/home/cern/BDSIM_new/include/BDSQuadStepper.hh

/* BDSIM code.    Version 1.0
   Author: Grahame A. Blair, Royal Holloway, Univ. of London.
   Last modified 24.7.2002
   Copyright (c) 2002 by G.A.Blair.  ALL RIGHTS RESERVED. 
*/

//
// class BDSQuadStepper
//
// Class description:
// stepper for pure quadrupole magnetic field

// History:
// - Created. G.Blair 1/11/00

#ifndef BDSQUADSTEPPER_HH
#define BDSQUADSTEPPER_HH
#include "globals.hh"
#include "G4MagIntegratorStepper.hh"
#include "G4Mag_EqRhs.hh"
#include "G4ThreeVector.hh"
#include "G4Navigator.hh"

class BDSQuadStepper : public G4MagIntegratorStepper
{

public:  // with description

  BDSQuadStepper(G4Mag_EqRhs *EqRhs);

  ~BDSQuadStepper();

  void Stepper( const G4double y[],
                const G4double dydx[],
                const G4double h,
                G4double yout[],
                G4double yerr[]  );
  // The stepper for the Runge Kutta integration.
  // The stepsize is fixed, equal to h.
  // Integrates ODE starting values y[0 to 6]
  // Outputs yout[] and its estimated error yerr[].

  G4double DistChord()   const;
  // Estimate maximum distance of curved solution and chord ... 
 
  void SetBGrad(G4double aBGrad);
  G4double GetBGrad();

  void StepperName();

public: // without description
  
  G4int IntegratorOrder()const { return 2; }

protected:
  //  --- Methods used to implement all the derived classes -----

  void AdvanceHelix( const G4double  yIn[],
                     G4ThreeVector Bfld,
                     G4double  h,
                     G4double  yQuad[]);    // output 
  // A first order Step along a quad inside the field.

private:
  
  G4Mag_EqRhs*  fPtrMagEqOfMot;

  G4double itsBGrad;

  G4ThreeVector yInitial, yMidPoint, yFinal;
  // Data stored in order to find the chord.

  G4double itsDist;

};

inline  void BDSQuadStepper::SetBGrad(G4double aBGrad)
{itsBGrad=aBGrad;
}

inline G4double BDSQuadStepper::GetBGrad()
{return itsBGrad;}

inline void BDSQuadStepper::StepperName()
{G4cout<<"BDSQuadStepper"<<G4endl;}

#endif /* BDSQUADSTEPPER_HH */

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