TITLE: 04/10 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: 4mph Gusts, 2mph 3min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.14 μm/s 
QUICK SUMMARY:

IFO is in IDLE for MAINTENANCE

BSC2 and HAM3 prep and vacuum work to continue

It dawned on me recently that with the scratched view ports for CHETA, the delay of the CHETA roll out could have a subtle saving grace.
The intended use for IR1 is to heat the ITM with the same power as the absorbed power, so that the ITMs would remain in more or less the same thermal state at all times, making DRMI locking fast and reliable, and removing some of the impact on SRC detuning changing over time as the ITM lenses would evolve less than in O4.
It appears that in the CHETA Design Document, the effects on mode spacing and therefore Parametric Instabilities (PIs) was completely overlooked. Shame, no PI expert in LIGO was consulted, I'm even an author on the cited document in the design document and how we used CHETA like actuators at UWA to mitigate PI.

Very simplistically, rolling out CHETA only for the ITMs (as was the plan for the upcoming IR1) would have two impacts on how the optical mode spacing evolves:

• Mode spacings would start closer to the final, thermalised, frequencies.
• They would evolve with the same time constant (only ETM heating) as in O4, to the thermalised state.
  • But! Because they start closer, the mode spacing would evolve slower.

In O4 LHO's QUAD Radii of curvature's operating point has them stuck between two lock-losing PIs, and they haven't managed to demonstrate reliable damping of either. This lead to several periods in O4 where their lock stretches would be repeatedly cut short at around 4 hours.
The implementation of CHETA on ITMs only would have put them closer to their 10.4 kHz PIs as a starting condition, and because the mode spacing would be changing more slowly over time, they would experience the frequency matched condition of PI for longer periods of time. Thus:

• LHO would lose locks more reliably.
• LHO would have shorted locks.

I could spend time modelling this but its blindingly obvious once you notice.
CHETA on both ETMs and ITMs would theoretically allow you to start with essentially thermalised mode spacing, allowing you to more reliably side-step PIs.

Jenne, Oli

JM3 is no longer saturating.
During this investigation, we ended up finding the last time that we offloaded MC WFS, so for future reference, the last time we offloaded MCWFS was 2026/03/10 21:51 UTC.

JM3 Saturating
Earlier TJ noticed that JM3 was saturating. I went to take a look and found that the overdamping on JM1 and JM3 that had been done for in-chamber work at the beginning of April (89732) hadn't been undone, so now that the HAM1 doors were on, the damping was just way too much(JM1, JM3). I reverted these damping changes on both JM1 and JM3(JM1, JM3).

However, this didn't stop the saturations on JM3. The LOCK filter bank was sending in large negative numbers that were coming in from WFS DOF3 P and Y. With Jenne's help, we were able to sort of figure out what had happened.

The channel we look at for triggering the IMC WFS is IMC-IMC_TRIGGER_INMON, which is IMC-MC2_TRANS_NSUM_OUT_DQ divided by IMC-PWR_IN_NORM_MON. It seems like for some reason this morning IMC-MC2_TRANS_NSUM_OUT_DQ started going up, probably from noise and light in the LVEA, and ended up triggering the IMC WFS (the value was actually still lower than the trigger threshold of 40 so that's still a mystery though). Anyway, once the WFS were triggered, they were turning off and on over the next 4.5 hours. This caused garbage noise to build up in the DOF integrators, which got sent out to MC1, MC2, MC3, and JM3.
We cleared history on these filter banks, which fixed JM3.

IMC_LOCK Guardian Request
We think that something should be put into the IMC_LOCK guardian so that when we go through MOVE_TO_OFFLINE, something happens to prevent the WFS from turning on, like turning off the DOF inputs. Then when we go through DOWN, we turn the WFS inputs back on. This would prevent the integrators from building up garbage noise like what happened here.

TITLE: 04/09 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY:
HAM3 +Y door is removed
BSC1 door bolts are being broken.

GRB- Short E632727 17:33 UTC  notification (IFO status: Vented .)

Both HAM3 doors are Off. 

I have attached screen shots of all of the SDF Diffs from EX & EY before the CDS team rebooted  IOPs for both End stations after Marc replaced the IOP Ribbon cables.

20:26 UTC EX IOP Restarts 
20:58 UTC EY IOP Restarts 
Started to bring EX back up at 21:12 UTC untripped watchdogs for HEPI & ISI.

Fil is unplugging some IMC cables.

JM3 Looks to have grown in motion over the last few hours for some reason. Oli believes that JM3 is "Over damped" due to the wrong gain not being reverted,  Oli's alog with more detailed coming soon.

BSC2 dust mon counts for the day.
 

(Jordan V, Corey G)

In prep for upcoming BBSS Install, "broke" bolts (which is slang for loosened them) on:

• BSC1's +Y Door in the Beer Garden
• BSC2's Dome (to see if giving the Dome's O-Ring some time to "decompress" helps us out at all with removal next week).  

BSC1's +Y Door Bolts (mostly) Removed & Accelerometer Cable Disconnected

BSC1's door had all bolts but (4) removed.  Sadly, I removed the bottom (easy ones) bolts first and then when I got to the top bolts they were very hard to loosen because of some sag.  Additionally, their access is horrible with:  a stiffening plate for the chamber right above the rear access to these bolts, then there are cable trays also in the way, and the C3 fabric cover is draped in your face the whole time.  Jordan helped out and we were able to get the last top bolt removed.  We also loosened the (4) bolts 1-turn which is the typical procedure.

There was an accelerometer still cabled up to this door.  I disconnected the cable (labeled "PEM:BSC1_ACC_X") and stuffed the cable into the cable tray above this door.

Time lapse of me removing half the bolts in this LINK (since we only files allowed in alog have to be smaller than 15Mb.)  :(

BSC2's Dome Bolts (mostly) Removed, But Have A Galled Bolt!

BSC2's dome bolts were removed.  4-bolts were left in place (they were loosened and then tightened up a little).  One notable, is there is 1-galled dome bolt.  Jordan and I used the long wrenches to see if we could use more force to help it break loose, but no luck.  We did not try pouring some alcohol on the bolt to help as a lubricant.  The bolt is loose and has about 1-2mm of a gap on it.  So, the pros could try use even longer cheater bars, a saw cutter, or they were also chatting about a tool to cut the nut off.  At any rate, 

(Jordan V., Travis S., Randy T., Corey G., Gerardo M.)

The removal was somewhat cumbersome for both doors, but the doors are off HAM3, on the +Y door both O-rings popped out at the bottom of the chamber, they were easily coaxed back into the O-ring groove, both O-rings were out from 5 to 7 O'clock, both bolt holes at this location have traces of "rust".  The -Y side door was a bit more sticky, it took some time to convince the door to come loose, and we had O-rings out of the groove from 4:30 to 6:15 O'clock, both of them at one point.  They went back into the O-ring groove without a major issue.
Flange protector were installed and both C3 covers, purge is up.

[Oli, Elenna]

Summary: Oli and I finished the alignment of all the optics on the BHSS. We were able to place beamdumps to capture the reflected beams off of the four QPDs.

Oli wrote up a summary of the work from yesterday, 89836, and they noted a mistake in the alignment of the B path. We were able to correct that alignment, so the reflected beam from QPD-T-B-R2 goes to QPD B 1 and the transmitted beam reflects off QPD-T-B-R3 to the QPD B 2. Keep in mind that we are following the naming convention that's currently in D2000405 and the BHSS build document T2100190. We found that we had placed B-R2 one hole wrong yesterday, and once we had corrected this, it was much easier to center the beams on the mirrors and get them to the correct QPDs.

Oli briefly described this issue yesterday, but I want to emphasize again: we struggled to use the D2400130 alignment template to align the mirror called "36-R1". This mirror is a high reflector that steers the beam to a splitter that splits to the on-platform OMCB REFL path, and then off-platform to the LO WFS. Because this mirror is a high reflector, it has black glass clipped to the back, and the screw to hold the clip in place protrudes and interferes with the place the optic is supposed to press against the alignment template. This means we have to slightly rethink the HAM6 table alignment plan slightly. I think, since we have aligned the subsequent beamsplitter to the OMCB REFL path, we can follow these steps:

• use the OMC iris alignment template to align the input beams to each OMC, remove when finished
  • placing this alignment template requires removing the three optics at the head of the manta ray (A-R1, B-R1 and 36-1)
• use D2400130 to align A-R1 and D2400129 to align B-R1
• Use the reflected beam from OMCB and the placement of B-R1 and all downstream optics to find the correct placement of 36-R1

These steps will vary slightly depending if we only do the phase A install, or we do phase A and B together. If we only do phase A, we will just have to guess the 36-R1 placement for now, because there will be no beam to check it.

We are ready to go for cable routing and butterdish clamping on the BHSS!

The BSC2 E3-2 blank was removed and a Type 'C' Dual 25-pin feedthrough (D2000223-S2000697) was installed in its place.  

Dripta and I went to EY with PS4 to do a PCAL ES measurement. We followed the  T1500062-v21 Procedure  but there were changes to the scripts we were using to do the analysis for this measurement. 
Obligitory before beam spot. 

python3 generate_measurement_data.py --WS PS4 --date 2026-04-02
Reading in config file from python file in scripts
../../../Common/O4PSparams.yaml
PS4 rho, kappa, u_rel on 2026-04-02 corrected to ES temperature 299.9 K :
-4.7013350503199405 -0.0002694340454223 0.0007506545774987483
Copying the scripts into tD directory...
Connected to h1daqnds1
martel run
reading data at start_time:  1459616830
reading data at start_time:  1459617300
reading data at start_time:  1459617635
reading data at start_time:  1459618001
reading data at start_time:  1459618370
reading data at start_time:  1459618700
reading data at start_time:  1459619030
reading data at start_time:  1459619580
 reading data at start_time:  1459619930
Ratios: -0.5341166097396405 -0.5439653195648569
writing nds2 data to files
finishing writing
Background Values:
bg1 =        18.656956; Background of TX when WS is at TX
bg2 =        5.029697; Background of WS when WS is at TX
bg3 =        18.678297; Background of TX when WS is at RX
bg4 =        5.152238; Background of WS when WS is at RX
bg5 =        18.675415; Background of TX
bg6 =        -0.527308; Background of RX

The uncertainty reported below are Relative Standard Deviation in percent 

Intermediate Ratios
RatioWS_TX_it      = -0.534117;
RatioWS_TX_ot      = -0.543965;
RatioWS_TX_ir      = -0.526729;
RatioWS_TX_or      = -0.535441;
RatioWS_TX_it_unc  = 0.057495;
RatioWS_TX_ot_unc  = 0.055038;
RatioWS_TX_ir_unc  = 0.052784;
RatioWS_TX_or_unc  = 0.054928;
Optical Efficiency
OE_Inner_beam                      = 0.986428;
OE_Outer_beam                      = 0.984304;
Weighted_Optical_Efficiency        = 0.985366;

OE_Inner_beam_unc                  = 0.042212;
OE_Outer_beam_unc                  = 0.043766; 
Weighted_Optical_Efficiency_unc    = 0.060806;

Martel Voltage fit:
Gradient      = 1637.917034;
Intercept     = 0.063908;

 Power Imbalance = 0.981895;

Endstation Power sensors to WS ratios::
Ratio_WS_TX                        = -0.927573;
Ratio_WS_RX                        = -1.384310;

Ratio_WS_TX_unc                    = 0.046237;
Ratio_WS_RX_unc                    = 0.042014;

=============================================================
============= Values for Force Coefficients =================
=============================================================

Key Pcal Values :
GS           =      -5.135100; Gold Standard Value in (V/W)             
WS           =      -4.701335; Working Standard Value             

costheta     =      0.988362; Angle of incidence
c            =      299792458.000000; Speed of Light
             
End Station Values : 
TXWS         =        -0.927573; Tx to WS Rel responsivity (V/V)
sigma_TXWS   =        0.000429; Uncertainity of Tx to WS Rel responsivity (V/V)
RXWS         =        -1.384310; Rx to WS Rel responsivity (V/V)
sigma_RXWS   =        0.000582; Uncertainity of Rx to WS Rel responsivity (V/V)

e            =        0.985366; Optical Efficiency
sigma_e      =        0.000599; Uncertainity in Optical Efficiency

Martel Voltage fit : 
Martel_gradient         =        1637.917034; Martel to output channel (C/V)
Martel_intercept   =        0.063908; Intercept of fit of     Martel to output (C/V)

Power Loss Apportion : 
beta          =        0.998844; Ratio between input and output (Beta)  
E_T          =        0.992082; TX Optical efficiency 
sigma_E_T          =        0.000302; Uncertainity in TX Optical efficiency 
E_R          =        0.993230; RX Optical Efficiency 
sigma_E_R          =        0.000302; Uncertainity in RX Optical efficiency 

Force Coefficients : 
FC_TxPD          =        9.158224e-13; TxPD Force Coefficient 
FC_RxPD          =        6.227715e-13; RxPD Force Coefficient 
sigma_FC_TxPD          =        4.284257e-24; TxPD Force Coefficient 
sigma_FC_RxPD          =        2.800786e-24; RxPD Force Coefficient 
data written ... to /ligo/gitcommon/Calibration/pcal/O4/ES/measurements/LHO_EndY/tD20260407
 

Martel_Voltage_test.png 
WS_at_RX.png 
WS_at_TX.png 
WS_at_RX_BOTH_BEAMS.png 
Final Report is here: LHO_EndY_PD_ReportV6.pdf
Final beamspot .

Thu Apr 09 10:07:34 2026 INFO: Fill completed in 7min 31secs

WP 13154
a-Plus O5 SUS HAM5 (sush5) System Wiring Diagrams - D2300380
aLIGO SUS HAM 5-6 System Wiring Diagrams - D1002740

SUS-C7/ SUS-C8
Two HAM-A coil drivers were installed in the SUS-C7 rack, part of LO3. We decided to use the existing OMC cables for the new OFI. Cables are going to correct CER and field rack. OMC is being moved to the MER. Once HAM6 is vented the OM1/OM2/OM3 electronics and cabling will be removed.

SEI-C1
Started clean-up of the SEI racks. Removed a HAM ISI Interface Chassis from SEI-C1. This was part of the HAM1 L4C testing back in 2018. Plan is to remove the STS distribution electronics. See alog 89835 for testing of sending signals over IPC.

ISC-C3
The Heliax cable for SPI was landed in ISC-C3 (Patch Panel U37/U38, port 4) 

LVEA Work
Finished routing the ±18V power cable for CHETA Y around BSC8 and BSC1. Cable was landed in the TCS-R2 rack. We spent some time cleaning cabling in the TCS rack and the space between the TCSY enclosure and BSC1.

F. Clara, C. Gray

Wed Apr 08 10:07:42 2026 INFO: Fill completed in 7min 39secs

Late entry for yesterday's fill.

TITLE: 04/09 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: 3mph Gusts, 2mph 3min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.16 μm/s 
QUICK SUMMARY:
Work today is Likely going to be removing bolts from chambers HAM3, BSC1, And BSC2's Dome.
 

(Jordan V., Travis S., Gerardo M.)

To get ahead on door removal, we vented a couple of anuli systems, and we used nitrogen to vent BSC1, BSC2 and HAM3.  No issues to report for any of the vents.

Also, we removed most of the bolts from HAM3 chamber doors.

Elenna, Madi, Oli

Today we started tackling the alignment of all the REFL optics that go on the BHSS.

A Path
The A path went relatively smoothly. We had an issue with A-R1 where we had the left side alignment template D2400130 correct and placed A-R1 in it correctly, but the angle of A-R1 was off and sent the beam into the side of the OMCA butter dish. This was possibly due to an error with the clocking tool, but since Elenna had roughly placed the downstream optics last week, we were able to easily fix it by rotating A-R1's mount until it was shooting down the right way. We then were able to get the rest of the REFL A path worked out pretty well, just not the beamdumps.

B Path
The B path caused a few more issues. First, trying to place 36-R1 using the left side template, we realized that we couldn't actually use the tooling since 36-R1 has a J-holder for the black glass, and the screw that holds the J-holder in place doesn't screw in all the way - there are a couple of threads that stick out. Those couple of threads mean that the screw is in the way of the optic sitting in place in the template. To work around this, we ended up installing B-R1 using the right side template, and once we had that we used that as a reference to get 36-R1 reflecting OMCB REFL towards it. Later, we had some trouble getting the beam to B-R3 while also keeping B-R3 at the correct screwhole. We ended up moving it over one screwhole to the left, from L8 / T13 to L9 / T13. At this point we just roughly aligned it to go towards the QPD and left it for now since we might need to move it back over. We might end up needing to shift all the optics in that line over ?
UNFORTUNATELY, we also made a mistake. We aligned B-R2 to hit the B-2 QPD, and B-R3 to hit the B-1 QPD, but it's supposed to be the other way around. We will have to correct this next time!

TITLE: 04/09 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY:
Vacuum team has been Venting the corner station still. 

OMC's were taken to SAFE for a model reboot then taken back to aligned.

Dave and Marc  swapped some cables and restarted the following IOP's & models today. Please check your SDF's haven't been reverted.

H1IOPOMC0 
H1IOPOAF0 
H1IOPASC0
Tagging teams that may have SDF issues in the future.

SRM taken to aligned. (I have no idea Why it was misaligned.)

IMC Input Power Channel is no longer "Cray Cray" and is now reading correclty as of Jennie D's alog.

Restart ISI models BSC 1,2, & 3 
FW1 Down 19:15 UTC
DC0 down 19:20 UTC 
DC0 Re-established at 20:36 UTC  

ISI BS Stage 1&2 watchdog tripped 20:36 Likely due to Vac activities. 
ISI HAM3 WD tripped 23:33

VAC team says BSC2 annulus is vented & Dome bolts ready to be broken. 
 

LOG:

Jeff and I started looking at HAM ISI signal chains to see if there were enough AA inputs for the planned upgrades during this install cycle. We realized that we still have all of the cabling for the original distribution of STS channels, where each STS is connected to one of the BSC front-ends, the signal goes through a distribution chassis that then sends copies of that STS to each of the other front-ends before sending signal to the source front-end AA, sort a physical ipc. This means each HAM rack has 3 db9 AA ports taken up by a signal distribution chain we no longer use, each BSC has 2.

Until today, ITMY sent its collection of 1 directly connected STS set of channels (the HAM2 (or A) STS) and 2 distributed sets (ITMY (or B) from BSC2 and HAM5 (or C) from BSC3) over IPC to SEIPROC, where it was calibrated, then used for a sensor correction signal that got sent back out to all of the corner seismic. This means we can free up AA ports by removing the rat-king STS distribution set up and just use the IPCs. Doing this required redistributing the IPCs for each STS to the front end model the ground sensor was directly connected to.

Arnaud is working on the ECR (with the helpful cartoon of what is being changed in p. 2 here), but I wanted to test the changes needed to do this today. I disconnected the extra connections for the shared STS signals between each BSC, leaving just the AA cable for each chambers directly connected STS. I then split out the 9 IPCs from ITMY to each chamber. Dave and EJ found a bug where I had mistakenly used an ADC selector instead or a bus, so I also fixed that in a couple places on the top level for each chamber. Somehow this had been before this point, but today meant the wrong channels got picked out for the BS STS IPCs. Dave also had to do some editing of some other files that had to do with the IPCs, because the sender models were changing, but not the names of the IPCs.  

As far as I can tell at the moment this seems to be working. Corner is vented, so testing sensor correction performance will be difficult, but I can at least check that the signals look like ground motion and do a couple other checks.

Per WP13110 we have upgraded the IO chassis listed below.
This link contains the asbuilt for all of the H1 IO Chassis: https://dcc.ligo.org/LIGO-D1301004
This link contains the ECR for the IO Chassis sync cable upgrade: https://dcc.ligo.org/LIGO-E2600069

This link is to the work in progress spreadsheet LHO Front Ends Upgrade Status

Corner:
SUSB2H34 has upgraded firmware and sync
SUSAUXB2H34 has upgraded firmware and sync
SEIH7 has upgraded firmware and sync
OMC0 has upgraded firmware and sync
OAF0 has upgraded firmware and sync
ASC0 has upgraded firmware and sync
LSC0 has upgraded firmware and sync

We started the venting process for the corner today, including the FCB1 section of the filter cavity attached to BSC3

GVs Closed:

GV2, GV5 (GV7 remains soft closed until repairs are done on the piston cylinder), RV1, FC1, 2, 4, 5.

Dry air dewpoint at vent port = -40.3C

We followed the venting procedure E2300169, until the small burp of dry air into the corner volume, during this "burp" we noticed a small pressure increase at PT114 (CP1 gauge on beamtube side of GV5). There was a clear pressure step from 2.02E-9 to 2.04E-9 Torr at the same time as the dry air burp, see attachment.

We waited for ~15 minutes and repeated the air burp into the corner, again we saw another pressure increase at PT114, though the pressure gauge on the opposite side of CP1 PT124 showed a small decrease at the same time as the pressure increases. 

We paused the vent to investigate, PT120, PT114 and PT124 are all pirani/CC gauge pairs and we are investigating if there is any potential crosstalk at the vacuum rack that could be causing this.

More to come.