source: trunk/source/processes/electromagnetic/standard/src/G4UrbanMscModel92.cc@ 1199

Last change on this file since 1199 was 1197, checked in by garnier, 16 years ago

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[1197]1//
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25//
26//
27// $Id: G4UrbanMscModel92.cc,v 1.1 2009/11/01 13:05:01 vnivanch Exp $
28// GEANT4 tag $Name: geant4-09-03-cand-01 $
29//
30// -------------------------------------------------------------------
31//
32// GEANT4 Class file
33//
34//
35// File name: G4UrbanMscModel92
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// 28-10-09 V.Ivanchenko moved G4UrbanMscModel to G4UrbanMscModel92,
88// now it is a frozen version of the Urban model corresponding
89// to g4 9.2
90
91// Class Description:
92//
93// Implementation of the model of multiple scattering based on
94// H.W.Lewis Phys Rev 78 (1950) 526 and others
95
96// -------------------------------------------------------------------
97// In its present form the model can be used for simulation
98// of the e-/e+, muon and charged hadron multiple scattering
99//
100
101
102//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
103//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
104
105#include "G4UrbanMscModel92.hh"
106#include "Randomize.hh"
107#include "G4Electron.hh"
108#include "G4LossTableManager.hh"
109#include "G4ParticleChangeForMSC.hh"
110
111#include "G4Poisson.hh"
112#include "globals.hh"
113
114//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
115
116using namespace std;
117
118G4UrbanMscModel92::G4UrbanMscModel92(const G4String& nam)
119 : G4VMscModel(nam),
120 isInitialized(false)
121{
122 masslimite = 0.6*MeV;
123 lambdalimit = 1.*mm;
124 fr = 0.02;
125 // facsafety = 0.3;
126 taubig = 8.0;
127 tausmall = 1.e-16;
128 taulim = 1.e-6;
129 currentTau = taulim;
130 tlimitminfix = 1.e-6*mm;
131 stepmin = tlimitminfix;
132 smallstep = 1.e10;
133 currentRange = 0. ;
134 rangeinit = 0.;
135 tlimit = 1.e10*mm;
136 tlimitmin = 10.*tlimitminfix;
137 tgeom = 1.e50*mm;
138 geombig = 1.e50*mm;
139 geommin = 1.e-3*mm;
140 geomlimit = geombig;
141 presafety = 0.*mm;
142
143 y = 0.;
144
145 Zold = 0.;
146 Zeff = 1.;
147 Z2 = 1.;
148 Z23 = 1.;
149 lnZ = 0.;
150 coeffth1 = 0.;
151 coeffth2 = 0.;
152 coeffc1 = 0.;
153 coeffc2 = 0.;
154 scr1ini = fine_structure_const*fine_structure_const*
155 electron_mass_c2*electron_mass_c2/(0.885*0.885*4.*pi);
156 scr2ini = 3.76*fine_structure_const*fine_structure_const;
157 scr1 = 0.;
158 scr2 = 0.;
159
160 theta0max = pi/6.;
161 rellossmax = 0.50;
162 third = 1./3.;
163 particle = 0;
164 theManager = G4LossTableManager::Instance();
165 inside = false;
166 insideskin = false;
167
168}
169
170//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
171
172G4UrbanMscModel92::~G4UrbanMscModel92()
173{}
174
175//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
176
177void G4UrbanMscModel92::Initialise(const G4ParticleDefinition* p,
178 const G4DataVector&)
179{
180 skindepth = skin*stepmin;
181 if(isInitialized) return;
182 // set values of some data members
183 SetParticle(p);
184
185 fParticleChange = GetParticleChangeForMSC();
186 InitialiseSafetyHelper();
187
188 isInitialized = true;
189}
190
191//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
192
193G4double G4UrbanMscModel92::ComputeCrossSectionPerAtom(
194 const G4ParticleDefinition* part,
195 G4double KineticEnergy,
196 G4double AtomicNumber,G4double,
197 G4double, G4double)
198{
199 const G4double sigmafactor = twopi*classic_electr_radius*classic_electr_radius;
200 const G4double epsfactor = 2.*electron_mass_c2*electron_mass_c2*
201 Bohr_radius*Bohr_radius/(hbarc*hbarc);
202 const G4double epsmin = 1.e-4 , epsmax = 1.e10;
203
204 const G4double Zdat[15] = { 4., 6., 13., 20., 26., 29., 32., 38., 47.,
205 50., 56., 64., 74., 79., 82. };
206
207 const G4double Tdat[22] = { 100*eV, 200*eV, 400*eV, 700*eV,
208 1*keV, 2*keV, 4*keV, 7*keV,
209 10*keV, 20*keV, 40*keV, 70*keV,
210 100*keV, 200*keV, 400*keV, 700*keV,
211 1*MeV, 2*MeV, 4*MeV, 7*MeV,
212 10*MeV, 20*MeV};
213
214 // corr. factors for e-/e+ lambda for T <= Tlim
215 G4double celectron[15][22] =
216 {{1.125,1.072,1.051,1.047,1.047,1.050,1.052,1.054,
217 1.054,1.057,1.062,1.069,1.075,1.090,1.105,1.111,
218 1.112,1.108,1.100,1.093,1.089,1.087 },
219 {1.408,1.246,1.143,1.096,1.077,1.059,1.053,1.051,
220 1.052,1.053,1.058,1.065,1.072,1.087,1.101,1.108,
221 1.109,1.105,1.097,1.090,1.086,1.082 },
222 {2.833,2.268,1.861,1.612,1.486,1.309,1.204,1.156,
223 1.136,1.114,1.106,1.106,1.109,1.119,1.129,1.132,
224 1.131,1.124,1.113,1.104,1.099,1.098 },
225 {3.879,3.016,2.380,2.007,1.818,1.535,1.340,1.236,
226 1.190,1.133,1.107,1.099,1.098,1.103,1.110,1.113,
227 1.112,1.105,1.096,1.089,1.085,1.098 },
228 {6.937,4.330,2.886,2.256,1.987,1.628,1.395,1.265,
229 1.203,1.122,1.080,1.065,1.061,1.063,1.070,1.073,
230 1.073,1.070,1.064,1.059,1.056,1.056 },
231 {9.616,5.708,3.424,2.551,2.204,1.762,1.485,1.330,
232 1.256,1.155,1.099,1.077,1.070,1.068,1.072,1.074,
233 1.074,1.070,1.063,1.059,1.056,1.052 },
234 {11.72,6.364,3.811,2.806,2.401,1.884,1.564,1.386,
235 1.300,1.180,1.112,1.082,1.073,1.066,1.068,1.069,
236 1.068,1.064,1.059,1.054,1.051,1.050 },
237 {18.08,8.601,4.569,3.183,2.662,2.025,1.646,1.439,
238 1.339,1.195,1.108,1.068,1.053,1.040,1.039,1.039,
239 1.039,1.037,1.034,1.031,1.030,1.036 },
240 {18.22,10.48,5.333,3.713,3.115,2.367,1.898,1.631,
241 1.498,1.301,1.171,1.105,1.077,1.048,1.036,1.033,
242 1.031,1.028,1.024,1.022,1.021,1.024 },
243 {14.14,10.65,5.710,3.929,3.266,2.453,1.951,1.669,
244 1.528,1.319,1.178,1.106,1.075,1.040,1.027,1.022,
245 1.020,1.017,1.015,1.013,1.013,1.020 },
246 {14.11,11.73,6.312,4.240,3.478,2.566,2.022,1.720,
247 1.569,1.342,1.186,1.102,1.065,1.022,1.003,0.997,
248 0.995,0.993,0.993,0.993,0.993,1.011 },
249 {22.76,20.01,8.835,5.287,4.144,2.901,2.219,1.855,
250 1.677,1.410,1.224,1.121,1.073,1.014,0.986,0.976,
251 0.974,0.972,0.973,0.974,0.975,0.987 },
252 {50.77,40.85,14.13,7.184,5.284,3.435,2.520,2.059,
253 1.837,1.512,1.283,1.153,1.091,1.010,0.969,0.954,
254 0.950,0.947,0.949,0.952,0.954,0.963 },
255 {65.87,59.06,15.87,7.570,5.567,3.650,2.682,2.182,
256 1.939,1.579,1.325,1.178,1.108,1.014,0.965,0.947,
257 0.941,0.938,0.940,0.944,0.946,0.954 },
258 {55.60,47.34,15.92,7.810,5.755,3.767,2.760,2.239,
259 1.985,1.609,1.343,1.188,1.113,1.013,0.960,0.939,
260 0.933,0.930,0.933,0.936,0.939,0.949 }};
261
262 G4double cpositron[15][22] = {
263 {2.589,2.044,1.658,1.446,1.347,1.217,1.144,1.110,
264 1.097,1.083,1.080,1.086,1.092,1.108,1.123,1.131,
265 1.131,1.126,1.117,1.108,1.103,1.100 },
266 {3.904,2.794,2.079,1.710,1.543,1.325,1.202,1.145,
267 1.122,1.096,1.089,1.092,1.098,1.114,1.130,1.137,
268 1.138,1.132,1.122,1.113,1.108,1.102 },
269 {7.970,6.080,4.442,3.398,2.872,2.127,1.672,1.451,
270 1.357,1.246,1.194,1.179,1.178,1.188,1.201,1.205,
271 1.203,1.190,1.173,1.159,1.151,1.145 },
272 {9.714,7.607,5.747,4.493,3.815,2.777,2.079,1.715,
273 1.553,1.353,1.253,1.219,1.211,1.214,1.225,1.228,
274 1.225,1.210,1.191,1.175,1.166,1.174 },
275 {17.97,12.95,8.628,6.065,4.849,3.222,2.275,1.820,
276 1.624,1.382,1.259,1.214,1.202,1.202,1.214,1.219,
277 1.217,1.203,1.184,1.169,1.160,1.151 },
278 {24.83,17.06,10.84,7.355,5.767,3.707,2.546,1.996,
279 1.759,1.465,1.311,1.252,1.234,1.228,1.238,1.241,
280 1.237,1.222,1.201,1.184,1.174,1.159 },
281 {23.26,17.15,11.52,8.049,6.375,4.114,2.792,2.155,
282 1.880,1.535,1.353,1.281,1.258,1.247,1.254,1.256,
283 1.252,1.234,1.212,1.194,1.183,1.170 },
284 {22.33,18.01,12.86,9.212,7.336,4.702,3.117,2.348,
285 2.015,1.602,1.385,1.297,1.268,1.251,1.256,1.258,
286 1.254,1.237,1.214,1.195,1.185,1.179 },
287 {33.91,24.13,15.71,10.80,8.507,5.467,3.692,2.808,
288 2.407,1.873,1.564,1.425,1.374,1.330,1.324,1.320,
289 1.312,1.288,1.258,1.235,1.221,1.205 },
290 {32.14,24.11,16.30,11.40,9.015,5.782,3.868,2.917,
291 2.490,1.925,1.596,1.447,1.391,1.342,1.332,1.327,
292 1.320,1.294,1.264,1.240,1.226,1.214 },
293 {29.51,24.07,17.19,12.28,9.766,6.238,4.112,3.066,
294 2.602,1.995,1.641,1.477,1.414,1.356,1.342,1.336,
295 1.328,1.302,1.270,1.245,1.231,1.233 },
296 {38.19,30.85,21.76,15.35,12.07,7.521,4.812,3.498,
297 2.926,2.188,1.763,1.563,1.484,1.405,1.382,1.371,
298 1.361,1.330,1.294,1.267,1.251,1.239 },
299 {49.71,39.80,27.96,19.63,15.36,9.407,5.863,4.155,
300 3.417,2.478,1.944,1.692,1.589,1.480,1.441,1.423,
301 1.409,1.372,1.330,1.298,1.280,1.258 },
302 {59.25,45.08,30.36,20.83,16.15,9.834,6.166,4.407,
303 3.641,2.648,2.064,1.779,1.661,1.531,1.482,1.459,
304 1.442,1.400,1.354,1.319,1.299,1.272 },
305 {56.38,44.29,30.50,21.18,16.51,10.11,6.354,4.542,
306 3.752,2.724,2.116,1.817,1.692,1.554,1.499,1.474,
307 1.456,1.412,1.364,1.328,1.307,1.282 }};
308
309 //data/corrections for T > Tlim
310 G4double Tlim = 10.*MeV;
311 G4double beta2lim = Tlim*(Tlim+2.*electron_mass_c2)/
312 ((Tlim+electron_mass_c2)*(Tlim+electron_mass_c2));
313 G4double bg2lim = Tlim*(Tlim+2.*electron_mass_c2)/
314 (electron_mass_c2*electron_mass_c2);
315
316 G4double sig0[15] = {0.2672*barn, 0.5922*barn, 2.653*barn, 6.235*barn,
317 11.69*barn , 13.24*barn , 16.12*barn, 23.00*barn ,
318 35.13*barn , 39.95*barn , 50.85*barn, 67.19*barn ,
319 91.15*barn , 104.4*barn , 113.1*barn};
320
321 G4double hecorr[15] = {120.70, 117.50, 105.00, 92.92, 79.23, 74.510, 68.29,
322 57.39, 41.97, 36.14, 24.53, 10.21, -7.855, -16.84,
323 -22.30};
324
325 G4double sigma;
326 SetParticle(part);
327
328 G4double Z23 = 2.*log(AtomicNumber)/3.; Z23 = exp(Z23);
329
330 // correction if particle .ne. e-/e+
331 // compute equivalent kinetic energy
332 // lambda depends on p*beta ....
333
334 G4double eKineticEnergy = KineticEnergy;
335
336 if(mass > electron_mass_c2)
337 {
338 G4double TAU = KineticEnergy/mass ;
339 G4double c = mass*TAU*(TAU+2.)/(electron_mass_c2*(TAU+1.)) ;
340 G4double w = c-2. ;
341 G4double tau = 0.5*(w+sqrt(w*w+4.*c)) ;
342 eKineticEnergy = electron_mass_c2*tau ;
343 }
344
345 G4double eTotalEnergy = eKineticEnergy + electron_mass_c2 ;
346 G4double beta2 = eKineticEnergy*(eTotalEnergy+electron_mass_c2)
347 /(eTotalEnergy*eTotalEnergy);
348 G4double bg2 = eKineticEnergy*(eTotalEnergy+electron_mass_c2)
349 /(electron_mass_c2*electron_mass_c2);
350
351 G4double eps = epsfactor*bg2/Z23;
352
353 if (eps<epsmin) sigma = 2.*eps*eps;
354 else if(eps<epsmax) sigma = log(1.+2.*eps)-2.*eps/(1.+2.*eps);
355 else sigma = log(2.*eps)-1.+1./eps;
356
357 sigma *= ChargeSquare*AtomicNumber*AtomicNumber/(beta2*bg2);
358
359 // interpolate in AtomicNumber and beta2
360 G4double c1,c2,cc1,cc2,corr;
361
362 // get bin number in Z
363 G4int iZ = 14;
364 while ((iZ>=0)&&(Zdat[iZ]>=AtomicNumber)) iZ -= 1;
365 if (iZ==14) iZ = 13;
366 if (iZ==-1) iZ = 0 ;
367
368 G4double Z1 = Zdat[iZ];
369 G4double Z2 = Zdat[iZ+1];
370 G4double ratZ = (AtomicNumber-Z1)*(AtomicNumber+Z1)/
371 ((Z2-Z1)*(Z2+Z1));
372
373 if(eKineticEnergy <= Tlim)
374 {
375 // get bin number in T (beta2)
376 G4int iT = 21;
377 while ((iT>=0)&&(Tdat[iT]>=eKineticEnergy)) iT -= 1;
378 if(iT==21) iT = 20;
379 if(iT==-1) iT = 0 ;
380
381 // calculate betasquare values
382 G4double T = Tdat[iT], E = T + electron_mass_c2;
383 G4double b2small = T*(E+electron_mass_c2)/(E*E);
384
385 T = Tdat[iT+1]; E = T + electron_mass_c2;
386 G4double b2big = T*(E+electron_mass_c2)/(E*E);
387 G4double ratb2 = (beta2-b2small)/(b2big-b2small);
388
389 if (charge < 0.)
390 {
391 c1 = celectron[iZ][iT];
392 c2 = celectron[iZ+1][iT];
393 cc1 = c1+ratZ*(c2-c1);
394
395 c1 = celectron[iZ][iT+1];
396 c2 = celectron[iZ+1][iT+1];
397 cc2 = c1+ratZ*(c2-c1);
398
399 corr = cc1+ratb2*(cc2-cc1);
400
401 sigma *= sigmafactor/corr;
402 }
403 else
404 {
405 c1 = cpositron[iZ][iT];
406 c2 = cpositron[iZ+1][iT];
407 cc1 = c1+ratZ*(c2-c1);
408
409 c1 = cpositron[iZ][iT+1];
410 c2 = cpositron[iZ+1][iT+1];
411 cc2 = c1+ratZ*(c2-c1);
412
413 corr = cc1+ratb2*(cc2-cc1);
414
415 sigma *= sigmafactor/corr;
416 }
417 }
418 else
419 {
420 c1 = bg2lim*sig0[iZ]*(1.+hecorr[iZ]*(beta2-beta2lim))/bg2;
421 c2 = bg2lim*sig0[iZ+1]*(1.+hecorr[iZ+1]*(beta2-beta2lim))/bg2;
422 if((AtomicNumber >= Z1) && (AtomicNumber <= Z2))
423 sigma = c1+ratZ*(c2-c1) ;
424 else if(AtomicNumber < Z1)
425 sigma = AtomicNumber*AtomicNumber*c1/(Z1*Z1);
426 else if(AtomicNumber > Z2)
427 sigma = AtomicNumber*AtomicNumber*c2/(Z2*Z2);
428 }
429 return sigma;
430
431}
432
433//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
434
435G4double G4UrbanMscModel92::ComputeTruePathLengthLimit(
436 const G4Track& track,
437 G4PhysicsTable* theTable,
438 G4double currentMinimalStep)
439{
440 tPathLength = currentMinimalStep;
441 G4StepPoint* sp = track.GetStep()->GetPreStepPoint();
442 G4StepStatus stepStatus = sp->GetStepStatus();
443
444 const G4DynamicParticle* dp = track.GetDynamicParticle();
445
446 if(stepStatus == fUndefined) {
447 inside = false;
448 insideskin = false;
449 tlimit = geombig;
450 SetParticle( dp->GetDefinition() );
451 }
452
453 theLambdaTable = theTable;
454 couple = track.GetMaterialCutsCouple();
455 currentMaterialIndex = couple->GetIndex();
456 currentKinEnergy = dp->GetKineticEnergy();
457 currentRange =
458 theManager->GetRangeFromRestricteDEDX(particle,currentKinEnergy,couple);
459 lambda0 = GetLambda(currentKinEnergy);
460
461 // stop here if small range particle
462 if(inside) return tPathLength;
463
464 if(tPathLength > currentRange) tPathLength = currentRange;
465
466 presafety = sp->GetSafety();
467
468 // G4cout << "G4UrbanMscModel92::ComputeTruePathLengthLimit tPathLength= "
469 // <<tPathLength<<" safety= " << presafety
470 // << " range= " <<currentRange<<G4endl;
471
472 // far from geometry boundary
473 if(currentRange < presafety)
474 {
475 inside = true;
476 return tPathLength;
477 }
478
479 // standard version
480 //
481 if (steppingAlgorithm == fUseDistanceToBoundary)
482 {
483 //compute geomlimit and presafety
484 G4double geomlimit = ComputeGeomLimit(track, presafety, currentRange);
485
486 // is it far from boundary ?
487 if(currentRange < presafety)
488 {
489 inside = true;
490 return tPathLength;
491 }
492
493 smallstep += 1.;
494 insideskin = false;
495
496 if((stepStatus == fGeomBoundary) || (stepStatus == fUndefined))
497 {
498 rangeinit = currentRange;
499 if(stepStatus == fUndefined) smallstep = 1.e10;
500 else smallstep = 1.;
501
502 // constraint from the geometry
503 if((geomlimit < geombig) && (geomlimit > geommin))
504 {
505 if(stepStatus == fGeomBoundary)
506 tgeom = geomlimit/facgeom;
507 else
508 tgeom = 2.*geomlimit/facgeom;
509 }
510 else
511 tgeom = geombig;
512
513 //define stepmin here (it depends on lambda!)
514 //rough estimation of lambda_elastic/lambda_transport
515 G4double rat = currentKinEnergy/MeV ;
516 rat = 1.e-3/(rat*(10.+rat)) ;
517 //stepmin ~ lambda_elastic
518 stepmin = rat*lambda0;
519 skindepth = skin*stepmin;
520
521 //define tlimitmin
522 tlimitmin = 10.*stepmin;
523 if(tlimitmin < tlimitminfix) tlimitmin = tlimitminfix;
524
525 }
526
527 //step limit
528 tlimit = facrange*rangeinit;
529 if(tlimit < facsafety*presafety)
530 tlimit = facsafety*presafety;
531
532 //lower limit for tlimit
533 if(tlimit < tlimitmin) tlimit = tlimitmin;
534
535 if(tlimit > tgeom) tlimit = tgeom;
536
537 // G4cout << "tgeom= " << tgeom << " geomlimit= " << geomlimit
538 // << " tlimit= " << tlimit << " presafety= " << presafety << G4endl;
539
540 // shortcut
541 if((tPathLength < tlimit) && (tPathLength < presafety) &&
542 (smallstep >= skin) && (tPathLength < geomlimit-0.999*skindepth))
543 return tPathLength;
544
545 // step reduction near to boundary
546 if(smallstep < skin)
547 {
548 tlimit = stepmin;
549 insideskin = true;
550 }
551 else if(geomlimit < geombig)
552 {
553 if(geomlimit > skindepth)
554 {
555 if(tlimit > geomlimit-0.999*skindepth)
556 tlimit = geomlimit-0.999*skindepth;
557 }
558 else
559 {
560 insideskin = true;
561 if(tlimit > stepmin) tlimit = stepmin;
562 }
563 }
564
565 if(tlimit < stepmin) tlimit = stepmin;
566
567 if(tPathLength > tlimit) tPathLength = tlimit ;
568
569 }
570 // for 'normal' simulation with or without magnetic field
571 // there no small step/single scattering at boundaries
572 else if(steppingAlgorithm == fUseSafety)
573 {
574 // compute presafety again if presafety <= 0 and no boundary
575 // i.e. when it is needed for optimization purposes
576 if((stepStatus != fGeomBoundary) && (presafety < tlimitminfix))
577 presafety = ComputeSafety(sp->GetPosition(),tPathLength);
578
579 // is far from boundary
580 if(currentRange < presafety)
581 {
582 inside = true;
583 return tPathLength;
584 }
585
586 if((stepStatus == fGeomBoundary) || (stepStatus == fUndefined))
587 {
588 rangeinit = currentRange;
589 fr = facrange;
590 // 9.1 like stepping for e+/e- only (not for muons,hadrons)
591 if(mass < masslimite)
592 {
593 if(lambda0 > currentRange)
594 rangeinit = lambda0;
595 if(lambda0 > lambdalimit)
596 fr *= 0.75+0.25*lambda0/lambdalimit;
597 }
598
599 //lower limit for tlimit
600 G4double rat = currentKinEnergy/MeV ;
601 rat = 1.e-3/(rat*(10.+rat)) ;
602 tlimitmin = 10.*lambda0*rat;
603 if(tlimitmin < tlimitminfix) tlimitmin = tlimitminfix;
604 }
605 //step limit
606 tlimit = fr*rangeinit;
607
608 if(tlimit < facsafety*presafety)
609 tlimit = facsafety*presafety;
610
611 //lower limit for tlimit
612 if(tlimit < tlimitmin) tlimit = tlimitmin;
613
614 if(tPathLength > tlimit) tPathLength = tlimit;
615 }
616
617 // version similar to 7.1 (needed for some experiments)
618 else
619 {
620 if (stepStatus == fGeomBoundary)
621 {
622 if (currentRange > lambda0) tlimit = facrange*currentRange;
623 else tlimit = facrange*lambda0;
624
625 if(tlimit < tlimitmin) tlimit = tlimitmin;
626 if(tPathLength > tlimit) tPathLength = tlimit;
627 }
628 }
629 // G4cout << "tPathLength= " << tPathLength << " geomlimit= " << geomlimit
630 // << " currentMinimalStep= " << currentMinimalStep << G4endl;
631 return tPathLength ;
632}
633
634//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
635
636G4double G4UrbanMscModel92::ComputeGeomPathLength(G4double)
637{
638 lambdaeff = lambda0;
639 par1 = -1. ;
640 par2 = par3 = 0. ;
641
642 // do the true -> geom transformation
643 zPathLength = tPathLength;
644
645 // z = t for very small tPathLength
646 if(tPathLength < tlimitminfix) return zPathLength;
647
648 // this correction needed to run MSC with eIoni and eBrem inactivated
649 // and makes no harm for a normal run
650 if(tPathLength > currentRange)
651 tPathLength = currentRange ;
652
653 G4double tau = tPathLength/lambda0 ;
654
655 if ((tau <= tausmall) || insideskin) {
656 zPathLength = tPathLength;
657 if(zPathLength > lambda0) zPathLength = lambda0;
658 return zPathLength;
659 }
660
661 G4double zmean = tPathLength;
662 if (tPathLength < currentRange*dtrl) {
663 if(tau < taulim) zmean = tPathLength*(1.-0.5*tau) ;
664 else zmean = lambda0*(1.-exp(-tau));
665 } else if(currentKinEnergy < mass) {
666 par1 = 1./currentRange ;
667 par2 = 1./(par1*lambda0) ;
668 par3 = 1.+par2 ;
669 if(tPathLength < currentRange)
670 zmean = (1.-exp(par3*log(1.-tPathLength/currentRange)))/(par1*par3) ;
671 else
672 zmean = 1./(par1*par3) ;
673 } else {
674 G4double T1 = theManager->GetEnergy(particle,currentRange-tPathLength,couple);
675 G4double lambda1 = GetLambda(T1);
676
677 par1 = (lambda0-lambda1)/(lambda0*tPathLength) ;
678 par2 = 1./(par1*lambda0) ;
679 par3 = 1.+par2 ;
680 zmean = (1.-exp(par3*log(lambda1/lambda0)))/(par1*par3) ;
681 }
682
683 zPathLength = zmean ;
684
685 // sample z
686 if(samplez)
687 {
688 const G4double ztmax = 0.99 ;
689 G4double zt = zmean/tPathLength ;
690
691 if (tPathLength > stepmin && zt < ztmax)
692 {
693 G4double u,cz1;
694 if(zt >= third)
695 {
696 G4double cz = 0.5*(3.*zt-1.)/(1.-zt) ;
697 cz1 = 1.+cz ;
698 G4double u0 = cz/cz1 ;
699 G4double grej ;
700 do {
701 u = exp(log(G4UniformRand())/cz1) ;
702 grej = exp(cz*log(u/u0))*(1.-u)/(1.-u0) ;
703 } while (grej < G4UniformRand()) ;
704 }
705 else
706 {
707 cz1 = 1./zt-1.;
708 u = 1.-exp(log(G4UniformRand())/cz1) ;
709 }
710 zPathLength = tPathLength*u ;
711 }
712 }
713
714 if(zPathLength > lambda0) zPathLength = lambda0;
715
716 return zPathLength;
717}
718
719//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
720
721G4double G4UrbanMscModel92::ComputeTrueStepLength(G4double geomStepLength)
722{
723 // step defined other than transportation
724 if(geomStepLength == zPathLength && tPathLength <= currentRange)
725 return tPathLength;
726
727 // t = z for very small step
728 zPathLength = geomStepLength;
729 tPathLength = geomStepLength;
730 if(geomStepLength < tlimitminfix) return tPathLength;
731
732 // recalculation
733 if((geomStepLength > lambda0*tausmall) && !insideskin)
734 {
735 if(par1 < 0.)
736 tPathLength = -lambda0*log(1.-geomStepLength/lambda0) ;
737 else
738 {
739 if(par1*par3*geomStepLength < 1.)
740 tPathLength = (1.-exp(log(1.-par1*par3*geomStepLength)/par3))/par1 ;
741 else
742 tPathLength = currentRange;
743 }
744 }
745 if(tPathLength < geomStepLength) tPathLength = geomStepLength;
746
747 return tPathLength;
748}
749
750//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
751
752G4double G4UrbanMscModel92::ComputeTheta0(G4double trueStepLength,
753 G4double KineticEnergy)
754{
755 // for all particles take the width of the central part
756 // from a parametrization similar to the Highland formula
757 // ( Highland formula: Particle Physics Booklet, July 2002, eq. 26.10)
758 const G4double c_highland = 13.6*MeV ;
759 G4double betacp = sqrt(currentKinEnergy*(currentKinEnergy+2.*mass)*
760 KineticEnergy*(KineticEnergy+2.*mass)/
761 ((currentKinEnergy+mass)*(KineticEnergy+mass)));
762 y = trueStepLength/currentRadLength;
763 G4double theta0 = c_highland*std::abs(charge)*sqrt(y)/betacp;
764 y = log(y);
765 // correction factor from e-/proton scattering data
766 G4double corr = coeffth1+coeffth2*y;
767 if(y < -6.5) corr -= 0.011*(6.5+y);
768 theta0 *= corr ;
769
770 return theta0;
771}
772
773//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
774
775void G4UrbanMscModel92::SampleScattering(const G4DynamicParticle* dynParticle,
776 G4double safety)
777{
778 G4double kineticEnergy = dynParticle->GetKineticEnergy();
779
780 if((kineticEnergy <= 0.0) || (tPathLength <= tlimitminfix) ||
781 (tPathLength/tausmall < lambda0)) return;
782
783 G4double cth = SampleCosineTheta(tPathLength,kineticEnergy);
784
785 // protection against 'bad' cth values
786 if(std::abs(cth) > 1.) return;
787
788 G4double sth = sqrt((1.0 - cth)*(1.0 + cth));
789 G4double phi = twopi*G4UniformRand();
790 G4double dirx = sth*cos(phi);
791 G4double diry = sth*sin(phi);
792
793 G4ThreeVector oldDirection = dynParticle->GetMomentumDirection();
794 G4ThreeVector newDirection(dirx,diry,cth);
795 newDirection.rotateUz(oldDirection);
796 fParticleChange->ProposeMomentumDirection(newDirection);
797
798 if (latDisplasment && safety > tlimitminfix) {
799
800 G4double r = SampleDisplacement();
801 /*
802 G4cout << "G4UrbanMscModel92::SampleSecondaries: e(MeV)= " << kineticEnergy
803 << " sinTheta= " << sth << " r(mm)= " << r
804 << " trueStep(mm)= " << tPathLength
805 << " geomStep(mm)= " << zPathLength
806 << G4endl;
807 */
808 if(r > 0.)
809 {
810 G4double latcorr = LatCorrelation();
811 if(latcorr > r) latcorr = r;
812
813 // sample direction of lateral displacement
814 // compute it from the lateral correlation
815 G4double Phi = 0.;
816 if(std::abs(r*sth) < latcorr)
817 Phi = twopi*G4UniformRand();
818 else
819 {
820 G4double psi = std::acos(latcorr/(r*sth));
821 if(G4UniformRand() < 0.5)
822 Phi = phi+psi;
823 else
824 Phi = phi-psi;
825 }
826
827 dirx = std::cos(Phi);
828 diry = std::sin(Phi);
829
830 G4ThreeVector latDirection(dirx,diry,0.0);
831 latDirection.rotateUz(oldDirection);
832
833 ComputeDisplacement(fParticleChange, latDirection, r, safety);
834 }
835 }
836}
837
838//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
839
840G4double G4UrbanMscModel92::SampleCosineTheta(G4double trueStepLength,
841 G4double KineticEnergy)
842{
843 G4double cth = 1. ;
844 G4double tau = trueStepLength/lambda0 ;
845
846 Zeff = couple->GetMaterial()->GetTotNbOfElectPerVolume()/
847 couple->GetMaterial()->GetTotNbOfAtomsPerVolume() ;
848
849 if(Zold != Zeff)
850 UpdateCache();
851
852 if(insideskin)
853 {
854 //no scattering, single or plural scattering
855 G4double mean = trueStepLength/stepmin ;
856
857 G4int n = G4Poisson(mean);
858 if(n > 0)
859 {
860 //screening (Moliere-Bethe)
861 G4double mom2 = KineticEnergy*(2.*mass+KineticEnergy);
862 G4double beta2 = mom2/((KineticEnergy+mass)*(KineticEnergy+mass));
863 G4double ascr = scr1/mom2;
864 ascr *= 1.13+scr2/beta2;
865 G4double ascr1 = 1.+2.*ascr;
866 G4double bp1=ascr1+1.;
867 G4double bm1=ascr1-1.;
868
869 // single scattering from screened Rutherford x-section
870 G4double ct,st,phi;
871 G4double sx=0.,sy=0.,sz=0.;
872 for(G4int i=1; i<=n; i++)
873 {
874 ct = ascr1-bp1*bm1/(2.*G4UniformRand()+bm1);
875 if(ct < -1.) ct = -1.;
876 if(ct > 1.) ct = 1.;
877 st = sqrt(1.-ct*ct);
878 phi = twopi*G4UniformRand();
879 sx += st*cos(phi);
880 sy += st*sin(phi);
881 sz += ct;
882 }
883 cth = sz/sqrt(sx*sx+sy*sy+sz*sz);
884 }
885 }
886 else
887 {
888 if(trueStepLength >= currentRange*dtrl)
889 {
890 if(par1*trueStepLength < 1.)
891 tau = -par2*log(1.-par1*trueStepLength) ;
892 // for the case if ioni/brems are inactivated
893 // see the corresponding condition in ComputeGeomPathLength
894 else if(1.-KineticEnergy/currentKinEnergy > taulim)
895 tau = taubig ;
896 }
897 currentTau = tau ;
898 lambdaeff = trueStepLength/currentTau;
899 currentRadLength = couple->GetMaterial()->GetRadlen();
900
901 if (tau >= taubig) cth = -1.+2.*G4UniformRand();
902 else if (tau >= tausmall)
903 {
904 G4double xsi = 3.0;
905 G4double x0 = 1.;
906 G4double a = 1., ea = 0., eaa = 1.;
907 G4double b=2.,b1=3.,bx=1.,eb1=3.,ebx=1.;
908 G4double prob = 1. , qprob = 1. ;
909 G4double xmean1 = 1., xmean2 = 0.;
910 G4double xmeanth = exp(-tau);
911 G4double x2meanth = (1.+2.*exp(-2.5*tau))/3.;
912
913 G4double relloss = 1.-KineticEnergy/currentKinEnergy;
914 if(relloss > rellossmax)
915 return SimpleScattering(xmeanth,x2meanth);
916
917 G4double theta0 = ComputeTheta0(trueStepLength,KineticEnergy);
918
919 // protection for very small angles
920 if(theta0 < tausmall) return cth;
921
922 if(theta0 > theta0max)
923 return SimpleScattering(xmeanth,x2meanth);
924 G4double sth = sin(0.5*theta0);
925 a = 0.25/(sth*sth);
926
927 ea = exp(-xsi);
928 eaa = 1.-ea ;
929 xmean1 = 1.-(1.-(1.+xsi)*ea)/(a*eaa);
930 x0 = 1.-xsi/a;
931
932 if(xmean1 <= 0.999*xmeanth)
933 return SimpleScattering(xmeanth,x2meanth);
934
935 // from MUSCAT H,Be,Fe data
936 G4double c = coeffc1;
937 if(y > -13.5)
938 c += coeffc2*exp(3.*log(y+13.5));
939
940 if(abs(c-3.) < 0.001) c = 3.001;
941 if(abs(c-2.) < 0.001) c = 2.001;
942
943 G4double c1 = c-1.;
944
945 //from continuity of derivatives
946 b = 1.+(c-xsi)/a;
947
948 b1 = b+1.;
949 bx = c/a;
950 eb1 = exp(c1*log(b1));
951 ebx = exp(c1*log(bx));
952
953 xmean2 = (x0*eb1+ebx-(eb1*bx-b1*ebx)/(c-2.))/(eb1-ebx);
954
955 G4double f1x0 = a*ea/eaa;
956 G4double f2x0 = c1*eb1/(bx*(eb1-ebx));
957 prob = f2x0/(f1x0+f2x0);
958
959 qprob = xmeanth/(prob*xmean1+(1.-prob)*xmean2);
960
961 // sampling of costheta
962 if(G4UniformRand() < qprob)
963 {
964 if(G4UniformRand() < prob)
965 cth = 1.+log(ea+G4UniformRand()*eaa)/a ;
966 else
967 cth = b-b1*bx/exp(log(ebx+(eb1-ebx)*G4UniformRand())/c1) ;
968 }
969 else
970 cth = -1.+2.*G4UniformRand();
971 }
972 }
973 return cth ;
974}
975
976//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
977
978G4double G4UrbanMscModel92::SimpleScattering(G4double xmeanth,G4double x2meanth)
979{
980 // 'large angle scattering'
981 // 2 model functions with correct xmean and x2mean
982 G4double a = (2.*xmeanth+9.*x2meanth-3.)/(2.*xmeanth-3.*x2meanth+1.);
983 G4double prob = (a+2.)*xmeanth/a;
984
985 // sampling
986 G4double cth = 1.;
987 if(G4UniformRand() < prob)
988 cth = -1.+2.*exp(log(G4UniformRand())/(a+1.));
989 else
990 cth = -1.+2.*G4UniformRand();
991 return cth;
992}
993
994//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
995
996G4double G4UrbanMscModel92::SampleDisplacement()
997{
998 const G4double kappa = 2.5;
999 const G4double kappapl1 = kappa+1.;
1000 const G4double kappami1 = kappa-1.;
1001 G4double rmean = 0.0;
1002 if ((currentTau >= tausmall) && !insideskin) {
1003 if (currentTau < taulim) {
1004 rmean = kappa*currentTau*currentTau*currentTau*
1005 (1.-kappapl1*currentTau*0.25)/6. ;
1006
1007 } else {
1008 G4double etau = 0.0;
1009 if (currentTau<taubig) etau = exp(-currentTau);
1010 rmean = -kappa*currentTau;
1011 rmean = -exp(rmean)/(kappa*kappami1);
1012 rmean += currentTau-kappapl1/kappa+kappa*etau/kappami1;
1013 }
1014 if (rmean>0.) rmean = 2.*lambdaeff*sqrt(rmean/3.0);
1015 else rmean = 0.;
1016 }
1017
1018 // protection against z > t ...........................
1019 if(rmean > 0.) {
1020 G4double zt = (tPathLength-zPathLength)*(tPathLength+zPathLength);
1021 if(zt <= 0.)
1022 rmean = 0.;
1023 else if(rmean*rmean > zt)
1024 rmean = sqrt(zt);
1025 }
1026 return rmean;
1027}
1028
1029//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
1030
1031G4double G4UrbanMscModel92::LatCorrelation()
1032{
1033 const G4double kappa = 2.5;
1034 const G4double kappami1 = kappa-1.;
1035
1036 G4double latcorr = 0.;
1037 if((currentTau >= tausmall) && !insideskin)
1038 {
1039 if(currentTau < taulim)
1040 latcorr = lambdaeff*kappa*currentTau*currentTau*
1041 (1.-(kappa+1.)*currentTau/3.)/3.;
1042 else
1043 {
1044 G4double etau = 0.;
1045 if(currentTau < taubig) etau = exp(-currentTau);
1046 latcorr = -kappa*currentTau;
1047 latcorr = exp(latcorr)/kappami1;
1048 latcorr += 1.-kappa*etau/kappami1 ;
1049 latcorr *= 2.*lambdaeff/3. ;
1050 }
1051 }
1052
1053 return latcorr;
1054}
1055
1056//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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