Notes - Synclite Instrumentation/beam physics meeting Wed. Sept 8, 2004
         ( I'll start a BD document for this note and future ones from
            the Inst/beam physics meetings>)

 Next week - Tune measurements

 Action Items:

   1. A careful calculation of the diffraction
      contribution is needed.   Sasha will do this with
      Timur Shaftan's code once Sasha gets the code.
      (Note, SL3 code makes no diffraction correction
      to sigma**2)
   2. Analyze if the body light is better than the edge
      light for stable operation.
   3. Check for the factor of 2 observed
      by Sasha when he compared to flying wires.
      (After the meeting Randy and Stephen found that
      the returned sigma is sqrt(2) larger than the
      actual sigma. This accounts for the factor of two
      and also means that Sasha's offset is a factor
      of 2 too big.)
   4. Sasha will repeat his analysis for protons
      on store 3744 which has a wide range of
      proton emittances bunch to bunch.
   5. It would be very useful if someone(Randy?)
      would summarize and document the optical
      calculations made to explain the two peak
      behavior.  This is, I think, equivalent
      to the suggestion that a simple model be made.

 Some details:

    1. Randy showed some pictures of the spots after
       the pbar mirror was moved in.  He described
       the two peak phenomenon.  He stated that the
       actual distributions are a convolution of
       light from the two( maybe three) edges, the
       body of the full dipole, and possibly reflections.
       This sparked considerable discussion. There seemed
       to be some consensus that the two peak behavior
       is what would be expected.  The two peaks are
       light from the end of the 1/2 dipole and the
       beginning of the full dipole.
    2. Sasha pointed out that the distance scales measured
       when the orbits are moved now agree with expectation
       and are the same for p and pbar.
    3. Sasha pointed out that the two mirror positions
       are consistent with light from the edges and
       light from the body.  Body light comes from a small
       region in the middle of the full dipole.
    4. Randy had plots showing the ratio of the pbar intensity
       as measured by SL and by the SBD for 3 bunches as a
       function of time, intensity and SL sigma. The ratio
       depends on the bunch.  There is about a 4% change in
       the ratio for the 12 hours of this store, so things are
       not crazy.  Since sigma and intensity both change smoothly
       with time in the store, it's hard to get the actual dependence
       from these plots.
    5. Sasha compared the H and V emittances as measured by
       synclite  with those measured by flying wires at the
       beginning and end of the store for pbars for the 36
       bunches. He subtracted from the sigmas an amount such
       as to make the intercept 0 when plotting synclite
       versus flying wires emittances.  The slopes in all 4 cases
       are a factor of 2 two large, explained after the meeting by
       the extra square root of two in the SL3 code.
       The offsets are the same for H and V, but different for
       the beginning and end of the store.  It was speculated
       that subtracting from sigma squared would make these the
       same. The same square root of two also makes these offsets
       too big.
    6. There was a long discussion of the offset, which is probably
       due to diffraction.  A quick estimate by Valeri gave a
       reasonable value but larger than that quoted
       by Alan Hahn - remember the square root of 2 error!
       Sasha said he was corresponding with Timur Shaftan of BNL
       who has a code to calculate the optics, including
       diffraction of systems like ours.  Timur is doing it for
       synchrotron light source applications.  Once Sasha gets the code
       he'll do the estimate.