source: trunk/source/processes/electromagnetic/standard/src/G4UrbanMscModel90.cc @ 1316

Last change on this file since 1316 was 1228, checked in by garnier, 14 years ago

update geant4.9.3 tag
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25//
26// $Id: G4UrbanMscModel90.cc,v 1.13 2009/04/10 18:10:58 vnivanch Exp $
27// GEANT4 tag $Name: geant4-09-03 $
28//
29// -------------------------------------------------------------------
30//
31// GEANT4 Class file
32//
33//
34// File name:   G4UrbanMscModel90
35//
36// Author:        V.Ivanchenko clone Laszlo Urban model
37//
38// Creation date: 07.12.2007
39//
40// Modifications:
41//
42//
43
44// Class Description:
45//
46// Implementation of the model of multiple scattering based on
47// H.W.Lewis Phys Rev 78 (1950) 526 and others
48
49// -------------------------------------------------------------------
50//
51
52
53//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
54//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
55
56#include "G4UrbanMscModel90.hh"
57#include "Randomize.hh"
58#include "G4Electron.hh"
59
60#include "G4LossTableManager.hh"
61#include "G4ParticleChangeForMSC.hh"
62
63#include "G4Poisson.hh"
64
65//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
66
67using namespace std;
68
69G4UrbanMscModel90::G4UrbanMscModel90(const G4String& nam)
70  : G4VMscModel(nam),
71    isInitialized(false)
72{
73  taubig        = 8.0;
74  tausmall      = 1.e-20;
75  taulim        = 1.e-6;
76  currentTau    = taulim;
77  tlimitminfix  = 1.e-6*mm;           
78  stepmin       = tlimitminfix;
79  smallstep     = 1.e10;
80  currentRange  = 0. ;
81  frscaling2    = 0.25;
82  frscaling1    = 1.-frscaling2;
83  tlimit        = 1.e10*mm;
84  tlimitmin     = 10.*tlimitminfix;           
85  nstepmax      = 25.;
86  geombig       = 1.e50*mm;
87  geommin       = 1.e-3*mm;
88  geomlimit     = geombig;
89  presafety     = 0.*mm;
90  Zeff          = 1.;
91  particle      = 0;
92  theManager    = G4LossTableManager::Instance(); 
93  inside        = false; 
94  insideskin    = false;
95}
96
97//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
98
99G4UrbanMscModel90::~G4UrbanMscModel90()
100{}
101
102//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
103
104void G4UrbanMscModel90::Initialise(const G4ParticleDefinition* p,
105                                   const G4DataVector&)
106{
107  skindepth     = skin*stepmin;
108  if(isInitialized) return;
109
110  // set values of some data members
111  SetParticle(p);
112
113  fParticleChange = GetParticleChangeForMSC();
114  InitialiseSafetyHelper();
115
116  isInitialized = true;
117}
118
119//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
120
121G4double G4UrbanMscModel90::ComputeCrossSectionPerAtom( 
122                             const G4ParticleDefinition* part,
123                                   G4double KineticEnergy,
124                                   G4double AtomicNumber,G4double,
125                                   G4double, G4double)
126{
127  const G4double sigmafactor = twopi*classic_electr_radius*classic_electr_radius;
128  const G4double epsfactor = 2.*electron_mass_c2*electron_mass_c2*
129                            Bohr_radius*Bohr_radius/(hbarc*hbarc);
130  const G4double epsmin = 1.e-4 , epsmax = 1.e10;
131
132  const G4double Zdat[15] = { 4.,  6., 13., 20., 26., 29., 32., 38., 47.,
133                             50., 56., 64., 74., 79., 82. };
134
135  const G4double Tdat[22] = { 100*eV,  200*eV,  400*eV,  700*eV,
136                               1*keV,   2*keV,   4*keV,   7*keV,
137                              10*keV,  20*keV,  40*keV,  70*keV,
138                             100*keV, 200*keV, 400*keV, 700*keV,
139                               1*MeV,   2*MeV,   4*MeV,   7*MeV,
140                              10*MeV,  20*MeV};
141
142  // corr. factors for e-/e+ lambda for T <= Tlim
143          G4double celectron[15][22] =
144          {{1.125,1.072,1.051,1.047,1.047,1.050,1.052,1.054,
145            1.054,1.057,1.062,1.069,1.075,1.090,1.105,1.111,
146            1.112,1.108,1.100,1.093,1.089,1.087            },
147           {1.408,1.246,1.143,1.096,1.077,1.059,1.053,1.051,
148            1.052,1.053,1.058,1.065,1.072,1.087,1.101,1.108,
149            1.109,1.105,1.097,1.090,1.086,1.082            },
150           {2.833,2.268,1.861,1.612,1.486,1.309,1.204,1.156,
151            1.136,1.114,1.106,1.106,1.109,1.119,1.129,1.132,
152            1.131,1.124,1.113,1.104,1.099,1.098            },
153           {3.879,3.016,2.380,2.007,1.818,1.535,1.340,1.236,
154            1.190,1.133,1.107,1.099,1.098,1.103,1.110,1.113,
155            1.112,1.105,1.096,1.089,1.085,1.098            },
156           {6.937,4.330,2.886,2.256,1.987,1.628,1.395,1.265,
157            1.203,1.122,1.080,1.065,1.061,1.063,1.070,1.073,
158            1.073,1.070,1.064,1.059,1.056,1.056            },
159           {9.616,5.708,3.424,2.551,2.204,1.762,1.485,1.330,
160            1.256,1.155,1.099,1.077,1.070,1.068,1.072,1.074,
161            1.074,1.070,1.063,1.059,1.056,1.052            },
162           {11.72,6.364,3.811,2.806,2.401,1.884,1.564,1.386,
163            1.300,1.180,1.112,1.082,1.073,1.066,1.068,1.069,
164            1.068,1.064,1.059,1.054,1.051,1.050            },
165           {18.08,8.601,4.569,3.183,2.662,2.025,1.646,1.439,
166            1.339,1.195,1.108,1.068,1.053,1.040,1.039,1.039,
167            1.039,1.037,1.034,1.031,1.030,1.036            },
168           {18.22,10.48,5.333,3.713,3.115,2.367,1.898,1.631,
169            1.498,1.301,1.171,1.105,1.077,1.048,1.036,1.033,
170            1.031,1.028,1.024,1.022,1.021,1.024            },
171           {14.14,10.65,5.710,3.929,3.266,2.453,1.951,1.669,
172            1.528,1.319,1.178,1.106,1.075,1.040,1.027,1.022,
173            1.020,1.017,1.015,1.013,1.013,1.020            },
174           {14.11,11.73,6.312,4.240,3.478,2.566,2.022,1.720,
175            1.569,1.342,1.186,1.102,1.065,1.022,1.003,0.997,
176            0.995,0.993,0.993,0.993,0.993,1.011            },
177           {22.76,20.01,8.835,5.287,4.144,2.901,2.219,1.855,
178            1.677,1.410,1.224,1.121,1.073,1.014,0.986,0.976,
179            0.974,0.972,0.973,0.974,0.975,0.987            },
180           {50.77,40.85,14.13,7.184,5.284,3.435,2.520,2.059,
181            1.837,1.512,1.283,1.153,1.091,1.010,0.969,0.954,
182            0.950,0.947,0.949,0.952,0.954,0.963            },
183           {65.87,59.06,15.87,7.570,5.567,3.650,2.682,2.182,
184            1.939,1.579,1.325,1.178,1.108,1.014,0.965,0.947,
185            0.941,0.938,0.940,0.944,0.946,0.954            },
186           {55.60,47.34,15.92,7.810,5.755,3.767,2.760,2.239,
187            1.985,1.609,1.343,1.188,1.113,1.013,0.960,0.939,
188            0.933,0.930,0.933,0.936,0.939,0.949            }};
189           
190           G4double cpositron[15][22] = {
191           {2.589,2.044,1.658,1.446,1.347,1.217,1.144,1.110,
192            1.097,1.083,1.080,1.086,1.092,1.108,1.123,1.131,
193            1.131,1.126,1.117,1.108,1.103,1.100            },
194           {3.904,2.794,2.079,1.710,1.543,1.325,1.202,1.145,
195            1.122,1.096,1.089,1.092,1.098,1.114,1.130,1.137,
196            1.138,1.132,1.122,1.113,1.108,1.102            },
197           {7.970,6.080,4.442,3.398,2.872,2.127,1.672,1.451,
198            1.357,1.246,1.194,1.179,1.178,1.188,1.201,1.205,
199            1.203,1.190,1.173,1.159,1.151,1.145            },
200           {9.714,7.607,5.747,4.493,3.815,2.777,2.079,1.715,
201            1.553,1.353,1.253,1.219,1.211,1.214,1.225,1.228,
202            1.225,1.210,1.191,1.175,1.166,1.174            },
203           {17.97,12.95,8.628,6.065,4.849,3.222,2.275,1.820,
204            1.624,1.382,1.259,1.214,1.202,1.202,1.214,1.219,
205            1.217,1.203,1.184,1.169,1.160,1.151            },
206           {24.83,17.06,10.84,7.355,5.767,3.707,2.546,1.996,
207            1.759,1.465,1.311,1.252,1.234,1.228,1.238,1.241,
208            1.237,1.222,1.201,1.184,1.174,1.159            },
209           {23.26,17.15,11.52,8.049,6.375,4.114,2.792,2.155,
210            1.880,1.535,1.353,1.281,1.258,1.247,1.254,1.256,
211            1.252,1.234,1.212,1.194,1.183,1.170            },
212           {22.33,18.01,12.86,9.212,7.336,4.702,3.117,2.348,
213            2.015,1.602,1.385,1.297,1.268,1.251,1.256,1.258,
214            1.254,1.237,1.214,1.195,1.185,1.179            },
215           {33.91,24.13,15.71,10.80,8.507,5.467,3.692,2.808,
216            2.407,1.873,1.564,1.425,1.374,1.330,1.324,1.320,
217            1.312,1.288,1.258,1.235,1.221,1.205            },
218           {32.14,24.11,16.30,11.40,9.015,5.782,3.868,2.917,
219            2.490,1.925,1.596,1.447,1.391,1.342,1.332,1.327,
220            1.320,1.294,1.264,1.240,1.226,1.214            },
221           {29.51,24.07,17.19,12.28,9.766,6.238,4.112,3.066,
222            2.602,1.995,1.641,1.477,1.414,1.356,1.342,1.336,
223            1.328,1.302,1.270,1.245,1.231,1.233            },
224           {38.19,30.85,21.76,15.35,12.07,7.521,4.812,3.498,
225            2.926,2.188,1.763,1.563,1.484,1.405,1.382,1.371,
226            1.361,1.330,1.294,1.267,1.251,1.239            },
227           {49.71,39.80,27.96,19.63,15.36,9.407,5.863,4.155,
228            3.417,2.478,1.944,1.692,1.589,1.480,1.441,1.423,
229            1.409,1.372,1.330,1.298,1.280,1.258            },
230           {59.25,45.08,30.36,20.83,16.15,9.834,6.166,4.407,
231            3.641,2.648,2.064,1.779,1.661,1.531,1.482,1.459,
232            1.442,1.400,1.354,1.319,1.299,1.272            },
233           {56.38,44.29,30.50,21.18,16.51,10.11,6.354,4.542,
234            3.752,2.724,2.116,1.817,1.692,1.554,1.499,1.474,
235            1.456,1.412,1.364,1.328,1.307,1.282            }};
236
237  //data/corrections for T > Tlim 
238  G4double Tlim = 10.*MeV;
239  G4double beta2lim = Tlim*(Tlim+2.*electron_mass_c2)/
240                      ((Tlim+electron_mass_c2)*(Tlim+electron_mass_c2));
241  G4double bg2lim   = Tlim*(Tlim+2.*electron_mass_c2)/
242                      (electron_mass_c2*electron_mass_c2);
243
244  G4double sig0[15] = {0.2672*barn,  0.5922*barn, 2.653*barn,  6.235*barn,
245                      11.69*barn  , 13.24*barn  , 16.12*barn, 23.00*barn ,
246                      35.13*barn  , 39.95*barn  , 50.85*barn, 67.19*barn ,
247                      91.15*barn  , 104.4*barn  , 113.1*barn};
248                                       
249  G4double hecorr[15] = {120.70, 117.50, 105.00, 92.92, 79.23,  74.510,  68.29,
250                          57.39,  41.97,  36.14, 24.53, 10.21,  -7.855, -16.84,
251                         -22.30};
252
253  G4double sigma;
254  SetParticle(part);
255
256  G4double Z23 = 2.*log(AtomicNumber)/3.; Z23 = exp(Z23);
257
258  // correction if particle .ne. e-/e+
259  // compute equivalent kinetic energy
260  // lambda depends on p*beta ....
261
262  G4double eKineticEnergy = KineticEnergy;
263
264  if(mass > electron_mass_c2)
265  {
266    G4double TAU = KineticEnergy/mass ;
267    G4double c = mass*TAU*(TAU+2.)/(electron_mass_c2*(TAU+1.)) ;
268    G4double w = c-2. ;
269    G4double tau = 0.5*(w+sqrt(w*w+4.*c)) ;
270    eKineticEnergy = electron_mass_c2*tau ;
271  }
272
273  G4double ChargeSquare = charge*charge;
274
275  G4double eTotalEnergy = eKineticEnergy + electron_mass_c2 ;
276  G4double beta2 = eKineticEnergy*(eTotalEnergy+electron_mass_c2)
277                                 /(eTotalEnergy*eTotalEnergy);
278  G4double bg2   = eKineticEnergy*(eTotalEnergy+electron_mass_c2)
279                                 /(electron_mass_c2*electron_mass_c2);
280
281  G4double eps = epsfactor*bg2/Z23;
282
283  if     (eps<epsmin)  sigma = 2.*eps*eps;
284  else if(eps<epsmax)  sigma = log(1.+2.*eps)-2.*eps/(1.+2.*eps);
285  else                 sigma = log(2.*eps)-1.+1./eps;
286
287  sigma *= ChargeSquare*AtomicNumber*AtomicNumber/(beta2*bg2);
288
289  // interpolate in AtomicNumber and beta2
290  G4double c1,c2,cc1,cc2,corr;
291
292  // get bin number in Z
293  G4int iZ = 14;
294  while ((iZ>=0)&&(Zdat[iZ]>=AtomicNumber)) iZ -= 1;
295  if (iZ==14)                               iZ = 13;
296  if (iZ==-1)                               iZ = 0 ;
297
298  G4double Z1 = Zdat[iZ];
299  G4double Z2 = Zdat[iZ+1];
300  G4double ratZ = (AtomicNumber-Z1)*(AtomicNumber+Z1)/
301                  ((Z2-Z1)*(Z2+Z1));
302
303  if(eKineticEnergy <= Tlim) 
304  {
305    // get bin number in T (beta2)
306    G4int iT = 21;
307    while ((iT>=0)&&(Tdat[iT]>=eKineticEnergy)) iT -= 1;
308    if(iT==21)                                  iT = 20;
309    if(iT==-1)                                  iT = 0 ;
310
311    //  calculate betasquare values
312    G4double T = Tdat[iT],   E = T + electron_mass_c2;
313    G4double b2small = T*(E+electron_mass_c2)/(E*E);
314
315    T = Tdat[iT+1]; E = T + electron_mass_c2;
316    G4double b2big = T*(E+electron_mass_c2)/(E*E);
317    G4double ratb2 = (beta2-b2small)/(b2big-b2small);
318
319    if (charge < 0.)
320    {
321       c1 = celectron[iZ][iT];
322       c2 = celectron[iZ+1][iT];
323       cc1 = c1+ratZ*(c2-c1);
324
325       c1 = celectron[iZ][iT+1];
326       c2 = celectron[iZ+1][iT+1];
327       cc2 = c1+ratZ*(c2-c1);
328
329       corr = cc1+ratb2*(cc2-cc1);
330
331       sigma *= sigmafactor/corr;
332    }
333    else             
334    {
335       c1 = cpositron[iZ][iT];
336       c2 = cpositron[iZ+1][iT];
337       cc1 = c1+ratZ*(c2-c1);
338
339       c1 = cpositron[iZ][iT+1];
340       c2 = cpositron[iZ+1][iT+1];
341       cc2 = c1+ratZ*(c2-c1);
342
343       corr = cc1+ratb2*(cc2-cc1);
344
345       sigma *= sigmafactor/corr;
346    }
347  }
348  else
349  {
350    c1 = bg2lim*sig0[iZ]*(1.+hecorr[iZ]*(beta2-beta2lim))/bg2;
351    c2 = bg2lim*sig0[iZ+1]*(1.+hecorr[iZ+1]*(beta2-beta2lim))/bg2;
352    if((AtomicNumber >= Z1) && (AtomicNumber <= Z2))
353      sigma = c1+ratZ*(c2-c1) ;
354    else if(AtomicNumber < Z1)
355      sigma = AtomicNumber*AtomicNumber*c1/(Z1*Z1);
356    else if(AtomicNumber > Z2)
357      sigma = AtomicNumber*AtomicNumber*c2/(Z2*Z2);
358  }
359  return sigma;
360
361}
362
363//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
364
365G4double G4UrbanMscModel90::ComputeTruePathLengthLimit(
366                             const G4Track& track,
367                             G4PhysicsTable* theTable,
368                             G4double currentMinimalStep)
369{
370  tPathLength = currentMinimalStep;
371  const G4DynamicParticle* dp = track.GetDynamicParticle();
372  G4StepPoint* sp = track.GetStep()->GetPreStepPoint();
373  G4StepStatus stepStatus = sp->GetStepStatus();
374
375  if(stepStatus == fUndefined) {
376    inside = false;
377    insideskin = false;
378    tlimit = geombig;
379    SetParticle( dp->GetDefinition() );
380  }
381
382  theLambdaTable = theTable;
383  couple = track.GetMaterialCutsCouple();
384  currentMaterialIndex = couple->GetIndex();
385  currentKinEnergy = dp->GetKineticEnergy();
386  currentRange = 
387    theManager->GetRangeFromRestricteDEDX(particle,currentKinEnergy,couple);
388  lambda0 = GetLambda(currentKinEnergy);
389
390  // stop here if small range particle
391  if(inside) return tPathLength;           
392 
393  if(tPathLength > currentRange) tPathLength = currentRange;
394
395  presafety = sp->GetSafety();
396  /*
397  G4cout << "G4UrbanMscModel90::ComputeTruePathLengthLimit tPathLength= "
398         <<tPathLength<<" safety= " << presafety
399       << " range= " <<currentRange<<G4endl;
400  */
401  // far from geometry boundary
402  if(currentRange < presafety)
403    {
404      inside = true;
405      return tPathLength; 
406    }
407
408  // standard  version
409  //
410  if (steppingAlgorithm == fUseDistanceToBoundary)
411    {
412      //compute geomlimit and presafety
413      G4double geomlimit = ComputeGeomLimit(track, presafety, currentRange);
414   
415      // is far from boundary
416      if(currentRange <= presafety)
417        {
418          inside = true;
419          return tPathLength;   
420        }
421
422      smallstep += 1.;
423      insideskin = false;
424
425      if((stepStatus == fGeomBoundary) || (stepStatus == fUndefined))
426        {
427
428          if(stepStatus == fUndefined) smallstep = 1.e10;
429          else  smallstep = 1.;
430
431          // facrange scaling in lambda
432          // not so strong step restriction above lambdalimit
433          G4double facr = facrange;
434          if(lambda0 > lambdalimit)
435            facr *= frscaling1+frscaling2*lambda0/lambdalimit;
436
437          // constraint from the physics
438          if (currentRange > lambda0) tlimit = facr*currentRange;
439          else                        tlimit = facr*lambda0;
440
441          // constraint from the geometry (if tlimit above is too big)
442          G4double tgeom = geombig; 
443          if(geomlimit > geommin)
444            {
445              if(stepStatus == fGeomBoundary) 
446                tgeom = geomlimit/facgeom;
447              else
448                tgeom = 2.*geomlimit/facgeom;
449            }
450
451          //define stepmin here (it depends on lambda!)
452          //rough estimation of lambda_elastic/lambda_transport
453          G4double rat = currentKinEnergy/MeV ;
454          rat = 1.e-3/(rat*(10.+rat)) ;
455          //stepmin ~ lambda_elastic
456          stepmin = rat*lambda0;
457          skindepth = skin*stepmin;
458
459          //define tlimitmin
460          tlimitmin = lambda0/nstepmax;
461          if(tlimitmin < stepmin) tlimitmin = 1.01*stepmin;
462          if(tlimitmin < tlimitminfix) tlimitmin = tlimitminfix;
463
464          //lower limit for tlimit
465          if(tlimit < tlimitmin) tlimit = tlimitmin;
466
467          //check against geometry limit
468          if(tlimit > tgeom) tlimit = tgeom;
469        }
470
471      //if track starts far from boundaries increase tlimit!
472      if(tlimit < facsafety*presafety) tlimit = facsafety*presafety ;
473
474      //  G4cout << "tgeom= " << tgeom << " geomlimit= " << geomlimit 
475      //     << " tlimit= " << tlimit << " presafety= " << presafety << G4endl;
476
477      // shortcut
478      if((tPathLength < tlimit) && (tPathLength < presafety))
479        return tPathLength;   
480
481      G4double tnow = tlimit;
482      // optimization ...
483      if(geomlimit < geombig) tnow = max(tlimit,facsafety*geomlimit);
484   
485      // step reduction near to boundary
486      if(smallstep < skin)
487        {
488          tnow = stepmin;
489          insideskin = true;
490        }
491      else if(geomlimit < geombig)
492        {
493          if(geomlimit > skindepth)
494            {
495              if(tnow > geomlimit-0.999*skindepth)
496                tnow = geomlimit-0.999*skindepth;
497            }
498          else
499            {
500              insideskin = true;
501              if(tnow > stepmin) tnow = stepmin;
502            }
503        }
504
505      if(tnow < stepmin) tnow = stepmin;
506
507      if(tPathLength > tnow) tPathLength = tnow ; 
508    }
509    // for 'normal' simulation with or without magnetic field
510    //  there no small step/single scattering at boundaries
511  else if(steppingAlgorithm == fUseSafety)
512    {
513      // compute presafety again if presafety <= 0 and no boundary
514      // i.e. when it is needed for optimization purposes
515      if((stepStatus != fGeomBoundary) && (presafety < tlimitminfix)) 
516        presafety = ComputeSafety(sp->GetPosition(),tPathLength); 
517
518      // is far from boundary
519      if(currentRange < presafety)
520        {
521          inside = true;
522          return tPathLength; 
523        }
524
525      if((stepStatus == fGeomBoundary) || (stepStatus == fUndefined))
526        { 
527          // facrange scaling in lambda
528          // not so strong step restriction above lambdalimit
529          G4double facr = facrange;
530          if(lambda0 > lambdalimit)
531            facr *= frscaling1+frscaling2*lambda0/lambdalimit;
532
533          // constraint from the physics
534          if (currentRange > lambda0) tlimit = facr*currentRange;
535          else                        tlimit = facr*lambda0;
536
537          //lower limit for tlimit
538          tlimitmin = std::max(tlimitminfix,lambda0/nstepmax);
539          if(tlimit < tlimitmin) tlimit = tlimitmin;
540        }
541
542      //if track starts far from boundaries increase tlimit!
543      if(tlimit < facsafety*presafety) tlimit = facsafety*presafety ;
544
545      if(tPathLength > tlimit) tPathLength = tlimit;
546    }
547 
548  // version similar to 7.1 (needed for some experiments)
549  else
550    {
551      if (stepStatus == fGeomBoundary)
552        {
553          if (currentRange > lambda0) tlimit = facrange*currentRange;
554          else                        tlimit = facrange*lambda0;
555
556          if(tlimit < tlimitmin) tlimit = tlimitmin;
557          if(tPathLength > tlimit) tPathLength = tlimit;
558        }
559    }
560  //  G4cout << "tPathLength= " << tPathLength << "  geomlimit= " << geomlimit
561  //     << " currentMinimalStep= " << currentMinimalStep << G4endl;
562  return tPathLength ;
563}
564
565//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
566
567G4double G4UrbanMscModel90::ComputeGeomPathLength(G4double)
568{
569  lambdaeff = lambda0;
570  par1 = -1. ; 
571  par2 = par3 = 0. ; 
572
573  //  do the true -> geom transformation
574  zPathLength = tPathLength;
575
576  // z = t for very small tPathLength
577  if(tPathLength < tlimitminfix) return zPathLength;
578
579  // this correction needed to run MSC with eIoni and eBrem inactivated
580  // and makes no harm for a normal run
581  if(tPathLength > currentRange)
582    tPathLength = currentRange ;
583
584  G4double tau   = tPathLength/lambda0 ;
585
586  if ((tau <= tausmall) || insideskin) {
587    zPathLength  = tPathLength;
588    if(zPathLength > lambda0) zPathLength = lambda0;
589    return zPathLength;
590  }
591
592  G4double zmean = tPathLength;
593  if (tPathLength < currentRange*dtrl) {
594    if(tau < taulim) zmean = tPathLength*(1.-0.5*tau) ;
595    else             zmean = lambda0*(1.-exp(-tau));
596  } else if(currentKinEnergy < mass) {
597    par1 = 1./currentRange ;
598    par2 = 1./(par1*lambda0) ;
599    par3 = 1.+par2 ;
600    if(tPathLength < currentRange)
601      zmean = (1.-exp(par3*log(1.-tPathLength/currentRange)))/(par1*par3) ;
602    else
603      zmean = 1./(par1*par3) ;
604  } else {
605    G4double T1 = theManager->GetEnergy(particle,currentRange-tPathLength,couple);
606    G4double lambda1 = GetLambda(T1);
607
608    par1 = (lambda0-lambda1)/(lambda0*tPathLength) ;
609    par2 = 1./(par1*lambda0) ;
610    par3 = 1.+par2 ;
611    zmean = (1.-exp(par3*log(lambda1/lambda0)))/(par1*par3) ;
612  }
613
614  zPathLength = zmean ;
615
616  //  sample z
617  if(samplez)
618  {
619    const G4double  ztmax = 0.99, onethird = 1./3. ;
620    G4double zt = zmean/tPathLength ;
621
622    if (tPathLength > stepmin && zt < ztmax)             
623    {
624      G4double u,cz1;
625      if(zt >= onethird)
626      {
627        G4double cz = 0.5*(3.*zt-1.)/(1.-zt) ;
628        cz1 = 1.+cz ;
629        G4double u0 = cz/cz1 ;
630        G4double grej ;
631        do {
632            u = exp(log(G4UniformRand())/cz1) ;
633            grej = exp(cz*log(u/u0))*(1.-u)/(1.-u0) ;
634           } while (grej < G4UniformRand()) ;
635      }
636      else
637      {
638        cz1 = 1./zt-1.;
639        u = 1.-exp(log(G4UniformRand())/cz1) ;
640      }
641      zPathLength = tPathLength*u ;
642    }
643  }
644
645  if(zPathLength > lambda0) zPathLength = lambda0;
646
647  return zPathLength;
648}
649
650//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
651
652G4double G4UrbanMscModel90::ComputeTrueStepLength(G4double geomStepLength)
653{
654  // step defined other than transportation
655  if(geomStepLength == zPathLength && tPathLength <= currentRange)
656    return tPathLength;
657
658  // t = z for very small step
659  zPathLength = geomStepLength;
660  tPathLength = geomStepLength;
661  if(geomStepLength < tlimitminfix) return tPathLength;
662 
663  // recalculation
664  if((geomStepLength > lambda0*tausmall) && !insideskin)
665  {
666    if(par1 <  0.)
667      tPathLength = -lambda0*log(1.-geomStepLength/lambda0) ;
668    else 
669    {
670      if(par1*par3*geomStepLength < 1.)
671        tPathLength = (1.-exp(log(1.-par1*par3*geomStepLength)/par3))/par1 ;
672      else 
673        tPathLength = currentRange;
674    } 
675  }
676  if(tPathLength < geomStepLength) tPathLength = geomStepLength;
677
678  return tPathLength;
679}
680
681//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
682
683G4double G4UrbanMscModel90::ComputeTheta0(G4double trueStepLength,
684                                        G4double KineticEnergy)
685{
686  // for all particles take the width of the central part
687  //  from a  parametrization similar to the Highland formula
688  // ( Highland formula: Particle Physics Booklet, July 2002, eq. 26.10)
689  const G4double c_highland = 13.6*MeV ;
690  G4double betacp = sqrt(currentKinEnergy*(currentKinEnergy+2.*mass)*
691                         KineticEnergy*(KineticEnergy+2.*mass)/
692                      ((currentKinEnergy+mass)*(KineticEnergy+mass)));
693  G4double y = trueStepLength/currentRadLength;
694  G4double theta0 = c_highland*std::abs(charge)*sqrt(y)/betacp;
695           y = log(y);
696           theta0 *= sqrt(1.+y*(0.105+0.0035*y));
697
698  //correction for small Zeff (based on high energy
699  // proton scattering  data)
700  // see G.Shen at al. Phys.Rev.D20(1979) p.1584
701  theta0 *= 1.-0.24/(Zeff*(Zeff+1.));
702
703  return theta0;
704
705}
706
707//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
708
709void G4UrbanMscModel90::SampleScattering(const G4DynamicParticle* dynParticle,
710                                         G4double safety)
711{
712  G4double kineticEnergy = dynParticle->GetKineticEnergy();
713  if((kineticEnergy <= 0.0) || (tPathLength <= tlimitminfix) ||
714     (tPathLength/tausmall < lambda0) ) return;
715
716  G4double cth  = SampleCosineTheta(tPathLength,kineticEnergy);
717  // protection against 'bad' cth values
718  if(std::abs(cth) > 1.) return;
719
720  G4double sth  = sqrt((1.0 - cth)*(1.0 + cth));
721  G4double phi  = twopi*G4UniformRand();
722  G4double dirx = sth*cos(phi);
723  G4double diry = sth*sin(phi);
724
725  G4ThreeVector oldDirection = dynParticle->GetMomentumDirection();
726  G4ThreeVector newDirection(dirx,diry,cth);
727  newDirection.rotateUz(oldDirection);
728  fParticleChange->ProposeMomentumDirection(newDirection);
729
730  if (latDisplasment && safety > tlimitminfix) {
731
732    G4double r = SampleDisplacement();
733/*
734    G4cout << "G4UrbanMscModel90::SampleSecondaries: e(MeV)= " << kineticEnergy
735           << " sinTheta= " << sth << " r(mm)= " << r
736           << " trueStep(mm)= " << truestep
737           << " geomStep(mm)= " << zPathLength
738           << G4endl;
739*/
740    if(r > 0.)
741      {
742        G4double latcorr = LatCorrelation();
743        if(latcorr > r) latcorr = r;
744
745        // sample direction of lateral displacement
746        // compute it from the lateral correlation
747        G4double Phi = 0.;
748        if(std::abs(r*sth) < latcorr) {
749          Phi  = twopi*G4UniformRand();
750        } else {
751          G4double psi = std::acos(latcorr/(r*sth));
752          if(G4UniformRand() < 0.5) Phi = phi+psi;
753          else                      Phi = phi-psi;
754        }
755
756        dirx = std::cos(Phi);
757        diry = std::sin(Phi);
758
759        G4ThreeVector latDirection(dirx,diry,0.0);
760        latDirection.rotateUz(oldDirection);
761        ComputeDisplacement(fParticleChange, latDirection, r, safety);
762      }
763  }
764}
765
766//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
767
768G4double G4UrbanMscModel90::SampleCosineTheta(G4double trueStepLength,
769                                            G4double KineticEnergy)
770{
771  G4double cth = 1. ;
772  G4double tau = trueStepLength/lambda0 ;
773
774  Zeff = couple->GetMaterial()->GetTotNbOfElectPerVolume()/
775         couple->GetMaterial()->GetTotNbOfAtomsPerVolume() ;
776
777  if(insideskin)
778  {
779    //no scattering, single or plural scattering
780    G4double mean = trueStepLength/stepmin ;
781
782    G4int n = G4Poisson(mean);
783    if(n > 0)
784    {
785      G4double tm = KineticEnergy/electron_mass_c2;
786      // ascr - screening parameter
787      G4double ascr = exp(log(Zeff)/3.)/(137.*sqrt(tm*(tm+2.)));
788      G4double ascr1 = 1.+0.5*ascr*ascr;
789      G4double bp1=ascr1+1.;
790      G4double bm1=ascr1-1.;
791      // single scattering from screened Rutherford x-section
792      G4double ct,st,phi;
793      G4double sx=0.,sy=0.,sz=0.;
794      for(G4int i=1; i<=n; i++)
795      {
796        ct = ascr1-bp1*bm1/(2.*G4UniformRand()+bm1);
797        if(ct < -1.) ct = -1.;
798        if(ct >  1.) ct =  1.; 
799        st = sqrt(1.-ct*ct);
800        phi = twopi*G4UniformRand();
801        sx += st*cos(phi);
802        sy += st*sin(phi);
803        sz += ct;
804      }
805        cth = sz/sqrt(sx*sx+sy*sy+sz*sz);
806    }
807  }
808  else
809  {
810    if(trueStepLength >= currentRange*dtrl) {
811      if(par1*trueStepLength < 1.)
812        tau = -par2*log(1.-par1*trueStepLength) ;
813      // for the case if ioni/brems are inactivated
814      // see the corresponding condition in ComputeGeomPathLength
815      else if(1.-KineticEnergy/currentKinEnergy > taulim)
816        tau = taubig ;
817    }
818    currentTau = tau ;
819    lambdaeff = trueStepLength/currentTau;
820    currentRadLength = couple->GetMaterial()->GetRadlen();
821
822    if (tau >= taubig) cth = -1.+2.*G4UniformRand();
823    else if (tau >= tausmall)
824    {
825      G4double b,bx,b1,ebx,eb1;
826      G4double prob = 0., qprob = 1. ;
827      G4double a = 1., ea = 0., eaa = 1.;
828      G4double xmean1 = 1., xmean2 = 0.;
829      G4double xsi = 3.;
830
831      G4double theta0 = ComputeTheta0(trueStepLength,KineticEnergy);
832
833      // protexction for very small angles
834      if(theta0 < tausmall) return cth;
835
836      G4double sth = sin(0.5*theta0);
837      a = 0.25/(sth*sth);
838
839      G4double xmeanth = exp(-tau);
840
841      G4double c = 3. ;         
842      G4double c1 = c-1.;
843
844      G4double x0 = 1.-xsi/a ;
845      if(x0 < 0.)
846      {
847        // 1 model function
848        b = exp(tau);
849        bx = b-1.;
850        b1 = b+1.;
851        ebx=exp((c1)*log(bx)) ;
852        eb1=exp((c1)*log(b1)) ;
853      }
854      else
855      {
856        //empirical tail parameter
857        // based some exp. data
858        c = 2.40-0.027*exp(2.*log(Zeff)/3.);
859
860        if(c == 2.) c = 2.+taulim ;
861        if(c <= 1.) c = 1.+taulim ;
862        c1 = c-1.;
863
864        ea = exp(-xsi) ;
865        eaa = 1.-ea ;
866        xmean1 = 1.-(1.-(1.+xsi)*ea)/(eaa*a) ; 
867
868        // from the continuity of the 1st derivative at x=x0
869        b = 1.+(c-xsi)/a ;
870
871        b1 = b+1. ;
872        bx = c/a ;
873        eb1=exp((c1)*log(b1)) ;
874        ebx=exp((c1)*log(bx)) ;
875        xmean2 = (x0*eb1+ebx-(eb1*bx-b1*ebx)/(c-2.))/(eb1-ebx) ;
876
877        G4double f1x0 = a*ea/eaa ;
878        G4double f2x0 = c1*eb1*ebx/(eb1-ebx)/exp(c*log(bx)) ;
879
880        // from continuity at x=x0
881        prob = f2x0/(f1x0+f2x0) ;
882
883        // from xmean = xmeanth
884        qprob = (f1x0+f2x0)*xmeanth/(f2x0*xmean1+f1x0*xmean2) ;
885      }
886
887      // sampling of costheta
888      if (G4UniformRand() < qprob)
889      {
890        if (G4UniformRand() < prob)
891           cth = 1.+log(ea+G4UniformRand()*eaa)/a ;
892        else
893           cth = b-b1*bx/exp(log(ebx-G4UniformRand()*(ebx-eb1))/c1) ;
894      }
895      else
896      {
897        cth = -1.+2.*G4UniformRand();
898      }
899    }
900  } 
901
902  return cth ;
903}
904//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
905
906G4double G4UrbanMscModel90::SampleDisplacement()
907{
908  const G4double kappa = 2.5;
909  const G4double kappapl1 = kappa+1.;
910  const G4double kappami1 = kappa-1.;
911  G4double rmean = 0.0;
912  if ((currentTau >= tausmall) && !insideskin) {
913    if (currentTau < taulim) {
914      rmean = kappa*currentTau*currentTau*currentTau*
915             (1.-kappapl1*currentTau*0.25)/6. ;
916
917    } else {
918      G4double etau = 0.0;
919      if (currentTau<taubig) etau = exp(-currentTau);
920      rmean = -kappa*currentTau;
921      rmean = -exp(rmean)/(kappa*kappami1);
922      rmean += currentTau-kappapl1/kappa+kappa*etau/kappami1;
923    }
924    if (rmean>0.) rmean = 2.*lambdaeff*sqrt(rmean/3.0);
925    else          rmean = 0.;
926  }
927
928  // protection against z > t ...........................
929  if(rmean > 0.) {
930    G4double zt = (tPathLength-zPathLength)*(tPathLength+zPathLength);
931    if(zt <= 0.)
932      rmean = 0.;
933    else if(rmean*rmean > zt)
934      rmean = sqrt(zt);
935  }
936  return rmean;
937}
938
939//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
940
941G4double G4UrbanMscModel90::LatCorrelation()
942{
943  const G4double kappa = 2.5;
944  const G4double kappami1 = kappa-1.;
945
946  G4double latcorr = 0.;
947  if((currentTau >= tausmall) && !insideskin)
948  {
949    if(currentTau < taulim)
950      latcorr = lambdaeff*kappa*currentTau*currentTau*
951                (1.-(kappa+1.)*currentTau/3.)/3.;
952    else
953    {
954      G4double etau = 0.;
955      if(currentTau < taubig) etau = exp(-currentTau);
956      latcorr = -kappa*currentTau;
957      latcorr = exp(latcorr)/kappami1;
958      latcorr += 1.-kappa*etau/kappami1 ;
959      latcorr *= 2.*lambdaeff/3. ;
960    }
961  }
962
963  return latcorr;
964}
965
966//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
967
968void G4UrbanMscModel90::SampleSecondaries(std::vector<G4DynamicParticle*>*,
969                                          const G4MaterialCutsCouple*,
970                                          const G4DynamicParticle*,
971                                          G4double,
972                                          G4double)
973{}
974
975//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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