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    User name S. Sirca

    Log entry time 08:32:55 on November 2,2001

    Entry number 75618

    This entry is a followup to: 75546

    keyword=READ THIS: Previous experience with waterfall target

    I took the liberty to post this entry from the e00102_analysis mailing list
    since I consider it very important for the general shift-taker. It contains
    a short description by Larry Weinstein of what was going on previous
    morning, and Kevin Fissum's remarks to it.
    -----------------------------------------------------------
    [Larry] Symptoms: increasing radiation level in the dump ion counters tripped
    the beam at 05:30. This level had increased exponentially over about 3 hours.
    After this, we could not put 5 uA on the waterfall target. Day shift put in
    the BeO. That worked. Then we put in the waterfall at 1 uA (pulsed) and
    saw a bizarre y-target spectrum (see halog). Meekins and Folts rebooted
    the target motion controller, moved the waterfall target to home (to reset
    the motor encoder) and then back to waterfall, and turned the pump back
    on. Everything then seemed nominal. It was probably due to the target
    filling with water and possibly also being out of position.
    -----------------------------------------------------------
    [Kevin] W r t the target filling - this is not new. It
    happened during E89-003 for the run period in
    August, 1997. The *exact* same behaviour was
    observed. The *exact* same consequences resulted.
    As the target fills, when the level gets close
    to the beam plane, turning on the vertical raster
    should also cause the trip, and indicate it is
    time for a reset. As I recall, we backed off
    slightly on the pump speed, but it was not clear
    this had any effect, since the run period was only
    eight days and the effect has a rather long time
    constant. Has a stripline monitor of the ion dump
    counters been put on prominent display somewhere?
    -----------------------------------------------------------
    Let me mention that we have the strip-chart monitor now running for both
    ion chambers in the beam dump. This should be flat with beam on. Any
    increase in rate is suspicious. Please also keep an eye on the react_z spectrum
    for EACH production run.