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TFBDRIVER

Driver for a transverse feedback loop
Parallel capable? : no
Parameter Name Units Type Default Description
ID   STRING NULL System identifier
STRENGTH   double 0.0 Strength factor
KICK_LIMIT $RAD$ double 0.0 Limit on applied kick
DELAY   long 0 Delay (in turns)
OUTPUT_FILE   STRING NULL File for logging filter output and driver output
A0   double 1 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
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 is used together with the TFBPICKUP element to simulate a digital transverse feedback system. Each TFBDRIVER element must have a unique identification string assigned to it using the ID parameter. The same identifier must be used on a TFBPICKUP element. This is the pickup from which the driver gets its signal. Each pickup may feed more than one driver, but a driver can use only one pickup.

A 15-term FIR filter can be defined using the A0 through A14 parameters. The output of the filter is simply $\sum_{i=0}^{14}
a_i P_i$, where $P_i$ is the pickup filter output from $i$ turns ago. The output of the filter is optionally delayed by the number of turns given by the DELAY parameter.

To some extent, the DELAY is redundant. For example, the filter $a_0=0, a_1=1$ with a delay of 0 is equivalent to $a_0=1, a_1=0$ with a delay of 1. However, for long delays or delays combined with many-term filters, the DELAY feature must be used.

The output of the filter is multiplied by the STRENGTH parameter to get the kick to apply to the beam. The KICK_LIMIT parameter provides a very basic way to simulate saturation of the kicker output.

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


next up previous
Next: TFBPICKUP Up: Element Dictionary Previous: STRAY
Robert Soliday 2014-03-21