Camilla, Nutsinee, Sheila
Screenshot of different sqz angles attached. Nutsinee's final attachment compares sqz with two different CLF servo signs.
We offloaded IFO ASC and used "Save ZMs IFO" script to save the ZM settings that we found.
We moved the ADF back to 1.3kHZ as think the 322Hz ADF we used eariler is impacting the range.
Attachment 1 - looking for freq-dep SQZ loss/rotations. Here we fit a common model of frequency-dependent losses and rotations to all squeeze angle spectra simultaneously. FIS data would probably clean this up at low-frequencies, maybe removing the ~20 Hz anti-sqz bump.
Dots + thick lines = subtracted sqz data, with a moving average for clarity. Thin line = common fit model. Equations in the plot title. For each frequency bin \Omega, we fit the loss(\Omega) and the sqz angle offset theta(\Omega) given the \phi_0 for the dataset. The fit to all sqz angle spectra is done independently for each frequency bin.
This dataset suggest higher freq-dep losses at low frequencies in-band, but before we typically we had lower freq-dep losses below darm pole, e.g. Fig. 3 of the O3 quantum response paper (P2100050). I'm not really sure yet how to interpret this, and don't think there's a clear expectation for one way or another. As a basic sanity check, I compared another time with anti-sqz from March 17 LHO:76434 (which had different PSAMS settings) - there, evidence for frequency-dependent losses at lower frequencies is weaker, but there is still some evidence for it.
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Attachment 2 - squeezing-related DARM comparison, O4a vs. pre-O4b. Blue/yellow = O4a. Purple/pink = pre-O4b. Interesting things (from a sqz perspective):
A comment regarding the excess noise - it seems clear that the excess mid-band DARM noise is not caused by / related to squeezing, because it's there even without squeezing injected. That said, squeezing seems to be having its own issues at these lower frequencies, below the DARM pole. Not clear how the worse low-frequency squeezing (after subtraction) could be a consequence of whatever causes the excess noise without squeezing. Likely different issues / things to be optimized happening at the same time/frequencies.
After PSAMS optimization with alignment scripts, it could be interesting to try a similar SQZ dataset with FIS.