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Reports until 07:38, Monday 18 May 2026
LHO General
ryan.short@LIGO.ORG - posted 07:38, Monday 18 May 2026 (90260)
Ops Day Shift Start

TITLE: 05/18 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: 12mph Gusts, 6mph 3min avg
    Primary useism: 0.03 μm/s
    Secondary useism: 0.15 μm/s 
QUICK SUMMARY: No alarms over the weekend, temperatures looking normal, dust counts low as well. The same 31 channels are disconnected from the EDC since the CS HEPI pump controller is still down.

Likely continuing with alignment work in HAM2 today following the ISS array replacement.

H1 AOS
robert.schofield@LIGO.ORG - posted 12:41, Sunday 17 May 2026 (90258)
Chamber cleaning did not reduce subsequent particle counts: BSC2 chamber cleaning investigation

TJ and I cleaned the BSC2 aluminum floor, the bottom of the chamber below that, feedthrough nozzles, support tubes and their nozzles (see figure for photo of cleaning and some of the stuff we found). The particulate level while walking around gently did not change significantly from before to after the cleaning (see table below). This and the other cleaning experiments reported in the table suggest that, at the current state of cleanliness,  the dominant source of suspended particulate is the people and the things we bring in rather than dust that we stir up by moving around. 

The dust counts generally returned to low levels a minute or two after the activities in the table.

Just as patting clothes produces more dust, we found that rapid movements produce more dust in the chamber than slow movements. The linked video shows the movement speed and the wiping speed that produced the lower levels in the table below: slow chamber speed. 

Recommendations:

1. The chambers are currently clean enough that general cleaning is probably counterproductive.

2. Move slowly when possible. This can reduce the particulate suspended from your bunny suit by an order of magnitude.

 

Activity

Particulate per cubic foot*

0.3 um

0.5 um

Standing still in chamber

0

0

Walking around gently in BSC2 before cleaning

150

80

Walking around gently in BSC2 an hour after cleaning aluminum floor, bottom of chamber, and all nozzles

170

85

Wiping aluminum BSC chamber floor

200

50

Wiping feedthroughs and their nozzles

200

70

Cleaning support tubes and their nozzles

100

60

Slow wiping of BSC floor under aluminum floor towards center (lowest part)

200

50

Fast wiping of BSC floor under aluminum floor towards center (lowest part)

800

500

Deploying vacuum hose and accessories

1000

800

Vacuuming up material wiped to center of BSC floor

200

50

Vacuuming bellows with tube accesory that fits between them

600

150

Vacuuming walls in spool piece

200

50

Vacuuming aluminum floor in chamber while hose assembly is dragging

600

200

Waving hand up and down while standing still outside the chamber

150

50

Waving hand up and down while standing still inside the chamber, monitor at same relative position

200

70

* Particle counts are aproximate averages, mostly of 1 minute samples. Repeats suggested that differences in the table of a factor of two or greater are significant. Quiet controls were taken in between reported measurements to ensure that measured levels were not significantly affected by previous activities.  Monitor: Met One  GT-521S laser particle counter 

TJ and Robert

Non-image files attached to this report
Under-the-floor.pdf
H1 IOO (INS, IOO, ISC)
keita.kawabe@LIGO.ORG - posted 23:19, Saturday 16 May 2026 (90259)
IMC alignment work on Friday, not that much success (Keita, with remote help from Elenna and Sheila)

One problem solved, two problems found.

Clipping on IFO REFL baffle is gone.

The problem of IFO REFL beam clipping by the last IFO REFL baffle in HAM2 (see alog 90251, especially this picture) seems to have been caused by a huge PRM change in the PRM alignment sliders made on Monday May/11/2026 past 1700 local time (that none of us knew/remembered/understood).

Once Sheila reverted PRM back to March/2026 alignment, changing the IFO REFL beam path (but not the alignment into ISS path), IFO REFL was not clipped any more even though it looked low on the baffle (IFOREFL_baffle.mp4). LSC and ASC REFL sensors on HAM1 ISI saw the flashes right away without any adjustment of RMs, and the flash peaks were already reasonable. According to Sheila,  compaing to a time when DRMI was acquiring in November:

All of these were a good sign.

Forward-going beam into the IM4 is clipped by the baffle in front of IM4, and the IFO REFL beam is clipped by the baffle at the -Y edge of the IFI.

Unfortunately I've found that there were two other clipping points that I must have missed yesterday using IR viewer. See clipping.png, sorry for a blurry through-IR-viewer picture shot from the distance. Go back to HAM2layout_annotated2.png to figure out which baffle is what.

There's a baffle in front of IM4 between IM4 and IM3, and the forward-going beam is slightly clipped at the +X edge of that baffle.

Also the IFO REFL beam is clipped by the baffle installed at the -Y edge of the IFI. I know this is IFO REFL because the bright spot goes away when I block the beam on PRM by a sheet of aluminum. I cannot quite tell from the picture which edge of the baffle is clipping, but I think it's also +X edge.

In the past, when PRM spot position was measured with full IFO, it was like a mm off according to Sheila, so it's hard to imagine that the beam was clipping on the baffle in front of IM4.

Changing IMC alignment (trial 1, didn't fix clipping).

We decided to back off the changes we've made  for MC1, 2 and 3 since Monday and revert back to in-vac March alignment. If we have to make a huge adjustment to JM3 to follow the IMC, maybe the beam coming from JM3 is suspect (which means that the MC2 trans path is somehow suspect too).

Before I did anything, the starting point was captured in alignment_2026-05-15_16-14-21.png.

MC1/2/3 was reverted just based on slider values and not using OSEM readings as per alignment_2026-03-18.png.

Then JM3 was adjusted in PIT and YAW to give the maximum transmission measured in IM4_TRANS_NSUM. Actually I didn't move JM3 as much as I expected.

That alone couldn't recover a good 00 mode flashing so I moved MC2 and MC3 to follow the input beam.  MC2 moved back closer to the position this morning.

After that I felt as if it was somehow easier to optimize further using MC1 as well as MC3, thinking that it would be a minor adjustment but somehow ended up moving MC1 by a large amount after iterations.

My end point is captured in alignment_202605151726_sliders.png.

Without IM3 and IM2, the beam was still on IM4_TRANS as well as ISS QPD, the flashes were good, so I looked at the clipping on the baffle in front of IM4 as well as the baffle at the -Y edge of the IFI, and they were still there. IFO REFL baffle was still not clipping.

Will have to think about what these all mean.

Images attached to this report
Non-image files attached to this report
IFOREFL_baffle.mp4
LHO VE (VE)
gerardo.moreno@LIGO.ORG - posted 12:35, Saturday 16 May 2026 (90256)
Oil added to Kobelco unit

(Jordan V., Gerardo M.)

Late entry.

The compressor that produces the purge air developed a seeping leak of oil a few weeks ago, second oil leak, located were a previous work was done last March, see here for details, then the leak turned into a drop by drop leak, then other hose joints started to seep, we called the vendor regarding the leaks so they can fix the issue, they should be here next week.  However, due to the amount of oil the unit has lost, we decided to add some oil to the compressor.

Before adding oil, the chambers were checked that all soft covers were on, operator was notified that the compressor was getting shut down, Kobelco unit was turned off.  All doors for the compressor unit were opened, air moving equipment was added to cool down the compressor for about 1 hour, then oil was added until the sight glass showed a good level.  Unit was restored and turned on.  We allowed the unit to run one hour to achieve nominal temperature, then we opened the purge air to the chambers. DP at the drying towers showed -78 degrees C.

Attached are a few photos, the front display shows the oil temp TT4, nominal is above 110 degrees F, and the unit alarms above 170 degrees F.

 

Images attached to this report
LHO General
ryan.short@LIGO.ORG - posted 16:38, Friday 15 May 2026 (90255)
Ops Day Shift Summary

TITLE: 05/15 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: Alignment continued in HAM2 today after the Kobelco unit was worked on this morning. Ibrahim has been tidying up around the test stand area and wrapping up parts from the BSFM. Robert continued grounding studies at End X, and Jeff worked in the optics lab on SPI. His work requires leaving the laser running over the weekend in the optics lab; curtain is closed and proper signage is up.
LOG:

Start Time System Name Location Lazer_Haz Task Time End
19:43 SAF LASER HAZARD LVEA YES LVEA IS LASER HAZARD Ongoing
14:59 VAC Jordan LVEA - Check covers/RGA, shut down Kobelco 15:11
15:32 FAC Kim LVEA - Technical cleaning 17:02
15:41 SPI Jeff Opt Lab Local SPI prep work 19:33
16:25 VAC Jordan LVEA - Checking RGA 16:30
16:39 FAC Randy LVEA - Plugging in equipment 17:31
16:40 SUS Ibrahim LVEA - BSFM housekeeping 19:21
17:20 FAC Kim LVEA - Technical cleaning 18:00
17:41 ISC Keita LVEA Y HAM2 beam alignment 17:55
17:55 PEM Robert EX N Grounding studies (in/out all day) Ongoing
17:58 VAC Jordan LVEA - Ramping up RGA temp 18:04
19:47 ISC Keita LVEA Y HAM2 beam alignment 21:42
20:40 VAC Jordan LVEA - Checking RGA 20:45
21:32 SPI Jeff Opt Lab Local SPI prep work 22:57
21:49 SUS Ibrahim LVEA - BSFM wrap, bag, tag Ongoing
22:38 EPO Oli +2 LVEA - Tour Ongoing
23:05 VAC Jordan LVEA - End-of-day RGA check 23:10
H1 SPI
jeffrey.kissel@LIGO.ORG - posted 16:27, Friday 15 May 2026 - last comment - 11:26, Friday 26 June 2026(90253)
SPI Pathfinder ISIK Transceiver Status 
J. Kissel

Quick summary of status and things done before the weekend:
    2026-05-14 
       - Secured new D2400143-v6 breadboard to 1"Dx6"L posts
       - w/ J. Freed Helicoiled most holes
  
    2026-05-15
       - Finished helicoiling and confirmed all holes have helicoils.
       - Brought out IXM100 mounts that are to replace CVM100 mounts, confirmed left vs. right-handed assignment
       - Fit-checked (success!), then installed new version of 45 deg periscope adapters to M_M4 and M_M5 mounts. 
       - Aligned periscope adapters as best possible by eye
       - Migrated over and re-cabled up all photodiodes per wiring diagram and cable routing defined in LHO:90228.
       - Migrated R_F1 and M_F1 fiber collimators, confirming and adjusting alignment of slow-axis w/ vertical flat.
       - Re-connected optical fiber input to each collimator.
       - Re-introduced beam on to breadboard confirming that NPRO and Laser Prep Chassis still work as good as we left it. 
       - Measured raw power from R_F1 and M_F1 fiber collimator output using S121C power meter.
       - Aligned R_F1 and M_F1 fiber collimator output using 
           - D2500080 alignment iris target assemblies
           - D2400143-v6 holes 89 + 101 for R_F1 and 101 + 80 for M_F1 and 
           - S121C behind the "far" iris, maximizing power throughput.
       - Migrated R_P1 and M_P1 thin-film polarizers.
       - Measured P-pol (TRANS) and S-pol (REFL). 
       - Migrated D_R_P1 and D_M_P1 beam dumps.

Optical power going into the mock PSL input fiber is ~195 [mW] as we left it, and internal laser prep chassis reads 7.8 [V] implying that input power to the chassis is the same 173 [mW] we set it to, to match the real PSL input (see LHO:89693).

RF power on power monitors from prep chassis are as expected, in the 750 +/- 10 [mV] range.

Measuring power with our trusty S121C with ThorLabs PM100-D readout (confirmed to be measuring at 1064 [nm] wavelength):
Images attached to this report
Comments related to this report
jeffrey.kissel@LIGO.ORG - 16:28, Friday 15 May 2026 (90254)EPO, SPI
Link 

Josh and I hard at work doing helicoil science. Photo credit: Ryan Short.
Images attached to this comment
jeffrey.kissel@LIGO.ORG - 11:26, Friday 26 June 2026 (90776)
Link 

A belated photo from the day that both D2400143-v4 and D2400143-v6 were side-by-side, right before the helicoiling and transfer of components began.
Images attached to this comment
LHO General
ryan.short@LIGO.ORG - posted 07:42, Friday 15 May 2026 (90252)
Ops Day Shift Start

TITLE: 05/15 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: 6mph Gusts, 3mph 3min avg
    Primary useism: 0.06 μm/s
    Secondary useism: 0.13 μm/s 
QUICK SUMMARY: Work in HAM2 continues today as part of the ISS swap, but not until the Kobelco unit has had some maintenance done this morning. No in-chamber work allowed until that's finished. 31 disconnected channels on the EDC since the corner HEPI pump controller appears to still be down.

In other news, a M6.7 EQ out of Japan is rolling through, and it's a beautiful morning on-site.

H1 PSL (INS, IOO, ISC, PSL)
keita.kawabe@LIGO.ORG - posted 17:41, Thursday 14 May 2026 - last comment - 20:58, Saturday 16 May 2026(90251)
Done with ISS array alignment, not yet ready to go laser safe due to IFO alignment mystery (Rahul, Elenna, Keita)

Good news is that we're done with the alignment of the ISS path. Pictures and details are to follow.

Then I reinstalled the last IFO REFL baffle right in front of the HAM2-HAM1 septum window. (The baffle was removed after marking the exact position using three temporary dog clamps on the ISI on day 1 because it was in the way, I was supposed to record that in alog 90158 but forgot. I'm absolutely sure that the position of the baffle was restored within 0.1mm of the original position.)

Bad news is the IFO REFL was clipped on that baffle. 00 mode flash isn't clipped that much but horizontal modes certainly are. That was not THAT surprising because the IMC alignment was/is not great (see my comment 90224). This looks to me that the uncontrolled degree of freedom of the IMC is wrong regardless of the reason why a huge alignment change had to be made to center the MC2 TRANS QPD.

Good news is the ISS path alignment is not impacted by that, at least greatly, because we made sure that the beam hit the right location of IM4 TRANS as well as ISS array QPD before we did anything in the ISS path. Note that the baffle clipping the beam is not in the ISS path.

In other words,

  • the beam position on MC3 might have been poor but we used IM3 and IM2 to steer the beam INTO the ISS path such that the alignment there is reasonably close to in-vac alignment,
  • when the beam coming out of MC3 is brought back to the good position/angle, we can bring the beam back onto IM4 trans using IM3 and IM2,
  • if the beam is not found on the ISS QPD at that point, we can scan IM3 (and IM2 if necessary) further to find the beam,
  • and use the first pico for the ISS array path to keep the beam on the array QPD while slowly bringing IM3 (and IM2 if that's touched) back to the good angle.

However, since we don't want to revisit HAM2 once we close it, I'd like to understand what's going on for the IMC/IFO alignment. 

Comments related to this report
keita.kawabe@LIGO.ORG - 20:58, Saturday 16 May 2026 (90257)
Link

For location of things, refer to HAM2layout_annotated.png. Blue line = IMC reflection. Red line = IMC transmission. Orange line = IFO REFL rejected by the IFI. Green things are baffles (two-hole baffle and the last IFO REFL baffle are circled in green).

The alignment status at the start of Thursday morning:

The beam was very high on the two-hole baffles but was OK on the input hole of the ISS array. See alog 90237, see this picture as well as this, and this video. This just meant that we were shooting down the beam from the 1" lens toward the center of the array QPD.

Work done on Thursday:

We moved the beam down using the two pico mirrors such that ultimately the beam goes through the center of the input hole of the array and reasonably centered on QPD.

Detailed procedure was:

  • Use the first pico mirror until the flash is just seen in segment 3 and 4 of the array QPD (i.e. PIT=-1 if this were a stable DC light) and then use the second pico mirror to bring up the beam until the QPD was roughly centered. Measure the beam position on the baffle holes as well as the ISS input. Repeated until the beam comes close to 1/8" or so of the center of the input hole of the array.
  • Install the biggest array alignment aperture tool (D1300986, -03 variant with 2.4mm diameter hole) in the hole of the array. Use pico mirrors until no clipping at the alignment aperture tool is visible using IR viewer and the QPD is roughly centered at the same time.
  • Repeat with the middle sized alignment aperture (-02 variant with a 1.6mm hole). That is enough as the final adjustment before pumping down.
    • We didn't bother to use the smallest alignment aperture (-01 variant with 0.79mm hole). Refining the alignment at that level for in-air initial alignment is pointless, the beam WILL move once things are in vacuum and the IMC is properly aligned and IMs adjusted. What ultimately matters at this point is to make sure that, once that in-vac adjustment for IMC/IFO is done, the beam could be found on the QPD. From there on we need to fine-tune to find a good ISS array alignment and minimize the jitter coupling.
Status after Thursday's work:
right_baffle_hole_spot.png (seen from +Y), 2nd_pico_spot.png (from -Y), 1inch_lens_spot.png (from -Y) and 2inch_lens_spot.png (from -Y) show the beam spot on various positions in the order of the distance from the array in the ascending order. You can see that the height on the right baffle hole as well as the second pico mirror are pretty good. Pictures of the lenses have significant parralax because of the distance between the card and the lenses and because of the camera height, but the beam doesn't seem to be centered on the lenses. I don't see that as a problem, it's fine as far as the beam is far from clipping. 

We have found no unexpected behavior here, I was surprised that the process was easy and things made sense given the difficulty people had in the past to improve alignment of the array in vacuum with the old unit. That's probably because the beam was already clipping back then.

The only thing was that the YAW actuator of the second pico mirror didn't have much range to start with even before we moved anything. At some point it didn't hit its end of the range but was close (2nd_pico_position_before.jpg). Since we need a healthy headroom for adjustment both ways, I relieved the pico by mechanically rotating the pico mirror assy (2nd_pico_position_after.jpg).

IFO REFL beam was clipping on the baffle:

See IFO_REFL_baffle.jpg
Images attached to this comment
H1 SEI
jim.warner@LIGO.ORG - posted 17:04, Thursday 14 May 2026 (90250)
CRS progress for the week

To close out the week, we got stops and shroud mounts installed on the 2 CRS today. This is as far as we can go until we can get flexures or start assembling HOQIs, so probably not much more to report until later next week. We've covered the CRS in foil to protect them, and packed up the left over hardware for these 2 sensors. 

Images attached to this report
LHO General
corey.gray@LIGO.ORG - posted 16:30, Thursday 14 May 2026 (90242)
Thurs DAY Ops Summary

TITLE: 05/14 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY:

Cement truck convoy day for CEBEX today.  Bigger BeamSplitter "captured" in the suspension assy & FARO-ed in the afternoon.  A couple big middle school tours.  ISS Array alignment continued.
LOG:

  • 1438 Kim finishing up with garb supply checks.
  • 1524 technical cleaning in lvea (kim)
  • 1543-1709 Charge Measurements (ryanC)
  • 1547-1554 checking on pumps and overall VAC status (jordan)
  • 1553 Rebar inspector arrived for CEBEX
  • ~1615 LVEA transitioned to SAFE for....
  • ~1615-1813 BBSS work (ibrahim,betsy,oli)
  • 1640:  susr2 rack work near ham3 (josh)
  • 1648:  Cement Truck convoy begins to MY!!
  • ~1650 CP1 checks (travis)
  • 1713-1723 Finley Middle School Tour (amber)
  • 1715-2035 cleaning tests in-chamber....turned ON illuminator in BSC3 (bsc1 & bsc2 is already ON) (robert.tj)
  • 1717-1755 Walkabout in lvea (richard)
  • 1727-1821 technical cleaning in lvea (kim)
  • 1758-1814 Finley Middle School 8th grader tour (maggie)
  • 1815-1833 LVEA Transition back to HAZARD (tony)
  • 1824- 2137 Corner rga (jordan)
  • 1920-1930 checking FARO parts (stephenA)
  • 1942-2324 team-ISS Array starting chamber work (keita)
    • 2002-2248 rahul joining
    • 2015 elenna joining
  • 1943 -2120 team-BBSS back at it (ibrahim, betsy, randy)
  • 1955-2012 Warming up FARO (jason)
  • 2013-2225 CRS work in the CRS Lab (jim.shoshanna.michaelR)
  • 2015-2158 SPI alignment + possible laser hazard (jeff.josh)
    • 2158 jeff out
    • 2224 josh out
  • 2022 Connection alarm for HEPI_PUMPS, not a beckhoff issue, so will need jim to restore (notified Jonathan.patrick/CDS + Jim)
  • 2038-2111 MER to check on HEPI cabling (fil)
  • 2041-2055 connecting with jordan + betsy (travis)
  • 2108-2258 sqzt7 beam profiling, turning sqz laser ON for this work and OFF when done (sheila.ryanS.tony)
  • 2109-2328 team FARO getting set up at Test Stand (jason.ryanC)
  • 2140 turned BSC123+HAM3 illuminators OFF (corey)
  • 2243-2301 Checking out a pelican case (b&k) near HAM6 (tj.jim)
  • 2246-2252 corner rga check (jordan)
  • 2304 Checking on corner station HEPI Pump Station (jim)
  • 2312 More BSC2 cleaning & tests.  Turned BSC123 + H3 illuminators back on (robert w/ Oli-buddy)
H1 SUS
ibrahim.abouelfettouh@LIGO.ORG - posted 15:20, Thursday 14 May 2026 - last comment - 08:43, Monday 18 May 2026(90249)
BBS01 Installed into BBSS

Ibrahim, Betsy, Oli

Today, we installed BBS01 into the BBSS successfully. 

BBS01 was on a table. BBSS was on the aluma lift. We picked BBS01 using the ERGO arm and slowly came into the optic. In this process, we:

  • Removed the EQ stops and replaced them with the glass tips
  • Ensured that the gold wire was held correctly about the lower structure barrell
  • Made contact between the gold wire and the grooves of the prisms
  • Backed the glass tip EQ stops in to contact, securing and locking the whole suspension (M1 and M2 were already locked)
  • Installed the BBSS face shields
  • Practiced a lift of how it would go up into the test stand
  • Placed teflon pads between the lift arms and the BBSS 45 degree lifting bars - LLO did the same (alog 80802) - this helps with fine structure adjustment when below the ISI
  • Covered the BBSS on the lift in prep for test stand install (IAS needs time with the ISI to get exact positions in XY for where BBSS will sit).

On top of pictures below, 2 videos:

Images attached to this report
Comments related to this report
jeffrey.kissel@LIGO.ORG - 08:30, Monday 18 May 2026 (90261)EPO
Link 

Wahoo! Congrats, y'all!
betsy.weaver@LIGO.ORG - 08:43, Monday 18 May 2026 (90262)
Link

Note, current status as of last Thur was handoff to FARO IAS (Jason/Ryan C) who are up for mapping and guiding us into place.  CAD files from CIT arrived Thur so quite literally just in time to get on it.

Also, thanks Travis for all the pictures.

H1 CAL
michael.ross@LIGO.ORG - posted 10:58, Thursday 14 May 2026 (90246)
iNCal Low Speed Accelerometer Tests

I spun the iNCal (currently installed version) at a low speeds to see if low speed operation shows the same vibrations that high speed operation does (see 67207). Even rotating at 1 Hz shows a large increase in signal in the accelerometer (H1:PEM-EX_ACC_BSC9_ETMX_Z) around 200 Hz. 7 Hz shows an order of magnitude increase between 100-300 Hz. The 0 Hz spectrum is with the iNCal powered but a set speed of 0 Hz. 

The lesson is that the iNCal will inject broad band noise in the strain readout even at very low speed operation.

Non-image files attached to this report
H1 SUS (SUS)
ryan.crouch@LIGO.ORG - posted 10:42, Thursday 14 May 2026 (90245)
OPLEV charge measurements, ETMX, ETMY

I ran the oplev charge measurements this morning for both of the ETMs, previously checked in alog89906.

ETMY's charge remains largely unchanged, the values across the quadrants remain below 100 on all quadrants/DOF and I don't see any appreciable trends. As a reminder we switched off the HV digitally for EY.

ETMX's charge is decreasing across all quadrants/DOF after the sign flip we inposed back in April. Over the past 4 weeks the average decrease for P was ~ -14 [V], and ~ -18.25 [V] for Y. UL saw the greatest decrease, a drop of over 30 [V] for both P & Y, UR saw the smallest decrease, around ~ 5 [V] for both P & Y. The charge is now at or below 50 [V] on all quadrants/DOF except UR_P and LR_P.

Images attached to this report
LHO General
corey.gray@LIGO.ORG - posted 07:34, Thursday 14 May 2026 (90241)
Thurs DAY Ops Transition

TITLE: 05/14 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: 5mph Gusts, 3mph 3min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.23 μm/s 
QUICK SUMMARY:

New ISS Array alignment will continue as well as work with the new Bigger BeamSplitter. 

No alarms overnight. Clearer & calmer weather this morning.

With the better weather, perhaps the DGR subcontractors will start pouring concrete for the CEBEX walls today (this will require the main gate to be left open for the cement trucks to roll through.  (WP# 13250)

H1 IOO (INS, IOO, ISC)
keita.kawabe@LIGO.ORG - posted 23:19, Wednesday 13 May 2026 - last comment - 11:50, Thursday 14 May 2026(90237)
Swapped the ISS array. Alignment into the new unit started. (Rahul, Elenna, Keita)

Following yesterday's alog 90219:

  • IM2 and IM3 were reverted back to Monday evening position just using the slider values.
  • Using flashes, confirmed that the IM4 trans as well as ISS QPD were roughly at the same position as the Monday evening position.
  • Elenna confirmed that ISS OUTER SUM flash peak minus dark offset was 0.031 with 200mW input. (INNER SUM was much smaller.) Back in March it was 0.062 with 2 W input. So somehow the alignment into ISS array used to be REALLY poor.

At this point I and Rahul checked the beam positions in HAM2. Some things to note:

  • The beam was uncomfortably close to the holes in the last baffle before the ISS array. It might have been clipped back in March. See ISS_two_hole_baffle.png showing the flash on the right hole. That hole is the "exit" hole for the reflection of the last pico mirror. Left hole is for the incoming beam from the 1" lens (which is right behind the baffle in the picture) but we couldn't take a good photo of the flash in the left hole at the time.
  • Once the beam clears the last baffle, the beam is not clipped by the array cover nor the input hole of the array elevator plate.
  • IM4 trans beam goes to the first pico mirror cleanly without getting clipped, and it's not clipped at all on the 2" lens.
  • IMC trans beam from MC3 hit the IM1 cleanly, clears the baffle after that (IMC_REFL_peri.jpg), and appeared to go to IM2 without getting clipped. Couldn't check IM2->IFI->IM3 but no reason to get suspicious either. 
  • IM1 transmission was clearly visible using a card and the IR viewer, it was not clipped by the suspension cage with considerable marging and was hitting the steering mirror behind IM1. 
  • IMC REFL comes out of the last (second) IMC REFL periscope cleanly, the beam is well centered on the baffle hole. See IMC_trans_after_IM1.mp4.

We proceeded to swap the ISS array unit.

  • Rahul went inside HAM2 and disconnected the QPD and array PDs after powering down the transimpedance amplifiers. Note that ISS QPD TIA shares the chassis with the IM4 trans, so IM4 trans went dark for some time too. 
  • The old array assy was separated from the ISS array spacer. The latter remained in the chamber, only the top assy was swapped, as was explained in alog 90158.
  • The new array assy SN1202965 (S1202965) was put on top of the array spacer. We took time to double check that the bias voltage for QPD comes to the expected pin on the QPD connector before making connection because the connector could be rotated by 90, 180, or 270 degrees and we can ruin some quadrants. Array PD cables were straightforward, it went as planned in alog 90158.
  • TIAs were turned on.

At this point we saw flashes on QPDs as well as array PDs right away. INNER as well as OUTER SUM flashes were both about 0.06 (in the old unit it was 0.03 for OUTER but INNER was much smaller).

We started trying to center the QPD using the first pico mirror. Since pico driver is temporary unavailable (IOT2L is moved away) Rahul turned the pico manually while Elena looked at the laptop screen to monitor flashes in the individual segments. We managed an OK job (arrayqpd_centered.jpg) and checked the beam spots again.

The baffle height might not be the same as the lens height and/or the ISS array input hole height, but otherwise it seems that we're shooting down the beam from the 1" lens to the ISS array. We'll check if the lens, baffle and the array are all at the same height or not, and decide how to proceed.

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keita.kawabe@LIGO.ORG - 23:40, Wednesday 13 May 2026 (90239)
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1st: Rahul is disconnecting the QPD cable.

2nd, 3rd (photo by Betsy): Rahul in chamber (me outside).

4th: Old unit was extracted. This is S1202971.

5th: New unit (S1202965) to the left, old one to the right.

6th: Rahul after successfully connecting up the new unit in chamber.

7th (photo by Betsy): Elenna (front) is checking the QPD centering, Rahul (a shadow in the back in this photo) is manually moving the pico mirror from -Y door, and I'm somewhere inbetween just observing the two doing a good job.

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corey.gray@LIGO.ORG - 08:45, Thursday 14 May 2026 (90243)EPO
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epo tagging for photos!

rahul.kumar@LIGO.ORG - 09:39, Thursday 14 May 2026 (90244)
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Attaching two pictures in reference to Keita's comment above - "The beam was very high on the left hole of the two-hole baffle (Rahul has a good pic), high on the right hole (right_hole_after_new_array_QPD_centered.mp4)"

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keita.kawabe@LIGO.ORG - 11:50, Thursday 14 May 2026 (90248)
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We concluded that the height of the baffle and the array unit are both correct, the beam is really too high on the 1" lens and we're shooting down from there to the QPD. (This should have been the case for a long time with the old unit. Right after the new unit was installed the beam was on QPD and the beam stayed on the QPD, the diameter of the QPD is 3mm, i.e. we haven't made any huge change on the height of the beam at the left baffle hole.)

  • Rahul found in solidworks that the design beam height for LHO is 6.132"=155.75mm.
  • Looking at the pictures we took in the chamber, the center height of the two-hole baffle is about 156mm so that's fine.
  • The height of the spacer we have, which is supposed to be D1101074 specifically made for LHO,  has 4.94"~125.5mm nominal height and our measurement shows somewhat larger than 125.5mm, excellent agreement. We didn't measure the thickness of the thin part of the array base plate (https://dcc.ligo.org/LIGO-D1300323, detailed dimensions are only available in solidworks) nor the distance from the bottom to the beam center of the elevator plate D1400140 (again only available in solidoworks) but Rahul's number makes sense, the height of the actual array unit seems to be according to the design.

With this information, what we'll do next is to gradually bring down the height of the beam on the left baffle hole using the first pico mirror, and use the second pico mirror to bring the beam back on the QPD, until the beam line into the array becomes level-ish with the ISI surface. It doesn't have to be perfect but we don't want to be this much tilted.

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LHO VE (VE)
gerardo.moreno@LIGO.ORG - posted 08:34, Thursday 07 May 2026 - last comment - 19:17, Thursday 28 May 2026(90152)
CP1 Soft Regeneration Update

(Jordan V., Dave B., Gerardo M.)

The internal pressure to CP1 turned around overnight signaling that the process of emptying the trap is complete, now we'll continue to monitor and pump on the cryotrap volume.until good pressure is achieved.

A side note, I manually turned off the CC for PT114B last night at 9:44 pm (local time) as the pressure was rising a bit high, then turned it back on this morning at 5:33 am local time.

Attached is a snapshot of one day trend data of pressure behavior regarding the soft regeneration for CP1.

Process started here.

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gerardo.moreno@LIGO.ORG - 00:44, Wednesday 13 May 2026 (90220)VE
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(Jordan, Travis, Gerardo)

CP1 soft regeneration update, CP1 pumpdown continues, system is currently pumped down by the SS500 cart, one turbo pump and one scroll pump.  Yesterday we visited the sensing line and we injected high purity nitrogen gas, we removed the lower sensing line near the Rosemount sensor to be able to inject the nitrogen gas, no issue introducing the gas, lower sensing line appears clear.

To be done, leak check CP1.

Attached is a plot of the pressure internal to CP1, the plot is for the total ongoing soft regeneration.

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gerardo.moreno@LIGO.ORG - 04:03, Thursday 14 May 2026 (90240)VE
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(Jordan, Gerardo)

We leak checked CP1, specifically the bi-braze joints, we introduced He to both sensing lines (we disconnected the lines before the 3 way valve -X marks the spot - , this is less disruption to the shape of the metal tubing lines), we started with the bottom or low sensing line, we introduced 1 psi of flow into the line for about 35 seconds, no signal was detected by the leak detector attached to the exhaust of the turbo pump.  We did the same test with the high sensing line, no signal was detected.  Since we had the setup on hand we also decided to spray all the bellows, given that now they are free of ice, sprayed helium for about 35+ seconds, no signal was detected by the leak detector at any of the points sprayed.

During all the tests performed the He background at the leak detector was 1.0X10-10 Torr*L/Sec.

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gerardo.moreno@LIGO.ORG - 19:17, Thursday 28 May 2026 (90376)VE
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CP1 pumpdown continues, no issues to report.  However, we had the aux-cart connected to the GV5 annulus trip, but we don't know how it happened, we noted only one tiny slithery critter around the area.

Attached is a plot of the total pumpdown.

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