G4UrbanMscModel95.cc

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00025 //
00026 // $Id:   $
00027 // GEANT4 tag $Name:  $
00028 //
00029 // -------------------------------------------------------------------
00030 //   
00031 // GEANT4 Class file
00032 //    
00033 //
00034 // File name:   G4UrbanMscModel95
00035 //
00036 // Author:      Laszlo Urban
00037 //
00038 // Creation date: 20.03.2011
00039 //
00040 // Created from G4UrbanMscModel93
00041 //
00042 // 01-08-2011 L.Urban
00043 // new parametrization of the tail parameter c. Some of the timing 
00044 // optimization has been removed (facsafety) 
00045 // 04-09-2011 L.Urban
00046 // facsafety optimization is back for UseSafety
00047 // 10-10-2011 L.Urban 
00048 //  facsafety=0.5 instead of 0.3  
00049 // 12-04-2012 L.Urban
00050 // correction of tail for high energy/small step
00051 //
00052 //
00053 // Class Description:
00054 //
00055 // Implementation of the model of multiple scattering based on
00056 // H.W.Lewis Phys Rev 78 (1950) 526 and others
00057 
00058 // -------------------------------------------------------------------
00059 // In its present form the model can be  used for simulation 
00060 //   of the e-/e+ multiple scattering
00061 //
00062 
00063 
00064 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
00065 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
00066 
00067 #include "G4UrbanMscModel95.hh"
00068 #include "G4PhysicalConstants.hh"
00069 #include "G4SystemOfUnits.hh"
00070 #include "Randomize.hh"
00071 #include "G4Electron.hh"
00072 #include "G4LossTableManager.hh"
00073 #include "G4ParticleChangeForMSC.hh"
00074 
00075 #include "G4Poisson.hh"
00076 #include "globals.hh"
00077 #include "G4Pow.hh"
00078 
00079 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
00080 
00081 using namespace std;
00082 
00083 G4UrbanMscModel95::G4UrbanMscModel95(const G4String& nam)
00084   : G4VMscModel(nam)
00085 {
00086   masslimite    = 0.6*MeV;
00087   lambdalimit   = 1.*mm;
00088   fr            = 0.02;
00089   taubig        = 8.0;
00090   tausmall      = 1.e-16;
00091   taulim        = 1.e-6;
00092   currentTau    = taulim;
00093   tlimitminfix  = 1.e-6*mm;            
00094   stepmin       = tlimitminfix;
00095   smallstep     = 1.e10;
00096   currentRange  = 0. ;
00097   rangeinit     = 0.;
00098   tlimit        = 1.e10*mm;
00099   tlimitmin     = 10.*tlimitminfix;            
00100   tgeom         = 1.e50*mm;
00101   geombig       = 1.e50*mm;
00102   geommin       = 1.e-3*mm;
00103   geomlimit     = geombig;
00104   presafety     = 0.*mm;
00105   //facsafety     = 0.50 ;
00106                           
00107   y             = 0.;
00108 
00109   Zold          = 0.;
00110   Zeff          = 1.;
00111   Z2            = 1.;                
00112   Z23           = 1.;                    
00113   lnZ           = 0.;
00114   coeffth1      = 0.;
00115   coeffth2      = 0.;
00116   coeffc1       = 0.;
00117   coeffc2       = 0.;
00118   coeffc3       = 0.;
00119   coeffc4       = 0.;
00120   scr1ini       = fine_structure_const*fine_structure_const*
00121                   electron_mass_c2*electron_mass_c2/(0.885*0.885*4.*pi);
00122   scr2ini       = 3.76*fine_structure_const*fine_structure_const;
00123   scr1          = 0.;
00124   scr2          = 0.;
00125 
00126   theta0max     = pi/6.;
00127   rellossmax    = 0.50;
00128   third         = 1./3.;
00129   particle      = 0;
00130   theManager    = G4LossTableManager::Instance(); 
00131   firstStep     = true; 
00132   inside        = false;  
00133   insideskin    = false;
00134 
00135   skindepth = skin*stepmin;
00136 
00137   mass = proton_mass_c2;
00138   charge = ChargeSquare = 1.0;
00139   currentKinEnergy = currentRadLength = lambda0 = lambdaeff = tPathLength 
00140     = zPathLength = par1 = par2 = par3 = 0;
00141 
00142   currentMaterialIndex = -1;
00143   fParticleChange = 0;
00144   couple = 0;
00145   SetSampleZ(false);
00146 }
00147 
00148 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
00149 
00150 G4UrbanMscModel95::~G4UrbanMscModel95()
00151 {}
00152 
00153 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
00154 
00155 void G4UrbanMscModel95::Initialise(const G4ParticleDefinition* p,
00156                                    const G4DataVector&)
00157 {
00158   skindepth = skin*stepmin;
00159   //  trackID = -1;
00160 
00161   // set values of some data members
00162   SetParticle(p);
00163   /*
00164   if(p->GetPDGMass() > MeV) {
00165     G4cout << "### WARNING: G4UrbanMscModel95 model is used for " 
00166            << p->GetParticleName() << " !!! " << G4endl;
00167     G4cout << "###          This model should be used only for e+-" 
00168            << G4endl;
00169   }
00170   */
00171   fParticleChange = GetParticleChangeForMSC(p);
00172 
00173   //samplez = true;
00174   //G4cout << "### G4UrbanMscModel95::Initialise done!" << G4endl;
00175 }
00176 
00177 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
00178 
00179 G4double G4UrbanMscModel95::ComputeCrossSectionPerAtom( 
00180                              const G4ParticleDefinition* part,
00181                                    G4double KineticEnergy,
00182                                    G4double AtomicNumber,G4double,
00183                                    G4double, G4double)
00184 {
00185   static const G4double sigmafactor = 
00186     twopi*classic_electr_radius*classic_electr_radius;
00187   static const G4double epsfactor = 2.*electron_mass_c2*electron_mass_c2*
00188                             Bohr_radius*Bohr_radius/(hbarc*hbarc);
00189   static const G4double epsmin = 1.e-4 , epsmax = 1.e10;
00190 
00191   static const G4double Zdat[15] = { 4.,  6., 13., 20., 26., 29., 32., 38., 47.,
00192                                      50., 56., 64., 74., 79., 82. };
00193 
00194   static const G4double Tdat[22] = { 100*eV,  200*eV,  400*eV,  700*eV,
00195                                      1*keV,   2*keV,   4*keV,   7*keV,
00196                                      10*keV,  20*keV,  40*keV,  70*keV,
00197                                      100*keV, 200*keV, 400*keV, 700*keV,
00198                                      1*MeV,   2*MeV,   4*MeV,   7*MeV,
00199                                      10*MeV,  20*MeV};
00200 
00201   // corr. factors for e-/e+ lambda for T <= Tlim
00202   static const G4double celectron[15][22] =
00203           {{1.125,1.072,1.051,1.047,1.047,1.050,1.052,1.054,
00204             1.054,1.057,1.062,1.069,1.075,1.090,1.105,1.111,
00205             1.112,1.108,1.100,1.093,1.089,1.087            },
00206            {1.408,1.246,1.143,1.096,1.077,1.059,1.053,1.051,
00207             1.052,1.053,1.058,1.065,1.072,1.087,1.101,1.108,
00208             1.109,1.105,1.097,1.090,1.086,1.082            },
00209            {2.833,2.268,1.861,1.612,1.486,1.309,1.204,1.156,
00210             1.136,1.114,1.106,1.106,1.109,1.119,1.129,1.132,
00211             1.131,1.124,1.113,1.104,1.099,1.098            },
00212            {3.879,3.016,2.380,2.007,1.818,1.535,1.340,1.236,
00213             1.190,1.133,1.107,1.099,1.098,1.103,1.110,1.113,
00214             1.112,1.105,1.096,1.089,1.085,1.098            },
00215            {6.937,4.330,2.886,2.256,1.987,1.628,1.395,1.265,
00216             1.203,1.122,1.080,1.065,1.061,1.063,1.070,1.073,
00217             1.073,1.070,1.064,1.059,1.056,1.056            },
00218            {9.616,5.708,3.424,2.551,2.204,1.762,1.485,1.330,
00219             1.256,1.155,1.099,1.077,1.070,1.068,1.072,1.074,
00220             1.074,1.070,1.063,1.059,1.056,1.052            },
00221            {11.72,6.364,3.811,2.806,2.401,1.884,1.564,1.386,
00222             1.300,1.180,1.112,1.082,1.073,1.066,1.068,1.069,
00223             1.068,1.064,1.059,1.054,1.051,1.050            },
00224            {18.08,8.601,4.569,3.183,2.662,2.025,1.646,1.439,
00225             1.339,1.195,1.108,1.068,1.053,1.040,1.039,1.039,
00226             1.039,1.037,1.034,1.031,1.030,1.036            },
00227            {18.22,10.48,5.333,3.713,3.115,2.367,1.898,1.631,
00228             1.498,1.301,1.171,1.105,1.077,1.048,1.036,1.033,
00229             1.031,1.028,1.024,1.022,1.021,1.024            },
00230            {14.14,10.65,5.710,3.929,3.266,2.453,1.951,1.669,
00231             1.528,1.319,1.178,1.106,1.075,1.040,1.027,1.022,
00232             1.020,1.017,1.015,1.013,1.013,1.020            },
00233            {14.11,11.73,6.312,4.240,3.478,2.566,2.022,1.720,
00234             1.569,1.342,1.186,1.102,1.065,1.022,1.003,0.997,
00235             0.995,0.993,0.993,0.993,0.993,1.011            },
00236            {22.76,20.01,8.835,5.287,4.144,2.901,2.219,1.855,
00237             1.677,1.410,1.224,1.121,1.073,1.014,0.986,0.976,
00238             0.974,0.972,0.973,0.974,0.975,0.987            },
00239            {50.77,40.85,14.13,7.184,5.284,3.435,2.520,2.059,
00240             1.837,1.512,1.283,1.153,1.091,1.010,0.969,0.954,
00241             0.950,0.947,0.949,0.952,0.954,0.963            },
00242            {65.87,59.06,15.87,7.570,5.567,3.650,2.682,2.182,
00243             1.939,1.579,1.325,1.178,1.108,1.014,0.965,0.947,
00244             0.941,0.938,0.940,0.944,0.946,0.954            },
00245            {55.60,47.34,15.92,7.810,5.755,3.767,2.760,2.239,
00246             1.985,1.609,1.343,1.188,1.113,1.013,0.960,0.939,
00247             0.933,0.930,0.933,0.936,0.939,0.949            }};
00248             
00249   static const G4double cpositron[15][22] = {
00250            {2.589,2.044,1.658,1.446,1.347,1.217,1.144,1.110,
00251             1.097,1.083,1.080,1.086,1.092,1.108,1.123,1.131,
00252             1.131,1.126,1.117,1.108,1.103,1.100            },
00253            {3.904,2.794,2.079,1.710,1.543,1.325,1.202,1.145,
00254             1.122,1.096,1.089,1.092,1.098,1.114,1.130,1.137,
00255             1.138,1.132,1.122,1.113,1.108,1.102            },
00256            {7.970,6.080,4.442,3.398,2.872,2.127,1.672,1.451,
00257             1.357,1.246,1.194,1.179,1.178,1.188,1.201,1.205,
00258             1.203,1.190,1.173,1.159,1.151,1.145            },
00259            {9.714,7.607,5.747,4.493,3.815,2.777,2.079,1.715,
00260             1.553,1.353,1.253,1.219,1.211,1.214,1.225,1.228,
00261             1.225,1.210,1.191,1.175,1.166,1.174            },
00262            {17.97,12.95,8.628,6.065,4.849,3.222,2.275,1.820,
00263             1.624,1.382,1.259,1.214,1.202,1.202,1.214,1.219,
00264             1.217,1.203,1.184,1.169,1.160,1.151            },
00265            {24.83,17.06,10.84,7.355,5.767,3.707,2.546,1.996,
00266             1.759,1.465,1.311,1.252,1.234,1.228,1.238,1.241,
00267             1.237,1.222,1.201,1.184,1.174,1.159            },
00268            {23.26,17.15,11.52,8.049,6.375,4.114,2.792,2.155,
00269             1.880,1.535,1.353,1.281,1.258,1.247,1.254,1.256,
00270             1.252,1.234,1.212,1.194,1.183,1.170            },
00271            {22.33,18.01,12.86,9.212,7.336,4.702,3.117,2.348,
00272             2.015,1.602,1.385,1.297,1.268,1.251,1.256,1.258,
00273             1.254,1.237,1.214,1.195,1.185,1.179            },
00274            {33.91,24.13,15.71,10.80,8.507,5.467,3.692,2.808,
00275             2.407,1.873,1.564,1.425,1.374,1.330,1.324,1.320,
00276             1.312,1.288,1.258,1.235,1.221,1.205            },
00277            {32.14,24.11,16.30,11.40,9.015,5.782,3.868,2.917,
00278             2.490,1.925,1.596,1.447,1.391,1.342,1.332,1.327,
00279             1.320,1.294,1.264,1.240,1.226,1.214            },
00280            {29.51,24.07,17.19,12.28,9.766,6.238,4.112,3.066,
00281             2.602,1.995,1.641,1.477,1.414,1.356,1.342,1.336,
00282             1.328,1.302,1.270,1.245,1.231,1.233            },
00283            {38.19,30.85,21.76,15.35,12.07,7.521,4.812,3.498,
00284             2.926,2.188,1.763,1.563,1.484,1.405,1.382,1.371,
00285             1.361,1.330,1.294,1.267,1.251,1.239            },
00286            {49.71,39.80,27.96,19.63,15.36,9.407,5.863,4.155,
00287             3.417,2.478,1.944,1.692,1.589,1.480,1.441,1.423,
00288             1.409,1.372,1.330,1.298,1.280,1.258            },
00289            {59.25,45.08,30.36,20.83,16.15,9.834,6.166,4.407,
00290             3.641,2.648,2.064,1.779,1.661,1.531,1.482,1.459,
00291             1.442,1.400,1.354,1.319,1.299,1.272            },
00292            {56.38,44.29,30.50,21.18,16.51,10.11,6.354,4.542,
00293             3.752,2.724,2.116,1.817,1.692,1.554,1.499,1.474,
00294             1.456,1.412,1.364,1.328,1.307,1.282            }};
00295 
00296   //data/corrections for T > Tlim  
00297   static const G4double Tlim = 10.*MeV;
00298   static const G4double beta2lim = Tlim*(Tlim+2.*electron_mass_c2)/
00299                       ((Tlim+electron_mass_c2)*(Tlim+electron_mass_c2));
00300   static const G4double bg2lim   = Tlim*(Tlim+2.*electron_mass_c2)/
00301                       (electron_mass_c2*electron_mass_c2);
00302 
00303   static const G4double sig0[15] = {
00304                      0.2672*barn,  0.5922*barn, 2.653*barn,  6.235*barn,
00305                       11.69*barn  , 13.24*barn  , 16.12*barn, 23.00*barn ,
00306                       35.13*barn  , 39.95*barn  , 50.85*barn, 67.19*barn ,
00307                       91.15*barn  , 104.4*barn  , 113.1*barn};
00308                                        
00309   static const G4double hecorr[15] = {
00310                          120.70, 117.50, 105.00, 92.92, 79.23,  74.510,  68.29,
00311                           57.39,  41.97,  36.14, 24.53, 10.21,  -7.855, -16.84,
00312                          -22.30};
00313 
00314   G4double sigma;
00315   SetParticle(part);
00316 
00317   Z23 = G4Pow::GetInstance()->Z23(G4lrint(AtomicNumber));
00318 
00319   // correction if particle .ne. e-/e+
00320   // compute equivalent kinetic energy
00321   // lambda depends on p*beta ....
00322 
00323   G4double eKineticEnergy = KineticEnergy;
00324 
00325   if(mass > electron_mass_c2)
00326   {
00327      G4double TAU = KineticEnergy/mass ;
00328      G4double c = mass*TAU*(TAU+2.)/(electron_mass_c2*(TAU+1.)) ;
00329      G4double w = c-2. ;
00330      G4double tau = 0.5*(w+sqrt(w*w+4.*c)) ;
00331      eKineticEnergy = electron_mass_c2*tau ;
00332   }
00333 
00334   G4double eTotalEnergy = eKineticEnergy + electron_mass_c2 ;
00335   G4double beta2 = eKineticEnergy*(eTotalEnergy+electron_mass_c2)
00336                                  /(eTotalEnergy*eTotalEnergy);
00337   G4double bg2   = eKineticEnergy*(eTotalEnergy+electron_mass_c2)
00338                                  /(electron_mass_c2*electron_mass_c2);
00339 
00340   G4double eps = epsfactor*bg2/Z23;
00341 
00342   if     (eps<epsmin)  sigma = 2.*eps*eps;
00343   else if(eps<epsmax)  sigma = log(1.+2.*eps)-2.*eps/(1.+2.*eps);
00344   else                 sigma = log(2.*eps)-1.+1./eps;
00345 
00346   sigma *= ChargeSquare*AtomicNumber*AtomicNumber/(beta2*bg2);
00347 
00348   // interpolate in AtomicNumber and beta2 
00349   G4double c1,c2,cc1,cc2,corr;
00350 
00351   // get bin number in Z
00352   G4int iZ = 14;
00353   while ((iZ>=0)&&(Zdat[iZ]>=AtomicNumber)) iZ -= 1;
00354   if (iZ==14)                               iZ = 13;
00355   if (iZ==-1)                               iZ = 0 ;
00356 
00357   G4double ZZ1 = Zdat[iZ];
00358   G4double ZZ2 = Zdat[iZ+1];
00359   G4double ratZ = (AtomicNumber-ZZ1)*(AtomicNumber+ZZ1)/
00360                   ((ZZ2-ZZ1)*(ZZ2+ZZ1));
00361 
00362   if(eKineticEnergy <= Tlim) 
00363   {
00364     // get bin number in T (beta2)
00365     G4int iT = 21;
00366     while ((iT>=0)&&(Tdat[iT]>=eKineticEnergy)) iT -= 1;
00367     if(iT==21)                                  iT = 20;
00368     if(iT==-1)                                  iT = 0 ;
00369 
00370     //  calculate betasquare values
00371     G4double T = Tdat[iT],   E = T + electron_mass_c2;
00372     G4double b2small = T*(E+electron_mass_c2)/(E*E);
00373 
00374     T = Tdat[iT+1]; E = T + electron_mass_c2;
00375     G4double b2big = T*(E+electron_mass_c2)/(E*E);
00376     G4double ratb2 = (beta2-b2small)/(b2big-b2small);
00377 
00378     if (charge < 0.)
00379     {
00380        c1 = celectron[iZ][iT];
00381        c2 = celectron[iZ+1][iT];
00382        cc1 = c1+ratZ*(c2-c1);
00383 
00384        c1 = celectron[iZ][iT+1];
00385        c2 = celectron[iZ+1][iT+1];
00386        cc2 = c1+ratZ*(c2-c1);
00387 
00388        corr = cc1+ratb2*(cc2-cc1);
00389 
00390        sigma *= sigmafactor/corr;
00391     }
00392     else              
00393     {
00394        c1 = cpositron[iZ][iT];
00395        c2 = cpositron[iZ+1][iT];
00396        cc1 = c1+ratZ*(c2-c1);
00397 
00398        c1 = cpositron[iZ][iT+1];
00399        c2 = cpositron[iZ+1][iT+1];
00400        cc2 = c1+ratZ*(c2-c1);
00401 
00402        corr = cc1+ratb2*(cc2-cc1);
00403 
00404        sigma *= sigmafactor/corr;
00405     }
00406   }
00407   else
00408   {
00409     c1 = bg2lim*sig0[iZ]*(1.+hecorr[iZ]*(beta2-beta2lim))/bg2;
00410     c2 = bg2lim*sig0[iZ+1]*(1.+hecorr[iZ+1]*(beta2-beta2lim))/bg2;
00411     if((AtomicNumber >= ZZ1) && (AtomicNumber <= ZZ2))
00412       sigma = c1+ratZ*(c2-c1) ;
00413     else if(AtomicNumber < ZZ1)
00414       sigma = AtomicNumber*AtomicNumber*c1/(ZZ1*ZZ1);
00415     else if(AtomicNumber > ZZ2)
00416       sigma = AtomicNumber*AtomicNumber*c2/(ZZ2*ZZ2);
00417   }
00418   return sigma;
00419 
00420 }
00421 
00422 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
00423 
00424 void G4UrbanMscModel95::StartTracking(G4Track* track)
00425 {
00426   SetParticle(track->GetDynamicParticle()->GetDefinition());
00427   firstStep = true; 
00428   inside = false;
00429   insideskin = false;
00430   tlimit = geombig;
00431   stepmin = tlimitminfix ;
00432   tlimitmin = 10.*stepmin ;
00433 }
00434 
00435 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
00436 
00437 G4double G4UrbanMscModel95::ComputeTruePathLengthLimit(
00438                              const G4Track& track,
00439                              G4double& currentMinimalStep)
00440 {
00441   tPathLength = currentMinimalStep;
00442   const G4DynamicParticle* dp = track.GetDynamicParticle();
00443   
00444   G4StepPoint* sp = track.GetStep()->GetPreStepPoint();
00445   G4StepStatus stepStatus = sp->GetStepStatus();
00446   couple = track.GetMaterialCutsCouple();
00447   SetCurrentCouple(couple); 
00448   currentMaterialIndex = couple->GetIndex();
00449   currentKinEnergy = dp->GetKineticEnergy();
00450   currentRange = GetRange(particle,currentKinEnergy,couple);
00451   lambda0 = GetTransportMeanFreePath(particle,currentKinEnergy);
00452   if(tPathLength > currentRange) { tPathLength = currentRange; }
00453 
00454   // stop here if small range particle
00455   if(inside || tPathLength < tlimitminfix) { 
00456     return ConvertTrueToGeom(tPathLength, currentMinimalStep); 
00457   }
00458   
00459   presafety = sp->GetSafety();
00460   /*
00461   G4cout << "G4Urban95::StepLimit tPathLength= " 
00462          <<tPathLength<<" safety= " << presafety
00463           << " range= " <<currentRange<< " lambda= "<<lambda0
00464          << " Alg: " << steppingAlgorithm <<G4endl;
00465   */
00466   // far from geometry boundary
00467   if(currentRange < presafety)
00468     {
00469       inside = true;
00470       return ConvertTrueToGeom(tPathLength, currentMinimalStep);  
00471     }
00472 
00473   // standard  version
00474   //
00475   if (steppingAlgorithm == fUseDistanceToBoundary)
00476     {
00477       //compute geomlimit and presafety 
00478       geomlimit = ComputeGeomLimit(track, presafety, currentRange);
00479 
00480       // is it far from boundary ?
00481       if(currentRange < presafety)
00482         {
00483           inside = true;
00484           return ConvertTrueToGeom(tPathLength, currentMinimalStep);   
00485         }
00486 
00487       smallstep += 1.;
00488       insideskin = false;
00489 
00490       if(firstStep || (stepStatus == fGeomBoundary))
00491         {
00492           rangeinit = currentRange;
00493           if(firstStep) smallstep = 1.e10;
00494           else  smallstep = 1.;
00495 
00496           //define stepmin here (it depends on lambda!)
00497           //rough estimation of lambda_elastic/lambda_transport
00498           G4double rat = currentKinEnergy/MeV ;
00499           rat = 1.e-3/(rat*(10.+rat)) ;
00500           //stepmin ~ lambda_elastic
00501           stepmin = rat*lambda0;
00502           skindepth = skin*stepmin;
00503           //define tlimitmin
00504           tlimitmin = 10.*stepmin;
00505           if(tlimitmin < tlimitminfix) tlimitmin = tlimitminfix;
00506           //G4cout << "rangeinit= " << rangeinit << " stepmin= " << stepmin
00507           //     << " tlimitmin= " << tlimitmin << " geomlimit= " << geomlimit <<G4endl;
00508           // constraint from the geometry
00509           if((geomlimit < geombig) && (geomlimit > geommin))
00510             {
00511               // geomlimit is a geometrical step length
00512               // transform it to true path length (estimation)
00513               if((1.-geomlimit/lambda0) > 0.)
00514                 geomlimit = -lambda0*log(1.-geomlimit/lambda0)+tlimitmin ;
00515 
00516               if(stepStatus == fGeomBoundary)
00517                 tgeom = geomlimit/facgeom;
00518               else
00519                 tgeom = 2.*geomlimit/facgeom;
00520             }
00521             else
00522               tgeom = geombig;
00523         }
00524 
00525 
00526       //step limit 
00527       tlimit = facrange*rangeinit;              
00528 
00529       //lower limit for tlimit
00530       if(tlimit < tlimitmin) tlimit = tlimitmin;
00531 
00532       if(tlimit > tgeom) tlimit = tgeom;
00533 
00534       //G4cout << "tgeom= " << tgeom << " geomlimit= " << geomlimit  
00535       //      << " tlimit= " << tlimit << " presafety= " << presafety << G4endl;
00536 
00537       // shortcut
00538       if((tPathLength < tlimit) && (tPathLength < presafety) &&
00539          (smallstep > skin) && (tPathLength < geomlimit-0.999*skindepth))
00540         return ConvertTrueToGeom(tPathLength, currentMinimalStep);   
00541 
00542       // step reduction near to boundary
00543       if(smallstep <= skin)
00544         {
00545           tlimit = stepmin;
00546           insideskin = true;
00547         }
00548       else if(geomlimit < geombig)
00549         {
00550           if(geomlimit > skindepth)
00551             {
00552               if(tlimit > geomlimit-0.999*skindepth)
00553                 tlimit = geomlimit-0.999*skindepth;
00554             }
00555           else
00556             {
00557               insideskin = true;
00558               if(tlimit > stepmin) tlimit = stepmin;
00559             }
00560         }
00561 
00562       if(tlimit < stepmin) tlimit = stepmin;
00563 
00564       // randomize 1st step or 1st 'normal' step in volume
00565       if(firstStep || ((smallstep == skin) && !insideskin)) 
00566         { 
00567           G4double temptlimit = tlimit;
00568           if(temptlimit > tlimitmin)
00569           {
00570             do {
00571               temptlimit = G4RandGauss::shoot(tlimit,0.3*tlimit);        
00572                } while ((temptlimit < tlimitmin) || 
00573                         (temptlimit > 2.*tlimit-tlimitmin));
00574           }
00575           else
00576             temptlimit = tlimitmin;
00577           if(tPathLength > temptlimit) tPathLength = temptlimit;
00578         }
00579       else
00580         {  
00581           if(tPathLength > tlimit) tPathLength = tlimit  ; 
00582         }
00583 
00584     }
00585     // for 'normal' simulation with or without magnetic field 
00586     //  there no small step/single scattering at boundaries
00587   else if(steppingAlgorithm == fUseSafety)
00588     {
00589       // compute presafety again if presafety <= 0 and no boundary
00590       // i.e. when it is needed for optimization purposes
00591       if((stepStatus != fGeomBoundary) && (presafety < tlimitminfix)) 
00592         presafety = ComputeSafety(sp->GetPosition(),tPathLength); 
00593       /*
00594       G4cout << "presafety= " << presafety
00595              << " firstStep= " << firstStep
00596              << " stepStatus= " << stepStatus 
00597              << G4endl;
00598       */
00599       // is far from boundary
00600       if(currentRange < presafety)
00601         {
00602           inside = true;
00603           return ConvertTrueToGeom(tPathLength, currentMinimalStep);  
00604         }
00605 
00606       if(firstStep || stepStatus == fGeomBoundary)
00607       {
00608         rangeinit = currentRange;
00609         fr = facrange;
00610         // 9.1 like stepping for e+/e- only (not for muons,hadrons)
00611         if(mass < masslimite) 
00612         {
00613           if(lambda0 > currentRange)
00614             rangeinit = lambda0;
00615           if(lambda0 > lambdalimit)
00616             fr *= 0.75+0.25*lambda0/lambdalimit;
00617         }
00618 
00619         //lower limit for tlimit
00620         G4double rat = currentKinEnergy/MeV ;
00621         rat = 1.e-3/(rat*(10.+rat)) ;
00622         tlimitmin = 10.*lambda0*rat;
00623         if(tlimitmin < tlimitminfix) tlimitmin = tlimitminfix;
00624       }
00625       //step limit
00626       tlimit = fr*rangeinit;               
00627 
00628       if(tlimit < facsafety*presafety)
00629         tlimit = facsafety*presafety;
00630 
00631       //lower limit for tlimit
00632       if(tlimit < tlimitmin) tlimit = tlimitmin;
00633       
00634       if(tPathLength > tlimit) tPathLength = tlimit;
00635 
00636     }
00637   
00638   // version similar to 7.1 (needed for some experiments)
00639   else
00640     {
00641       if (stepStatus == fGeomBoundary)
00642         {
00643           if (currentRange > lambda0) tlimit = facrange*currentRange;
00644           else                        tlimit = facrange*lambda0;
00645 
00646           if(tlimit < tlimitmin) tlimit = tlimitmin;
00647           if(tPathLength > tlimit) tPathLength = tlimit;
00648         }
00649     }
00650   //G4cout << "tPathLength= " << tPathLength 
00651   //     << " currentMinimalStep= " << currentMinimalStep << G4endl;
00652   return ConvertTrueToGeom(tPathLength, currentMinimalStep);
00653 }
00654 
00655 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
00656 
00657 G4double G4UrbanMscModel95::ComputeGeomPathLength(G4double)
00658 {
00659   firstStep = false; 
00660   lambdaeff = lambda0;
00661   par1 = -1. ;  
00662   par2 = par3 = 0. ;  
00663 
00664   //  do the true -> geom transformation
00665   zPathLength = tPathLength;
00666 
00667   // z = t for very small tPathLength
00668   if(tPathLength < tlimitminfix) return zPathLength;
00669 
00670   // this correction needed to run MSC with eIoni and eBrem inactivated
00671   // and makes no harm for a normal run
00672   // It is already checked
00673   // if(tPathLength > currentRange)
00674   //  tPathLength = currentRange ;
00675 
00676   G4double tau   = tPathLength/lambda0 ;
00677 
00678   if ((tau <= tausmall) || insideskin) {
00679     zPathLength  = tPathLength;
00680     if(zPathLength > lambda0) zPathLength = lambda0;
00681     return zPathLength;
00682   }
00683 
00684   G4double zmean = tPathLength;
00685   if (tPathLength < currentRange*dtrl) {
00686     if(tau < taulim) zmean = tPathLength*(1.-0.5*tau) ;
00687     else             zmean = lambda0*(1.-exp(-tau));
00688     zPathLength = zmean ;
00689     return zPathLength;    
00690 
00691   } else if(currentKinEnergy < mass || tPathLength == currentRange)  {
00692     par1 = 1./currentRange ;
00693     par2 = 1./(par1*lambda0) ;
00694     par3 = 1.+par2 ;
00695     if(tPathLength < currentRange)
00696       zmean = (1.-exp(par3*log(1.-tPathLength/currentRange)))/(par1*par3) ;
00697     else {
00698       zmean = 1./(par1*par3) ;
00699     }
00700     zPathLength = zmean ;
00701     return zPathLength;    
00702 
00703   } else {
00704     G4double T1 = GetEnergy(particle,currentRange-tPathLength,couple);
00705     G4double lambda1 = GetTransportMeanFreePath(particle,T1);
00706 
00707     par1 = (lambda0-lambda1)/(lambda0*tPathLength);
00708     par2 = 1./(par1*lambda0);
00709     par3 = 1.+par2 ;
00710     zmean = (1.-exp(par3*log(lambda1/lambda0)))/(par1*par3);
00711   }
00712 
00713   zPathLength = zmean;
00714 
00715   //  sample z
00716   if(samplez)
00717   {
00718     const G4double  ztmax = 0.999 ;
00719     G4double zt = zmean/tPathLength ;
00720 
00721     if (tPathLength > stepmin && zt < ztmax)              
00722     {
00723       G4double u,cz1;
00724       if(zt >= third)
00725       {
00726         G4double cz = 0.5*(3.*zt-1.)/(1.-zt) ;
00727         cz1 = 1.+cz ;
00728         G4double u0 = cz/cz1 ;
00729         G4double grej ;
00730         do {
00731             u = exp(log(G4UniformRand())/cz1) ;
00732             grej = exp(cz*log(u/u0))*(1.-u)/(1.-u0) ;
00733            } while (grej < G4UniformRand()) ;
00734       }
00735       else
00736       {
00737         u = 2.*zt*G4UniformRand();
00738       }
00739       zPathLength = tPathLength*u ;
00740     }
00741   }
00742 
00743   if(zPathLength > lambda0) { zPathLength = lambda0; }
00744   //G4cout<< "zPathLength= "<< zPathLength<< " lambda1= " << lambda0 << G4endl;
00745   return zPathLength;
00746 }
00747 
00748 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
00749 
00750 G4double G4UrbanMscModel95::ComputeTrueStepLength(G4double geomStepLength)
00751 {
00752   // step defined other than transportation 
00753   if(geomStepLength == zPathLength)
00754     { return tPathLength; }
00755 
00756   zPathLength = geomStepLength;
00757 
00758   // t = z for very small step
00759   if(geomStepLength < tlimitminfix) { 
00760     tPathLength = geomStepLength; 
00761   
00762   // recalculation
00763   } else {
00764 
00765     G4double tlength = geomStepLength;
00766     if((geomStepLength > lambda0*tausmall) && !insideskin) {
00767 
00768       if(par1 <  0.) {
00769         tlength = -lambda0*log(1.-geomStepLength/lambda0) ;
00770       } else {
00771         if(par1*par3*geomStepLength < 1.) {
00772           tlength = (1.-exp(log(1.-par1*par3*geomStepLength)/par3))/par1 ;
00773         } else {
00774           tlength = currentRange;
00775         }
00776       }
00777       if(tlength < geomStepLength)   { tlength = geomStepLength; }
00778       else if(tlength > tPathLength) { tlength = tPathLength; }
00779     }  
00780     tPathLength = tlength; 
00781   }
00782   //G4cout << "Urban95::ComputeTrueLength: tPathLength= " << tPathLength 
00783   //     << " step= " << geomStepLength << G4endl;
00784 
00785   return tPathLength;
00786 }
00787 
00788 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
00789 
00790 G4double G4UrbanMscModel95::ComputeTheta0(G4double trueStepLength,
00791                                           G4double KineticEnergy)
00792 {
00793   // for all particles take the width of the central part
00794   //  from a  parametrization similar to the Highland formula
00795   // ( Highland formula: Particle Physics Booklet, July 2002, eq. 26.10)
00796   static const G4double c_highland = 13.6*MeV ;
00797   G4double betacp = sqrt(currentKinEnergy*(currentKinEnergy+2.*mass)*
00798                          KineticEnergy*(KineticEnergy+2.*mass)/
00799                       ((currentKinEnergy+mass)*(KineticEnergy+mass)));
00800   y = trueStepLength/currentRadLength;
00801   G4double theta0 = c_highland*std::abs(charge)*sqrt(y)/betacp;
00802   y = log(y);
00803   // correction factor from e- scattering data
00804   G4double corr = coeffth1+coeffth2*y;                
00805 
00806   theta0 *= corr ;                                               
00807 
00808   return theta0;
00809 }
00810 
00811 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
00812 
00813 G4ThreeVector& 
00814 G4UrbanMscModel95::SampleScattering(const G4ThreeVector& oldDirection,
00815                                     G4double safety)
00816 {
00817   fDisplacement.set(0.0,0.0,0.0);
00818   G4double kineticEnergy = currentKinEnergy;
00819   if (tPathLength > currentRange*dtrl) {
00820     kineticEnergy = GetEnergy(particle,currentRange-tPathLength,couple);
00821   } else {
00822     kineticEnergy -= tPathLength*GetDEDX(particle,currentKinEnergy,couple);
00823   }
00824 
00825   if((kineticEnergy <= eV) || (tPathLength <= tlimitminfix) ||
00826      (tPathLength/tausmall < lambda0)) { return fDisplacement; }
00827 
00828   G4double cth  = SampleCosineTheta(tPathLength,kineticEnergy);
00829 
00830   // protection against 'bad' cth values
00831   if(std::fabs(cth) > 1.) { return fDisplacement; }
00832 
00833   // extra protection agaist high energy particles backscattered 
00834     //G4cout << "Warning: large scattering E(MeV)= " << kineticEnergy 
00835     //     << " s(mm)= " << tPathLength/mm
00836     //     << " 1-cosTheta= " << 1.0 - cth << G4endl;
00837     // do Gaussian central scattering
00838   //if(kineticEnergy > 5*GeV && cth < 0.9) {
00839   /*
00840   if(cth < 1.0 - 1000*tPathLength/lambda0 
00841      && cth < 0.8 && kineticEnergy > 20*MeV) { 
00842     G4ExceptionDescription ed;
00843     ed << particle->GetParticleName()
00844        << " E(MeV)= " << kineticEnergy/MeV
00845        << " Step(mm)= " << tPathLength/mm
00846        << " in " << CurrentCouple()->GetMaterial()->GetName()
00847        << " CosTheta= " << cth 
00848        << " is too big";
00849     G4Exception("G4UrbanMscModel95::SampleScattering","em0004",
00850                 JustWarning, ed,"");
00851                 }
00852   */
00853 
00854   G4double sth  = sqrt((1.0 - cth)*(1.0 + cth));
00855   G4double phi  = twopi*G4UniformRand();
00856   G4double dirx = sth*cos(phi);
00857   G4double diry = sth*sin(phi);
00858 
00859   G4ThreeVector newDirection(dirx,diry,cth);
00860   newDirection.rotateUz(oldDirection);
00861   fParticleChange->ProposeMomentumDirection(newDirection);
00862   /*
00863   G4cout << "G4UrbanMscModel95::SampleSecondaries: e(MeV)= " << kineticEnergy
00864          << " sinTheta= " << sth << " safety(mm)= " << safety
00865          << " trueStep(mm)= " << tPathLength
00866          << " geomStep(mm)= " << zPathLength
00867          << G4endl;
00868   */
00869   if (latDisplasment && safety > tlimitminfix) {
00870 
00871     G4double r = SampleDisplacement();
00872     /*    
00873     G4cout << "G4UrbanMscModel95::SampleSecondaries: e(MeV)= " << kineticEnergy
00874            << " sinTheta= " << sth << " r(mm)= " << r
00875            << " trueStep(mm)= " << tPathLength
00876            << " geomStep(mm)= " << zPathLength
00877            << G4endl;
00878     */
00879     if(r > 0.)
00880       {
00881         G4double latcorr = LatCorrelation();
00882         if(latcorr > r) latcorr = r;
00883 
00884         // sample direction of lateral displacement
00885         // compute it from the lateral correlation
00886         G4double Phi = 0.;
00887         if(std::abs(r*sth) < latcorr)
00888           Phi  = twopi*G4UniformRand();
00889         else
00890         {
00891           G4double psi = std::acos(latcorr/(r*sth));
00892           if(G4UniformRand() < 0.5)
00893             Phi = phi+psi;
00894           else
00895             Phi = phi-psi;
00896         }
00897 
00898         dirx = std::cos(Phi);
00899         diry = std::sin(Phi);
00900 
00901         fDisplacement.set(r*dirx,r*diry,0.0);
00902         fDisplacement.rotateUz(oldDirection);
00903       }
00904   }
00905   return fDisplacement;
00906 }
00907 
00908 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
00909 
00910 G4double G4UrbanMscModel95::SampleCosineTheta(G4double trueStepLength,
00911                                               G4double KineticEnergy)
00912 {
00913   G4double cth = 1. ;
00914   G4double tau = trueStepLength/lambda0;
00915   currentTau   = tau;
00916   lambdaeff    = lambda0;
00917 
00918   Zeff = couple->GetMaterial()->GetTotNbOfElectPerVolume()/
00919          couple->GetMaterial()->GetTotNbOfAtomsPerVolume() ;
00920 
00921   if(Zold != Zeff)  
00922     UpdateCache();
00923 
00924   if(insideskin)
00925   {
00926     //no scattering, single or plural scattering
00927     G4double mean = trueStepLength/stepmin ;
00928 
00929     G4int n = G4Poisson(mean);
00930     if(n > 0)
00931     {
00932       //screening (Moliere-Bethe)
00933       G4double mom2 = KineticEnergy*(2.*mass+KineticEnergy);
00934       G4double beta2 = mom2/((KineticEnergy+mass)*(KineticEnergy+mass));
00935       G4double ascr = scr1/mom2;
00936       ascr *= 1.13+scr2/beta2;
00937       G4double ascr1 = 1.+2.*ascr;
00938       G4double bp1=ascr1+1.;
00939       G4double bm1=ascr1-1.;
00940 
00941       // single scattering from screened Rutherford x-section
00942       G4double ct,st,phi;
00943       G4double sx=0.,sy=0.,sz=0.;
00944       for(G4int i=1; i<=n; i++)
00945       {
00946         ct = ascr1-bp1*bm1/(2.*G4UniformRand()+bm1);
00947         if(ct < -1.) ct = -1.;
00948         if(ct >  1.) ct =  1.; 
00949         st = sqrt(1.-ct*ct);
00950         phi = twopi*G4UniformRand();
00951         sx += st*cos(phi);
00952         sy += st*sin(phi);
00953         sz += ct;
00954       }
00955       cth = sz/sqrt(sx*sx+sy*sy+sz*sz);
00956     }
00957   }
00958   else
00959   {
00960     G4double lambda1 = GetTransportMeanFreePath(particle,KineticEnergy);
00961     if(std::fabs(lambda1/lambda0 - 1) > 0.01 && lambda1 > 0.)
00962     {
00963       // mean tau value
00964       tau = trueStepLength*log(lambda0/lambda1)/(lambda0-lambda1);
00965     }
00966 
00967     currentTau = tau ;
00968     lambdaeff = trueStepLength/currentTau;
00969     currentRadLength = couple->GetMaterial()->GetRadlen();
00970 
00971     if (tau >= taubig) cth = -1.+2.*G4UniformRand();
00972     else if (tau >= tausmall)
00973     {
00974       static const G4double numlim = 0.01;
00975       G4double xmeanth, x2meanth;
00976       if(tau < numlim) {
00977         xmeanth = 1.0 - tau*(1.0 - 0.5*tau);
00978         x2meanth= 1.0 - tau*(5.0 - 6.25*tau)/3.;
00979       } else {
00980         xmeanth = exp(-tau);
00981         x2meanth = (1.+2.*exp(-2.5*tau))/3.;
00982       }
00983       G4double relloss = 1.-KineticEnergy/currentKinEnergy;
00984 
00985       if(relloss > rellossmax) 
00986         return SimpleScattering(xmeanth,x2meanth);
00987 
00988       G4double theta0 = ComputeTheta0(trueStepLength,KineticEnergy);
00989 
00990       //G4cout << "Theta0= " << theta0 << " theta0max= " << theta0max 
00991       //             << "  sqrt(tausmall)= " << sqrt(tausmall) << G4endl;
00992 
00993       // protection for very small angles
00994       G4double theta2 = theta0*theta0;
00995 
00996       if(theta2 < tausmall) { return cth; }
00997     
00998       if(theta0 > theta0max) {
00999         return SimpleScattering(xmeanth,x2meanth);
01000       }
01001 
01002       G4double x = theta2*(1.0 - theta2/12.);
01003       if(theta2 > numlim) {
01004         G4double sth = 2*sin(0.5*theta0);
01005         x = sth*sth;
01006       }
01007 
01008       // parameter for tail
01009       G4double ltau= log(tau);
01010       G4double u   = exp(ltau/6.);
01011       G4double xx  = log(lambdaeff/currentRadLength);
01012       G4double xsi = coeffc1+u*(coeffc2+coeffc3*u)+coeffc4*xx;
01013       G4double   c = xsi;
01014 
01015       //correction of tail for high energy/small step
01016       if(ltau < -10.63)
01017         { c *= (0.016*ltau+1.17008); }
01018 
01019       // tail should not be too big
01020       if(c < 1.9) { 
01021         /*
01022         if(KineticEnergy > 20*MeV && c < 1.6) {
01023           G4cout << "G4UrbanMscModel95::SampleCosineTheta: E(GeV)= " 
01024                  << KineticEnergy/GeV 
01025                  << " !!** c= " << c
01026                  << " **!! length(mm)= " << trueStepLength << " Zeff= " << Zeff 
01027                  << " " << couple->GetMaterial()->GetName()
01028                  << " tau= " << tau << G4endl;
01029         }
01030         */
01031         c = 1.9; 
01032       }
01033 
01034       if(fabs(c-3.) < 0.001)      { c = 3.001; }
01035       else if(fabs(c-2.) < 0.001) { c = 2.001; }
01036 
01037       G4double c1 = c-1.;
01038 
01039       G4double ea = exp(-xsi);
01040       G4double eaa = 1.-ea ;
01041       G4double xmean1 = 1.-(1.-(1.+xsi)*ea)*x/eaa;
01042       G4double x0 = 1. - xsi*x;
01043 
01044       // G4cout << " xmean1= " << xmean1 << "  xmeanth= " << xmeanth << G4endl;
01045 
01046       if(xmean1 <= 0.999*xmeanth) {
01047         return SimpleScattering(xmeanth,x2meanth);
01048       }
01049       //from continuity of derivatives
01050       G4double b = 1.+(c-xsi)*x;
01051 
01052       G4double b1 = b+1.;
01053       G4double bx = c*x;
01054 
01055       G4double eb1 = pow(b1,c1);
01056       G4double ebx = pow(bx,c1);
01057       G4double d = ebx/eb1;
01058 
01059       G4double xmean2 = (x0 + d - (bx - b1*d)/(c-2.))/(1. - d);
01060 
01061       G4double f1x0 = ea/eaa;
01062       G4double f2x0 = c1/(c*(1. - d));
01063       G4double prob = f2x0/(f1x0+f2x0);
01064 
01065       G4double qprob = xmeanth/(prob*xmean1+(1.-prob)*xmean2);
01066 
01067       // sampling of costheta
01068       //G4cout << "c= " << c << " qprob= " << qprob << " eb1= " << eb1
01069       // << " c1= " << c1 << " b1= " << b1 << " bx= " << bx << " eb1= " << eb1
01070       //             << G4endl;
01071       if(G4UniformRand() < qprob)
01072       {
01073         G4double var = 0;
01074         if(G4UniformRand() < prob) {
01075           cth = 1.+log(ea+G4UniformRand()*eaa)*x;
01076         } else {
01077           var = (1.0 - d)*G4UniformRand();
01078           if(var < numlim*d) {
01079             var /= (d*c1); 
01080             cth = -1.0 + var*(1.0 - 0.5*var*c)*(2. + (c - xsi)*x);
01081           } else {
01082             cth = 1. + x*(c - xsi - c*pow(var + d, -1.0/c1));
01083             //b-b1*bx/exp(log(ebx+(eb1-ebx)*G4UniformRand())/c1) ;
01084           }
01085         }
01086         if(KineticEnergy > 5*GeV && cth < 0.9) {
01087           G4cout << "G4UrbanMscModel95::SampleCosineTheta: E(GeV)= " 
01088                  << KineticEnergy/GeV 
01089                  << " 1-cosT= " << 1 - cth
01090                  << " length(mm)= " << trueStepLength << " Zeff= " << Zeff 
01091                  << " tau= " << tau
01092                  << " prob= " << prob << " var= " << var << G4endl;
01093           G4cout << "  c= " << c << " qprob= " << qprob << " eb1= " << eb1
01094                  << " ebx= " << ebx
01095                  << " c1= " << c1 << " b= " << b << " b1= " << b1 
01096                  << " bx= " << bx << " d= " << d
01097                  << " ea= " << ea << " eaa= " << eaa << G4endl;
01098         }
01099       }
01100       else {
01101         cth = -1.+2.*G4UniformRand();
01102         if(KineticEnergy > 5*GeV) {
01103           G4cout << "G4UrbanMscModel95::SampleCosineTheta: E(GeV)= " 
01104                  << KineticEnergy/GeV 
01105                  << " length(mm)= " << trueStepLength << " Zeff= " << Zeff 
01106                  << " qprob= " << qprob << G4endl;
01107         }
01108       }
01109     }
01110   }
01111   return cth ;
01112 }
01113 
01114 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
01115 
01116 G4double G4UrbanMscModel95::SimpleScattering(G4double xmeanth,G4double x2meanth)
01117 {
01118   // 'large angle scattering'
01119   // 2 model functions with correct xmean and x2mean
01120   G4double a = (2.*xmeanth+9.*x2meanth-3.)/(2.*xmeanth-3.*x2meanth+1.);
01121   G4double prob = (a+2.)*xmeanth/a;
01122 
01123   // sampling
01124   G4double cth = 1.;
01125   if(G4UniformRand() < prob)
01126     cth = -1.+2.*exp(log(G4UniformRand())/(a+1.));
01127   else
01128     cth = -1.+2.*G4UniformRand();
01129   return cth;
01130 }
01131 
01132 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
01133 
01134 G4double G4UrbanMscModel95::SampleDisplacement()
01135 {
01136   G4double r = 0.0;
01137   if ((currentTau >= tausmall) && !insideskin) {
01138     G4double rmax = sqrt((tPathLength-zPathLength)*(tPathLength+zPathLength));
01139     r = rmax*exp(log(G4UniformRand())/3.);
01140   }
01141   return r;
01142 }
01143 
01144 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
01145 
01146 G4double G4UrbanMscModel95::LatCorrelation()
01147 {
01148   static const G4double kappa = 2.5;
01149   static const G4double kappami1 = kappa-1.;
01150 
01151   G4double latcorr = 0.;
01152   if((currentTau >= tausmall) && !insideskin)
01153   {
01154     if(currentTau < taulim)
01155       latcorr = lambdaeff*kappa*currentTau*currentTau*
01156                 (1.-(kappa+1.)*currentTau/3.)/3.;
01157     else
01158     {
01159       G4double etau = 0.;
01160       if(currentTau < taubig) etau = exp(-currentTau);
01161       latcorr = -kappa*currentTau;
01162       latcorr = exp(latcorr)/kappami1;
01163       latcorr += 1.-kappa*etau/kappami1 ;
01164       latcorr *= 2.*lambdaeff/3. ;
01165     }
01166   }
01167 
01168   return latcorr;
01169 }
01170 
01171 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......

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