Bi-Weekly ISC Locking Histograms. 
I turned this into a 1 click button to make these plots: Sitemap-> OPS-> WEEKLIES-> ISC Histograms. 
Once it runs (should only take about 15 seconds) the terminal tells you where to find the plots,  just upload the plots into your alog.

 

We run the Prep_for_Locking state before SDF_Revert, and Sheila and others have wondered how much of that state gets reverted during SDF_Revert. Not a huge amount, but we might want to consider changing these to work more cohesively.

Related: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=87729

We disconnected everything from the ISS array installation spare unit S1202965 and stored it in the ISS array cabinet in the vac prep area next to the OSB optics lab. See the first 8 pictures.

The  incomplete spare ISS array assy originally removed from LLO HAM2 (S1202966) was moved to a shelf under the work table right next to the clean loom in the optics lab (see the 9th picture). Note that one PD was pulled from that and was transplanted to our installation spare S1202965.

Metadata for both 2965 and 2966 were updated.

ISS second array parts inventory https://dcc.ligo.org/E2500191 is being updated.

Closes FAMIS#28429, last checked 87622

ITMX didn't have enough coherence again this time :(

ETMX

ETMY

ITMX

ITMY

FAMIS27827

No water was added, but the filters all looked good. There was no water in the Dixie Leak Detector. Updated the T2200289 sheet.

Closes FAMIS27404, last checked in alog87178

In general we can see blips at 10/21 and 09/10 from the BRS-Y damping issues and the power outage.

We can see the BRSY issues we had last week 10/21 alog87634, ETMY BRS temperature seems to still be slowly increasing just like last month?

BRS-X looks to be drifting down for ~all of October.

Last checked in alog87549, closes FAMIS27429.

There are a few noisy outbuilding fans, EY_470_1 and MX_370_1 are the worst offenders with ~ 0.3. MY_270_{1,2} see some sporadic noise increases everyday or less.

For the corner station fans, MR_FAN1_170_{1,2} have gotten a bit noisier 2 days ago, MR_FAN6_170_1 has also gotten a bit noisier the over past day. The winner of noisiest fan in the CS is MR_FAN5_170_1 at around ~0.4.

I swept the LVEA, nothing to report this week.

Procedure checklist for both stations completed.  No issues were identified at this time.

MX: Scroll pump hours: 236.9
       Turbo pump hours: 149
       Crash bearings: 100%

EX: Scroll pump hours: 7157.3
       Turbo pump hours: 1109
       Crash bearings: 100%

EX purge air compressor was ran for ~3 hours, dew point monitor reached <-40 deg F in ~15 minutes and at time of shut down was reporting -76 degF.

Compressor has 74 running hours total, distributed between the three scroll compressors. Drains are operational, dryers indicate normal operation. The only caveat here is that compared to the EY compressor, the main drain (after the compressor) discharged a lot more water. This indicates a higher humidity in the EX MER.

J. Kissel, M. Todd, S. Dwyer

Just recording this for posterity in case: Matt and I wanted to (continue) parallelizing our work on characterizing the ISS Array at full / nominal power (60W into the PSL) and characterizing RPM dynamics for future HSTS Estimator modeling, respectively. The estimator team discovered a week or two ago that PRM has a different dynamical response when the SUS is ALIGNED vs. MISALIGNED. So, I misaligned IM4 and PR2 to ensure the 60W didn't go anywhere but a fixed location, and aligned PRM. 

The worry is that IM4 doesn't have a "safe" designated fixed location to dump its reflected beam when misaligned -- there's no "parking dump" like there is for PRM. So -- this an aLOG to indicate the times of high power with IM4 misaligned and what little info we have about the physical position.

I say "what little information about the position we have" because IM4, which is a HAUX suspension -- while IM4 has recently had its OSEM sensor PD sat amp upgraded, we have not measured or installed an absolute calibration for the sensors with an ISI injection. We know from other suspensions, that OSEM PDs can have factors of 2x to 3x errors between the "generic calibration based on electronics and [likely ancient] open light current measurement" and the modern absolute calibration from the ISI GS13s.

There *is* a calibration of the IM4 alignment sliders -- installed in Apr 2024 (LHO:77211). 
However, that calibration was based on the OSEM sensor PDs. 
So we have to take the fidelity of this calibration with a huge grain of salt a la the above distrust in OSEM PD calibration.

So -- IM4 had the following alignment offsets requested of its sliders: 
              OFFSET       OUT16
             ["urad"]    [EB-DAC ct]
    P        +114.539     +1248.53
    Y        +111.103      +625.387

and its *misalignment* offsets -- which are not calibrated in the front-end, but I've calibrated them using the (P,Y) = (10.9005 , 5.6289) [EB-DAC ct / "urad"] calibration from LHO:77211 here: 
              OFFSET       OUT16
             ["urad"]   [EB-DAC ct]
    P         +50.915      +555.0
    Y         +98.598      +555.0

So, misaligned, that give a total requested displacement of  
              OFFSET       OUT16
             ["urad"]   [EB-DAC ct]
    P         165.454     1803.532
    Y         209.701     1180.388

IM4 was misaligned, with PRM aligned and PR2 misaligned, and 60W into the IMC from 2025-10-28 16:08 UTC to 2025-10-28 17:06 UTC. 

After 17:06 UTC, the IMC power remained at 60W, but I aligned IM4 and PR2 and misaligned PRM. (The normal "IFO DOWN" configuration).
(So yes, we didn't turn the IMC power down before we went from misaligned to aligned, either.)

Tue Oct 28 10:06:36 2025 INFO: Fill completed in 6min 32secs

J. Kissel, T. Shaffer, J. Warner

1) Set STS SELECT ramping matrix to use the ITMY biergarten GND T240;
    caput H1:ISI-GND_STS_MTRX_RAMPING_1_4 1.0
    caput H1:ISI-GND_STS_MTRX_RAMPING_2_5 1.0
    caput H1:ISI-GND_STS_MTRX_RAMPING_3_6 1.0

2) open ISI-HAM overview screen whose sensor correction you want to engage, open light blue SENSCOR Gnd->ISI block.

3) In the middle top, open Filter Selection screen. Hit "engage" on the NORM_FILT2 banks for all three X, Y, Z degrees of freedom (turning on the CML_BB_SC filter). This'll take 30 seconds, and then once done, it'll box will go green.
    caput H1:ISI-HAM3_SENSCOR_X_NEXT_CHAN 2.0
    caput H1:ISI-HAM3_SENSCOR_Y_NEXT_CHAN 2.0
    caput H1:ISI-HAM3_SENSCOR_Z_NEXT_CHAN 2.0

4) Back to the SENSOR Gnd->ISI screen, open the MATCH filter bank screen. Set the MATCH gain to 1.0
    H1:ISI-HAM3_SENSCOR_X_MATCH_GAIN 1.0
    H1:ISI-HAM3_SENSCOR_X_MATCH_GAIN 1.0
    H1:ISI-HAM3_SENSCOR_X_MATCH_GAIN 1.0
    
To disengage, do the opposite:
-1) Set the STS_SELECT matrix to all zeros.
-3) Hit the "disengage X, Y, Z" buttons.
-4) Set the MATCH gains to 0.0. 

1. OPTION 1: We set the M1_DAMP_Y filters to 20% gain, leaving all other M1_DAMP filters at 100% nominal gain. Measure all of the Yaw estimator transfer functions. Then, set M1_DAMP_L and M1_DAMP_P to 20% gain, leaving everthing else at 100% nominal gain. Measure all the Length/Pitch estimator transfer functions.
2. OPTION 2: We set all three of the M1_DAMP_{L,P,Y} to 20% gain and get all measurements for L, P , and Y transfer functions. This method is faster for measurement, but needs more fitting to deal with cross-couplings to Yaw.

Here are the thougths

• The risk of measuring all with 20% damping simultaneously is that we might have to fit  L/P-to-Y and Y-to-L/P transfer functions because the cross-couplings will peak at the lightly damped resonances. 
  Two cases to consider:
  1. In the worst case scenario, this is 4 extra transfer functions per stage to fit, added to the 5 we already fit. So for the HSTSs it will be 16 extra models, for a total of 36 fits.
  2. If the cross-coupling resonances are small with light-damping, or if the estimator to limits the drive to the cross-coupled plant enough that we can ignore the cross-coupling effects, then we can get away with only doing 20 fits.
• However, we can use the HLTSs as an example: if a 20% LPY damping measurement does not change the Y2Y transfer function for the PR3/SR3 compared to 20% Y and 100% L/P, then the model we are running on the HLTSs is identical to case (b) above, the best case scenario. 
  • Since the estimator on SR3/PR3 seems to work fine without L2Y/P2Y couplings, I see no loss whatsoever in doing 20% damping for all three.  [This is the thought that convinced me it will be fine to do OPTION 2] 
     
• Also, we run the plant with 20% LPY damping with the estimator already. It makes sense that we measure the exact plant that will be available when the estimator is running. Plus, It will be cleaner, only one set of measurements per estimator fit.
• If we wish to add a L to Y plant, the procedure is lengthier in the OPTION 2 (20% LPY) case, we have to add fits for L2Y for all stages measured. In OPTION 1, we can skip adding the M1 stage, as the damping is already folded into the measurements.
  • However, for suspensions with ISC drives, we risk double-counting the effects of the Suspoint motion into the ISC drives with OPTION 1. SInce the ISC drives were not included in the original measurement. 

FAMIS27395

Nothing unusual that I can tell.

This morning I tweaked the beam alignment into the RefCav from the Control Room using our picomotor mounts; the ISS was ON for this tweak, and the IMC was unlocked.  When I started the RefCav TPD was 0.514 V, and at completion the TPD is 0.535 V.  With the IMC relocked the RefCav TPD is reading 0.531 V.  Not much of an increase, and not as high as the last time we tweaked the alignment on the PSL table.  Everything seems OK for now, but things are moving towards an on-table alignment in the future (since I couldn't get the TPD back to where it was at last on-table alignment with beam alignment alone).  Will continue to monitor.

Bypass will expire:
Tue Oct 28 12:16:04 PM PDT 2025
For channel(s):
    H0:FMC-CS_FIRE_PUMP_1
    H0:FMC-CS_FIRE_PUMP_2
 

The well pump has been manually activated as of 7:46a for a duration of 4 hours to replenish the fire water tank.

C. Soike T. Guidry

Jeff, Ryan S, Oli

During last week's set of issues, something that we saw happen a few times during our lock reacquisition attempts were lots of EY saturations while going through LOWNOISE_COIL_DRIVERS/TRANSITION_FROM_ETMX. The saturations would stop once L2 to R0 damping was turned off (87713), so it seemed like the issue was with the ETMY L2 satamp, so we swapped it out with a different one (87722). We didn't see any of these repeating saturations after that, but also we were changing a lot of things at the time trying to figure out the problem, plus we hadn't been seeing these saturations during every single relock attempt.

The DAC channels that were showing saturations were from DAC1 channels 1 and 2. Checking the model, those channels line up with R0 F2 and F3, which are the channels that control Length on R0. We plotted R0's MASTER OUTs during times where we saw lots of the EY saturations, and at times where the saturations heard on verbals were normal, including a time before we swapped the ETMY L2 satamp on October 14th.

Here's a breakdown of the different examples we looked at:

We saw that for the times where the amount of saturations were what we consider 'normal', the LOWNOISE_COIL_DRIVERS/TRANSITION_FROM_ETMX states behave similarly in the R0 MASTER OUT channels, including after swapping the satamp. The OSEMs will see some movement, but it's not too far outside of where they usually sit. However, for the two times that we checked where we had the excessive EY saturations, we saw that right before they started, there was a high frequency glitch seen in the ETMY L2 Length witness channel. This glitch only moved L2 a small amount, about 0.5 um, but it was causing R0 to move a lot in Length, saturating or nearly saturating for a long time.

Plotting the impulse response of the SUS-ETMY_L2_R0DAMP_L filter bank, we see that these filters have an impulse response time of ~16 seconds, and breaking down the impulse response by each filter's contribution, we see that the FM8 (module 7) filter module, invPsmoo, has a wild impulse response. Because of this filter module, the impulse response of the entire R0_L2DAMP_L filter bank is extremely long, and the signal is very large. The frequency response plot for module 7 shows us that it approaches the 10^15 gain at higher frequencies. Additionally, these new satamps have about double the gain at high frequencies as compared to the old satamps, so that would also be exacerbating any issues at higher frequencies.

With all that said, it looks like the conclusion is that the EY saturation issues from last week were not caused by a faulty satamp, but instead by something else that caused L2 to glitch, and the long impulse response and high gain causing R0 to take forever to calm down.

A temporary solution would be to keep the L2 to R0 damping off during locking until after LOWNOISE_LENGTH_CONTROL has finished, to make sure that we are avoiding having it on during all the sudden movements that could upset R0.

J. Kissel, C. Gray, M. Nakano, G. Billingsley

We're getting started with cleaning our 1" and 2" optics for SPI. Corey uploaded *all* of our optics (50:50 BSs, 85:15 BSs, TFPs, HR mirrors, Lenses etc.) to ICS in prep, and I reviewed the work double checking that the ICS record information makes sense. For the HR mirrors, which were part of the 2025 large custom purchase order (C2500044) from FiveNine Optics (to be used by JAC, SQZ, the LLO TNT Lab, and SPI), he entered them into ICS with a key that used the DCC number that's physically etched into the barrel of the optic.

HOWEVER -- the DCC number etched on the barrel of the optic is E1900393 -- E1900393. See attached picture. 

That drawing number is for the coating spec of 0-25 deg AOI HR mirrors.

The physical coating spec we want, was provided, and bought was for 45 deg AOI, i.e. E1900392 -- E1900392 (one DCC number lower).

So these HR optics, coated with E1900392 spec, bought with C2500044, which have vendor run numbers 1895 and 1897, have the incorrect DCC number for the spec etched on the barrel.

If you head to the purchase order, C2500044, and look at the FNO_4787-1.pdf attachment, it clearly states (twice!)
    "[...] per drawing E1900392-V2. Serialization per E1900392-V2."

However, if you then *read* E1900392-v2, section 8 states equally clearly
    "Each optic should be serialized and marked with the following code/description:
        1" optics: E1900393-v2-01 S/N:01 HR1064+532
            with incremental S/N: 01, 02, 03, ...
        2" optics: E1900393-v2-02 S/N:01 HR1064+532
            with incremental S/N: 01, 02, 03, ..."

Thankfully we know the coating is the correct E1900392 coating --
(1) The PCAL team confirms via measurement at 45 deg AOI, that these have transmission at the level of ~5e-5 W/W, so these will serve excellently as HR mirrors at 45 deg AOI. See LHO:86699
(2) The vendor's data, posted to C2500186, (Even though the run numbers listed on the first page of the data for the First Batch are quoted as "V2-2895" and "V2-1897" we know the run numbers are V2-1895 and 1897 from what's written on the containers the optics came in; see attached picture) show figures with captions indicating the data is from AoIs of 38, 45, and 50 deg, a reasonable range of AoI's to test for a 45 deg AoI mirror; and conversely no measurement of anything at AoIs less than 25 deg, which would be what one would report for a coating that's spec'd with the *actual* E1900393 spec.
(3) The E1900392 spec specificies a 45 deg AoI.

So, now we just have to figure out how to keep track of this information when we're in the lab / in the chamber, 5 years later, and the optics are no where near their cases and a brand new person is using the optics. C'est le vie!