QUAD

A quadrupole implemented as a matrix, up to 3rd order.

Parameter Name	Units	Type	Default	Description
L	$M$	double	0.0	length
K1	$1/M^{2}$	double	0.0	geometric strength
TILT	$RAD$	double	0.0	rotation about longitudinal axis
FFRINGE		double	0.0	fraction of length occupied by linear fringe region
DX	$M$	double	0.0	misalignment
DY	$M$	double	0.0	misalignment
DZ	$M$	double	0.0	misalignment
FSE	$M$	double	0.0	fractional strength error
HKICK	$RAD$	double	0.0	horizontal correction kick
VKICK	$RAD$	double	0.0	vertical correction kick
HSTEERING		long	0	use for horizontal steering?
VSTEERING		long	0	use for vertical steering?
ORDER		long	0	matrix order
FRINGE_TYPE		STRING	inset	type of fringe: "inset" or "fixed-strength"

This element simulates a quadrupole using a matrix of first, second, or third order.

By default, the element has hard edges and constant field within the defined length, L. However, soft-edge effects (up to second order) may be added using the FFRINGE and FRINGE_TYPE parameters. If FFRINGE is zero (the default), then the magnet is hard-edged. If FFRINGE is positive, then the magnet has linear fringe fields of length FFRINGE*L/2 at each end. That is, the total length of fringe field from both ends combined is FFRINGE*L.

Depending on the value of FRINGE_TYPE, the fringe fields are modeled as contained within the length L (``inset'' type) or extending symmetrically outside the length L (``fixed-strength'' type).

For ``inset'' type fringe fields, the length of the ``hard core'' part of the quadrupole is L*(1-FFRINGE). For ``fixed-strength'' type fringe fields, the length of the hard core is L*(1-FFRINGE/2). In the latter case, the fringe gradient reaches 50% of the hard core value at the nominal boundaries of the magnet. This means that the integrated strength of the magnet does not change as the FFRINGE parameter is varied. This is not the case with ``inset'' type fringe fields.