G4PreCompoundAlpha.cc

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// $Id: G4PreCompoundAlpha.cc 82765 2014-07-08 14:25:39Z gcosmo $
//
// -------------------------------------------------------------------
//
// GEANT4 Class file
//
//
// File name:     G4PreCompoundAlpha
//
// Author:         V.Lara
//
// Modified:  
// 21.08.2008 J. M. Quesada add choice of options  
// 20.08.2010 V.Ivanchenko added G4Pow and G4PreCompoundParameters pointers
//                         use int Z and A and cleanup
// 05.07.2013 J.M. Quesada FactorialFactor fixed
//

#include "G4PreCompoundAlpha.hh"
#include "G4SystemOfUnits.hh"
#include "G4Alpha.hh"

G4PreCompoundAlpha::G4PreCompoundAlpha()
  : G4PreCompoundIon(G4Alpha::Alpha(), &theAlphaCoulombBarrier)
{
  ResidualA = GetRestA();
  ResidualZ = GetRestZ(); 
  theA = GetA();
  theZ = GetZ();
  ResidualAthrd = ResidualA13();
  FragmentAthrd = ResidualAthrd;
  FragmentA = theA + ResidualA;
}

G4PreCompoundAlpha::~G4PreCompoundAlpha()
{}

G4double G4PreCompoundAlpha::FactorialFactor(G4int N, G4int P)
{
  return G4double((N-4)*(P-3)*(N-3)*(P-2))*G4double((N-2)*(P-1)*(N-1)*P)/144.0;
}
  
G4double G4PreCompoundAlpha::CoalescenceFactor(G4int A)
{
  return 4096.0/G4double(A*A*A);  
}    

G4double G4PreCompoundAlpha::GetRj(G4int nParticles, G4int nCharged)
{
  G4double rj = 0.0;
  if(nCharged >=2 && (nParticles-nCharged) >=2 ) {
    G4double denominator = 
      G4double(nParticles*(nParticles-1)*(nParticles-2)*(nParticles-3));
    rj = 6.0*nCharged*(nCharged-1)*(nParticles-nCharged)*(nParticles-nCharged-1)
      /denominator;  
  }
  return rj;
}

//J. M. Quesada (Dec 2007-June 2008): New inverse reaction cross sections 
//OPT=0 Dostrovski's parameterization
//OPT=1,2 Chatterjee's paramaterization 
//OPT=3,4 Kalbach's parameterization 
// 
G4double G4PreCompoundAlpha::CrossSection(G4double K)
{
  ResidualA = GetRestA();
  ResidualZ = GetRestZ(); 
  theA = GetA();
  theZ = GetZ();
  ResidualAthrd = ResidualA13();
  FragmentA = theA + ResidualA;
  FragmentAthrd = g4pow->Z13(FragmentA);

  if (OPTxs==0) { return GetOpt0( K); }
  else if( OPTxs==1 || OPTxs==2) { return GetOpt12( K); }
  else if (OPTxs==3 || OPTxs==4) { return GetOpt34( K); }
  else{
    std::ostringstream errOs;
    errOs << "BAD Alpha CROSS SECTION OPTION !!"  <<G4endl;
    throw G4HadronicException(__FILE__, __LINE__, errOs.str());
    return 0.;
  }
}

G4double G4PreCompoundAlpha::GetAlpha()
{
  G4double C = 0.0;
  G4int aZ = theZ + ResidualZ;
  if (aZ <= 30) 
    {
      C = 0.10;
    } 
  else if (aZ <= 50) 
    {
      C = 0.1 - (aZ-30)*0.001;
    } 
  else if (aZ < 70) 
    {
      C = 0.08 - (aZ-50)*0.001;
    }
  else 
    {
      C = 0.06;
    }
  return 1.0+C;
}

//
//********************* OPT=1,2 : Chatterjee's cross section ********************
//(fitting to cross section from Bechetti & Greenles OM potential)

G4double G4PreCompoundAlpha::GetOpt12(G4double K)
{
  G4double Kc=K;

  // JMQ xsec is set constant above limit of validity
  if (K > 50*MeV) { Kc = 50*MeV; }

  G4double landa ,mu ,nu ,p , Ec,q,r,ji,xs;

  G4double     p0 = 10.95;
  G4double     p1 = -85.2;
  G4double     p2 = 1146.;
  G4double     landa0 = 0.0643;
  G4double     landa1 = -13.96;
  G4double     mm0 = 781.2;
  G4double     mu1 = 0.29;
  G4double     nu0 = -304.7;
  G4double     nu1 = -470.0;
  G4double     nu2 = -8.580;   
  G4double     delta=1.2;          

  Ec = 1.44*theZ*ResidualZ/(1.5*ResidualAthrd+delta);
  p = p0 + p1/Ec + p2/(Ec*Ec);
  landa = landa0*ResidualA + landa1;
  G4double resmu1 = g4pow->powZ(ResidualA,mu1); 
  mu = mm0*resmu1;
  nu = resmu1*(nu0 + nu1*Ec + nu2*(Ec*Ec));
  q = landa - nu/(Ec*Ec) - 2*p*Ec;
  r = mu + 2*nu/Ec + p*(Ec*Ec);

  ji=std::max(Kc,Ec);
  if(Kc < Ec) { xs = p*Kc*Kc + q*Kc + r;}
  else {xs = p*(Kc - ji)*(Kc - ji) + landa*Kc + mu + nu*(2 - Kc/ji)/ji ;}
  
  if (xs <0.0) {xs=0.0;}
              
  return xs;
}

// *********** OPT=3,4 : Kalbach's cross sections (from PRECO code)*************
G4double G4PreCompoundAlpha::GetOpt34(G4double K)
// c     ** alpha from huizenga and igo
{
  G4double landa, mu, nu, p , signor(1.),sig;
  G4double ec,ecsq,xnulam,etest(0.),a; 
  G4double b,ecut,cut,ecut2,geom,elab;

  G4double     flow = 1.e-18;
  G4double     spill= 1.e+18;

  G4double     p0 = 10.95;
  G4double     p1 = -85.2;
  G4double     p2 = 1146.;
  G4double     landa0 = 0.0643;
  G4double     landa1 = -13.96;
  G4double     mm0 = 781.2;
  G4double     mu1 = 0.29;
  G4double     nu0 = -304.7;
  G4double     nu1 = -470.0;
  G4double     nu2 = -8.580;        
  
  G4double      ra=1.20;
        
  //JMQ 13/02/09 increase of reduced radius to lower the barrier
  // ec = 1.44 * theZ * ResidualZ / (1.5*ResidualAthrd+ra);
  ec = 1.44 * theZ * ResidualZ / (1.7*ResidualAthrd+ra);
  ecsq = ec * ec;
  p = p0 + p1/ec + p2/ecsq;
  landa = landa0*ResidualA + landa1;
  a = g4pow->powZ(ResidualA,mu1);
  mu = mm0 * a;
  nu = a* (nu0+nu1*ec+nu2*ecsq);  
  xnulam = nu / landa;
  if (xnulam > spill) { xnulam=0.; }
  if (xnulam >= flow) { etest = 1.2 *std::sqrt(xnulam); }

  a = -2.*p*ec + landa - nu/ecsq;
  b = p*ecsq + mu + 2.*nu/ec;
  ecut = 0.;
  cut = a*a - 4.*p*b;
  if (cut > 0.) { ecut = std::sqrt(cut); }
  ecut = (ecut-a) / (p+p);
  ecut2 = ecut;
  //JMQ 290310 for avoiding unphysical increase below minimum (at ecut)
  // ecut<0 means that there is no cut with energy axis, i.e. xs is set 
  // to 0 bellow minimum
  //  if (cut < 0.) ecut2 = ecut - 2.;
  if (cut < 0.) { ecut2 = ecut; }
  elab = K * FragmentA / G4double(ResidualA);
  sig = 0.;
  
  if (elab <= ec) { //start for E<Ec
    if (elab > ecut2) { sig = (p*elab*elab+a*elab+b) * signor; }
  }           //end for E<Ec
  else {           //start for E>Ec
    sig = (landa*elab+mu+nu/elab) * signor;
    geom = 0.;
    if (xnulam < flow || elab < etest) { return sig; }
    geom = std::sqrt(theA*K);
    geom = 1.23*ResidualAthrd + ra + 4.573/geom;
    geom = 31.416 * geom * geom;
    sig = std::max(geom,sig);
  }           //end for E>Ec
  return sig;
}