source: trunk/source/processes/electromagnetic/standard/src/G4UrbanMscModel93.cc@ 1330

Last change on this file since 1330 was 1315, checked in by garnier, 15 years ago

update geant4-09-04-beta-cand-01 interfaces-V09-03-09 vis-V09-03-08
File size: 36.6 KB
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24// ********************************************************************
25//
26//
27// $Id: G4UrbanMscModel93.cc,v 1.4 2010/05/20 13:17:25 vnivanch Exp $
28// GEANT4 tag $Name: geant4-09-04-beta-cand-01 $
29//
30// -------------------------------------------------------------------
31//
32// GEANT4 Class file
33//
34//
35// File name: G4UrbanMscModel93
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 G4UrbanMscModel2 to G4UrbanMscModel93,
88// now it is a frozen version of the Urban model corresponding
89// to g4 9.3
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 "G4UrbanMscModel93.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
118G4UrbanMscModel93::G4UrbanMscModel93(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
172G4UrbanMscModel93::~G4UrbanMscModel93()
173{}
174
175//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
176
177void G4UrbanMscModel93::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 G4UrbanMscModel93::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 G4UrbanMscModel93::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 << "G4Urban2::StepLimit tPathLength= "
469 // <<tPathLength<<" safety= " << presafety
470 // << " range= " <<currentRange<< " lambda= "<<lambda0
471 // << " Alg: " << steppingAlgorithm <<G4endl;
472
473 // far from geometry boundary
474 if(currentRange < presafety)
475 {
476 inside = true;
477 return tPathLength;
478 }
479
480 // standard version
481 //
482 if (steppingAlgorithm == fUseDistanceToBoundary)
483 {
484 //compute geomlimit and presafety
485 G4double geomlimit = ComputeGeomLimit(track, presafety, currentRange);
486
487 // is it far from boundary ?
488 if(currentRange < presafety)
489 {
490 inside = true;
491 return tPathLength;
492 }
493
494 smallstep += 1.;
495 insideskin = false;
496
497 if((stepStatus == fGeomBoundary) || (stepStatus == fUndefined))
498 {
499 rangeinit = currentRange;
500 if(stepStatus == fUndefined) smallstep = 1.e10;
501 else smallstep = 1.;
502
503 //define stepmin here (it depends on lambda!)
504 //rough estimation of lambda_elastic/lambda_transport
505 G4double rat = currentKinEnergy/MeV ;
506 rat = 1.e-3/(rat*(10.+rat)) ;
507 //stepmin ~ lambda_elastic
508 stepmin = rat*lambda0;
509 skindepth = skin*stepmin;
510 //define tlimitmin
511 tlimitmin = 10.*stepmin;
512 if(tlimitmin < tlimitminfix) tlimitmin = tlimitminfix;
513 //G4cout << "rangeinit= " << rangeinit << " stepmin= " << stepmin
514 // << " tlimitmin= " << tlimitmin << " geomlimit= " << geomlimit <<G4endl;
515 // constraint from the geometry
516 if((geomlimit < geombig) && (geomlimit > geommin))
517 {
518 // geomlimit is a geometrical step length
519 // transform it to true path length (estimation)
520 if((1.-geomlimit/lambda0) > 0.)
521 geomlimit = -lambda0*log(1.-geomlimit/lambda0)+tlimitmin ;
522
523 if(stepStatus == fGeomBoundary)
524 tgeom = geomlimit/facgeom;
525 else
526 tgeom = 2.*geomlimit/facgeom;
527 }
528 else
529 tgeom = geombig;
530 }
531
532
533 //step limit
534 tlimit = facrange*rangeinit;
535 if(tlimit < facsafety*presafety)
536 tlimit = facsafety*presafety;
537
538 //lower limit for tlimit
539 if(tlimit < tlimitmin) tlimit = tlimitmin;
540
541 if(tlimit > tgeom) tlimit = tgeom;
542
543 //G4cout << "tgeom= " << tgeom << " geomlimit= " << geomlimit
544 // << " tlimit= " << tlimit << " presafety= " << presafety << G4endl;
545
546 // shortcut
547 if((tPathLength < tlimit) && (tPathLength < presafety) &&
548 (smallstep >= skin) && (tPathLength < geomlimit-0.999*skindepth))
549 return tPathLength;
550
551 // step reduction near to boundary
552 if(smallstep < skin)
553 {
554 tlimit = stepmin;
555 insideskin = true;
556 }
557 else if(geomlimit < geombig)
558 {
559 if(geomlimit > skindepth)
560 {
561 if(tlimit > geomlimit-0.999*skindepth)
562 tlimit = geomlimit-0.999*skindepth;
563 }
564 else
565 {
566 insideskin = true;
567 if(tlimit > stepmin) tlimit = stepmin;
568 }
569 }
570
571 if(tlimit < stepmin) tlimit = stepmin;
572
573 // randomize 1st step or 1st 'normal' step in volume
574 if((stepStatus == fUndefined) ||
575 ((smallstep == skin) && !insideskin))
576 {
577 G4double temptlimit = tlimit;
578 if(temptlimit > tlimitmin)
579 {
580 do {
581 temptlimit = G4RandGauss::shoot(tlimit,0.3*tlimit);
582 } while ((temptlimit < tlimitmin) ||
583 (temptlimit > 2.*tlimit-tlimitmin));
584 }
585 else
586 temptlimit = tlimitmin;
587 if(tPathLength > temptlimit) tPathLength = temptlimit;
588 }
589 else
590 {
591 if(tPathLength > tlimit) tPathLength = tlimit ;
592 }
593
594 }
595 // for 'normal' simulation with or without magnetic field
596 // there no small step/single scattering at boundaries
597 else if(steppingAlgorithm == fUseSafety)
598 {
599 // compute presafety again if presafety <= 0 and no boundary
600 // i.e. when it is needed for optimization purposes
601 if((stepStatus != fGeomBoundary) && (presafety < tlimitminfix))
602 presafety = ComputeSafety(sp->GetPosition(),tPathLength);
603
604 // is far from boundary
605 if(currentRange < presafety)
606 {
607 inside = true;
608 return tPathLength;
609 }
610
611 if((stepStatus == fGeomBoundary) || (stepStatus == fUndefined))
612 {
613 rangeinit = currentRange;
614 fr = facrange;
615 // 9.1 like stepping for e+/e- only (not for muons,hadrons)
616 if(mass < masslimite)
617 {
618 if(lambda0 > currentRange)
619 rangeinit = lambda0;
620 if(lambda0 > lambdalimit)
621 fr *= 0.75+0.25*lambda0/lambdalimit;
622 }
623
624 //lower limit for tlimit
625 G4double rat = currentKinEnergy/MeV ;
626 rat = 1.e-3/(rat*(10.+rat)) ;
627 tlimitmin = 10.*lambda0*rat;
628 if(tlimitmin < tlimitminfix) tlimitmin = tlimitminfix;
629 }
630 //step limit
631 tlimit = fr*rangeinit;
632
633 if(tlimit < facsafety*presafety)
634 tlimit = facsafety*presafety;
635
636 //lower limit for tlimit
637 if(tlimit < tlimitmin) tlimit = tlimitmin;
638
639 if(tPathLength > tlimit) tPathLength = tlimit;
640
641 }
642
643 // version similar to 7.1 (needed for some experiments)
644 else
645 {
646 if (stepStatus == fGeomBoundary)
647 {
648 if (currentRange > lambda0) tlimit = facrange*currentRange;
649 else tlimit = facrange*lambda0;
650
651 if(tlimit < tlimitmin) tlimit = tlimitmin;
652 if(tPathLength > tlimit) tPathLength = tlimit;
653 }
654 }
655 //G4cout << "tPathLength= " << tPathLength
656 // << " currentMinimalStep= " << currentMinimalStep << G4endl;
657 return tPathLength ;
658}
659
660//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
661
662G4double G4UrbanMscModel93::ComputeGeomPathLength(G4double)
663{
664 lambdaeff = lambda0;
665 par1 = -1. ;
666 par2 = par3 = 0. ;
667
668 // do the true -> geom transformation
669 zPathLength = tPathLength;
670
671 // z = t for very small tPathLength
672 if(tPathLength < tlimitminfix) return zPathLength;
673
674 // this correction needed to run MSC with eIoni and eBrem inactivated
675 // and makes no harm for a normal run
676 if(tPathLength > currentRange)
677 tPathLength = currentRange ;
678
679 G4double tau = tPathLength/lambda0 ;
680
681 if ((tau <= tausmall) || insideskin) {
682 zPathLength = tPathLength;
683 if(zPathLength > lambda0) zPathLength = lambda0;
684 return zPathLength;
685 }
686
687 G4double zmean = tPathLength;
688 if (tPathLength < currentRange*dtrl) {
689 if(tau < taulim) zmean = tPathLength*(1.-0.5*tau) ;
690 else zmean = lambda0*(1.-exp(-tau));
691 } else if(currentKinEnergy < mass) {
692 par1 = 1./currentRange ;
693 par2 = 1./(par1*lambda0) ;
694 par3 = 1.+par2 ;
695 if(tPathLength < currentRange)
696 zmean = (1.-exp(par3*log(1.-tPathLength/currentRange)))/(par1*par3) ;
697 else
698 zmean = 1./(par1*par3) ;
699 } else {
700 G4double T1 = theManager->GetEnergy(particle,currentRange-tPathLength,couple);
701 G4double lambda1 = GetLambda(T1);
702
703 par1 = (lambda0-lambda1)/(lambda0*tPathLength) ;
704 par2 = 1./(par1*lambda0) ;
705 par3 = 1.+par2 ;
706 zmean = (1.-exp(par3*log(lambda1/lambda0)))/(par1*par3) ;
707 }
708
709 zPathLength = zmean ;
710
711 // sample z
712 if(samplez)
713 {
714 const G4double ztmax = 0.99 ;
715 G4double zt = zmean/tPathLength ;
716
717 if (tPathLength > stepmin && zt < ztmax)
718 {
719 G4double u,cz1;
720 if(zt >= third)
721 {
722 G4double cz = 0.5*(3.*zt-1.)/(1.-zt) ;
723 cz1 = 1.+cz ;
724 G4double u0 = cz/cz1 ;
725 G4double grej ;
726 do {
727 u = exp(log(G4UniformRand())/cz1) ;
728 grej = exp(cz*log(u/u0))*(1.-u)/(1.-u0) ;
729 } while (grej < G4UniformRand()) ;
730 }
731 else
732 {
733 cz1 = 1./zt-1.;
734 u = 1.-exp(log(G4UniformRand())/cz1) ;
735 }
736 zPathLength = tPathLength*u ;
737 }
738 }
739
740 if(zPathLength > lambda0) zPathLength = lambda0;
741 //G4cout << "zPathLength= " << zPathLength << " lambda1= " << lambda0 << G4endl;
742 return zPathLength;
743}
744
745//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
746
747G4double G4UrbanMscModel93::ComputeTrueStepLength(G4double geomStepLength)
748{
749 // step defined other than transportation
750 if(geomStepLength == zPathLength && tPathLength <= currentRange)
751 return tPathLength;
752
753 // t = z for very small step
754 zPathLength = geomStepLength;
755 tPathLength = geomStepLength;
756 if(geomStepLength < tlimitminfix) return tPathLength;
757
758 // recalculation
759 if((geomStepLength > lambda0*tausmall) && !insideskin)
760 {
761 if(par1 < 0.)
762 tPathLength = -lambda0*log(1.-geomStepLength/lambda0) ;
763 else
764 {
765 if(par1*par3*geomStepLength < 1.)
766 tPathLength = (1.-exp(log(1.-par1*par3*geomStepLength)/par3))/par1 ;
767 else
768 tPathLength = currentRange;
769 }
770 }
771 if(tPathLength < geomStepLength) tPathLength = geomStepLength;
772 //G4cout << "tPathLength= " << tPathLength << " step= " << geomStepLength << G4endl;
773
774 return tPathLength;
775}
776
777//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
778
779G4double G4UrbanMscModel93::ComputeTheta0(G4double trueStepLength,
780 G4double KineticEnergy)
781{
782 // for all particles take the width of the central part
783 // from a parametrization similar to the Highland formula
784 // ( Highland formula: Particle Physics Booklet, July 2002, eq. 26.10)
785 const G4double c_highland = 13.6*MeV ;
786 G4double betacp = sqrt(currentKinEnergy*(currentKinEnergy+2.*mass)*
787 KineticEnergy*(KineticEnergy+2.*mass)/
788 ((currentKinEnergy+mass)*(KineticEnergy+mass)));
789 y = trueStepLength/currentRadLength;
790 G4double theta0 = c_highland*std::abs(charge)*sqrt(y)/betacp;
791 y = log(y);
792 // correction factor from e- scattering data
793 G4double corr = coeffth1+coeffth2*y;
794
795 theta0 *= corr ;
796
797 return theta0;
798}
799
800//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
801
802void G4UrbanMscModel93::SampleScattering(const G4DynamicParticle* dynParticle,
803 G4double safety)
804{
805 G4double kineticEnergy = dynParticle->GetKineticEnergy();
806
807 if((kineticEnergy <= 0.0) || (tPathLength <= tlimitminfix) ||
808 (tPathLength/tausmall < lambda0)) return;
809
810 G4double cth = SampleCosineTheta(tPathLength,kineticEnergy);
811
812 // protection against 'bad' cth values
813 if(std::abs(cth) > 1.) return;
814
815 G4double sth = sqrt((1.0 - cth)*(1.0 + cth));
816 G4double phi = twopi*G4UniformRand();
817 G4double dirx = sth*cos(phi);
818 G4double diry = sth*sin(phi);
819
820 G4ThreeVector oldDirection = dynParticle->GetMomentumDirection();
821 G4ThreeVector newDirection(dirx,diry,cth);
822 newDirection.rotateUz(oldDirection);
823 fParticleChange->ProposeMomentumDirection(newDirection);
824
825 if (latDisplasment && safety > tlimitminfix) {
826
827 G4double r = SampleDisplacement();
828 /*
829 G4cout << "G4UrbanMscModel93::SampleSecondaries: e(MeV)= " << kineticEnergy
830 << " sinTheta= " << sth << " r(mm)= " << r
831 << " trueStep(mm)= " << tPathLength
832 << " geomStep(mm)= " << zPathLength
833 << G4endl;
834 */
835 if(r > 0.)
836 {
837 G4double latcorr = LatCorrelation();
838 if(latcorr > r) latcorr = r;
839
840 // sample direction of lateral displacement
841 // compute it from the lateral correlation
842 G4double Phi = 0.;
843 if(std::abs(r*sth) < latcorr)
844 Phi = twopi*G4UniformRand();
845 else
846 {
847 G4double psi = std::acos(latcorr/(r*sth));
848 if(G4UniformRand() < 0.5)
849 Phi = phi+psi;
850 else
851 Phi = phi-psi;
852 }
853
854 dirx = std::cos(Phi);
855 diry = std::sin(Phi);
856
857 G4ThreeVector latDirection(dirx,diry,0.0);
858 latDirection.rotateUz(oldDirection);
859
860 ComputeDisplacement(fParticleChange, latDirection, r, safety);
861 }
862 }
863}
864
865//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
866
867G4double G4UrbanMscModel93::SampleCosineTheta(G4double trueStepLength,
868 G4double KineticEnergy)
869{
870 G4double cth = 1. ;
871 G4double tau = trueStepLength/lambda0 ;
872
873 Zeff = couple->GetMaterial()->GetTotNbOfElectPerVolume()/
874 couple->GetMaterial()->GetTotNbOfAtomsPerVolume() ;
875
876 if(Zold != Zeff)
877 UpdateCache();
878
879 if(insideskin)
880 {
881 //no scattering, single or plural scattering
882 G4double mean = trueStepLength/stepmin ;
883
884 G4int n = G4Poisson(mean);
885 if(n > 0)
886 {
887 //screening (Moliere-Bethe)
888 G4double mom2 = KineticEnergy*(2.*mass+KineticEnergy);
889 G4double beta2 = mom2/((KineticEnergy+mass)*(KineticEnergy+mass));
890 G4double ascr = scr1/mom2;
891 ascr *= 1.13+scr2/beta2;
892 G4double ascr1 = 1.+2.*ascr;
893 G4double bp1=ascr1+1.;
894 G4double bm1=ascr1-1.;
895
896 // single scattering from screened Rutherford x-section
897 G4double ct,st,phi;
898 G4double sx=0.,sy=0.,sz=0.;
899 for(G4int i=1; i<=n; i++)
900 {
901 ct = ascr1-bp1*bm1/(2.*G4UniformRand()+bm1);
902 if(ct < -1.) ct = -1.;
903 if(ct > 1.) ct = 1.;
904 st = sqrt(1.-ct*ct);
905 phi = twopi*G4UniformRand();
906 sx += st*cos(phi);
907 sy += st*sin(phi);
908 sz += ct;
909 }
910 cth = sz/sqrt(sx*sx+sy*sy+sz*sz);
911 }
912 }
913 else
914 {
915 if(trueStepLength >= currentRange*dtrl)
916 {
917 if(par1*trueStepLength < 1.)
918 tau = -par2*log(1.-par1*trueStepLength) ;
919 // for the case if ioni/brems are inactivated
920 // see the corresponding condition in ComputeGeomPathLength
921 else if(1.-KineticEnergy/currentKinEnergy > taulim)
922 tau = taubig ;
923 }
924 currentTau = tau ;
925 lambdaeff = trueStepLength/currentTau;
926 currentRadLength = couple->GetMaterial()->GetRadlen();
927
928 if (tau >= taubig) cth = -1.+2.*G4UniformRand();
929 else if (tau >= tausmall)
930 {
931 G4double xsi = 3.;
932 G4double x0 = 1.;
933 G4double a = 1., ea = 0., eaa = 1.;
934 G4double b=2.,b1=3.,bx=1.,eb1=3.,ebx=1.;
935 G4double prob = 1. , qprob = 1. ;
936 G4double xmean1 = 1., xmean2 = 0.;
937 G4double xmeanth = exp(-tau);
938 G4double x2meanth = (1.+2.*exp(-2.5*tau))/3.;
939
940 G4double relloss = 1.-KineticEnergy/currentKinEnergy;
941 if(relloss > rellossmax)
942 return SimpleScattering(xmeanth,x2meanth);
943
944 G4double theta0 = ComputeTheta0(trueStepLength,KineticEnergy);
945
946 // protection for very small angles
947 if(theta0 < tausmall) return cth;
948
949 if(theta0 > theta0max)
950 return SimpleScattering(xmeanth,x2meanth);
951 G4double sth = sin(0.5*theta0);
952 a = 0.25/(sth*sth);
953
954 ea = exp(-xsi);
955 eaa = 1.-ea ;
956 xmean1 = 1.-(1.-(1.+xsi)*ea)/(a*eaa);
957 x0 = 1.-xsi/a;
958
959 if(xmean1 <= 0.999*xmeanth)
960 return SimpleScattering(xmeanth,x2meanth);
961
962 // from e- and muon scattering data
963 G4double c = coeffc1+coeffc2*y; ;
964
965 if(abs(c-3.) < 0.001) c = 3.001;
966 if(abs(c-2.) < 0.001) c = 2.001;
967 if(abs(c-1.) < 0.001) c = 1.001;
968
969 G4double c1 = c-1.;
970
971 //from continuity of derivatives
972 b = 1.+(c-xsi)/a;
973
974 b1 = b+1.;
975 bx = c/a;
976 eb1 = exp(c1*log(b1));
977 ebx = exp(c1*log(bx));
978
979 xmean2 = (x0*eb1+ebx-(eb1*bx-b1*ebx)/(c-2.))/(eb1-ebx);
980
981 G4double f1x0 = a*ea/eaa;
982 G4double f2x0 = c1*eb1/(bx*(eb1-ebx));
983 prob = f2x0/(f1x0+f2x0);
984
985 qprob = xmeanth/(prob*xmean1+(1.-prob)*xmean2);
986
987 // sampling of costheta
988 if(G4UniformRand() < qprob)
989 {
990 if(G4UniformRand() < prob)
991 cth = 1.+log(ea+G4UniformRand()*eaa)/a ;
992 else
993 cth = b-b1*bx/exp(log(ebx+(eb1-ebx)*G4UniformRand())/c1) ;
994 }
995 else
996 cth = -1.+2.*G4UniformRand();
997 }
998 }
999 return cth ;
1000}
1001
1002//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
1003
1004G4double G4UrbanMscModel93::SimpleScattering(G4double xmeanth,G4double x2meanth)
1005{
1006 // 'large angle scattering'
1007 // 2 model functions with correct xmean and x2mean
1008 G4double a = (2.*xmeanth+9.*x2meanth-3.)/(2.*xmeanth-3.*x2meanth+1.);
1009 G4double prob = (a+2.)*xmeanth/a;
1010
1011 // sampling
1012 G4double cth = 1.;
1013 if(G4UniformRand() < prob)
1014 cth = -1.+2.*exp(log(G4UniformRand())/(a+1.));
1015 else
1016 cth = -1.+2.*G4UniformRand();
1017 return cth;
1018}
1019
1020//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
1021
1022G4double G4UrbanMscModel93::SampleDisplacement()
1023{
1024 // compute rmean = sqrt(<r**2>) from theory
1025 const G4double kappa = 2.5;
1026 const G4double kappapl1 = kappa+1.;
1027 const G4double kappami1 = kappa-1.;
1028 // Compute rmean = sqrt(<r**2>) from theory
1029 G4double rmean = 0.0;
1030 if ((currentTau >= tausmall) && !insideskin) {
1031 if (currentTau < taulim) {
1032 rmean = kappa*currentTau*currentTau*currentTau*
1033 (1.-kappapl1*currentTau*0.25)/6. ;
1034
1035 } else {
1036 G4double etau = 0.0;
1037 if (currentTau<taubig) etau = exp(-currentTau);
1038 rmean = -kappa*currentTau;
1039 rmean = -exp(rmean)/(kappa*kappami1);
1040 rmean += currentTau-kappapl1/kappa+kappa*etau/kappami1;
1041 }
1042 if (rmean>0.) rmean = 2.*lambdaeff*sqrt(rmean/3.0);
1043 else rmean = 0.;
1044 }
1045
1046 if(rmean == 0.) return rmean;
1047
1048 // protection against z > t ...........................
1049 G4double rmax = (tPathLength-zPathLength)*(tPathLength+zPathLength);
1050 if(rmax <= 0.)
1051 rmax = 0.;
1052 else
1053 rmax = sqrt(rmax);
1054
1055 if(rmean >= rmax) return rmax;
1056
1057 return rmean;
1058 // VI comment out for the time being
1059 /*
1060 //sample r (Gaussian distribution with a mean of rmean )
1061 G4double r = 0.;
1062 G4double sigma = min(rmean,rmax-rmean);
1063 sigma /= 3.;
1064 G4double rlow = rmean-3.*sigma;
1065 G4double rhigh = rmean+3.*sigma;
1066 do {
1067 r = G4RandGauss::shoot(rmean,sigma);
1068 } while ((r < rlow) || (r > rhigh));
1069
1070 return r;
1071 */
1072}
1073
1074//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
1075
1076G4double G4UrbanMscModel93::LatCorrelation()
1077{
1078 const G4double kappa = 2.5;
1079 const G4double kappami1 = kappa-1.;
1080
1081 G4double latcorr = 0.;
1082 if((currentTau >= tausmall) && !insideskin)
1083 {
1084 if(currentTau < taulim)
1085 latcorr = lambdaeff*kappa*currentTau*currentTau*
1086 (1.-(kappa+1.)*currentTau/3.)/3.;
1087 else
1088 {
1089 G4double etau = 0.;
1090 if(currentTau < taubig) etau = exp(-currentTau);
1091 latcorr = -kappa*currentTau;
1092 latcorr = exp(latcorr)/kappami1;
1093 latcorr += 1.-kappa*etau/kappami1 ;
1094 latcorr *= 2.*lambdaeff/3. ;
1095 }
1096 }
1097
1098 return latcorr;
1099}
1100
1101//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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