[BTeam] Injector BPMs (an observation)

[Christopher Tennant]

Thanks for all the good feedback Joe! Re-taking the data shouldn't be too difficult and you bring up some interesting items to check.
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From: Joe Grames <grames at jlab.org>
Sent: Tuesday, September 14, 2021 3:59 PM
To: Christopher Tennant <tennant at jlab.org>; bteam at jlab.org <bteam at jlab.org>
Subject: Re: Injector BPMs (an observation)

Hi Chris,

That's interesting, first time to see it, thanks for sharing.

You clearly found a topic near and dear, here are some thoughts, I guess you have thought of them already, but just in case...

  1.  Maybe consider proximity of each steering coil to nearby magnetic steel, then plot beam displacement (from your plot) vs. proximity to nearby magnet, look for a correlation
  2.  I might be treading into the deep water here, but our PQB colleagues operate the BPM's in fixed gain mode to avoid pedestal variations when the beam intensity changes.   Even if the current returns to original value after varying a steering coil, perhaps it doesn't.   I assume as you move the beam, the gains are changing, so how well they return.   => repeat test in fixed gain?
  3.  We know that in the past we've suffered from charging up components in the beam line, which can be collected when beam is dumped (reflected) and it doesn't take too much accumulated charge on a screen or isolated part.
  4.  and maybe related to #3, would be interesting to see size of discrepancy when you excited the corrector by say 50% or 25% as much, e.g. to ensure beam wasn't lost (which maybe you did!)  i should make assumptions
  5.  cross-talk in trim cards, look at correlation of adjusted trim with current readbacks​ of other nearby trims
  6.  Clearly a sign you produced Transformium.

Joe

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From: BTeam <bteam-bounces at jlab.org> on behalf of Christopher Tennant <tennant at jlab.org>
Sent: Tuesday, September 14, 2021 3:46 PM
To: bteam at jlab.org <bteam at jlab.org>
Subject: [BTeam] Injector BPMs (an observation)

Hi all,

Not sure if this is of interest to anyone, but just wanted to throw it out there...

For a recent SBIR project we (Brian, Daniel, Reza and I) collected and analyzed data from the injector. Specifically, last fall we varied beamline components (solenoids, correctors, RF gradients) and recorded the downstream response (BPMs, BCMs, BLMs, vacuum). I'm sharing the results of analyzing the BPM data which is in the attached slides.

slide 1: For this portion of the beam studies correctors were varied and the downstream response recorded. What is plotted here is the horizontal (top) and vertical (bottom) BPM readings after the corrector being varied has been returned to its default value. That is, each marker in these plots represents the injector with the exact same corrector settings. (Note, the BPMs were allowed to settle, and an average reading was taken). The extent of the vertical smear at each BPM displays the system reproducibility (or lack thereof).

slide 2: This represents an alternate way to view the information from slide 1. Here the standard deviation of the measurements at each BPM are plotted.

I was rather surprised by these results, though perhaps for those more familiar with operations, this is expected (?).

--chris
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