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sheila.dwyer@LIGO.ORG - posted 09:20, Monday 06 May 2024 - last comment - 09:10, Monday 13 May 2024(77641)
DRMI PRCL gain change

Sheila, Jenne, Tony, Camilla

We've had locklosses in DRMI because the PRCL gain has been to high when locked on REFL1F.  Tony looked and thinks that this started on 77583, the day of our big shift in the output alignment.

Today we acquired DRMI with half the gain in the PRCL input matrix for 1F, this one acquisition was fast.  I've attached the OLG measurements for PRCL and MICH after the change. 

Tony is working on making histograms of the DRMI acquisition times, before the 23rd, from the 23rd to today, and eventually a histogram from today for the next few weeks to evaluate if this change has an impact on the DRMI acquisition times.

Jenne also found that it seems out POP18 build up seems higher in DRMI since the 23rd.

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jenne.driggers@LIGO.ORG - 11:45, Friday 10 May 2024 (77763)

I'm no longer quite so sure about the conclusion that Pop18 is higher, or at least enough to really matter.

Here are 2 screenshots that I made extremely quickly, so they are not very awesome, but they can be a placeholder until Tony's much more awesome version arrives.  They both have the same data, displayed 2 ways.

The first plot is pop18 and kappaC versus time.  The x-axis is gpstime, but that's hard to interpret, so I made a note on the screenshot that it ranges from about April 20th (before The Big Shift) to today.  Certainly during times when the optical gain was low, Pop18 was also low.  But, Pop18 is sometimes high even before the drop in optical gain.  So, probably it's unrelated to The Big Shift.  That means that the big shift in the output arm is not responsible for the change in PRCL gain (which makes sense, since they should be largely separate).

The second plot is just one value versus the other, to see that there does seem to be a bit of a trend that if kappaC is low, then definitely Pop18 is low.  But the opposite is not true - if pop18 is low kappaC isn't necessarily low.

The last attachment is the jupyter notebook (you'd have to download it and fix up the suffix to remove .txt and make it again a .ipynb), with my hand-typed data and the plots.

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sheila.dwyer@LIGO.ORG - 09:10, Monday 13 May 2024 (77805)

I actually didn't load the guardian at the time of this change, so it didn't take effect until today.

So, we'd like histograms of DRMI acquitisiton times from before April 23rd, from April 23rd until today, and for a few weeks from today.

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