TITLE: 10/24 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Corrective Maintenance
INCOMING OPERATOR: Ryan C
SHIFT SUMMARY: Busy day of continuous troubleshooting of H1. Things have been learned and progress has been made, but currently still waiting to relock after discovering an incorrect whitening setting and swapping a sat amp to see if those help with some of our instabilities. We've had some locklosses at DRMI_3F, but waiting for DRMI ASC to fully converge on this most recent try seemed to work. Currently relocking up to MOVE_SPOTS.

• 14:35 - Starting initial alignment
• 15:06 - Starting lock acquisition
  • Applied roll mode damping (G = -200) during LOWNOISE_LENGTH_CONTROL
  • Waited for 30 minutes to watch for roll mode ringups, saw none
  • Went through LOWNOISE_ASC once DHARD_P lownoise steps commented out (alog87712)
  • Saw 1 HZ ASC oscillation once at NLN, transitioned to high gain ASC configuration
• 17:03 - Lockloss after ~1:15 at max power with 5.8 Hz DARM "pulse" behavior (alog87717)
• Holding down for sat amp swap (alog87722)
• 17:38 - Starting lock acquisition
  • Applied roll mode damping (G = -200) during LOWNOISE_LENGTH_CONTROL
  • Skipped over LOWNOISE_ASC entirely
• 20:59 - Lockloss similar to before with ~1:15 at max power and 5.8 Hz DARM "pulse"
• Discovered incorrect POP A RF45 whitening setting, fixed (alog87728)
• 21:30 - Starting initial alignment
• 21:55 - Starting lock acquisition

LOG:

My first SDF post today, which was based on getting archive files from subversion commits, doesn't appear to be complete and in addition may have some false positives.

I have generated new lists, this time getting the archived OBSERVE.snap files from the CDS backups of userapps by the file server.

In the directory /ligo/home/david.barker/tuesdaymaintenance/24oct2025/sdf/observe there are:

mon20oct2025/ Directory of backups as of 00:39 early monday morning

wed22oct2025/ Directory of backups as of 00:39 early wednesday morning

thu23oct2025/ Directory of snaps as of 00:39 ealy thursday morning

mon-wed_diffs.txt Text file of settings changed between the monday and wednesday backups

mon-thu_diffs.txt Text file of settings changed between the monday and thursday backups

snap_diffs.bsh Shell script to generate the diffs files

snapfiles Text file of the userapps "OBSERVE.snap" files as symbolically linked from the target directories

TITLE: 10/24 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Corrective Maintenance
OUTGOING OPERATOR: Ryan S
CURRENT ENVIRONMENT:
    SEI_ENV state: USEISM
    Wind: 9mph Gusts, 6mph 3min avg
    Primary useism: 0.04 μm/s
    Secondary useism: 0.53 μm/s 
QUICK SUMMARY:

• We've had 2 ~1 hour locks today, 2 locklosses so far
• Locking itself has been straightfoward, for the 3rd lock attempt we had to run the 2nd IA of the day
• Microseism seems steady around the 90th percentile
• Wind is low

We (Sheila, Jennie, Ryan, Oli) have found that the POP A RF45 antiwhitening gain was set incorrectly. We tracked this problem down to the SDF being saved incorrectly Monday night along with with various dark offsets (87598). The antiwhitening gain should be -15 dB but was set to -21 dB. Additionally, the new dark offsets were doubled. We think this problem explains why the MICH gain needed to be doubled this week (87645).

I reset the safe SDF to have the correct LSC POP antiwhitening filters, and reverted the dark offsets as well.

Extra kudos to Jennie for scrolling through Dave's SDF difference file (400 settings!) to find this mismatch, 87718.

Sheila edited the guardian to remove the MICH gain doubling.

Marc, Oli

In 87713 it's noted that some of the strange behavior we've been seeing with the locks seem to be related to the ETMY L2 stage. The ETMY L2 satamp was swapped out on Oct 14th from S1100137 to S1100127 as part of the ECR E2400330 upgrade (87469). So, even though we were seemingly doing fine with this ETMY L2 satamp, we decided to swap it out this morning to see if that is the cause of our issues. Coincidentally, the spare satamp that we have available that was modified for ECR E2400330 and that Jeff had characterized was the satamp that had come from ETMY L2, S1100137. So we decided to put that one back in - it was fine before, although it obviously has now been modified for the satamp upgrade. So it's not been swapped back to exactly what it was before, but this is the closest we can get!

Marc and I took S1100137 down to EY and swapped out S1100127 with S1100137. I edited the fitresults file for S1100137 to work for ETMY L2 and replaced the previous OSEMINF 5.3:0.1 compensation filters to be the best possible compensation filters for this new satamp. 

Updating compensation filters
$ py satampswap_bestpossible_filterupdate_ECR_E2400330.py -o ETMY_L2
All updated filters grabbed for ETMY
ETMY L2 UL compensation filter updated to zpk([5.25],[0.0959],1,"n")
ETMY L2 LL compensation filter updated to zpk([5.21],[0.0953],1,"n")
ETMY L2 UR compensation filter updated to zpk([5.18],[0.0949],1,"n")
ETMY L2 LR compensation filter updated to zpk([5.21],[0.0955],1,"n")
write /opt/rtcds/userapps/release/sus/h1/filterfiles/H1SUSETMY.txt
Done writing updated filters for ETMY

Swap timeline

Satamp characterization data

Here's the characterization data and fit results for S1100137, assigned to ETMY L2's ULLLURLR OSEMs.

This sat amp is a UK 4CH sat amp, D0900900 / D0901284. The data was taken per methods described in T080062-v3, using the diagrammatic setup shown on PAGE 1 of the Measurement Diagrams from LHO:86807.

The data was processed and fit using ${SusSVN}/trunk/electronicstesting/lho_electronics_testing/satamp/ECR_E2400330/Scripts/
plotresponse_S1100137_ETMY_L2_20251020.m

Explicitly, the fit to the whitening stage zero and pole, the transimpedance feedback resistor, and foton design string are:

The attached plot and machine readable .txt file version of the above table are also found in ${SusSVN}/trunk/electronicstesting/lho_electronics_testing/satamp/ECR_E2400330/Results/
2025-10-20_UKSatAmp_S1100137_D0901284-v5_fitresults.txt

Per usual, R_TIA_kOhm is not used in the compensation filter -- but after ruling out an adjustment in the zero frequency (by zeroing the phase residual at the lowest few frequency points), Jeff nudged the transimpedance a bit to get the magnitude scale within the ~0.25%, shown in the attached results. Any scaling like this will be accounted for instead with the absolute calibration step, i.e. Side Quest 4 from G2501621, a la what was done for PR3 and SR3 top masses in LHO:86222 and LHO:84531 respectively.

Fri Oct 24 10:10:02 2025 INFO: Fill completed in 9min 58secs

To continue with the "what has changed since Monday" I have created the SDF reports. For now I've just concentrated on the OBSERVE.snap settings changes.

Models with changed settings over this time period: h1alsex  h1alsey  h1asc  h1ascimc  h1iscex  h1iscey  h1isietmy  h1lsc  h1omc  h1suspr3  h1sussr3

There are approximately 400 settings changes.

Full details available in /ligo/home/david.barker/tuesdaymaintenance/23oct2025/sdf/observe

We had a lockloss at 17:03 UTC that has the same "pulse" behavior noted by Jennie and Oli yesterday. This pulses can be seen in the DARM loop, on the L3 master out, and in the EX and EY L2 master outs. These pulses are about 5.8 Hz in frequency.

I'm going to use this post to keep running notes of the 1 Hz investigations:

• After being at high power for more than 30 minutes, we went to low noise and left DHARD P in its high bandwidth configuration.
• After some minutes, the 1 Hz oscillation appeared in the ASC
• Indication that DHARD P is NOT the only culprit here
• I averted the lockloss by running the High Gain ASC script
• after the script completed I reengaed the LSC FF since that is not the issue here
• we had been at high power long enough that the CSOFT P gain was dropped to 20, and I can't change it because the thermalization guardian won't let me
• I measured DHARD P around 1 Hz with all ASC in high bandwidth
• DHARD P looks very stable at 1Hz, the phase is fine and there is no UGF at this frequency
• at 9:54 local I transitioned all the YAW arm loops to their low bandwidth state
• LOCKLOSS at 10:03- no oscillations, no saturation warnings, just a "fast" lockloss

DHARD P at 1 Hz attached.

We have been getting saturation warnings on EY after going through the lownoise coil drivers state. We finally tracked it down to the R0 F2 and F3 drivers. The reaction chain length drive (aka reaction chain tracking) is causing these saturations. This servo is run using the L2 OSEMs as a witness to then drive the R0 chain to follow the main chain. I turned off the length drive and the saturations stopped. When I turn it back on it continues to saturate.

The only recent change I can think of is the L2 satamp swap on all the test masses.

Because we continue to have issues with the lownoise state of DHARD P (1 Hz ring up), I have commented out both DHARD P lownoise steps in LOWNOISE_ASC. This includes the engagement of FM4 (lownois reshape with low pass) and FM8 (boost). These steps are done separately. This means that we can safely run the LOWNOISE_ASC guardian state, there will just be a little more noise until we can resolve the DHARD P issues.

TITLE: 10/24 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Corrective Maintenance
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    SEI_ENV state: USEISM
    Wind: 8mph Gusts, 6mph 3min avg
    Primary useism: 0.04 μm/s
    Secondary useism: 0.62 μm/s 
QUICK SUMMARY: H1 was down overnight due to ongoing locking issues. I'll start by running through an initial alignment while I get caught up on events of the past couple days.

• Wind low, microseism steady around 90th percentile
• DR1 dust monitor reports no change in counts
• All other systems nominal

WP 12836
ECR E2400330
Modified List T2500232

The following SUS SAT Amps were upgraded per ECR E2400330. Modification improves the whitening stage to reduce ADC noise from 0.05 to 10 Hz.

F. Clara, J. Kissel, O. Patane