source: trunk/source/processes/electromagnetic/standard/src/G4UrbanMscModel2.cc @ 1228

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

update geant4.9.3 tag
File size: 35.3 KB
Line 
1//
2// ********************************************************************
3// * License and Disclaimer                                           *
4// *                                                                  *
5// * The  Geant4 software  is  copyright of the Copyright Holders  of *
6// * the Geant4 Collaboration.  It is provided  under  the terms  and *
7// * conditions of the Geant4 Software License,  included in the file *
8// * LICENSE and available at  http://cern.ch/geant4/license .  These *
9// * include a list of copyright holders.                             *
10// *                                                                  *
11// * Neither the authors of this software system, nor their employing *
12// * institutes,nor the agencies providing financial support for this *
13// * work  make  any representation or  warranty, express or implied, *
14// * regarding  this  software system or assume any liability for its *
15// * use.  Please see the license in the file  LICENSE  and URL above *
16// * for the full disclaimer and the limitation of liability.         *
17// *                                                                  *
18// * This  code  implementation is the result of  the  scientific and *
19// * technical work of the GEANT4 collaboration.                      *
20// * By using,  copying,  modifying or  distributing the software (or *
21// * any work based  on the software)  you  agree  to acknowledge its *
22// * use  in  resulting  scientific  publications,  and indicate your *
23// * acceptance of all terms of the Geant4 Software license.          *
24// ********************************************************************
25//
26//
27// $Id: G4UrbanMscModel2.cc,v 1.27 2009/07/20 18:41:34 vnivanch Exp $
28// GEANT4 tag $Name: geant4-09-03 $
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
107#include "G4Poisson.hh"
108#include "globals.hh"
109
110//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
111
112using namespace std;
113
114G4UrbanMscModel2::G4UrbanMscModel2(const G4String& nam)
115  : G4VMscModel(nam),
116    isInitialized(false)
117{
118  masslimite    = 0.6*MeV;
119  lambdalimit   = 1.*mm;
120  fr            = 0.02;
121  //facsafety     = 0.3;
122  taubig        = 8.0;
123  tausmall      = 1.e-16;
124  taulim        = 1.e-6;
125  currentTau    = taulim;
126  tlimitminfix  = 1.e-6*mm;           
127  stepmin       = tlimitminfix;
128  smallstep     = 1.e10;
129  currentRange  = 0. ;
130  rangeinit     = 0.;
131  tlimit        = 1.e10*mm;
132  tlimitmin     = 10.*tlimitminfix;           
133  tgeom         = 1.e50*mm;
134  geombig       = 1.e50*mm;
135  geommin       = 1.e-3*mm;
136  geomlimit     = geombig;
137  presafety     = 0.*mm;
138                         
139  y             = 0.;
140
141  Zold          = 0.;
142  Zeff          = 1.;
143  Z2            = 1.;               
144  Z23           = 1.;                   
145  lnZ           = 0.;
146  coeffth1      = 0.;
147  coeffth2      = 0.;
148  coeffc1       = 0.;
149  coeffc2       = 0.;
150  scr1ini       = fine_structure_const*fine_structure_const*
151                  electron_mass_c2*electron_mass_c2/(0.885*0.885*4.*pi);
152  scr2ini       = 3.76*fine_structure_const*fine_structure_const;
153  scr1          = 0.;
154  scr2          = 0.;
155
156  theta0max     = pi/6.;
157  rellossmax    = 0.50;
158  third         = 1./3.;
159  particle      = 0;
160  theManager    = G4LossTableManager::Instance(); 
161  inside        = false; 
162  insideskin    = false;
163
164}
165
166//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
167
168G4UrbanMscModel2::~G4UrbanMscModel2()
169{}
170
171//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
172
173void G4UrbanMscModel2::Initialise(const G4ParticleDefinition* p,
174                                  const G4DataVector&)
175{
176  skindepth = skin*stepmin;
177  if(isInitialized) return;
178  // set values of some data members
179  SetParticle(p);
180
181  fParticleChange = GetParticleChangeForMSC();
182  InitialiseSafetyHelper();
183
184  isInitialized = true;
185}
186
187//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
188
189G4double G4UrbanMscModel2::ComputeCrossSectionPerAtom( 
190                             const G4ParticleDefinition* part,
191                                   G4double KineticEnergy,
192                                   G4double AtomicNumber,G4double,
193                                   G4double, G4double)
194{
195  const G4double sigmafactor = twopi*classic_electr_radius*classic_electr_radius;
196  const G4double epsfactor = 2.*electron_mass_c2*electron_mass_c2*
197                            Bohr_radius*Bohr_radius/(hbarc*hbarc);
198  const G4double epsmin = 1.e-4 , epsmax = 1.e10;
199
200  const G4double Zdat[15] = { 4.,  6., 13., 20., 26., 29., 32., 38., 47.,
201                             50., 56., 64., 74., 79., 82. };
202
203  const G4double Tdat[22] = { 100*eV,  200*eV,  400*eV,  700*eV,
204                               1*keV,   2*keV,   4*keV,   7*keV,
205                              10*keV,  20*keV,  40*keV,  70*keV,
206                             100*keV, 200*keV, 400*keV, 700*keV,
207                               1*MeV,   2*MeV,   4*MeV,   7*MeV,
208                              10*MeV,  20*MeV};
209
210  // corr. factors for e-/e+ lambda for T <= Tlim
211          G4double celectron[15][22] =
212          {{1.125,1.072,1.051,1.047,1.047,1.050,1.052,1.054,
213            1.054,1.057,1.062,1.069,1.075,1.090,1.105,1.111,
214            1.112,1.108,1.100,1.093,1.089,1.087            },
215           {1.408,1.246,1.143,1.096,1.077,1.059,1.053,1.051,
216            1.052,1.053,1.058,1.065,1.072,1.087,1.101,1.108,
217            1.109,1.105,1.097,1.090,1.086,1.082            },
218           {2.833,2.268,1.861,1.612,1.486,1.309,1.204,1.156,
219            1.136,1.114,1.106,1.106,1.109,1.119,1.129,1.132,
220            1.131,1.124,1.113,1.104,1.099,1.098            },
221           {3.879,3.016,2.380,2.007,1.818,1.535,1.340,1.236,
222            1.190,1.133,1.107,1.099,1.098,1.103,1.110,1.113,
223            1.112,1.105,1.096,1.089,1.085,1.098            },
224           {6.937,4.330,2.886,2.256,1.987,1.628,1.395,1.265,
225            1.203,1.122,1.080,1.065,1.061,1.063,1.070,1.073,
226            1.073,1.070,1.064,1.059,1.056,1.056            },
227           {9.616,5.708,3.424,2.551,2.204,1.762,1.485,1.330,
228            1.256,1.155,1.099,1.077,1.070,1.068,1.072,1.074,
229            1.074,1.070,1.063,1.059,1.056,1.052            },
230           {11.72,6.364,3.811,2.806,2.401,1.884,1.564,1.386,
231            1.300,1.180,1.112,1.082,1.073,1.066,1.068,1.069,
232            1.068,1.064,1.059,1.054,1.051,1.050            },
233           {18.08,8.601,4.569,3.183,2.662,2.025,1.646,1.439,
234            1.339,1.195,1.108,1.068,1.053,1.040,1.039,1.039,
235            1.039,1.037,1.034,1.031,1.030,1.036            },
236           {18.22,10.48,5.333,3.713,3.115,2.367,1.898,1.631,
237            1.498,1.301,1.171,1.105,1.077,1.048,1.036,1.033,
238            1.031,1.028,1.024,1.022,1.021,1.024            },
239           {14.14,10.65,5.710,3.929,3.266,2.453,1.951,1.669,
240            1.528,1.319,1.178,1.106,1.075,1.040,1.027,1.022,
241            1.020,1.017,1.015,1.013,1.013,1.020            },
242           {14.11,11.73,6.312,4.240,3.478,2.566,2.022,1.720,
243            1.569,1.342,1.186,1.102,1.065,1.022,1.003,0.997,
244            0.995,0.993,0.993,0.993,0.993,1.011            },
245           {22.76,20.01,8.835,5.287,4.144,2.901,2.219,1.855,
246            1.677,1.410,1.224,1.121,1.073,1.014,0.986,0.976,
247            0.974,0.972,0.973,0.974,0.975,0.987            },
248           {50.77,40.85,14.13,7.184,5.284,3.435,2.520,2.059,
249            1.837,1.512,1.283,1.153,1.091,1.010,0.969,0.954,
250            0.950,0.947,0.949,0.952,0.954,0.963            },
251           {65.87,59.06,15.87,7.570,5.567,3.650,2.682,2.182,
252            1.939,1.579,1.325,1.178,1.108,1.014,0.965,0.947,
253            0.941,0.938,0.940,0.944,0.946,0.954            },
254           {55.60,47.34,15.92,7.810,5.755,3.767,2.760,2.239,
255            1.985,1.609,1.343,1.188,1.113,1.013,0.960,0.939,
256            0.933,0.930,0.933,0.936,0.939,0.949            }};
257           
258           G4double cpositron[15][22] = {
259           {2.589,2.044,1.658,1.446,1.347,1.217,1.144,1.110,
260            1.097,1.083,1.080,1.086,1.092,1.108,1.123,1.131,
261            1.131,1.126,1.117,1.108,1.103,1.100            },
262           {3.904,2.794,2.079,1.710,1.543,1.325,1.202,1.145,
263            1.122,1.096,1.089,1.092,1.098,1.114,1.130,1.137,
264            1.138,1.132,1.122,1.113,1.108,1.102            },
265           {7.970,6.080,4.442,3.398,2.872,2.127,1.672,1.451,
266            1.357,1.246,1.194,1.179,1.178,1.188,1.201,1.205,
267            1.203,1.190,1.173,1.159,1.151,1.145            },
268           {9.714,7.607,5.747,4.493,3.815,2.777,2.079,1.715,
269            1.553,1.353,1.253,1.219,1.211,1.214,1.225,1.228,
270            1.225,1.210,1.191,1.175,1.166,1.174            },
271           {17.97,12.95,8.628,6.065,4.849,3.222,2.275,1.820,
272            1.624,1.382,1.259,1.214,1.202,1.202,1.214,1.219,
273            1.217,1.203,1.184,1.169,1.160,1.151            },
274           {24.83,17.06,10.84,7.355,5.767,3.707,2.546,1.996,
275            1.759,1.465,1.311,1.252,1.234,1.228,1.238,1.241,
276            1.237,1.222,1.201,1.184,1.174,1.159            },
277           {23.26,17.15,11.52,8.049,6.375,4.114,2.792,2.155,
278            1.880,1.535,1.353,1.281,1.258,1.247,1.254,1.256,
279            1.252,1.234,1.212,1.194,1.183,1.170            },
280           {22.33,18.01,12.86,9.212,7.336,4.702,3.117,2.348,
281            2.015,1.602,1.385,1.297,1.268,1.251,1.256,1.258,
282            1.254,1.237,1.214,1.195,1.185,1.179            },
283           {33.91,24.13,15.71,10.80,8.507,5.467,3.692,2.808,
284            2.407,1.873,1.564,1.425,1.374,1.330,1.324,1.320,
285            1.312,1.288,1.258,1.235,1.221,1.205            },
286           {32.14,24.11,16.30,11.40,9.015,5.782,3.868,2.917,
287            2.490,1.925,1.596,1.447,1.391,1.342,1.332,1.327,
288            1.320,1.294,1.264,1.240,1.226,1.214            },
289           {29.51,24.07,17.19,12.28,9.766,6.238,4.112,3.066,
290            2.602,1.995,1.641,1.477,1.414,1.356,1.342,1.336,
291            1.328,1.302,1.270,1.245,1.231,1.233            },
292           {38.19,30.85,21.76,15.35,12.07,7.521,4.812,3.498,
293            2.926,2.188,1.763,1.563,1.484,1.405,1.382,1.371,
294            1.361,1.330,1.294,1.267,1.251,1.239            },
295           {49.71,39.80,27.96,19.63,15.36,9.407,5.863,4.155,
296            3.417,2.478,1.944,1.692,1.589,1.480,1.441,1.423,
297            1.409,1.372,1.330,1.298,1.280,1.258            },
298           {59.25,45.08,30.36,20.83,16.15,9.834,6.166,4.407,
299            3.641,2.648,2.064,1.779,1.661,1.531,1.482,1.459,
300            1.442,1.400,1.354,1.319,1.299,1.272            },
301           {56.38,44.29,30.50,21.18,16.51,10.11,6.354,4.542,
302            3.752,2.724,2.116,1.817,1.692,1.554,1.499,1.474,
303            1.456,1.412,1.364,1.328,1.307,1.282            }};
304
305  //data/corrections for T > Tlim 
306  G4double Tlim = 10.*MeV;
307  G4double beta2lim = Tlim*(Tlim+2.*electron_mass_c2)/
308                      ((Tlim+electron_mass_c2)*(Tlim+electron_mass_c2));
309  G4double bg2lim   = Tlim*(Tlim+2.*electron_mass_c2)/
310                      (electron_mass_c2*electron_mass_c2);
311
312  G4double sig0[15] = {0.2672*barn,  0.5922*barn, 2.653*barn,  6.235*barn,
313                      11.69*barn  , 13.24*barn  , 16.12*barn, 23.00*barn ,
314                      35.13*barn  , 39.95*barn  , 50.85*barn, 67.19*barn ,
315                      91.15*barn  , 104.4*barn  , 113.1*barn};
316                                       
317  G4double hecorr[15] = {120.70, 117.50, 105.00, 92.92, 79.23,  74.510,  68.29,
318                          57.39,  41.97,  36.14, 24.53, 10.21,  -7.855, -16.84,
319                         -22.30};
320
321  G4double sigma;
322  SetParticle(part);
323
324  G4double Z23 = 2.*log(AtomicNumber)/3.; Z23 = exp(Z23);
325
326  // correction if particle .ne. e-/e+
327  // compute equivalent kinetic energy
328  // lambda depends on p*beta ....
329
330  G4double eKineticEnergy = KineticEnergy;
331
332  if(mass > electron_mass_c2)
333  {
334     G4double TAU = KineticEnergy/mass ;
335     G4double c = mass*TAU*(TAU+2.)/(electron_mass_c2*(TAU+1.)) ;
336     G4double w = c-2. ;
337     G4double tau = 0.5*(w+sqrt(w*w+4.*c)) ;
338     eKineticEnergy = electron_mass_c2*tau ;
339  }
340
341  G4double eTotalEnergy = eKineticEnergy + electron_mass_c2 ;
342  G4double beta2 = eKineticEnergy*(eTotalEnergy+electron_mass_c2)
343                                 /(eTotalEnergy*eTotalEnergy);
344  G4double bg2   = eKineticEnergy*(eTotalEnergy+electron_mass_c2)
345                                 /(electron_mass_c2*electron_mass_c2);
346
347  G4double eps = epsfactor*bg2/Z23;
348
349  if     (eps<epsmin)  sigma = 2.*eps*eps;
350  else if(eps<epsmax)  sigma = log(1.+2.*eps)-2.*eps/(1.+2.*eps);
351  else                 sigma = log(2.*eps)-1.+1./eps;
352
353  sigma *= ChargeSquare*AtomicNumber*AtomicNumber/(beta2*bg2);
354
355  // interpolate in AtomicNumber and beta2
356  G4double c1,c2,cc1,cc2,corr;
357
358  // get bin number in Z
359  G4int iZ = 14;
360  while ((iZ>=0)&&(Zdat[iZ]>=AtomicNumber)) iZ -= 1;
361  if (iZ==14)                               iZ = 13;
362  if (iZ==-1)                               iZ = 0 ;
363
364  G4double Z1 = Zdat[iZ];
365  G4double Z2 = Zdat[iZ+1];
366  G4double ratZ = (AtomicNumber-Z1)*(AtomicNumber+Z1)/
367                  ((Z2-Z1)*(Z2+Z1));
368
369  if(eKineticEnergy <= Tlim) 
370  {
371    // get bin number in T (beta2)
372    G4int iT = 21;
373    while ((iT>=0)&&(Tdat[iT]>=eKineticEnergy)) iT -= 1;
374    if(iT==21)                                  iT = 20;
375    if(iT==-1)                                  iT = 0 ;
376
377    //  calculate betasquare values
378    G4double T = Tdat[iT],   E = T + electron_mass_c2;
379    G4double b2small = T*(E+electron_mass_c2)/(E*E);
380
381    T = Tdat[iT+1]; E = T + electron_mass_c2;
382    G4double b2big = T*(E+electron_mass_c2)/(E*E);
383    G4double ratb2 = (beta2-b2small)/(b2big-b2small);
384
385    if (charge < 0.)
386    {
387       c1 = celectron[iZ][iT];
388       c2 = celectron[iZ+1][iT];
389       cc1 = c1+ratZ*(c2-c1);
390
391       c1 = celectron[iZ][iT+1];
392       c2 = celectron[iZ+1][iT+1];
393       cc2 = c1+ratZ*(c2-c1);
394
395       corr = cc1+ratb2*(cc2-cc1);
396
397       sigma *= sigmafactor/corr;
398    }
399    else             
400    {
401       c1 = cpositron[iZ][iT];
402       c2 = cpositron[iZ+1][iT];
403       cc1 = c1+ratZ*(c2-c1);
404
405       c1 = cpositron[iZ][iT+1];
406       c2 = cpositron[iZ+1][iT+1];
407       cc2 = c1+ratZ*(c2-c1);
408
409       corr = cc1+ratb2*(cc2-cc1);
410
411       sigma *= sigmafactor/corr;
412    }
413  }
414  else
415  {
416    c1 = bg2lim*sig0[iZ]*(1.+hecorr[iZ]*(beta2-beta2lim))/bg2;
417    c2 = bg2lim*sig0[iZ+1]*(1.+hecorr[iZ+1]*(beta2-beta2lim))/bg2;
418    if((AtomicNumber >= Z1) && (AtomicNumber <= Z2))
419      sigma = c1+ratZ*(c2-c1) ;
420    else if(AtomicNumber < Z1)
421      sigma = AtomicNumber*AtomicNumber*c1/(Z1*Z1);
422    else if(AtomicNumber > Z2)
423      sigma = AtomicNumber*AtomicNumber*c2/(Z2*Z2);
424  }
425  return sigma;
426
427}
428
429//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
430
431G4double G4UrbanMscModel2::ComputeTruePathLengthLimit(
432                             const G4Track& track,
433                             G4PhysicsTable* theTable,
434                             G4double currentMinimalStep)
435{
436  tPathLength = currentMinimalStep;
437  G4StepPoint* sp = track.GetStep()->GetPreStepPoint();
438  G4StepStatus stepStatus = sp->GetStepStatus();
439
440  const G4DynamicParticle* dp = track.GetDynamicParticle();
441
442  if(stepStatus == fUndefined) {
443    inside = false;
444    insideskin = false;
445    tlimit = geombig;
446    SetParticle( dp->GetDefinition() );
447  }
448
449  theLambdaTable = theTable;
450  couple = track.GetMaterialCutsCouple();
451  currentMaterialIndex = couple->GetIndex();
452  currentKinEnergy = dp->GetKineticEnergy();
453  currentRange = 
454    theManager->GetRangeFromRestricteDEDX(particle,currentKinEnergy,couple);
455  lambda0 = GetLambda(currentKinEnergy);
456
457  // stop here if small range particle
458  if(inside) return tPathLength;           
459 
460  if(tPathLength > currentRange) tPathLength = currentRange;
461
462  presafety = sp->GetSafety();
463
464  //G4cout << "G4Urban2::StepLimit tPathLength= "
465  //     <<tPathLength<<" safety= " << presafety
466  //       << " range= " <<currentRange<< " lambda= "<<lambda0
467  //     << " Alg: " << steppingAlgorithm <<G4endl;
468
469  // far from geometry boundary
470  if(currentRange < presafety)
471    {
472      inside = true;
473      return tPathLength; 
474    }
475
476  // standard  version
477  //
478  if (steppingAlgorithm == fUseDistanceToBoundary)
479    {
480      //compute geomlimit and presafety
481      G4double geomlimit = ComputeGeomLimit(track, presafety, currentRange);
482
483      // is it far from boundary ?
484      if(currentRange < presafety)
485        {
486          inside = true;
487          return tPathLength;   
488        }
489
490      smallstep += 1.;
491      insideskin = false;
492
493      if((stepStatus == fGeomBoundary) || (stepStatus == fUndefined))
494        {
495          rangeinit = currentRange;
496          if(stepStatus == fUndefined) smallstep = 1.e10;
497          else  smallstep = 1.;
498
499          //define stepmin here (it depends on lambda!)
500          //rough estimation of lambda_elastic/lambda_transport
501          G4double rat = currentKinEnergy/MeV ;
502          rat = 1.e-3/(rat*(10.+rat)) ;
503          //stepmin ~ lambda_elastic
504          stepmin = rat*lambda0;
505          skindepth = skin*stepmin;
506          //define tlimitmin
507          tlimitmin = 10.*stepmin;
508          if(tlimitmin < tlimitminfix) tlimitmin = tlimitminfix;
509          //G4cout << "rangeinit= " << rangeinit << " stepmin= " << stepmin
510          //     << " tlimitmin= " << tlimitmin << " geomlimit= " << geomlimit <<G4endl;
511          // constraint from the geometry
512          if((geomlimit < geombig) && (geomlimit > geommin))
513            {
514              // geomlimit is a geometrical step length
515              // transform it to true path length (estimation)
516              if((1.-geomlimit/lambda0) > 0.)
517                geomlimit = -lambda0*log(1.-geomlimit/lambda0)+tlimitmin ;
518
519              if(stepStatus == fGeomBoundary)
520                tgeom = geomlimit/facgeom;
521              else
522                tgeom = 2.*geomlimit/facgeom;
523            }
524            else
525              tgeom = geombig;
526        }
527
528
529      //step limit
530      tlimit = facrange*rangeinit;             
531      if(tlimit < facsafety*presafety)
532        tlimit = facsafety*presafety; 
533
534      //lower limit for tlimit
535      if(tlimit < tlimitmin) tlimit = tlimitmin;
536
537      if(tlimit > tgeom) tlimit = tgeom;
538
539      //G4cout << "tgeom= " << tgeom << " geomlimit= " << geomlimit 
540      //      << " tlimit= " << tlimit << " presafety= " << presafety << G4endl;
541
542      // shortcut
543      if((tPathLength < tlimit) && (tPathLength < presafety) &&
544         (smallstep >= skin) && (tPathLength < geomlimit-0.999*skindepth))
545        return tPathLength;   
546
547      // step reduction near to boundary
548      if(smallstep < skin)
549        {
550          tlimit = stepmin;
551          insideskin = true;
552        }
553      else if(geomlimit < geombig)
554        {
555          if(geomlimit > skindepth)
556            {
557              if(tlimit > geomlimit-0.999*skindepth)
558                tlimit = geomlimit-0.999*skindepth;
559            }
560          else
561            {
562              insideskin = true;
563              if(tlimit > stepmin) tlimit = stepmin;
564            }
565        }
566
567      if(tlimit < stepmin) tlimit = stepmin;
568
569      if(tPathLength > tlimit) tPathLength = tlimit  ; 
570
571    }
572    // for 'normal' simulation with or without magnetic field
573    //  there no small step/single scattering at boundaries
574  else if(steppingAlgorithm == fUseSafety)
575    {
576      // compute presafety again if presafety <= 0 and no boundary
577      // i.e. when it is needed for optimization purposes
578      if((stepStatus != fGeomBoundary) && (presafety < tlimitminfix)) 
579        presafety = ComputeSafety(sp->GetPosition(),tPathLength); 
580
581      // is far from boundary
582      if(currentRange < presafety)
583        {
584          inside = true;
585          return tPathLength; 
586        }
587
588      if((stepStatus == fGeomBoundary) || (stepStatus == fUndefined))
589      {
590        rangeinit = currentRange;
591        fr = facrange;
592        // 9.1 like stepping for e+/e- only (not for muons,hadrons)
593        if(mass < masslimite) 
594        {
595          if(lambda0 > currentRange)
596            rangeinit = lambda0;
597          if(lambda0 > lambdalimit)
598            fr *= 0.75+0.25*lambda0/lambdalimit;
599        }
600
601        //lower limit for tlimit
602        G4double rat = currentKinEnergy/MeV ;
603        rat = 1.e-3/(rat*(10.+rat)) ;
604        tlimitmin = 10.*lambda0*rat;
605        if(tlimitmin < tlimitminfix) tlimitmin = tlimitminfix;
606      }
607      //step limit
608      tlimit = fr*rangeinit;               
609
610      if(tlimit < facsafety*presafety)
611        tlimit = facsafety*presafety;
612
613      //lower limit for tlimit
614      if(tlimit < tlimitmin) tlimit = tlimitmin;
615
616      if(tPathLength > tlimit) tPathLength = tlimit;
617    }
618 
619  // version similar to 7.1 (needed for some experiments)
620  else
621    {
622      if (stepStatus == fGeomBoundary)
623        {
624          if (currentRange > lambda0) tlimit = facrange*currentRange;
625          else                        tlimit = facrange*lambda0;
626
627          if(tlimit < tlimitmin) tlimit = tlimitmin;
628          if(tPathLength > tlimit) tPathLength = tlimit;
629        }
630    }
631  //G4cout << "tPathLength= " << tPathLength
632  //     << " currentMinimalStep= " << currentMinimalStep << G4endl;
633  return tPathLength ;
634}
635
636//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
637
638G4double G4UrbanMscModel2::ComputeGeomPathLength(G4double)
639{
640  lambdaeff = lambda0;
641  par1 = -1. ; 
642  par2 = par3 = 0. ; 
643
644  //  do the true -> geom transformation
645  zPathLength = tPathLength;
646
647  // z = t for very small tPathLength
648  if(tPathLength < tlimitminfix) return zPathLength;
649
650  // this correction needed to run MSC with eIoni and eBrem inactivated
651  // and makes no harm for a normal run
652  if(tPathLength > currentRange)
653    tPathLength = currentRange ;
654
655  G4double tau   = tPathLength/lambda0 ;
656
657  if ((tau <= tausmall) || insideskin) {
658    zPathLength  = tPathLength;
659    if(zPathLength > lambda0) zPathLength = lambda0;
660    return zPathLength;
661  }
662
663  G4double zmean = tPathLength;
664  if (tPathLength < currentRange*dtrl) {
665    if(tau < taulim) zmean = tPathLength*(1.-0.5*tau) ;
666    else             zmean = lambda0*(1.-exp(-tau));
667  } else if(currentKinEnergy < mass)  {
668    par1 = 1./currentRange ;
669    par2 = 1./(par1*lambda0) ;
670    par3 = 1.+par2 ;
671    if(tPathLength < currentRange)
672      zmean = (1.-exp(par3*log(1.-tPathLength/currentRange)))/(par1*par3) ;
673    else
674      zmean = 1./(par1*par3) ;
675  } else {
676    G4double T1 = theManager->GetEnergy(particle,currentRange-tPathLength,couple);
677    G4double lambda1 = GetLambda(T1);
678
679    par1 = (lambda0-lambda1)/(lambda0*tPathLength) ;
680    par2 = 1./(par1*lambda0) ;
681    par3 = 1.+par2 ;
682    zmean = (1.-exp(par3*log(lambda1/lambda0)))/(par1*par3) ;
683  }
684
685  zPathLength = zmean ;
686
687  //  sample z
688  if(samplez)
689  {
690    const G4double  ztmax = 0.99 ;
691    G4double zt = zmean/tPathLength ;
692
693    if (tPathLength > stepmin && zt < ztmax)             
694    {
695      G4double u,cz1;
696      if(zt >= third)
697      {
698        G4double cz = 0.5*(3.*zt-1.)/(1.-zt) ;
699        cz1 = 1.+cz ;
700        G4double u0 = cz/cz1 ;
701        G4double grej ;
702        do {
703            u = exp(log(G4UniformRand())/cz1) ;
704            grej = exp(cz*log(u/u0))*(1.-u)/(1.-u0) ;
705           } while (grej < G4UniformRand()) ;
706      }
707      else
708      {
709        cz1 = 1./zt-1.;
710        u = 1.-exp(log(G4UniformRand())/cz1) ;
711      }
712      zPathLength = tPathLength*u ;
713    }
714  }
715
716  if(zPathLength > lambda0) zPathLength = lambda0;
717  //G4cout << "zPathLength= " << zPathLength << " lambda1= " << lambda0 << G4endl;
718  return zPathLength;
719}
720
721//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
722
723G4double G4UrbanMscModel2::ComputeTrueStepLength(G4double geomStepLength)
724{
725  // step defined other than transportation
726  if(geomStepLength == zPathLength && tPathLength <= currentRange)
727    return tPathLength;
728
729  // t = z for very small step
730  zPathLength = geomStepLength;
731  tPathLength = geomStepLength;
732  if(geomStepLength < tlimitminfix) return tPathLength;
733 
734  // recalculation
735  if((geomStepLength > lambda0*tausmall) && !insideskin)
736  {
737    if(par1 <  0.)
738      tPathLength = -lambda0*log(1.-geomStepLength/lambda0) ;
739    else 
740    {
741      if(par1*par3*geomStepLength < 1.)
742        tPathLength = (1.-exp(log(1.-par1*par3*geomStepLength)/par3))/par1 ;
743      else 
744        tPathLength = currentRange;
745    } 
746  }
747  if(tPathLength < geomStepLength) tPathLength = geomStepLength;
748  //G4cout << "tPathLength= " << tPathLength << " step= " << geomStepLength << G4endl;
749
750  return tPathLength;
751}
752
753//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
754
755G4double G4UrbanMscModel2::ComputeTheta0(G4double trueStepLength,
756                                        G4double KineticEnergy)
757{
758  // for all particles take the width of the central part
759  //  from a  parametrization similar to the Highland formula
760  // ( Highland formula: Particle Physics Booklet, July 2002, eq. 26.10)
761  const G4double c_highland = 13.6*MeV ;
762  G4double betacp = sqrt(currentKinEnergy*(currentKinEnergy+2.*mass)*
763                         KineticEnergy*(KineticEnergy+2.*mass)/
764                      ((currentKinEnergy+mass)*(KineticEnergy+mass)));
765  y = trueStepLength/currentRadLength;
766  G4double theta0 = c_highland*std::abs(charge)*sqrt(y)/betacp;
767  y = log(y);
768  // correction factor from e- scattering data
769  G4double corr = coeffth1+coeffth2*y;               
770
771  theta0 *= corr ;                                               
772
773  return theta0;
774}
775
776//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
777
778void G4UrbanMscModel2::SampleScattering(const G4DynamicParticle* dynParticle,
779                                        G4double safety)
780{
781  G4double kineticEnergy = dynParticle->GetKineticEnergy();
782
783  if((kineticEnergy <= 0.0) || (tPathLength <= tlimitminfix) ||
784     (tPathLength/tausmall < lambda0)) return;
785
786  G4double cth  = SampleCosineTheta(tPathLength,kineticEnergy);
787
788  // protection against 'bad' cth values
789  if(std::abs(cth) > 1.) return;
790
791  G4double sth  = sqrt((1.0 - cth)*(1.0 + cth));
792  G4double phi  = twopi*G4UniformRand();
793  G4double dirx = sth*cos(phi);
794  G4double diry = sth*sin(phi);
795
796  G4ThreeVector oldDirection = dynParticle->GetMomentumDirection();
797  G4ThreeVector newDirection(dirx,diry,cth);
798  newDirection.rotateUz(oldDirection);
799  fParticleChange->ProposeMomentumDirection(newDirection);
800
801  if (latDisplasment && safety > tlimitminfix) {
802
803    G4double r = SampleDisplacement();
804    /*   
805    G4cout << "G4UrbanMscModel2::SampleSecondaries: e(MeV)= " << kineticEnergy
806           << " sinTheta= " << sth << " r(mm)= " << r
807           << " trueStep(mm)= " << tPathLength
808           << " geomStep(mm)= " << zPathLength
809           << G4endl;
810    */
811    if(r > 0.)
812      {
813        G4double latcorr = LatCorrelation();
814        if(latcorr > r) latcorr = r;
815
816        // sample direction of lateral displacement
817        // compute it from the lateral correlation
818        G4double Phi = 0.;
819        if(std::abs(r*sth) < latcorr)
820          Phi  = twopi*G4UniformRand();
821        else
822        {
823          G4double psi = std::acos(latcorr/(r*sth));
824          if(G4UniformRand() < 0.5)
825            Phi = phi+psi;
826          else
827            Phi = phi-psi;
828        }
829
830        dirx = std::cos(Phi);
831        diry = std::sin(Phi);
832
833        G4ThreeVector latDirection(dirx,diry,0.0);
834        latDirection.rotateUz(oldDirection);
835
836        ComputeDisplacement(fParticleChange, latDirection, r, safety);
837      }
838  }
839}
840
841//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
842
843G4double G4UrbanMscModel2::SampleCosineTheta(G4double trueStepLength,
844                                             G4double KineticEnergy)
845{
846  G4double cth = 1. ;
847  G4double tau = trueStepLength/lambda0 ;
848
849  Zeff = couple->GetMaterial()->GetTotNbOfElectPerVolume()/
850         couple->GetMaterial()->GetTotNbOfAtomsPerVolume() ;
851
852  if(Zold != Zeff) 
853    UpdateCache();
854
855  if(insideskin)
856  {
857    //no scattering, single or plural scattering
858    G4double mean = trueStepLength/stepmin ;
859
860    G4int n = G4Poisson(mean);
861    if(n > 0)
862    {
863      //screening (Moliere-Bethe)
864      G4double mom2 = KineticEnergy*(2.*mass+KineticEnergy);
865      G4double beta2 = mom2/((KineticEnergy+mass)*(KineticEnergy+mass));
866      G4double ascr = scr1/mom2;
867      ascr *= 1.13+scr2/beta2;
868      G4double ascr1 = 1.+2.*ascr;
869      G4double bp1=ascr1+1.;
870      G4double bm1=ascr1-1.;
871
872      // single scattering from screened Rutherford x-section
873      G4double ct,st,phi;
874      G4double sx=0.,sy=0.,sz=0.;
875      for(G4int i=1; i<=n; i++)
876      {
877        ct = ascr1-bp1*bm1/(2.*G4UniformRand()+bm1);
878        if(ct < -1.) ct = -1.;
879        if(ct >  1.) ct =  1.; 
880        st = sqrt(1.-ct*ct);
881        phi = twopi*G4UniformRand();
882        sx += st*cos(phi);
883        sy += st*sin(phi);
884        sz += ct;
885      }
886      cth = sz/sqrt(sx*sx+sy*sy+sz*sz);
887    }
888  }
889  else
890  {
891    if(trueStepLength >= currentRange*dtrl) 
892    {
893      if(par1*trueStepLength < 1.)
894        tau = -par2*log(1.-par1*trueStepLength) ;
895      // for the case if ioni/brems are inactivated
896      // see the corresponding condition in ComputeGeomPathLength
897      else if(1.-KineticEnergy/currentKinEnergy > taulim)
898        tau = taubig ;
899    }
900    currentTau = tau ;
901    lambdaeff = trueStepLength/currentTau;
902    currentRadLength = couple->GetMaterial()->GetRadlen();
903
904    if (tau >= taubig) cth = -1.+2.*G4UniformRand();
905    else if (tau >= tausmall)
906    {
907      G4double xsi = 3.;
908      G4double x0 = 1.;
909      G4double a = 1., ea = 0., eaa = 1.;
910      G4double b=2.,b1=3.,bx=1.,eb1=3.,ebx=1.;
911      G4double prob = 1. , qprob = 1. ;
912      G4double xmean1 = 1., xmean2 = 0.;
913      G4double xmeanth = exp(-tau);
914      G4double x2meanth = (1.+2.*exp(-2.5*tau))/3.;
915
916      G4double relloss = 1.-KineticEnergy/currentKinEnergy;
917      if(relloss > rellossmax) 
918        return SimpleScattering(xmeanth,x2meanth);
919
920      G4double theta0 = ComputeTheta0(trueStepLength,KineticEnergy);
921
922      // protection for very small angles
923      if(theta0 < tausmall) return cth;
924   
925      if(theta0 > theta0max)
926        return SimpleScattering(xmeanth,x2meanth);
927      G4double sth = sin(0.5*theta0);
928      a = 0.25/(sth*sth);
929
930      ea = exp(-xsi);
931      eaa = 1.-ea ;
932      xmean1 = 1.-(1.-(1.+xsi)*ea)/(a*eaa);
933      x0 = 1.-xsi/a;
934
935      if(xmean1 <= 0.999*xmeanth)
936        return SimpleScattering(xmeanth,x2meanth);
937
938      // from e- and muon scattering data                   
939      G4double c = coeffc1+coeffc2*y; ;                         
940
941      if(abs(c-3.) < 0.001)  c = 3.001;     
942      if(abs(c-2.) < 0.001)  c = 2.001;     
943      if(abs(c-1.) < 0.001)  c = 1.001;     
944
945      G4double c1 = c-1.;
946
947      //from continuity of derivatives
948      b = 1.+(c-xsi)/a;
949
950      b1 = b+1.;
951      bx = c/a;
952      eb1 = exp(c1*log(b1));
953      ebx = exp(c1*log(bx));
954
955      xmean2 = (x0*eb1+ebx-(eb1*bx-b1*ebx)/(c-2.))/(eb1-ebx);
956     
957      G4double f1x0 = a*ea/eaa;
958      G4double f2x0 = c1*eb1/(bx*(eb1-ebx));
959      prob = f2x0/(f1x0+f2x0);
960
961      qprob = xmeanth/(prob*xmean1+(1.-prob)*xmean2);
962
963      // sampling of costheta
964      if(G4UniformRand() < qprob)
965      {
966        if(G4UniformRand() < prob)
967          cth = 1.+log(ea+G4UniformRand()*eaa)/a ;
968        else
969          cth = b-b1*bx/exp(log(ebx+(eb1-ebx)*G4UniformRand())/c1) ;
970      }
971      else
972        cth = -1.+2.*G4UniformRand();
973    }
974  } 
975  return cth ;
976}
977
978//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
979
980G4double G4UrbanMscModel2::SimpleScattering(G4double xmeanth,G4double x2meanth)
981{
982  // 'large angle scattering'
983  // 2 model functions with correct xmean and x2mean
984  G4double a = (2.*xmeanth+9.*x2meanth-3.)/(2.*xmeanth-3.*x2meanth+1.);
985  G4double prob = (a+2.)*xmeanth/a;
986
987  // sampling
988  G4double cth = 1.;
989  if(G4UniformRand() < prob)
990    cth = -1.+2.*exp(log(G4UniformRand())/(a+1.));
991  else
992    cth = -1.+2.*G4UniformRand();
993  return cth;
994}
995
996//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
997
998G4double G4UrbanMscModel2::SampleDisplacement()
999{
1000  const G4double kappa = 2.5;
1001  const G4double kappapl1 = kappa+1.;
1002  const G4double kappami1 = kappa-1.;
1003  G4double rmean = 0.0;
1004  if ((currentTau >= tausmall) && !insideskin) {
1005    if (currentTau < taulim) {
1006      rmean = kappa*currentTau*currentTau*currentTau*
1007             (1.-kappapl1*currentTau*0.25)/6. ;
1008
1009    } else {
1010      G4double etau = 0.0;
1011      if (currentTau<taubig) etau = exp(-currentTau);
1012      rmean = -kappa*currentTau;
1013      rmean = -exp(rmean)/(kappa*kappami1);
1014      rmean += currentTau-kappapl1/kappa+kappa*etau/kappami1;
1015    }
1016    if (rmean>0.) rmean = 2.*lambdaeff*sqrt(rmean/3.0);
1017    else          rmean = 0.;
1018  }
1019
1020  // protection against z > t ...........................
1021  if(rmean > 0.) {
1022    G4double zt = (tPathLength-zPathLength)*(tPathLength+zPathLength);
1023    if(zt <= 0.)
1024      rmean = 0.;
1025    else if(rmean*rmean > zt)
1026      rmean = sqrt(zt);
1027  }
1028  return rmean;
1029}
1030
1031//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
1032
1033G4double G4UrbanMscModel2::LatCorrelation()
1034{
1035  const G4double kappa = 2.5;
1036  const G4double kappami1 = kappa-1.;
1037
1038  G4double latcorr = 0.;
1039  if((currentTau >= tausmall) && !insideskin)
1040  {
1041    if(currentTau < taulim)
1042      latcorr = lambdaeff*kappa*currentTau*currentTau*
1043                (1.-(kappa+1.)*currentTau/3.)/3.;
1044    else
1045    {
1046      G4double etau = 0.;
1047      if(currentTau < taubig) etau = exp(-currentTau);
1048      latcorr = -kappa*currentTau;
1049      latcorr = exp(latcorr)/kappami1;
1050      latcorr += 1.-kappa*etau/kappami1 ;
1051      latcorr *= 2.*lambdaeff/3. ;
1052    }
1053  }
1054
1055  return latcorr;
1056}
1057
1058//....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
Note: See TracBrowser for help on using the repository browser.