*A)*G4Log(1.+1./A)-2.;
682 G4double dum0 = (tau+2.)/(tau+1.);
683 G4double dum1 = tau+1.;
684 G4double gm = G4Log(0.5*tau/tauCut) + (1.+dum0*dum0)*G4Log(2.*(tau-tauCut+2.)/(tau+4.))
685 - 0.25*(tau+2.)*( tau+2.+2.*(2.*tau+1.)/(dum1*dum1))*
686 G4Log((tau+4.)*(tau-tauCut)/tau/(tau-tauCut+2.))
687 + 0.5*(tau-2*tauCut)*(tau+2.)*(1./(tau-tauCut)-1./(dum1*dum1));
688 if (gm<gr) {
689 gm = gm/gr;
690 } else {
691 gm = 1.;
692 }
693 G4double z0 = matCut->GetMaterial()->GetIonisation()->GetZeffective();
694 scpCorr = 1.-gm*z0/(z0*(z0+1.));
695 }
696 fSCPCPerMatCuts[imc]->fVSCPC[ie] = scpCorr;
697 }
698 }
699 }
700