/scratch0/jsnuveri/BDSIM/BDSIMgit/bdsim/include/BDSDecStepper.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 BDSDecStepper
//
// Class description:
// stepper for pure decapole magnetic field

// History:
//

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

class BDSDecStepper : public G4MagIntegratorStepper
{

public:  // with description

  BDSDecStepper(G4Mag_EqRhs *EqRhs);

  ~BDSDecStepper();

  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 SetBQuadPrime(G4double aBQuadPrime);
  G4double GetBQuadPrime();

  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  yDec[]);    // output 
  // A first order Step along a dec inside the field.

private:
  
  G4Mag_EqRhs*  fPtrMagEqOfMot;

  G4double itsBQuadPrime;

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

  G4double itsDist;

};

inline  void BDSDecStepper::SetBQuadPrime(G4double aBQuadPrime)
{itsBQuadPrime=aBQuadPrime;
}

inline G4double BDSDecStepper::GetBQuadPrime()
{return itsBQuadPrime;}

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

#endif /* BDSDECSTEPPER_HH */

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