aLIGO LHO Logbook

LHO General - Ops Day Shift Summary

ryan.short@ligo.org — Fri, 15 May 2026 16:38:57 -0700

Author: ryan.short@ligo.org

Report ID: 90255

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 - Comment to SPI Pathfinder ISIK Transceiver Status

jeffrey.kissel@ligo.org — Fri, 15 May 2026 16:28:04 -0700

Author: jeffrey.kissel@ligo.org

Report ID: 90254

Josh and I hard at work doing helicoil science. Photo credit: Ryan Short.EPO, SPI

Images attached to this report

H1 SPI - SPI Pathfinder ISIK Transceiver Status

jeffrey.kissel@ligo.org — Fri, 15 May 2026 16:27:15 -0700

Author: jeffrey.kissel@ligo.org

Report ID: 90253

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

LHO General - Ops Day Shift Start

ryan.short@ligo.org — Fri, 15 May 2026 07:42:22 -0700

Author: ryan.short@ligo.org

Report ID: 90252

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 - Done with ISS array alignment, not yet ready to go laser safe due to IFO alignment mystery (Rahul, Elenna, Keita)

keita.kawabe@ligo.org — Thu, 14 May 2026 17:41:26 -0700

Author: keita.kawabe@ligo.org

Report ID: 90251

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.

INS, IOO, ISC, PSL

H1 SEI - CRS progress for the week

jim.warner@ligo.org — Thu, 14 May 2026 17:04:25 -0700

Author: jim.warner@ligo.org

Report ID: 90250

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 - Thurs DAY Ops Summary

corey.gray@ligo.org — Thu, 14 May 2026 16:30:12 -0700

Author: corey.gray@ligo.org

Report ID: 90242

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 - BBS01 Installed into BBSS

ibrahim.abouelfettouh@ligo.org — Thu, 14 May 2026 15:20:38 -0700

Author: ibrahim.abouelfettouh@ligo.org

Report ID: 90249

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

H1 IOO - Comment to Swapped the ISS array. Alignment into the new unit started. (Rahul, Elenna, Keita)

keita.kawabe@ligo.org — Thu, 14 May 2026 11:50:54 -0700

Author: keita.kawabe@ligo.org

Report ID: 90248

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.

Images attached to this report

H1 CAL - iNCal Low Speed Accelerometer Tests

michael.ross@ligo.org — Thu, 14 May 2026 10:58:46 -0700

Author: michael.ross@ligo.org

Report ID: 90246

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

NCal_Accel_SpeedTest_rotated.pdf

H1 SUS - OPLEV charge measurements, ETMX, ETMY

ryan.crouch@ligo.org — Thu, 14 May 2026 10:42:38 -0700

Author: ryan.crouch@ligo.org

Report ID: 90245

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.

SUS

Images attached to this report

H1 IOO - Comment to Swapped the ISS array. Alignment into the new unit started. (Rahul, Elenna, Keita)

rahul.kumar@ligo.org — Thu, 14 May 2026 09:39:07 -0700

Author: rahul.kumar@ligo.org

Report ID: 90244

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)"

Images attached to this report

H1 IOO - Comment to Swapped the ISS array. Alignment into the new unit started. (Rahul, Elenna, Keita)

corey.gray@ligo.org — Thu, 14 May 2026 08:45:48 -0700

Author: corey.gray@ligo.org

Report ID: 90243

epo tagging for photos!

EPO

LHO General - Thurs DAY Ops Transition

corey.gray@ligo.org — Thu, 14 May 2026 07:34:28 -0700

Author: corey.gray@ligo.org

Report ID: 90241

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)

LHO VE - Comment to CP1 Soft Regeneration Update

gerardo.moreno@ligo.org — Thu, 14 May 2026 04:03:23 -0700

Author: gerardo.moreno@ligo.org

Report ID: 90240

(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.

Images attached to this report

H1 IOO - Comment to Swapped the ISS array. Alignment into the new unit started. (Rahul, Elenna, Keita)

keita.kawabe@ligo.org — Wed, 13 May 2026 23:40:27 -0700

Author: keita.kawabe@ligo.org

Report ID: 90239

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.

Images attached to this report

H1 IOO - Swapped the ISS array. Alignment into the new unit started. (Rahul, Elenna, Keita)

keita.kawabe@ligo.org — Wed, 13 May 2026 23:19:35 -0700

Author: keita.kawabe@ligo.org

Report ID: 90237

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 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), and OK on the input hold of the array (array_input_after_new_array_QPD_centered.mp4).

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.

INS, IOO, ISC

Images attached to this report

Non-image files attached to this report

IMC_trans_after_IM1.mp4

right_hole_after_new_array_QPD_centered.mp4

array_input_after_new_array_QPD_centered.mp4

H1 SEI - CRS progress today

jim.warner@ligo.org — Wed, 13 May 2026 18:38:34 -0700

Author: jim.warner@ligo.org

Report ID: 90238

Shoshana, Michael, Jim

Today we went into the PSL and started putting together the 2 complete CRS assemblies we have cleaned and ready to go. This went pretty smoothly and we now have to mostly done CRS, sans HOQI readout. We don't have flexures we can use, so we can't suspend or do any mechanical tuning, but proof masses are installed in the frames, mass adjustment hardware and picos are mounted. Tomorrow, we will probably look at what prep we can do on the other 2 CRS, but fasteners are still working through c&b for those, so I don't know there is much to do until those come out.

Images attached to this report

H1 SUS - BBSS Taken out of Can and Prepped for Install

ibrahim.abouelfettouh@ligo.org — Wed, 13 May 2026 16:36:41 -0700

Author: ibrahim.abouelfettouh@ligo.org

Report ID: 90236

Ibrahim, Betsy, Randy

Today, we:

Took the BBSS out of the can after securing the BSFM.
Prepped the BBSS
- blew the suspension with nitrogen top gun from top down
- took the lifting plates out and set it down on its assembly tooling
- attached the 45 degree lifting arms
Prepped the ERGO arm
- 2 adjustment O-rings had to be re-installed
- BBS plate was used to lift practice glass
- Dry run of where it would go with the optic was done
Prepped the Aluma-Lift
- cleaned the lift arms
- positioned and dry-ran the path it would take during install

Particle counts were checked periodically and were under 75 consistently during acitvity

See pictures.

EPO, SUS

Images attached to this report

LHO General - Wed DAY Ops Summary

corey.gray@ligo.org — Wed, 13 May 2026 16:30:53 -0700

Author: corey.gray@ligo.org

Report ID: 90222

TITLE: 05/13 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY:

ISS PD Array and BBSS work continues. Had a couple of big school field trip visits.

Odd weather day with fairly high winds and rain for most of the day.
LOG:

1534-1717 technical cleaning (optics lab and then LVEA + set-up at the old H2 PSL enclosure for upcoming work to be done inside it) [kim]
1545-1805 SQZT7 taking panels off (sheila)
- 1556-1657 tony joining
1554-1746 BBSS work working on connecting the Bigger Beamspliter to the suspension frame in the coming days (ibrahim)
- 1601- betsy joining
- 1643 oli joining
- 1700 randy joining
1611- 1613 Opening PSL Light pipe for ISS pd array & returning to control room to look at alignment (keita)
1627-1634 HAM6 ramp down rga bakeout & then move to CP1 to begin leak checking (jordan)
1708- ~2000 CRS (Cyllindrical Rotation Sensor) work at h2psl (jim,michaelR,shoshana)
1713-1935 ISS PD Array (keita,rahul)
1732-1815 EX ground studies continue (robert)
1736-1850 technical cleaning @EX (kim)
1751 SUSR2 rackwork for SPI (josh)
1800-1918 BBSS team returns for test stand to continue move to install the Bbs (betsy.randy.ibrahim)
~1730-1838 TCS plumbing work (tj,madi)
1830-1845 Outlook Elementary School tour (Amber)
1915-1930 Outlook Elementary School tour (Cassidy)
2018- 2149 TCS plumbing work cont.; will leave the chiller ON overnight. (tj,madi)
2039-2252 BBSS team returns to Test Stand (ibrahim, betsy, randy)
- 2216 randy out
2042 HAM6 RGA (jordan)
2046-2230 SPI build + possible laser hazard in the optics lab (Jeff)
2049 CRS work at h2psl (jim,michaelR,shoshana)
2049-2155 electronics work for CRS near h2psl (richard,fil)
2055-2116 Escorted rebar inspector to CEBEX site & made lunch (corey)
2100 ISS PD Array alignment cont (keita.rahul)
- 2229 Elenna joining for picomotor help
- 2329 Rahul out
2206 restarting bake of RGA at HAM6 and another quick check at 2330 (jordan)
2238-2255 Closing TCSy table (was letting it dry out) [tj]

H1 COC - BBS01: First Contact on HR Side (and flipping BBS post-gluing)

ibrahim.abouelfettouh@ligo.org — Wed, 13 May 2026 16:29:22 -0700

Author: ibrahim.abouelfettouh@ligo.org

Report ID: 90235

Ibrahim, Betsy, Oli

BBS01 AOSEM flag standoffs were removed, concluding gluing.

BBS01 was flipped to the HR Side via the inspection fixture.

Betsy and I then first contacted the HR Side (S1) and peeled an hour or so later.

We did not see any features or defects as we did with S2.

EPO

Images attached to this report

H1 TCS - TCSY table chiller lines all replaced and tested

thomas.shaffer@ligo.org — Wed, 13 May 2026 16:00:26 -0700

Author: thomas.shaffer@ligo.org

Report ID: 90234

Camilla C, Madi S., TJ S

Just as we did with the TCSX table a few weeks ago (alog90078), we swapped all of the flex lines on the table. Most of this was done last week, but today Madi and I fisnished the last two lines today. We then used the same vacuum trick to suck water into the table lines to "test" the lines over lunch, and then plugged the table back into the full system and slowly turned on the chiller. We had one leak at the laser driver, but cutting and reseating the 1/8"OD tube seemed to fix it.

While trying to removed the old 3/4"OD return tube from the tee, I managed to bump the iris next to the bottom periscope mirror. We'll have to recheck this when we have beam again and can some HWS tests.

The chiller is running, I'll check on things in the morning.

Images attached to this report

H1 SEI - H1 ISI CPS Noise Spectra Check - Weekly

anthony.sanchez@ligo.org — Wed, 13 May 2026 15:51:44 -0700

Author: anthony.sanchez@ligo.org

Report ID: 90233

H1 ISI CPS Sensor Noise Spectra Check - Weekly FAMIS 39336

For some context, most of the Corner station is vented and the BS cartridge is not in the chamber which explains what is shown on the BS plots here..

Non-image files attached to this report

CPS_spectra_15:19-05_13_2026.pdf

H1 IOO - Comment to ISS work restarts

elenna.capote@ligo.org — Wed, 13 May 2026 13:46:22 -0700

Author: elenna.capote@ligo.org

Report ID: 90232

On March 11 when we locked the IMC at 2 W, the outersum was 0.062. Today, I measured the outersum flashes (relative to the dark noise) to be 0.031, with 0.18 W input. This means our alignment into the ISS has improved relative to March.

H1 SPI - SPI Pathfinder, RF Install Pt 1, ISIK 80MHz

joshua.freed@ligo.org — Wed, 13 May 2026 12:38:24 -0700

Author: joshua.freed@ligo.org

Report ID: 90231

J Freed, M Pirello,

We continued the progress to install the SPI RF chain as well as measured the 80MHz RF power along key points along the chain.

SPI_RACK_LAYOUT_SUS-R2.png Shows the schematic of the rack layout for SPI in HAM 3 as well as measured power along that chain. We currently have the entire chain installed to just before the 2W amp. The main thing of note is that we have more power than even our most optimistic estimate. (We were expecting about 5dBm, MAX 8dBm, but we have 9.5dBm). The Heliax cables are much more efficient than we expected. As such next on the list is to install attenuators such that we get the power we expect.

IMG_0627.jpg Shows the current Balun/Spitter set up. There is not really a good place to put the splitter on the SUS-R2 rack as the Patch Panel "walls" prevent using zip-ties or velcro to attach the Splitter on the sides of the SUS-R2 rack. Above the patch panel is the top of the rack; and below cables are in the way. As such, the least intrusive way is to attach the splitter to the balun (The transformer that converts the balanced Heliax cable to the unbalanced coax N-type cable), and add some strain relief on it. Not sure how effective this strain relief is but its better than nothing.

Marc also set up the 18V and 24V DC that powers the Double Mixer and other chassis that will eventually be installed.

Next steps:

1. Add attenuators such that the power going into the 2W amp would be correct.

2. Do phase noise measurements on the output power of the Double Mixer and see if anything has changed since 90179

3. Test if instead of Attenuators we can attenuate the power output of the double mixer by adjusting the input voltage of the 4096Hz signal from the CDS that goes to the Double Mixer

Images attached to this report

H1 SPI - Comment to First In-vac Components for SPI Pathfinder Installed!! ISI HAM2 (ISIJ) Reflector Assembly Installed and Cabled up to Feedthrus

jeffrey.kissel@ligo.org — Wed, 13 May 2026 11:22:27 -0700

Author: jeffrey.kissel@ligo.org

Report ID: 90230

Belated aLOG on in-vac cable routing of the ISIJ QPD A PD and serial number assignments: Path PD Name PD SN Monopus D9-to-D25 Monopus |----------D2600002--------| D1600083 Type 3 D2400340 D2300128 OL ISIJ QPD A S2401092 S2500517 S2500511

Images attached to this report

H1 SPI - SPI Pathfinder ISIK Transceiver In-vac PD cable routing vs. PD / Cable Serial Numbers

jeffrey.kissel@ligo.org — Wed, 13 May 2026 11:20:16 -0700

Author: jeffrey.kissel@ligo.org

Report ID: 90228

J. Kissel SPI Wiring Diagram: D2400111-v6 In-chamber in-vac cable routing: In-vac Cable Routing Plan from G2401479-v3 I never aLOGged our choice of cable-table bracket floor assignment down when we originally assembled and signal-checked the D2400107-v4, so during disassembly in prep for upgrade to D2400107-v5 (LHO:90225) I took the time to write down the cable routing, cable serial number assignment, and cable table bracket (CBT) floor assignment: Path PD Name PD SN Duopus D9 CBT Name / Floor Quadrapus D25 CBT Name / Floor |----------D2600001--------| D1600083 Type 2 D2400341 D2000492 D2400343 D2000492 S2500512 IFO REF A/B S2401096/S2401095 S2500516 CBT 2 / 2nd of 2 cable E CBT 1 / 1st of 2 IFO MEAS A/B S2401097/S2401098 S2500514 CBT 2 / 1st of 2 cable D CBT 1 / 1st of 2 FBR PWR REF/MEAS S2401094/S2401093 S2500515 CBT 3 / 2nd of 2 cable C CBT 1 / 1st of 2 PD SN Monopus |----------D2600002--------| D1600083 Type 3 D2400340 OL ISIK QPD B S2401091 S2500518 CBT 3 / 1st of 2 cable B CBT 1 / 1st of 2 First and Second of the attached pictures are of the CBT 2 cable routing. I needed two pictures because the D9 end's two-part backshell of IFO REF cable was assembled with its serial number stamped on one side of one part, and the other side of the other part. C'est la vie. Third picture is of CBT 3's cable routing. The 2x D9 CBT assemblies (since the "type" we've assembled is not explicitly drawn in D2000492) are - QTY 1x D2000519 baseplate - QTY 1x D2000520 "Type 2" two-floor uprights, with - QTY 2x D2200443 D9 adapters, - QTY 2x 1/4"-20 x 0.625" L captive SHCS (95966A512) for securing to the HAM table (rather than the 3/8"-16 captive SHCS that are used to secure to the BSC tables) - QTY 2x #6-32 x 0.375"L SHCS (92200A146) for securing the baseplate to the upright - QTY 2x per D9 adapter (4x total) #4-40 x 0.224"L ("2D"; 1185-04EN224) nitronic 60 helicoils for each of the upright holes - QTY 2x per D9 adapter (4x total) #4-40 x 0.5"L captive SHCS (95966A140) for securing the adapters to the upright For the single D25 2-floor CBT that holds the D25 ends of the PD and picomotor quadrapuses, we used the standard D2000492 Type 2 configuration.

Images attached to this report

H1 AOS - Comment to SPI Pathfinder ISIK Transceiver In-vac PD cable routing vs. PD / Cable Serial Numbers

jeffrey.kissel@ligo.org — Wed, 13 May 2026 11:02:24 -0700

Author: jeffrey.kissel@ligo.org

Report ID: 90229

Pictures of the D1600083 Generic PD enclosure ends of the D2600001 Assemblies In order of their appearance in D2400111-v6 page 3: - IFO_REFA - IFO_REFB - IFO_MEASA - IFO_MEASB - FBRPWRIN_REF - FBRPWRIN_MEAS - QPD_B

Images attached to this report

H1 IOO - ISS work restarts

keita.kawabe@ligo.org — Wed, 13 May 2026 10:07:40 -0700

Author: keita.kawabe@ligo.org

Report ID: 90226

Restored the alignment sliders for IM2 and IM3 back to Monday values ([IM2P, Y] =[765, -187.7], [IM3P, Y]=[-560.7, 320]).

Measured the flashes. Chose the flash that gave the MC2 trans sum maximum power, which in general agreed with IM4 trans sum max but didn't with ISS QPD nor array PD inner sum nor outer sum.

Anyway,

MC2 trans: SUM=21; seg1=0.0027; seg2=0.0029; seg3=0.0024; seg4=0.0022
- i.e. PIT=0.098, YAW=-0.039
IM4 trans: SUM=0.0276; seg1=0.00876; seg2= 0.00760; seg3=0.00456; seg4=0.00526
- i.e. PIT=0.25, YAW=0.07
ISS QPD: SUM 362; seg1=67; seg2=13; seg3=13; seg4=271
- i.e. PIT= -0.56, YAW=0.86
ISS Inner: SUM 0.023
ISS Outer: SUM 0.104

PIT and YAW numbers were after normalization divided by (seg1+2+3+4), not by SUM, so there's a small difference but that doesn't matter at this point.

IM4 TRANS and ISS QPD PIT and YAW are broadly in agreement with Jenne's alog 90206 i.e.

IM4 Trans Pit 0.2 Yaw 0.05 (Monday)
ISS QPD Pit -0.53 YAW 0.85 (Monday)

I haven't compared the ISS Outer SUM with March 2026 when IMC was locked with 2W. Somebody check please. We'll go into chamber and start checking the beam path.

INS, IOO, ISC

H1 SPI - SPI Pathfinder D2400107-v4 Decommissioned, Moved Aside, and Prepped for Upgrade to -v5

jeffrey.kissel@ligo.org — Wed, 13 May 2026 09:17:57 -0700

Author: jeffrey.kissel@ligo.org

Report ID: 90225

J. Kissel E2600106 / IIET:37433 D2400107-v4 I've decommissioned the SPI pathfinder's ISIK Transceiver as it stands now (D2400107-v4) by - disconnecting all electronics cabling; PDs at the cable-table bracket and picomotors' quadrupus at each pico-actuated optic - disconnecting optic fibers - untangling the in-vac cabling and fibers, ensuring the - installing installation handles (LHO:90223) - setting up a new set of 1"D x 6"L class-B posts then - removed the 3x temporary class-B bolts and washers that had secured the breadboard to the posts - lifting and transferring the D2400107-v4 assembly over to the other position and - securing there with the 3x temporary class B bolts. Pictures of the move attached. SEI

Images attached to this report

H1 IOO - Comment to ISS path alignment: Not much progress on Tuesday due to distraction/confusion (Elenna, JennieW, Keita)

keita.kawabe@ligo.org — Wed, 13 May 2026 09:10:09 -0700

Author: keita.kawabe@ligo.org

Report ID: 90224

One of the things that bothered me (that isn't directly related to ISS alignment) is the fact that we had to rotate JM3 by a huge amount, i.e. negative 200um in PIT to "center" the MC2 trans QPD. This is the equivalent of the negative YAW rotation of the beam in IMC's coordinates (clockwise seen from the top). Since the distance between MC2 and JM3 is ~19m according to E2400218, this means that the MC2 beam position was moved by about ~7.6mm in -Y direction on MC2. This seems to roughly corroborate with the pictures in alog 90203 ("before" picture and "after", hard to tell how much it actually moved due to parallax but there's no doubt that the motion was large).

What if this is because something is wrong with the MC2 trans path? Like the pico mirror in front of the QPD was bumped (by a huge amount, however unlikely it is). My conclusion is that we can lock IMC in vacuum, use WFS with MC2 centering, measure the centering on MC2 using dither, and figure it out. If QPD center is grossly off from the MC2 center, we can pico.

H1 SPI - SPI Installation Handles Fit Check

jeffrey.kissel@ligo.org — Wed, 13 May 2026 09:07:05 -0700

Author: jeffrey.kissel@ligo.org

Report ID: 90223

J. Kissel ISIK Transceiver Assembly D2400107-v5 ISIK Installation Handle Assembly D2500215-v2 In prep for moving the old version of the SPI pathfinder's ISIK transceiver (D2400107-v4) with CVM100 mounts to the side, I assembled and fit-checked the (Class-B) ISIK Installation Handle Assembly D2500215. It fit! The only detail that required clock cycles was understanding which hardware went to which hole, so I made some redlines and posted them to D2500215-v2. Attached are pictures before moving ye ol' 'board. Nice work ANU!

Images attached to this report

LHO General - Wed DAY Ops Transition

corey.gray@ligo.org — Wed, 13 May 2026 07:36:53 -0700

Author: corey.gray@ligo.org

Report ID: 90221

TITLE: 05/13 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: 19mph Gusts, 13mph 3min avg
Primary useism: 0.04 μm/s
Secondary useism: 0.10 μm/s
QUICK SUMMARY:

ISS PD Array + LVEA Laser Hazard will continue. BBSS work continues at the Test Stand.

Rainy & windy morning (just had quick wind storm with gusts reaching almost 50mph just passed...forecast is for a windy day).

H1 IOO - ISS path alignment: Not much progress on Tuesday due to distraction/confusion (Elenna, JennieW, Keita)

keita.kawabe@ligo.org — Wed, 13 May 2026 00:54:39 -0700

Author: keita.kawabe@ligo.org

Report ID: 90219

We started with yesterday's alignment. I checked flashes in ISS array PDs and didn't like that the balances between them were very much different from how they were when IMC was locked back in March.

Then we started changing IM2 and IM3 to see if we can get back, but I was appalled that the flashes became stronger and stronger on array PDs as we aligned, which probably means that the beam was almost falling off of the PDs when we started.

That shouldn't have stopped us because we don't know where the beam was on the array PDs when MC was locked (people gave up optimizing that path because things didn't make sense), it could have been falling off of the diode (because each diode is 2mm, QPD is 3mm, the beam size is ~250um or so, and the beam was almost in one quadrant of the QPD). But I started thinking about many what-ifs and wasted time.

After all, since IM4 TRANS and ISS array QPD are both reasonably close to March 2026 position, we know that the beam position as well as angle of the beam injected into ISS path from IM4 are already close to those when IMC was good in vacuum.

What we should do is this:

Revert back to Monday IM2/IM3 alignment. Confirm that the IM4 trans position as well as ISS array QPD position are OK.
Check flashes in 2nd loop inloop and out-of-loop sum. Recheck if at least one of them is comparable to when IMC was locked back in March, taking into account the power difference, even though Sheila checked it yesterday. At this point, we'll have established again that the position and the angle of the beam coming into the ISS path are reasonable.
Check that the beam in ISS path is nowhere near being clipped by baffles and ISS array cover and the elevator aperture of the ISS array. Don't fix clipping right away, do it after swapping the array because we'll have to move pico mirrors anyway.
Swap the array. There's no assurance that the beam will be on the QPD right away but that's OK. We can move the unit on the spacer if that helps. Go as close as you can, then start using the two pico steering mirrors. Use the array input aperture to aid the process.
Once you see the beam on the QPD, continue to center the QPD, fix clipping, not necessarily in this order.
Check the flash height of array PDs as well as QPD, see if things makes sense.

Other things to note:

This is not required for the alignment but it's helpful to know how much we can move the beam on QPD. In an unlikely event where we somehow lose the beam in vacuum on the array QPD after IMC is locked, we might be able to scan IM3/IM2 to regain the beam on QPD, and slowly move IM3/IM2 back to the nominal position while pico-ing so the beam isn't lost on the QPD. If the beam is not clipped, the beam displacement on the QPD is ~3mm per 1mrad of IM3 rotation using parameters collected from various documents, see attached script.

The same script shows you that the Gouy phase separation between two pico mirrors is 10 degrees (if we use the beam parameter in Matt Heintze's alog 12537, which was probably obtained by the measurement of the bypassed beam) or about 20 degrees (if we use IMC eigenmode parameter propagated to the ISS path using D1200693).

Another thing is, if we believe the design eigenmode number rather than the measured bypassed beam in Matt's alog, the beam waist will be smaller and at about 20cm upstream of the PDs. The beam size on the PDs is about twice as large as it should be (470um rather than 250um). I cannot measure the beamsize of the flashes so we won't do anything, but that's something to remember. If IM3 has enough actuation range, we can later lock the IMC, scan the beam across the PD until the beam falls off, see how sharp the fall-off is, and use the diameter of the PD (3mm) to determine the size of the beam. Maybe a good project for a fellow.

Non-image files attached to this report

ISS_array_path.m

LHO VE - Comment to CP1 Soft Regeneration Update

gerardo.moreno@ligo.org — Wed, 13 May 2026 00:44:31 -0700

Author: gerardo.moreno@ligo.org

Report ID: 90220

(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.

Images attached to this report

H1 SQZ - Comment to looking at SQZ beam profile data from last summer

sheila.dwyer@ligo.org — Tue, 12 May 2026 16:54:24 -0700

Author: sheila.dwyer@ligo.org

Report ID: 90218

Evan and Camille both pointed out that I made an error with the signs in estimating the ROC of the psams after the pre-load change.

ZM4 has a negative ROC, adding pre-load to ZM4 should make it more curved, having a more negative optical power or a smaller negative ROC. For ZM4 with 0V on PZT, -106 - 2.4*29 = -175.6 mD, or ROC of -11.4 meters. DpV on the strain gage should be a negative number.

ZM5 has a positive ROC, adding more preload should make it less curved, so smaller positive optical power, larger positive ROC. ZM5 before preload change was 667mD, after preload change it should be 667 -2.4*27 = 602mD, or ROC 3.32 meters. DpV on the strain gage should still be a negative number.

Correcting this in the script changes the plot of the overlaps slightly, new version is attached.

ZM4 nominal O4 ROC -9.2m, actuation -0.36mD/Vpzt
ZM5 nominal O4 ROC 3.7m, actuation -0.47 mD/Vpzt

Images attached to this report

H1 SEI - Prep for CRS assembly in H2 PSL anteroom

jim.warner@ligo.org — Tue, 12 May 2026 16:43:27 -0700

Author: jim.warner@ligo.org

Report ID: 90217

Shoshana, MichaelR, Jim

This morning we started moving parts into the lvea to start doing CRS assembly in the H2 PSL enclosure. We should have parts for 2 complete sensors right now (minus HOQIs), and should be getting the remaining parts out of clean and bake soon. We spent a lot of time trying to debug the H2 fans and hvac, but it seems not everything is fully functional yet. HEPA units are running in the anteroom however, which should be enough for us to keep parts clean while we assemble. I put a dust monitor in on a table and took counts, they stayed the in 50-100 range while I was watching. Parts are set on one of the stainless shelving units, we can use the stainless table in the anteroom for assembly for now.

Images attached to this report

LHO General - Ops Day Shift End

thomas.shaffer@ligo.org — Tue, 12 May 2026 16:30:34 -0700

Author: thomas.shaffer@ligo.org

Report ID: 90209

TITLE: 05/12 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
SHIFT SUMMARY: The BS suspension was removed from the ISI that it hung from today. The LVEA continues to be in laser hazard for the ISS swap work, which will continue on for another day or so. Alignment trends attached, no surprises with the ongoing ISS work.

Operators - It looks like the LVEA temperature has been trending up over the last week (see screenshot). We should keep an eye on this to verify that it comes back.

LOG:

Start Time	System	Name	Location	Lazer_Haz	Task	Time End
19:43	SAF	LVEA IS LASER HAZARD	LVEA	Y	LVEA IS LASER HAZARD	12:03
15:14	FAC	Kim	LVEA	yes	Tech clean	17:05
15:17	IAS	Ryan C	LVEA	yes	Warm up Faro	15:33
15:20	FAC	Randy	LVEA	yes	Setting up lights at test stand	15:58
16:05	FAC	Randy	LVEA	yes	Prep and setup	16:36
16:20	SUS	Betsy, Rahul	LVEA	yes	BBS bonding and sus prep	18:46
16:27	SAF	Keita	LVEA	YES	Opening light pipe	16:44
16:31	FAC	Chris	MY	n	Bringing battery charger	17:31
17:01	SUS	Ibrahim	LVEA	yes	BBS work	18:56
17:03	SUS	Randy	LVEA	yes	Assist with BBS	18:38
17:17	PEM	Robert	EX	n	Magnetic coupling investigation	19:31
17:31	SEI	Jim, Michael, Shoshana	LVEA	yes	Moving CRS into the H2 PSL enclosure	19:03
17:34	IAS	Jason, Ryan C, Stephen	LVEA	yes	Monument search and error hunt	19:56
17:54	FAC	Kim	LVEA	yes	Tech clean	18:48
19:32	SPI	Jeff	Opt Lab	n	SPI assembly	21:56
19:33	SUS	Ibrahim	LVEA	yes	BBS work	22:03
19:43	SUS	Randy	LVEA	yes	BBS work	22:03
19:46	SUS	Betsy	LVEA	yes	BBS work	22:03
19:57	CDS	Marc, Josh	LVEA	yes	SUS R2 rack testing out SPI electronics	21:42
20:27	SUS	Rahul	LVEA	yes	BBS work	20:35
20:28	SUS	Travis	LVEA	yes	Bringing out hardware	20:33
20:50	FAC	Tyler	LVEA	yes	Inspect scaffolding	21:05
21:02	NCAL	Tony, Michael, Shoshana	EX	n	Spin up NCAL	22:13
21:05	SEI	Mitchell	ends	n	HEPI FAMIS checks	21:46
21:22	PEM	Robert	EX	n	Magnetic coupling invesitgation cont.	23:23
22:28	SEI	Jim, Michael, Shoshana	LVEA	y	H2 anteroom CRS build (M & S out @2300)	23:07

OpsInfo

Images attached to this report

H1 CDS - FMCS Well Pump Monitor EPICS IOC

david.barker@ligo.org — Tue, 12 May 2026 15:55:56 -0700

Author: david.barker@ligo.org

Report ID: 90216

Jonathan, Erik, Dave:

The EY well pump is now being monitored by an EPICS IOC which will report if the pump runs long outside of business hours. The well pump status is available on a MEDM, which can be launched from the FMCS overview MEDM (see attached). If the pump runs for more than 2 hours outside of standard hours (07:00 - 17:00 Mon-Fri) an alarm will be raised.

Images attached to this report

H1 SUS - BSFM lifted off of test stand/ISI

ibrahim.abouelfettouh@ligo.org — Tue, 12 May 2026 15:14:57 -0700

Author: ibrahim.abouelfettouh@ligo.org

Report ID: 90214

Ibrahim, Randy, Betsy, Rahul

Today, we:

Prepared the BSFM for test stand removal which involved taking off some wire baffles, loosening dog clamps and wiping down the BSFM platform (LSAT).
Set a perimeter for BBSS to go up (in same position) using dog clamps.
Installed and fit-check the 45 deg. lifting bars - the screws seemed to be too long so we used 2 nuts to back them out.
Brought the aluma lift in to pick up the suspension and lifted it out of the test stand smoothly.
Rested it in the cleanroom on the LSAT with some dunnage blocks.

See pictures

Images attached to this report

H1 SUS - Comment to ZM4 (P-SAMS in HAM7) preload adjusted to change the radius of curvature of the mirror

sheila.dwyer@ligo.org — Tue, 12 May 2026 14:55:35 -0700

Author: sheila.dwyer@ligo.org

Report ID: 90213

Evan and Camille noticed that I flipped a sign here:

The preloading should make the magnitude of the optical power larger, so it should be increased to -106mD - 2.4mD/in lb * 29 in lbs = -175.6 mD with 0 V on the PZT. ROC = 1/-175.6e-3 = -11.4 meters

H1 SPI - Comment to First In-vac Components for SPI Pathfinder Installed!! ISI HAM2 (ISIJ) Reflector Assembly Installed and Cabled up to Feedthrus

jeffrey.kissel@ligo.org — Tue, 12 May 2026 12:08:34 -0700

Author: jeffrey.kissel@ligo.org

Report ID: 90212

On the new channel assignment of HAM2's SPI ISIJ picomotor, and why I'm confident it's CH7: Per D1000581-v13, page 13 and then D1900511-v12 page 17, I'm quite confident that the quadrupus cable and up in CH5-8 of the controller on IOT2L, called "PICOMOTOR 5" in D1900511, which I guess becomes "Picomotor B / Slot 2" on page 2 of the ECAT System Diagram D1100683-v11. This is corroborated with opening up the picomotor MEDM screen -- sitemap > LSC > picomotors > "HAM 2 + oplev" button (that has "controller 5" and "PICO B" next to it), and clicking through the channels and seeing that CH8 is called "PSL ISS QPD/PD (PM5)." Here's a labeled picture that makes things more clear.

Images attached to this report

H1 SUS - BBSS SUS medm infrastructure filled in

oli.patane@ligo.org — Tue, 12 May 2026 11:01:58 -0700

Author: oli.patane@ligo.org

Report ID: 90154

I've gone through and filled in most of the infrastructure for the BBSS (found under BS/ITM on sitemap as BBSS temp). Values and filter settings have been saved to sdf and filters added have been committed in H1SUSLO12.txt as r35219. For the majority of the filters banks, I turned any filters that are shown as being on in whatever I referenced them from, but all filter banks have INP and/or OUT OFF, so no signal can pass through.

Infrastucture filled in:

All stages
OSEM2EUL / SENSALIGN / EUL2OSEM Matrices
Filled out according to matrices calculated in /ligo/svncommon/SusSVN/sus/trunk/BBSS/Common/MatlabTools/make_susbbss_projections.m. The Y direction matrix elements for M1 OSEM2EUL have been left blank for now

M1
OSEMINF Filter Banks
- _{F1,F2,F3,LF,RT,SD}_{X_RAW,Y_RAW,SUM} have satamp compensation filter of zpk([0.145],[720e-6],1) installed in FM1, called 0.15:7e-4
- _{F1,F2,F3,LF,RT,SD}_{X,Y} have a conversion from counts to um with a gain(250) in FM5, called to_um. This value was found by using the conversion from Tom of 4000 counts / meter, and then converting meters to um.
- Tom said that we will not need any offsets, and the QOSEMs are calibrated so we don't need any special gains in the filter banks, so I've set the filter banks to gains of 1.
WATCHDOG Filters
BANDLIM Filter Banks
- Same filters as in OSEMINF, plus acBandLimiter
RMSLP Filter Banks
- 10 second LP added into FM1
LOCK Filter Banks
- Copied over from BSFM M1 for now
DAMP Filter Banks
- Copied the damping filters from BSFM M1 over for now
COILOUTF Filter Banks
- Copied over from BSFM M1 for now

M2
OSEMINF Filter Banks
- Satamp precise compensation filters inserted into FM1 according to the installed satamp for M2, plus conversion to_um in FM5
- Offsets and gains need to be re-done for BBSS M2
WATCHDOG Filters
BANDLIM Filter Banks
- Same filters as in OSEMINF, plus acBandLimiter
RMSLP Filter Bank
- 10 second LP added into FM1
LOCK Filter Banks
- Copied over from BSFM M2 for now
OLDAMP Filter Banks
- Copied over from BSFM M2 for now
VRDAMP Filter Banks
- Copied over from BSFM M2 for now
COILOUTF Filter Banks
- Copied over from BSFM M2 for now

M3
OSEMINF Filter Banks
- Satamp precise compensation filters inserted into FM1 according to the installed satamp for M3, plus conversion to_um in FM5
- Offsets and gains need to be done for BBSS M3
WATCHDOG Filters
BANDLIM Filter Banks
- Same filters as in OSEMINF, plus acBandLimiter
RMSLP Filter Bank
- 10 second LP added into FM1
OPLEVINF Filter Banks
- Copied over from BSFM M3 for now
LOCK Filter Banks
- Copied over from BSFM M3 for now
COILOUTF Filter Banks
- Copied over from PR3 M3 since they have the same electronics for M3

H1 IOO - Comment to Restoration of IMC alignment continues (Elenna, Sheila, Jenne, Keita)

keita.kawabe@ligo.org — Tue, 12 May 2026 09:19:44 -0700

Author: keita.kawabe@ligo.org

Report ID: 90210

During the work noted above, I disabled IMC-IM4_TRANS whitening OFF (only one stage was on) because the fringe velocity was big-ish and made flash peaks of some quadrants distorted, which means either the whitening/dewhitening mismatch was a problem (likely) or the ADC was railing (unlikely).

Also, I held the output of H1:IMC-IM4_TRANS_SUM (to avoid dividing P and Y by a tiny number, but of course it was useless). NSUM wasn't changed.

Whitening is still OFF but I turned off the holding of H1:IMC-IM4_TRANS_SUM this morning.

I'll turn one stage of IM4_TRANS whitening back ON after we're done with ISS.

LHO General - Ops Day Shift Start

thomas.shaffer@ligo.org — Tue, 12 May 2026 07:35:18 -0700

Author: thomas.shaffer@ligo.org

Report ID: 90208

TITLE: 05/12 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
CURRENT ENVIRONMENT:
SEI_ENV state: MAINTENANCE
Wind: 4mph Gusts, 1mph 3min avg
Primary useism: 0.01 μm/s
Secondary useism: 0.09 μm/s
QUICK SUMMARY: IPC errors on h1susMC2 and h1seiproc, dackill on h1iopseib2. All sus aligned and damped except PR2 which is in safe (looking into this), SEI in state captured by the whiteboard. Temps look good and dust counts look good in the LVEA. More laser hazard work planned for the day in the LVEA.

H1 CDS - Workstations updated

erik.vonreis@ligo.org — Tue, 12 May 2026 05:08:16 -0700

Author: erik.vonreis@ligo.org

Report ID: 90207

Workstations were updated and rebooted. This was an OS packages update. Conda packages were not updated.

H1 IOO - Comment to Restoration of IMC alignment continues (Elenna, Sheila, Jenne, Keita)

jenne.driggers@ligo.org — Mon, 11 May 2026 18:39:08 -0700

Author: jenne.driggers@ligo.org

Report ID: 90206

Once Elenna had the IMC nicely aligned, we moved on to setting the pointing of the beam headed to the IFO. We need this to be roughly correct, so that we can use it to align the ISS array.

Back in March when the IMC was locked, Elenna found the locations of the beam on IM4 Trans and ISS QPD:

IM4 Trans Pit (March 2026): 0.22
IM4 Trans Yaw (March 2026): -0.06
ISS QPD Pit (March 2026): -0.92
ISS QPD Yaw (March 2026): 0.94

We then worked to move IM2 to get to the right spot on IM4 trans, and then IM3 to get to the spot on the ISS QPD. The tricky thing is that, since we can't lock the IMC (IOT2 is away from the chamber, so no IMC REFL PD, so no IMC locking), we're just looking at flashes. So, the spot on the QPDs has to be calculated by looking at peak heights when we get a flash, and doing the matrix math to go from segments to pit and yaw.

.....After 23 different iterations of setting IM2 and IM3 based on an educated guess of where they should go, calculating the QPD spots, finding that we weren't quite right, and then tweaking again, we're leaving the IMs such that we're back to the March location on IM4 trans, but we're less on the edge for the ISS QPD. Current spots (calculated from the peaks of IMC flashes):

IM4 Trans Pit (May 2026): 0.2
IM4 Trans Yaw (May 2026): 0.05
ISS QPD Pit (May 2026): -0.53
ISS QPD Yaw (May 2026): 0.85

This helps assure us that we've got a pretty reasonable beam headed toward the ISS array, and that even if we didn't get the IMC alignment quite right earlier, we should be in a pretty reasonable place and we can use this beam to replace the ISS array.

One final thing we could do as a last check is to calculate the spots on POP A and POP B QPDs (or, at least the one that is used for initial alignment and acquisition), and make sure that we can move IM4 to get to that spot. That would mean that IM4 trans QPD and POP QPDs are both correct, which sets the pointing of the beam into the PRM and into the IFO, so if that line is correct in air and we use it to align the ISS array, then we will certainly be in a good place when we pump down. Again, this would just be a check that the IM1+IM2+IM3 position that we've got right now to give us good pointing to the ISS array is compatible with some IM4 pointing to the POP QPD. The individual segments aren't _DQed, so we'll have to check this tomorrow when the light pipe is open again.

Keita closed the light pipe for the night.

H1 IOO - Comment to Restoration of IMC alignment continues (Elenna, Sheila, Jenne, Keita)

elenna.capote@ligo.org — Mon, 11 May 2026 18:29:51 -0700

Author: elenna.capote@ligo.org

Report ID: 90205

At first, I only moved some combination of MC1, 2 and 3 because we believed that the pointing into the IMC was fine. However, as Keita summarizes above, this was a futile process and veru confusing because it sometimes seemed as if the camera, MC2 trans QPD and IM4 trans QPD all gave differing directions.

However, although Keita said that the beam hit MC2 in a good place, he did clarify this was within mm, so this gave us room to move around JM3 by many microradians. Then, we had this whole realization that JM3 pitch and yaw are flipped relative to IMC pitch and yaw, so some of our other confusion about what we were walking (and why it wasn't really working) started to make sense.

In the end, this is the process that worked: move JM3 a large amount, follow up with MC2 move and some MC1 move in opposite dof (so JM3 pitch goes with MC2/1 yaw). At first, I relied only on IM4 trans, but then the flashes on MC2 trans started to improve, so this became a much more useful signal to follow.

Below, I compare the OSEM readbacks of each suspension from before we started moving to now at the end of the day:

JM3 pitch (IMC yaw): -177 urad

JM3 yaw (IMC pitch): -93 urad

MC1 pitch: -186 urad

MC1 yaw: +83 urad

MC2 pitch: +58 urad

MC2 yaw: -62 urad

MC3 pitch: + 12 urad

MC3 yaw: +21 urad

We should probably put some note next to the JM3 sliders that the pit/yaw dofs are flipped compared to IMC pit/yaw, or I predict that we will recommit this mistake many times over!

Attached is a screenshot of the IMC aligned in air with associated signals (and dog)

Images attached to this report

H1 IOO - Restoration of IMC alignment continues (Elenna, Sheila, Jenne, Keita)

keita.kawabe@ligo.org — Mon, 11 May 2026 18:24:24 -0700

Author: keita.kawabe@ligo.org

Report ID: 90203

I went to HAM3 to see that the MC2 beam position wasn't crazy. See the first photo, the beam is to the left (+Y direction) relative to the baffle on the HR side but the baffle itself is offset in -Y direction relative to the cage. Green lines are extension of the EQ stop screws to guide your eyes.

I also opened the ISCT1 and moved the mirror in front of the REFL BBPD out of the way and directed the beam to IFO REFL camera (because I couldn't see the beam at all without moting the mirror).

While manually aligning the IMC, we found that somehow things are in such a bad state that the MC2 TRANS SUM decreases when IM4 TRANS SUM increases, and vice versa. Improving the IMC alignment using IM4 TRANS as well as IFO REFL camera made the flashes stronger to the point that we can see 00 mode once in a while. I was also able to see the beam in the ISS path. But MC2 TRANS was nowhere near centered. Attempts to resolve this by incremental changes failed.

We wondered if something behind MC2 was bumped and changed the alignment into MC2 trans. I looked at the path and didn't see anything obvious. The beam transmitted through MC2 was visible using a card and a viewer, it was not clipped by the baffle behind MC2 nor the BS for the beam dump. I could not see the transmission of the BS, though, it was too weak, so I cannot confirm if the steering mirror in front of the QPD was bumped or not.

Elenna started making big changes for JM3 in PIT (to make big YAW changes in the beam injected into IMC, remember that YAW and PIT are flipped between JAC and IMC, IMC WFS takes care of this but that won't help when you're manually aligning JM3) and moving MC2 and MC1 so that the IMC follows the input beam. Repeating this in YAW anShe successfully centered the beam on MC2 trans.

At this point I looked at the MC2 beam position again, see the second picture. Apparently the beam moved in YAW by a few mm to the right (i.e. -Y direction).

Elenna will post which optic was moved by how much in which direction.

Jenne is now trying to put IM4_TRANS and ISS QPD beam position back where they used to be using IM2 and 3.

INS, IOO, ISC

Images attached to this report

H1 IOO - Comment to Restoration of IMC alignment continues (Elenna, Sheila, Jenne, Keita)

keita.kawabe@ligo.org — Mon, 11 May 2026 18:14:54 -0700

Author: keita.kawabe@ligo.org

Report ID: 90204

We found that people opening BSC door cover(?) somehow disturbs IMC whether or not HAM3 and HAM2 door covers are on. The IMC fringe becomes super fast and it almost becomes impossible to align anything. Purge air seems to go to strange places to do strange things.

OTOH, when people are out of BSC, we had to put 0.2Hz 150cts excitation to MC2 M1 drive align L2L so the IMC goes across the entire FSR.

H1 COC - 2 of 4 AOSEM Flag Standoffs Glued

ibrahim.abouelfettouh@ligo.org — Mon, 11 May 2026 17:13:19 -0700

Author: ibrahim.abouelfettouh@ligo.org

Report ID: 90202

Ibrahim, Betsy, Rahul

Today we glued two of the four AOSEM flag standoffs onto S2 of BBS01.

After gluing, we wanted to make sure we were contacted evenly so an hour and a half later, we used magnets to remove the flags from the glued-on mounts.

We discovered that some glue was touching the bottom of the magnet bushings, so we elected to use some foil as shims to create more space between S2 and the bottom interface of the bushings.

Otherwise, the mounts were flat on the surface. We put the bushings back on for the overnight cure. See pictures below.

Images attached to this report

LHO General - Ops Day Shift End

thomas.shaffer@ligo.org — Mon, 11 May 2026 16:39:18 -0700

Author: thomas.shaffer@ligo.org

Report ID: 90197

TITLE: 05/11 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
SHIFT SUMMARY: The LVEA is still in laser hazard and will be for a few more days. The IMC alignment continues to prove difficult to get right. ITMY IAS finished up today. BBS work continues, CP1 regen, and more!
LOG:

1629 light pipe open

Start Time	System	Name	Location	Lazer_Haz	Task	Time End
19:43	SAF	LVEA IS LASER HAZARD	LVEA	Y	LVEA IS LASER HAZARD	12:03
15:07	VAC	Jordan	LVEA	yes	Checking on pumps and RGAs	15:17
15:27	CC	Ryan C	LVEA	yes	Grab dust monitor	15:42
15:43	FAC	Kim	LVEA	yes	Tech clean	17:13
16:26	ISC	Keita	LVEA	YES	HAM2/3 IMC alignment troubleshooting	18:20
16:27	ISC	Jenne	LVEA	YES	HAM2/3 IMC alignment troubleshooting	17:03
16:27	FAC	Randy	LVEA	yes	Measurements for more platforms around BSC3 area and emod area	16:47
16:29	IAS	Jason, Ryan C, Stephen A	LVEA	yes	ITMY Faroing in beir garten	20:16
17:15	VAC	Jordan	LVEA	yes	CP1 checks	18:25
17:36	FAC	Kim	LVEA	yes	Tech clean	18:19
17:49	VAC	Travis	LVEA	yes	CP1 work	18:31
18:17	SUS	Betsy, Ibrahim	LVEA	yes	BBS first contacting, suspension prep	19:50
20:06	SYS	Betsy	LVEA	yes	Checking that a chassis was turned back on	20:12
20:07	SAF	Ryan S	LVEA	yes	Checking on door	20:17
20:38	TCS	TJ, Madi	EX	Y	HWS table work	23:20
20:40	VAC	Jordan	LVEA	yes	HAM4 RGA	22:48
20:42	SUS	Betsy, Ibrahim, Rahul	LVEA	yes	BBS magnet gluing	23:42
21:13	ISC	Keita	LVEA	YES	HAM2 alignment	21:50
21:21	EE	Fil	LVEA	yes	HAM6 rack cabling	00:21
21:36	CAL	Tony	EX	-	Spinning up NCal	21:36
21:48	SPI	Jeff	Opt Lab	n	SPI work	23:03
22:19	SUS	Oli	CER	n	Taking rack pictures	22:23
22:25	PEM	Robert	EX	n	Grounding studies	00:25
22:49	VAC	Jordan, Gerardo, Travis	LVEA	yes	CP1 regen work	00:49
23:09	SEI	Jim, Michael, Shoshana, Stephen	LVEA	yes	Looking at cartridge and BSC2	01:09

H1 SQZ - Comment to SQZ beam profiles with different psams

sheila.dwyer@ligo.org — Mon, 11 May 2026 16:34:28 -0700

Author: sheila.dwyer@ligo.org

Report ID: 90201

Keita, Ryan Short, Tony, Sheila

In the saved PDFs, the units on "Beam Waist Position" are listed as um, but in the text file (which does contain all the same information), the values are the same but the units are mm. mm must be the correct units.

Looking at T2500077 we believe that to get from the reported Beam Waist position in the text file we need to add (z_stage_min - 4.4 mm= 122.9mm) to the distance from the reference plane as depicted in that diagram to the waist position. We believe that this waist position being positive means that the waist is after the reference plane (on the sensor side of the reference plane), I think a negative number would mean the waist is before the profiler.

I asked Claude to write a script to collect the data from the txt files in the archive above and save it in a yml, the script is attached here in case someone else wants it.

Non-image files attached to this report

thorlabs_to_yml.py

H1 PSL - PSL 10-Day Trends

ryan.short@ligo.org — Mon, 11 May 2026 15:22:20 -0700

Author: ryan.short@ligo.org

Report ID: 90200

FAMIS 63898 (I think. With the new system there are duplicate tickets, so I picked the one that has a schedule assigned.)

No major events of note this week.

Images attached to this report

H1 CAL - Spinning the NCAL with Micheal Ross

anthony.sanchez@ligo.org — Mon, 11 May 2026 14:57:24 -0700

Author: anthony.sanchez@ligo.org

Report ID: 90199

Micheal Ross showed up in the control room, so we spun up the NCAL.

It wouldn't spin at first because there was a current Latch reset button that needed to be pushed. Michael pushed System Reset and Latch Reset in rapid succession.
More documentation can be found here: LIGO iNCal Operating Procedures.pdf T2600149-v1.

We ran it for 4 minutes 30 seconds starting at 21:25 UTC.
H1:CAL-NCALX_MOVE_VELOCITY_VELOCITY_REQ was set to: 104 which translates to ~ 0.991 hz.
H1:CAL-NCALX_VELOCITY_KP_REQ: 0.0100 Mn/rad/s
H1:CAL-NCALX_VELOCITY_FILTER_REQ: 5 ms

NCAL ran.
Beckhoff I/O H1:CAL-NCALX_AXIS_ERROR_ID now has an Error status.

Pressing the system reset button cleared this Beckhoff I/O error status indicator.

Images attached to this report

H1 IOO - IMC_LOCK's OFFLOAD_MCWFS State Updated to Use JM3

ryan.short@ligo.org — Mon, 11 May 2026 11:10:09 -0700

Author: ryan.short@ligo.org

Report ID: 90198

Jenne reminded us that with the installation of the JAC, the process we use to offload the IMC WFS should be updated to use JM3's alignment instead of the PSL PZT since it's now the alignment mirror directly upstream of the IMC. I've done this in the IMC_LOCK Guardian node's code by essentially just doing a "find and replace" for the term "PZT" with "JM3" (and double-checking the result, of course), all of which happened in the OFFLOAD_MCWFS state. We'll test this state's functionality at a later date.

Changes have been committed to svn and loaded.

ISC

H1 AOS - Comment to Two HAM 3 POP-path optics are retroreflecting light scattered from MC1 and PRM

sheila.dwyer@ligo.org — Mon, 11 May 2026 09:03:29 -0700

Author: sheila.dwyer@ligo.org

Report ID: 90196

Here is a layout that may be helpful for understanding some of Robert's photos above: HAM3 IO paths

LHO General - Ops Day Shift Start

thomas.shaffer@ligo.org — Mon, 11 May 2026 07:37:06 -0700

Author: thomas.shaffer@ligo.org

Report ID: 90195

TITLE: 05/11 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: 0.01 μm/s
Secondary useism: 0.12 μm/s
QUICK SUMMARY: IPC errors on h1susMC2 and h1seiproc, dackill on h1iopseib2. All sus aligned and damped, SEI in state captured by the whiteboard. Temps look good and dust counts look good in the LVEA, the ends saw counts up into the 2000s during the last bout of wind 12 hours ago.

Laser hazard work in the LVEA continues today.

H1 SUS - Attempt at QOSEM Test on BSFM

thomas.roocke@ligo.org — Mon, 11 May 2026 02:47:57 -0700

Author: thomas.roocke@ligo.org

Report ID: 90194

[Tom R, Oli]

Summary: QOSEM testing on the BSFM will require the tablecloth to be shifted OR SUSP to be raised, probably not worth the effort to do so given the BBSS will be ready for QOSEMs shortly.

Last Friday Oli and I attempted to install the QOSEMs onto the now removed from chamber and on test stand BSFM suspension, now that the IAS work was completed. The purpose of this test is to run and compare TFs taken with QOSEMs, providing a final functionality test before installation on the BBSS (which is not yet ready to accept QOSEMs). The full test and integration plan for the QOSEMs / BBSS can be found here T2600169.

We began by removing the SD BOSEM from M1 of the BSFM, and swapping the flag out for the QOSEM variety. We installed the QOSEM onto the cage, and used the existing DB25 in vac extensions and in air cables to run the QOSEM to its sat amp in SUS-R2. The QOSEM and its entire signal chain was functional, with readouts from this SD QOSEM appearing as expected in CDS.

Unfortunately upon unlocking the suspension, to align this SD QOSEM, we found that its y axis could not be brought into range with the cams (at its best was ~1mm off). This is a similar issues we faced when setting up the BBSS at LLO. As the SD BOSEM does not have a readout in this 'y' or vertical direction, misplacement of the tablecloth by ~1mm is unnoticeable, and does not impede function of the BOSEMs, but as we are activity trying to readout this axis it does matter for the QOSEM.

As such, to setup the QOSEMs on the BSFM, we would need to raise the tablecloth, or SUSP via the blade spring angle. While this certainly could be done, at the moment this feels like an unnecessary amount of work to do for a quick test of the QOSEMs, given the BBSS will be ready shortly. For now we have abandoned this test, and removed the SD QOSEM from the BSFM, reinstalling the original BOSEM.

SUS

H1 AOS - Two HAM 3 POP-path optics are retroreflecting light scattered from MC1 and PRM

robert.schofield@ligo.org — Sun, 10 May 2026 17:45:44 -0700

Author: robert.schofield@ligo.org

Report ID: 90193

In order to search for retroreflections of scattered light that might recombine and cause scattered light noise, I take pictures from the point of view of the beam spot on important optics. The flash on the camera is right next to its aperture so, when the camera is held close to the location of the beam spot, the path of the light from the flash is similar to that of light scattered from the beam spot during observation, and glints in the photograph are indicative of potentiial retroreflections of scattered light. The distribution of light from the flash is, by design, more uniform than that of most scattered light, so more off-axis retroreflections in the photos tend to be less important.

An old photo taken from near the beam spot on PR3 showed a glint from an optic on the POP path so I re-took beam spot photos last week since we are baffling HAM3. The figure shows that I did not find a retroreflection in beam spot photos from PR3, but I did in photos from MC1 and from close to the center of PRM. I took beam spot photos with both my IR camera and cell phone – the figure shows cell phone photos as they are eaisier to interpret, but photos from both cameras show the same issues. I could verify these retroreflections and track them to their source by eye using a head lamp near my eyes. The PRM retroreflection is from the last optic on the POP path and the MC1 retroreflection is from the second to the last optic on the POP path (see diagram on the second page of the figure).

Im a little surprised that there are two of these random alignments, but I guess it is due to how small the angular differences between the paths from HAM3 to HAM2 are and the number of mirrors on the tables. I am also concerned that my beam spot photo technique only picks up retroreflections and not reflections of scattered light from one optic to a different optic. I would also like to make us more aware of these cross talk issues in planning optic paths and suggest that it might be worthwhile to develop code that checked for this.

I don’t know how bad these retroreflections are, but, in my photos, they are brighter than the reflections from ballast masses and the table that we are trying to baffle, so I may try to baffle the PRM retroreflection when we return to baffling. Im not sure how I could baffle the MC1 retroreflection without blocking the POP path.

Non-image files attached to this report

Beam-Spot-Photos-and-Diagram.pdf