HAPPEX/PVDIS Troubleshooting

last updated: Nov 15, 2009

What to do if...

BPM12 is saturating

N.B Instructions modified 8 Sep 2009 to account for 18 bit ADC.

During data taking keep an eye on the BPM12 stripcharts in Panguin. All channels should be roughly 85K. If they go to around 230K they are saturating. This is at present regarded as highly unlikely if not impossible, however data with BPM12 saturating is unacceptable; beam might as well be off. In fact, when BPM12 is saturating we log this as "Beam not acceptable". (Exception: BPM saturation in the first minute or so after a beam trip -- but not beyond that -- is harmless.)

If BPM12 is saturating IMMEDIATELY do the following:

  1. Call MCC and request they do "gain search" on FFB.
  2. Also ask MCC to check that FFB is running in "manual gain" mode, 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").
  3. If that doesn't clear the problem, ask them to:
    1. Turn FFB off.
    2. put the crate in SEE normal ops and wait for BPM12 to return to normal gain on our Panguin monitor.
    3. Turn FFB back on, in manual gain mode.

If none of this works call the RC, and MCC should call their software on call people.

Log the problem in HALOG. When filling out the beam accounting, report "Beam Not Acceptable" for the duration of the time BPM12 was saturating.

Empty Histograms?!?!


WHY? SEVERITY HOW TO CHECK? WHAT TO DO?
No Q2 plots, or anything else that needs tracks. Okay These plots are only filled for special runs VDCs are off at high current. Do NOT turn on.
Beam Current is
    less than 95 ľA
Okay Check "Hall A Current Monitor"
Wait/Ask for higher beam current.
Beam Is Tripping Frequently
(More than 1 trip every
     5 minutes)
Not So Good Check "Hall A Current Monitor"
Wait for stable current, or
    ask MCC for better stability.
Beam Is Noisy Not Good Difficult to diagnose
Ask MCC to check "Laser Phase Noise"
    or "Injector Transmission"
Ask MCC to fix it.
    (Source On-Call or Optics On-Call)
HAPPEX Detectors
     are saturated
VERY BAD Check "Detector Stripcharts"
    in Online Monitor
Vertical scale should show signal less than 50k
Adjust detector HV to bring signal below 45k
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BPMs are saturated VERY BAD Check "Target BPMs" and "ARC BPMs"
    in Online Monitor
Horizontal scale for each BPM
     should be the same
Events will be cut if the BPM is saturated.
Inform MCC that BPM gains are too high.
    iocse9 for BPM12
    iocse10 for BPM 4A and 4B
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