G4QuadrupoleMagField.cc

Go to the documentation of this file.

//
// ********************************************************************
// * License and Disclaimer                                           *
// *                                                                  *
// * The  Geant4 software  is  copyright of the Copyright Holders  of *
// * the Geant4 Collaboration.  It is provided  under  the terms  and *
// * conditions of the Geant4 Software License,  included in the file *
// * LICENSE and available at  http://cern.ch/geant4/license .  These *
// * include a list of copyright holders.                             *
// *                                                                  *
// * Neither the authors of this software system, nor their employing *
// * institutes,nor the agencies providing financial support for this *
// * work  make  any representation or  warranty, express or implied, *
// * regarding  this  software system or assume any liability for its *
// * use.  Please see the license in the file  LICENSE  and URL above *
// * for the full disclaimer and the limitation of liability.         *
// *                                                                  *
// * This  code  implementation is the result of  the  scientific and *
// * technical work of the GEANT4 collaboration.                      *
// * By using,  copying,  modifying or  distributing the software (or *
// * any work based  on the software)  you  agree  to acknowledge its *
// * use  in  resulting  scientific  publications,  and indicate your *
// * acceptance of all terms of the Geant4 Software license.          *
// ********************************************************************
//
// G4QuadrupoleMagField implementation
//
// Author: Vladimir Grichine (CERN), 03.02.1997 - Created
// -------------------------------------------------------------------
 
#include "G4QuadrupoleMagField.hh"
#include "G4RotationMatrix.hh"
 
namespace
{
   G4RotationMatrix IdentityMatrix; 
}
 
G4QuadrupoleMagField::G4QuadrupoleMagField(G4double pGradient)
{
   fGradient = pGradient;
   fpMatrix  = &IdentityMatrix;
}
 
// -------------------------------------------------------------------
 
G4QuadrupoleMagField::G4QuadrupoleMagField(G4double pGradient,
                                           const G4ThreeVector& pOrigin,
                                           G4RotationMatrix* pMatrix)
{
   fGradient = pGradient ;
   fOrigin   = pOrigin ;
   fpMatrix  = pMatrix ;
}
 
// -------------------------------------------------------------------
 
G4Field* G4QuadrupoleMagField::Clone() const
{
   return new G4QuadrupoleMagField(fGradient, fOrigin, fpMatrix);
}
 
// -------------------------------------------------------------------
 
void G4QuadrupoleMagField::GetFieldValue( const G4double y[],         // [7]
                                                G4double B[]  ) const // [3]
{
  //  with displaced origin and rotation
 
  G4ThreeVector r_global = G4ThreeVector(y[0] - fOrigin.x(),
                                         y[1] - fOrigin.y(),
                                         y[2] - fOrigin.z());
  
  const G4ThreeVector r_local = (*fpMatrix) * r_global;
  const G4ThreeVector B_local( fGradient * r_local.y(),
                               fGradient * r_local.x(), 0);
  const G4ThreeVector B_global = fpMatrix->inverse() * B_local;
 
  B[0] = B_global.x();
  B[1] = B_global.y();
  B[2] = B_global.z();
}