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

Last change on this file was 1340, checked in by garnier, 14 years ago

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[1197]1//
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26//
[1340]27// $Id: G4UrbanMscModel92.cc,v 1.2 2010/10/26 10:06:12 vnivanch Exp $
28// GEANT4 tag $Name: emstand-V09-03-24 $
[1197]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
[1340]168  skindepth = skin*stepmin;
169
170  mass = proton_mass_c2;
171  charge = ChargeSquare = 1.0;
172  currentKinEnergy = currentRadLength = lambda0 = lambdaeff = tPathLength
173    = zPathLength = par1 = par2 = par3 = 0;
174
175  currentMaterialIndex = 0;
[1197]176}
177
178//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
179
180G4UrbanMscModel92::~G4UrbanMscModel92()
181{}
182
183//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
184
185void G4UrbanMscModel92::Initialise(const G4ParticleDefinition* p,
186                                   const G4DataVector&)
187{
188  skindepth = skin*stepmin;
189  if(isInitialized) return;
190  // set values of some data members
191  SetParticle(p);
192
193  fParticleChange = GetParticleChangeForMSC();
194  InitialiseSafetyHelper();
195
196  isInitialized = true;
197}
198
199//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
200
201G4double G4UrbanMscModel92::ComputeCrossSectionPerAtom( 
202                             const G4ParticleDefinition* part,
203                                   G4double KineticEnergy,
204                                   G4double AtomicNumber,G4double,
205                                   G4double, G4double)
206{
207  const G4double sigmafactor = twopi*classic_electr_radius*classic_electr_radius;
208  const G4double epsfactor = 2.*electron_mass_c2*electron_mass_c2*
209                            Bohr_radius*Bohr_radius/(hbarc*hbarc);
210  const G4double epsmin = 1.e-4 , epsmax = 1.e10;
211
212  const G4double Zdat[15] = { 4.,  6., 13., 20., 26., 29., 32., 38., 47.,
213                             50., 56., 64., 74., 79., 82. };
214
215  const G4double Tdat[22] = { 100*eV,  200*eV,  400*eV,  700*eV,
216                               1*keV,   2*keV,   4*keV,   7*keV,
217                              10*keV,  20*keV,  40*keV,  70*keV,
218                             100*keV, 200*keV, 400*keV, 700*keV,
219                               1*MeV,   2*MeV,   4*MeV,   7*MeV,
220                              10*MeV,  20*MeV};
221
222  // corr. factors for e-/e+ lambda for T <= Tlim
223          G4double celectron[15][22] =
224          {{1.125,1.072,1.051,1.047,1.047,1.050,1.052,1.054,
225            1.054,1.057,1.062,1.069,1.075,1.090,1.105,1.111,
226            1.112,1.108,1.100,1.093,1.089,1.087            },
227           {1.408,1.246,1.143,1.096,1.077,1.059,1.053,1.051,
228            1.052,1.053,1.058,1.065,1.072,1.087,1.101,1.108,
229            1.109,1.105,1.097,1.090,1.086,1.082            },
230           {2.833,2.268,1.861,1.612,1.486,1.309,1.204,1.156,
231            1.136,1.114,1.106,1.106,1.109,1.119,1.129,1.132,
232            1.131,1.124,1.113,1.104,1.099,1.098            },
233           {3.879,3.016,2.380,2.007,1.818,1.535,1.340,1.236,
234            1.190,1.133,1.107,1.099,1.098,1.103,1.110,1.113,
235            1.112,1.105,1.096,1.089,1.085,1.098            },
236           {6.937,4.330,2.886,2.256,1.987,1.628,1.395,1.265,
237            1.203,1.122,1.080,1.065,1.061,1.063,1.070,1.073,
238            1.073,1.070,1.064,1.059,1.056,1.056            },
239           {9.616,5.708,3.424,2.551,2.204,1.762,1.485,1.330,
240            1.256,1.155,1.099,1.077,1.070,1.068,1.072,1.074,
241            1.074,1.070,1.063,1.059,1.056,1.052            },
242           {11.72,6.364,3.811,2.806,2.401,1.884,1.564,1.386,
243            1.300,1.180,1.112,1.082,1.073,1.066,1.068,1.069,
244            1.068,1.064,1.059,1.054,1.051,1.050            },
245           {18.08,8.601,4.569,3.183,2.662,2.025,1.646,1.439,
246            1.339,1.195,1.108,1.068,1.053,1.040,1.039,1.039,
247            1.039,1.037,1.034,1.031,1.030,1.036            },
248           {18.22,10.48,5.333,3.713,3.115,2.367,1.898,1.631,
249            1.498,1.301,1.171,1.105,1.077,1.048,1.036,1.033,
250            1.031,1.028,1.024,1.022,1.021,1.024            },
251           {14.14,10.65,5.710,3.929,3.266,2.453,1.951,1.669,
252            1.528,1.319,1.178,1.106,1.075,1.040,1.027,1.022,
253            1.020,1.017,1.015,1.013,1.013,1.020            },
254           {14.11,11.73,6.312,4.240,3.478,2.566,2.022,1.720,
255            1.569,1.342,1.186,1.102,1.065,1.022,1.003,0.997,
256            0.995,0.993,0.993,0.993,0.993,1.011            },
257           {22.76,20.01,8.835,5.287,4.144,2.901,2.219,1.855,
258            1.677,1.410,1.224,1.121,1.073,1.014,0.986,0.976,
259            0.974,0.972,0.973,0.974,0.975,0.987            },
260           {50.77,40.85,14.13,7.184,5.284,3.435,2.520,2.059,
261            1.837,1.512,1.283,1.153,1.091,1.010,0.969,0.954,
262            0.950,0.947,0.949,0.952,0.954,0.963            },
263           {65.87,59.06,15.87,7.570,5.567,3.650,2.682,2.182,
264            1.939,1.579,1.325,1.178,1.108,1.014,0.965,0.947,
265            0.941,0.938,0.940,0.944,0.946,0.954            },
266           {55.60,47.34,15.92,7.810,5.755,3.767,2.760,2.239,
267            1.985,1.609,1.343,1.188,1.113,1.013,0.960,0.939,
268            0.933,0.930,0.933,0.936,0.939,0.949            }};
269           
270           G4double cpositron[15][22] = {
271           {2.589,2.044,1.658,1.446,1.347,1.217,1.144,1.110,
272            1.097,1.083,1.080,1.086,1.092,1.108,1.123,1.131,
273            1.131,1.126,1.117,1.108,1.103,1.100            },
274           {3.904,2.794,2.079,1.710,1.543,1.325,1.202,1.145,
275            1.122,1.096,1.089,1.092,1.098,1.114,1.130,1.137,
276            1.138,1.132,1.122,1.113,1.108,1.102            },
277           {7.970,6.080,4.442,3.398,2.872,2.127,1.672,1.451,
278            1.357,1.246,1.194,1.179,1.178,1.188,1.201,1.205,
279            1.203,1.190,1.173,1.159,1.151,1.145            },
280           {9.714,7.607,5.747,4.493,3.815,2.777,2.079,1.715,
281            1.553,1.353,1.253,1.219,1.211,1.214,1.225,1.228,
282            1.225,1.210,1.191,1.175,1.166,1.174            },
283           {17.97,12.95,8.628,6.065,4.849,3.222,2.275,1.820,
284            1.624,1.382,1.259,1.214,1.202,1.202,1.214,1.219,
285            1.217,1.203,1.184,1.169,1.160,1.151            },
286           {24.83,17.06,10.84,7.355,5.767,3.707,2.546,1.996,
287            1.759,1.465,1.311,1.252,1.234,1.228,1.238,1.241,
288            1.237,1.222,1.201,1.184,1.174,1.159            },
289           {23.26,17.15,11.52,8.049,6.375,4.114,2.792,2.155,
290            1.880,1.535,1.353,1.281,1.258,1.247,1.254,1.256,
291            1.252,1.234,1.212,1.194,1.183,1.170            },
292           {22.33,18.01,12.86,9.212,7.336,4.702,3.117,2.348,
293            2.015,1.602,1.385,1.297,1.268,1.251,1.256,1.258,
294            1.254,1.237,1.214,1.195,1.185,1.179            },
295           {33.91,24.13,15.71,10.80,8.507,5.467,3.692,2.808,
296            2.407,1.873,1.564,1.425,1.374,1.330,1.324,1.320,
297            1.312,1.288,1.258,1.235,1.221,1.205            },
298           {32.14,24.11,16.30,11.40,9.015,5.782,3.868,2.917,
299            2.490,1.925,1.596,1.447,1.391,1.342,1.332,1.327,
300            1.320,1.294,1.264,1.240,1.226,1.214            },
301           {29.51,24.07,17.19,12.28,9.766,6.238,4.112,3.066,
302            2.602,1.995,1.641,1.477,1.414,1.356,1.342,1.336,
303            1.328,1.302,1.270,1.245,1.231,1.233            },
304           {38.19,30.85,21.76,15.35,12.07,7.521,4.812,3.498,
305            2.926,2.188,1.763,1.563,1.484,1.405,1.382,1.371,
306            1.361,1.330,1.294,1.267,1.251,1.239            },
307           {49.71,39.80,27.96,19.63,15.36,9.407,5.863,4.155,
308            3.417,2.478,1.944,1.692,1.589,1.480,1.441,1.423,
309            1.409,1.372,1.330,1.298,1.280,1.258            },
310           {59.25,45.08,30.36,20.83,16.15,9.834,6.166,4.407,
311            3.641,2.648,2.064,1.779,1.661,1.531,1.482,1.459,
312            1.442,1.400,1.354,1.319,1.299,1.272            },
313           {56.38,44.29,30.50,21.18,16.51,10.11,6.354,4.542,
314            3.752,2.724,2.116,1.817,1.692,1.554,1.499,1.474,
315            1.456,1.412,1.364,1.328,1.307,1.282            }};
316
317  //data/corrections for T > Tlim 
318  G4double Tlim = 10.*MeV;
319  G4double beta2lim = Tlim*(Tlim+2.*electron_mass_c2)/
320                      ((Tlim+electron_mass_c2)*(Tlim+electron_mass_c2));
321  G4double bg2lim   = Tlim*(Tlim+2.*electron_mass_c2)/
322                      (electron_mass_c2*electron_mass_c2);
323
324  G4double sig0[15] = {0.2672*barn,  0.5922*barn, 2.653*barn,  6.235*barn,
325                      11.69*barn  , 13.24*barn  , 16.12*barn, 23.00*barn ,
326                      35.13*barn  , 39.95*barn  , 50.85*barn, 67.19*barn ,
327                      91.15*barn  , 104.4*barn  , 113.1*barn};
328                                       
329  G4double hecorr[15] = {120.70, 117.50, 105.00, 92.92, 79.23,  74.510,  68.29,
330                          57.39,  41.97,  36.14, 24.53, 10.21,  -7.855, -16.84,
331                         -22.30};
332
333  G4double sigma;
334  SetParticle(part);
335
336  G4double Z23 = 2.*log(AtomicNumber)/3.; Z23 = exp(Z23);
337
338  // correction if particle .ne. e-/e+
339  // compute equivalent kinetic energy
340  // lambda depends on p*beta ....
341
342  G4double eKineticEnergy = KineticEnergy;
343
344  if(mass > electron_mass_c2)
345  {
346     G4double TAU = KineticEnergy/mass ;
347     G4double c = mass*TAU*(TAU+2.)/(electron_mass_c2*(TAU+1.)) ;
348     G4double w = c-2. ;
349     G4double tau = 0.5*(w+sqrt(w*w+4.*c)) ;
350     eKineticEnergy = electron_mass_c2*tau ;
351  }
352
353  G4double eTotalEnergy = eKineticEnergy + electron_mass_c2 ;
354  G4double beta2 = eKineticEnergy*(eTotalEnergy+electron_mass_c2)
355                                 /(eTotalEnergy*eTotalEnergy);
356  G4double bg2   = eKineticEnergy*(eTotalEnergy+electron_mass_c2)
357                                 /(electron_mass_c2*electron_mass_c2);
358
359  G4double eps = epsfactor*bg2/Z23;
360
361  if     (eps<epsmin)  sigma = 2.*eps*eps;
362  else if(eps<epsmax)  sigma = log(1.+2.*eps)-2.*eps/(1.+2.*eps);
363  else                 sigma = log(2.*eps)-1.+1./eps;
364
365  sigma *= ChargeSquare*AtomicNumber*AtomicNumber/(beta2*bg2);
366
367  // interpolate in AtomicNumber and beta2
368  G4double c1,c2,cc1,cc2,corr;
369
370  // get bin number in Z
371  G4int iZ = 14;
372  while ((iZ>=0)&&(Zdat[iZ]>=AtomicNumber)) iZ -= 1;
373  if (iZ==14)                               iZ = 13;
374  if (iZ==-1)                               iZ = 0 ;
375
376  G4double Z1 = Zdat[iZ];
377  G4double Z2 = Zdat[iZ+1];
378  G4double ratZ = (AtomicNumber-Z1)*(AtomicNumber+Z1)/
379                  ((Z2-Z1)*(Z2+Z1));
380
381  if(eKineticEnergy <= Tlim) 
382  {
383    // get bin number in T (beta2)
384    G4int iT = 21;
385    while ((iT>=0)&&(Tdat[iT]>=eKineticEnergy)) iT -= 1;
386    if(iT==21)                                  iT = 20;
387    if(iT==-1)                                  iT = 0 ;
388
389    //  calculate betasquare values
390    G4double T = Tdat[iT],   E = T + electron_mass_c2;
391    G4double b2small = T*(E+electron_mass_c2)/(E*E);
392
393    T = Tdat[iT+1]; E = T + electron_mass_c2;
394    G4double b2big = T*(E+electron_mass_c2)/(E*E);
395    G4double ratb2 = (beta2-b2small)/(b2big-b2small);
396
397    if (charge < 0.)
398    {
399       c1 = celectron[iZ][iT];
400       c2 = celectron[iZ+1][iT];
401       cc1 = c1+ratZ*(c2-c1);
402
403       c1 = celectron[iZ][iT+1];
404       c2 = celectron[iZ+1][iT+1];
405       cc2 = c1+ratZ*(c2-c1);
406
407       corr = cc1+ratb2*(cc2-cc1);
408
409       sigma *= sigmafactor/corr;
410    }
411    else             
412    {
413       c1 = cpositron[iZ][iT];
414       c2 = cpositron[iZ+1][iT];
415       cc1 = c1+ratZ*(c2-c1);
416
417       c1 = cpositron[iZ][iT+1];
418       c2 = cpositron[iZ+1][iT+1];
419       cc2 = c1+ratZ*(c2-c1);
420
421       corr = cc1+ratb2*(cc2-cc1);
422
423       sigma *= sigmafactor/corr;
424    }
425  }
426  else
427  {
428    c1 = bg2lim*sig0[iZ]*(1.+hecorr[iZ]*(beta2-beta2lim))/bg2;
429    c2 = bg2lim*sig0[iZ+1]*(1.+hecorr[iZ+1]*(beta2-beta2lim))/bg2;
430    if((AtomicNumber >= Z1) && (AtomicNumber <= Z2))
431      sigma = c1+ratZ*(c2-c1) ;
432    else if(AtomicNumber < Z1)
433      sigma = AtomicNumber*AtomicNumber*c1/(Z1*Z1);
434    else if(AtomicNumber > Z2)
435      sigma = AtomicNumber*AtomicNumber*c2/(Z2*Z2);
436  }
437  return sigma;
438
439}
440
441//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
442
443G4double G4UrbanMscModel92::ComputeTruePathLengthLimit(
444                             const G4Track& track,
445                             G4PhysicsTable* theTable,
446                             G4double currentMinimalStep)
447{
448  tPathLength = currentMinimalStep;
449  G4StepPoint* sp = track.GetStep()->GetPreStepPoint();
450  G4StepStatus stepStatus = sp->GetStepStatus();
451
452  const G4DynamicParticle* dp = track.GetDynamicParticle();
453
454  if(stepStatus == fUndefined) {
455    inside = false;
456    insideskin = false;
457    tlimit = geombig;
458    SetParticle( dp->GetDefinition() );
459  }
460
461  theLambdaTable = theTable;
462  couple = track.GetMaterialCutsCouple();
463  currentMaterialIndex = couple->GetIndex();
464  currentKinEnergy = dp->GetKineticEnergy();
465  currentRange = 
466    theManager->GetRangeFromRestricteDEDX(particle,currentKinEnergy,couple);
467  lambda0 = GetLambda(currentKinEnergy);
468
469  // stop here if small range particle
470  if(inside) return tPathLength;           
471 
472  if(tPathLength > currentRange) tPathLength = currentRange;
473
474  presafety = sp->GetSafety();
475
476  //    G4cout << "G4UrbanMscModel92::ComputeTruePathLengthLimit tPathLength= "
477  //       <<tPathLength<<" safety= " << presafety
478  //       << " range= " <<currentRange<<G4endl;
479
480  // far from geometry boundary
481  if(currentRange < presafety)
482    {
483      inside = true;
484      return tPathLength; 
485    }
486
487  // standard  version
488  //
489  if (steppingAlgorithm == fUseDistanceToBoundary)
490    {
491      //compute geomlimit and presafety
492      G4double geomlimit = ComputeGeomLimit(track, presafety, currentRange);
493
494      // is it far from boundary ?
495      if(currentRange < presafety)
496        {
497          inside = true;
498          return tPathLength;   
499        }
500
501      smallstep += 1.;
502      insideskin = false;
503
504      if((stepStatus == fGeomBoundary) || (stepStatus == fUndefined))
505        {
506          rangeinit = currentRange;
507          if(stepStatus == fUndefined) smallstep = 1.e10;
508          else  smallstep = 1.;
509
510          // constraint from the geometry
511          if((geomlimit < geombig) && (geomlimit > geommin))
512            {
513              if(stepStatus == fGeomBoundary) 
514                tgeom = geomlimit/facgeom;
515              else
516                tgeom = 2.*geomlimit/facgeom;
517            }
518            else
519              tgeom = geombig;
520
521          //define stepmin here (it depends on lambda!)
522          //rough estimation of lambda_elastic/lambda_transport
523          G4double rat = currentKinEnergy/MeV ;
524          rat = 1.e-3/(rat*(10.+rat)) ;
525          //stepmin ~ lambda_elastic
526          stepmin = rat*lambda0;
527          skindepth = skin*stepmin;
528
529          //define tlimitmin
530          tlimitmin = 10.*stepmin;
531          if(tlimitmin < tlimitminfix) tlimitmin = tlimitminfix;
532
533        }
534
535      //step limit
536      tlimit = facrange*rangeinit;             
537      if(tlimit < facsafety*presafety)
538        tlimit = facsafety*presafety; 
539
540      //lower limit for tlimit
541      if(tlimit < tlimitmin) tlimit = tlimitmin;
542
543      if(tlimit > tgeom) tlimit = tgeom;
544
545      //  G4cout << "tgeom= " << tgeom << " geomlimit= " << geomlimit 
546      //     << " tlimit= " << tlimit << " presafety= " << presafety << G4endl;
547
548      // shortcut
549      if((tPathLength < tlimit) && (tPathLength < presafety) &&
550         (smallstep >= skin) && (tPathLength < geomlimit-0.999*skindepth))
551        return tPathLength;   
552
553      // step reduction near to boundary
554      if(smallstep < skin)
555        {
556          tlimit = stepmin;
557          insideskin = true;
558        }
559      else if(geomlimit < geombig)
560        {
561          if(geomlimit > skindepth)
562            {
563              if(tlimit > geomlimit-0.999*skindepth)
564                tlimit = geomlimit-0.999*skindepth;
565            }
566          else
567            {
568              insideskin = true;
569              if(tlimit > stepmin) tlimit = stepmin;
570            }
571        }
572
573      if(tlimit < stepmin) tlimit = stepmin;
574
575      if(tPathLength > tlimit) tPathLength = tlimit  ; 
576
577    }
578    // for 'normal' simulation with or without magnetic field
579    //  there no small step/single scattering at boundaries
580  else if(steppingAlgorithm == fUseSafety)
581    {
582      // compute presafety again if presafety <= 0 and no boundary
583      // i.e. when it is needed for optimization purposes
584      if((stepStatus != fGeomBoundary) && (presafety < tlimitminfix)) 
585        presafety = ComputeSafety(sp->GetPosition(),tPathLength); 
586
587      // is far from boundary
588      if(currentRange < presafety)
589        {
590          inside = true;
591          return tPathLength; 
592        }
593
594      if((stepStatus == fGeomBoundary) || (stepStatus == fUndefined))
595      {
596        rangeinit = currentRange;
597        fr = facrange;
598        // 9.1 like stepping for e+/e- only (not for muons,hadrons)
599        if(mass < masslimite) 
600        {
601          if(lambda0 > currentRange)
602            rangeinit = lambda0;
603          if(lambda0 > lambdalimit)
604            fr *= 0.75+0.25*lambda0/lambdalimit;
605        }
606
607        //lower limit for tlimit
608        G4double rat = currentKinEnergy/MeV ;
609        rat = 1.e-3/(rat*(10.+rat)) ;
610        tlimitmin = 10.*lambda0*rat;
611        if(tlimitmin < tlimitminfix) tlimitmin = tlimitminfix;
612      }
613      //step limit
614      tlimit = fr*rangeinit;               
615
616      if(tlimit < facsafety*presafety)
617        tlimit = facsafety*presafety;
618
619      //lower limit for tlimit
620      if(tlimit < tlimitmin) tlimit = tlimitmin;
621
622      if(tPathLength > tlimit) tPathLength = tlimit;
623    }
624 
625  // version similar to 7.1 (needed for some experiments)
626  else
627    {
628      if (stepStatus == fGeomBoundary)
629        {
630          if (currentRange > lambda0) tlimit = facrange*currentRange;
631          else                        tlimit = facrange*lambda0;
632
633          if(tlimit < tlimitmin) tlimit = tlimitmin;
634          if(tPathLength > tlimit) tPathLength = tlimit;
635        }
636    }
637  // G4cout << "tPathLength= " << tPathLength << "  geomlimit= " << geomlimit
638  //     << " currentMinimalStep= " << currentMinimalStep << G4endl;
639  return tPathLength ;
640}
641
642//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
643
644G4double G4UrbanMscModel92::ComputeGeomPathLength(G4double)
645{
646  lambdaeff = lambda0;
647  par1 = -1. ; 
648  par2 = par3 = 0. ; 
649
650  //  do the true -> geom transformation
651  zPathLength = tPathLength;
652
653  // z = t for very small tPathLength
654  if(tPathLength < tlimitminfix) return zPathLength;
655
656  // this correction needed to run MSC with eIoni and eBrem inactivated
657  // and makes no harm for a normal run
658  if(tPathLength > currentRange)
659    tPathLength = currentRange ;
660
661  G4double tau   = tPathLength/lambda0 ;
662
663  if ((tau <= tausmall) || insideskin) {
664    zPathLength  = tPathLength;
665    if(zPathLength > lambda0) zPathLength = lambda0;
666    return zPathLength;
667  }
668
669  G4double zmean = tPathLength;
670  if (tPathLength < currentRange*dtrl) {
671    if(tau < taulim) zmean = tPathLength*(1.-0.5*tau) ;
672    else             zmean = lambda0*(1.-exp(-tau));
673  } else if(currentKinEnergy < mass)  {
674    par1 = 1./currentRange ;
675    par2 = 1./(par1*lambda0) ;
676    par3 = 1.+par2 ;
677    if(tPathLength < currentRange)
678      zmean = (1.-exp(par3*log(1.-tPathLength/currentRange)))/(par1*par3) ;
679    else
680      zmean = 1./(par1*par3) ;
681  } else {
682    G4double T1 = theManager->GetEnergy(particle,currentRange-tPathLength,couple);
683    G4double lambda1 = GetLambda(T1);
684
685    par1 = (lambda0-lambda1)/(lambda0*tPathLength) ;
686    par2 = 1./(par1*lambda0) ;
687    par3 = 1.+par2 ;
688    zmean = (1.-exp(par3*log(lambda1/lambda0)))/(par1*par3) ;
689  }
690
691  zPathLength = zmean ;
692
693  //  sample z
694  if(samplez)
695  {
696    const G4double  ztmax = 0.99 ;
697    G4double zt = zmean/tPathLength ;
698
699    if (tPathLength > stepmin && zt < ztmax)             
700    {
701      G4double u,cz1;
702      if(zt >= third)
703      {
704        G4double cz = 0.5*(3.*zt-1.)/(1.-zt) ;
705        cz1 = 1.+cz ;
706        G4double u0 = cz/cz1 ;
707        G4double grej ;
708        do {
709            u = exp(log(G4UniformRand())/cz1) ;
710            grej = exp(cz*log(u/u0))*(1.-u)/(1.-u0) ;
711           } while (grej < G4UniformRand()) ;
712      }
713      else
714      {
715        cz1 = 1./zt-1.;
716        u = 1.-exp(log(G4UniformRand())/cz1) ;
717      }
718      zPathLength = tPathLength*u ;
719    }
720  }
721
722  if(zPathLength > lambda0) zPathLength = lambda0;
723
724  return zPathLength;
725}
726
727//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
728
729G4double G4UrbanMscModel92::ComputeTrueStepLength(G4double geomStepLength)
730{
731  // step defined other than transportation
732  if(geomStepLength == zPathLength && tPathLength <= currentRange)
733    return tPathLength;
734
735  // t = z for very small step
736  zPathLength = geomStepLength;
737  tPathLength = geomStepLength;
738  if(geomStepLength < tlimitminfix) return tPathLength;
739 
740  // recalculation
741  if((geomStepLength > lambda0*tausmall) && !insideskin)
742  {
743    if(par1 <  0.)
744      tPathLength = -lambda0*log(1.-geomStepLength/lambda0) ;
745    else 
746    {
747      if(par1*par3*geomStepLength < 1.)
748        tPathLength = (1.-exp(log(1.-par1*par3*geomStepLength)/par3))/par1 ;
749      else 
750        tPathLength = currentRange;
751    } 
752  }
753  if(tPathLength < geomStepLength) tPathLength = geomStepLength;
754
755  return tPathLength;
756}
757
758//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
759
760G4double G4UrbanMscModel92::ComputeTheta0(G4double trueStepLength,
761                                          G4double KineticEnergy)
762{
763  // for all particles take the width of the central part
764  //  from a  parametrization similar to the Highland formula
765  // ( Highland formula: Particle Physics Booklet, July 2002, eq. 26.10)
766  const G4double c_highland = 13.6*MeV ;
767  G4double betacp = sqrt(currentKinEnergy*(currentKinEnergy+2.*mass)*
768                         KineticEnergy*(KineticEnergy+2.*mass)/
769                      ((currentKinEnergy+mass)*(KineticEnergy+mass)));
770  y = trueStepLength/currentRadLength;
771  G4double theta0 = c_highland*std::abs(charge)*sqrt(y)/betacp;
772  y = log(y);
773  // correction factor from e-/proton scattering data
774  G4double corr = coeffth1+coeffth2*y;               
775  if(y < -6.5) corr -= 0.011*(6.5+y);
776  theta0 *= corr ;                                               
777
778  return theta0;
779}
780
781//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
782
783void G4UrbanMscModel92::SampleScattering(const G4DynamicParticle* dynParticle,
784                                         G4double safety)
785{
786  G4double kineticEnergy = dynParticle->GetKineticEnergy();
787
788  if((kineticEnergy <= 0.0) || (tPathLength <= tlimitminfix) ||
789     (tPathLength/tausmall < lambda0)) return;
790
791  G4double cth  = SampleCosineTheta(tPathLength,kineticEnergy);
792
793  // protection against 'bad' cth values
794  if(std::abs(cth) > 1.) return;
795
796  G4double sth  = sqrt((1.0 - cth)*(1.0 + cth));
797  G4double phi  = twopi*G4UniformRand();
798  G4double dirx = sth*cos(phi);
799  G4double diry = sth*sin(phi);
800
801  G4ThreeVector oldDirection = dynParticle->GetMomentumDirection();
802  G4ThreeVector newDirection(dirx,diry,cth);
803  newDirection.rotateUz(oldDirection);
804  fParticleChange->ProposeMomentumDirection(newDirection);
805
806  if (latDisplasment && safety > tlimitminfix) {
807
808    G4double r = SampleDisplacement();
809    /*
810    G4cout << "G4UrbanMscModel92::SampleSecondaries: e(MeV)= " << kineticEnergy
811           << " sinTheta= " << sth << " r(mm)= " << r
812           << " trueStep(mm)= " << tPathLength
813           << " geomStep(mm)= " << zPathLength
814           << G4endl;
815    */
816    if(r > 0.)
817      {
818        G4double latcorr = LatCorrelation();
819        if(latcorr > r) latcorr = r;
820
821        // sample direction of lateral displacement
822        // compute it from the lateral correlation
823        G4double Phi = 0.;
824        if(std::abs(r*sth) < latcorr)
825          Phi  = twopi*G4UniformRand();
826        else
827        {
828          G4double psi = std::acos(latcorr/(r*sth));
829          if(G4UniformRand() < 0.5)
830            Phi = phi+psi;
831          else
832            Phi = phi-psi;
833        }
834
835        dirx = std::cos(Phi);
836        diry = std::sin(Phi);
837
838        G4ThreeVector latDirection(dirx,diry,0.0);
839        latDirection.rotateUz(oldDirection);
840
841        ComputeDisplacement(fParticleChange, latDirection, r, safety);
842      }
843  }
844}
845
846//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
847
848G4double G4UrbanMscModel92::SampleCosineTheta(G4double trueStepLength,
849                                              G4double KineticEnergy)
850{
851  G4double cth = 1. ;
852  G4double tau = trueStepLength/lambda0 ;
853
854  Zeff = couple->GetMaterial()->GetTotNbOfElectPerVolume()/
855         couple->GetMaterial()->GetTotNbOfAtomsPerVolume() ;
856
857  if(Zold != Zeff) 
858    UpdateCache();
859
860  if(insideskin)
861  {
862    //no scattering, single or plural scattering
863    G4double mean = trueStepLength/stepmin ;
864
865    G4int n = G4Poisson(mean);
866    if(n > 0)
867    {
868      //screening (Moliere-Bethe)
869      G4double mom2 = KineticEnergy*(2.*mass+KineticEnergy);
870      G4double beta2 = mom2/((KineticEnergy+mass)*(KineticEnergy+mass));
871      G4double ascr = scr1/mom2;
872      ascr *= 1.13+scr2/beta2;
873      G4double ascr1 = 1.+2.*ascr;
874      G4double bp1=ascr1+1.;
875      G4double bm1=ascr1-1.;
876
877      // single scattering from screened Rutherford x-section
878      G4double ct,st,phi;
879      G4double sx=0.,sy=0.,sz=0.;
880      for(G4int i=1; i<=n; i++)
881      {
882        ct = ascr1-bp1*bm1/(2.*G4UniformRand()+bm1);
883        if(ct < -1.) ct = -1.;
884        if(ct >  1.) ct =  1.; 
885        st = sqrt(1.-ct*ct);
886        phi = twopi*G4UniformRand();
887        sx += st*cos(phi);
888        sy += st*sin(phi);
889        sz += ct;
890      }
891      cth = sz/sqrt(sx*sx+sy*sy+sz*sz);
892    }
893  }
894  else
895  {
896    if(trueStepLength >= currentRange*dtrl) 
897    {
898      if(par1*trueStepLength < 1.)
899        tau = -par2*log(1.-par1*trueStepLength) ;
900      // for the case if ioni/brems are inactivated
901      // see the corresponding condition in ComputeGeomPathLength
902      else if(1.-KineticEnergy/currentKinEnergy > taulim)
903        tau = taubig ;
904    }
905    currentTau = tau ;
906    lambdaeff = trueStepLength/currentTau;
907    currentRadLength = couple->GetMaterial()->GetRadlen();
908
909    if (tau >= taubig) cth = -1.+2.*G4UniformRand();
910    else if (tau >= tausmall)
911    {
912      G4double xsi = 3.0; 
913      G4double x0 = 1.;
914      G4double a = 1., ea = 0., eaa = 1.;
915      G4double b=2.,b1=3.,bx=1.,eb1=3.,ebx=1.;
916      G4double prob = 1. , qprob = 1. ;
917      G4double xmean1 = 1., xmean2 = 0.;
918      G4double xmeanth = exp(-tau);
919      G4double x2meanth = (1.+2.*exp(-2.5*tau))/3.;
920
921      G4double relloss = 1.-KineticEnergy/currentKinEnergy;
922      if(relloss > rellossmax) 
923        return SimpleScattering(xmeanth,x2meanth);
924
925      G4double theta0 = ComputeTheta0(trueStepLength,KineticEnergy);
926
927      // protection for very small angles
928      if(theta0 < tausmall) return cth;
929   
930      if(theta0 > theta0max)
931        return SimpleScattering(xmeanth,x2meanth);
932      G4double sth = sin(0.5*theta0);
933      a = 0.25/(sth*sth);
934
935      ea = exp(-xsi);
936      eaa = 1.-ea ;
937      xmean1 = 1.-(1.-(1.+xsi)*ea)/(a*eaa);
938      x0 = 1.-xsi/a;
939
940      if(xmean1 <= 0.999*xmeanth)
941        return SimpleScattering(xmeanth,x2meanth);
942
943      // from MUSCAT H,Be,Fe data
944      G4double c = coeffc1;                         
945      if(y > -13.5) 
946        c += coeffc2*exp(3.*log(y+13.5));
947
948      if(abs(c-3.) < 0.001)  c = 3.001;     
949      if(abs(c-2.) < 0.001)  c = 2.001;     
950
951      G4double c1 = c-1.;
952
953      //from continuity of derivatives
954      b = 1.+(c-xsi)/a;
955
956      b1 = b+1.;
957      bx = c/a;
958      eb1 = exp(c1*log(b1));
959      ebx = exp(c1*log(bx));
960
961      xmean2 = (x0*eb1+ebx-(eb1*bx-b1*ebx)/(c-2.))/(eb1-ebx);
962     
963      G4double f1x0 = a*ea/eaa;
964      G4double f2x0 = c1*eb1/(bx*(eb1-ebx));
965      prob = f2x0/(f1x0+f2x0);
966
967      qprob = xmeanth/(prob*xmean1+(1.-prob)*xmean2);
968
969      // sampling of costheta
970      if(G4UniformRand() < qprob)
971      {
972        if(G4UniformRand() < prob)
973          cth = 1.+log(ea+G4UniformRand()*eaa)/a ;
974        else
975          cth = b-b1*bx/exp(log(ebx+(eb1-ebx)*G4UniformRand())/c1) ;
976      }
977      else
978        cth = -1.+2.*G4UniformRand();
979    }
980  } 
981  return cth ;
982}
983
984//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
985
986G4double G4UrbanMscModel92::SimpleScattering(G4double xmeanth,G4double x2meanth)
987{
988  // 'large angle scattering'
989  // 2 model functions with correct xmean and x2mean
990  G4double a = (2.*xmeanth+9.*x2meanth-3.)/(2.*xmeanth-3.*x2meanth+1.);
991  G4double prob = (a+2.)*xmeanth/a;
992
993  // sampling
994  G4double cth = 1.;
995  if(G4UniformRand() < prob)
996    cth = -1.+2.*exp(log(G4UniformRand())/(a+1.));
997  else
998    cth = -1.+2.*G4UniformRand();
999  return cth;
1000}
1001
1002//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
1003
1004G4double G4UrbanMscModel92::SampleDisplacement()
1005{
1006  const G4double kappa = 2.5;
1007  const G4double kappapl1 = kappa+1.;
1008  const G4double kappami1 = kappa-1.;
1009  G4double rmean = 0.0;
1010  if ((currentTau >= tausmall) && !insideskin) {
1011    if (currentTau < taulim) {
1012      rmean = kappa*currentTau*currentTau*currentTau*
1013             (1.-kappapl1*currentTau*0.25)/6. ;
1014
1015    } else {
1016      G4double etau = 0.0;
1017      if (currentTau<taubig) etau = exp(-currentTau);
1018      rmean = -kappa*currentTau;
1019      rmean = -exp(rmean)/(kappa*kappami1);
1020      rmean += currentTau-kappapl1/kappa+kappa*etau/kappami1;
1021    }
1022    if (rmean>0.) rmean = 2.*lambdaeff*sqrt(rmean/3.0);
1023    else          rmean = 0.;
1024  }
1025
1026  // protection against z > t ...........................
1027  if(rmean > 0.) {
1028    G4double zt = (tPathLength-zPathLength)*(tPathLength+zPathLength);
1029    if(zt <= 0.)
1030      rmean = 0.;
1031    else if(rmean*rmean > zt)
1032      rmean = sqrt(zt);
1033  }
1034  return rmean;
1035}
1036
1037//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
1038
1039G4double G4UrbanMscModel92::LatCorrelation()
1040{
1041  const G4double kappa = 2.5;
1042  const G4double kappami1 = kappa-1.;
1043
1044  G4double latcorr = 0.;
1045  if((currentTau >= tausmall) && !insideskin)
1046  {
1047    if(currentTau < taulim)
1048      latcorr = lambdaeff*kappa*currentTau*currentTau*
1049                (1.-(kappa+1.)*currentTau/3.)/3.;
1050    else
1051    {
1052      G4double etau = 0.;
1053      if(currentTau < taubig) etau = exp(-currentTau);
1054      latcorr = -kappa*currentTau;
1055      latcorr = exp(latcorr)/kappami1;
1056      latcorr += 1.-kappa*etau/kappami1 ;
1057      latcorr *= 2.*lambdaeff/3. ;
1058    }
1059  }
1060
1061  return latcorr;
1062}
1063
1064//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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