J. Kissel

The ETMs have L2 to R0 "tracking" in longitudinal (in addition to pitch and roll "damping") L2 sensing to R0 actuation. It's referred to as "tracking" rather than "damping" because the open loop gain is greater than unity over a much broader frequency region, focusing around 0.1 Hz.
These, like the P and R damping, didn't change after the sat amp swaps.

The templates to take this data lives here:
    /ligo/svncommon/SusSVN/sus/trunk/QUAD/H1/ETMY/SAGR0/Data
        2025-10-14_1830UTC_H1SUSETMY_R0_WhiteNoise_0p02to50Hz_L2DAMP_OLGTF_L.xml

    /ligo/svncommon/SusSVN/sus/trunk/QUAD/H1/ETMX/SAGR0/Data
        2025-10-14_1830UTC_H1SUSETMX_R0_WhiteNoise_0p02to50Hz_L2DAMP_OLGTF_L.xml

J. Kissel, S. Dwyer, E. Capote

We recently re-discovered that H1SUSPRM M3 DRIVEALIGN matrix has an L2P filter ON with gain of -1.36 that was designed in 2014 (see LHO:9589). Unsure of its function/performance with the modern IFO, we wanted to test turning it OFF. We turned it OFF (by ramping the gain in that bank to 0.0 with a 10 sec ramp time) at the end of the most recent lock stretch, with the IFO in nominal low noise (just after Elenna's calibration push; LHO:87520). Namely the IFO was suffering from a failed H1 SUS ITMY PUM sat amp, and we knew we needed to replace it, so we were looking for "useful" ways to break the lock.

Turning off the H1 SUS PRM M3 DRIVEALIGN L2P filter, at first superficial glance, has no impact on the IFO excpet for reducing the M3 pitch drive from +/- 300 to +/- 2 (Euler Basis) DAC Counts.

For more in-depth analysis, 
    - 2025-10-16 18:45 UTC the problems with the ITMY satamp started
    - 2025-10-16 19:54 UTC we turned off the PRM M3 L2P filter, and
    - 2025-10-16 20:02 UTC I caused the IFO lock loss by inverting the polarity on IN2 of the IMC common mode board.

So, we should have a good 5 minutes of time right before vs. right after to compare ISC ASDs.

We also tried this next lock acquisition with the filter OFF, to see if it's still needed for lock acquisition.
PRMI isn't locking after 10 minutes of trying (*after* going through MICH fringes), though we did NOT run an initial alignment prior to this lock attempt and the AS port does look a little splotchy.
Turned it back on 2025-10-16 20:39:44 UTC, but pretty quickly decided to run initial alignment instead (by 2025-10-16 20:42:57 UTC).
We'll leave it ON and test more / again some other day; we'd rather get back to observing.

Today I pushed calibration report 20251016T180834Z which was just taken in alog 87512. My motivation was due to what appears to be an incorrect kappa c value that I reported here 87453. We have also moved the beam spot on ETMY due to a camera bump, reported here 87473 and here 87508.

Note, I did not update the L3 drivealign gain in the model. That number is still changed in the actual suspension gain, but not in CALCS or in the pydarm ini file.

I also noticed that, maybe due to the beamspot change, there is an antispring present in the sensing function that maybe we should correct.

I followed the usual steps to commit, upload and export. I loaded the calcs model and accepted the SDF diffs. I confirmed things look good by checking the broadband measurement. Calibration is within +-2%. Kappa C is back to 1-ish. This is not as good as the Aug 28 push, but it's still pretty good overall.

18:45 UTC While Jim was running a measurement on ISI HAM5, SUS ITMY started to flash its' red Rocker Switch Death on L2 and report that its' L2 OSEMs were in fault, we also noticed there's a big new line at ~92Hz. Jeff turned off feedback from L2. It looks like it could be a sat amp issue, the L2 sat amp was upgraded this past Tuesday alog87469. Jeff is starting to work on characterizing a sat amp box in the EE shop to swap in. 

We would need a lockloss to swap this component.

We are going to try to go back into Observing for a bit until we can fix it or lose lock.

J. Kissel

This past Tuesday (Oct 14 2025), we upgraded the L2 (PUM) OSEM PD Sat Amps to improve their whitening filter, per ECR E2400330; see LHO:87469. These QUAD L2 PUM OSEMs (in which the flags are on the QUADs main chain PUM, and the LED & PD are on the reaction chain PUM [aka the "PenRe"]) are used in feedback. This "damping" of a "3.3" Hz reaction chain resonance is different ITMs and ETMs (ITM Install = LHO:65728; ETMs Install = LHO:68012 --- commissioning of both = LHO:68200); the ITM has resonances at 3.28 / 3.31 Hz and the ETM has modes at 3.18 Hz / 3.42 Hz.

Because the improved sat amps come with better compensation of the whitening filter frequency response, we know that the frequency dependent gain on each channel -- especially around 3.3 Hz may change by as much as ~10%. 

In the aLOG (and comments collection) I report 
    (a) That we *did* see a change in the open loop gain TFs of these loops, but (after ~2 days of observing since the upgrade) the IFO doesn't seem to mind the changes.
    (b) We were able to get better coherence on the open loop gain TFs in the 0.1 to 10 Hz region because of the sat amp whitening improvement
    (c) A comparison between all four QUAD's PITCH and YAW damping, so that we might understand them better and potentially improve them.

In this main aLOG I show the comparison between the PITCH and ROLL open loop gain TFs and loop suppression for all four QUADs.

Rushed commentary:
    - The surprising thing to me is that we're getting gain peaking and/or some suppression of other modes below 1 Hz, which I'm confident was not the design intent.
    - Even though the filters and EPICs gains are the same for EX and EY, ETMX has a lot more open loop gain below 1 Hz.
    - Also though the ETM loop suppression is about the same on these 3.18 / 3.42 Hz, the ITM loops have pretty different amount of gain peaking.
    - I'm guessing we *don't* want this much sharp gain peaking just *off* the "3.3" Hz mode.

Broadband:

Start: 2025-10-16 18:01:42 UTC

Stop: 2025-10-16 18:06:53 UTC

Files: /ligo/groups/cal/H1/measurements/PCALY2DARM_BB/PCALY2DARM_BB_20251016T180142Z.xml

Simulines:

Start: 2025-10-16 18:08:33 UTC // 1444673331.797786 GPS

Stop: 2025-10-16 18:31:47 UTC // 1444674725.604456 GPS

Files:

2025-10-16 18:31:47,448 | INFO | File written out to: /ligo/groups/cal/H1/measurements/DARMOLG_SS/DARMOLG_SS_20251016T180834Z.hdf5
2025-10-16 18:31:47,456 | INFO | File written out to: /ligo/groups/cal/H1/measurements/PCALY2DARM_SS/PCALY2DARM_SS_20251016T180834Z.hdf5
2025-10-16 18:31:47,461 | INFO | File written out to: /ligo/groups/cal/H1/measurements/SUSETMX_L1_SS/SUSETMX_L1_SS_20251016T180834Z.hdf5
2025-10-16 18:31:47,466 | INFO | File written out to: /ligo/groups/cal/H1/measurements/SUSETMX_L2_SS/SUSETMX_L2_SS_20251016T180834Z.hdf5
2025-10-16 18:31:47,471 | INFO | File written out to: /ligo/groups/cal/H1/measurements/SUSETMX_L3_SS/SUSETMX_L3_SS_20251016T180834Z.hdf5

Since we are still not happy with our buildups, I moved the ETMY beam spot again, following the assumption that this camera was bumped on Tuesday.

Instead of considering the A2L gains or ADS, I just chose to move the spot around by hand to make the buildups better. I did so slowly in pitch and then in yaw. Overall, the final camera offsets are P: -224 and Y: -346. This offsets brought the PRG up to 49.5 and the arm powers up to 380 "kW". I also noticed that this change brought the Y arm power up slightly about the X arm power, which is how it used to be before whatever happened on Tuesday.

Once the cameras converged on these new values, I ran the A2L script. This was a large beam shift for ETMY, so I had to run it a few times to get the script to cross zero for the ETMY lines. I would run it, guess where to go next, and rerun. Sheila pointed out to me that if you scroll up in the script output, it will tell you where it thinks the zero crossing is. I was able to use this to guess the final position. I reran one more time to see the script cross zero on all dofs, confirming that the A2L gains ended up in the right spot.

As a part of this, I was able to test TJ's new version of this script, /opt/rtcds/userapps/release/isc/h1/scripts/a2l/a2l_min_multi_sdf_cleanup.py

His script now does not leave SDF diffs, since it reverts all the tramps and matrices. However, when I cntrl-Ced, only half the lines turned off. It appears that cntrlC only turns off the matrix values for pitch, but not yaw, and it still leaves the clkgains and such in place. So the cntrlC capability needs more work. To get the scrpt to revert everything properly, you still need to let it fully run.

I updated the guardian lscparams to have these new ETMY A2Ls (P: 4.89, Y: 0.78) and camera offsets. I have loaded both the ISC_LOCK and the CAMERA_SERVO guardians.

While these A2Ls suggest that the ETMY spot has not ended up in the same place as before, I do believe this is a good place that gives us good buildups, so I think this is a fine spot to be in.

First run:

Second try I cntrl-Ced which sort of worked.

Third try: