Pickup for a turn-by-turn feedback loop
Parallel capable? : yes
GPU capable? : no
Back-tracking capable? : no
| Parameter Name | Units | Type | Default | Description |
| ID | STRING | NULL | System identifier |
|
| PLANE | STRING | x | ”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 | Units | Type | 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 | double | 0.0 | Reference frequency for computing phase offsets. |
|
| DX | M | double | 0.0 | Horizontal offset (subtracted from pickup signal). |
| DY | M | double | 0.0 | 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