source: trunk/source/processes/electromagnetic/standard/src/G4UrbanMscModel2.cc @ 1006

Last change on this file since 1006 was 1006, checked in by garnier, 15 years ago

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25//
26//
27// $Id: G4UrbanMscModel2.cc,v 1.18 2008/12/18 13:01:36 gunter Exp $
28// GEANT4 tag $Name: geant4-09-02-ref-02 $
29//
30// -------------------------------------------------------------------
31//
32// GEANT4 Class file
33//
34//
35// File name:   G4UrbanMscModel2
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// Class Description:
88//
89// Implementation of the model of multiple scattering based on
90// H.W.Lewis Phys Rev 78 (1950) 526 and others
91
92// -------------------------------------------------------------------
93// In its present form the model can be  used for simulation
94//   of the e-/e+, muon and charged hadron multiple scattering
95//
96
97
98//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
99//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
100
101#include "G4UrbanMscModel2.hh"
102#include "Randomize.hh"
103#include "G4Electron.hh"
104#include "G4LossTableManager.hh"
105#include "G4ParticleChangeForMSC.hh"
106#include "G4TransportationManager.hh"
107#include "G4SafetyHelper.hh"
108
109#include "G4Poisson.hh"
110#include "globals.hh"
111
112//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
113
114using namespace std;
115
116G4UrbanMscModel2::G4UrbanMscModel2(const G4String& nam)
117  : G4VMscModel(nam),
118    isInitialized(false)
119{
120  masslimite    = 0.6*MeV;
121  lambdalimit   = 1.*mm;
122  fr            = 0.02;
123  facsafety     = 0.3;
124  taubig        = 8.0;
125  tausmall      = 1.e-16;
126  taulim        = 1.e-6;
127  currentTau    = taulim;
128  tlimitminfix  = 1.e-6*mm;           
129  stepmin       = tlimitminfix;
130  smallstep     = 1.e10;
131  currentRange  = 0. ;
132  rangeinit     = 0.;
133  tlimit        = 1.e10*mm;
134  tlimitmin     = 10.*tlimitminfix;           
135  tgeom         = 1.e50*mm;
136  geombig       = 1.e50*mm;
137  geommin       = 1.e-3*mm;
138  geomlimit     = geombig;
139  presafety     = 0.*mm;
140                         
141  y             = 0.;
142
143  Zold          = 0.;
144  Zeff          = 1.;
145  Z2            = 1.;               
146  Z23           = 1.;                   
147  lnZ           = 0.;
148  coeffth1      = 0.;
149  coeffth2      = 0.;
150  coeffc1       = 0.;
151  coeffc2       = 0.;
152  scr1ini       = fine_structure_const*fine_structure_const*
153                  electron_mass_c2*electron_mass_c2/(0.885*0.885*4.*pi);
154  scr2ini       = 3.76*fine_structure_const*fine_structure_const;
155  scr1          = 0.;
156  scr2          = 0.;
157
158  theta0max     = pi/6.;
159  rellossmax    = 0.50;
160  third         = 1./3.;
161  particle      = 0;
162  theManager    = G4LossTableManager::Instance(); 
163  inside        = false; 
164  insideskin    = false;
165
166}
167
168//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
169
170G4UrbanMscModel2::~G4UrbanMscModel2()
171{}
172
173//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
174
175void G4UrbanMscModel2::Initialise(const G4ParticleDefinition* p,
176                                  const G4DataVector&)
177{
178  skindepth = skin*stepmin;
179  if(isInitialized) return;
180  // set values of some data members
181  SetParticle(p);
182
183  if (pParticleChange)
184   fParticleChange = reinterpret_cast<G4ParticleChangeForMSC*>(pParticleChange);
185  else
186   fParticleChange = new G4ParticleChangeForMSC();
187
188  safetyHelper = G4TransportationManager::GetTransportationManager()
189    ->GetSafetyHelper();
190  safetyHelper->InitialiseHelper();
191
192  isInitialized = true;
193}
194
195//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
196
197G4double G4UrbanMscModel2::ComputeCrossSectionPerAtom( 
198                             const G4ParticleDefinition* part,
199                                   G4double KineticEnergy,
200                                   G4double AtomicNumber,G4double,
201                                   G4double, G4double)
202{
203  const G4double sigmafactor = twopi*classic_electr_radius*classic_electr_radius;
204  const G4double epsfactor = 2.*electron_mass_c2*electron_mass_c2*
205                            Bohr_radius*Bohr_radius/(hbarc*hbarc);
206  const G4double epsmin = 1.e-4 , epsmax = 1.e10;
207
208  const G4double Zdat[15] = { 4.,  6., 13., 20., 26., 29., 32., 38., 47.,
209                             50., 56., 64., 74., 79., 82. };
210
211  const G4double Tdat[22] = { 100*eV,  200*eV,  400*eV,  700*eV,
212                               1*keV,   2*keV,   4*keV,   7*keV,
213                              10*keV,  20*keV,  40*keV,  70*keV,
214                             100*keV, 200*keV, 400*keV, 700*keV,
215                               1*MeV,   2*MeV,   4*MeV,   7*MeV,
216                              10*MeV,  20*MeV};
217
218  // corr. factors for e-/e+ lambda for T <= Tlim
219          G4double celectron[15][22] =
220          {{1.125,1.072,1.051,1.047,1.047,1.050,1.052,1.054,
221            1.054,1.057,1.062,1.069,1.075,1.090,1.105,1.111,
222            1.112,1.108,1.100,1.093,1.089,1.087            },
223           {1.408,1.246,1.143,1.096,1.077,1.059,1.053,1.051,
224            1.052,1.053,1.058,1.065,1.072,1.087,1.101,1.108,
225            1.109,1.105,1.097,1.090,1.086,1.082            },
226           {2.833,2.268,1.861,1.612,1.486,1.309,1.204,1.156,
227            1.136,1.114,1.106,1.106,1.109,1.119,1.129,1.132,
228            1.131,1.124,1.113,1.104,1.099,1.098            },
229           {3.879,3.016,2.380,2.007,1.818,1.535,1.340,1.236,
230            1.190,1.133,1.107,1.099,1.098,1.103,1.110,1.113,
231            1.112,1.105,1.096,1.089,1.085,1.098            },
232           {6.937,4.330,2.886,2.256,1.987,1.628,1.395,1.265,
233            1.203,1.122,1.080,1.065,1.061,1.063,1.070,1.073,
234            1.073,1.070,1.064,1.059,1.056,1.056            },
235           {9.616,5.708,3.424,2.551,2.204,1.762,1.485,1.330,
236            1.256,1.155,1.099,1.077,1.070,1.068,1.072,1.074,
237            1.074,1.070,1.063,1.059,1.056,1.052            },
238           {11.72,6.364,3.811,2.806,2.401,1.884,1.564,1.386,
239            1.300,1.180,1.112,1.082,1.073,1.066,1.068,1.069,
240            1.068,1.064,1.059,1.054,1.051,1.050            },
241           {18.08,8.601,4.569,3.183,2.662,2.025,1.646,1.439,
242            1.339,1.195,1.108,1.068,1.053,1.040,1.039,1.039,
243            1.039,1.037,1.034,1.031,1.030,1.036            },
244           {18.22,10.48,5.333,3.713,3.115,2.367,1.898,1.631,
245            1.498,1.301,1.171,1.105,1.077,1.048,1.036,1.033,
246            1.031,1.028,1.024,1.022,1.021,1.024            },
247           {14.14,10.65,5.710,3.929,3.266,2.453,1.951,1.669,
248            1.528,1.319,1.178,1.106,1.075,1.040,1.027,1.022,
249            1.020,1.017,1.015,1.013,1.013,1.020            },
250           {14.11,11.73,6.312,4.240,3.478,2.566,2.022,1.720,
251            1.569,1.342,1.186,1.102,1.065,1.022,1.003,0.997,
252            0.995,0.993,0.993,0.993,0.993,1.011            },
253           {22.76,20.01,8.835,5.287,4.144,2.901,2.219,1.855,
254            1.677,1.410,1.224,1.121,1.073,1.014,0.986,0.976,
255            0.974,0.972,0.973,0.974,0.975,0.987            },
256           {50.77,40.85,14.13,7.184,5.284,3.435,2.520,2.059,
257            1.837,1.512,1.283,1.153,1.091,1.010,0.969,0.954,
258            0.950,0.947,0.949,0.952,0.954,0.963            },
259           {65.87,59.06,15.87,7.570,5.567,3.650,2.682,2.182,
260            1.939,1.579,1.325,1.178,1.108,1.014,0.965,0.947,
261            0.941,0.938,0.940,0.944,0.946,0.954            },
262           {55.60,47.34,15.92,7.810,5.755,3.767,2.760,2.239,
263            1.985,1.609,1.343,1.188,1.113,1.013,0.960,0.939,
264            0.933,0.930,0.933,0.936,0.939,0.949            }};
265           
266           G4double cpositron[15][22] = {
267           {2.589,2.044,1.658,1.446,1.347,1.217,1.144,1.110,
268            1.097,1.083,1.080,1.086,1.092,1.108,1.123,1.131,
269            1.131,1.126,1.117,1.108,1.103,1.100            },
270           {3.904,2.794,2.079,1.710,1.543,1.325,1.202,1.145,
271            1.122,1.096,1.089,1.092,1.098,1.114,1.130,1.137,
272            1.138,1.132,1.122,1.113,1.108,1.102            },
273           {7.970,6.080,4.442,3.398,2.872,2.127,1.672,1.451,
274            1.357,1.246,1.194,1.179,1.178,1.188,1.201,1.205,
275            1.203,1.190,1.173,1.159,1.151,1.145            },
276           {9.714,7.607,5.747,4.493,3.815,2.777,2.079,1.715,
277            1.553,1.353,1.253,1.219,1.211,1.214,1.225,1.228,
278            1.225,1.210,1.191,1.175,1.166,1.174            },
279           {17.97,12.95,8.628,6.065,4.849,3.222,2.275,1.820,
280            1.624,1.382,1.259,1.214,1.202,1.202,1.214,1.219,
281            1.217,1.203,1.184,1.169,1.160,1.151            },
282           {24.83,17.06,10.84,7.355,5.767,3.707,2.546,1.996,
283            1.759,1.465,1.311,1.252,1.234,1.228,1.238,1.241,
284            1.237,1.222,1.201,1.184,1.174,1.159            },
285           {23.26,17.15,11.52,8.049,6.375,4.114,2.792,2.155,
286            1.880,1.535,1.353,1.281,1.258,1.247,1.254,1.256,
287            1.252,1.234,1.212,1.194,1.183,1.170            },
288           {22.33,18.01,12.86,9.212,7.336,4.702,3.117,2.348,
289            2.015,1.602,1.385,1.297,1.268,1.251,1.256,1.258,
290            1.254,1.237,1.214,1.195,1.185,1.179            },
291           {33.91,24.13,15.71,10.80,8.507,5.467,3.692,2.808,
292            2.407,1.873,1.564,1.425,1.374,1.330,1.324,1.320,
293            1.312,1.288,1.258,1.235,1.221,1.205            },
294           {32.14,24.11,16.30,11.40,9.015,5.782,3.868,2.917,
295            2.490,1.925,1.596,1.447,1.391,1.342,1.332,1.327,
296            1.320,1.294,1.264,1.240,1.226,1.214            },
297           {29.51,24.07,17.19,12.28,9.766,6.238,4.112,3.066,
298            2.602,1.995,1.641,1.477,1.414,1.356,1.342,1.336,
299            1.328,1.302,1.270,1.245,1.231,1.233            },
300           {38.19,30.85,21.76,15.35,12.07,7.521,4.812,3.498,
301            2.926,2.188,1.763,1.563,1.484,1.405,1.382,1.371,
302            1.361,1.330,1.294,1.267,1.251,1.239            },
303           {49.71,39.80,27.96,19.63,15.36,9.407,5.863,4.155,
304            3.417,2.478,1.944,1.692,1.589,1.480,1.441,1.423,
305            1.409,1.372,1.330,1.298,1.280,1.258            },
306           {59.25,45.08,30.36,20.83,16.15,9.834,6.166,4.407,
307            3.641,2.648,2.064,1.779,1.661,1.531,1.482,1.459,
308            1.442,1.400,1.354,1.319,1.299,1.272            },
309           {56.38,44.29,30.50,21.18,16.51,10.11,6.354,4.542,
310            3.752,2.724,2.116,1.817,1.692,1.554,1.499,1.474,
311            1.456,1.412,1.364,1.328,1.307,1.282            }};
312
313  //data/corrections for T > Tlim 
314  G4double Tlim = 10.*MeV;
315  G4double beta2lim = Tlim*(Tlim+2.*electron_mass_c2)/
316                      ((Tlim+electron_mass_c2)*(Tlim+electron_mass_c2));
317  G4double bg2lim   = Tlim*(Tlim+2.*electron_mass_c2)/
318                      (electron_mass_c2*electron_mass_c2);
319
320  G4double sig0[15] = {0.2672*barn,  0.5922*barn, 2.653*barn,  6.235*barn,
321                      11.69*barn  , 13.24*barn  , 16.12*barn, 23.00*barn ,
322                      35.13*barn  , 39.95*barn  , 50.85*barn, 67.19*barn ,
323                      91.15*barn  , 104.4*barn  , 113.1*barn};
324                                       
325  G4double hecorr[15] = {120.70, 117.50, 105.00, 92.92, 79.23,  74.510,  68.29,
326                          57.39,  41.97,  36.14, 24.53, 10.21,  -7.855, -16.84,
327                         -22.30};
328
329  G4double sigma;
330  SetParticle(part);
331
332  G4double Z23 = 2.*log(AtomicNumber)/3.; Z23 = exp(Z23);
333
334  // correction if particle .ne. e-/e+
335  // compute equivalent kinetic energy
336  // lambda depends on p*beta ....
337
338  G4double eKineticEnergy = KineticEnergy;
339
340  if(mass > electron_mass_c2)
341  {
342     G4double TAU = KineticEnergy/mass ;
343     G4double c = mass*TAU*(TAU+2.)/(electron_mass_c2*(TAU+1.)) ;
344     G4double w = c-2. ;
345     G4double tau = 0.5*(w+sqrt(w*w+4.*c)) ;
346     eKineticEnergy = electron_mass_c2*tau ;
347  }
348
349  G4double eTotalEnergy = eKineticEnergy + electron_mass_c2 ;
350  G4double beta2 = eKineticEnergy*(eTotalEnergy+electron_mass_c2)
351                                 /(eTotalEnergy*eTotalEnergy);
352  G4double bg2   = eKineticEnergy*(eTotalEnergy+electron_mass_c2)
353                                 /(electron_mass_c2*electron_mass_c2);
354
355  G4double eps = epsfactor*bg2/Z23;
356
357  if     (eps<epsmin)  sigma = 2.*eps*eps;
358  else if(eps<epsmax)  sigma = log(1.+2.*eps)-2.*eps/(1.+2.*eps);
359  else                 sigma = log(2.*eps)-1.+1./eps;
360
361  sigma *= ChargeSquare*AtomicNumber*AtomicNumber/(beta2*bg2);
362
363  // interpolate in AtomicNumber and beta2
364  G4double c1,c2,cc1,cc2,corr;
365
366  // get bin number in Z
367  G4int iZ = 14;
368  while ((iZ>=0)&&(Zdat[iZ]>=AtomicNumber)) iZ -= 1;
369  if (iZ==14)                               iZ = 13;
370  if (iZ==-1)                               iZ = 0 ;
371
372  G4double Z1 = Zdat[iZ];
373  G4double Z2 = Zdat[iZ+1];
374  G4double ratZ = (AtomicNumber-Z1)*(AtomicNumber+Z1)/
375                  ((Z2-Z1)*(Z2+Z1));
376
377  if(eKineticEnergy <= Tlim) 
378  {
379    // get bin number in T (beta2)
380    G4int iT = 21;
381    while ((iT>=0)&&(Tdat[iT]>=eKineticEnergy)) iT -= 1;
382    if(iT==21)                                  iT = 20;
383    if(iT==-1)                                  iT = 0 ;
384
385    //  calculate betasquare values
386    G4double T = Tdat[iT],   E = T + electron_mass_c2;
387    G4double b2small = T*(E+electron_mass_c2)/(E*E);
388
389    T = Tdat[iT+1]; E = T + electron_mass_c2;
390    G4double b2big = T*(E+electron_mass_c2)/(E*E);
391    G4double ratb2 = (beta2-b2small)/(b2big-b2small);
392
393    if (charge < 0.)
394    {
395       c1 = celectron[iZ][iT];
396       c2 = celectron[iZ+1][iT];
397       cc1 = c1+ratZ*(c2-c1);
398
399       c1 = celectron[iZ][iT+1];
400       c2 = celectron[iZ+1][iT+1];
401       cc2 = c1+ratZ*(c2-c1);
402
403       corr = cc1+ratb2*(cc2-cc1);
404
405       sigma *= sigmafactor/corr;
406    }
407    else             
408    {
409       c1 = cpositron[iZ][iT];
410       c2 = cpositron[iZ+1][iT];
411       cc1 = c1+ratZ*(c2-c1);
412
413       c1 = cpositron[iZ][iT+1];
414       c2 = cpositron[iZ+1][iT+1];
415       cc2 = c1+ratZ*(c2-c1);
416
417       corr = cc1+ratb2*(cc2-cc1);
418
419       sigma *= sigmafactor/corr;
420    }
421  }
422  else
423  {
424    c1 = bg2lim*sig0[iZ]*(1.+hecorr[iZ]*(beta2-beta2lim))/bg2;
425    c2 = bg2lim*sig0[iZ+1]*(1.+hecorr[iZ+1]*(beta2-beta2lim))/bg2;
426    if((AtomicNumber >= Z1) && (AtomicNumber <= Z2))
427      sigma = c1+ratZ*(c2-c1) ;
428    else if(AtomicNumber < Z1)
429      sigma = AtomicNumber*AtomicNumber*c1/(Z1*Z1);
430    else if(AtomicNumber > Z2)
431      sigma = AtomicNumber*AtomicNumber*c2/(Z2*Z2);
432  }
433  return sigma;
434
435}
436
437//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
438
439G4double G4UrbanMscModel2::ComputeTruePathLengthLimit(
440                             const G4Track& track,
441                             G4PhysicsTable* theTable,
442                             G4double currentMinimalStep)
443{
444  tPathLength = currentMinimalStep;
445  G4StepPoint* sp = track.GetStep()->GetPreStepPoint();
446  G4StepStatus stepStatus = sp->GetStepStatus();
447
448  const G4DynamicParticle* dp = track.GetDynamicParticle();
449
450  if(stepStatus == fUndefined) {
451    inside = false;
452    insideskin = false;
453    tlimit = geombig;
454    SetParticle( dp->GetDefinition() );
455  }
456
457  theLambdaTable = theTable;
458  couple = track.GetMaterialCutsCouple();
459  currentMaterialIndex = couple->GetIndex();
460  currentKinEnergy = dp->GetKineticEnergy();
461  currentRange = 
462    theManager->GetRangeFromRestricteDEDX(particle,currentKinEnergy,couple);
463  lambda0 = GetLambda(currentKinEnergy);
464
465  // stop here if small range particle
466  if(inside) return tPathLength;           
467 
468  if(tPathLength > currentRange) tPathLength = currentRange;
469
470  presafety = sp->GetSafety();
471
472  //    G4cout << "G4UrbanMscModel2::ComputeTruePathLengthLimit tPathLength= "
473  //       <<tPathLength<<" safety= " << presafety
474  //       << " range= " <<currentRange<<G4endl;
475
476  // far from geometry boundary
477  if(currentRange < presafety)
478    {
479      inside = true;
480      return tPathLength; 
481    }
482
483  // standard  version
484  //
485  if (steppingAlgorithm == fUseDistanceToBoundary)
486    {
487      //compute geomlimit and presafety
488      GeomLimit(track);
489
490      // is it far from boundary ?
491      if(currentRange < presafety)
492        {
493          inside = true;
494          return tPathLength;   
495        }
496
497      smallstep += 1.;
498      insideskin = false;
499
500      if((stepStatus == fGeomBoundary) || (stepStatus == fUndefined))
501        {
502          rangeinit = currentRange;
503          if(stepStatus == fUndefined) smallstep = 1.e10;
504          else  smallstep = 1.;
505
506          // constraint from the geometry
507          if((geomlimit < geombig) && (geomlimit > geommin))
508            {
509              if(stepStatus == fGeomBoundary) 
510                tgeom = geomlimit/facgeom;
511              else
512                tgeom = 2.*geomlimit/facgeom;
513            }
514            else
515              tgeom = geombig;
516
517          //define stepmin here (it depends on lambda!)
518          //rough estimation of lambda_elastic/lambda_transport
519          G4double rat = currentKinEnergy/MeV ;
520          rat = 1.e-3/(rat*(10.+rat)) ;
521          //stepmin ~ lambda_elastic
522          stepmin = rat*lambda0;
523          skindepth = skin*stepmin;
524
525          //define tlimitmin
526          tlimitmin = 10.*stepmin;
527          if(tlimitmin < tlimitminfix) tlimitmin = tlimitminfix;
528
529        }
530
531      //step limit
532      tlimit = facrange*rangeinit;             
533      if(tlimit < facsafety*presafety)
534        tlimit = facsafety*presafety; 
535
536      //lower limit for tlimit
537      if(tlimit < tlimitmin) tlimit = tlimitmin;
538
539      if(tlimit > tgeom) tlimit = tgeom;
540
541      //  G4cout << "tgeom= " << tgeom << " geomlimit= " << geomlimit 
542      //     << " tlimit= " << tlimit << " presafety= " << presafety << G4endl;
543
544      // shortcut
545      if((tPathLength < tlimit) && (tPathLength < presafety) &&
546         (smallstep >= skin) && (tPathLength < geomlimit-0.999*skindepth))
547        return tPathLength;   
548
549      // step reduction near to boundary
550      if(smallstep < skin)
551        {
552          tlimit = stepmin;
553          insideskin = true;
554        }
555      else if(geomlimit < geombig)
556        {
557          if(geomlimit > skindepth)
558            {
559              if(tlimit > geomlimit-0.999*skindepth)
560                tlimit = geomlimit-0.999*skindepth;
561            }
562          else
563            {
564              insideskin = true;
565              if(tlimit > stepmin) tlimit = stepmin;
566            }
567        }
568
569      if(tlimit < stepmin) tlimit = stepmin;
570
571      if(tPathLength > tlimit) tPathLength = tlimit  ; 
572
573    }
574    // for 'normal' simulation with or without magnetic field
575    //  there no small step/single scattering at boundaries
576  else if(steppingAlgorithm == fUseSafety)
577    {
578      // compute presafety again if presafety <= 0 and no boundary
579      // i.e. when it is needed for optimization purposes
580      if((stepStatus != fGeomBoundary) && (presafety < tlimitminfix)) 
581        presafety = safetyHelper->ComputeSafety(sp->GetPosition()); 
582
583      // is far from boundary
584      if(currentRange < presafety)
585        {
586          inside = true;
587          return tPathLength; 
588        }
589
590      if((stepStatus == fGeomBoundary) || (stepStatus == fUndefined))
591      {
592        rangeinit = currentRange;
593        fr = facrange;
594        // 9.1 like stepping for e+/e- only (not for muons,hadrons)
595        if(mass < masslimite) 
596        {
597          if(lambda0 > currentRange)
598            rangeinit = lambda0;
599          if(lambda0 > lambdalimit)
600            fr *= 0.75+0.25*lambda0/lambdalimit;
601        }
602
603        //lower limit for tlimit
604        G4double rat = currentKinEnergy/MeV ;
605        rat = 1.e-3/(rat*(10.+rat)) ;
606        tlimitmin = 10.*lambda0*rat;
607        if(tlimitmin < tlimitminfix) tlimitmin = tlimitminfix;
608      }
609      //step limit
610      tlimit = fr*rangeinit;               
611
612      if(tlimit < facsafety*presafety)
613        tlimit = facsafety*presafety;
614
615      //lower limit for tlimit
616      if(tlimit < tlimitmin) tlimit = tlimitmin;
617
618      if(tPathLength > tlimit) tPathLength = tlimit;
619    }
620 
621  // version similar to 7.1 (needed for some experiments)
622  else
623    {
624      if (stepStatus == fGeomBoundary)
625        {
626          if (currentRange > lambda0) tlimit = facrange*currentRange;
627          else                        tlimit = facrange*lambda0;
628
629          if(tlimit < tlimitmin) tlimit = tlimitmin;
630          if(tPathLength > tlimit) tPathLength = tlimit;
631        }
632    }
633  // G4cout << "tPathLength= " << tPathLength << "  geomlimit= " << geomlimit
634  //     << " currentMinimalStep= " << currentMinimalStep << G4endl;
635  return tPathLength ;
636}
637
638//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
639
640void G4UrbanMscModel2::GeomLimit(const G4Track&  track)
641{
642  geomlimit = geombig;
643
644  // no geomlimit for the World volume
645  if((track.GetVolume() != 0) &&
646     (track.GetVolume() != safetyHelper->GetWorldVolume())) 
647  {
648    G4double cstep = currentRange;
649
650    geomlimit = safetyHelper->CheckNextStep(
651                  track.GetStep()->GetPreStepPoint()->GetPosition(),
652                  track.GetMomentumDirection(),
653                  cstep,
654                  presafety);
655    /*
656    G4cout << "!!!G4UrbanMscModel2::GeomLimit presafety= " << presafety
657           << " r= " << currentRange
658           << " limit= " << geomlimit << G4endl;
659    */
660  } 
661}
662
663//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
664
665G4double G4UrbanMscModel2::ComputeGeomPathLength(G4double)
666{
667  lambdaeff = lambda0;
668  par1 = -1. ; 
669  par2 = par3 = 0. ; 
670
671  //  do the true -> geom transformation
672  zPathLength = tPathLength;
673
674  // z = t for very small tPathLength
675  if(tPathLength < tlimitminfix) return zPathLength;
676
677  // this correction needed to run MSC with eIoni and eBrem inactivated
678  // and makes no harm for a normal run
679  if(tPathLength > currentRange)
680    tPathLength = currentRange ;
681
682  G4double tau   = tPathLength/lambda0 ;
683
684  if ((tau <= tausmall) || insideskin) {
685    zPathLength  = tPathLength;
686    if(zPathLength > lambda0) zPathLength = lambda0;
687    return zPathLength;
688  }
689
690  G4double zmean = tPathLength;
691  if (tPathLength < currentRange*dtrl) {
692    if(tau < taulim) zmean = tPathLength*(1.-0.5*tau) ;
693    else             zmean = lambda0*(1.-exp(-tau));
694  } else if(currentKinEnergy < mass)  {
695    par1 = 1./currentRange ;
696    par2 = 1./(par1*lambda0) ;
697    par3 = 1.+par2 ;
698    if(tPathLength < currentRange)
699      zmean = (1.-exp(par3*log(1.-tPathLength/currentRange)))/(par1*par3) ;
700    else
701      zmean = 1./(par1*par3) ;
702  } else {
703    G4double T1 = theManager->GetEnergy(particle,currentRange-tPathLength,couple);
704    G4double lambda1 = GetLambda(T1);
705
706    par1 = (lambda0-lambda1)/(lambda0*tPathLength) ;
707    par2 = 1./(par1*lambda0) ;
708    par3 = 1.+par2 ;
709    zmean = (1.-exp(par3*log(lambda1/lambda0)))/(par1*par3) ;
710  }
711
712  zPathLength = zmean ;
713
714  //  sample z
715  if(samplez)
716  {
717    const G4double  ztmax = 0.99 ;
718    G4double zt = zmean/tPathLength ;
719
720    if (tPathLength > stepmin && zt < ztmax)             
721    {
722      G4double u,cz1;
723      if(zt >= third)
724      {
725        G4double cz = 0.5*(3.*zt-1.)/(1.-zt) ;
726        cz1 = 1.+cz ;
727        G4double u0 = cz/cz1 ;
728        G4double grej ;
729        do {
730            u = exp(log(G4UniformRand())/cz1) ;
731            grej = exp(cz*log(u/u0))*(1.-u)/(1.-u0) ;
732           } while (grej < G4UniformRand()) ;
733      }
734      else
735      {
736        cz1 = 1./zt-1.;
737        u = 1.-exp(log(G4UniformRand())/cz1) ;
738      }
739      zPathLength = tPathLength*u ;
740    }
741  }
742
743  if(zPathLength > lambda0) zPathLength = lambda0;
744
745  return zPathLength;
746}
747
748//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
749
750G4double G4UrbanMscModel2::ComputeTrueStepLength(G4double geomStepLength)
751{
752  // step defined other than transportation
753  if(geomStepLength == zPathLength && tPathLength <= currentRange)
754    return tPathLength;
755
756  // t = z for very small step
757  zPathLength = geomStepLength;
758  tPathLength = geomStepLength;
759  if(geomStepLength < tlimitminfix) return tPathLength;
760 
761  // recalculation
762  if((geomStepLength > lambda0*tausmall) && !insideskin)
763  {
764    if(par1 <  0.)
765      tPathLength = -lambda0*log(1.-geomStepLength/lambda0) ;
766    else 
767    {
768      if(par1*par3*geomStepLength < 1.)
769        tPathLength = (1.-exp(log(1.-par1*par3*geomStepLength)/par3))/par1 ;
770      else 
771        tPathLength = currentRange;
772    } 
773  }
774  if(tPathLength < geomStepLength) tPathLength = geomStepLength;
775
776  return tPathLength;
777}
778
779//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
780
781G4double G4UrbanMscModel2::ComputeTheta0(G4double trueStepLength,
782                                        G4double KineticEnergy)
783{
784  // for all particles take the width of the central part
785  //  from a  parametrization similar to the Highland formula
786  // ( Highland formula: Particle Physics Booklet, July 2002, eq. 26.10)
787  const G4double c_highland = 13.6*MeV ;
788  G4double betacp = sqrt(currentKinEnergy*(currentKinEnergy+2.*mass)*
789                         KineticEnergy*(KineticEnergy+2.*mass)/
790                      ((currentKinEnergy+mass)*(KineticEnergy+mass)));
791  y = trueStepLength/currentRadLength;
792  G4double theta0 = c_highland*std::abs(charge)*sqrt(y)/betacp;
793  y = log(y);
794  // correction factor from e-/proton scattering data
795  G4double corr = coeffth1+coeffth2*y;               
796  if(y < -6.5) corr -= 0.011*(6.5+y);
797  theta0 *= corr ;                                               
798
799  return theta0;
800}
801
802//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
803
804void G4UrbanMscModel2::SampleScattering(const G4DynamicParticle* dynParticle,
805                                        G4double safety)
806{
807  G4double kineticEnergy = dynParticle->GetKineticEnergy();
808
809  if((kineticEnergy <= 0.0) || (tPathLength <= tlimitminfix) ||
810     (tPathLength/tausmall < lambda0)) return;
811
812  G4double cth  = SampleCosineTheta(tPathLength,kineticEnergy);
813
814  // protection against 'bad' cth values
815  if(std::abs(cth) > 1.) return;
816
817  G4double sth  = sqrt((1.0 - cth)*(1.0 + cth));
818  G4double phi  = twopi*G4UniformRand();
819  G4double dirx = sth*cos(phi);
820  G4double diry = sth*sin(phi);
821
822  G4ThreeVector oldDirection = dynParticle->GetMomentumDirection();
823  G4ThreeVector newDirection(dirx,diry,cth);
824  newDirection.rotateUz(oldDirection);
825  fParticleChange->ProposeMomentumDirection(newDirection);
826
827  if (latDisplasment && safety > tlimitminfix) {
828
829    G4double r = SampleDisplacement();
830    /*
831    G4cout << "G4UrbanMscModel2::SampleSecondaries: e(MeV)= " << kineticEnergy
832           << " sinTheta= " << sth << " r(mm)= " << r
833           << " trueStep(mm)= " << tPathLength
834           << " geomStep(mm)= " << zPathLength
835           << G4endl;
836    */
837    if(r > 0.)
838      {
839        G4double latcorr = LatCorrelation();
840        if(latcorr > r) latcorr = r;
841
842        // sample direction of lateral displacement
843        // compute it from the lateral correlation
844        G4double Phi = 0.;
845        if(std::abs(r*sth) < latcorr)
846          Phi  = twopi*G4UniformRand();
847        else
848        {
849          G4double psi = std::acos(latcorr/(r*sth));
850          if(G4UniformRand() < 0.5)
851            Phi = phi+psi;
852          else
853            Phi = phi-psi;
854        }
855
856        dirx = std::cos(Phi);
857        diry = std::sin(Phi);
858
859        G4ThreeVector latDirection(dirx,diry,0.0);
860        latDirection.rotateUz(oldDirection);
861
862        G4ThreeVector Position = *(fParticleChange->GetProposedPosition());
863        G4double fac = 1.;
864        if(r >  safety) {
865          //  ******* so safety is computed at boundary too ************
866          G4double newsafety = safetyHelper->ComputeSafety(Position);
867          if(r > newsafety)
868            fac = newsafety/r ;
869        } 
870
871        if(fac > 0.)
872        {
873          // compute new endpoint of the Step
874          G4ThreeVector newPosition = Position+fac*r*latDirection;
875
876          // definitely not on boundary
877          if(1. == fac) {
878            safetyHelper->ReLocateWithinVolume(newPosition);
879           
880          } else {
881            // check safety after displacement
882            G4double postsafety = safetyHelper->ComputeSafety(newPosition);
883
884            // displacement to boundary
885            if(postsafety <= 0.0) {
886              safetyHelper->Locate(newPosition, newDirection);
887
888            // not on the boundary
889            } else {
890              safetyHelper->ReLocateWithinVolume(newPosition);
891            }
892          }
893          fParticleChange->ProposePosition(newPosition);
894        } 
895     }
896  }
897}
898
899//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
900
901G4double G4UrbanMscModel2::SampleCosineTheta(G4double trueStepLength,
902                                             G4double KineticEnergy)
903{
904  G4double cth = 1. ;
905  G4double tau = trueStepLength/lambda0 ;
906
907  Zeff = couple->GetMaterial()->GetTotNbOfElectPerVolume()/
908         couple->GetMaterial()->GetTotNbOfAtomsPerVolume() ;
909
910  if(Zold != Zeff) 
911    UpdateCache();
912
913  if(insideskin)
914  {
915    //no scattering, single or plural scattering
916    G4double mean = trueStepLength/stepmin ;
917
918    G4int n = G4Poisson(mean);
919    if(n > 0)
920    {
921      //screening (Moliere-Bethe)
922      G4double mom2 = KineticEnergy*(2.*mass+KineticEnergy);
923      G4double beta2 = mom2/((KineticEnergy+mass)*(KineticEnergy+mass));
924      G4double ascr = scr1/mom2;
925      ascr *= 1.13+scr2/beta2;
926      G4double ascr1 = 1.+2.*ascr;
927      G4double bp1=ascr1+1.;
928      G4double bm1=ascr1-1.;
929
930      // single scattering from screened Rutherford x-section
931      G4double ct,st,phi;
932      G4double sx=0.,sy=0.,sz=0.;
933      for(G4int i=1; i<=n; i++)
934      {
935        ct = ascr1-bp1*bm1/(2.*G4UniformRand()+bm1);
936        if(ct < -1.) ct = -1.;
937        if(ct >  1.) ct =  1.; 
938        st = sqrt(1.-ct*ct);
939        phi = twopi*G4UniformRand();
940        sx += st*cos(phi);
941        sy += st*sin(phi);
942        sz += ct;
943      }
944      cth = sz/sqrt(sx*sx+sy*sy+sz*sz);
945    }
946  }
947  else
948  {
949    if(trueStepLength >= currentRange*dtrl) 
950    {
951      if(par1*trueStepLength < 1.)
952        tau = -par2*log(1.-par1*trueStepLength) ;
953      // for the case if ioni/brems are inactivated
954      // see the corresponding condition in ComputeGeomPathLength
955      else if(1.-KineticEnergy/currentKinEnergy > taulim)
956        tau = taubig ;
957    }
958    currentTau = tau ;
959    lambdaeff = trueStepLength/currentTau;
960    currentRadLength = couple->GetMaterial()->GetRadlen();
961
962    if (tau >= taubig) cth = -1.+2.*G4UniformRand();
963    else if (tau >= tausmall)
964    {
965      G4double xsi = 3.0; 
966      G4double x0 = 1.;
967      G4double a = 1., ea = 0., eaa = 1.;
968      G4double b=2.,b1=3.,bx=1.,eb1=3.,ebx=1.;
969      G4double prob = 1. , qprob = 1. ;
970      G4double xmean1 = 1., xmean2 = 0.;
971      G4double xmeanth = exp(-tau);
972      G4double x2meanth = (1.+2.*exp(-2.5*tau))/3.;
973
974      G4double relloss = 1.-KineticEnergy/currentKinEnergy;
975      if(relloss > rellossmax) 
976        return SimpleScattering(xmeanth,x2meanth);
977
978      G4double theta0 = ComputeTheta0(trueStepLength,KineticEnergy);
979
980      // protection for very small angles
981      if(theta0 < tausmall) return cth;
982   
983      if(theta0 > theta0max)
984        return SimpleScattering(xmeanth,x2meanth);
985      G4double sth = sin(0.5*theta0);
986      a = 0.25/(sth*sth);
987
988      ea = exp(-xsi);
989      eaa = 1.-ea ;
990      xmean1 = 1.-(1.-(1.+xsi)*ea)/(a*eaa);
991      x0 = 1.-xsi/a;
992
993      if(xmean1 <= 0.999*xmeanth)
994        return SimpleScattering(xmeanth,x2meanth);
995
996      // from MUSCAT H,Be,Fe data
997      G4double c = coeffc1;                         
998      if(y > -13.5) 
999        c += coeffc2*exp(3.*log(y+13.5));
1000
1001      if(abs(c-3.) < 0.001)  c = 3.001;     
1002      if(abs(c-2.) < 0.001)  c = 2.001;     
1003
1004      G4double c1 = c-1.;
1005
1006      //from continuity of derivatives
1007      b = 1.+(c-xsi)/a;
1008
1009      b1 = b+1.;
1010      bx = c/a;
1011      eb1 = exp(c1*log(b1));
1012      ebx = exp(c1*log(bx));
1013
1014      xmean2 = (x0*eb1+ebx-(eb1*bx-b1*ebx)/(c-2.))/(eb1-ebx);
1015     
1016      G4double f1x0 = a*ea/eaa;
1017      G4double f2x0 = c1*eb1/(bx*(eb1-ebx));
1018      prob = f2x0/(f1x0+f2x0);
1019
1020      qprob = xmeanth/(prob*xmean1+(1.-prob)*xmean2);
1021
1022      // sampling of costheta
1023      if(G4UniformRand() < qprob)
1024      {
1025        if(G4UniformRand() < prob)
1026          cth = 1.+log(ea+G4UniformRand()*eaa)/a ;
1027        else
1028          cth = b-b1*bx/exp(log(ebx+(eb1-ebx)*G4UniformRand())/c1) ;
1029      }
1030      else
1031        cth = -1.+2.*G4UniformRand();
1032    }
1033  } 
1034  return cth ;
1035}
1036
1037//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
1038
1039G4double G4UrbanMscModel2::SimpleScattering(G4double xmeanth,G4double x2meanth)
1040{
1041  // 'large angle scattering'
1042  // 2 model functions with correct xmean and x2mean
1043  G4double a = (2.*xmeanth+9.*x2meanth-3.)/(2.*xmeanth-3.*x2meanth+1.);
1044  G4double prob = (a+2.)*xmeanth/a;
1045
1046  // sampling
1047  G4double cth = 1.;
1048  if(G4UniformRand() < prob)
1049    cth = -1.+2.*exp(log(G4UniformRand())/(a+1.));
1050  else
1051    cth = -1.+2.*G4UniformRand();
1052  return cth;
1053}
1054
1055//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
1056
1057G4double G4UrbanMscModel2::SampleDisplacement()
1058{
1059  const G4double kappa = 2.5;
1060  const G4double kappapl1 = kappa+1.;
1061  const G4double kappami1 = kappa-1.;
1062  G4double rmean = 0.0;
1063  if ((currentTau >= tausmall) && !insideskin) {
1064    if (currentTau < taulim) {
1065      rmean = kappa*currentTau*currentTau*currentTau*
1066             (1.-kappapl1*currentTau*0.25)/6. ;
1067
1068    } else {
1069      G4double etau = 0.0;
1070      if (currentTau<taubig) etau = exp(-currentTau);
1071      rmean = -kappa*currentTau;
1072      rmean = -exp(rmean)/(kappa*kappami1);
1073      rmean += currentTau-kappapl1/kappa+kappa*etau/kappami1;
1074    }
1075    if (rmean>0.) rmean = 2.*lambdaeff*sqrt(rmean/3.0);
1076    else          rmean = 0.;
1077  }
1078
1079  // protection against z > t ...........................
1080  if(rmean > 0.) {
1081    G4double zt = (tPathLength-zPathLength)*(tPathLength+zPathLength);
1082    if(zt <= 0.)
1083      rmean = 0.;
1084    else if(rmean*rmean > zt)
1085      rmean = sqrt(zt);
1086  }
1087  return rmean;
1088}
1089
1090//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
1091
1092G4double G4UrbanMscModel2::LatCorrelation()
1093{
1094  const G4double kappa = 2.5;
1095  const G4double kappami1 = kappa-1.;
1096
1097  G4double latcorr = 0.;
1098  if((currentTau >= tausmall) && !insideskin)
1099  {
1100    if(currentTau < taulim)
1101      latcorr = lambdaeff*kappa*currentTau*currentTau*
1102                (1.-(kappa+1.)*currentTau/3.)/3.;
1103    else
1104    {
1105      G4double etau = 0.;
1106      if(currentTau < taubig) etau = exp(-currentTau);
1107      latcorr = -kappa*currentTau;
1108      latcorr = exp(latcorr)/kappami1;
1109      latcorr += 1.-kappa*etau/kappami1 ;
1110      latcorr *= 2.*lambdaeff/3. ;
1111    }
1112  }
1113
1114  return latcorr;
1115}
1116
1117//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
1118
1119void G4UrbanMscModel2::SampleSecondaries(std::vector<G4DynamicParticle*>*,
1120                                         const G4MaterialCutsCouple*,
1121                                         const G4DynamicParticle*,
1122                                         G4double,
1123                                         G4double)
1124{}
1125
1126//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
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