WP13189 Removed bellows from IOT2L. Guillotines and yellow covers are in place.

Madi, Camilla

This week we went down to EX and installed the OzOptics fibre pig-tailed 532nm 5mW laser, and co-aligned it with the HWS 532nm LED beam.
Out-of-fibre the laser power was 4mW, and after the PBS the power was ~1mW (compare to HWS LED at the same location, power was ~1uW)
The green laser return beam was visible at the HWS camera, with ~50uW power. It was also quite large, and the beam shape indicated clipping.
We took an image of the beam spots with the HWS camera, and also briefly installed a CMOS camera to observe the return beam. We cannot fit the entire beam onto the camera sensor, however you can see enough to observe striations in the beam profile (see attached).
Planning to calculate what lens to put in the path to ensure the beam is correctly sized for the entire path to avoid clipping.

Today, with the BS SUS set to SAFE and the SEI chassis turned off at the rack, Tony, Ibrahim and I started unplugging and logging all of the cables in the chamber at the feedthrus.  I have a master log going which will be posted as an As-Built to the D1003079 BSC2 Flange Feedthru Layout Drawing for future re-plug-in activities.  Pictures of 2 feedthrus prior to unplugging are attached for samples of what I'm talking about.

As well, we dropped the ITMX Elliptical Baffle and Down Tube Sub assemblies from Stage 2 and have a good start on the ITMY one but didn't finish since it has mismatched hardware and we need a different tool.  (In the event we need to put them back up, we left them off to the sides of the chamber to deal with later - the ITMX one is the one closest into the ITMX chamber.)

Also also, we locked the BS SUS, tightened all of the nuts, removed all of the Vibration Absorber Cubes, and put the sock on the full SUS.

Tomorrow we need to:

Add the BS Face cover
Remove a Stay or 4
Finish stowing all of the dangling cables
Finish removing the ITMY Elliptical Baffle
Get on with the Support Tube and SEI work

TITLE: 04/23 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: The soon-to-be-removed beamsplitter is now covered in the chamber with cables disconnected, baffles removed, and keel masses off the top of the ISI. The old "meat locker" was also craned over the X-arm and is staged at the LVEA hi-bay door.
LOG:

[Disha, Elenna, Keita]

Following FRS ticket 37601, we fixed the incorrect wiring of the OMC PZT cables. We determined that both OMCA and OMCB PZTs were wired incorrectly following this diagram D2200276. We found the black dots on the outside of each PZT to determine the positive lead. Disha and Keita noted that for OMCA, relative to the "head" of the manta ray (short side, this terminology is used in the build document T2100190), the PZT closest to the head has the black dot on towards the center of the manta ray, and the far PZT has the black dot towards the outside of the manta ray. For OMCB it is opposite, the PZT closest to the head has the positive lead on the outside, while the far PZT has it on the inside. I am specifically not naming PZTs 1 or 2, or LV or HV, because it was not clear to us which one is which.

We confirmed that the pins were in the wrong location on the cable, so Keita proceeded to swap the pins around.

The schematic diagram suggests there should be a shielding for the PZT cables wired to pin 1, but there was no such shielding on any pin.

OMCA:

far PZT: had pins on 1-6 (plus-minus), we moved these pins to 5-9 (p-m)

near PZT: had pins on 2-7 (p-m), we moved these pins to 4-8 (p-m)

OMCB:

far PZT: had pins on 1-6 (p-m), we moved to 5-9 (p-m)

near PZT: had pins on 2-7 (p-m), we moved to 4-8 (p-m)

We confirmed with a multimeter that there were no shorts between the pins after the pin swap.

Jennie W, Jeff Kissel,

Summary: Can we see a difference in jitter with JAC in the IMC ASC sensors? Short answer, yes.

The IMC has less angular motion with JAC installed at some frequencies - jitter is being suppressed by the JAC so less input beam motion relative to the cavity axis. The QPD readouts are noisier with JAC but there is one new suspension between JAC and the IMC so maybe the beam pointing to MC1 is noisier? MC2 TRANS QPD looks pretty similar with and without JAC, but this makes sense as cavity axis is still well aligned to this QPD. I need some other figure of merit to look at jitter as it only limits the IFO above 20 Hz, see alog #86555 by Sheila.

Since there was no time for a full IFO lock betwen the HAM1 vent and the current vent of the corner volume, we cannot directly check whether the jitter coupling to DARM is better with the JAC cavity.

We have lots of data of the JAC and IMC locked after the installation of JAC, however.

So I compared two times when we had roughly 2W input from the PSL to HAM1. In both cases H1 and the corner were at vacuum to rule out confounding effects from purge air and other sound noise seen when HAM1 was at air.

In both these cases the IMC was locked.

The two times I used were:

2025/11/17 15:38:54 UTC no JAC, during O4c

2026/03/20 00:26:01 UTC JAC installed, HAM1 at vacuum

Here is the ASD measurements for five sensors in the pitch degree of freedom:

IMC REFL WFS A  Roughly the same above 10Hz with and without JAC. Better with JAC between 0.3 and 7Hz.

IMC REFL WFS B Roughly the same above 10Hz with and without JAC. Better with JAC below 7Hz.

IMC REFL QPD A has lower noise now below 5Hz than before JAC installation and much higher noise at frequencies above 10Hz.

IMC REFL QPD B has lower noise now below 3Hz than before JAC installation and much higher noise at frequencies above 10Hz.

MC2 TRANS QPD roughly the same with and without JAC.

Jitter noise is more of a problem in the 20-800 Hz region, which these plots don't tell us much about.

I also need the check YAW

J. Kissel, M. Pirello, B. Weaver

Betsy let us know that she's ready to start disconnecting cables of the ISIBS (the ISI supporting the Beam Splitter) in BSC2. As such, we used D0901301 to guide us, we turned off all three corners of the BSC ISI and T240 Interface Chassis in SEI-C5 U40-38 and U21-19 in the CER. The BSC ISI Interface Chassis are for the on-board capacitive position sensors (both stage 1 and stage 2 CPS), "high" frequency inertial sensors (stage 1 L4Cs and stage 2 GS13s), and the T240 Interface Chassis are for the on-board "low" frequency inertial sensors (stage 1 T240s).

All sensors are OFF as of 1:52p PT (2026-04-23 20:52 UTC).

Thu Apr 23 10:11:23 2026 INFO: Fill completed in 11min 20secs

Closes FAMIS37263

No new issues (LAB2 and LVEA5 are not connected currently), or unreasonable/concerning counts at any location.

Tony, Mitch and I rolled the JAC table IOT1 back into place next to HAM1 +X yesterday. Feet were put down, though we don't think there's a recorded height for the table ot be set to. Bellows reattached. 

Since we've found the BS OpLev damping on and causing the suspension to be moving around more than we'd like during prep for the swap to the BBSS, I went through Guardian nodes looking for all the places the OpLev damping is either turned on or off as a learning exercise for myself:

Basically, the BS OpLev damping is ON during alignment and lock acquisition, and is turned OFF once MICH ASC is engaged. To keep the OpLev damping off for the time being, I've set their gains to zero since the suspension node doesn't change those and we won't be going through any states that do for a while.

When the BBSS is installed, we should think about how if at all these interactions need to change (although I'm sure someone already has).

TITLE: 04/23 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: 10mph Gusts, 6mph 3min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.26 μm/s 
QUICK SUMMARY: More prep for BSC2 cartridge removal today, including craning keel masses off and the start of cable unplugging.

Wed Apr 22 10:12:38 2026 INFO: Fill completed in 12min 34secs

TITLE: 04/22 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: More progress towards preparing to remove the BSC2 cartridge, both in-chamber and out, which is now slated to happen on Monday.

• Walking platforms around the BSC2 ISI were installed: alog89977
• BS OpLev positioning was determined to be good: alog89978
• IOT2L was de-cabled to prepare for its move away from the HAM2 +Y door: alog89975
• More water lines on the TCSX table were replaced: alog89976

LOG:

B. Weaver, J. Oberling

With trends of the BS OpLev posted here and here, Betsy and I decided to also go out and physically look at where the beam is on the OpLev QPD.  The beam itself sits a little bit low and about half-way to one edge of the QPD.  I've attached a couple of pictures, but they aren't the best quality due to low light and difficult access (the BS OpLev sits on the +X/-Y BSC2 HEPI pier, between the pier and the chamber, roughly 7 feet above the floor).  The 2nd picture is viewing the QPD using an inspection mirror, hence why it is flipped w.r.t. the 1st picture.  My phone camera couldn't really pick out the actual OpLev beam, it instead registered it as a "blob" on the QPD (pointed to by the yellow arrows in each picture); the beam itself is roughly in the center of the blob and looks by my eye to be approximately 1.5mm to 2mm in diameter.  The bright spot seen off to the side in each picture is NOT the beam, it is scatter that is reflecting off of a component on the QPD amplifier board.

Based on this, we decided to NOT recenter the BS OpLev before cartridge removal, as the beam is not near the edge of the QPD.

PARTICLE COUNTS in Cleanroom Tent on top of BSC2:  All zeros (or puffs of 10) across from the HEPA flow bank on the opposite side of the ISI pillow, see pix attached.  Counted just after crew left area doing walking plates.  The Tent is working as planned.

PEM BNCs wandering across the West bay was coiled up out of the way of all of the heavy foot traffic.

PEM WEST BAY WALL COIL cables across floor has been disconnected and also coiled up and now out of the way of heavy foot traffic. 

Travis/Mitchell/Randy installed the Walking Plates for better access to the ISI up at the platform level.  Note, after some deliberation and re-reviewing of the drawings (which are actually incorrect), it turns out that you cannot attach the bolts to the underside of the flanges anyways due to in-accessibility of the area.  LLO doesn't recall using them recently either. (Last picture)

TJ, Camilla 

We have almost finished swapping all TCSX on table water lines to new ones as started in alog 89974, photo attached. The new beamdump lines didn't fit the connectors tightly so the old lines have been left for now. The table has not yet been tested for leaks. 

WP 13189

In preparation for HAM2 door removal, the ISCT2 table enclosure cables have been disconnected.