source: trunk/source/processes/electromagnetic/standard/src/G4UrbanMscModel.cc@ 1192

Last change on this file since 1192 was 1055, checked in by garnier, 17 years ago

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25//
26//
27// $Id: G4UrbanMscModel.cc,v 1.90 2009/04/29 13:30:22 vnivanch Exp $
28// GEANT4 tag $Name: geant4-09-03-beta-cand-01 $
29//
30// -------------------------------------------------------------------
31//
32// GEANT4 Class file
33//
34//
35// File name: G4UrbanMscModel
36//
37// Author: Laszlo Urban
38//
39// Creation date: 06.03.2008
40//
41// Modifications:
42//
43// 06-03-2008 starting point : G4UrbanMscModel2 = G4UrbanMscModel 9.1 ref 02
44//
45// 13-03-08 Bug in SampleScattering (which caused lateral asymmetry) fixed
46// (L.Urban)
47//
48// 14-03-08 Simplification of step limitation in ComputeTruePathLengthLimit,
49// + tlimitmin is the same for UseDistancetoBoundary and
50// UseSafety (L.Urban)
51//
52// 16-03-08 Reorganization of SampleCosineTheta + new method SimpleScattering
53// SimpleScattering is used if the relative energy loss is too big
54// or theta0 is too big (see data members rellossmax, theta0max)
55// (L.Urban)
56//
57// 17-03-08 tuning of the correction factor in ComputeTheta0 (L.Urban)
58//
59// 19-03-08 exponent c of the 'tail' model function is not equal to 2 any more,
60// value of c has been extracted from some e- scattering data (L.Urban)
61//
62// 24-03-08 Step limitation in ComputeTruePathLengthLimit has been
63// simplified further + some data members have been removed (L.Urban)
64//
65// 24-07-08 central part of scattering angle (theta0) has been tuned
66// tail of the scattering angle distribution has been tuned
67// using some e- and proton scattering data
68//
69// 05-08-08 bugfix in ComputeTruePathLengthLimit (L.Urban)
70//
71// 09-10-08 theta0 and tail have been retuned using some e-,mu,proton
72// scattering data (L.Urban)
73// + single scattering without path length correction for
74// small steps (t < tlimitmin, for UseDistanceToBoundary only)
75//
76// 15-10-08 Moliere-Bethe screening in the single scattering part(L.Urban)
77//
78// 17-10-08 stepping similar to that in model (9.1) for UseSafety case
79// for e+/e- in order to speed up the code for calorimeters
80//
81// 23-10-08 bugfix in the screeningparameter of the single scattering part,
82// some technical change in order to speed up the code (UpdateCache)
83//
84// 27-10-08 bugfix in ComputeTruePathLengthLimit (affects UseDistanceToBoundary
85// stepping type only) (L.Urban)
86//
87// 28-04-09 move G4UrbanMscModel2 from the g49.2 to G4UrbanMscModel.
88// now it is frozen (V.Ivanchenk0)
89
90// Class Description:
91//
92// Implementation of the model of multiple scattering based on
93// H.W.Lewis Phys Rev 78 (1950) 526 and others
94
95// -------------------------------------------------------------------
96// In its present form the model can be used for simulation
97// of the e-/e+, muon and charged hadron multiple scattering
98//
99
100
101//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
102//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
103
104#include "G4UrbanMscModel.hh"
105#include "Randomize.hh"
106#include "G4Electron.hh"
107#include "G4LossTableManager.hh"
108#include "G4ParticleChangeForMSC.hh"
109
110#include "G4Poisson.hh"
111#include "globals.hh"
112
113//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
114
115using namespace std;
116
117G4UrbanMscModel::G4UrbanMscModel(const G4String& nam)
118 : G4VMscModel(nam),
119 isInitialized(false)
120{
121 masslimite = 0.6*MeV;
122 lambdalimit = 1.*mm;
123 fr = 0.02;
124 facsafety = 0.3;
125 taubig = 8.0;
126 tausmall = 1.e-16;
127 taulim = 1.e-6;
128 currentTau = taulim;
129 tlimitminfix = 1.e-6*mm;
130 stepmin = tlimitminfix;
131 smallstep = 1.e10;
132 currentRange = 0. ;
133 rangeinit = 0.;
134 tlimit = 1.e10*mm;
135 tlimitmin = 10.*tlimitminfix;
136 tgeom = 1.e50*mm;
137 geombig = 1.e50*mm;
138 geommin = 1.e-3*mm;
139 geomlimit = geombig;
140 presafety = 0.*mm;
141
142 y = 0.;
143
144 Zold = 0.;
145 Zeff = 1.;
146 Z2 = 1.;
147 Z23 = 1.;
148 lnZ = 0.;
149 coeffth1 = 0.;
150 coeffth2 = 0.;
151 coeffc1 = 0.;
152 coeffc2 = 0.;
153 scr1ini = fine_structure_const*fine_structure_const*
154 electron_mass_c2*electron_mass_c2/(0.885*0.885*4.*pi);
155 scr2ini = 3.76*fine_structure_const*fine_structure_const;
156 scr1 = 0.;
157 scr2 = 0.;
158
159 theta0max = pi/6.;
160 rellossmax = 0.50;
161 third = 1./3.;
162 particle = 0;
163 theManager = G4LossTableManager::Instance();
164 inside = false;
165 insideskin = false;
166
167}
168
169//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
170
171G4UrbanMscModel::~G4UrbanMscModel()
172{}
173
174//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
175
176void G4UrbanMscModel::Initialise(const G4ParticleDefinition* p,
177 const G4DataVector&)
178{
179 skindepth = skin*stepmin;
180 if(isInitialized) return;
181 // set values of some data members
182 SetParticle(p);
183
184 fParticleChange = GetParticleChangeForMSC();
185 InitialiseSafetyHelper();
186
187 isInitialized = true;
188}
189
190//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
191
192G4double G4UrbanMscModel::ComputeCrossSectionPerAtom(
193 const G4ParticleDefinition* part,
194 G4double KineticEnergy,
195 G4double AtomicNumber,G4double,
196 G4double, G4double)
197{
198 const G4double sigmafactor = twopi*classic_electr_radius*classic_electr_radius;
199 const G4double epsfactor = 2.*electron_mass_c2*electron_mass_c2*
200 Bohr_radius*Bohr_radius/(hbarc*hbarc);
201 const G4double epsmin = 1.e-4 , epsmax = 1.e10;
202
203 const G4double Zdat[15] = { 4., 6., 13., 20., 26., 29., 32., 38., 47.,
204 50., 56., 64., 74., 79., 82. };
205
206 const G4double Tdat[22] = { 100*eV, 200*eV, 400*eV, 700*eV,
207 1*keV, 2*keV, 4*keV, 7*keV,
208 10*keV, 20*keV, 40*keV, 70*keV,
209 100*keV, 200*keV, 400*keV, 700*keV,
210 1*MeV, 2*MeV, 4*MeV, 7*MeV,
211 10*MeV, 20*MeV};
212
213 // corr. factors for e-/e+ lambda for T <= Tlim
214 G4double celectron[15][22] =
215 {{1.125,1.072,1.051,1.047,1.047,1.050,1.052,1.054,
216 1.054,1.057,1.062,1.069,1.075,1.090,1.105,1.111,
217 1.112,1.108,1.100,1.093,1.089,1.087 },
218 {1.408,1.246,1.143,1.096,1.077,1.059,1.053,1.051,
219 1.052,1.053,1.058,1.065,1.072,1.087,1.101,1.108,
220 1.109,1.105,1.097,1.090,1.086,1.082 },
221 {2.833,2.268,1.861,1.612,1.486,1.309,1.204,1.156,
222 1.136,1.114,1.106,1.106,1.109,1.119,1.129,1.132,
223 1.131,1.124,1.113,1.104,1.099,1.098 },
224 {3.879,3.016,2.380,2.007,1.818,1.535,1.340,1.236,
225 1.190,1.133,1.107,1.099,1.098,1.103,1.110,1.113,
226 1.112,1.105,1.096,1.089,1.085,1.098 },
227 {6.937,4.330,2.886,2.256,1.987,1.628,1.395,1.265,
228 1.203,1.122,1.080,1.065,1.061,1.063,1.070,1.073,
229 1.073,1.070,1.064,1.059,1.056,1.056 },
230 {9.616,5.708,3.424,2.551,2.204,1.762,1.485,1.330,
231 1.256,1.155,1.099,1.077,1.070,1.068,1.072,1.074,
232 1.074,1.070,1.063,1.059,1.056,1.052 },
233 {11.72,6.364,3.811,2.806,2.401,1.884,1.564,1.386,
234 1.300,1.180,1.112,1.082,1.073,1.066,1.068,1.069,
235 1.068,1.064,1.059,1.054,1.051,1.050 },
236 {18.08,8.601,4.569,3.183,2.662,2.025,1.646,1.439,
237 1.339,1.195,1.108,1.068,1.053,1.040,1.039,1.039,
238 1.039,1.037,1.034,1.031,1.030,1.036 },
239 {18.22,10.48,5.333,3.713,3.115,2.367,1.898,1.631,
240 1.498,1.301,1.171,1.105,1.077,1.048,1.036,1.033,
241 1.031,1.028,1.024,1.022,1.021,1.024 },
242 {14.14,10.65,5.710,3.929,3.266,2.453,1.951,1.669,
243 1.528,1.319,1.178,1.106,1.075,1.040,1.027,1.022,
244 1.020,1.017,1.015,1.013,1.013,1.020 },
245 {14.11,11.73,6.312,4.240,3.478,2.566,2.022,1.720,
246 1.569,1.342,1.186,1.102,1.065,1.022,1.003,0.997,
247 0.995,0.993,0.993,0.993,0.993,1.011 },
248 {22.76,20.01,8.835,5.287,4.144,2.901,2.219,1.855,
249 1.677,1.410,1.224,1.121,1.073,1.014,0.986,0.976,
250 0.974,0.972,0.973,0.974,0.975,0.987 },
251 {50.77,40.85,14.13,7.184,5.284,3.435,2.520,2.059,
252 1.837,1.512,1.283,1.153,1.091,1.010,0.969,0.954,
253 0.950,0.947,0.949,0.952,0.954,0.963 },
254 {65.87,59.06,15.87,7.570,5.567,3.650,2.682,2.182,
255 1.939,1.579,1.325,1.178,1.108,1.014,0.965,0.947,
256 0.941,0.938,0.940,0.944,0.946,0.954 },
257 {55.60,47.34,15.92,7.810,5.755,3.767,2.760,2.239,
258 1.985,1.609,1.343,1.188,1.113,1.013,0.960,0.939,
259 0.933,0.930,0.933,0.936,0.939,0.949 }};
260
261 G4double cpositron[15][22] = {
262 {2.589,2.044,1.658,1.446,1.347,1.217,1.144,1.110,
263 1.097,1.083,1.080,1.086,1.092,1.108,1.123,1.131,
264 1.131,1.126,1.117,1.108,1.103,1.100 },
265 {3.904,2.794,2.079,1.710,1.543,1.325,1.202,1.145,
266 1.122,1.096,1.089,1.092,1.098,1.114,1.130,1.137,
267 1.138,1.132,1.122,1.113,1.108,1.102 },
268 {7.970,6.080,4.442,3.398,2.872,2.127,1.672,1.451,
269 1.357,1.246,1.194,1.179,1.178,1.188,1.201,1.205,
270 1.203,1.190,1.173,1.159,1.151,1.145 },
271 {9.714,7.607,5.747,4.493,3.815,2.777,2.079,1.715,
272 1.553,1.353,1.253,1.219,1.211,1.214,1.225,1.228,
273 1.225,1.210,1.191,1.175,1.166,1.174 },
274 {17.97,12.95,8.628,6.065,4.849,3.222,2.275,1.820,
275 1.624,1.382,1.259,1.214,1.202,1.202,1.214,1.219,
276 1.217,1.203,1.184,1.169,1.160,1.151 },
277 {24.83,17.06,10.84,7.355,5.767,3.707,2.546,1.996,
278 1.759,1.465,1.311,1.252,1.234,1.228,1.238,1.241,
279 1.237,1.222,1.201,1.184,1.174,1.159 },
280 {23.26,17.15,11.52,8.049,6.375,4.114,2.792,2.155,
281 1.880,1.535,1.353,1.281,1.258,1.247,1.254,1.256,
282 1.252,1.234,1.212,1.194,1.183,1.170 },
283 {22.33,18.01,12.86,9.212,7.336,4.702,3.117,2.348,
284 2.015,1.602,1.385,1.297,1.268,1.251,1.256,1.258,
285 1.254,1.237,1.214,1.195,1.185,1.179 },
286 {33.91,24.13,15.71,10.80,8.507,5.467,3.692,2.808,
287 2.407,1.873,1.564,1.425,1.374,1.330,1.324,1.320,
288 1.312,1.288,1.258,1.235,1.221,1.205 },
289 {32.14,24.11,16.30,11.40,9.015,5.782,3.868,2.917,
290 2.490,1.925,1.596,1.447,1.391,1.342,1.332,1.327,
291 1.320,1.294,1.264,1.240,1.226,1.214 },
292 {29.51,24.07,17.19,12.28,9.766,6.238,4.112,3.066,
293 2.602,1.995,1.641,1.477,1.414,1.356,1.342,1.336,
294 1.328,1.302,1.270,1.245,1.231,1.233 },
295 {38.19,30.85,21.76,15.35,12.07,7.521,4.812,3.498,
296 2.926,2.188,1.763,1.563,1.484,1.405,1.382,1.371,
297 1.361,1.330,1.294,1.267,1.251,1.239 },
298 {49.71,39.80,27.96,19.63,15.36,9.407,5.863,4.155,
299 3.417,2.478,1.944,1.692,1.589,1.480,1.441,1.423,
300 1.409,1.372,1.330,1.298,1.280,1.258 },
301 {59.25,45.08,30.36,20.83,16.15,9.834,6.166,4.407,
302 3.641,2.648,2.064,1.779,1.661,1.531,1.482,1.459,
303 1.442,1.400,1.354,1.319,1.299,1.272 },
304 {56.38,44.29,30.50,21.18,16.51,10.11,6.354,4.542,
305 3.752,2.724,2.116,1.817,1.692,1.554,1.499,1.474,
306 1.456,1.412,1.364,1.328,1.307,1.282 }};
307
308 //data/corrections for T > Tlim
309 G4double Tlim = 10.*MeV;
310 G4double beta2lim = Tlim*(Tlim+2.*electron_mass_c2)/
311 ((Tlim+electron_mass_c2)*(Tlim+electron_mass_c2));
312 G4double bg2lim = Tlim*(Tlim+2.*electron_mass_c2)/
313 (electron_mass_c2*electron_mass_c2);
314
315 G4double sig0[15] = {0.2672*barn, 0.5922*barn, 2.653*barn, 6.235*barn,
316 11.69*barn , 13.24*barn , 16.12*barn, 23.00*barn ,
317 35.13*barn , 39.95*barn , 50.85*barn, 67.19*barn ,
318 91.15*barn , 104.4*barn , 113.1*barn};
319
320 G4double hecorr[15] = {120.70, 117.50, 105.00, 92.92, 79.23, 74.510, 68.29,
321 57.39, 41.97, 36.14, 24.53, 10.21, -7.855, -16.84,
322 -22.30};
323
324 G4double sigma;
325 SetParticle(part);
326
327 G4double Z23 = 2.*log(AtomicNumber)/3.; Z23 = exp(Z23);
328
329 // correction if particle .ne. e-/e+
330 // compute equivalent kinetic energy
331 // lambda depends on p*beta ....
332
333 G4double eKineticEnergy = KineticEnergy;
334
335 if(mass > electron_mass_c2)
336 {
337 G4double TAU = KineticEnergy/mass ;
338 G4double c = mass*TAU*(TAU+2.)/(electron_mass_c2*(TAU+1.)) ;
339 G4double w = c-2. ;
340 G4double tau = 0.5*(w+sqrt(w*w+4.*c)) ;
341 eKineticEnergy = electron_mass_c2*tau ;
342 }
343
344 G4double eTotalEnergy = eKineticEnergy + electron_mass_c2 ;
345 G4double beta2 = eKineticEnergy*(eTotalEnergy+electron_mass_c2)
346 /(eTotalEnergy*eTotalEnergy);
347 G4double bg2 = eKineticEnergy*(eTotalEnergy+electron_mass_c2)
348 /(electron_mass_c2*electron_mass_c2);
349
350 G4double eps = epsfactor*bg2/Z23;
351
352 if (eps<epsmin) sigma = 2.*eps*eps;
353 else if(eps<epsmax) sigma = log(1.+2.*eps)-2.*eps/(1.+2.*eps);
354 else sigma = log(2.*eps)-1.+1./eps;
355
356 sigma *= ChargeSquare*AtomicNumber*AtomicNumber/(beta2*bg2);
357
358 // interpolate in AtomicNumber and beta2
359 G4double c1,c2,cc1,cc2,corr;
360
361 // get bin number in Z
362 G4int iZ = 14;
363 while ((iZ>=0)&&(Zdat[iZ]>=AtomicNumber)) iZ -= 1;
364 if (iZ==14) iZ = 13;
365 if (iZ==-1) iZ = 0 ;
366
367 G4double Z1 = Zdat[iZ];
368 G4double Z2 = Zdat[iZ+1];
369 G4double ratZ = (AtomicNumber-Z1)*(AtomicNumber+Z1)/
370 ((Z2-Z1)*(Z2+Z1));
371
372 if(eKineticEnergy <= Tlim)
373 {
374 // get bin number in T (beta2)
375 G4int iT = 21;
376 while ((iT>=0)&&(Tdat[iT]>=eKineticEnergy)) iT -= 1;
377 if(iT==21) iT = 20;
378 if(iT==-1) iT = 0 ;
379
380 // calculate betasquare values
381 G4double T = Tdat[iT], E = T + electron_mass_c2;
382 G4double b2small = T*(E+electron_mass_c2)/(E*E);
383
384 T = Tdat[iT+1]; E = T + electron_mass_c2;
385 G4double b2big = T*(E+electron_mass_c2)/(E*E);
386 G4double ratb2 = (beta2-b2small)/(b2big-b2small);
387
388 if (charge < 0.)
389 {
390 c1 = celectron[iZ][iT];
391 c2 = celectron[iZ+1][iT];
392 cc1 = c1+ratZ*(c2-c1);
393
394 c1 = celectron[iZ][iT+1];
395 c2 = celectron[iZ+1][iT+1];
396 cc2 = c1+ratZ*(c2-c1);
397
398 corr = cc1+ratb2*(cc2-cc1);
399
400 sigma *= sigmafactor/corr;
401 }
402 else
403 {
404 c1 = cpositron[iZ][iT];
405 c2 = cpositron[iZ+1][iT];
406 cc1 = c1+ratZ*(c2-c1);
407
408 c1 = cpositron[iZ][iT+1];
409 c2 = cpositron[iZ+1][iT+1];
410 cc2 = c1+ratZ*(c2-c1);
411
412 corr = cc1+ratb2*(cc2-cc1);
413
414 sigma *= sigmafactor/corr;
415 }
416 }
417 else
418 {
419 c1 = bg2lim*sig0[iZ]*(1.+hecorr[iZ]*(beta2-beta2lim))/bg2;
420 c2 = bg2lim*sig0[iZ+1]*(1.+hecorr[iZ+1]*(beta2-beta2lim))/bg2;
421 if((AtomicNumber >= Z1) && (AtomicNumber <= Z2))
422 sigma = c1+ratZ*(c2-c1) ;
423 else if(AtomicNumber < Z1)
424 sigma = AtomicNumber*AtomicNumber*c1/(Z1*Z1);
425 else if(AtomicNumber > Z2)
426 sigma = AtomicNumber*AtomicNumber*c2/(Z2*Z2);
427 }
428 return sigma;
429
430}
431
432//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
433
434G4double G4UrbanMscModel::ComputeTruePathLengthLimit(
435 const G4Track& track,
436 G4PhysicsTable* theTable,
437 G4double currentMinimalStep)
438{
439 tPathLength = currentMinimalStep;
440 G4StepPoint* sp = track.GetStep()->GetPreStepPoint();
441 G4StepStatus stepStatus = sp->GetStepStatus();
442
443 const G4DynamicParticle* dp = track.GetDynamicParticle();
444
445 if(stepStatus == fUndefined) {
446 inside = false;
447 insideskin = false;
448 tlimit = geombig;
449 SetParticle( dp->GetDefinition() );
450 }
451
452 theLambdaTable = theTable;
453 couple = track.GetMaterialCutsCouple();
454 currentMaterialIndex = couple->GetIndex();
455 currentKinEnergy = dp->GetKineticEnergy();
456 currentRange =
457 theManager->GetRangeFromRestricteDEDX(particle,currentKinEnergy,couple);
458 lambda0 = GetLambda(currentKinEnergy);
459
460 // stop here if small range particle
461 if(inside) return tPathLength;
462
463 if(tPathLength > currentRange) tPathLength = currentRange;
464
465 presafety = sp->GetSafety();
466
467 // G4cout << "G4UrbanMscModel::ComputeTruePathLengthLimit tPathLength= "
468 // <<tPathLength<<" safety= " << presafety
469 // << " range= " <<currentRange<<G4endl;
470
471 // far from geometry boundary
472 if(currentRange < presafety)
473 {
474 inside = true;
475 return tPathLength;
476 }
477
478 // standard version
479 //
480 if (steppingAlgorithm == fUseDistanceToBoundary)
481 {
482 //compute geomlimit and presafety
483 G4double geomlimit = ComputeGeomLimit(track, presafety, currentRange);
484
485 // is it far from boundary ?
486 if(currentRange < presafety)
487 {
488 inside = true;
489 return tPathLength;
490 }
491
492 smallstep += 1.;
493 insideskin = false;
494
495 if((stepStatus == fGeomBoundary) || (stepStatus == fUndefined))
496 {
497 rangeinit = currentRange;
498 if(stepStatus == fUndefined) smallstep = 1.e10;
499 else smallstep = 1.;
500
501 // constraint from the geometry
502 if((geomlimit < geombig) && (geomlimit > geommin))
503 {
504 if(stepStatus == fGeomBoundary)
505 tgeom = geomlimit/facgeom;
506 else
507 tgeom = 2.*geomlimit/facgeom;
508 }
509 else
510 tgeom = geombig;
511
512 //define stepmin here (it depends on lambda!)
513 //rough estimation of lambda_elastic/lambda_transport
514 G4double rat = currentKinEnergy/MeV ;
515 rat = 1.e-3/(rat*(10.+rat)) ;
516 //stepmin ~ lambda_elastic
517 stepmin = rat*lambda0;
518 skindepth = skin*stepmin;
519
520 //define tlimitmin
521 tlimitmin = 10.*stepmin;
522 if(tlimitmin < tlimitminfix) tlimitmin = tlimitminfix;
523
524 }
525
526 //step limit
527 tlimit = facrange*rangeinit;
528 if(tlimit < facsafety*presafety)
529 tlimit = facsafety*presafety;
530
531 //lower limit for tlimit
532 if(tlimit < tlimitmin) tlimit = tlimitmin;
533
534 if(tlimit > tgeom) tlimit = tgeom;
535
536 // G4cout << "tgeom= " << tgeom << " geomlimit= " << geomlimit
537 // << " tlimit= " << tlimit << " presafety= " << presafety << G4endl;
538
539 // shortcut
540 if((tPathLength < tlimit) && (tPathLength < presafety) &&
541 (smallstep >= skin) && (tPathLength < geomlimit-0.999*skindepth))
542 return tPathLength;
543
544 // step reduction near to boundary
545 if(smallstep < skin)
546 {
547 tlimit = stepmin;
548 insideskin = true;
549 }
550 else if(geomlimit < geombig)
551 {
552 if(geomlimit > skindepth)
553 {
554 if(tlimit > geomlimit-0.999*skindepth)
555 tlimit = geomlimit-0.999*skindepth;
556 }
557 else
558 {
559 insideskin = true;
560 if(tlimit > stepmin) tlimit = stepmin;
561 }
562 }
563
564 if(tlimit < stepmin) tlimit = stepmin;
565
566 if(tPathLength > tlimit) tPathLength = tlimit ;
567
568 }
569 // for 'normal' simulation with or without magnetic field
570 // there no small step/single scattering at boundaries
571 else if(steppingAlgorithm == fUseSafety)
572 {
573 // compute presafety again if presafety <= 0 and no boundary
574 // i.e. when it is needed for optimization purposes
575 if((stepStatus != fGeomBoundary) && (presafety < tlimitminfix))
576 presafety = ComputeSafety(sp->GetPosition(),tPathLength);
577
578 // is far from boundary
579 if(currentRange < presafety)
580 {
581 inside = true;
582 return tPathLength;
583 }
584
585 if((stepStatus == fGeomBoundary) || (stepStatus == fUndefined))
586 {
587 rangeinit = currentRange;
588 fr = facrange;
589 // 9.1 like stepping for e+/e- only (not for muons,hadrons)
590 if(mass < masslimite)
591 {
592 if(lambda0 > currentRange)
593 rangeinit = lambda0;
594 if(lambda0 > lambdalimit)
595 fr *= 0.75+0.25*lambda0/lambdalimit;
596 }
597
598 //lower limit for tlimit
599 G4double rat = currentKinEnergy/MeV ;
600 rat = 1.e-3/(rat*(10.+rat)) ;
601 tlimitmin = 10.*lambda0*rat;
602 if(tlimitmin < tlimitminfix) tlimitmin = tlimitminfix;
603 }
604 //step limit
605 tlimit = fr*rangeinit;
606
607 if(tlimit < facsafety*presafety)
608 tlimit = facsafety*presafety;
609
610 //lower limit for tlimit
611 if(tlimit < tlimitmin) tlimit = tlimitmin;
612
613 if(tPathLength > tlimit) tPathLength = tlimit;
614 }
615
616 // version similar to 7.1 (needed for some experiments)
617 else
618 {
619 if (stepStatus == fGeomBoundary)
620 {
621 if (currentRange > lambda0) tlimit = facrange*currentRange;
622 else tlimit = facrange*lambda0;
623
624 if(tlimit < tlimitmin) tlimit = tlimitmin;
625 if(tPathLength > tlimit) tPathLength = tlimit;
626 }
627 }
628 // G4cout << "tPathLength= " << tPathLength << " geomlimit= " << geomlimit
629 // << " currentMinimalStep= " << currentMinimalStep << G4endl;
630 return tPathLength ;
631}
632
633//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
634
635G4double G4UrbanMscModel::ComputeGeomPathLength(G4double)
636{
637 lambdaeff = lambda0;
638 par1 = -1. ;
639 par2 = par3 = 0. ;
640
641 // do the true -> geom transformation
642 zPathLength = tPathLength;
643
644 // z = t for very small tPathLength
645 if(tPathLength < tlimitminfix) return zPathLength;
646
647 // this correction needed to run MSC with eIoni and eBrem inactivated
648 // and makes no harm for a normal run
649 if(tPathLength > currentRange)
650 tPathLength = currentRange ;
651
652 G4double tau = tPathLength/lambda0 ;
653
654 if ((tau <= tausmall) || insideskin) {
655 zPathLength = tPathLength;
656 if(zPathLength > lambda0) zPathLength = lambda0;
657 return zPathLength;
658 }
659
660 G4double zmean = tPathLength;
661 if (tPathLength < currentRange*dtrl) {
662 if(tau < taulim) zmean = tPathLength*(1.-0.5*tau) ;
663 else zmean = lambda0*(1.-exp(-tau));
664 } else if(currentKinEnergy < mass) {
665 par1 = 1./currentRange ;
666 par2 = 1./(par1*lambda0) ;
667 par3 = 1.+par2 ;
668 if(tPathLength < currentRange)
669 zmean = (1.-exp(par3*log(1.-tPathLength/currentRange)))/(par1*par3) ;
670 else
671 zmean = 1./(par1*par3) ;
672 } else {
673 G4double T1 = theManager->GetEnergy(particle,currentRange-tPathLength,couple);
674 G4double lambda1 = GetLambda(T1);
675
676 par1 = (lambda0-lambda1)/(lambda0*tPathLength) ;
677 par2 = 1./(par1*lambda0) ;
678 par3 = 1.+par2 ;
679 zmean = (1.-exp(par3*log(lambda1/lambda0)))/(par1*par3) ;
680 }
681
682 zPathLength = zmean ;
683
684 // sample z
685 if(samplez)
686 {
687 const G4double ztmax = 0.99 ;
688 G4double zt = zmean/tPathLength ;
689
690 if (tPathLength > stepmin && zt < ztmax)
691 {
692 G4double u,cz1;
693 if(zt >= third)
694 {
695 G4double cz = 0.5*(3.*zt-1.)/(1.-zt) ;
696 cz1 = 1.+cz ;
697 G4double u0 = cz/cz1 ;
698 G4double grej ;
699 do {
700 u = exp(log(G4UniformRand())/cz1) ;
701 grej = exp(cz*log(u/u0))*(1.-u)/(1.-u0) ;
702 } while (grej < G4UniformRand()) ;
703 }
704 else
705 {
706 cz1 = 1./zt-1.;
707 u = 1.-exp(log(G4UniformRand())/cz1) ;
708 }
709 zPathLength = tPathLength*u ;
710 }
711 }
712
713 if(zPathLength > lambda0) zPathLength = lambda0;
714
715 return zPathLength;
716}
717
718//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
719
720G4double G4UrbanMscModel::ComputeTrueStepLength(G4double geomStepLength)
721{
722 // step defined other than transportation
723 if(geomStepLength == zPathLength && tPathLength <= currentRange)
724 return tPathLength;
725
726 // t = z for very small step
727 zPathLength = geomStepLength;
728 tPathLength = geomStepLength;
729 if(geomStepLength < tlimitminfix) return tPathLength;
730
731 // recalculation
732 if((geomStepLength > lambda0*tausmall) && !insideskin)
733 {
734 if(par1 < 0.)
735 tPathLength = -lambda0*log(1.-geomStepLength/lambda0) ;
736 else
737 {
738 if(par1*par3*geomStepLength < 1.)
739 tPathLength = (1.-exp(log(1.-par1*par3*geomStepLength)/par3))/par1 ;
740 else
741 tPathLength = currentRange;
742 }
743 }
744 if(tPathLength < geomStepLength) tPathLength = geomStepLength;
745
746 return tPathLength;
747}
748
749//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
750
751G4double G4UrbanMscModel::ComputeTheta0(G4double trueStepLength,
752 G4double KineticEnergy)
753{
754 // for all particles take the width of the central part
755 // from a parametrization similar to the Highland formula
756 // ( Highland formula: Particle Physics Booklet, July 2002, eq. 26.10)
757 const G4double c_highland = 13.6*MeV ;
758 G4double betacp = sqrt(currentKinEnergy*(currentKinEnergy+2.*mass)*
759 KineticEnergy*(KineticEnergy+2.*mass)/
760 ((currentKinEnergy+mass)*(KineticEnergy+mass)));
761 y = trueStepLength/currentRadLength;
762 G4double theta0 = c_highland*std::abs(charge)*sqrt(y)/betacp;
763 y = log(y);
764 // correction factor from e-/proton scattering data
765 G4double corr = coeffth1+coeffth2*y;
766 if(y < -6.5) corr -= 0.011*(6.5+y);
767 theta0 *= corr ;
768
769 return theta0;
770}
771
772//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
773
774void G4UrbanMscModel::SampleScattering(const G4DynamicParticle* dynParticle,
775 G4double safety)
776{
777 G4double kineticEnergy = dynParticle->GetKineticEnergy();
778
779 if((kineticEnergy <= 0.0) || (tPathLength <= tlimitminfix) ||
780 (tPathLength/tausmall < lambda0)) return;
781
782 G4double cth = SampleCosineTheta(tPathLength,kineticEnergy);
783
784 // protection against 'bad' cth values
785 if(std::abs(cth) > 1.) return;
786
787 G4double sth = sqrt((1.0 - cth)*(1.0 + cth));
788 G4double phi = twopi*G4UniformRand();
789 G4double dirx = sth*cos(phi);
790 G4double diry = sth*sin(phi);
791
792 G4ThreeVector oldDirection = dynParticle->GetMomentumDirection();
793 G4ThreeVector newDirection(dirx,diry,cth);
794 newDirection.rotateUz(oldDirection);
795 fParticleChange->ProposeMomentumDirection(newDirection);
796
797 if (latDisplasment && safety > tlimitminfix) {
798
799 G4double r = SampleDisplacement();
800 /*
801 G4cout << "G4UrbanMscModel::SampleSecondaries: e(MeV)= " << kineticEnergy
802 << " sinTheta= " << sth << " r(mm)= " << r
803 << " trueStep(mm)= " << tPathLength
804 << " geomStep(mm)= " << zPathLength
805 << G4endl;
806 */
807 if(r > 0.)
808 {
809 G4double latcorr = LatCorrelation();
810 if(latcorr > r) latcorr = r;
811
812 // sample direction of lateral displacement
813 // compute it from the lateral correlation
814 G4double Phi = 0.;
815 if(std::abs(r*sth) < latcorr)
816 Phi = twopi*G4UniformRand();
817 else
818 {
819 G4double psi = std::acos(latcorr/(r*sth));
820 if(G4UniformRand() < 0.5)
821 Phi = phi+psi;
822 else
823 Phi = phi-psi;
824 }
825
826 dirx = std::cos(Phi);
827 diry = std::sin(Phi);
828
829 G4ThreeVector latDirection(dirx,diry,0.0);
830 latDirection.rotateUz(oldDirection);
831
832 ComputeDisplacement(fParticleChange, latDirection, r, safety);
833 }
834 }
835}
836
837//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
838
839G4double G4UrbanMscModel::SampleCosineTheta(G4double trueStepLength,
840 G4double KineticEnergy)
841{
842 G4double cth = 1. ;
843 G4double tau = trueStepLength/lambda0 ;
844
845 Zeff = couple->GetMaterial()->GetTotNbOfElectPerVolume()/
846 couple->GetMaterial()->GetTotNbOfAtomsPerVolume() ;
847
848 if(Zold != Zeff)
849 UpdateCache();
850
851 if(insideskin)
852 {
853 //no scattering, single or plural scattering
854 G4double mean = trueStepLength/stepmin ;
855
856 G4int n = G4Poisson(mean);
857 if(n > 0)
858 {
859 //screening (Moliere-Bethe)
860 G4double mom2 = KineticEnergy*(2.*mass+KineticEnergy);
861 G4double beta2 = mom2/((KineticEnergy+mass)*(KineticEnergy+mass));
862 G4double ascr = scr1/mom2;
863 ascr *= 1.13+scr2/beta2;
864 G4double ascr1 = 1.+2.*ascr;
865 G4double bp1=ascr1+1.;
866 G4double bm1=ascr1-1.;
867
868 // single scattering from screened Rutherford x-section
869 G4double ct,st,phi;
870 G4double sx=0.,sy=0.,sz=0.;
871 for(G4int i=1; i<=n; i++)
872 {
873 ct = ascr1-bp1*bm1/(2.*G4UniformRand()+bm1);
874 if(ct < -1.) ct = -1.;
875 if(ct > 1.) ct = 1.;
876 st = sqrt(1.-ct*ct);
877 phi = twopi*G4UniformRand();
878 sx += st*cos(phi);
879 sy += st*sin(phi);
880 sz += ct;
881 }
882 cth = sz/sqrt(sx*sx+sy*sy+sz*sz);
883 }
884 }
885 else
886 {
887 if(trueStepLength >= currentRange*dtrl)
888 {
889 if(par1*trueStepLength < 1.)
890 tau = -par2*log(1.-par1*trueStepLength) ;
891 // for the case if ioni/brems are inactivated
892 // see the corresponding condition in ComputeGeomPathLength
893 else if(1.-KineticEnergy/currentKinEnergy > taulim)
894 tau = taubig ;
895 }
896 currentTau = tau ;
897 lambdaeff = trueStepLength/currentTau;
898 currentRadLength = couple->GetMaterial()->GetRadlen();
899
900 if (tau >= taubig) cth = -1.+2.*G4UniformRand();
901 else if (tau >= tausmall)
902 {
903 G4double xsi = 3.0;
904 G4double x0 = 1.;
905 G4double a = 1., ea = 0., eaa = 1.;
906 G4double b=2.,b1=3.,bx=1.,eb1=3.,ebx=1.;
907 G4double prob = 1. , qprob = 1. ;
908 G4double xmean1 = 1., xmean2 = 0.;
909 G4double xmeanth = exp(-tau);
910 G4double x2meanth = (1.+2.*exp(-2.5*tau))/3.;
911
912 G4double relloss = 1.-KineticEnergy/currentKinEnergy;
913 if(relloss > rellossmax)
914 return SimpleScattering(xmeanth,x2meanth);
915
916 G4double theta0 = ComputeTheta0(trueStepLength,KineticEnergy);
917
918 // protection for very small angles
919 if(theta0 < tausmall) return cth;
920
921 if(theta0 > theta0max)
922 return SimpleScattering(xmeanth,x2meanth);
923 G4double sth = sin(0.5*theta0);
924 a = 0.25/(sth*sth);
925
926 ea = exp(-xsi);
927 eaa = 1.-ea ;
928 xmean1 = 1.-(1.-(1.+xsi)*ea)/(a*eaa);
929 x0 = 1.-xsi/a;
930
931 if(xmean1 <= 0.999*xmeanth)
932 return SimpleScattering(xmeanth,x2meanth);
933
934 // from MUSCAT H,Be,Fe data
935 G4double c = coeffc1;
936 if(y > -13.5)
937 c += coeffc2*exp(3.*log(y+13.5));
938
939 if(abs(c-3.) < 0.001) c = 3.001;
940 if(abs(c-2.) < 0.001) c = 2.001;
941
942 G4double c1 = c-1.;
943
944 //from continuity of derivatives
945 b = 1.+(c-xsi)/a;
946
947 b1 = b+1.;
948 bx = c/a;
949 eb1 = exp(c1*log(b1));
950 ebx = exp(c1*log(bx));
951
952 xmean2 = (x0*eb1+ebx-(eb1*bx-b1*ebx)/(c-2.))/(eb1-ebx);
953
954 G4double f1x0 = a*ea/eaa;
955 G4double f2x0 = c1*eb1/(bx*(eb1-ebx));
956 prob = f2x0/(f1x0+f2x0);
957
958 qprob = xmeanth/(prob*xmean1+(1.-prob)*xmean2);
959
960 // sampling of costheta
961 if(G4UniformRand() < qprob)
962 {
963 if(G4UniformRand() < prob)
964 cth = 1.+log(ea+G4UniformRand()*eaa)/a ;
965 else
966 cth = b-b1*bx/exp(log(ebx+(eb1-ebx)*G4UniformRand())/c1) ;
967 }
968 else
969 cth = -1.+2.*G4UniformRand();
970 }
971 }
972 return cth ;
973}
974
975//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
976
977G4double G4UrbanMscModel::SimpleScattering(G4double xmeanth,G4double x2meanth)
978{
979 // 'large angle scattering'
980 // 2 model functions with correct xmean and x2mean
981 G4double a = (2.*xmeanth+9.*x2meanth-3.)/(2.*xmeanth-3.*x2meanth+1.);
982 G4double prob = (a+2.)*xmeanth/a;
983
984 // sampling
985 G4double cth = 1.;
986 if(G4UniformRand() < prob)
987 cth = -1.+2.*exp(log(G4UniformRand())/(a+1.));
988 else
989 cth = -1.+2.*G4UniformRand();
990 return cth;
991}
992
993//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
994
995G4double G4UrbanMscModel::SampleDisplacement()
996{
997 const G4double kappa = 2.5;
998 const G4double kappapl1 = kappa+1.;
999 const G4double kappami1 = kappa-1.;
1000 G4double rmean = 0.0;
1001 if ((currentTau >= tausmall) && !insideskin) {
1002 if (currentTau < taulim) {
1003 rmean = kappa*currentTau*currentTau*currentTau*
1004 (1.-kappapl1*currentTau*0.25)/6. ;
1005
1006 } else {
1007 G4double etau = 0.0;
1008 if (currentTau<taubig) etau = exp(-currentTau);
1009 rmean = -kappa*currentTau;
1010 rmean = -exp(rmean)/(kappa*kappami1);
1011 rmean += currentTau-kappapl1/kappa+kappa*etau/kappami1;
1012 }
1013 if (rmean>0.) rmean = 2.*lambdaeff*sqrt(rmean/3.0);
1014 else rmean = 0.;
1015 }
1016
1017 // protection against z > t ...........................
1018 if(rmean > 0.) {
1019 G4double zt = (tPathLength-zPathLength)*(tPathLength+zPathLength);
1020 if(zt <= 0.)
1021 rmean = 0.;
1022 else if(rmean*rmean > zt)
1023 rmean = sqrt(zt);
1024 }
1025 return rmean;
1026}
1027
1028//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
1029
1030G4double G4UrbanMscModel::LatCorrelation()
1031{
1032 const G4double kappa = 2.5;
1033 const G4double kappami1 = kappa-1.;
1034
1035 G4double latcorr = 0.;
1036 if((currentTau >= tausmall) && !insideskin)
1037 {
1038 if(currentTau < taulim)
1039 latcorr = lambdaeff*kappa*currentTau*currentTau*
1040 (1.-(kappa+1.)*currentTau/3.)/3.;
1041 else
1042 {
1043 G4double etau = 0.;
1044 if(currentTau < taubig) etau = exp(-currentTau);
1045 latcorr = -kappa*currentTau;
1046 latcorr = exp(latcorr)/kappami1;
1047 latcorr += 1.-kappa*etau/kappami1 ;
1048 latcorr *= 2.*lambdaeff/3. ;
1049 }
1050 }
1051
1052 return latcorr;
1053}
1054
1055//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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