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    User name R. Michaels

    Log entry time 11:07:43 on October11,2005

    Entry number 156556

    keyword=FR AC relay

    A remote relay was installed by Chen Yan to be able to turn off the
    fast raster power. This is useful for some runs, e.g. cavity monitor
    checkout, where we really want no raster. By design the raster always
    had some small nonzero current even if the MCC tried to turn it off,
    so this switch turns it COMPLETELY OFF.

    The switch is in the NIM crate where all the helicity electronics
    is located. The usage:

    1. First, take the cryotarget out of the beam.

    2. Ramp the raster to zero -- ask MCC to do it.

    Ramping is important because if you slam the raster current to zero
    you might destroy some components -- which is one reason to dislike
    this switch and I'll probably bypass it at some point but we'll
    start the run with it installed.   On the other hand, AC power failure,
    which does happen, creates the same danger and it begs the question
    why we don't use a UPS ...

    3. Put the relay toggle switch to the "off" position.

    Note, unplugging the BNC cable also turns off raster, which is quite
    dangerous (see comment after #2), but turning off the NIM crate
    does not turn off the raster (and that's a good thing).