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    User name R. Michaels

    Log entry time 03:32:45 on May23,2002

    Entry number 4037

    keyword=tuning and harp scans - not making sense

    After we got the raster size we need, we spent 2 hours trying to tune the spot
    size to the size needed which is roughly 100 um x 100 um. In various attempts
    it would be either MUCH bigger or MUCH smaller according to the fits, but finally
    we decided these fits make no sense. Take for example run 1729 which at 4A is
    79 x 62 um and at 4B is 213 x 6 um (yes, 6 um). But if I look at histograms of the
    HARP data, there is nothing as narrow as 6. All much wider. Nicely Gaussian,
    no saturation. We don't know how the three bumps translate into the fitted values,
    but we cannot see how 6 um arises. The target OTR says the beam is roughly 200 um wide in X and Y.
    See also HARP run 1732 which says the beam is 3 microns in Y at target.
    We decided we cannot believe this and will continue with the program.
    In the latest run, 1732, the values were
    BPM4A (called 3A) : horiz. sigma = 135 um, vert. sigma = 191 um
    BPM4B (called 3B): horiz. sigma = 442 um, vert sigma = 3 um (if you believe it)
    Investigating....