#include <G4MagHelicalStepper.hh>

Inheritance diagram for G4MagHelicalStepper:

Public Member Functions
	G4MagHelicalStepper (G4Mag_EqRhs *EqRhs)

virtual	~G4MagHelicalStepper ()

virtual void	Stepper (const G4double y[], const G4double dydx[], G4double h, G4double yout[], G4double yerr[])

virtual void	DumbStepper (const G4double y[], G4ThreeVector Bfld, G4double h, G4double yout[])=0

G4double	DistChord () const

Public Member Functions inherited from G4MagIntegratorStepper
	G4MagIntegratorStepper (G4EquationOfMotion *Equation, G4int numIntegrationVariables, G4int numStateVariables=12)

virtual	~G4MagIntegratorStepper ()

virtual void	ComputeRightHandSide (const G4double y[], G4double dydx[])

void	NormaliseTangentVector (G4double vec[6])

void	NormalisePolarizationVector (G4double vec[12])

void	RightHandSide (const double y[], double dydx[])

G4int	GetNumberOfVariables () const

G4int	GetNumberOfStateVariables () const

virtual G4int	IntegratorOrder () const =0

G4EquationOfMotion *	GetEquationOfMotion ()

void	SetEquationOfMotion (G4EquationOfMotion *newEquation)

Protected Member Functions
void	LinearStep (const G4double yIn[], G4double h, G4double yHelix[]) const

void	AdvanceHelix (const G4double yIn[], G4ThreeVector Bfld, G4double h, G4double yHelix[], G4double yHelix2[]=0)

void	MagFieldEvaluate (const G4double y[], G4ThreeVector &Bfield)

G4double	GetInverseCurve (const G4double Momentum, const G4double Bmag)

void	SetAngCurve (const G4double Ang)

G4double	GetAngCurve () const

void	SetCurve (const G4double Curve)

G4double	GetCurve () const

void	SetRadHelix (const G4double Rad)

G4double	GetRadHelix () const

Detailed Description

Definition at line 53 of file G4MagHelicalStepper.hh.

Constructor & Destructor Documentation

G4MagHelicalStepper::G4MagHelicalStepper ( G4Mag_EqRhs * EqRhs )

Definition at line 47 of file G4MagHelicalStepper.cc.

    : G4MagIntegratorStepper(EqRhs, 6), // integrate over 6 variables only !!
                                        // position & velocity
      fPtrMagEqOfMot(EqRhs), fAngCurve(0.), frCurve(0.), frHelix(0.)
 {
 }

G4MagHelicalStepper::~G4MagHelicalStepper ( )

virtual

Definition at line 54 of file G4MagHelicalStepper.cc.

55 {

56 }

Member Function Documentation

void G4MagHelicalStepper::AdvanceHelix	(	const G4double	yIn[],
		G4ThreeVector	Bfld,
		G4double	h,
		G4double	yHelix[],
		G4double	yHelix2[] = `0`
	)

protected

Definition at line 59 of file G4MagHelicalStepper.cc.

References python.hepunit::c_light, CLHEP::Hep3Vector::cross(), CLHEP::Hep3Vector::dot(), python.hepunit::eplus, G4Mag_EqRhs::FCof(), GetInverseCurve(), LinearStep(), CLHEP::Hep3Vector::mag(), SetAngCurve(), SetCurve(), SetRadHelix(), CLHEP::Hep3Vector::x(), CLHEP::Hep3Vector::y(), and CLHEP::Hep3Vector::z().

Referenced by G4HelixSimpleRunge::DumbStepper(), G4HelixHeum::DumbStepper(), G4HelixImplicitEuler::DumbStepper(), G4HelixExplicitEuler::DumbStepper(), G4ExactHelixStepper::DumbStepper(), G4HelixMixedStepper::DumbStepper(), G4HelixExplicitEuler::Stepper(), G4ExactHelixStepper::Stepper(), and G4HelixMixedStepper::Stepper().

 {
   // const G4int    nvar = 6;
  
   // OLD  const G4double approc_limit = 0.05;
   // OLD  approc_limit = 0.05 gives max.error=x^5/5!=(0.05)^5/5!=2.6*e-9
   // NEW  approc_limit = 0.005 gives max.error=x^5/5!=2.6*e-14
 
   const G4double approc_limit = 0.005;
   G4ThreeVector  Bnorm, B_x_P, vperp, vpar;
 
   G4double B_d_P;
   G4double B_v_P;
   G4double Theta;
   G4double R_1;
   G4double R_Helix;
   G4double CosT2, SinT2, CosT, SinT;
   G4ThreeVector positionMove, endTangent;
 
   G4double Bmag = Bfld.mag();
   const G4double *pIn = yIn+3;
   G4ThreeVector initVelocity= G4ThreeVector( pIn[0], pIn[1], pIn[2]);
   G4double      velocityVal = initVelocity.mag();
   G4ThreeVector initTangent = (1.0/velocityVal) * initVelocity;
   
   R_1=GetInverseCurve(velocityVal,Bmag);
 
   // for too small magnetic fields there is no curvature
   // (include momentum here) FIXME
 
   if( (std::fabs(R_1) < 1e-10)||(Bmag<1e-12) )
   {
     LinearStep( yIn, h, yHelix );
 
     // Store and/or calculate parameters for chord distance
 
     SetAngCurve(1.);     
     SetCurve(h);
     SetRadHelix(0.);
   }
   else
   {
     Bnorm = (1.0/Bmag)*Bfld;
 
     // calculate the direction of the force
     
     B_x_P = Bnorm.cross(initTangent);
 
     // parallel and perp vectors
 
     B_d_P = Bnorm.dot(initTangent); // this is the fraction of P parallel to B
 
     vpar = B_d_P * Bnorm;       // the component parallel      to B
     vperp= initTangent - vpar;  // the component perpendicular to B
     
     B_v_P  = std::sqrt( 1 - B_d_P * B_d_P); // Fraction of P perp to B
 
     // calculate  the stepping angle
   
     Theta   = R_1 * h; // * B_v_P;
 
     // Trigonometrix
       
     if( std::fabs(Theta) > approc_limit )
     {
        SinT     = std::sin(Theta);
        CosT     = std::cos(Theta);
     }
     else
     {
       G4double Theta2 = Theta*Theta;
       G4double Theta3 = Theta2 * Theta;
       G4double Theta4 = Theta2 * Theta2;
       SinT     = Theta - 1.0/6.0 * Theta3;
       CosT     = 1 - 0.5 * Theta2 + 1.0/24.0 * Theta4;
     }
 
     // the actual "rotation"
 
     G4double R = 1.0 / R_1;
 
     positionMove  = R * ( SinT * vperp + (1-CosT) * B_x_P) + h * vpar;
     endTangent    = CosT * vperp + SinT * B_x_P + vpar;
 
     // Store the resulting position and tangent
 
     yHelix[0]   = yIn[0] + positionMove.x(); 
     yHelix[1]   = yIn[1] + positionMove.y(); 
     yHelix[2]   = yIn[2] + positionMove.z();
     yHelix[3] = velocityVal * endTangent.x();
     yHelix[4] = velocityVal * endTangent.y();
     yHelix[5] = velocityVal * endTangent.z();
 
     // Store 2*h step Helix if exist
 
     if(yHelix2)
     {
       SinT2     = 2.0 * SinT * CosT;
       CosT2     = 1.0 - 2.0 * SinT * SinT;
       endTangent    = (CosT2 * vperp + SinT2 * B_x_P + vpar);
       positionMove  = R * ( SinT2 * vperp + (1-CosT2) * B_x_P) + h*2 * vpar;
       
       yHelix2[0]   = yIn[0] + positionMove.x(); 
       yHelix2[1]   = yIn[1] + positionMove.y(); 
       yHelix2[2]   = yIn[2] + positionMove.z(); 
       yHelix2[3] = velocityVal * endTangent.x();
       yHelix2[4] = velocityVal * endTangent.y();
       yHelix2[5] = velocityVal * endTangent.z();
     }
 
     // Store and/or calculate parameters for chord distance
 
     G4double ptan=velocityVal*B_v_P;
 
     G4double particleCharge = fPtrMagEqOfMot->FCof() / (eplus*c_light); 
     R_Helix =std::abs( ptan/(fUnitConstant  * particleCharge*Bmag));
        
     SetAngCurve(std::abs(Theta));
     SetCurve(std::abs(R));
     SetRadHelix(R_Helix);
   }
 }

G4double G4MagHelicalStepper::DistChord ( ) const

virtual

Implements G4MagIntegratorStepper.

Definition at line 238 of file G4MagHelicalStepper.cc.

References GetAngCurve(), GetRadHelix(), python.hepunit::pi, and python.hepunit::twopi.

 {
   // Check whether h/R >  pi  !!
   // Method DistLine is good only for <  pi
 
   G4double Ang=GetAngCurve();
   if(Ang<=pi)
   {
     return GetRadHelix()*(1-std::cos(0.5*Ang));
   }
   else
   {
     if(Ang<twopi)
     {
       return GetRadHelix()*(1+std::cos(0.5*(twopi-Ang)));
     }
     else  // return Diameter of projected circle
     {
       return 2*GetRadHelix();
     }
   }
 }

virtual void G4MagHelicalStepper::DumbStepper	(	const G4double	y[],
		G4ThreeVector	Bfld,
		G4double	h,
		G4double	yout[]
	)

pure virtual

Implemented in G4HelixMixedStepper, G4ExactHelixStepper, G4HelixExplicitEuler, G4HelixImplicitEuler, G4HelixHeum, and G4HelixSimpleRunge.

Referenced by Stepper().

G4double G4MagHelicalStepper::GetAngCurve ( ) const

inlineprotected

Referenced by G4HelixExplicitEuler::DistChord(), G4ExactHelixStepper::DistChord(), DistChord(), and G4HelixMixedStepper::DistChord().

G4double G4MagHelicalStepper::GetCurve ( ) const

inlineprotected

G4double G4MagHelicalStepper::GetInverseCurve	(	const G4double	Momentum,
		const G4double	Bmag
	)

inlineprotected

Referenced by AdvanceHelix(), and G4HelixMixedStepper::Stepper().

G4double G4MagHelicalStepper::GetRadHelix ( ) const

inlineprotected

Referenced by G4HelixExplicitEuler::DistChord(), G4ExactHelixStepper::DistChord(), DistChord(), and G4HelixMixedStepper::DistChord().

void G4MagHelicalStepper::LinearStep	(	const G4double	yIn[],
		G4double	h,
		G4double	yHelix[]
	)		const

inlineprotected

Referenced by AdvanceHelix().

void G4MagHelicalStepper::MagFieldEvaluate	(	const G4double	y[],
		G4ThreeVector &	Bfield
	)

inlineprotected

Referenced by G4HelixSimpleRunge::DumbStepper(), G4HelixHeum::DumbStepper(), G4HelixImplicitEuler::DumbStepper(), G4HelixExplicitEuler::Stepper(), G4ExactHelixStepper::Stepper(), Stepper(), and G4HelixMixedStepper::Stepper().

void G4MagHelicalStepper::SetAngCurve ( const G4double Ang )

inlineprotected

Referenced by AdvanceHelix(), and G4HelixMixedStepper::Stepper().

void G4MagHelicalStepper::SetCurve ( const G4double Curve )

inlineprotected

Referenced by AdvanceHelix(), and G4HelixMixedStepper::Stepper().

void G4MagHelicalStepper::SetRadHelix ( const G4double Rad )

inlineprotected

Referenced by AdvanceHelix().

void G4MagHelicalStepper::Stepper	(	const G4double	y[],
		const G4double	dydx[],
		G4double	h,
		G4double	yout[],
		G4double	yerr[]
	)

virtual

Implements G4MagIntegratorStepper.

Reimplemented in G4HelixMixedStepper, and G4ExactHelixStepper.

Definition at line 192 of file G4MagHelicalStepper.cc.

References DumbStepper(), and MagFieldEvaluate().

 {  
    const G4int nvar = 6;
 
    G4int i;
 
    // correction for Richardson Extrapolation.
    // G4double  correction = 1. / ( (1 << IntegratorOrder()) -1 );
    
    G4double      yTemp[7], yIn[7] ;
    G4ThreeVector Bfld_initial, Bfld_midpoint;
    
    //  Saving yInput because yInput and yOut can be aliases for same array
 
    for(i=0;i<nvar;i++) { yIn[i]=yInput[i]; }
 
    G4double h = hstep * 0.5; 
 
    MagFieldEvaluate(yIn, Bfld_initial) ;      
 
    // Do two half steps
 
    DumbStepper(yIn,   Bfld_initial,  h, yTemp);
    MagFieldEvaluate(yTemp, Bfld_midpoint) ;     
    DumbStepper(yTemp, Bfld_midpoint, h, yOut); 
 
    // Do a full Step
 
    h = hstep ;
    DumbStepper(yIn, Bfld_initial, h, yTemp);
 
    // Error estimation
 
    for(i=0;i<nvar;i++)
    {
      yErr[i] = yOut[i] - yTemp[i] ;
    }
    
    return;
 }

The documentation for this class was generated from the following files:

Public Member Functions

Protected Member Functions

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation