We started installing electronics chassis for JAC:

• Heater driver, S2500960.
• DB9 breakout panel, S2500958.
• PZT driver, S2500954
• RF doubler: S2500737
• RF amp (was already installed)
• Two sat amps for JM1 and JM3

Still missing:

• Two 4-chn WFS demod chassis.
• Two AA chassis.
• JAC in-vacuum electronics interface chassis.

The necessary coax cables were also installed and terminated where possible.

The RefCav Refl spot was off this morning and the TPD had been trending down the last several days, so I took the opportunity to tweak the beam alignment into it from the Control Room.  The ISS was ON for this work.

When I started the RefCav TPD was ~0.520 V and when I finished the TPD was ~0.548 V.  I then noticed the ISS was diffracting ~4.5%, which is higher than its norm, so I adjusted the ISS RefSignal to -2.01 V from -2.00 V.  This brought the diffracted power % down to around its normal value of ~4%.  At this diffraction % the RefCav TPD is now ~0.550 V and the PMC Trans is now ~106.9 W.

I took the OPLEV charge measurements for both the ends this morning.

I ran into the same issue as had previously with ETMX constantly saturating no matter what amplitude I used. Jeff suggested I look at the biases and see if they're correct, the biases used for ETMX were [-9, -4, 0, 4, 9] and I changed them to [-8. -4. 0. 4. 8] in ESD_Night_ETMX.py which stopped the overflows. I then had to fine tune the amplitude (too low, bad coherence), through the first measurement, amplitudes of 10000, 12000, and 20000 wasn't enough, I ended up at 100,000 which gave me the best measurement I've seen in month. LR did still have some big error bars, the charge is high on LR, and UR but looks low at UL and LL, and the recent trend actually looks to be decreasing, looking at the year long trend it actually looks fairly stable considering the massive error bars on a lot of the measurements. Every quadrant is under + 100 [V].

ETMY also initially had some saturations but reducing the gain by 20% stopped them and still yielded good coherence. ETMY's charge is slightly high, it's just under + 100 [V] on 2/3 of the quadrants, UR is the only quadrant below +/- 50 [V], it has risen since May, but zooming out to the whole year it doesn't look to have much of a trend, May wasn't a great measurement.

M. Todd, J. Wright, S. Dwyer

Here is my attempt to summarize as many of the OMC scan measurements of the input beam overlap with the OMC mode, as well as PRC and SRC gouy phases -- all at different thermal states.

Tue Nov 18 10:11:33 2025 INFO: Fill completed in 11min 30secs

Famis 27573 Vibration Sensors To Gauge Health Of HVAC Fans Site 

H0:VAC-MR_FAN6_170_1_ACC_INCHSEC seem to be going up in that few days especially the last 24 hours.
This is also the case for H0:VAC-MY_FAN2_270_2_ACC_INCHSEC in the last day saw a fairly large increase in noise.

1616UTC rebooted the h1guardian1 machine. This was originally to switch over nds1, but Erik informed me that we had already done this some time ago. Since we already had a WP in and this seemed like a good time to do it, I went for a reboot anyway.

All nodes came back up on their own, no issues seen.

TITLE: 11/18 Day Shift: 1530-0030 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Calibration
OUTGOING OPERATOR: Ryan C
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 4mph Gusts, 2mph 3min avg
    Primary useism: 0.04 μm/s
    Secondary useism: 0.46 μm/s 
QUICK SUMMARY: Locked for 22 hours, SUS charge and PEM mag. injections running now. Maintenance today, then PEM measurements for the rest of the week, because....

O4C will end in 30 minutes. What a great run! Well done everyone!!

M. Todd, S. Dwyer

I've been polishing up the analysis of models estimating the various couplings of TCS powers to substrate and surface defocus in the test masses. This can be used to test the validity of the HWS estimate of the absorption in the ITMs. For reference, assuming the HWS are correct in their calibration of what the substrate defocus is in the test masses [ITMY = 63.5uD, ITMX = 54.5uD], and that my model is right estimating the absorbed Watts of power from substrate defocus [250 uD/W], then we have rougly 254mW of absorbed power in ITMY and 216mW of absorbed power in ITMX. Naively this seems too much, but I wanted to see if this could be consistent with measurements of the arm cavity Gouy phase.

We have fully thermalized HOM spacing measurements from the OMC DCPDs which can be translated into absorbed power estimates if you know how the Ring Heaters and how they couple to defocus. Models have yielded great agreement with the measurements of this coupling (previous conventions were not consistent with proper radius of curvature relation to defocus, but a technical note should hopefully be linked soon). Then, if we use the absorption derived from the HWS estimates, with an arm power of 345kW (average of Sidles-Sigg mode inference and arm gain inference), as well as coupling factors from my modeling we would infer ETM absorptions: ETMX abs: 0.228ppm and ETMY abs: -0.255ppm. For comparison, the galaxy estimates are 0.21ppm and 0.20ppm, respectively. This indicates that the ITMX HWS may be fine, but that the ITMY HWS may be miscalibrated. 

If instead, we assume ETM absorptions reported by galaxy, then the HOM spacing measurements would suggest ITM absorptions: ITMX abs = 0.678ppm, ITMY abs = 0.321ppm, half of what the HWS on ITMY reports. Some evidence that may support this is turning the CO2s off separately after the IFO cools off, where ITMY HWS reports twice the defocus as ITMX HWS -- unless there is some gross misalignment of CO2X the values should not be very different given the same CO2 power. I do not have any models of this to corroborate this but it is interesting (the HWS SLED was just replaced for ITMX).

I am not well versed in HWS code and I'm not totally sure how these values of defocus are calculated from the deflection of each partitioned beam but these errors may be mis-identification of the position of the centroid. More thought is needed!

This is a table of parameters describing the various coupling factors from the modeling. Note that the values for the ring heaters are assuming perfectly efficient ring heaters, which have previously been estimated to have an efficiency of around 75%, though the cold IFO HOM spacing measured with the SQZ dataset suggests the ring heater efficiencies are actually much closer to 100%. 

This is a summary table using the above modeled parameters

TITLE: 11/18 Eve Shift: 0030-0600 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Observing at 145Mpc
INCOMING OPERATOR: Ryan C
SHIFT SUMMARY:

IFO is in NLN and OBSERVING as of 19:46 UTC (12 hr 40 min lock) - last time I will be writing this for a while.

Extremely calm shift and well behaved interferometer on the last EVE of O4. Wind looks great and microseism is stable.

Wishing the OWL ops a smooth shift and some more spacetime ripples.

LOG:

None

TITLE: 11/18 Day Shift: 1530-0030 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Observing at 146Mpc
INCOMING OPERATOR: Ibrahim
SHIFT SUMMARY: One lockloss with an easy relock after running IA. We've been locked for 7 hours, Happy last day of 04!
LOG:

• 15:41 UTC IA
  • The IMC lost lock going from GREEN_ARMS to INPUT_ALIGN then struggled to relock after INPUT_ALIGN, it took ~ 7 minutes to relock.
• 17:17 UTC NLN and commissioning
• 19:46 UTC Observing
• 21:38 UTC Superevent S251117dq

TITLE: 11/18 Eve Shift: 0030-0600 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Observing at 146Mpc
OUTGOING OPERATOR: Ryan C
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 8mph Gusts, 6mph 3min avg
    Primary useism: 0.03 μm/s
    Secondary useism: 0.30 μm/s 
QUICK SUMMARY:

IFO is in NLN and OBSERVING as of 19:46 UTC (6hr 45 min lock)

Wind is good. Microseism is ok.

Expecting a calm shift for post-O4's eve EVE.

RyanC, Rahul

I have finished the assembly of two Tip Tilt suspensions (HTTS D1001396_V3), and both of them will be used for Jitter Attenuation Cavity (JAC) for O5 run. These two Tip Tilt suspensions (see two pictures of the finished assembly over here - view01 and view02), named as JM1 and JM3 will be installed in HAM1 chamber in Dec-Jan 2025/26. Give below are the details about the assembly,

1. Wire diameter - 0.0017in or 43 microns (purchased from California Fine Wire company in 2025).

2. Mirror used on JM1 (identified by D1000768_v2 s/n4) -  E1900393_V1_02 s/n 16, AOI = 45 degrees

3. Mirror used on JM3 (identified by D1000768_v2 s/n28) -  E1900393_V1_02 s/n 09, AOI = 5.07 degrees

Details about mirror characterization work is posted in LHO alog 88040.

Both JM1 and JM3 optics have been suspended and coarse balanced, both in pitch and yaw. I will fine tune it once they are plugged-in for electronics testing. 

Wire pulling jig (D1100735_V1) - we faced some issues when we tried using the wire pulling jig - issue captured in this document. I have handed over D1100732 to Tyler for re-work. However, this was not a show stopper as TJ showed us how it was done before (see LLO alog 36765, Nov 2017) and we recreated it - see here for details (using mirror holder with the bottom wire clamp). Also, we have created the intentional wire offset (to compensate for the heavy optic pitching up) on the wire clamps to counterbalance the optic. We have also used a bigger pitch adjuster to give us more dynamic range.

Both the suspensions have their Bosems (four each) attached and next we will connect it to the test stand and start performing SUS health checks. 

I've updated the in-lock charge measurements to start 5 minutes earlier tomorrow morning, changing the start time from 7:45am to 7:40am PT.

These measurements have been finishing either right at 8:00am or 8:01am PT recently, so moving up the start time should allow us to be back in observing mode right up until the very end of the O4 run at 8:00am PT tomorrow morning. The magnetic injections have been finishing at either 7:39am or 7:40am PT, so especially considering ramptimes, I don't expect there to be any overlap issues.

The SUS_CHARGE Guardian has been saved and loaded with this change.

FAMIS 31112

Between 2 and 3 days ago, there were some quick temperature spikes seen in the diode and chiller rooms, which seem to have propagated through to the diode boxes, amplifiers, some pump diodes, and eventually the PMC power. Not sure what caused this or if we've seen them before, but these jumps appear to have stopped and things are running smoothly.

I took another round of No BRD vs. BRD measurements for the BBSS BRDs, this time with a higher resolution.

Plots attached, including a comparison slide, on which the damped configuration (BRD installed) is the bottom picture.

Note that in the BRD-installed Roll screenshot, the line at the mode is just the cursor.

Ibrahim, Betsy

BBSS Eliptical Baffles (D2500293) were successfully installed today. Pictures from various angles are attached.

Problems - graphics regarding these are attached as slide screenshots

• D2000483 Type 2 - 12 O'Clock Baffle Brace
  • LHO did not recieve coated parts for this*, but it does not seem like this part is visible due to the baffle itself.
    • Note*: LHO recieved one coated part weeks after ours had gone into C&B so wasn't part of same set/load - either way missing one coated.
  • This part is extremely difficult to install due to poor sighting and no room. The screw that fastens this part has to be installed from behind the figure 8, where there isn't even enough room to fit the width of a 9/64 allen wrench. A combination of tweezers, wrenches, bent T-wrenches were used and we finally got it in. However, we could not tighten much in the case of the back.
  • Potential Fix: The sides of that thru hole have free thru holes that could fit another bracket instead of the 12 O'Clock one (~11 and ~1 O'Clock).
• D2000483 Type 1 - 6 O'Clock Baffle Brace
  • Helicoil call-out is incorrectly 1/4-20 X 1.5D but using those results in the helicoils bottoming out and appearing proud. So, removed and used 1D instead - it works. Will redline
• D1900594 V10 Mounting Bracket
  • 2 of these were too long to fit into its recessed spot in the Lower Structure, which seemed like a machining issue (barely 0.2 mm if I had to guess). To fix this, betsy and I filed off the problem surfaces until they fit. The filed surface is a mating surface and we used a clean-file.
  • Part incorrectly called a wire baffle - will edit DCC and redline

Remarks: I added one of those coated screw caps to the Y-Brace (D1900589) strut fasteners since I could see it shining in the head on picture. Comparison pictures for this are below.