Jeff, Oli

We were a bit unsure yesterday about the OPO but after some more measurements today I've confirmed that it is looking good. It still doesn't look like it did in 2022, but it works for us.

After some cable redressing last week the OPO was looking a lot better (88921), and then some further redressing was done (88957), which didn't seem to help, but at least didn't make Yaw worse. Those measurements were all taken with the ISI Locked. Yesterday I took what were supposed to be closeout measurements with the ISI now unlocked and DAMPED, but those measurements looked different from last week's, and not in a good way. There were two sets of measurements taken yesterday, one with the OPO damping all off (2026-02-03 1815UTC), and one where the DOF being measured was turned off, but the other DOFs were left damping (aka semi-off) (2026-02-03 1730UTC). Both measurement sets looked about the same besides a small increase in the highest frequency peak, but nowhere near the height it had been at last week(regular, zoomed).

In both sets of measurements, the lowest- and highest-frequency peaks (cross-coupling from T and V, respectively) were much smaller than they had been last week (last week we had thought the lowest peak had been split off from the main Yaw peak, but it was actually a shifted T cross-coupling). This was unexpected. The only (known) difference between last week's measurements and these two sets is the difference in the ISI, Locked vs Unlocked and DAMPED.

We decided to look at previous OPO measurements(regular, zoomed, txt explaining timeline from Jeff) taken with the ISI Locked, DAMPED, and ISOLATED, and found that the OPO resonances go down in Q when going from Locked to DAMPED. It also looks like once the ISI is ISOLATED, the resonances will rise back up(better zoom in). This could make sense as to why we're only seeing changes in the T and V resonances since the ISI moving side to side or up and down while in DAMPING would couple more directly into the OPO than when the ISI rotates.

The only way to confirm this idea was to take more measurements while the ISI was either Locked again or ISOLATED. Since yesterday afternoon the ISI had to be Locked again, I was able to take some measurements this morning(2026-02-04 1545UTC(all damping off), 2026-02-04 1630UTC(damping semi-off)), and they confirmed that the OPO looks like it did last week(regular, zoomed). So we're pretty sure once the ISI is back to ISOLATED it'll look like it did when the ISI was Locked earlier today and last week.

Yesterday's Measurements
- ISI Unlocked and DAMPED
2026-02-03 1730UTC
- OPO M1 DAMP all ON EXCEPT for DOF we are measuring (Semi-Off)
Data
/ligo/svncommon/SusSVN/sus/trunk/OPOS/H1/OPO/SAGM1/Data/2026-02-03_1730_H1SUSOPO_M1_WhiteNoise_{L,T,V,R,P,Y}_0p02to50Hz.xml
r12868
Results
/ligo/svncommon/SusSVN/sus/trunk/OPOS/H1/OPO/SAGM1/Results/2026-02-03_1730_H1SUSOPO_M1_ALL_TFs.pdf
r12869

2026-02-03 1815UTC
- OPO M1 DAMP all OFF
Data
/ligo/svncommon/SusSVN/sus/trunk/OPOS/H1/OPO/SAGM1/Data/2026-02-03_1815_H1SUSOPO_M1_WhiteNoise_{L,T,V,R,P,Y}_0p02to50Hz.xml
r12868
Results
/ligo/svncommon/SusSVN/sus/trunk/OPOS/H1/OPO/SAGM1/Results/2026-02-03_1815_H1SUSOPO_M1_ALL_TFs.pdf
r12869

Today's Measurements
- ISI Locked
2026-02-04 1545UTC
- OPO M1 DAMP all OFF
Data
/ligo/svncommon/SusSVN/sus/trunk/OPOS/H1/OPO/SAGM1/Data/2026-02-04_1545_H1SUSOPO_M1_WhiteNoise_{L,T,V,R,P,Y}_0p02to50Hz.xml
r12874
Results
/ligo/svncommon/SusSVN/sus/trunk/OPOS/H1/OPO/SAGM1/Results/2026-02-04_1545_H1SUSOPO_M1_ALL_TFs.pdf
r12876

2026-02-04 1630UTC
- OPO M1 DAMP all ON EXCEPT for DOF we are measuring (Semi-Off)
Data
/ligo/svncommon/SusSVN/sus/trunk/OPOS/H1/OPO/SAGM1/Data/2026-02-04_1630_H1SUSOPO_M1_WhiteNoise_{L,T,V,R,P,Y}_0p02to50Hz.xml
r12878
Results
/ligo/svncommon/SusSVN/sus/trunk/OPOS/H1/OPO/SAGM1/Results/2026-02-04_1630_H1SUSOPO_M1_ALL_TFs.pdf
r12877

Comparison plots
2022 vs last week vs yesterday
/ligo/svncommon/SusSVN/sus/trunk/OPOS/Common/Data/alloposs_2026-02-03_H1SUSOPO_StillPossibleIssue_ALL_TFs.pdf
/ligo/svncommon/SusSVN/sus/trunk/OPOS/Common/Data/alloposs_2026-02-03_H1SUSOPO_StillPossibleIssue_ALL_ZOOMED_TFs.pdf
r12872

ISI Locked v Damped v Isolated
/ligo/svncommon/SusSVN/sus/trunk/OPOS/Common/Data/alloposs_2026-02-03_H1SUSOPO_MaybeMysterySolved_ALL_TFs.pdf
/ligo/svncommon/SusSVN/sus/trunk/OPOS/Common/Data/alloposs_2026-02-03_H1SUSOPO_MaybeMysterySolved_ALL_ZOOMED_TFs.pdf
r12871

Everything looking good today
/ligo/svncommon/SusSVN/sus/trunk/OPOS/Common/Data/alloposs_2026-02-03_H1SUSOPO_LookingGood_ALL_TFs.pdf
/ligo/svncommon/SusSVN/sus/trunk/OPOS/Common/Data/alloposs_2026-02-03_H1SUSOPO_LookingGood_ALL_ZOOMED_TFs.pdf
r12887

The front fan bearing in Fan 1 inside AHU-1 was replaced this morning. Fan is currently off since Fan 2 is running in the lead position. 

All the whitening gain and filter are off.

at JAC-PZT_DRV_IN**/JAC-PZT_DRIVER_VOLTS: 532nm/179V = 2.97nm/V
at JAC-PZT_DRV_OUT_DQ = 532nm/8601cnts = 0.062nm/cnts

J. Kissel
- D2500175 :: S3228003
   . D2100573
   . E2300345
- D2400281

I'm finally back in the optics lab, taking the next steps towards assembling the SPI. 

Specific to this entry -- I'm assembling the Class A clean components of the fiber-coupled seed laser light. In other words, I'm integrating 
    (1) S3228003*** -- One of the 4.5" (inch) 1064nm V-FT Optical Fiber Feedthrough (Feedthru) Conflat Flange (DIAMOND) (D2500175) -- which includes the "off the shelf" (OTS) feedthru and integrated 3 [m] patch cord (the industry jargon for fiber optic cable), and its MIT-designed strain relief assembly D2100573 -- all delivered to LHO after class-A cleaning and assembly at Caltech per E2400159.
    (2) the ANU-designed Fiber Storage Spool assembly, D2400281, of which we have two.

Sina characterized the power transmission of all three of the feedthrus at Stanford before the clean-n-bake process, and identified that S3228003 had 100% transmission, so I've chosen that to be assigned to the MEAS path, where we need the most input power (as it's distributed through the most number of beam splitters). I plan to further integrate the patch cord into the SuK fiber collimator S0272503 for no better reason that to "pair the S[...]03 feedthru with the S[...]03 fiber collimator." 

***The serial numbers for the OTS feedthrus (D2500175) are of the alpha-numeric form 2153228V00n, where n = 1, 2, 3. That full version of the serial number is indicated in their ICS record, but in order to conform to the mold of the DCC S-numbers, I truncated the format to be numeric, S322800n, i.e. removing the identical leading 215 and misleading/unnecessary V character in the middle. 

Pictured here is 
    - The pre-assembly components of the fiber storage spool (First) 
    - The completed assembly of the spool with S3228003's patch cord wound up within it (Second and Third)

The feedthru's patch cord still has a Thor Lab Narrow-Key Mating sleeve (but NOT polarization maintaining) ADAFCB3 that is not intended to be a part of the final assembly, just there for fiber storage during shipment. I'd yet to detach it in these pictures.

Commentary:
     - Coiling the fiber within the spool was nerve racking. It feels like you're trying to coerce dry spaghetti into a curve without it snapping. If you let it go, it "sproings" into a wild relatively straight mess. In the end, holding it all mid-air with both hands, I used the weight of the mating sleeve to slowly pull the coil tighter as I rotated the coil nudging the rest of the coil into the newer smaller circle, until I met the radius of the storage spool. I had the goal of coiling it with one end "on top" and the other "on the bottom" of the stack, but I gave up on that. Once to the desired radius and no smaller, I used the securing cross, resting loosely across only 1/4 of the spool to hold the bulk of the coil of fiber in place while I tucked the rest of the length into the guiding channel. This is doable with a chair and patience in the open space of the optics lab, but I'm not looking forward to ding this in chamber.
     - Thinking through the install, my current plan is as follows :: WHAM3 D5 is currently a 12 inch blank with no 4.5 inch flange adapters. So it *needs* to be replaced by a 12 inch to 3x 4.5 inch flange adapter. So let's create the full 12 inch flange assembly with the 2x, MEAS and REF, fiber feedthroughs and 1x 4.5 blank -- and spool the fibers -- in the optics lab. Then we bring and install the whole 12 inch assembly on to HAM3 as a whole. 

Took HAM7 close out measurements this morning. They look ok, like the measurements taken in 2024. I believe there are known OPO plant interactions with the ISI plant that make it difficult to get clean tfs like other chambers. We should be ok to close.

Wed Feb 04 10:07:32 2026 INFO: Fill completed in 7min 29secs

Gerardo confirmed a good fill curbside.

TITLE: 02/04 Day Shift: 1530-0030 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    SEI_ENV state: MAINTENANCE
    Wind: 6mph Gusts, 5mph 3min avg
    Primary useism: 0.03 μm/s
    Secondary useism: 0.43 μm/s 
QUICK SUMMARY:

Work continues in chamber

Reminder that the LVEA is LASER SAFE EXCEPT around HAM1/2 and at height.

Functionality test for the corner station turbo pumps, see notes below:

Output mode cleaner tube turbo station;
Scroll pump hours: 7287.3
Turbo pump hours: 7309
Crash bearing life is at 100%

X beam manifold turbo station;
Scroll pump hours: 3389.9
Turbo pump hours: 3394
Crash bearing life is at 100%

Y beam manifold turbo station;
Scroll pump hours: 4160.3
Turbo pump hours: 2829
Crash bearing life is at 100%

FAMIS tasks 31332, 31340 and 31348.

Jennie W, Masayuki N, Keita K, Betsy W

Today we worked on improving the mode matching of the HAM1 output beam to the IMC. We also noticed the beam was going through the EOM and clipping somewhere inside so had to move the EOM up and sideways by a small ampunt to fix this. We will need to redo the RF electrical testing and the modulation depth testing for the EOM.

We improved the mode-matching of the HAM 1 output beam to the IMC by moving the lens L2 further away from JM2. We did 3 moves of 1 inch each and regained the alignment into IMC each time by using JM3 and JM2 to regain the pointing. At the end of this process we had a mode-mis-match of 1.1 % into the IMC.

After this a clipping of the beam was spotted by Keita somewhere between JM2 and JM3. We traced this down to the beam clipping somewhere inside the EOM crystal. This was fixed by shimming up the EOM at three points, after this we checked the mode-mis-match and it was 0.7%.

Then we realised there was still some clipping in pitch and so moved the EOM towards the -Y side of the table slightly. After these moves the mode mismatch was still 0.63 %.

Then after some alignent checks Keita and Masayuki have realised we need to rotate the EOM relative to the beam. This will require a sawn-off allen key as one of the 3 bolts required to yaw the EOM on its base is too near the sma connector elbows.

Camilla informed me that the non-magnetic tools might have one clean sawn-off 1/4 " allen key so left these in a tote bagged up on the + Y side outside the clean room.

Randy, Sheila, Betsy, Kar Meng, Camilla

After Sheila and Kar Meng found an issue with FC QPD A segment 3 88991, and after discussion with Ali James, Sheila went into chamber to test it.

Started with flashlight to confirm A vs B. Then after unplugging QPDs at SQZ rack, Sheila removed the diode detector holder D2000384 from the enclosure D2000246 (marked part #4). Once the cables were plugged back in at the rack, the signals on segments 1, 2, and 4 fell to zero but the segment 3 signal stayed railed at +30. This shows the issue is most likely inside the sealed enclosure, which is not a trivial fix. We attempted to swap the in-vac cables on the diodes to be sure the issue isn't in the in-vac cables or feed-through the cable was hard to removed so we stopped. Finished with a flashlight test again.

After consulting Safety on the technique, we employed a plank on the stationary fork lift to add an extra seating-perch in order to reach and troubleshoot the issue.  Photo attached of Sheila "surfing". 

TITLE: 02/04 Day Shift: 1530-0030 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY:  Lots of work towards finishing up in HAM1 and HAM7, including some surfing! LVEA is still LASER SAFE except behind the curtasins by HAM1/2 and at height.
LOG:                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              

Fil, Rahul

Out of chamber investigation

This morning Fil and I unplugged Tip Tilt PM1 cable going to its Satamp and connected it to Tip Tilt JM3 and found no change in its Bosem counts (was still low for UL and UR, like before). We connected JM3 to PM1's electronics chain and it was looking good. We also checked the long grey cable and found it to be healthy. Thus we came to this conclusion that in-air electronics chain is healthy for PM1.

In-chamber investigation

During lunch time when the chamber was empty, I took the OLC of all four BOSEMs for PM1 and found their values to be lower by 20% (last taken in April 2025).

This tells me that either the in-vacuum cable is not working properly or all four Bosems are malfunctioning. I need more in-chamber time to further investigate this issue.

Closes FAMIS27833, last checked in alog88799

Values added to spreadsheet. 

WP13007 TW1 offload

Oli, Dave:

I started the offload process this morning. The first step is to freeze the past 6 months of raw minute trend data on TW1 and start writing current data to a new directory. While the copy is proceding, which takes 24 hours, NDS1 needs to serve the raw minutes from their temporary location. To this end, at 11:20 I reconfigured NDS1 daqdrc and restarted the rts-daqd.service. Oli recovered the control room FOM ndscopes after this restart.

As noted on Friday, RLF QPD A segment 3 railed Nov 29th, and has been railed since then.  

Filiberto, Kar Meng, Marc and I went to the rack and swapped the two cables for WFS1 + WFS2 on D2000552.  The saturaed segment moved with the cable which could indicate the problem is the in vacuum QPD.  

The 105kHz segment went quiet at the same time as the problem on the DC segment.  This happened on a Saturday, before the chamber was vented.  It had been two days of not locking the squeezer or the IFO before this happened.  

Edited to add:  This is the QPD used for filter cavity length control.  We did lock the filter cavity after the segment broke, December 4th.  

Today Rahul and I worked on reducing the last bit of clipping in HAM7.  The power budget shows a couple of percent more loss than we've expected previously, but I don't think we can improve it much right now so this is good enough. QPDA segment 3 is railed. 

This morning we found that we had some loss on B:L2, see Rahul's power budget alog as of lunchtime: 88971.  In hindsight, this was also possible in the power budget that Kar Meng reported before the suspension work this week, 88847. We translated the beam in the -Y direction in the SFI2 aperture, so it would make sense that we might need to translate the lens in the -Y direction.  However, there is no space to move it because the mount is already as close as it can be to SFI2 (photo).  So, we translated the beam using B:M3, using the power meter to judge when we were improving the alignment.  We found that this aperture is very small, there isn't much of a plateau where we aren't clipping.  

After doing what we could to reduce the yaw clipping here we did a careful power budget with the thorlabs power meter, we seem to have  8% loss to SQZT7, 11-14% loss from output of the OPO to the homodyne, which is a bit worse than past measurements ( 65066): 

• Opo 0.97-1mw
• Input to sfi1 0.97 mW
• Output sfi1 0.95 to 0.97 mW
• Hitting zm1 0.95 to 0.97 mW
• Return from filter cavity after sfi1 0.92 to 0.97 mW
• After BL1 0.93 mW
• Input to sfi2 0.92-0.94 mW
• Output from sfi2 0.91-0.92 mW
• After B:L2 0.86-0.91mW 
• After bm4 0.86-0.90 mW
• On the table bottom of the periscope 0.87-0.89 mW
• Before the homodyne 0.86 mW
• Refl power 24mW

We attempted to move B:M3 in pitch to see if we could reduce clipping on B:L2 that way, but that did not improve the transmission.  In pitch we also saw that we increased the clipping with small moves in either direction.  I will try to look up the beam size and aperture size next week to see if this makes sense.  

We adjusted B:B4 and ZM4 a bit to align onto the two irises on SQZT7. 

We also walked the two picomirrors used to center the FC QPDs, with the seed beam which saturates the diode.  From the control room I reduced the power and was able to mostly center, but it seems that QPDA segment three has been railed at 33.9 since November 29th.  

After we finished up, I went back to check the FCGS alignment onto SQZT7, which was not good, so I went back in for a few minutes to get that beam onto the filter cavity reflection diode.  I also had a look at the red + green co-alignment, which looks similar to what Kar Meng posted in 88859.  

We also checked that the new cable routing doesn't block the beam onto H:PD1, we couldn't see the beam but we think it looks like a clear path.  Rahul also took a photo of where the beam exits SFI2.