Mon Mar 30 10:08:08 2026 INFO: Fill completed in 8min 5secs

Attached to this alog are the Omicron glitch rate compariosns between O4a, O4b, and O4c. I am posting just for the record, but this was also presented at the LVK in Pisa (see here). For the comparisons, I used roughly about ~3240 hours of observing time (denoted by the H1:DMT-ANALYSIS_READY:1 flag). The exact GPS times used for the analysis were:

O4a: 1372611618 - 1389484818

O4b: 1397692818 - 1422118818

O4c: 1422118818 - 1447502418

The first attached plot shows the glitch rate across each observing period, which includes glitches with an SNR > 7.5, and frequency between 10 Hz - 1024 Hz. The rate was the highest in O4a, at around ~38 glitches per hour. The subsequent glitch rates for O4b/c were lower and similar levels, coming in at around ~11 glitcher per hour and ~10 glitches per hour. In O4a, the glitch rate was high due to increased non-stationary noise from ~10 Hz - 50 Hz (see alogs 71005 & 71092). The following two plots show the glitch rates as a function of SNR and frequency. Most glitches had an SNR below 50, and frequency below 50 Hz.

[Tom, Sophie, Ibrahim, Betsy]

Thursday, Friday and Saturday of last week we assembled a batch of 4 QOSEM In-Vac cables (D2500311) for use at LLO on the BBSS. All cables have passed electrical testing.

On Sunday, Betsy cleaned and began an airbake on the cables, and they have now begun there vacuum bake, which should finish Wednesday evening.

TITLE: 03/30 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    SEI_ENV state: MAINTENANCE
    Wind: 14mph Gusts, 10mph 3min avg
    Primary useism: 0.03 μm/s
    Secondary useism: 0.13 μm/s 
QUICK SUMMARY:

IFO is in IDLE for PLANNED MAINTENANCE

An earthquake tripped some watchdogs - untripped now.

Plans this week prep BHSS and SPI in Optics lab and continue BSC2 platform install.

Sun Mar 29 10:10:19 2026 INFO: Fill completed in 10min 16secs

I've found that the pico mount for 50:50 BS on the REFL WFS sled in front of ASC REFL_A was loose and rotated counter-clockwise seen from the top by a huge amount (1st attachment, orange arrows show the direction of rotation). Our guess is that the BS mount was bumped when we were leaning into HAM1 from -Y door to work on the JAC output periscope. In general, it's hard to rotate the mount clockwise seen from the top even if the screw is not super tight (because the screw tends to be tightened), but it's easier to go counter-clockwise.

When this was found, the beam was hitting the +X-Y edge of the mirror, there was no clear reflection beam found so no beam on WFSA, but somehow the ugly transmission beam with lots of diffraction patterns was making it to WFSB.

We reverted the RM1 and RM2 bias sliders back to O4 level (RM1 PIT=-180, YAW=-57, RM2 PIT=890, YAW=-530) and I confirmed that the centering on the 2" lens was good. WFSA mount was screwed down tight to the post.

RM1 bias was adjusted further (RM1 PIT=-190, YAW=263) to roughly center the beam on WFSB.

At this point I looked at the beam on WFSA and it was still off mostly in YAW but there was also a large PIT offset. These were taken care of by adjusting the picos I've just screwed down.

I enabled the REFL WFS centering which worked right away. LSC REFL diodes are receiving almost equal amount of light. We'll have to make sure that the beam is not clipped on LSC diodes. Anyway, I relieved the ASC using RM sliders and ended up these numbers: RM1 PIT=-192, YAW=274, RM2 PIT=910, YAW=-532.

Sat Mar 28 10:07:24 2026 INFO: Fill completed in 7min 21secs

We're getting <HIHI, MAJOR> alarm about H1:PEM-CS_DUST_LAB2_300NM_PCF, which I cannot trend using NDSCOPE, but I can plot H1:PEM-CS_DUST_LAB2_300NM_RAW and that number has been 30[V?] for the past 6 days.

I've silenced it but could somebody check?

[Jenne, Jennie, Keita, Jim, Sheila, Betsy]

Sum up: We're aligned pretty similarly to a reference time of [ 14 March 2026  02:20:00 UTC ], which is an "IR Found" time in between DRMI locks.  We're back in the same place on IM4 Trans QPD as well as both forward-going POP QPDs.  We have some mediocre PRX flashes.  We are back (in the REFL path) on the same 3 of 4 PDs that we were before re-venting, so we should be in a good place for the team to work on REFL path things tomorrow.

Some details:

• Ref time for all optics *except* PRM is [ 14 March 2026  02:20:00 UTC ].  For PRM I take 20 mins earlier, at [ 14 March 2026  02:00:00 UTC ], when DRMI was locked.  
  • This ref time is when IR was found in the arms during main locking sequence, in between 2 DRMI locks, so the alignment should be overall pretty good. 
• First I put all the optics [IMC, IMs, PRs, ITMX] back to their top mass osems (after figuring out that the DAC Kill was killed, alog 89676).  
• Jim isolated HAM2's ISI. Jim had to unlock HAM3 HEPI to get HAM3 ISI isolated. 
• I touched up optics to top mass osems again.
• Once JAC was locked, I got IMC locked.  After the IMC ASC converged, I moved MC1 so that it was back to its OSEM place, which moved MC3 farther from its reference osem place. So, modulo HAM2 ISI slight change, the IMC is back to where it was I think.
• I then adjusted IM3 to get back to the reference time's place on IM4 trans QPD.  
• I then adjusted IM4 to get back to the reference time's place on the two POP QPDs (they both were happy at the same time). 
• This already gave pretty okay PRX flashes.  
• I moved SR2 to get centered on AS_C.  However, I hadn't checked the BS or SR3. 
• I tried improving the PRX flashes a little with PRM, but wasn't making tons of progress.  May need a bit of touching IM4 / PR2 in addition to PRM?  
• We're seeing DC light on ASC_REFL_B, as well as both LSC_REFLs (although less on LSC REFL B than LSC REFL A).  I have not checked or touched the RMs.  
• Being on the same 3 PDs that we were while under vacuum gives us confidence that we're in a good place at least for fixing up the REFL path.
• The Saturday team may try locking PRX, or may defer to Monday.  Either way, fixing up the POP path will probably happen after the REFL path.

The 4 attachments have vaguely descriptive names. The one from March 14th is my reference time, and then probably the other one that is useful to look at is the End of Day where I left things.  I'm not sure I was seeing PRX flashes at the very very end of the day, so PRM might need some adjustment in the morning. The other two attachments are showing where the suspensions were before I started, as well as showing that I first got back to the reference time osem positions. 

Jennie W, Keita, Betsy, Jason,

Betsy and Jason rolled up IOT1 this afternoon and Keita tweaked the alignment from the top periscope mirror to the DCPDs with the PSL output at 2W. He also re-aligned the trigger PD.

We can now lock JAC in air with the double door cover so we can have the light exiting the chamber but most of the door covered above and below where the beam exits.

I had to run the 'normalise signals guardian state after we closed the table and turned the light off, probably because the signal on REFL PD changed.

We left the light pipe closed and both doors covered at the end of the day.

NB: I accidentally pinged the HAM1 -Y side large table beam dump plate (the one that would catch the scatter from the JAC REFL viewport) with one of the small paper clips we use to hold the two door covers to each other. I will wipe this down tomorrow.

Today, Keita and Oli turned up the power to the fiber again so we are getting about 30 mW out. This is enough power that you can see the beam transmit the input coupler of the OMCs easily on a card. With the room lights dim, you can see flashing of the beam at both DCPDs with a card. Using the IR sensitive camera, we are able to fine tune the input alignment further.

The beam has been well-aligned to OMCA, and the flashing present at the DCPDs looks mostly like mode mismatch, which makes sense because we made no effort to mode-match our input beam to the OMCs.

The beam alignment to OMCB still needs some work. It looks predominantly like a yaw misalignment, so we need to make some finer adjustments of the upstream optics.

Since all of the BHSS optics have been pre-angled using the clocking tool, I followed the map on slide 86 of T2100190 to place the lenses, mirrors and beam dumps. Just by eye, I can tell we will need to fine tune this alignment further once we have laser beam. I was unable to place one beam dump because it goes roughly where we are pooling the OMCA cables. Once we can route and clamp those cables properly, there will be room for the dump. I haven't placed the QPDs yet, they are still bagged. I also placed the three head optics randomly, since they can't be placed until the OMC iris template is removed.

As a reminder, the order of operations here is to use the iris alignment template to get good input alignment to both OMCs. Then, this template is removed so we can use other precision templates to align the three optics that go at the head of the manta ray: mirrors A/B-R1 and 36-R1. Then, we can finish the rest of the beam paths to the OMC QPDs.

I took a phone video of OMCA flashing and managed to screengrab these two photos from the videos: DCPDA, DCPDB

I returned to the slider positions where we had good green and IR flashes in the filter cavity from Wed 89629.  Since this time of good flashes the H:M2 pico was reverted to 0 (it's setting during in chamber work), so the green flashes weren't as high as they were on Wed.  Screenshot attached here. In this alignment I went to SQZT7 and looked at the green reflection, it looks like an oval but is coming to the persicope.  (photo)

While at the table, I moved the picomotor for H:M2 X to -710, which is where Tony and I had put it 89596 and where we had both IR and green flashes good.  I could see the beam move on SQZT7, but it wasn't a big move, and after pico'ing it looks like we still have an oval beam making it to the table..  (photo, screenshot)  On the cameras we can clearly see cavity flashes in green but the IR flashes were off the camera, so I went to FCES and centered the flashes on the IR camera (using the seed).  I also went back to sqzt7 and aligned the FC green refl onto the diode.  

While I was there, I watched the green beam on a card while I moved suspensions to see how much freedom we have to move the suspensions and still get the green beam out of the viewport.  I could move ZM1,2,3 and FC1 by a couple hundred urad in both pitch and yaw (although not in either direction), so there is a reasonable adjustment range.  Moving these didn't impact the oblong shape of teh beam, so it doesn't seem like that is caused by clipping.  I then moved the ZM2 psams settings, and saw a big change in beam shape, it became more round looking on a card for strain guages of 4.15 or 5.15 (our usual setting is 3.15).  

I left the alignment back at the one that gave good flashes for IR and green (up to 10, is off in pitch), and with the CLF IR flashes are max 0.15 counts.  

TITLE: 03/27 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: The +/- Y doors were taken off HAM1 this afternoon alog89672, See Jims' alog89673 for the current CS seismic configuration. I'm not sure if the intercom is working, I didn't hear myself after plugging it in and trying the offices. THe LVEA is now is LASER HAZARD, as is the optics lab.
LOG:

• 16:08 UTC HAM3 and BSC2 SUS to safe, their SEI states were already in safe (ISI_DAMPED_HEPI_OFFLINE, and READY / LOCKED) for Fil and Marcs cabling/electronics work
• 16:12 UTC SUS BS wd trip, OSEMs inputs are disconnected it looks like, came back at 21:00 UTC, the pointing still looks the same pretty much the same
• 18:08 UTC SPI laser shuttered in Optics lab
• 18:15 - 18:40 Sophie to CHETA lab
• 22:21 UTC BS ISI ST1,2 WD trip, CPS glitch a minute later

F. Clara, J. Kissel, S. Koehlenbeck, J. Oberling, M. Pirello
D2400110

Today we picked up where we left off with the install of SPI into H1. 
Where we last left things, we'd installed a new SPI pick-off of ALS/SQZ beam in Apr 2025 (see ECR E2400083 and results in LHO aLOGs 83989, 83996, 83978). Back then, we had ended the work with the input to the fiber collimator within the PSL dumped.

With Jason and Sina in the PSL, we confirmed that the SPI path was still blocked. 

However, we also realized/remembered/confirmed that the entire ALS/SQZ/SPI path had 25% less power -- We've been running the PSL at lower power allocation downstream of the PMC since Sep 2025 to prevent issues we'd found with the currently installed EOM after a power outage triggered a dust monitor to spew out dust into the PSL (see that saga in e.g. LHO:87109 LHO:86966). They found the power at the SPI pick-off was 140 [mW] instead of the 188 [mW] we left in Apr 2025 (see LHO:83996).

(Using labels in the half-up-to-date drawing D1300348)
Jason and Sina rotated ALS-HWP2 upstream of ALSPBS01 to restore the nominal 50 [mW] into the ALS/SQZ pick-off and ~200 [mW] (190 [mW] measured). This means there's ~50 [mW] less out to ALS / ISCT1 than before today.

Then with the SPI pickoff still dumped, we installed a 30 [m] patch cord*** from the PSL optical table, out the mouse hole between the +X wall of the PSL enclosure and HAM1, then up running along the upper racks to waterfall down at SUS-H2. The fiber sits within the typical orange tubing. Per D2400110, this is SPI_PSL_001, and it's labeled as such on both ends.

After install, I connected the SUS-R2 end to a Thorlabs S121C power meter with S120-APC2 fiber adapter. 
With this installed (making the system laser safe at SUS-R2 end), Jason/Sina unblocked the SPI pickoff input. 
With 190 [mW] in, we measure 187 [mW] out on the other end. 98% transmission, pretty excellent. Almost unbelievably excellent but we weren't rigorous with our uncertainty and systematics.

Happy with this result, we then blocked the SPI path again, and re-capped the SUS-R2 end for final dressing in the racks.
We'll unblock again when we're read to connect it to the Laser Prep Chassis.

***Patch cord details:
Manufacturer DIAMOND
DIAMOND Part Number: ENS/1094388
Customer Part Number: 9711228
Patchcord SM L=30 PM
2xFC 2mm APC (i.e. 2mm narrow key FC/APC on both ends)
tran 6,6/125/245 PAND 980nm