Writing this alog to clarify some mistakes we have made regarding the naming of DCPDs. Jeff clarified to us on call this morning that the naming convention is A- photodiode on reflection, B- photodiode on transmission.

Therefore, here is the now corrected information about which high QE photodiodes are installed where, along with cabling and pin numbers:

OMCA (SN 103)

• DCPD B (TRANS)
  • DCPD: 1D-20
  • Housing: SN 10
  • cathode/anode/case wired to pins 1/2/6 of cable D2300118
• DCPD A (REFL)
  • DCPD: 1C-12
  • Housing: SN 06
  • cathode/anode/case wired to pins 4/5/9 of cable D2300118
• PZT cable D2300120

OMCB (SN 105)

• DCPD B (TRANS)
  • DCPD: 1C-14
  • Housing: SN 002
  • cathode/anode/case wired to pins 4/5/9 of cable D2300119
• DCPD A (REFL)
  • DCPD: 1C-10
  • Housing: SN 008
  • cathode/anode/case wired to pins 1/2/6 of cable D2300119
• PZT cable D2300121

Fri Mar 27 10:10:14 2026 INFO: Fill completed in 10min 10secs

I've added a "degraded state" indicator to the VACSTAT block on the CDS Overview MEDM (magenta oval in attachment). This circle is either the same light green as the block colour, or is a darker green to show at least one gauge has been disabled.

Currently we are running with HAM1 PT100 disabled in VACSTAT due to the vent.

The VACSTAT detailed MEDM (snippet in lower part of attachment) has a "NUM_GAUGES_DISABLED" line added, which turns RED if non-zero.

TITLE: 03/27 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: CALM
    Wind: 4mph Gusts, 1mph 3min avg
    Primary useism: 0.03 μm/s
    Secondary useism: 0.27 μm/s 
QUICK SUMMARY:

• HAM1 doors are coming off today +Y, -Y
  • Later... set tables back up to lock JAC in air and work on REFL and POP paths

Since yesterday, we have received an answer from Ali and Keita, that the determination is that the cathode and anode pins are in the correct location. There is a longer explanation about what's going on here and which diagrams are wrong, but I will leave that to them. Therefore, the only cable work that needs to be done is to adjust the pins on our "bad" cable, and then switch the DCPD cables between OMCA and OMCB.

Morning (no cable work):

Oli and I pulled the first contact that we left from yesterday. We just need one 50/50 45 deg AOI mirror for BHSS, and we were able to completely clean two of this type. More of these mirrors will be needed for the greater BHD layout, so Oli and I need to revisit the other three that still are not clean. For now, they are stored on the flow bench in clean single cases.

We went to begin the BHSS alignment, and found that no laser beam was coming out of the fiber. Some time between this alog, when Camilla and Oli aligned the beam into the fiber, and now, the beam was misaligned again. We think one of the mirrors to the fiber coupler was bumped. Correcting this took a little while. Oli had to leave, so Keita and I continued with the alignment. Luckily, our downstream alignment is still good- with the iris alignment template placed on the BHSS, we can see the beam comes down the center of both irises to OMCA.

Most of the beam reflects off the OMC, so Keita and I started turning up the power into the fiber. At some point, we turned up to 20 mW coming out of the fiber. We could see a faint beam transmit from the input coupler and make it to the output coupler. However, we still had a hard time seeing any beam make it to the DCPDs, probably because the power is still very low. We set up a beam block of the OMC REFL path for now, since it just goes right back off the suspension. At this point, we realized it's probably not a good idea to put so much power into the fiber, so we lowered the power again to have about 2 mW coming out of the fiber.

Afternoon (cable work):

Keita and I proceeded to fix the cables. We first checked which cables went to which pins:

Cable D2300119 (for OMCB): longer is on trans PD, goes to pins 4/5, shorter on refl PD, goes to pins 1/2

Travis, Jordan

HAM1 was vented today per M1300464 and E2300169, no pressure change in the corner during the venting. Dewpoint and particle counts collected prior to air admittance (-43C dew point).

Once the laser tables were moved away from the chamber, we vented the annulus system and all but 4 bolts were removed from both +Y and -Y doors in prep for door removal tomorrow. 

Closing WP 13123

TITLE: 03/26 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: HAM1 was vented and the bolts have been broken, doors should come off tomorrow. BHSS work continues, and the LVEA is now in Upgrade Laser Safe.
LOG:

17:00 UTC Jordan went over the VAC checklist and I confirmed the picomoters were off, the JAC PZT scan was disabled and its Driver offset was 0, and that the ISI and HEPI were in their safe states.

17:08 UTC HAM1 pressure starts to rise

17:11 UTC ISI HAM1 wd tripped

20:27 UTC Red alarm Dustmon6 by HAM6, 10.8k and 17.5k counts for the 0.3 and 0.5 um particles

21:58 UTC The SQZ laser was keyed off, The LVEA is now in Upgrade Laser Safe

22:00 UTC The tables by HAM1 were moved

23:05 UTC HAM2 ISI tripped from the HAM1 crew breaking the bolts, and the HAM1 sw watchdog

23:09 UTC RM1 and RM2 wd tripped, the HAM1 CPSs were glitching as well

23:31 UTC HEPI HAM1 watchdog tripped

I reset a PT100 VACSTAT alarm at 10:12 and disabled HAM1.

Thu Mar 26 10:11:54 2026 INFO: Fill completed in 11min 50secs

On Monday, Randy, Jordan and the FAC team craned the HAM3 cleanroom over into the appropriate place for HAM3 entrance for installation planned next week.  The cleanroom is now up against the BSC2 Platform.  As well, Kim and Nellie have been cleaning the HAM3 cleanroom.

On Tuesday, Randy craned into place and attached the new Installation Platform Sections G and F to the BSC2 platform.  Handrails will be installed next.  These platforms allow access from the eMod cleanroom to the BSC2 cross flow Dome cleanroom and platform, as well as provide added walking space between BSC2 and BSC3.  They also form 2 sides of the BSC3 platform which will be needed in subsequent vents.  Recall, this new LHO BSC2 Installation setup is part of the readiness review for install at https://dcc.ligo.org/E2400329-v1, and is part of a bigger plan to add sections around BSC3 and BSC1 to make a larger platform instead of moving them and encountering interferences other items like racks, trays and equipment.

TITLE: 03/26 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: USEISM
    Wind: 6mph Gusts, 4mph 3min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.55 μm/s 
QUICK SUMMARY:

• Zone5_I has been a little warm since the HAM1 CR has been turned on, its just off the plot but it looks stable
• HAM1 vent work continues
• More LVEA craning

"It is a truth universally acknowledged, that a single man in possession of a good fortune, must be in want of a wife"

- Jane Austen, opening line of Pride and Prejudice

But unfortunately for both us and them, sometimes those men are winged termites in the Optics Lab.

As Elenna and I were cleaning up our work in the back optics table this afternoon, we noticed a few winged termites, and ended up finding maybe almost 10 in total walking around on the floor in the back area of the optics lab near the wall mounted cabinets between the two cleanrooms. We got rid of them but couldn't find where they had come from. I'm wondering if they're maybe coming from an opening under one of those cabinets? Last year this happened but those came out from under the flow benches along the wall - not sure if this is part of that same colony that survived or a different colony.

To summarize the ongoing issues from yesterday:

• we determined that the cables (DCPD and PZT) attached to each OMC are mixed up
• one cable has incorrect wiring, because the ground pins are not where they should be (pin 2 and 5 are ground instead of 6 and 9)
• we're not sure if the polarity is correct on the diode

Keita and I have decided that swapping cables can possibly be done without removing the DCPDs. We're going to determine OMC A and OMC B based off of the PZT cable, and then swap the DCPD cables. We're waiting to hear the final verdict on the diode polarity to do pin adjustments and cable swapping.

In the meantime, Oli and I installed OMCB on the suspension and bolted it down using the OMC alignment template. We have placed the butterdishes over OMCA and B, but we haven't secured them yet with viton clamps while we continue to do work on the OMCs. The cables are only loosely clamped.

Next, Oli and I worked first contacting the remaining optics for BHSS- two HRs and one 50/50 splitter. The HRs were finished today, installed in their mounts, and placed randomly on the platform. The 50/50 splitter is still being FCed and should be ready in the morning. Once that optic is installed, we will proceed with the alignment of the OMCs and optics.

One vertical clamp is still missing from OMCB, but we should be able to install it once the helicoils and such arrive.

Sheila, Camilla.

We decided to pause on looking for the FC alignment and look at SQZ alignment into the IFO. To check our irises and possibly look for scattering shelves. 

Locked SEED_DITHER with 75mW into fiber. Moved ZM3 to get OPO_IR PD up to max 0.9mW. Opened BeamDiv and after aligning SRM, mis-aligning SR2, could see beams on AS_A,B and C. AS_A and B had a similar size ~60 to reported before (e.g. 86965), but there was less power on AS_C: 4e-4 rather than the previous 7e-4.

We used Ryan's DRMI time from 89573 to put OM1, OM2 and SRM back. The with the SQZ SEED injected, we tried to use SQZ centering loops to center on AS_A and AS_B, this didn't work quite as expected. ZM4 kept saturating although these loops had worked Janaury 19th, before moves were done on the VOPO to help with clipping e.g. 88966.

Then went back to alignment on Jan 31st with 88976 with ZM1,2,3, 4,5,6 FC1. And took OM1,2,SRM to the January 19th positions. However here we saw no light on SQZT7 OPO IR PD, HAM7 WFs or in HAM6 on the AS_A,B,C diodes. This was done at 23:10 UTC. Comparisons of osems attached. The sliders to get these osems values are fairly different, see attached, so I also tried going to these slider values, that gave me some light on SQZT7 IR PD, HAM7 WFS and FCES with SEED injected, see attached. HAM6 AS diodes saw nothing. 

We previously reported that the wiring to ground on the OMCA DCPD dsub9 cables seemed odd, see 89562. There appears to be two conflicting diagrams of the pin wiring, D2200276 and D2300119. Neither of these diagrams follow the correct pin naming practice either.

Today, Oli and I checked the ground connectivity for the OMCB DCPD dsub9. The case ground is wired to what is labeled pins 6 and 9, according to both of the diagrams above and also proper convention. However, this is different from OMCA, where the case ground is wired to pins 2 and 5 (following the incorrect naming of the diagrams above), or pins 1 and 4 (following correct naming conventions).

So either way, we have two different wiring set ups for OMCA and OMCB. We have only checked the ground pins so far, and it seems like we should confirm the cathode and anode wiring as well.

To summarize:

- we have two different diagrams for pin wiring

- OMCA and OMCB are wired differently from each other

- the diagrams are not following proper pin naming convention which is making this more confusing

Elenna, Oli

Summary: OMCB has its DCPDs installed and most of its stoppers (barring one that needs to be retapped + helicoiled). OMCA has been aligned according to the OMCA / OMCB install template and is ready for laser alignment. Cabling for both OMCs should be good to go.

After last week's issue of the OMCB DCPD A (TRANS) missing a diode hole (89583), we were able to clear up the issue and fix it (89606). Elenna then installed the DCPD B (REFL) diode. Note that once again there were tiny metal shavings below where the DCPD's were installed, which we picked up with a qtip that we wet with iso. Once we had both installed (pic), we installed the rest of the stoppers around OMCB. The only one we didn't install is one of the vertical stops. This is because there was an issue with the helicoil last week, and we ended up having to remove it. We think this might be due to an issue with the threads, so we are waiting on a 3/8"-24 tap to retap the hole before installing a new helicoil. Because we don't have this stop yet, it doesn't really make sense to fasten on the butter dish, but we might just sit it on today to hinder dust accumulation.

We also realized that the PZT cables were going to be way too short to reach the cable pylons for both OMCA and OMCB, so we very carefully opened the peak cable wraps on the OMCs and took out what we think should be enough. On OMCB we noticed that the little copper wrap for one of the PZTs was not right above the PZT as it should be, but instead was on the other side of the peak cable wrap and was only wrapped loosly around one of the cables. Because of this we just removed the wrap. The cables right above the PZT are looking fine and don't look like they need anything to hold them together.

I had been confused about the OMCA / OMCB install template for the past few days, since installing it was putting OMCB further back in its slot than OMCA, but I was able to confirm yesterday in eDrawings that OMCB is actually supposed to be an extra 1 mm away from the front of its slot as compared to OMCA, so we moved OMCA into position and bolted it down.

I also went in and installed the magnet mounts for the OSEM magnets (without the magnets), as well as the big mass on the back of the BHSS.

Installed serial numbers:

OMCB (SN 105)

• DCPD A (TRANS)
  • DCPD: 1C-14
  • Housing: SN 002
• DCPD B (REFL)
  • DCPD: 1C-10
  • Housing: SN 008