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//
// Class description:
//
// Sextupole magnetic field
//   fGradient - is the gradient value for a sextupole magnet
//   the magnetic field components are:
//   Bx = B[0] = fGradient*X*Y,
//   By = B[1] = fGradient*(X*X-Y*Y)/2,
//   Bz = B[2] = 0

// Author: Helmut Burkhardt (CERN), 23.10.2019
// -------------------------------------------------------------------
#ifndef G4SEXTUPOLEMAGFIELD_HH
#define G4SEXTUPOLEMAGFIELD_HH

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

/**
 * @brief G4SextupoleMagField is a class for defining a sextupole
 * magnetic field.
 */

class G4SextupoleMagField : public G4MagneticField
{
  public:

    /**
     * Constructor for G4SextupoleMagField.
     *  @param[in] pGradient Field gradient value.
     */
    G4SextupoleMagField(G4double pGradient);

    /**
     * Constructor for G4QuadrupoleMagField.
     *  @param[in] pGradient Field gradient value.
     *  @param[in] pOrigin Origin position.
     *  @param[in] pMatrix Rotation matrix.
     */
    G4SextupoleMagField(G4double pGradient,
                        const G4ThreeVector& pOrigin,
                        G4RotationMatrix* pMatrix);

    /**
     * Default Destructor.
     */
    ~G4SextupoleMagField() 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