[Bteam] arc dipole multipoles

[Jay Benesch]

Attached please find an updated version of my spreadsheet on arc dipole 
multipoles.  I have reproduced the work Nicolas did and established to 
my satisfaction that calculating multipoles on circles normal to the Z 
axis gives the appropriate result when summed along the particle 
trajectory.  These results are labeled "Z_norm" on the summary 
worksheet, the first.

Attempting to correct the orbit_normal values with the geometric factor, 
l/R^2, doesn't work precisely because I summed along particle trajectory 
rather than a straight line followed by an arc of a circle.  It's not 
bad, but there is a discrepancy which vanishes when exactly the same 
points are used for all sums.

I haven't tried to figure out whether my "Z_norm" numbers contain the 
edge focusing.  Comments solicited.

It should be noted that quadrupole and sextapole values are close to 
each other so B'L/BL is NOT dominated by quadrupole.  I am told that the 
measurements are too noisy to fit a parabola so as to resolve quad and 
sext.

I'll write up a TN sometime soon, including comparison with the 4-300A 
numbers Harwood provided.

Jay
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