10.108 TFBPICKUP—Pickup for a turn-by-turn feedback loop

Pickup for a turn-by-turn feedback loop
Parallel capable? : yes
GPU capable? : no
Back-tracking capable? : no






Parameter Name UnitsType Default

Description






ID STRINGNULL

System identifier






PLANE STRINGx

”x”, ”y”, ”delta”, or ”phase”






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






A15 double 0.0

Filter coefficient






A16 double 0.0

Filter coefficient






A17 double 0.0

Filter coefficient






A18 double 0.0

Filter coefficient






A19 double 0.0

Filter coefficient






A20 double 0.0

Filter coefficient






A21 double 0.0

Filter coefficient






A22 double 0.0

Filter coefficient






A23 double 0.0

Filter coefficient






A24 double 0.0

Filter coefficient






A25 double 0.0

Filter coefficient






A26 double 0.0

Filter coefficient






A27 double 0.0

Filter coefficient






A28 double 0.0

Filter coefficient






A29 double 0.0

Filter coefficient






UPDATE_INTERVAL long 0

Interval in turns for sampling data and updating filter output.






TFBPICKUP continued

Pickup for a turn-by-turn feedback loop






Parameter Name UnitsType Default

Description






START_PASS long -1

If positive, first pass on which to perform computations.






END_PASS long -1

If positive, last pass on which to perform computations.






REFERENCE_FREQUENCY double0.0

Reference frequency for computing phase offsets.






DX M double0.0

Horizontal offset (subtracted from pickup signal).






DY M double0.0

Vertical offset (subtracted from pickup signal)






BUNCHED_BEAM_MODE short 1

If non-zero, run in bunched beam mode.






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 TFBDRIVER element to simulate a digital turn-by-turn 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 30-term FIR filter can be defined using the A0 through A29 parameters. The input to the filter is the turn-by-turn beam centroid at the pickup location. The output of the filter is simply i=029aiCi, where Ci is the centroid from i * U turns ago, where U is the value specified by the UPDATE_INTERVAL parameter. Note that i=029ai should generally 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).

The PLANE parameter can take four values: “x”, “y”, “delta”, and “phase”, specifying what centroid property of the beam is measured by the pickup. The “delta”-mode pickup is nonphysical, but could have applications to simulations where is not convenient to put a pickup in a high-dispersion area.

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

TMCF