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User name R. Michaels
Log entry time 01:25:58 on March 1,2009
Entry number 263950
This entry is a followup to: 263940
keyword=more on Qasy (it looks ok)After a more refined analysis (fig 1), I find the charge asymmetry
is probably ok. The difference here is that I used more agressive
cleanup cuts to exclude the beam trips. The beam is very unstable.
Even with these cuts, I still get a rather wide (noisy) charge
asymmetry, but I suppose this is acceptable for this experiment.
Why is Qasy more noisy ? MCC re-tuned the capture at 8 pm, I hear.
This is the RF cavity that captures electrons through the chopper.
I speculate there is a helicity-correlated noise in beam position
causing instability here. The swing shift says the instability
in Qasy started happening at 8 pm with this change. This may require
a look-see by an injector expert but unless you're measuring ppm
level asymmetries I would wait until Monday to ask.
Why does the MCC graph show big excursions ? I don't know. Maybe
their cleanup cuts are less clean, or maybe the big noise interacts
in a wierd way with their software. Hard to say. But as I said in
halog 263940 there is nothing wrong with the HAPPEX feedback system.
It looks like the DAC is operating within 4.8 to 5.3 which is near
the middle of its dynamic range (0 - 10). All fine.
FIGURE 1
