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User name R. Michaels
Log entry time 06:19:18 on August26,2009
Entry number 286080
keyword=Lumi runs with "high" current
Restricted to 30 uA due to ion chambers.
Run 11646 ovs=0. Beam up to 30 uA but tripping a lot.
Luis is adjusting HV on Blumi. Also adjusting BCM gains.
Run 11647 ... same as 46.
BCM1 hi gain, BCM2 low gain, thick tantalum, 30 uA, ovs=0
Plan is to do ovs=0,1,3,7 (i.e. no-oversamp, then x2, x4, x8)
and have a beam ramp in each run : 0 to 30uA in 2 minutes.
Run 11649 ... ovs=1
Run 11650 ... same
The runs with ovs=1 show Blumi=100K at start of run, dropping
to 10K after a few min.
Run 11651 ... ovs=3
Conclusion: Oversampling data is not useful.
Run 11652 ... ovs=0 again
Symptom similar to 11649/50.
Oops ! had rampdelay on RHRS = 200. Must set to zero.
Run 11653 ... ovs=0 ... Rampdelays all zero. Now, data looks normal.
So it looks like this different rampdelay, which led to zero
deadtime for ovs>0, is bad for other reasons !
During 11653 we do another current ramp.
Observed poor synch for run 11653 -- in synch mon, but also
lack of tight correlation of blumi to bcm. Looks like the
ADCs in R-HRS are lagging behind. Yuk.
06:18 Request access to swap PREX Quartz detector config.