Find multipole components of fieldmaps by numerical differentiation. More...

#include <BDSFieldMagGradient.hh>

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Public Member Functions
BDSMagnetStrength *	CalculateMultipoles (BDSFieldMag *BField, G4int order, G4double Brho=4)
	Find the Magnet strengths of a multipole field to nth order.

G4double	GetBy (BDSFieldMag *BField, G4double x, G4double y=0) const
	Query a point on x axis (by default) for By.

std::vector< G4double >	PrepareValues (BDSFieldMag *field, G4int order, G4double centreX, G4double h, G4int &centreIndex) const

std::vector< std::vector< G4double > >	PrepareSkewValues (BDSFieldMag *field, G4int order, G4double centreX, G4double h, G4int &centreIndex) const

G4double	Derivative (const std::vector< G4double > &data, const G4int order, const G4int startIndex, const G4double h) const

Detailed Description

Find multipole components of fieldmaps by numerical differentiation.

Not optimised right now. Uses the Central difference method with each level taking the previous as the function (i.e. 1st order takes b, 2nd order takes 1st). Step size works right now but dropping it too low introduces large, inconsistent errors.

Author: Josh Albrecht

Definition at line 42 of file BDSFieldMagGradient.hh.

Constructor & Destructor Documentation

◆ BDSFieldMagGradient()

BDSFieldMagGradient::BDSFieldMagGradient ( )

Definition at line 34 of file BDSFieldMagGradient.cc.

◆ ~BDSFieldMagGradient()

BDSFieldMagGradient::~BDSFieldMagGradient ( )

Definition at line 37 of file BDSFieldMagGradient.cc.

Member Function Documentation

◆ CalculateMultipoles()

BDSMagnetStrength * BDSFieldMagGradient::CalculateMultipoles	(	BDSFieldMag *	BField,
		G4int	order,
		G4double	Brho = `4`
	)

Find the Magnet strengths of a multipole field to nth order.

Definition at line 48 of file BDSFieldMagGradient.cc.

References Derivative(), PrepareSkewValues(), and PrepareValues().

Referenced by BDSFieldLoader::LoadMagField().

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◆ Derivative()

G4double BDSFieldMagGradient::Derivative	(	const std::vector< G4double > &	data,
		const G4int	order,
		const G4int	startIndex,
		const G4double	h
	)		const

Returns 'order' derivative of data about startIndex in data with assumed spacing of samples of h (in Geant4 units). Derivative returned is in SI T/(m^order).

Definition at line 107 of file BDSFieldMagGradient.cc.

References Derivative().

Referenced by CalculateMultipoles(), and Derivative().

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◆ GetBy()

G4double BDSFieldMagGradient::GetBy	(	BDSFieldMag *	BField,
		G4double	x,
		G4double	y = `0`
	)		const

Query a point on x axis (by default) for By.

Definition at line 40 of file BDSFieldMagGradient.cc.

References BDSFieldMag::GetField().

Referenced by PrepareValues().

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◆ PrepareSkewValues()

std::vector< std::vector< G4double > > BDSFieldMagGradient::PrepareSkewValues	(	BDSFieldMag *	field,
		G4int	order,
		G4double	centreX,
		G4double	h,
		G4int &	centreIndex
	)		const

Similar to PrepareValues but for skew fields. For each order, rotate field by CLHEP::pi / (2*order + 2) - ie quadrupole = order 1 -> pi/4. For each rotation provide the vector of values to calculate gradients on.

Definition at line 90 of file BDSFieldMagGradient.cc.

References PrepareValues().

Referenced by CalculateMultipoles().

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◆ PrepareValues()

std::vector< G4double > BDSFieldMagGradient::PrepareValues	(	BDSFieldMag *	field,
		G4int	order,
		G4double	centreX,
		G4double	h,
		G4int &	centreIndex
	)		const

Prepare a vector of values corresponding to +- (2*order) in units of h about (spatial coordinate) centreX. centreIndex is passed by reference to write out which index represents the centre of the vector with x = centreX.

Definition at line 74 of file BDSFieldMagGradient.cc.

References GetBy().

Referenced by CalculateMultipoles(), and PrepareSkewValues().

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