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    User name Armstrong

    Log entry time 10:57:39 on July 28, 2005

    Entry number 149797

    This entry is a followup to: 149796

    keyword=more on phase advance..

    I quote below Jay's "Benesch Report" from this AM, which further amplifies on the progress on the optics issue...

    (from 7/28/05 Benesch report):

    I spent day and swing shift working with Operations, HAPPEx collaboration and CASA on hall A optics and therefore found the hardware troubles more irritating than usual. So I won't talk about them, just about the optics. That's still not right. We did demonstrate that the seemingly too-perfect correlation of vertical motion at the 1H04 A and B BPMs is real, not instrumental, by checking against cavity BPMs and nearby harps. We determined that the model is a good fit to the machine through the exit of the Compton chicane. We determined that we could revert to an optics which has good "phase advance" in the vertical plane but none in the horizontal and too small a raster, again verifying that the BPMs work. What we still haven't got is an installed optics that works in both planes and has a large raster. We have that in silico, so it's not physically impossible. We just can't get the imperfect machine set up to reproduce the model. There are no BPMs among the six quads so we've no way of pinning down which is causing the disagreement between machine and model. Discussion is underway on driving the modulation coils with beam-synched 30 Hz so we can empirically adjust quads among the last six to get the responses needed. This is the tool used to get around this same problem in the rest of the machine.