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    User name Kai Pan

    Log entry time 09:06:08 on November 12, 2009

    Entry number 299171

    This entry is a followup to: 299064


    keyword=find the problem causing the trouble on GC

    I traced back all yesterday's HRS right arm runs after #4941 to find the turning point that causes the GC spec and TDC change. The change happened between #4923 and #4924. What's the difference? The only diff is, first of all the raser size which I don't think will affect, another is the rate. #4923 is a spot++ run under 2uA, however #4924 is running under 100uA. In order to see if it is the real reason, I asked MCC for a 10min 2uA beam to see the result. Run #4953 is 100uA run, and run#4955 is 2uA run. The result shows the same diff as what we saw in #4923 and #4924, also as #4921,#4941 posted by Xiaochao. The results are attached. The first two pics are from #4953. Among them, first is GC spec with TDC ele veto cut, and the second is the histogram of global signals. The last two pics are the same from #4955. We can see that #4955(2uA) is much more clean than that of #4953(100uA). Xiaochao called in for some more detailed diagnoses before reaching the conclusion. I am still working on it.

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

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