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    User name R. Michaels

    Log entry time 13:51:07 on July24,2005

    Entry number 149295


    keyword=drift in peak location

    Between two runs with "nominally correct" alignment settings,
    and launch angles, runs 2196 and 2234, there is an apparent drift
    in the elastic peak of 3 MeV, see fig 1. This stuck out because
    as I was looking into the septum scan I noticed the baseline run
    (2234) was not aligned very well and wondered why. The detector
    limits (1/e point, sort-of) are also shown in fig1. a magenta line
    showing a width of about 20 MeV. This was judged, as usual,
    by run 2181 (a -2% run).

    We should do frequent Q2 scanner scans to verify nothing is drifting !!!

    In both runs the peak is still within the 20 MeV wide detector,
    but run 2196 is located better. Note, a 3 MeV shift would cut
    3 % of the rate -- it cuts the radiative tail.

    What causes a common 3 MeV shift ?   Could be beam energy.

    FIGURE 1