Log entry time 20:26:06 on April 01, 2010

Entry number 315556

Followups:

• 315559 04/01/10 20:37 R. Michaels tune B and "final" septum set

The present idea is to tune the septum current such that hole 'A' in the
figure below is about 4.8mm from the acceptance edge (which is the hole
spacing).  From the BPM scan done in the referenced post, this hole
disappears when the beam is shifted between 3-3.5 mm in the appropriate
direction, suggesting that if the hole is moved an additional 1.6mm, it
will be appropriately far from the edge.

To effectively move the hole we can change the septum current, and by
using the relative hole spacing as a guide on the distance scale, we can
map current change to effective hole position change.  6 mrad in target
phi is about the spacing between the central hole and hole A, Fig 2. 
Figs. 3 and 4 are how the central hole peak position changes in target
phi vs. current, which is nicely linear.  Taking the slopes from the
figures, I get an increase by 8 A for the left arm and 10 A in the right
arm corresponds to a shift of 1.6mm.

So, increasing the septum by 9 A should move the holes the additional space.

Figure 1

Figure 2

Figure 3

Figure 4