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    User name Jin Huang

    Log entry time 07:17:23 on November 16, 2008

    Entry number 249161

    This entry is a followup to: 249159


    keyword=Scalar Fast Clock Synchronization Check

    A 103kHz fast clock is sent to both LHRS and bigbtie scalars. The 
    difference between clock counts of two scalars are no more than 10^-5 
    level. However there is some interesting structure below 10^-5.
    The count difference between the two scalars are checked to be 
    ** count difference  <1ms for a 1M/50min run for scalar sets of 
    ungated, (++),(+-) and (-+) .
    ** For scalar sets of (--), The count difference of bigbite - LHRS is 
    climbing @ ~10 count/s = ~2 count / scalar read = ~2 count /100 event. 
    This climbing is also correlated to data taking rate. 
    Besides, there is a ~200us = ~20 counts vibration in counts diff of 
    gated scalars. It's correlated to helicity state. For, ex: for scalars 
    (spin=-1,hel=+1), the bigbite scalar will read extra ~20 more count 
    when the scalar event is read in helicity=+1 state. It appears as if 
    gate for left HRS scalar is applied 200us later than the one on Bigbite 
    (although the cable delay is 3 order of magnitude smaller).
    See plots below & in Last entry. run # 3308 is taken as an example.

    A copy of this log entry has been emailed to: kalyan, xqian, rom

    Scalar count difference for (spin=-1, helicity=-1) sets. It's climbing when scalar is actived

    20 count vibration when scalar is actived. Same for 4 gated scalar. Disappear on ungated scalar