G4XTRGammaRadModel.cc

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#include "G4XTRGammaRadModel.hh"
 
////////////////////////////////////////////////////////////////////////////
// Constructor, destructor
G4XTRGammaRadModel::G4XTRGammaRadModel(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)
{
  G4cout << "Gamma distributed X-ray TR radiator model is called" << G4endl;
 
  // Build energy and angular integral spectra of X-ray TR photons from
  // a radiator
  fAlphaPlate = alphaPlate;
  fAlphaGas   = alphaGas;
  G4cout << "fAlphaPlate = " << fAlphaPlate << " ; fAlphaGas = " << fAlphaGas
         << G4endl;
  fExitFlux = true;
}
 
///////////////////////////////////////////////////////////////////////////
G4XTRGammaRadModel::~G4XTRGammaRadModel() = default;
 
void G4XTRGammaRadModel::ProcessDescription(std::ostream& out) const
{
  out << "Rough model describing X-ray transition radiation. Thicknesses of "
         "plates\n"
         "and gas gaps are distributed according to gamma distributions.\n";
}
 
///////////////////////////////////////////////////////////////////////////
// Rough approximation for radiator interference factor for the case of
// fully GamDistr radiator. The plate and gas gap thicknesses are distributed
// according to exponent. The mean values of the plate and gas gap thicknesses
// are supposed to be about XTR formation zones but much less than
// mean absorption length of XTR photons in coresponding material.
G4double G4XTRGammaRadModel::GetStackFactor(G4double energy, G4double gamma,
                                            G4double varAngle)
{
  G4double result, Qa, Qb, Q, Za, Zb, Ma, Mb;
 
  Za = GetPlateFormationZone(energy, gamma, varAngle);
  Zb = GetGasFormationZone(energy, gamma, varAngle);
 
  Ma = GetPlateLinearPhotoAbs(energy);
  Mb = GetGasLinearPhotoAbs(energy);
 
  Qa = (1.0 + fPlateThick * Ma / fAlphaPlate);
  Qa = std::pow(Qa, -fAlphaPlate);
  Qb = (1.0 + fGasThick * Mb / fAlphaGas);
  Qb = std::pow(Qb, -fAlphaGas);
  Q  = Qa * Qb;
 
  G4complex Ca(1.0 + 0.5 * fPlateThick * Ma / fAlphaPlate,
               fPlateThick / Za / fAlphaPlate);
  G4complex Cb(1.0 + 0.5 * fGasThick * Mb / fAlphaGas,
               fGasThick / Zb / fAlphaGas);
 
  G4complex Ha = std::pow(Ca, -fAlphaPlate);
  G4complex Hb = std::pow(Cb, -fAlphaGas);
  G4complex H  = Ha * Hb;
 
  G4complex F1 = (0.5 * (1 + Qa) * (1.0 + H) - Ha - Qa * Hb) / (1.0 - H);
 
  G4complex F2 = (1.0 - Ha) * (Qa - Ha) * Hb / (1.0 - H) / (Q - H);
 
  F2 *= std::pow(Q, G4double(fPlateNumber)) - std::pow(H, fPlateNumber);
 
  result = (1. - std::pow(Q, G4double(fPlateNumber))) / (1. - Q);
 
  G4complex stack = result * F1;
  stack += F2;
  stack *= 2.0 * OneInterfaceXTRdEdx(energy, gamma, varAngle);
 
  result = std::real(stack);
 
  return result;
}