[Joan-Rene Merou, Alicia Calafat, Anamaria Effler, Sheila Dwyer, Robert Schofield, Jenne Driggers]

We have looked at the near-30 Hz and near-100 Hz combs (Detchar issue 340) in all of LHO Fscan channels (Full 148 channels list can be found in O4_H1_Fscan_ch_info.yml) to find witnesses and also channels where the amplitude and coherence change at the same dates as DARM.

The list of combs is the following one:


  

    

      
spacing (Hz)
      
offset (Hz)
    
  
  

    
29.9695138888
0
    
99.99845486125
70.02888889
    
99.99845679
0
    
99.99846
29.9694
    
99.9984722225
89.90847222
    
99.99865
0
    
99.99845
10.08992
    
29.96952
520.17208
    
29.9695211
589.9007589
    
29.96951374
760.22840625
  


As reported by Xuanye Fan in Detchar issue 296, "it can be determined that the high-order harmonics disappeared on April 8, 2024, and reappeared on July 7, 2024". Hence, we have compared coherence with DARM in all the channels and the difference between July 1st and July 7th 2024.

Following the findings by Xuanye, we have redone the comb time-evolution plots for all of these combs in order to check for dates where their amplitude changed. As can be seen in the plots below, there are two clear dates where changes in the behavior of the combs took place, April ~4th 2024 and July ~7th 2024. The attached plots to this post are similar to the ones generated by Fscan using FscanFineToothPlot plots, however, they have two differences: They use data from the non-normalized spectras instead of from the time average plots. Additionally, they compute the relative harmonic amplitude with respect to the median of the surrounding 1 Hz spectrogram. The attached plots confirm that there is a significant change in comb amplitude between April 4th and July 7th 2024. One clear example is shown here:



We list here the channels that do show most of these Combs. These same channels do show changes in coherence between July 1st and July 7th 2024, but do not show changes in the amplitude of the combs.

- H1_IMC-F_OUT_DQ
- H1_LSC-MCL_IN1_DQ
- H1_LSC-MICH_IN1_DQ
- H1_LSC-SRCL_IN1_DQ
- H1_PEM-CS_MAG_EBAY_LSCRACK_X_DQ
- H1_PEM-CS_MAG_EBAY_LSCRACK_Y_DQ
- H1_PEM-CS_MAG_EBAY_LSCRACK_Z_DQ
- H1_PEM-CS_MAG_LVEA_INPUTOPTICS_X_DQ
- H1_PEM-CS_MAG_LVEA_INPUTOPTICS_Y_DQ
- H1_PEM-CS_MAG_LVEA_INPUTOPTICS_Z_DQ

In most channels, the comb amplitude tends to get quite low after ~1500 Hz. The following sets of channels show differences between X, Y and Z:

- H1_PEM-CS_MAG_EBAY_SUSRACK_X_DQ (Higher amplitudes and towards higher frequencies)
- H1_PEM-CS_MAG_EBAY_SUSRACK_Y_DQ (Lower comb amplitudes)
- H1_PEM-CS_MAG_EBAY_SUSRACK_Y_DQ (Lower comb amplitudes)

Regarding CS_MAG_LVEA_OUTPUTOPTICS, these combs can be seen best in X, weaker in Y and almost non-existent in Z. (In CS_MAG_LVEA_INPUTOPTICS they look roughly the same height)

- H1_PEM-CS_MAG_LVEA_OUTPUTOPTICS_X_DQ (Strongest)
- H1_PEM-CS_MAG_LVEA_OUTPUTOPTICS_Y_DQ (Weaker lines)
- H1_PEM-CS_MAG_LVEA_OUTPUTOPTICS_Z_DQ (Almost no lines)

Same behavior at:
- H1_PEM-CS_MAG_LVEA_VERTEX_X_DQ (Strongest lines)
- H1_PEM-CS_MAG_LVEA_VERTEX_Y_DQ (Weaker lines)
- H1_PEM-CS_MAG_LVEA_VERTEX_Z_DQ (Almost no lines)

We can see that these combs mostly appear in the corner station. The combs do not appear in neither EX nor EY channels. However, comb 99.99865 Hz offset 0.000 appears in many EX, EY channels and does become more coherent after July 7th. However, it is very close to 100 Hz so it may be influenced by other round-number combs (?)

Fri Oct 10 10:07:47 2025 INFO: Fill completed in 7min 43secs

Gerardo confirmed a good fill curbside.

This is for FAMIS #27398.
Laser Status:
    NPRO output power is 1.857W
    AMP1 output power is 70.67W
    AMP2 output power is 140.3W
    NPRO watchdog is GREEN
    AMP1 watchdog is GREEN
    AMP2 watchdog is GREEN
    PDWD watchdog is GREEN

PMC:
    It has been locked 16 days, 21 hr 4 minutes
    Reflected power = 24.26W
    Transmitted power = 106.6W
    PowerSum = 130.8W

FSS:
    It has been locked for 0 days 1 hr and 35 min
    TPD[V] = 0.538V

ISS:
    The diffracted power is around 3.9%
    Last saturation event was 0 days 3 hours and 40 minutes ago

Possible Issues:
    PMC reflected power is high

TITLE: 10/10 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Observing at 152Mpc
OUTGOING OPERATOR: Ryan S
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 22mph Gusts, 13mph 3min avg
    Primary useism: 0.04 μm/s
    Secondary useism: 0.14 μm/s 
QUICK SUMMARY:

Looked like the spooky shaky night continued with another Phillipines EQ of M6.7 3hrs ago.  But continuing from Ibrahim's summary, after his alignment, H1 automatically made it back to NLN to observe for under 2hrs until the next lockloss (no EQ tag tho); then a brief SQZ drop (see below).  Finally the EQ 3+hr ago which took down H1/L1.  There were no Wake-Up calls last night.

Environmentally:  watch for EQs!  AND winds have been picking up over the last 90min with winds just under 30mph currently.

Overnight ISSUES:

• 1104-1108 SQZ Unlocked due to "LO Railing":

2025-10-10_09:47:27.819286Z SQZ_MANAGER executing state: FREQ_DEP_SQZ (100)
2025-10-10_11:04:43.645262Z SQZ_MANAGER [FREQ_DEP_SQZ.run] Unstalling SQZ_PMC
2025-10-10_11:04:43.839754Z SQZ_MANAGER [FREQ_DEP_SQZ.run] USERMSG 0: LO railing!
2025-10-10_11:04:43.839754Z SQZ_MANAGER [FREQ_DEP_SQZ.run] LO unlocked

TITLE: 10/10 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Earthquake
INCOMING OPERATOR: Ryan S
SHIFT SUMMARY:

IFO is LOCKING at CHECK_IR

Started as a quiet shift in which there was a coordinated calibration sweep with LLO. It ran successfully - alog 87401.

Then we lost lock due to a 7.4 EQ from the Philippines (lockloss alog 87402) After 2.5 hours of sitting in IDLE watching peakmon, I began to relock and though we made it past FIND_IR (losing lock a few times due to ground motion), we had very bad flashes at DRMI.

I just finished running an initial alignment and now IFO is LOCKING.

LOG:

None

Earthquake caused lockloss from an M7.4 in the Philippines. High gain was active but was (understandably) not enough. Staying in DOWN until the ground calms down (still anticipating R waves in 33 mins according to SEI_CONFIG.

Per today's comissioning recommendation, I ran a calibration sweep at the same time as LLO (17:15 PT). It was successful.

BB Start: 1444090610

BB End: 1444090920

Simulines Start: 1444091000

Simulines End: 1444092397

2025-10-10 00:45:43,280 | INFO | Finished gathering data. Data ends at 1444092360.0
2025-10-10 00:45:43,486 | INFO | It is SAFE TO RETURN TO OBSERVING now, whilst data is processed.
2025-10-10 00:45:43,486 | INFO | Commencing data processing.
2025-10-10 00:45:43,486 | INFO | Ending lockloss monitor. This is either due to having completed the measurement, and this functionality being terminated; or because the whole process was aborted.
2025-10-10 00:46:19,595 | INFO | File written out to: /ligo/groups/cal/H1/measurements/DARMOLG_SS/DARMOLG_SS_20251010T002302Z.hdf5
2025-10-10 00:46:19,602 | INFO | File written out to: /ligo/groups/cal/H1/measurements/PCALY2DARM_SS/PCALY2DARM_SS_20251010T002302Z.hdf5
2025-10-10 00:46:19,607 | INFO | File written out to: /ligo/groups/cal/H1/measurements/SUSETMX_L1_SS/SUSETMX_L1_SS_20251010T002302Z.hdf5
2025-10-10 00:46:19,612 | INFO | File written out to: /ligo/groups/cal/H1/measurements/SUSETMX_L2_SS/SUSETMX_L2_SS_20251010T002302Z.hdf5
2025-10-10 00:46:19,616 | INFO | File written out to: /ligo/groups/cal/H1/measurements/SUSETMX_L3_SS/SUSETMX_L3_SS_20251010T002302Z.hdf5
PDT: 2025-10-09 17:46:19.750557 PDT
UTC: 2025-10-10 00:46:19.750557 UTC
GPS: 1444092397.750557
 

Report: /ligo/groups/cal/H1/reports/20251010T002302Z/H1_calibration_report_20251010T002302Z.pdf

Keita, Jennie W, Rahul

Executive Summary: The coupling for PDs & and 8 is between 200 and 300 RIN per m. This is far too high. We might need to re-align to a different spot tomorrow and retake coupling measurements.

We went back into the lab yesterday afternoon (8th October) to find a spot where the PDs were all aligned well in DC voltage.

We found a spot (by changing PZT mirror translation horizontally across the input beam and by tilting the input mirror. The first we use to optimise the horizontal coupling to the PDs, the second we use to optimise the vertical coupling.

The spot we arrived at for the input pointing is one which doesn't seem to have particularly bad coupling in vertical or yaw for any of the PDs. This is made more problematic as PDs 2 and 6 are mis-aligned relative to the others in pitch and yaw (see graphs of PD DC alignment in LHO alog #87324) we think so there coupling is not minimised close to where the coupling of the other 5 diodes is minimised.

Then we moved the QPD to be centred on this new spot.

We took coupling measurements but will do the calibration tomorrow.

The alignment references for this position are pitch allen key = 14.7mm

Micrometer reading on translation stage = 0.4162 inches.

Today I calibrated the data using the calibration from Tuesday. Since we moved the QPD after that point we need to scale the calibration value.

Attached is Keita's working for this here and here.

The processed data is shown here and the DC values for each PD are here.

One can see that 7 and 8 have a very high coupling, but their DC values are ok. PDs 2 and 4 have low coupling but their DC values are not too low as was the case with one of the PDs on Tuesday (LHO alog #87373), so I trust these values.

TITLE: 10/09 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Observing at 155Mpc
INCOMING OPERATOR: Ibrahim
SHIFT SUMMARY:

Commissioning in the morning (including a lockloss), then H1 relocked fine and has been locked the last few hours.

HANDOFF Note:  Assuming L1 runs a calibration tonight, H1 will go out of Observing when L1 does to run another calibration since there was an update to the H1 calibration this afternoon (after this morning's calibration).  Will let Ibrahim know about this & that I confirmed this with Joe Hanson (L1 EVE operator).
LOG:

• 1445-1800 Y-arm BTE inspection EY toward MY (randy)
• 1511-1526 Optics Lab Technical Clean (nellie)
• 1457-1536 Y-arm run (matt)
• 1533 out of observing for COMMISSIONING
  • 1533 No SQZ meas (Camilla)
  • 1534-1540 PEM set-up....but will be in/out during commissioning(robert)
  • 1547 swept sine (elenna)
  • 1712-1744 Calibration measurements
  • 1745 Robert crawling under BSC2
  • 1840 LOCKLOSS (Robert was crawling around BSC2)
    • Paused a few minutes to wait out BSC2 ISI WD trip from Robert & then returned to locking.
    • To save time, Proactively took ISC Lock to Check Mich Fringes since H1 was locked for so long & assumed it would be misaligned.
• 1553-1615 EX trip to grab a light in fan room (chris)
• 1609-1631 MY parts search (travis)
• 1709 Returning laptops to Cleaning Room (tony)
• 2005 Back to OBSERVING
• 2029-2144 MY Emergency Pump work (travis)
• 2107-2256 Receiving CHETA parts in JAC Lab (camilla, matt)
• 2144-2148 Dropped OUT of Observing for Calibration change (elenna, jenne)

TITLE: 10/09 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Observing at 151Mpc
OUTGOING OPERATOR: Corey
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 13mph Gusts, 6mph 3min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.17 μm/s 
QUICK SUMMARY:

IFO is in NLN and OBSERVING

There is a plan for coordinated calibration with LLO at 5:10 PT so will contact LLO and if ready, do a full CAL sweep.

Nothing else of note.

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!

I updated Jim's "rasta plot" with a line for when Jim thinks we should turn on the high ASC to help us ride through earthquakes. This is a guess and will need more tested times, so we will very likely make changes to this in the near future. Operators, please transition to the high ASC before the earthquake arrives. You can transition back when the earthquake has sufficiently calmed down, perhaps even waiting until the SEI_ENV node goes out of Earthquake mode. 

Interestingly, the M6.0 from Russia this morning would have been in the high ASC realm, but we looked to have scraped by and survived. 

I'm ready to test the Guardian version of this high ASC switch whenever we get the chance. We had a lock loss just before trying it today, so perhaps Monday or opportunistically over the weekend. In the mean time operators will have to do the switching manually.

Over the last several weeks, I have collected some HAM ISI to DARM coupling measurements. These are the only HAM ISI that don't have st0 L4C feedforward, and should have overall not as good performance as the other HAMs. Attached pdfs show the coupling to darm for the closest analogs to their associate cavity length, pitch, yaw and vertical dofs. It seems like HAM2 generally has the worst coupling, then HAM6, then HAM3. HAM2 is already planned to receive st0 l4cs in the next vent, as well as lower noise vertical CPS. HAM3 is only planned to receive the lower noise CPS, for now. For HAM6, I have been trying ground to HEPI l4c feedforward, but so far haven't found a stable filter and don't yet understand why that feedforward is not work at HAM6 yet.

We noticed that comparing the last two calibration reports that there has been a significant change in the systematic error, 87295. It's not immediately obvious what the cause of this is. Two current problems we are aware of: there is test mass charge, and kappa TST is up by more than 3%, and we lost another 1% optical gain since the power outage.

One possible source is the SRC detuning changing (not sure how this could happen, but it might change).

Today, I tried to correct some of these issues.

Correcting actuation:

This is pretty straightforward, I measured the DARM OLG and adjusted the L3 DRIVEALIGN gain to bring the UGF back t about 70 Hz, and Kappa TST back to 1. This required about a 3.5% reduction in the drivealign gain, from 88.285 to 85.21. I confirmed that this did the right thing by comparing the DARM OLG to an old reference and watching kappa TST. I updated the guardian with this new gain, SDFed, and changed the standard calibration pydarm ini file to have this new gain. I also remembered to update this gain in the CAL CS model.

Correcting sensing:

Next, Camilla took a sqz data set using FIS at different SRCL offsets, 87387. We did the usual 3 SRCL offset steps, but then we were confused by the results, so we added in a fourth at -450 ct. Part of this measurement requires us to guess how much SRCL detuning each measurement has, so we spent a bunch of time iterating to make our gwinc fit match the data in this plot. I'm still not sure we did it right, but it could also be something else wrong with the model. The linear fit suggests we need about a -435 ct offset. We changed the offset following this result.

Checking the result:

After these changes, Corey ran the usual calibration sweep. The broadband comparison showed some improvement in the calibration. However, the calibration report shows a significant spring in the sensing function. To compare how this looks relative to previous measurements, I plotted the last three sensing function measurements.

The calibration was still with 1% uncertainty on 9/27. On 10/4, the calibration uncertainty increased. Today, we changed the SRCL offset following our SQZ measurement. This plot compares those three times, and includes the digital SRCL offset engaged at the time. I also took the ratio of each measurement with the measurement from 9.27 to highlight the differences. It seems like the difference between the 9/27 and 10/4 calibration cannot be attributed much to a change in the sensing. And clearly, this new SRCL offset makes the sensing function have an even larger spring than before.

Therefore, I concluded that this was a bad change to the offset, and I reverted. Unfortunately, it's too late today to get a new measurement. Since we have changed parameters, we would need a calibration measurement before we could generate a new model to push. Hopefully we can get a good measurement this Saturday. Whatever has changed about the calibration, I don't think it's from the SRCL offset. Also, correcting the L3 actuation strength was useful, but it doesn't account for the discrepancy we are seeing.

Just had a lockloss while Robert was out on the floor during commissioning time (ends a 20.5+hr lock).

NOTE:  For this particular Thurs Calibration, Commissioning work was done first for almost 2-hrs and then this Calibration was run.

Measurement NOTES:

• Following instructions (link)
• H1 at NLN for for ~19+hrs
• Calibration_Monitor medm screenshot is attached
• This Calibration was run after about 2.25hrs of commissioning 
•  Broadband measurement started at  17:12:31 utc ended 17:18:04utc
• Measurement at:  /ligo/groups/cal/H1/measurements/PCALY2DARM_BB/PCALY2DARM_BB_20251009T171253Z.xml
•  Simullines measurement
  • gps START time: 1444065645.179760  (1720utc)
  • gps STOP time:  1444067041.828354 (1743utc)
  •  File written out to: /ligo/groups/cal/H1/measurements/DARMOLG_SS/DARMOLG_SS_20251009T172027Z.hdf5
  • File written out to: /ligo/groups/cal/H1/measurements/PCALY2DARM_SS/PCALY2DARM_SS_20251009T172027Z.hdf5
  • File written out to: /ligo/groups/cal/H1/measurements/SUSETMX_L1_SS/SUSETMX_L1_SS_20251009T172027Z.hdf5
  • File written out to: /ligo/groups/cal/H1/measurements/SUSETMX_L2_SS/SUSETMX_L2_SS_20251009T172027Z.hdf5
  • File written out to: /ligo/groups/cal/H1/measurements/SUSETMX_L3_SS/SUSETMX_L3_SS_20251009T172027Z.hdf5
•   utc ISC_LOCK taken back to NLN & started commissioning
• PDF of PYDARM Report is attached also.

We went into no SQZ from 15:34UTC to 15:42UTC. I checked NLG as in 76542.