[BTeam] Matching small β functions using centroid jitter and two beam position monitors

[Jay Benesch]

Can this method for measuring Twiss parameters with beam jitter be 
adapted to our very different scale?  A non-invasive alternative to 
RayTrace, perhaps.  Each Hall has at least two BPMs after the last quad.

And for tuning purposes, I wonder if we should consider a "BPM ladder" 
after each target chamber, meaning a BPM on a vertical motion mechanism 
that can be placed on axis (no target) to make such measurements easier. 
  Perhaps with a YAG viewer on ladder too.   If symmetric in space with 
one upstream of target, relatively easy for Ops to get the size the same 
on both viewers, so minimum is at target.  Or to make it clear Ops needs 
APEL intervention.

Parity experiments, including PREX/CREX, install what they call SAMs, 
small angle monitors, into the downstream beam pipe via dedicated 
round-bottom tubes.  SAM is in air.  If these intrusions can be 
tolerated from a radiation and backscatter perspective, I see no reason 
why a retractable BPM or YAG would cause any difficulty.
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