G4BorisScheme Class Reference

The G4BorisScheme class implements of the Boris algorithm for advancing charged particles in an electromagnetic field. More...

#include <G4BorisScheme.hh>

Public Member Functions
	G4BorisScheme ()=default
	G4BorisScheme (G4EquationOfMotion *equation, G4int nvar=6)
	~G4BorisScheme ()=default
void	DoStep (G4double restMass, G4double charge, const G4double yIn[], G4double yOut[], G4double hstep) const
void	StepWithErrorEstimate (const G4double yIn[], G4double restMass, G4double charge, G4double hstep, G4double yOut[], G4double yErr[]) const
void	StepWithMidAndErrorEstimate (const G4double yIn[], G4double restMass, G4double charge, G4double hstep, G4double yMid[], G4double yOut[], G4double yErr[]) const
G4EquationOfMotion *	GetEquationOfMotion () const
G4int	GetNumberOfVariables () const

Detailed Description

The G4BorisScheme class implements of the Boris algorithm for advancing charged particles in an electromagnetic field.

Definition at line 49 of file G4BorisScheme.hh.

Constructor & Destructor Documentation

G4BorisScheme() [1/2]

G4BorisScheme::G4BorisScheme ( )

default

Default Constructor.

G4BorisScheme() [2/2]

G4BorisScheme::G4BorisScheme	(	G4EquationOfMotion *	equation,
		G4int	nvar = 6 )

Constructor for the equation of motion.

Parameters

[in]	equation	Pointer to the equation of motion algorithm.
[in]	nvar	The number of integration variables.

Definition at line 41 of file G4BorisScheme.cc.

  : fEquation(equation), fnvar(nvar)
{
  if (nvar <= 0)
  {
    G4Exception("G4BorisScheme::G4BorisScheme()",
                "GeomField0002", FatalException,
                "Invalid number of variables; must be greater than zero!");
  }
}

~G4BorisScheme()

G4BorisScheme::~G4BorisScheme ( )

default

Default Destructor.

Member Function Documentation

DoStep()

void G4BorisScheme::DoStep	(	G4double	restMass,
		G4double	charge,
		const G4double	yIn[],
		G4double	yOut[],
		G4double	hstep ) const

Does one step, updating velocity and position.

Parameters

[in]	restMass	Particle mass.
[in]	charge	Particle charge.
[in]	yIn	Initial position.
[out]	yOut	Updated position.
[in]	hstep	Proposed step.

Definition at line 52 of file G4BorisScheme.cc.

{
  G4double yOut1Temp[G4FieldTrack::ncompSVEC];
  G4double yOut2Temp[G4FieldTrack::ncompSVEC];
  
  // Used the scheme described in the following paper:
  // https://www.research-collection.ethz.ch/bitstream/handle/20.500.11850/153167/eth-5175-01.pdf?sequence=1
  UpdatePosition(restMass, charge, yIn, yOut1Temp, hstep/2);
  UpdateVelocity(restMass, charge, yOut1Temp, yOut2Temp, hstep);
  UpdatePosition(restMass, charge, yOut2Temp, yOut, hstep/2);
}

Referenced by StepWithMidAndErrorEstimate().

GetEquationOfMotion()

G4EquationOfMotion * G4BorisScheme::GetEquationOfMotion ( ) const

inline

Auxiliary methods returning a pointer to the equation of motion and the number of integration variables.

GetNumberOfVariables()

G4int G4BorisScheme::GetNumberOfVariables ( ) const

inline

StepWithErrorEstimate()

void G4BorisScheme::StepWithErrorEstimate	(	const G4double	yIn[],
		G4double	restMass,
		G4double	charge,
		G4double	hstep,
		G4double	yOut[],
		G4double	yErr[] ) const

Adopts the Boris Scheme Stepping to estimate the integration error. Uses two half-steps (comparing to a full step) to obtain output and error estimate.

Parameters

[in]	yIn	Initial position.
[in]	restMass	Particle mass.
[in]	charge	Particle charge.
[in]	hstep	Proposed step.
[out]	yOut	Updated position.
[out]	yErr	The estimated error.

Definition at line 166 of file G4BorisScheme.cc.

{
  // Use two half-steps (comparing to a full step) to obtain output
  // and error estimate
 
  G4double yMid[G4FieldTrack::ncompSVEC];
  StepWithMidAndErrorEstimate(yIn, restMass, charge, hstep, yMid, yOut, yErr);
}

StepWithMidAndErrorEstimate()

void G4BorisScheme::StepWithMidAndErrorEstimate	(	const G4double	yIn[],
		G4double	restMass,
		G4double	charge,
		G4double	hstep,
		G4double	yMid[],
		G4double	yOut[],
		G4double	yErr[] ) const

Adopts the Boris Scheme Stepping to estimate the integration error. Uses two half-steps (comparing to a full step) to obtain output and error estimate. Same as above, but also returns the mid-point evaluation.

Parameters

[in]	yIn	Initial position.
[in]	restMass	Particle mass.
[in]	charge	Particle charge.
[in]	hstep	Proposed step.
[out]	yMid	tThe mid-point evaluation.
[out]	yOut	Updated position.
[out]	yErr	The estimated error.

Definition at line 180 of file G4BorisScheme.cc.

{
  G4double halfStep= 0.5*hstep;
  G4double yOutAlt[G4FieldTrack::ncompSVEC];   
 
  // In a single step
  DoStep(restMass, charge, yIn,  yOutAlt, hstep );
 
  // Same, and also return mid-point evaluation
  DoStep(restMass, charge, yIn,  yMid, halfStep );
  DoStep(restMass, charge, yMid, yOut, halfStep );
 
  for( G4int i = 0; i < fnvar; i++ )
  {
    yErr[i] = yOutAlt[i] - yOut[i];
  }
}

Referenced by StepWithErrorEstimate().

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

• G4BorisScheme.hh
• G4BorisScheme.cc