G4MagHelicalStepper.hh

Go to the documentation of this file. Or view the newest version in sPHENIX GitHub for file G4MagHelicalStepper.hh

//
// ********************************************************************
// * 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.          *
// ********************************************************************
//
// G4MagHelicalStepper
//
// Class description:
//
// Abstract base class for integrator of particle's equation of motion,
// used in tracking in space dependent magnetic field
//
// It is used for a set of steppers which use the helix as a sort of
// 'first order' solution.
//   - Most obtain an error by breaking up the step in two
//   - G4ExactHelicalStepper does not provide an error estimate

// Created: J.Apostolakis, CERN - 05.11.1998
// --------------------------------------------------------------------
#ifndef G4MAGHELICALSTEPPER_HH
#define G4MAGHELICALSTEPPER_HH

#include <CLHEP/Units/PhysicalConstants.h>

#include "G4Types.hh"
#include "G4MagIntegratorStepper.hh"
#include "G4Mag_EqRhs.hh"
#include "G4ThreeVector.hh"

class G4MagHelicalStepper : public G4MagIntegratorStepper
{
  public:  // with description

    G4MagHelicalStepper(G4Mag_EqRhs *EqRhs);
    virtual ~G4MagHelicalStepper();
  
    G4MagHelicalStepper(const G4MagHelicalStepper&) = delete;
    G4MagHelicalStepper& operator=(const G4MagHelicalStepper&) = delete;
 
    virtual void Stepper( const G4double y[], // VIRTUAL for ExactHelix
                          const G4double dydx[],
                                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[].
  
    virtual  void DumbStepper( const G4double y[],
                                     G4ThreeVector Bfld,
                                     G4double h,
                                     G4double yout[] ) = 0;
      // Performs a 'dump' Step without error calculation.
  
    G4double DistChord()const ;
      // Estimate maximum distance of curved solution and chord ... 

  protected:  // with description

    inline void LinearStep( const G4double yIn[],
                                  G4double h,
                                  G4double yHelix[]) const;
      // A linear Step in regions without magnetic field.

    void AdvanceHelix( const G4double yIn[],
                             G4ThreeVector Bfld,
                             G4double h,
                             G4double yHelix[], G4double yHelix2[] = 0);
      // A first order Step along a helix inside the field.

    inline void MagFieldEvaluate( const G4double y[], G4ThreeVector& Bfield );
      // Evaluate the field at a certain point.
  
    inline G4double GetInverseCurve( const G4double Momentum,
                                     const G4double Bmag );
      // Evaluate Inverse of Curvature of Track

    // Store and use the parameters of track : 
    // radius of curve, Stepping angle, Radius of projected helix

    inline void SetAngCurve(const G4double Ang);
    inline G4double GetAngCurve()const;

    inline void SetCurve(const G4double Curve);
    inline G4double GetCurve()const;

    inline void SetRadHelix(const G4double Rad);
    inline G4double GetRadHelix()const;

  private:

    static const G4double fUnitConstant;
      // As in G4Mag_EqRhs.hh/cc where it is not used.

    G4Mag_EqRhs* fPtrMagEqOfMot = nullptr;
 
    // Data stored in order to find the chord
    //
    G4double fAngCurve = 0.0;
    G4double frCurve = 0.0;
    G4double frHelix = 0.0;
    G4ThreeVector yInitial, yMidPoint, yFinal;
};

#include  "G4MagHelicalStepper.icc"

#endif