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    User name R. Michaels

    Log entry time 06:32:45 on September 04, 2009

    Entry number 287887

    This entry is a followup to: 287852

    keyword=clarfications about spot++

    I talked to Kai and here are some points I made about spot++

    - It's true you want to want to check spot++ before putting high-I on LH2. It is usually
    sufficient to run with ps8=20 and no target. The raster current will look flat except for
    small peaks at the ends of the orbit where you integrate over the turnover (zero deriv).
    Example in halog 287686.

    - Kai ran with C12 target. He had a mix of T8 (makes it flat) and physics triggers (potentially
    not flat). Reason phys. trig. may be not flat: if you are hitting the frame that holds the C12.
    This effect is known from previous running. BTW, this is a good way to see if the lead
    melts when we do PREX - then you see a hole in this pic.

    - Note, BPMAy and BPMBy also show a bump, but its sorta in the middle. Reason: BPMs have
    a phase lag which is a fraction of the raster period. The raster current pickoff has no lag.

    - Does it matter that we're hitting the frame of C12 ? I don't think so, but ask the RC.
    What *does* matter is if we are hitting the Alum can walls of the LH2. What also matters
    is target boiling, which is why the raster is so big now. Be careful, we don't care about C12.

    - To be more sensitive to possible Alum wall background, prescale away T8. Don't need
    that flat offset. Use physics triggers.

    - In all cases where my advice contradicts the RCs, the RC takes priority.


    A copy of this log entry has been emailed to: rsholmes, paschke