I ran an iterative tuning of the LSC feedforward today. The feedforward was already decent, but there was some room for improvement. The two attached screenshots compare injections from the new feedforward fit and the old fit. The only place to pay attention to moving forward is the high frequency coupling of SRCL, which may be effected by the large SRCL offset measured (and potentially corrected) today. If we see any >100 Hz noise coupling from the LSC, maybe we can do another iterative fit. I also injected in PRCL and the noise coupling has not changed, so the previous feedforward is just fine.

The new filters are in FM7 for both MICHFF and SRCLFF, and I updated the guardian.

TITLE: 06/04 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: Oli
SHIFT SUMMARY:

IFO is in NLN_CAL_MEAS and PLANNED ENGINEERING

Extremely productive day in which we got to Nominal Low Noise for the first time in two months!

Very briefly, here's what we did today:

• Discovered that the HAM1 ISI watchdog was tripped for 1 full day, contributing to DRMI instabilities in the last EVE
• Violins are looking okay and being actively damped by OPS and Fellows
• REFL rephasing was done to max SNR from Q into I.
• ADS optimized via A2L
• HAM1 Leak checks are ongoiong because it has been determined that the annulus gap between HAM1 door is probably leaking. Tomorrow, vacuum will go into the LVEA and find out which door it is (if possible).
• DC Centering issues fixed
• SQZ being worked on

Relevant alogs:

alog 84800: low range coherence checks

alog 84798: a2l optimized pre-NLN

alog 84796: IM4 and MC2 TRANS

There are undoubtedly more in-progress alogs about work done today.

LOG:

TITLE: 06/04 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Planned Engineering
OUTGOING OPERATOR: Ibrahim
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 19mph Gusts, 10mph 3min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.14 μm/s
QUICK SUMMARY:

Currently we are sitting in NOMINAL_LOW_NOISE and people are working on measuring and updating various things.

Ibrahim

Ran a low range coherence check to better understand H1 range and its effects right before NLN. Screenshot of result attached.

Camilla, Ibrahim

Ran A2L before NLN to maxmimize range.

We had to run the a2l script a few times for all QUADs. The first two times, there was no change in gain because the required change vin gain was too much for the script to apply (a safety feature I'm sure). Camilla and I then stepped the gain in the right direction until we were sure that it would be within the adjustability of the script. It took two more runs in order to finally get the range maximized. This improved the range by about 20 MPc. Screenshots attached (the screenshot named initial is before manual stepping).

M. Todd, C. Cahillane

We are looking at the RIN in LSC-REFL_A to try and understand if there are some cavity dynamics that can give an estimate of the power recycling cavity mode-matching to the arms (for some more background, see Daniel's alog 70985)

I've made a plot that shows some interesting changes in the REFL_RIN asd as a function of thermal state. In particular I've looked at the asd at 4 different times as we thermalize after locking and stabilize the ISS.

There's some very interesting dynamics around 5-50 Hz. For the HF dynamics, I've also plotted the shot-noise limit based on that time's DC REFL_A_LF power; which I think is the limit in that frequency regime.

I've put both the dtt plot as well as my own plot that used quick_psd.

Next, I would like to model what RIN we would expect in that frequency band and compare to these measurements, specifically if this is intensity noise coupling changes due to mode mismatch changes during thermalization.

Looking at IM4 and MC2 trans, we see that the amount of power on MC2_TRANS and IM4_TRANS has decreased by around 1%.
The plot shows a time in March 12, 2025, with white dashed lines where those values are now on June 04, 2025.
The IM4_TRANS calibration was fixed after the HAM1 work in alog 82260.

The PRG is around 3% higher now, going from 52.2 to 53.9.
The PRG calculation already incorporates this apparent 1% fall in IM4_TRANS.
Matt Todd checked the PRG at 2W in alog 84668.

As far as alignment, MC2_TRANS is servoed to zero by the input PZT using IMC ASC DOF3, so that is "unchanged".
IM4_TRANS has drifted only a small amount, from 0.1 to 0.2 in PITCH, and -0.04 to -0.10 in YAW.

This is all loosely consistent with the small changes in input pointing we've seen in the ISS array pointing seen in alog 84728.
Keita noticed that the SEG3 on the ISS QPD is totally saturated at -32768 cts due to the misalignment onto that PD, so it becomes even harder to trust the ISS QPD reference.

We have not yet closed the ISS secondloop as a part of the locking sequence, so we don't know if the beam jitter coupling to DARM problem will get worse when we close this loop.
I reckon there is a very high likelihood that it will.

Keita had more suggestions, including
1) injecting into the IMC and checking coherence between IMC WFS and the ISS array and DARM (Mr. Todd has already started this analysis alog 84775).
2) moving the input pointing into the array in PITCH and YAW and checking the PHASE between each individual array diode, maybe via line injection, to see if there is any cancellation happening, or if some diodes are more susceptible to misalignments
3) far future: change around plugs for INNER and OUTER so that the INNER diodes are the most stable, best-aligned ones.  This could improve our overall beam jitter coupling, if we think it's coupling via the intensity loop.

WP12583

At 15:54 Tue 03jun2025 PDT the EX HWWD showed activity. This was repeated later in the day between 18:40 - 19:10. This could mean I don't need to go to EX to perform a cable-out test.

Attached 10 week trend shows when the various HWWDs went quiet and later resumed activity.

TJ, Dave:

The ADJUST_POWER state of the ISC_LOCK guardian node has been exercised recently during locking, with the unexpected consequence of various CDS system mis-interpreting this as entering/leaving nominal-low-noise. This is because this state's number is 1000, greater than NLN=600. For example, attachment shows CDS overview screen mistakingly showing models' SDF diffs in RED. Yesterday TJ reduced this state's number to 521, a number which wasn't available when this state was first created but has since become available (graph snippet shown).

Wed Jun 04 10:10:09 2025 INFO: Fill completed in 10min 5secs

Gerardo confirmed a good fill curbside.

TITLE: 06/04 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
OUTGOING OPERATOR: TJ
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 11mph Gusts, 6mph 3min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.15 μm/s
QUICK SUMMARY:

IFO is in DOWN and PLANNED ENGINEERING

Plan today is to continue lock acquisition. Might attempt an initial alignment whilst the comissioners arrive.

Oli, Georgia, Elenna

While we were taking care of several LSC items, Georgia pointed out that we are seeing the 0.8 Hz buzzing in INP1 yaw again, and to a lesser degree CHARD Y. While we did several useless things to debug, I noticed that the DC centering loops were also buzzing with the same frequency oscillation. I decided to try changing the DC centering loop gain (since I had raised the loop gain significantly last week), and noticed that NONE of the DC6 pitch or yaw filters were engaged, but a gain of 1 was engaged, essentially feeding the input signal right back to PM1. Bad!!

Searchingh DC6 in the guardian shows that in PREP_ASC_FOR_FULL_IFO, I found these lines of code:

Not good! Since the gain of DC6 is set on, this effectively keeps the gain on but turns off all the filters and just feeds back the pure error signal to the suspension.

I commented those lines out of the guardian and loaded, and then reengaged all the proper filters. A large 28 Hz line that had been present in DARM disappeared at this point, likely because the DC centering loops require a 28 Hz notch to avoid some suspension mode.

After this, I then tried turning down the DC1 and DC2 pitch and yaw gains to -1. This seemed to help the buzzing in CHARD and INP1. Georgia and I were able to engage all the low noise ASC settings without any issues (CHARD P had been held in high bandwidth to avoid a ring up and the soft loops had high gain for the same reason).

We need to monitor for a while longer and also try relocking, but these changes may fix many of our ASC issues.

I have SDFed these gain changes.

Daniel, Kevin, (Erik, Dave), Vicky

Kevin is interested in taking ADF sweeps around the second higher order mode arm resonance near 10.4 kHz.

We (Daniel) made model changes in h1ioplsc0 and h1omcpi that should enable higher freq ADF demods. Daniel built the models successfully. Then Dave also built these models successfully for the custom RCG running on h1omcpi for the variable duotone. We put in a WP to boot in these changes to h1ioplsc0 and h1omcpi next Tuesday 6/10.

From h1ioplsc0, we added 2 new PCIe channels to write the digital ADF LO oscillator out to PCIe. These are H1:IOP-PCI_ADF_VCXO_{COS,SIN} in screenshot 1. We also changed a rogue limiter such that the ADF should be able to scan +/-1 MHz according to the PLL.

In h1omcpi, we use the fast 64 kHz OMC PI user model to do a fast digital demodulation of the OMC_DCPD_SUM signal using the above ADF-LO PCIe channels. This is beating the fast dcpd output signal (H1:OMC-PI_DCPD_64KHZ_AHF), against the ADF LO's cosine and sine components from PCIe (H1:IOP-PCI_ADF_VCXO_{COS,SIN}), to get the demodulated ADF I/Q signals. The demod signals will have names like H1:OMC-PI_ADF_DEMOD_{I,Q}. Screenshots 2-4.

Operationally nothing should change for the ADF or for OMC-based fast PI damping. We are just using PCI to send 2 IPC channels from an IOP model to a user model on a different computer at ~65kHz, and doing the demod in a 64kHz user model (but the demod does not go anywhere, it is just used for squeezer diagnostics).

M. Todd, C. Cahillane, S. Dwyer

I ran another estimate of the PRG, following Craig's method in alog  58327, and estimate it to be around 54.2 W/W.

I compared the TRX power to Input Power ratio during the FIND_IR state versus the PREP_ASC_FOR_FULL_IFO state, with the PRM transmission as a normalization factor.

                       TRX_POWER_FULL_IFO  /  INPUT_POWER_FULL_IFO
PRG   =    -------------------------------------------------------------------------------------
                     TRX_POWER_FIND_IR   /  (Tp  * INPUT_POWER_FIND_IR)

I've attached the quick script I've used for the interesed reader.