Jim, Arnaud

The x12 in-vac BSC2 / BS ISI CPS sensors were replugged to their feedthrough as per D1003079. Jim worked from the platform, verifying the signals were live with a cds laptop while I was plugging them in from the chamber.  Before starting this work we turned on the interface chassis and had to power cycle corner 3 a couple of times before getting the -18V LED from the back panel to turn on.

I increased both BRS damping threshold defaults to stop the ringing behavior that we've seen after Beckhoff restarts. The defaults are hard coded into the BRS Beckhoff control under the follow lines:

H1_ISI_GND_BRS_ETMY_LOWTHRESHOLD: INT:=2000;(*~ (OPC : 1 : visible for OPC-Server)
                                        (OPC_PROP[0005] :3: read/write)
                                        (OPC_PROP[0101] :Lower Damping Threshold: DESC)*)
H1_ISI_GND_BRS_ETMY_HIGHTHRESHOLD: INT:=4000;(*~ (OPC : 1 : visible for OPC-Server)
                                        (OPC_PROP[0005] :3: read/write)
                                        (OPC_PROP[0101] :Upper Damping Threshold: DESC)*)

I changed the LowThreshold from 800 to 2000 and the HighThreshold from 2000 to 4000.

WP13318 h1crsproc model install

Shoshana, Arnaud, Jim, Jonathan, Erik, EJ, Ryan C, Dave:

We installed the first version of the h1crsproc model on h1seih23 at 09:27 Mon22jun2026PDT. Because this took one of the two spare cores on this W2245 machine, this required a reboot to force the exception to this rule. We will upgrade this machine to a W3323 before the RGC/IPC upgrade.

A DAQ+EDC restart was needed, no major issues were found.

[Shoshana]

Craned the CRS over to the temporary clean room over by HAM3 on 6/18. Unfortunately the flexures (SN13,SN20) broke during the transport process. It seemed like a clean break that was potentially caused by the proof mass jolting upwards crushing the flexures (photos attached), and the locks remained in place.

CRS was re-suspended chamber side HAM3 with flexures SN15/SN19, which is the last of the approved flexures of the first batch, but the other batch is ready for pickup. Suspension was painless as the locks kept the proof mass centered even after the break. The CRS CoM was balanced by eye.

There isn't an easily accessible outlet near the temporary clean room, so I was unable to get a resonance frequency measurement on Thursday. The hope is that because the proof mass remained locked when the flexures broke, the HoQI should hopefully still be mostly aligned with the CRS and only need small adjustments which will be done this week.

Late entry from Friday night.

Jordan, Gerardo (remote), Betsy (remote)

On Friday night (6/19) Gerardo noticed the purge air dewpoint had risen above our -40C requirement and continued to rise. Out of precaution, I came on to the site to check the purge air status and see if any HAM/BSC door covers had blown off the flange.

All door covers were in place, so no issue there. I then isolated the purge air from the lvea for ~30 minutes, therefore dropping the demand/duty cycle of the air comporessor, to see if the dewpoint changed. It slowly began to drop and I took local dewpoint measurements at the sample port just past the filters on the purge air skid. There was no significant difference in dewpoint when the drying towers cycled, the dewpoint remained around -38C regardless of which tower was drying. 

After ~30 minutes, the dewpoint had dropped to -43C and so I reopened the purge air to the lvea, then reduced the flow at the purge air port on the output tube. It seems there was just too much demand on the compressor.

As of this morning, the dewpoint has returned to normal -51C at the drying towers. 

TITLE: 06/22 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: 17mph Gusts, 10mph 3min avg
    Primary useism: 0.04 μm/s
    Secondary useism: 0.09 μm/s 
QUICK SUMMARY:

• HAM7 work, CRS work, possibly more FARO HEPI alignment planned for today
• IFO alignment checks

Using the same settings as 2021 the PID control of CP1's level is maintaining the 92% setpoint nicely.

Jennie W, Jeff K, Josh F, TJ S,

Summary: SPI interferometers aligned, shroud installed successfully. One stray beam and possible clipping on shroud to investigate/deal with but otherwise all problems were solved. Obligatory success photo taken by Josh.

Today we:

• reseated the M_M5 mount in its holder. We had troubles with this stick-slipping when we tried to move it. Jeff replaced the 45 deg adaptor part D2400336-v4 S/N 001 type 1 with S/N 002. This seats better in the holder.
• realigned beam to QPD A and B using picomotors M_C1 and M_M1.
• Confirmed other two picomotors M_B4 and M_M2 work and their pitch DOF (in breadboard basis) matches left/right on picomotor controls.
• We had some weirdness in the meas IFO which Josh has solved and will discuss in other alog from Josh (LHO alog #90680).
• During this debugging we used the oscilloscope to plug into analog outputs for meas and ref IFO and a commercial RF source.
• We used the breadboard steering mirrors to get 85.9 % heterodyne efficiency on the reference IFO PD A and 88.9% efficiency on reference IFO B.
• With no adjustment the measurement interferometer PD A had 86% efficiency and PD B had 93.4% efficiency so we will take this (ch4 on scope is PD A, ch2 is PD B).
• This afternoon we installed the shroud around the ISIK breadboard.
• We had to move the fiber spools to avoid the bottom shroud bracket and these are now close to the edge of the beam tube where it meets HAM3 in the -x direction.
• After installing the shroud panels both QPDs had dropped in power by ~2V, will investigate on Monday as the beam does not appear to clip the shroud when we check with the card.
• There is also a stray beam from the FBR_PWRIN_REF PD that hits the upper shroud stand-off on the lower panel on the -y side and then hits the door cover, this will need dumped somehow.
• After moving the fiber spools I checked the FBR PWRIN channel for meas and ref and these both drifted after we rerouted the fibre spools but the level seems to have been dirfting more than this since we got into chamber this afternoon at 14:20. The first cursor in the photo is when we started moving the spools and the second is when I shuttered the laser.

J. Freed

Found the problem discribed in 90644, as well as the strange sawtooth beat notes we have been finding in our IFOs. It was user error on our CDS system, the double mixer (which produces our REF RF signal for AOMs) requires a sin wave and cos wave 4096Hz signal. We were sending it 2x cos signals.

This also explains why our demod systems were not working as they use the same signals.

Sheila, Keita, Betsy, Elenna, Ibrahim, Oli, Tom, Camilla. Follow on from 90656

Summary: For BS alignment checks, we spent some time with the SQZ beam to check that we are happy with the SRC pointing. We could not find a beam using the BS sliders only. But we could see SQZ beam reflected off both ITMX and ITMY on the IR viewer paper at PR2. Beam splitter is being moved to overlap these SQZ beams. 

With ITMY aligned, SR2, SRM mis-aligned, we expect 2.5 counts of AS_A and AS_B (1.25mW * 0.3 SRM * 0.5 BS * 0.5 BS * 0.3 SRM), we could get this on AS_A and AS_B after we reverted SR3 to O4 sliders and started with SR2 at O4 sliders but moved significantly to get light on AS_A and AS_B.

Once SRM was aligned, we could see a beam not centered on the camera. We then realized the ITMs were far off (for Oplev centering in 90443) and then started taking ITMY back towards sliders walking with SR2 (ZM6 didn't have enough range) to get a round beam more centered on AS_AIR camera. *Sheila was later unsure we should have moved ITMY like this. 

After this we could see SRY fringes, there were +/-10 counts in size. 

We then took ITMX to it's oplev positions last time we had DRMI lock (19 March 2025 18:02 UTC). The sliders/L2 WIT osems were still ~30urad off, think this is okay for this gross BS alignment. 

Sheila put a large wobble on the BS while we had ITMX only aligned and we watched the AS_AIR camera and AS_A/AS_B. We could not find the beam off the BS at the HAM6 sensors. 

Betsy then went into the chamber and could see the SQZ beam reflected off both ITMX and ITMY on the IR viewer paper clipped at the baffle in front of PR2. Sliders helped bring these beams together but was not enough. Beam splitter is being moved to overlap these SQZ beams...

(Jordan, Travis, Jake, Owen, Gerardo)

After taking some RGA scans of CP1, and pushing nitrogen gas through the cryotrap (we injected nitrogen gas at the top sensor line for about 10 minutes), then we started the cooldown, or did we?  First, we opened the "bypass" valve (fully open) to measure the number of turns to guesstimate a less than 10% open valve, per procedure E960127. Then we opened the bottom draw valve to release LN2 out of the dewar.  We opened both valves around 2:00 pm, bottom draw fully open and bypass valve only 10%, but by 7:40 pm local time we terminated the cooldown, we didn't want to risk for something to go array overnight. 

We did not see a sign that the cryotrap was getting nitrogen, nothing on the exhaust (the exhaust pressure remained the same), nothing on the cryotrap level (remained at zero), pressure internal to the cryotrap remain level, and the consumption remained level at the dewar for CP1.  We are going to look more into this Thursday.

Summary: Since I had trouble seeing a noticeable improvement in jitter by looking at the IMC WFS in this alog #89988 where the PSL output power was 2W, I looked at times when we were at 10W PSL output power to see if we were limited by shot noise. The measurements at 10W show that we might have decreased jitter but I checked the QPD sum values for the measurements after JAC was installed vs. before and we are near the edge of the QPDs.

I took reference times, when our input power was 10W to see if this gave a better measurement of jitter

Time 1: 2025/11/17 16:13:17 UTC during initial alignment. Without JAC.

Time 2:2026/03/19 15:31:23 UTC during commissioning when HAM1 was at vacuum.

Image one shows the yaw measurement, there is again a difference in the value at DC of the QPD ASDs. It looks like the peaks seen between 40 and 1000 Hz are slightly better with JAC than without JAC but it is only obvious on WFS A and B QPDs (top left plot comparing green and purple lines for WFS A and red and yellow lines for WFS B).

Image two shows the pitch measurement, there is again a difference in the value at DC of the QPD ASDs. It looks like the peaks between 40 and 1000 Hz are slightly better with JAC than without JAC but it is only obvious on WFS A QPD (top left plot comparing green and purple lines).

I also checked that the QPD sum values changed between my reference times during O4 and after JAC installation. See these four images.

1. 2W reference time during run. A and B QPD SUMs were arpund 0.03 counts.

2. 2W reference time after JAC installation. A and B QPD SUMs were arpund 0.002 counts. Maybe we are now nearer the edge of the diode?

3. 10W reference time during run. A and B QPD SUMs were around 0.16 and 0.13 respectively.

4. 10W reference time after JAC installation. A and B QPD SUMs were around 0.009 and 0.008 respectively. Maybe we are now nearer the edge of the diode?