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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.
    Run 11648
    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.
    Use curmon=bcm1
    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.