G4PreCompoundNeutron.cc

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00025 //
00026 // $Id$
00027 //
00028 // -------------------------------------------------------------------
00029 //
00030 // GEANT4 Class file
00031 //
00032 //
00033 // File name:     G4PreCompoundNeutron
00034 //
00035 // Author:         V.Lara
00036 //
00037 // Modified:  
00038 // 21.08.2008 J. M. Quesada add choice of options  
00039 // 10.02.2009 J. M. Quesada set default opt3
00040 // 20.08.2010 V.Ivanchenko added G4Pow and G4PreCompoundParameters pointers
00041 //                         use int Z and A and cleanup
00042 // 
00043 
00044 #include "G4PreCompoundNeutron.hh"
00045 #include "G4SystemOfUnits.hh"
00046 #include "G4Neutron.hh"
00047 
00048 G4PreCompoundNeutron::G4PreCompoundNeutron()
00049   : G4PreCompoundNucleon(G4Neutron::Neutron(), &theNeutronCoulombBarrier)
00050 {
00051   ResidualA = GetRestA();
00052   ResidualZ = GetRestZ(); 
00053   theA = GetA();
00054   theZ = GetZ();
00055   ResidualAthrd = ResidualA13();
00056   FragmentAthrd = ResidualAthrd;
00057   FragmentA = theA + ResidualA;
00058 }
00059 
00060 G4PreCompoundNeutron::~G4PreCompoundNeutron()
00061 {}
00062 
00063 G4double G4PreCompoundNeutron::GetRj(G4int nParticles, G4int nCharged)
00064 {
00065   G4double rj = 0.0;
00066   if(nParticles > 0) { 
00067     rj = static_cast<G4double>(nParticles - nCharged)/
00068       static_cast<G4double>(nParticles);
00069   }
00070   return rj;
00071 }
00072 
00074 //J. M. Quesada (Dec 2007-June 2008): New inverse reaction cross sections 
00075 //OPT=0 Dostrovski's parameterization
00076 //OPT=1,2 Chatterjee's paramaterization 
00077 //OPT=3,4 Kalbach's parameterization 
00078 // 
00079 G4double G4PreCompoundNeutron::CrossSection(const  G4double K)
00080 {
00081   ResidualA = GetRestA();
00082   ResidualZ = GetRestZ(); 
00083   theA = GetA();
00084   theZ = GetZ();
00085   ResidualAthrd = ResidualA13();
00086   FragmentA = theA + ResidualA;
00087   FragmentAthrd = g4pow->Z13(FragmentA);
00088 
00089   if (OPTxs==0) { return GetOpt0( K); }
00090   else if( OPTxs==1 || OPTxs==2) { return GetOpt12( K); }
00091   else if (OPTxs==3 || OPTxs==4) { return GetOpt34( K); }
00092   else{
00093     std::ostringstream errOs;
00094     errOs << "BAD NEUTRON CROSS SECTION OPTION !!"  <<G4endl;
00095     throw G4HadronicException(__FILE__, __LINE__, errOs.str());
00096     return 0.;
00097   }
00098 }
00099 
00100 G4double G4PreCompoundNeutron::GetAlpha()
00101 {
00102   return 0.76+2.2/ResidualAthrd;
00103 }
00104 
00105 G4double G4PreCompoundNeutron::GetBeta() 
00106 {
00107   //   return (2.12/std::pow(GetRestA(),2.0/3.0)-0.05)*MeV/GetAlpha();
00108   return (2.12/(ResidualAthrd*ResidualAthrd)-0.05)*MeV/GetAlpha();
00109 }
00110 
00111 //********************* OPT=1,2 : Chatterjee's cross section ***************
00112 //(fitting to cross section from Bechetti & Greenles OM potential)
00113 
00114 G4double G4PreCompoundNeutron::GetOpt12(G4double K)
00115 {
00116   G4double Kc=K;
00117 
00118   // Pramana (Bechetti & Greenles) for neutrons is chosen 
00119 
00120   // JMQ  xsec is set constat above limit of validity
00121   if (K > 50*MeV) { Kc = 50*MeV; }
00122 
00123   G4double landa, landa0, landa1, mu, mm0, mu1,nu, nu0, nu1, nu2,xs;
00124 
00125   landa0 = 18.57;
00126   landa1 = -22.93;
00127   mm0 = 381.7;
00128   mu1 = 24.31;
00129   nu0 = 0.172;
00130   nu1 = -15.39;
00131   nu2 = 804.8;
00132   landa = landa0/ResidualAthrd + landa1;
00133   mu = mm0*ResidualAthrd + mu1*ResidualAthrd*ResidualAthrd;
00134   nu = nu0*ResidualAthrd*ResidualA + nu1*ResidualAthrd*ResidualAthrd + nu2 ;
00135   xs=landa*Kc + mu + nu/Kc;
00136   if (xs <= 0.0 ){
00137     std::ostringstream errOs;
00138     G4cout<<"WARNING:  NEGATIVE OPT=1 neutron cross section "<<G4endl;     
00139     errOs << "RESIDUAL: Ar=" << ResidualA << " Zr=" << ResidualZ <<G4endl;
00140     errOs <<"  xsec("<<Kc<<" MeV) ="<<xs <<G4endl;
00141     throw G4HadronicException(__FILE__, __LINE__, errOs.str());
00142               }
00143   return xs;
00144 }
00145 
00146 // *********** OPT=3,4 : Kalbach's cross sections (from PRECO code)*************
00147 G4double G4PreCompoundNeutron::GetOpt34(G4double K)
00148 {
00149   G4double landa, landa0, landa1, mu, mm0, mu1,nu, nu0, nu1, nu2;
00150   G4double p, p0;
00151   G4double flow,ec,ecsq,xnulam,etest(0.),ra(0.),a,signor(1.),sig; 
00152   G4double b,ecut,cut,ecut2,geom,elab;
00153 
00154   flow = 1.e-18;
00155 
00156   // PRECO xs for neutrons is choosen
00157   p0 = -312.;
00158   landa0 = 12.10;
00159   landa1=  -11.27;
00160   mm0 = 234.1;
00161   mu1 = 38.26;
00162   nu0 = 1.55;
00163   nu1 = -106.1;
00164   nu2 = 1280.8; 
00165 
00166   if (ResidualA < 40)  { signor =0.7 + ResidualA*0.0075; }
00167   if (ResidualA > 210) { signor = 1. + (ResidualA-210)/250.; }
00168   landa = landa0/ResidualAthrd + landa1;
00169   mu = mm0*ResidualAthrd + mu1*ResidualAthrd*ResidualAthrd;
00170   nu = nu0*ResidualAthrd*ResidualA + nu1*ResidualAthrd*ResidualAthrd + nu2;
00171 
00172   // JMQ very low energy behaviour corrected (problem  for A (apprx.)>60)
00173   if (nu < 0.) { nu=-nu; }
00174 
00175   ec = 0.5;
00176   ecsq = 0.25;
00177   p = p0;
00178   xnulam = 1.;
00179   etest = 32.;
00180   //          ** etest is the energy above which the rxn cross section is
00181   //          ** compared with the geometrical limit and the max taken.
00182   //          ** xnulam here is a dummy value to be used later.
00183 
00184   a = -2.*p*ec + landa - nu/ecsq;
00185   b = p*ecsq + mu + 2.*nu/ec;
00186   ecut = 0.;
00187   cut = a*a - 4.*p*b;
00188   if (cut > 0.) { ecut = std::sqrt(cut); }
00189   ecut = (ecut-a) / (p+p);
00190   ecut2 = ecut;
00191   if (cut < 0.) { ecut2 = ecut - 2.; }
00192   elab = K * FragmentA / G4double(ResidualA);
00193   sig = 0.;
00194   if (elab <= ec) { //start for E<Ec 
00195     if (elab > ecut2) { sig = (p*elab*elab+a*elab+b) * signor; } 
00196   }              //end for E<Ec
00197   else {           //start for  E>Ec
00198     sig = (landa*elab+mu+nu/elab) * signor;
00199     geom = 0.;
00200     if (xnulam < flow || elab < etest) { return sig; }
00201     geom = std::sqrt(theA*K);
00202     geom = 1.23*ResidualAthrd + ra + 4.573/geom;
00203     geom = 31.416 * geom * geom;
00204     sig = std::max(geom,sig);
00205 
00206   }
00207   return sig;
00208 }

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