TFBPICKUP

Pickup for a transverse feedback loop

Parameter Name	Units	Type	Default	Description
ID		STRING	NULL	System identifier
PLANE		STRING	x	"x" or "y"
RMS_NOISE	$M$	double	0.0	RMS noise to add to position readings.
A0		double	0.0	Filter coefficient
A1		double	0.0	Filter coefficient
A2		double	0.0	Filter coefficient
A3		double	0.0	Filter coefficient
A4		double	0.0	Filter coefficient
A5		double	0.0	Filter coefficient
A6		double	0.0	Filter coefficient
A7		double	0.0	Filter coefficient
A8		double	0.0	Filter coefficient
A9		double	0.0	Filter coefficient
A10		double	0.0	Filter coefficient
A11		double	0.0	Filter coefficient
A12		double	0.0	Filter coefficient
A13		double	0.0	Filter coefficient
A14		double	0.0	Filter coefficient

This element is used together with the TFBDRIVER element to simulate a digital transverse feedback system. Each TFBPICKUP element must have a unique identification string assigned to it using the ID parameter. This is used to identify which drivers get signals from the pickup.

A 15-term FIR filter can be defined using the A0 through A14 parameters. The input to the filter is the turn-by-turn beam centroid at the pickup location. The output of the filter is simply $\sum_{i=0}^{14} a_i C_i$, where $C_i$ is the position from $i$ turns ago. Note that $\sum_{i=0}^{14} a_i$ must be zero. Otherwise, the system will attempt to correct the DC orbit. The output of the filter is the input to the driver element(s).

See Section 7.2.14 of Handbook of Accelerator Physics and Engineering (Chao and Tigner, eds.) for a discussion of feedback systems.