TITLE: 05/28 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: Ryan S
SHIFT SUMMARY:
Epochs of locking:
When I first got in to the control room I ran a full Auto initial alignment.
This lead us to no flashes on DRMI & PRMI.
We then manual initial alignment through a few PRX steps.
Which gave us flashes, but after that we had some noise on the beam splitter oplevs.

Then a REFLAIR phase issue was overcame.
Mean while the SQZrs are turning on the laser and did some aligning on the SQZ tables.
Then unknown 70hz feature was later found out to be ISI in HAM1.

The VAC team checked HAM1 for leeks, and didn't find any.


LOG:

TITLE: 05/28 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Planned Engineering
OUTGOING OPERATOR: Tony
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 14mph Gusts, 3mph 3min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.11 μm/s
QUICK SUMMARY: H1 locking continues this evening; currently have made it up to CARM_TO_ANALOG and have paused to measure CARM OLG. More SQZ table work also going on.

J. Kissel, J. Warner, S. Dwyer, O. Patane, E. Capote, T. Sanchez

After finally making progress past Beam Splitter optical lever glitching (LHO:84631), a poorly phase REFLAIR sensor set for PRMI (LHO:84630), and adding loop gain to the REFL DC centering loops (LHO:84623), we were just about to see some success and made it ISC_LOCK's RESONANCE state.

Alas, Jim started commissioning/debugging the HAM1 ISI loops (in a different room), trying to carve out some time to deal with a ~70 Hz feature in some DOFs of the plant. In doing so he made sure to turn off the DOFs he thought were problematic (RX / RY). LHO:84638

We (including Jim) now know that even only having the X, Y, Z, and RZ loops closed, the ISI HAM1 X loop slowing goes into oscillation slowly, on the order of 5 to 10 minutes after the ISI is isolated.

This manifested in IFO commissioning in very confusing ways mostly because of the timing of events (and the "front row" didn't know that Jim had started commissioning the ISI). The first attachment "shows" this story.
    - The first re-acquisition after an unrelated lock loss started with the ALS COMM's out-of-loop sensor (H1:LSC-TR_X_NORM_INMON) oscillating at 70 Hz, i.e. "looking fuzzy" on the wall "DRMI buildups" screen.
        (See bottom, 5th panel.)
    - It started to dissipate in the middle of this acquisition (we now know because Jim was independently cycling the ISI Isolation loops)
        (See 4th panel)
    - But by the time that DRMI was locked, the "fuzziness" oscillations started to reappear.
        (again, see 5th panel)
    - All the while we notice that MC2's M2 stage -- feedback for the IMC -- is saturating. This in itself is confusing because our impression is that the IMC F / IMC L cross-over is at ~15 Hz, so "there shouldn't be any drive from the IMC common mode board to MC2 up there, especially not offloaded to the M2 stage."
        (see 2nd and 3rd panels)
    - But also, "why is the IMC seeing any HAM1 motion?"

I also attach an ASD of IMC F, the middle stage of MC2's DAC drive, and the HAM1 and HAM2 ISI motion. These clearly show the 70 Hz feature, and show nothing in HAM2.
I call out the "nothing in HAM2" to dispel the suspicions that vacuum equipment that's still vibrating and moving the HAM1 / HAM2 chambers is causing this noise. It's not. It's the oscillation in the ISI HAM1 loops.

Here's why "the IMC is seeing HAM1 motion:" at this point in the lock acquisition, ALS COMM is inserted as an additive offset to the IMC's Common Mode board, which drives MC2 length and the PSL frequency (see e.g. the difference between pg 12 and 13 of G1400519). This is why the MC2 M2 DAC request is peanuts when the IMC is locked alone, but then is gigantic once the ALS COMM signal is ramped in to push the laser frequency around to find the X arm resonance in IR. The ALS beam is "caught" in HAM1 with a periscope and steered around the table before being sent on to ISCT1. So the unstable 70 Hz motion in the new HAM1 ISI is imprinted there on the beam, which is then used to inform ALS COMM, which is then fed to the IMC.

For now, we're going to leave the HAM1 ISI loops off and carry on with ISI commissioning, and give Jim some dedicated time to figure out the issues with the ISI.

J. Freed

Contiuning the work from 84198 this alog is about characterizing the other components of the Double Mixer. D2400315

D2400296 PCB Board transimpedance amp

According to oscilloscope, the signals coming from PCB board are from J2 being cos and J3 being sin. The Vpp are 1.199V on J2 and 1.195V on J3. As before the phase measures are hard to get a read on as the phase measuremnt on the osciloscope says 90deg when I put J3 in the channel 1 position and 91deg when I put J2 in the channel 1 position. Instead I put a 4096 Hz signal generator on Channel 2 then put the of the sin and cos signals on channel 1.

ZLW-1BR Mixer

The mixer data was collected at a range of values incase LO input power needed to be changed, however I would not recomened going below 4dBm LO as the isolation of all the ports falls gets worse the lower the power. The indivitual signals were colected on the Agilent 4396B with a BW of 10 Hz (best one the spectrum analizer allowed without giving an overload notification). While the Total power was given on the E4418A power meter. SRS SG382 was used for the LO power.

ZMSC-2-1BR Combiner

The combiner values were colected by using the Agilent 4396B to apply a sweep of values around 80 MHz. All values were the same in about a 10kHz span that was measured

ZMDC-10-1+ Couplier

The couplier was characterized by applying a -1dBm from a SRS SG382 signal generator signal at 80MHz on the input port and reading off from the E4418A power meter. The other port not being measured was terminated. We do not care about relative phase so it was not collected

Camilla, Vicky

We found the PSAMS servos on ZM2/4/5 were railing (initially set up in 80685), so we reset them and tried to make it more robust for next time. What we did:

• Turn servo gains to 0
• Clear history on filter banks (ran into this problem before already 81697)
• In the filter banks, we changed the integrator "p0" to have Input = Zero History, Output = Ramp, and Ramp Time = 10 sec. At first we were having an issue that turning the filter bank gains to 1 caused the PSAMS servos to slam on and saturated the limiters. Having the 10-sec ramps on both the "p0" filter output and on the filter bank helped. We have previously lost lock  by slamming on the PSAMS servos so hopefully this helps in general. We SDF'd the 10-sec ramp times to both safe.snap and observe.snap.
• Turn servo gains to 1

Then all PSAMS servos were fine. Camilla re-adjusted the ZM2,4,5 osems alignments to set alignment back to yesterday 84593.

I haven't had time to post this because of the wind fence work, but I haven't been able to finish the commissioning of the HAM1 ISI because of a 70-ish hz feature in mostly the X and RZ plants. I didn't see or appreciate how large this 70hz feature was in my close out measurements before doors went on, and it's making the loop design very difficult. I was trying to notch the loops to make the ISI work, but 70hz is very close to the nominal 30hz loop ugf. The X,Y,RZ and Z loops are marginally stable right now, and the  70hz feature gets injected into the IMC when ALS is locked. I think that I can get the loops working, but probably with less gain than we would otherwise get.

Attached PDFs are the loops currently installed, the ISI is set to not use the RX and RY loops, but the X loop is probably ringing at 70hz when the ISI is isolated. We are currently running with just the damping loops though.

Georgia, Kevin, Camilla

Julia and I turned on the SQZ laser, PMC locked fine but the SHG PZT was railed high, Daniel needed to reduce H1:SQZ-SHG_SERVO_SLOWMON offset from 10V to 0V, it then locked fine too. I touched SHG polarizations to reduce SHG fiber rejected power.

Trended ZMs and FC1 top mass alignment. Adjusted ZM2P, ZM4P, ZM5P, FC1P and FC1Y as these were more than ~10urad from the last time in NLN. 

Started following last time we aligned Homodyne in 82153

Turned up SEED injected power from 0.7mW to 70mW.

We went out to SQZT7 and the beam was on the diodes adn there was fringing, we increased LO power to match SEED power using pico-waveplate. WE then adjusted the LO beam with SEED beam blocked to improve the subtraction: Checked we were centered on PDA/B using the steering mirrors downstream of the HD BS and then measured the HD DIFF spectrum. Adjusted BS, re centered on HD PDs and re-checked DIFF ndscope (spectrum of shot noise was noisy at low frequency, then repeated until we were close to zero on the DIFF channel.

Sheila, Elenna

I have commissioned the DC centering on the POP X WFS. This uses DC6 pitch and yaw. I made OLG measurements of both loops, setting them to have a UGF around 0.5 Hz. I had to add additional loop gain to get this UGF, similar to the REFL WFS centering.

Measurements saved in [userapps]/asc/h1/templates/DC_centering

Sheila is adding this centering loop to the ISC_DRMI guardian to engage when we lock DRMI.

We should probably also add "PM1 [P/Y] clear" buttons to the DC centering page.

I also edited the ISC_DRMI guardian to clear teh PM1 suspension when it goes to Down.

These alogs also contain relevant information regarding the PM1/DC6 control:84610, 84623, 84579

Georgia, Camilla, Kevin, Caroline, Julia

We did a few things to prepare for Kevin's ADF measurements. 

Refrencing the SQZT0 March 2024 Layout...

On SQZT0, we moved SHG Trans. camera back a few inches, we also noticed weird behavior with the camera: when the beam was on the camera it was black, but saturated when the beam wasn't on. 

We unblocked the LO path and aligned BS5 to get the beam on PD 1611. 

Camilla aligned the beam on on PZT 2 (used to control LO phase). 

We walked the beam with MR11 and XMR8 to maximize the power through the LO fiber. Going into the collimator, we had 7.3 mW. Coming out of the fiber after the collimator, we had 3.0 mW of power, then 1.9 mW out of the fiber going into the SQZT7 fiber patch. 

We then decided to clean the fiber tips, including those going into and out of the SQZT0 patch, and the fiber going into the SQZT7 patch, which didn't make a difference in the power. 

After adjusting the strain on the fiber, we had 1.45 mW of power out on SQT7.

We're now ready to set up the balanced homodyne using the SQZ LO independent of the PSL. 

J. Kissel, S. Dwyer

As opposed to the ''glitch'' I reported this morning (LHO:84622) which was while the IFO was configured in PRX and ISC loops created a large pitch excursion with M1 drive of the H1SUSBS. We're now seeing stuff that is much more "classic optical lever glitching" with the IFO configured in PRMI, with MICH ASC engaged. See attached. This is after Sheila/Camilla increased the current in the BS oplev laser this morning (LHO:84616)

As a reminder, Beam Splitter optical lever loops are only used in PRMI / DRMI until MICH ASC is turned on. The transition happens in the ISC_DRMI guardian, in the "ENGAGE_DRMI_ASC" (index 80) state; the gain in the ASC-MICH banks are ramped ON in 2 seconds, and the gain in SUS-BS_M2_OLDAMP banks are ramped off with a 20 sec ramp (i.e. it's not that the inputs or outputs are switched on or off).

So, beam splitter optical lever glitching had been particularly painful in the past few days when working in PRMI and/or DRMI without the corner ASC loops on. But, now that we've found a good alignment, and fixed the REFLAIR phase (LHO:84630) we're able to quickly transition to using DRMI ASC, and become insensitive to the optical lever performance -- which continues to glitch.

Following up on Jennie's PRCL OLG measurements yesterday, 84604, I checked the phasing of REFLAIR 45 (the MICH sensor) while PRMI was locked. I used a template in userapps/lsc/h1/templates/phase_REFLAIR.xml, but had to turn the PRM excitation down to 300 counts. 

THe first attachment shows that improving this phase improved the shape of the PRCL loop.  This has probably been not phased well for a while, not as a result of the vent. 

I also adjusted the phase of REFLAIR 9, SDFs attached.

Wed May 28 10:15:55 2025 INFO: Fill completed in 15min 51secs

Oli, Elenna

The DC1 and DC2 centering loops have seemed to be way too slow, so Oli and I took some transfer functions of the centering loops. We started with DC2 Y, and the loop didn't even seem to have a UGF. By looking at the phase, Oli and I determined that we could raise the loop gain to get a UGF of about 0.5 Hz with a phase margin of 38 degrees. This involved raising the gain from -0.1 to -8.

The DC1 and 2 yaw loops have the same design and feedback to the same suspensions, so we copied over the gain change and ran a quick OLG to confirm the result is the same.

DC1 and DC2 pitch also have the same design. The low pass filter in use in pitch cuts off at 0.7 Hz instead of 1.5 Hz like the yaw loops, so there was much less phase margin. Oli and I copied over the butterworth low pass at 1.5 Hz in the yaw loops to the pitch loops and found that raising the gain from -0.1 to -7 gave the desired 0.5 Hz UGF.

All four loops have been measured using the templates in [userapps]/asc/h1/templates/DC_centering and saved. I have attached screenshots of DC2 Y and DC1 P. We SDFed these changes.

We copied over the DC1/2 design to DC6 yesterday, so Oli and I also updated the low pass filter in DC6 P to match and SDFed. The gain of DC6 P and Y still needs to be checked.

As a final note, we lowered the bandwidth of these loops just before O4 to avoid noise reinjection into CHARD, so we should check how this higher bandwidth impacts the noise in CHARD at a later date.

J. Kissel, S. Dwyer, others

Just so others can see what we're seeing, here's the glitch at 2025-05-28 15:36 UTC that drove us to swap the F1/F2/F3/LF Triple Top coil driver on the H1SUSBS. 

Everything's wrapped in loops, so it's difficult to point fingers at any one component.
ISI is in FULLY_ISOLATED_NO_ST2_BOOST per normal for MICH lock acquisition
SUS has 
    - M1 OSEM PD to M1 OSEM Coil damping loops ON (L, T, V, R, P, Y)
    - M3 Oplev QPD to M2 OSEM Coil damping loops ON (P and Y)
The IFO was attempting to lock PRX.
This is unexpected, but apparently there's also some slow ISC loop that is really causing the majority of the alignment excursion.

Will keep investigating other times to see if this is a consistent issue. 
We've looked at a few other times where we suspect optical lever glitching, but the same ISC loops were not on.
Difficult to trend the configuration of the ISC loops at the moment, 'cause folks are trying lots of different configurations to get DRMI relocked.

We'll post if we find an answer.

We swapped the coil driver because the "glitch" showed up "most" in the F1 sensor, and we feared it was something like we've seen in the past -- SR3 top mass coil driver failures that took us a long time to find (see LHO:62038 and LHO:62123).

J. Kissel

As we begin to investigate transient issues with the Beam Splitter where its sensors are reporting intermittent glitching that is spoiling DRMI locking, the optical lever damping loops are always an open question for me. 

Here's the impulse response of the filters, shown both as a normal time-series, which shows that most of the action happens within the first 0.2 seconds. I also show a semilogx plot of the time series to show the early magnitude of the response.

Finally, I attach a screenshot of which filters are on.

Ryan S., Sheila, Elenna

First thing Wednesday morning: run full initial alignment with green cameras

Ryan and I were able to lock the IFO on DRMI after many hours struggling down rabbit holes. In short: we were able to finally lock DRMI after reverting the ITMX and ITMY alignment to the alignment on Friday, and running manual initial alignment.

Sheila came online while we were in DRMI checking various things, and together we made it to CARM on Resonance. The alignment was very good (mostly hand tuned except for MICH ASC and DHARD). Sheila and I did our usual check of the PRG following alog 62110 and confirmed that everything looks great.

From there, Ryan and I ran the green camera offset scripts, watched them converge, and set the camera values. These are all SDFed- Ryan will add screenshots. To reiterate: run full initial alignment!

Sheila will add comments about checking and fixing the REFL phases.

While Sheila was adjusting the REFL phases so we could go to CARM on analog, I tried setting up the POP X centering using PM1 (so we could do DRMI on POP). I confirmed that moving PM1 moves the beam on POPX in reasonable ways. I had to flip the DC centering sign to positive when I engaged the loop, DC6, so the centering would converge. I was trying to check the UGF of the DC6 pitch loop by adding an offset to the loop, and accidentally added a massive offset, which tripped a lockloss since the beam went crazy on POPX and therefore LSC POP and that's a lockloss trigger diode.

I also had to turn on the PM1 signal output from the ASC model, which I then SDFed. After lockloss, the PM1 locking output doesn't get cleared, so Sheila will add that to the list of suspensions to clear after lockloss.

Calibration is currently regenerating the O4b uncertainty budgets.

Due to a missed change to the ETMX UIM suspension filters, which was found in LHO alog 82804, and then fixed only on Feb 27, 2025 (see LHO alog 83088), we need to add a correction TF to be included in the uncertainty budgets.

I attach a graph of that correction TF (corrected model / original model) and the text file needed for that correction.

We will be using correction TF in all our uncertainty budgets for O4b, and up to Feb 27, 2025 around 20:00 UTC, or GPS 1424721618 for O4c.