G4QuadrupoleMagField.cc

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// $Id: G4QuadrupoleMagField.cc 68055 2013-03-13 14:43:28Z gcosmo $
//
// -------------------------------------------------------------------

#include "G4QuadrupoleMagField.hh"
#include "G4RotationMatrix.hh"

static G4RotationMatrix IdentityMatrix; 

G4QuadrupoleMagField::G4QuadrupoleMagField(G4double pGradient)
{
   fGradient = pGradient ;
   fOrigin   = G4ThreeVector( 0.0, 0.0, 0.0) ;
   fpMatrix  = &IdentityMatrix;
}



G4QuadrupoleMagField::G4QuadrupoleMagField(G4double pGradient,
                                           G4ThreeVector pOrigin,
                                           G4RotationMatrix* pMatrix)
{
   fGradient    = pGradient ;
   fOrigin      = pOrigin ;
   fpMatrix     = pMatrix ;
}

G4QuadrupoleMagField* G4QuadrupoleMagField::Clone() const
{
    //TODO: Can the fpMatrix be shared??
    return new G4QuadrupoleMagField(this->fGradient,
                                    this->fOrigin,
                                    this->fpMatrix);
}


G4QuadrupoleMagField::~G4QuadrupoleMagField()
{
}

//  Allow displaced origin and rotation 
//  Extensions by Björn Riese (GSI)

void G4QuadrupoleMagField::GetFieldValue( const G4double y[7],
                                                G4double B[3]  ) const  
{
   G4ThreeVector r_global = G4ThreeVector(
        y[0] - fOrigin.x(), 
        y[1] - fOrigin.y(), 
        y[2] - fOrigin.z());

   G4ThreeVector r_local = G4ThreeVector(
           fpMatrix->colX() * r_global,
           fpMatrix->colY() * r_global,
           fpMatrix->colZ() * r_global);

   G4ThreeVector B_local = G4ThreeVector(
           fGradient * r_local.y(),
        fGradient * r_local.x(),
        0);

   G4ThreeVector B_global = G4ThreeVector(
           fpMatrix->inverse().rowX() * B_local,
           fpMatrix->inverse().rowY() * B_local,
           fpMatrix->inverse().rowZ() * B_local);

   B[0] = B_global.x() ;
   B[1] = B_global.y() ;
   B[2] = B_global.z() ;
}