BEAMBEAM—An element to provide kicks from another beam

10.3 BEAMBEAM—An element to provide kicks from another beam

An element to provide kicks from another beam
Parallel capable? : yes
GPU capable? : no
Back-tracking capable? : no


Parameter Name	Units	Type	Default	Description

CHARGE	C	double	0.0	charge of opposing beam

XCENTER	M	double	0.0	horizontal center position of opposing beam

YCENTER	M	double	0.0	vertical center position of opposing beam

XSIZE	M	double	0.0	horizontal size of opposing beam

YSIZE	M	double	0.0	vertical size of opposing beam

DISTRIBUTION	NULL	STRING	gaussian	distribution type of opposing beam

GROUP		string	NULL	Optionally used to assign an element to a group, with a user-defined name. Group names will appear in the parameter output file in the column ElementGroup

This element provides a simple model of beam-beam kicks from a stiff opposing beam defined by the bunch charge, transverse centroids, and transverse sizes.

Three distribution types are supported:

gaussian — A transversely-gausssian charge distribution is used. The parameters XSIZE and YSIZE are interpreted as the rms sizes of the distribution. The computations are based on the Bassetti-Erskine formula [59].
uniform — A uniformly-filled two-dimensional ellipsoidal distribution is used.
$ρ(x,y,z) = -Q--- πabL$ (28)

when (x∕a)² + (y∕b)² ≤ 1 and ≤ L∕2, and zero otherwise. The parameters XSIZE and YSIZE are interpreted as a and b, respectively. L is the length of the slug of charge, which is assumed to be sufficiently short that the impulse approximation is valid. The computations are based on Furman’s expressions [60].
parabolic — A parabolic two-dimensional ellipsoidal distribution is used.
$ρ(x,y,z) = -2Q--(1- (x ∕a)2 - (y∕b)2) πabL$ (29)

when (x∕a)² + (y∕b)² ≤ 1 and ≤ L∕2, and zero otherwise. The parameters XSIZE and YSIZE are interpreted as a and b, respectively. L is the length of the slug of charge, which is assumed to be sufficiently short that the impulse approximation is valid. The computations are based on Furman’s expressions [60].

BGGEXP

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