FFB troubleshooting
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Jump to navigationJump to searchPREXI documentation:
- https://hallaweb.jlab.org/halog/log/html/0909_archive/090906203957.html
- https://hallaweb.jlab.org/halog/log/html/0909_archive/090907094816.html
Trouble with fastfeedback can take the form of:
- 1) Fast feedback not working.
- 2) Fast feedback killing bpm12x, which we need for energy monitor.
If turning on FFB leads to ion chamber trips -
- this is probably due to the self-calibration.
- Possibly running in "relative" mode (compared to "absolute" mode) on FFB may help, so it is one thing to ask the ops about.
If bpm12x is saturating -
- This happens when FFB gains that crate incorrectly. It can be good enough for FFB (and ops gets no errors) but we are still hosed due to bpm saturation.
- Keep an eye on bpm12x wires, and make sure that they are around 40k channels, not 60k channels.
- If they are saturating, call mcc and request that a "gain search" on ffb.
- If that doesn't clear the problem, ask them to turn FFB off, then set BPMs to "Normal OPS" mode, and then back on.
- Might also benefit from running in "manual gain" mode of FFB, rather than the FFB "auto gain" mode on the bpms. (The control for this is found under the debug tab, on the FFB control screen, under the title "BPM gain control").
To quote some wisdom - "Remember: bpm12x is absolutely critical. Data is useless without it. Running when bpm12x is saturating is the same as not having beam. If you aren't watching 12x and it saturates, this is comparable to forgetting to put the target in, or forgetting to put HV on the detector PMTS... get the point? Its crucial. Also, the time that BPM12x is saturating is not ABU."
