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// G4QuadrupoleMagField
//
// Class description:
//
// Class for creation of quadrupole magnetic field
//   fGradient - is the gradient value for quadrupole magnetic lense.
// Then the magnetic field components are:
//   Bx = B[0] = fGradient*X ,
//   By = B[1] = fGradient*Y ,
//   Bz = B[2] = 0 .
// Here X,Y,Z are the coordinates of a space point of interest.

// Author: Vladimir Grichine (CERN), 03.02.1997 - Created
// -------------------------------------------------------------------
#ifndef G4QUADRUPOLEMAGFIELD_HH
#define G4QUADRUPOLEMAGFIELD_HH

#include "G4MagneticField.hh"
#include "G4ThreeVector.hh"
#include "G4RotationMatrix.hh"

/**
 * @brief G4QuadrupoleMagField allows for the creation of quadrupole magnetic
 * field, given the gradient value for quadrupole magnetic lense.
 */

class G4QuadrupoleMagField : public G4MagneticField
{
  public:

    /**
     * Constructor for G4QuadrupoleMagField.
     *  @param[in] pGradient Field gradient value.
     */
    G4QuadrupoleMagField(G4double pGradient);

    /**
     * Constructor for G4QuadrupoleMagField.
     *  @param[in] pGradient Field gradient value.
     *  @param[in] pOrigin Origin position.
     *  @param[in] pMatrix Rotation matrix.
     */
    G4QuadrupoleMagField(G4double pGradient, 
                         const G4ThreeVector& pOrigin, 
                         G4RotationMatrix* pMatrix);

    /**
     * Default Destructor.
     */
    ~G4QuadrupoleMagField() override = default;

    /**
     * Returns the field value on the given position 'yTrack'.
     *  @param[in] yTrack Time position array.
     *  @param[out] B The returned field array.
     */
    void GetFieldValue(const G4double yTrack[], G4double B[]) const override;

    /**
     * Returns a pointer to a new allocated clone of this object.
     */
    G4Field* Clone() const override;

  private:

    G4double          fGradient = 0.0;
    G4ThreeVector     fOrigin = G4ThreeVector(0.0, 0.0, 0.0);
    G4RotationMatrix* fpMatrix = nullptr;
};

#endif