G4StrawTubeXTRadiator.cc

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// $Id$
//

#include "G4StrawTubeXTRadiator.hh"
#include "G4PhysicalConstants.hh"
#include "G4SystemOfUnits.hh"
#include "Randomize.hh"
#include "G4Gamma.hh"

//
// Constructor, destructor

G4StrawTubeXTRadiator::G4StrawTubeXTRadiator(G4LogicalVolume *anEnvelope,
                     G4Material* foilMat,G4Material* gasMat, 
                                         G4double a, G4double b, G4Material* mediumMat,
                                         G4bool unishut,
                                         const G4String& processName) :
  G4VXTRenergyLoss(anEnvelope,foilMat,gasMat,a,b,1,processName)
{
  if(verboseLevel > 0)
    G4cout<<"Straw tube X-ray TR  radiator EM process is called"<<G4endl;

  if( unishut )
  {
    fAlphaPlate = 1./3.;
    fAlphaGas   = 12.4;
    if(verboseLevel > 0)
      G4cout<<"straw uniform shooting: "<<"fAlphaPlate = "
        <<fAlphaPlate<<" ; fAlphaGas = "<<fAlphaGas<<G4endl;

  }
  else
  {
    fAlphaPlate = 0.5;
    fAlphaGas   = 5.;
    if(verboseLevel > 0)
      G4cout<<"straw isotropical shooting: "<<"fAlphaPlate = "
        <<fAlphaPlate<<" ; fAlphaGas = "<<fAlphaGas<<G4endl;


  }
  // index of medium material

  fMatIndex3 = mediumMat->GetIndex();
  if(verboseLevel > 0)
    G4cout<<"medium material = "<<mediumMat->GetName()<<G4endl;

  // plasma energy squared for plate material

  fSigma3 = fPlasmaCof*mediumMat->GetElectronDensity();
  if(verboseLevel > 0)
    G4cout<<"medium plasma energy = "<<std::sqrt(fSigma3)/eV<<" eV"<<G4endl;

  // Compute cofs for preparation of linear photo absorption in external medium

  ComputeMediumPhotoAbsCof();

  // Build energy and angular integral spectra of X-ray TR photons from
  // a radiator

  // BuildTable();
}


G4StrawTubeXTRadiator::~G4StrawTubeXTRadiator()
{
}

//
// Approximation for radiator interference factor for the case of
// straw tube radiator. The plate (window, straw wall) and gas (inside straw) 
// gap thicknesses are  gamma distributed.
// The mean values of the plate and gas gap thicknesses 
// are supposed to be about XTR formation zone.

G4double 
G4StrawTubeXTRadiator::GetStackFactor( G4double energy, 
                                         G4double gamma, G4double varAngle )
{


  G4double result, L2, L3, M2, M3;
  
  L2 = GetPlateFormationZone(energy,gamma,varAngle);
  L3 = GetGasFormationZone(energy,gamma,varAngle);

  M2 = GetPlateLinearPhotoAbs(energy);
  M3 = GetGasLinearPhotoAbs(energy);

  G4complex C2(1.0 + 0.5*fPlateThick*M2/fAlphaPlate, fPlateThick/L2/fAlphaPlate); 
  G4complex C3(1.0 + 0.5*fGasThick*M3/fAlphaGas, fGasThick/L3/fAlphaGas); 

  G4complex H2 = std::pow(C2,-fAlphaPlate);  
  G4complex H3 = std::pow(C3,-fAlphaGas);
  G4complex H  = H2*H3;

  G4complex Z1 = GetMediumComplexFZ(energy,gamma,varAngle);
  G4complex Z2 = GetPlateComplexFZ(energy,gamma,varAngle);
  G4complex Z3 = GetGasComplexFZ(energy,gamma,varAngle);


  G4complex R  =    ( Z1 - Z2 )*( Z1 - Z2 )*( 1. - H2*H ) +
                    ( Z2 - Z3 )*( Z2 - Z3 )*( 1. - H3 )   + 
                 2.*( Z1 - Z2 )*( Z2 - Z3 )*H2*( 1. - H3 ) ;

  result       = 2.0*std::real(R)*(varAngle*energy/hbarc/hbarc);
  
  return      result;

}


//
// Calculates formation zone for external medium. Omega is energy !!!

G4double G4StrawTubeXTRadiator::GetMediumFormationZone( G4double omega ,
                                                G4double gamma ,
                                                G4double varAngle    ) 
{
  G4double cof, lambda;
  lambda = 1.0/gamma/gamma + varAngle + fSigma3/omega/omega;
  cof = 2.0*hbarc/omega/lambda ;
  return cof ;
}

//
// Calculates complex formation zone for external medium. Omega is energy !!!

G4complex G4StrawTubeXTRadiator::GetMediumComplexFZ( G4double omega ,
                                             G4double gamma ,
                                             G4double varAngle    ) 
{
  G4double cof, length,delta, real_v, image_v;

  length = 0.5*GetMediumFormationZone(omega,gamma,varAngle);
  delta  = length*GetMediumLinearPhotoAbs(omega);
  cof    = 1.0/(1.0 + delta*delta);

  real_v   = length*cof;
  image_v  = real_v*delta;

  G4complex zone(real_v,image_v); 
  return zone;
}

//
// Computes matrix of Sandia photo absorption cross section coefficients for
// medium material

void G4StrawTubeXTRadiator::ComputeMediumPhotoAbsCof() 
{
  const G4MaterialTable* theMaterialTable = G4Material::GetMaterialTable();
  const G4Material* mat = (*theMaterialTable)[fMatIndex3];
  fMediumPhotoAbsCof = mat->GetSandiaTable();
}

//
// Returns the value of linear photo absorption coefficient (in reciprocal 
// length) for medium for given energy of X-ray photon omega

G4double G4StrawTubeXTRadiator::GetMediumLinearPhotoAbs(G4double omega) 
{
  G4double omega2, omega3, omega4; 

  omega2 = omega*omega;
  omega3 = omega2*omega;
  omega4 = omega2*omega2;

  G4double* SandiaCof = fMediumPhotoAbsCof->GetSandiaCofForMaterial(omega);

  G4double cross = SandiaCof[0]/omega  + SandiaCof[1]/omega2 +
                   SandiaCof[2]/omega3 + SandiaCof[3]/omega4;
  return cross;
}

//
//