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User name brads
Log entry time 13:05:07 on March 11, 2012
Entry number 365682
This entry is a followup to: 365669
keyword=re: Bleedthrough test
Note that the Hall C BCMs are not (AFAIK) fully calibrated yet. You
could just be seeing an unsubtracted pedestal that is being converted
into the 2--3 nA apparent readback.
The best way to tell is to stripchart the raw readback values (ie.
IBM1H00MAGA/B from this
) and then identify the readbacks for these four cases:
Ideally, all four readbacks should be the same -- that is your zero current
- Hall C on, Hall A laser off, A slit fully closed
- Hall C on, Hall A laser off, A slit at '14' (our normal setting)
- Hall C off, Hall A laser off, A slit fully closed
- Hall C off, Hall A laser off, A slit at '14' (our normal setting)
This is a pretty short test to run invasively if we want, but it can also be
done purely parasitically by looking in the EPICS archiver for periods that
match the above conditions. ie. Hall C trips off during a TE or the target
anneal period where the Hall A laser is off. If the right slit open/closed
combos don't show up, then they can be arranged during the next time A laser
is off for a few minutes.