G4GaussXTRadiator.cc

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//
// 19.09.21 V. Grichine, first version
//
 
#include "G4GaussXTRadiator.hh"
 
#include "G4PhysicalConstants.hh"
 
////////////////////////////////////////////////////////////////////////////
// Constructor, destructor
 
G4GaussXTRadiator::G4GaussXTRadiator(
  G4LogicalVolume* anEnvelope,   G4double alphaPlate, G4double alphaGas, G4Material* foilMat, G4Material* gasMat,
  G4double a, G4double b, G4int n, const G4String& processName)
  : G4VXTRenergyLoss(anEnvelope, foilMat, gasMat, a, b, n, processName)
{
  if(verboseLevel > 0)
    G4cout << "Gauss X-ray TR  radiator EM process is called"
           << G4endl;
 
  fAlphaPlate = alphaPlate;
  fAlphaGas   = alphaGas; //  1000; // 
}
 
///////////////////////////////////////////////////////////////////////////
G4GaussXTRadiator::~G4GaussXTRadiator() = default;
 
///////////////////////////////////////////////////////////////////////////
void G4GaussXTRadiator::ProcessDescription(std::ostream& out) const
{
  out << "Simulation of forward X-ray transition radiation generated by\n"
         "relativistic charged particles crossing the interface between\n"
         "two materials.\n";
}
 
///////////////////////////////////////////////////////////////////////////
//
// The Fabian-Strujinsky (FS) algorithm for integration over XTR angle, 
// resolution is about 0.1-0.5 mrad
 
G4double G4GaussXTRadiator::SpectralXTRdEdx(G4double energy)
{
  G4double result, sum = 0., tmp, cof1, cof2, cofMin, cofPHC, theta2, theta2k;
  G4int k, kMax, kMin;
 
  cofPHC = 4. * pi * hbarc;
  tmp    = (fSigma1 - fSigma2) / cofPHC / energy;
  cof1   = fPlateThick * tmp;
  cof2   = fGasThick * tmp;
 
  cofMin = energy * (fPlateThick + fGasThick) / fGamma / fGamma;
  cofMin += (fPlateThick * fSigma1 + fGasThick * fSigma2) / energy;
  cofMin /= cofPHC;
 
  theta2 = cofPHC / (energy * (fPlateThick + fGasThick));
 
  kMin = G4int(cofMin);
  if(cofMin > kMin)
    kMin++;
 
  kMax = kMin + fKrange;
 
  if(verboseLevel > 2)
  {
    G4cout << cof1 << "     " << cof2 << "        " << cofMin << G4endl;
    G4cout << "kMin = " << kMin << ";    kMax = " << kMax << G4endl;
  }
  for(k = kMin; k <= kMax; ++k)
  {
    tmp    = pi * fPlateThick * (k + cof2) / (fPlateThick + fGasThick);
    result = (k - cof1) * (k - cof1) * (k + cof2) * (k + cof2);
    if(k == kMin && kMin == G4int(cofMin))
    {
      sum +=
        0.5 * std::sin(tmp) * std::sin(tmp) * std::abs(k - cofMin) / result;
    }
    else
    {
      sum += std::sin(tmp) * std::sin(tmp) * std::abs(k - cofMin) / result;
    }
    theta2k = std::sqrt(theta2 * std::abs(k - cofMin));
 
    if(verboseLevel > 2)
    {
      G4cout << k << "   " << theta2k << "     "
             << std::sin(tmp) * std::sin(tmp) * std::abs(k - cofMin) / result
             << "      " << sum << G4endl;
    }
  }
  result = 4. * (cof1 + cof2) * (cof1 + cof2) * sum / energy;
  result *= fPlateNumber;
 
  return result;
}
 
///////////////////////////////////////////////////////////////////////////
//
// Approximation for radiator interference factor for the case of
// Gauss-distributed regular radiator. The plate and gas gap thicknesses are Gauss distributed with RMS
// sa and sb for plate and gas, respectively.
// The mean values of the plate and gas gap thicknesses
// are supposed to be about XTR formation zones.
 
 
G4double G4GaussXTRadiator::GetStackFactor(G4double energy,
                                                    G4double gamma,
                                                    G4double varAngle)
{
  G4double result(0.);
  G4double sa = fPlateThick/fAlphaPlate;
  G4double sb = fGasThick/fAlphaGas;
  G4double nn = G4double(fPlateNumber);
  
  G4complex med( 0., 1.);
  G4complex Z1   = GetPlateComplexFZ( energy, gamma, varAngle);
  G4complex order1 = -0.5*med*fPlateThick/Z1 - 0.125*sa*sa/Z1/Z1;
 
  G4complex Z2   = GetGasComplexFZ( energy, gamma, varAngle);
  G4complex order2 = -0.5*med*fGasThick/Z2 - 0.125*sb*sb/Z2/Z2;
 
  G4complex ordernn = ( order1 + order2 )*nn;
 
  G4complex Ha = exp( order1 );
  G4complex Hb = exp( order2 );
  G4complex H  = Ha * Hb;
  G4complex Hn = exp( ordernn );
  
  G4complex F1 = ( 1.0 - Ha ) * ( 1.0 - Hb ) * nn / ( 1. - H );
  
  G4complex F2 = ( 1.0 - Ha ) * ( 1.0 - Ha ) * Hb * ( 1. - Hn ) / ( 1. - H ) / ( 1. - H );
  
  G4complex R = (F1 + F2) * OneInterfaceXTRdEdx(energy, gamma, varAngle);
  
  result      = 2.0 * std::real(R);
  
  return result;
}