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

TITLE: 10/28 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Lock Acquisition
OUTGOING OPERATOR: Ibrahim
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 10mph Gusts, 8mph 3min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.21 μm/s 
QUICK SUMMARY: Locked for almost 2 hours, maintenance day. Calm environment. Magnetic injections and sus charge running now.

Workstations were updated and rebooted.  This was an os packages update.  Conda packages were not updated.

TITLE: 10/27 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Observing at 152Mpc
INCOMING OPERATOR: Ibrahim
SHIFT SUMMARY:

H1's been locked 9.25hrs.  Environmentally all is quiet.
LOG:   0327 GRB Short

Jeff, Oli

Along with trying to verify the current location of the BBSS's primary prism on LLO and LHO's dummy masses (87767), we also wanted to check to see if we were near a point of instability for the prism relative to the center of mass of the dummy test mass. I plotted the model with the original value for d4, 2.67mm, alongside models with OG d4 +/- 1mm, 2mm, and 3mm. They all look like stable places to put the prism, so it looks like we don't have to worry. The plots can be found at /ligo/svncommon/SusSVN/sus/trunk/BBSS/Common/Results/comparetripleparams/2025-10-28_BBSS_d4nom_plusminus3mm/triplemodelcomp_2025-10-28_BBSS_d4nom_plusminus3mm_M1toM1.pdf svn r12759

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.

TITLE: 10/27 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Observing at 149Mpc
INCOMING OPERATOR: Corey
SHIFT SUMMARY: Two lock acquisitions today, both of which involved pauses for some commissioning measurements, but otherwise they were automatic. Rode through an earthquake this afternoon using the high-gain ASC configuration, which very likely saved time with relocking afterwords. H1 has now been locked for 4 hours.

• 14:44 - Starting initial alignment
• 15:22 - Starting lock acquisition
• 16:57 - Reached NLN, starting commissioning
• 17:14 - Lockloss
• 19:43 - Reached NLN
  • Mitigated 1 Hz ASC ringup, accepted SDFs, ran switch_nom_sqz_states script, touched up SQZ rejected pump fiber power - alog87771
• 19:54 - Observing
• 20:32 - Dropped observing for high-gain ASC to ride out EQ
• 21:17 - Observing

LOG:

TITLE: 10/27 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Observing at 148Mpc
OUTGOING OPERATOR: Ryan S
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 8mph Gusts, 3mph 3min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.26 μm/s 
QUICK SUMMARY:

Got the rundown from RyanS with H1's status (which has been good even with the EQs), it has been locked 3.5hrs.  Microseism has leveled off (between the 50th & 90th percentile lines, after it's fast downturn yesterday), and winds lare calm.

Summary:

We aligned everything such that none of 8 PDs was excellent but all were OK (we were also able to set up such that 4 pds were excellent but a few were terrible but decided not to take that), we were preparing for putting the array in storage until the installation, only to find that something is wrong with the design of the asymmetric QPD clamp D1300963-V2. It's unusable as is.

QPD clamp doesn't constrain the position of the QPD laterally, and there's a gross mismatch between the position of properly aligned QPD and that of the center hole of the QPD clamp. Because of that, when QPD is properly positioned, one of the QPD pins will touch the QPD clamp and be grounded unless the QPD connector is fixed such a way to pull the QPD pins sideways. Fortunately but sadly, the old non-tilt QPD clamp D1300963-V1 works better, so we'll use that.

Another minor issue, is that there seems to be a confusion as to the direction of the QPD tilt in terms of the word "pitch" and "yaw". The way the QPD is tilted in D1101059-v5 (this is how things are set up in the lab as of now) doesn't seem to follow the design intent of ECR E1400231 though it follows the word of it. After confirming that this is the case with systems, we'll change the QPD tilt direction (or not). This means that we're not ready to put everything in storage quite yet.  

None of these affect the PD array alignment we've done, this is just a problem of the QPD.

Pin grounding issue due to the QPD clamp design.

I loosened the screws for the QPD connector clamps (circled in blue in the first attachment) and the output of the QPD preamp got crazy with super large 60Hz noise and large DC SUM even though there was no laser light.

I disconnected the QPD connector, removed the connector clamps too, and found that one pin of the QPD was short circuited to the ground via the QPD clamp (not to be confused with the QPC connector clamps, see 2nd attachment).

Turns out, the offending pin was isolated during our adjustments all the time because the QPD connector clamps were putting enough lateral pressure as well as down such that the pins were slightly bent from the offending side. I was able to reattach the connector, push it laterally while tightening the clamp screws, and confirm that the QPD functioned fine. But this is not really where we wanted to be.

I rotated the QPD clamp 180 degrees (which turns out to make more sense judging from the drawings in the first attachment), which moved the QPD. Since the beam radius is about 0.2mm, if the QPD moves by 0.2mm it's not useful as a reference of the in-lab beam position. I turned the laser on, repositioned the QPD back to where it should be, but the pin on the opposite side started touching. (Sorry no picture.)

I put the old non-tilt version clamp and it was much, much better (attachment 3). It's annoying because the screw holes don't have an angled recess. The screw head is tilted relative to the mating surface on the clamp, contacting at a single point, and tightening/loosening the screw tend to move the QPD. But it's possible to carefully tighten one screw a bit, then the other one a bit, repeat that dozen times or so until nothing moves even when pushed firmly by finger. After that, you can still move the QPD by tiny amounts by tapping the QPD assy by bigger Allen key. Then tighten again.

What's going on here?

In the 4th attachment, you can see that the "center" hole of the QPD clamp is offset by 0.55" (1.4mm) in the direction orthogonal to A-A, and about 0.07" (even though this number is not specified anywhere in the drawing) or 1.8mm in A-A direction. So the total lateral offset is sqrt(1.4^2+1.8^2)~2.3mm. OTOH, the QPD assy is only 0.5" thick, so the lateral shift arising from the 1.41deg tilt at the back of the QPD assy is just 1.41/180*pi*0.5=0.0123" or 0.3mm.

Given that the beam position relative to the array structure is determined by the array itself and not by how the QPD is mounted, 2.3mm lateral shift is impossibly large, something must be wrong in the design. The 5th attachment is a visual aid for you.

Anyway, we'll use the old clamp, it's not worth designing and manufacturing new ones at this point.

QPD tilt direction.

If you go back to the first attachment, the QPD is tilted in a direction indicated by a red "tilt" arrow in the lab as we just followed the drawing.

The ECR E1400231 says "We have to tilt the QPD 1 deg in tip (pitch) and 1 deg in tilt (yaw)" and it sounds as if it colloborates with the drawing.

However, I suspect that "pitch" and "yaw" in the above sentence might have been misused. In the right figure of the 6th attachment (screeshot of ECR unedited), it seems that the QPD reflection hits the elevator (the red 45 degree thing in the figure) at around 6 O'clock position around the eliptic exit hole, which means that the QPD is tilted in its optical PIT. If it's really tilted 1 degree in optical PIT and 1 degree in optical YAW, the reflection will hit something like 7:30 position instead of 6:00.

That makes sense as the design intent of the ECR is to make sure that the QPD reflection will not go back into the exit hole. The 7th attachment is a side view I made, red lines represent the IR beams, yellow lines the internal hole(s) in the elevator, and green lines the aperture of the two eliptical exit holes. Nothing is to scale, but hopefully you agree that, in order to steer the QPD reflection outside of the exit hole aperture, PIT UP requires the largest tilt and PIT DOWN requires the least tilt. We have a fixed tilt of QPD, so it's best to PIT DOWN, that's what I read from the ECR. If you don't know which angle is bigger or smaller, see attachment 8.

Anyway, I'll ask Callum if my interpretation is correct, and will act accordingly.

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!