[Varun, Jenne, Georgia, Craig, Brad, Austin, Camilla, Keita, Richard]
Next up: On/Off tests with some of the cleanrooms (when okay with other teams), and other low frequency noise improvements (such as checking and tuning the MICH and SRCL LSC FF if needed).
Richard has turned many cleanrooms off for a few minutes, which has dramatically improved things, and revealed some other scattered light shelves and / or acoustic peaks (note that the pump carts are still on). So, we've clearly got some work to do in working on our low freq noise, but it's still very exciting that we're close enough to start looking for these things!
[Georgia, Craig, Austin, Varun]
HAM5 and HAM6 ISI shaker test results coming soon in Georgia's alog!
BOOM!
Follow up from yesterday's power trend plots in alog alog 62347, addressing the short lock we had from 2021. Now the 2021 lock is six hours of data, and is compared to six hours of data from today. 0) We have about the same amount of light incident on the PRM (40 W). 1) It does seem like POP18 decays with thermalization far more than it used to. 2) REFL LF never achieves the heights it once did. 3) Thermalization agrees with carrier buildup. 4) POP90 looks better than before.
Because we were seeing scattering shelves, I wrote a uncalibrated DARM spectrogram maker in python quickly,
It's in https://git.ligo.org/aligo_commissioning/labutils/-/tree/master/spectrograms with some instructions for how to run it.
On CDS machines it's in /ligo/gitcommon/labutils/spectrograms/
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I only plot between 10 and 450 Hz, because otherwise the violins drown out everything.
The main takeaway from these plots is how stationary the scattering shelves are. The peaks rise and fall by about a factor of 2 or so, but are always present.
We have been thinking about output optics mostly, because of the OFI problems at Livingston. We should perhaps be suspicious of our input optics and the new PSL.
Posted first is an example from when Georgia was moving AS_C offset in pitch. We went to a bad place, as seen by some of the glitches across the band, then she moved back and recovered the "quiet" noise.
Posted second is from when McCarthy turned the mega clean room back on. The noise humps above 100 Hz returned, but the low frequency stuff remains about the same.
I just turned the SR3 yaw walk around since it seems like it's making the range worse. It will step down to an offset of -247.3.
We lost lock during the SR3 yaw move, it's hard to tell exactly what happened but there looks like a 0.43Hz ringup in the test mass oplevs.
While moving SR3 the noise in DARM got a bit worse (see attached spectrum). When we're locked later in the week maybe we cna try a SR3_P walk. SR3 is back in it's origianl position.