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 coating absorption in ITMY and 216mW of coating absorption 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. 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!

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.

Kar Meng, Sheila

About 45 minutes after locking, we turned on the AS42 WFS to track the squeezer alignment while we stepped the ZM5 PSAMs from it's nominal value of -0.4 to -4.5V on the strain guage.  ZM4 is left at it's nominal value of 6.2V.  We doubled the ASC gain to 1 to speed this up, and stepped the psams by 0.5 V at a time waiting for the ASC to catch up a bit between steps. 

After the 42 MHz WFS signals were close to zero at our target psams value, we turned them off and ran SCAN_ALINGMENT, results are here: https://lhocds.ligo-wa.caltech.edu/exports/SQZ/GRD/ZM_SCAN/251117100527/, after that we ran scan sqz angle, results here: https://lhocds.ligo-wa.caltech.edu/exports/SQZ/GRD/SQZANG_SCAN/SQZANG_SCAN_251117101454.png

Then we started a script to move the squeezing angle.  I forgot to turn off the SQZ angle adjust servo for the first 15 minutes of the script, so this data isn't very useful since the ADF servo was running.  Now I've added a reminder to the script if it sees that is on. 

The squeezing angle that scan alignment found to be best was 167 degrees (CLF RF6, servo sign negative), it was at 159.7 from 1447439668 to 1447439844 (2 minutes 27 seconds).  

Went to 167 degrees at 1447442247, then no sqz at 1447442524.  

NLG measurement: amplified max: 0.0198 (drifted down to 0.186) minimum: 0.0007, unamplified 4.9e-5

To restore squeezing we had to trend the osems (once the ASC was cleared and the psams were back to nominal settings), to avoid this in the future we should offload the ASC before we start a psams move. 

Here is the log of times of demod 6 changes from the script:

167.1 : 1447438644.0 
177.1 : 1447438884.0 
172.1 : 1447439124.0 
162.1 : 1447439364.0 
157.1 : 1447439604.0 
200.0 : 1447439844.0 
177.8 : 1447440084.0 
155.6 : 1447440324.0 
133.3 : 1447440564.0 
111.1 : 1447440804.0 
88.9 : 1447441045.0 
66.7 : 1447441285.0 
44.4 : 1447441525.0 
22.2 : 1447441765.0 
0.0 : 1447442005.0 

Mon Nov 17 10:11:48 2025 INFO: Fill completed in 11min 45secs

Gerardo confirmed a good fill curbside.

15:35 UTC lockloss, it appears to have been an ETMX glitch.

TITLE: 11/17 Day Shift: 1530-0030 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Observing at 145Mpc
OUTGOING OPERATOR: Tony
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 3mph Gusts, 1mph 3min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.33 μm/s 
QUICK SUMMARY:

• We've been locked for almost 22 hours
• Microseism looks to be maybe creeping back up a little
• Site's a bit foggy this morning

TITLE: 11/17 Eve Shift: 0030-0600 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Observing at 146Mpc
INCOMING OPERATOR: Tony
SHIFT SUMMARY:

IFO is in NLN and OBSERVING as of 17:51 UTC (12hrs 30 mins!)

Extremely calm shift with stable microseism and low wind.

A message to OWL Ops from DAY Ops if you get called and we drop out of observing: Load ISC_LOCK guardian (confirming changes from DAY shift).

LOG:

None

Closes FAMIS 27572. Last checked in alog 87988

MR_FAN1_170_1 and MR_FAN1_170_2 were increasing rapidly and approaching the cutoff of 0.7, but it appears they were turned off last Tue during maintenance (Ryan C reports that he and TJ saw this and told facilities). This was also reported in the last FAMIS alog for these fans. Counts are 0 for this plot. 

MR_FAN6_170_1 is increasing very slightly but still under 0.2 cts.

All other fans look good. Plots attached.

TITLE: 11/17 Day Shift: 1530-0030 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Observing at 145Mpc
INCOMING OPERATOR: Ibrahim
SHIFT SUMMARY: I shuffling around a bit of code in LOWNOISE_ESD_ETMX to hopefully stop the locklosses the states is inducing. We've been locked for a little under 7 hours.
LOG: No log.

• 16:14 UTC LOWNOISE_ESD_ETMX lockloss
• 17:51 UTC Observing
  • I editing the LOWNOISE_ESD_ETMX state, I added a timer equal to the bias ramp time, and moved the troublesome lines from the main method to the end of the run method after the bias has finished ramping. I again forgot to reload ISC_LOCK before returning to Observing. Starting at line 5516 in ISC_LOCK.py:

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.

[Jenne, Alicia, Joan-Rene, with suggestions from Sheila]

Today we tested using ETMY to transition the ETMX ESD, rather than the usual locking procedure of ITMX.  I had checked on the guardian code for this last week, alog 87997.  It worked!  The first time we tried transitionining back to ETMX, we lost lock, but the second time that also worked.  We are currently locked at NLN and observing, having gotten here using ETMY and not any stages of ITMX for the ESD transition. This means that we're ready to try grounding the ITM ESDs, to see if that helps reduce the combs that Alicia and Joan-Rene have been investigating. 

• The first time we tried locking, we went through the state LOWNOISE_ESD_ETMY by hand, so that we could transition ETMX -> ETMY slowly and measure the DARM loop along the way.  
  • We measured the DARM open loop gain before any transitioning, then after 25%, after 50%, after 75%, and after we were fully on ETMY.  See attached plot with the measurements labeled on the right side with percent of actuation on ETMY.
  • When we tried to transition back ETMY -> ETMX 25% of the way, (doing the state LOWNOISE_ESD_ETMX by hand), we lost lock.
    • After looking through the settings, it could be that the ETMX L1 Lock L filter bank wasn't set correctly (FM2 not on), even though I see that in my guardian shell I told it to turn on. 
    • Or, as Sheila points out to us, it could be that this transition back to ETMX is rather delicate, and we're going from using 2 stages of the temporary (ETMY) suspension to 3 stages on low noise ETMX, and we just can't do that part way.  
• The second time we tried locking, we let the guardian go through LOWNOISE_ESD_ETMY, which was successful.  We also checked that the ETMX L1 LOCK L filter bank was set up correctly. Since we were worried about going partially back to ETMX being delicate, we just ran the LOWNOISE_ESD_ETMX state to ramp all the way back to ETMX at once, and that was also successful. 
  • It turns out that I had forgotten that we'd need to disable the ETMY L3 Length actuation after we were done using it, since ETMY is used as part of our LSC FF actuation path, and that signal is only supposed to go to L2.  We had a funny bump in the DARM spectrum, and also some SDF diffs on ETMY that helped us find that easily.  
  • I have added (but not tested) a few lines in LOWNOISE_ESD_ETMX to reset the ETMY L3 settings to match the Observe.snap SDF, which should also fix the lump from improper feedforwarding. 

As of now, the guardian is set to acquire lock still using the nominal ITMX ESD.  So, before we ground the ITM ESDs we'll need to modify the weights in the guardian path, to make it so that the nominal path uses the ETMY and not ITMX.

Here is how the PR3 and SR3 signals show up at various ports.

I drove a pitch line from PR3 M3 and SR3 M3 at 8.125 Hz with the ASC notches on. I was able to see at signal with a 10 ct drive on PR3 pitch and 60 ct drive on SR3 pitch.

Templates saved as {PR3,SR3}_M3_injection_all_ports.xml in /ligo/home/elenna.capote/POPX_test in case the data is useful to you.

PR3 appears strongly at REFL and POP in I and at AS in Q. SR3 appears strongly at AS in Q and POP in Q.

Will try to repeat for yaw.