TITLE: 09/26 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Wind
INCOMING OPERATOR: Ibrahim
SHIFT SUMMARY: Currently relocking and in LASER_NOISE_SUPPRESSION. One lockloss today due to the wind, and relocking has been taking a while because of the wind. We were worried about the ETMY Roll mode earlier, but it ended up coming back down on its own. Maybe we should keep an eye on it over the weekend, but it seemed like the current setting are doing okay. The ion pump is still running in the LVEA - since the lockloss was so late in the evening, there were no vacuum people on site to turn it off, but that's okay. 
LOG:

23:30 UTC Observing and Locked for over 11 hours
    00:22 GRB-Short E603710
02:27 Lockloss
    - ALSY needed help
    - Constant ALS locklosses because of high wind, so sitting in DOWN for a while

Lockloss at 2025-09-26 02:37 UTC after 14.5 locked due to high wind :( We were riding it out really well up until now 

Here is a summary of some results from the open loop gain measurements of DHARD Y and CHARD Y, and the implementation of a new CHARD P low pass:

DHARD Y

I measured the DHARD Y open loop gain, results shown here. The dark blue trace shows the original measurement, showing 17 degrees of phase margin and gain peaking of 10 dB. Looking at the loop design, there are three different boost filters applied to DHARD Y, compared here. These boosts in combination seem to be destroying all the phase of the loop. I took a measurement with the 0.9 Hz boost disengaged (FM3), which is shown in the green trace. Then, I disengaged the 0.5 Hz boost (FM4) and remeasured, shown in the red trace. This improved the phase margin to 32 degrees. This obviously resulted in less microseismic suppression. I adjusted the 0.5 Hz boost (FM4) and decided we should operate without the boost in FM3. This plot compares the original loop error signal and RMS with all three boosts (gold), the error signal and RMS without FM3 and FM4 boosts (green) and then error signal and RMS with the updated FM4 boost (red). The RMS increased 50% without both boosts on, the improved boost returns the RMS to that value. There is now more phase margin in the loop. Updated in guardian and ASC high gain script, SDFed (1,2).

CHARD Y

I measured the CHARD Y open loop gain, results shown here. The file had an old reference trace from 2023, shown in bluegreen in the reference. The gray trace shows the first measurement I made today of CHARD Y. The gain appeared to be way too low. I raised the gain to match the old reference, which was a gain increase of 6 dB. Here is a comparison of the RMS of CHARD Y from 14 hours ago (bluegreen reference) and now (red live). The microseism level is the same between these two measurements. Overall, this reduces the RMS of the loop, so I think this is a good adjustment. This is updated in the guardian and ASC high gain script, also SDFed.

CHARD P

I implemented a new CHARD P low pass filter to reduce CHARD P coupling that is apparent in coherence measurements (example).

Here is a comparison of the old controller (red) with the new controller (blue). This replaces the lowpass filter in FM8 with the filter in FM9. I also disengaged the old 200 Hz lowpass that was previously in FM10, as it wasn't doing much. SDFs (1,2). Guardian code and ASC high gain script updated.

The coherence of DARM with CHARD P has reduced, as expected, and increased for CHARD Y, also as expected. I have since created a new lowpass for CHARD Y that should reduce the coherence and is ready for testing at the next opportunity (comparison).

TITLE: 09/25 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Observing at 147Mpc
INCOMING OPERATOR: Oli
SHIFT SUMMARY: H1 has been locked the whole day so far; current lock stretch is up to almost 11.5 hours. The ETMY roll mode is slightly more rung up than it has been in the past few days, but maybe not egregiously so; Oli will keep an eye on it this evening. Other than commissioning time this morning, it's been a quiet shift.

• 15:30 - Dropped observing for calibration sweeps
• 16:00 - Calibration finished, starting commissioning
• 17:04 - GRB-Short E603626 (was not observing)
• 20:02 - Commissioning finished, resuming observing

LOG:

Today I adjusted the DHARD gain and asked Ryan to rerun the simulines measurements to see if changing the DHARD gain has any measureable effect on the sensing function. This tests possible L2A2L coupling present in the sensing function.

Based on recent OLGs of the HARD loops, I decided we could probably lower each gain by 3 dB. For DHARD P, this takes the gain from -30 to -18 and DHARD Y from -40 to -24.

We ran one simulines with DHARD P gain lowered and one with DHARD Y gain lowered. These measurements can be compared with this morning usual calibration measurement.

The results seem a bit inconclusive to me. There might be some change in the phase below 10 Hz. First I compare the three sensing measurements, then I take the ratio of each measurement with the "nominal settings" measurement.

TITLE: 09/25 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Observing at 150Mpc
OUTGOING OPERATOR: Ryan S
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 19mph Gusts, 14mph 3min avg
    Primary useism: 0.06 μm/s
    Secondary useism: 0.16 μm/s 
QUICK SUMMARY:

Observing at 150 Mpc and have been Locked for almost 11 hours. Wind has increased recently, but shouldn't get too bad. ETMY roll mode has been slowly increasing over the past ~few hours, so I'll be keeping an eye on it.

Since maintenance will start early next Tuesday, I've updated the PEM_MAG_INJ node to start its injections at 6:00am (13:00 UTC) and the SUS_CHARGE node will start at 6:25am (13:25 UTC). These should all be finished by 6:45am (13:45 UTC).

I don't have time to analyze these for now, so I'm just dumping the pictures here.

On Tuesday Sep/23 RyanS and I went to the PSL room to do two things.

• Measure the beam size downstream of the bottom periscope mirror with two different settings. Wincam was put at the same place as the measurement on Sept/15 (alog 86949).
  • The new nominal setting where PMC receives the full power but EOM receives the reduced power (PSL-PWR_PMC_TRANS~103W, IMC-PWR_EOM~86.6W or so, and IMC-PWR_IN=2W at the time of measurement). See the 1st photo. Note that IMC-PWR_EOM calibration is known to be bad, it's only useful for making the ratio of two power levels.
  • PMC power is reduced but the EOM receives the same power as the nominal setting (PSL-PWR_PMC_TRANS~77W, IMC-PWR_EOM~86.6W or so, and IMC-PWR_IN=2W at the time of measurement). See the 2nd photo.
• Look through the EOM with a help of green flashlight to see if there's something apparently wrong, which we didn't find though we found some specks which might be far from the beam.
  • We put a 45 degree mirror on the PSL table right after the EOM and look through the EOM (i.e. the camera is downstream of EOM, looking into upstream direction). In the third photo (DSC_0776.jpg) the focus is on the output aperture of the EOM. As I shifted focus closer towards PMC, somewhere close to the input face of the crystal, two specks (maybe one is the ghost image of the other?) became visible. See DSC_0778.jpg.
  • We also tried to see the EOM from the input aperture side, which was not at all productive due to tight space. DSC_0782.jpg was the best view we got but we still couldn't even see the entire front surface of the crystal.
  • We also tested hand-holding a USB microscope but was hopeless. It might have been better with some kind of rigid structure to rest a hand/microscope on (but the space is very tight).

Yesterday I went into the optics lab and re-measured the coupling between input beam motion and PD array. While taking measurements I noticed that the injection could not be seen on the AC readouts of the PDs (example) so I tuned the temperature of the laser via changing the resistance of the controller, I went from ~10kOhms up to 13 kOHms and down to 8kOhms and while I found places where the noise reduced see example of noisy trace here, I couldn't find anywhere with the controller where the trace renamed stably in the non-noisy state. I then decided to tune the pump current down from 130mA to ~100mA and eventually found a somewhat stable place. I still had to wait through some periods of noise to trigger the measurement of the PDs.

I alos increased the modulation ampltitude to 80 mVpp. The counts on the QPD LCD readout were 10672, see image.

When the laser is in its quiet state the AC PD traces should comfortably fit on the screen of the osclloscopes with a 5mV scale, with the laser noisy this is more like 100mV, I also use 100mV scale for the QPD, I didn't change it when I reduced the noise on the laser.

The noisy state for the QPD outputs is here, the quiet state is here.

For each measurement I used a capture range of 400ms on the time axis of the scope and 125 000 samples selected on the 'ACQUIRE' menu.

The final measurements are:

PD 1 - 4 measured at AC: T0012ALL.CSV

PD 5 - 8 measured at AC: T0014ALL.CSV

QPD X, Y and SUM channels measured at AC: T0013ALL.CSV

The two DC measurements are going to be averaged so I didn't wait for a quiet time to measure them.

PD 1 - 4 measured at DC: T0011ALL.CSV 

PD 5 - 8 measured at DC: T0010ALL.CSV

To save you need to click on the menu button and change the resolution to be'Full', the format to be CSV and the channels captured to be 'ALL', the file number will roll over every time you save so you don't need to enter it manually.

Thu Sep 25 10:09:27 2025 INFO: Fill completed in 9min 23secs

In 87071, we found that the low frequency SQZ noise could be removed by changing the ZM4 or ZM5 PSAMs and we left the ZM4 PSAMs at 6.2V strain (from 6.0V). 

Today I went back to the noisy area at 6.0V and lower on ZM4 and saw no increase in low frequency noise, plot attached. I did not try going higher than 6.2V yet, we could do that as 6.5V caused noise on Monday too. 

It is not surprising that this noise couldn't be re-created as it was coming and going in the past. 

Following the procedure in the TakingCalibrationMeasurements wiki, at 15:30 UTC H1 dropped observing for the usual calibration sweeps.

Broadband - 15:30:52 to 15:36:02 UTC

Simulines - 15:36:37 to 16:00:00 UTC

Calibration monitor screenshot and calibration report attached.

File written out to: /ligo/groups/cal/H1/measurements/DARMOLG_SS/DARMOLG_SS_20250925T153638Z.hdf5
File written out to: /ligo/groups/cal/H1/measurements/PCALY2DARM_SS/PCALY2DARM_SS_20250925T153638Z.hdf5
File written out to: /ligo/groups/cal/H1/measurements/SUSETMX_L1_SS/SUSETMX_L1_SS_20250925T153638Z.hdf5
File written out to: /ligo/groups/cal/H1/measurements/SUSETMX_L2_SS/SUSETMX_L2_SS_20250925T153638Z.hdf5
File written out to: /ligo/groups/cal/H1/measurements/SUSETMX_L3_SS/SUSETMX_L3_SS_20250925T153638Z.hdf5

TITLE: 09/25 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Observing at 154Mpc
OUTGOING OPERATOR: Tony
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 5mph Gusts, 3mph 3min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.16 μm/s 
QUICK SUMMARY: H1 has been locked for 2.5 hours. Looks like the lockloss last night was from yet another earthquake, this time likely a M5.7 from Mexico. Calibration and commissioning time scheduled today from 15:30 to 20:00 UTC.

• Wind low, ground motion calm now after a night of quakes
• All other systems nominal

TITLE: 09/25 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Earthquake
INCOMING OPERATOR: Tony
SHIFT SUMMARY:

IFO is in LOCKING in LOCKING_ARMS_GREEN

Very calm shift with a fully auto Lock acquisition from the M6.1 Venezuela EQ this afternoon (alog 87128).

We had one Lockloss due to another earthquake from Venezuela, M6.3. Lockloss alog 87134. I turned on the ASC High Gain before it happened, but we understandably still lost lock.

I've just set IFO to auto-lock, which it will do once the EQ rings down (I expect it to take another 30 mins to get to a lockable state).

LOG:

Lockloss due to another EQ from Venezuela - 6.3 Magnitude

I previously reported results from DARM offset step tests in October and last week. The overall goal here is to figure out what overall effect the power outage has had on the IFO, especially since we have lost 1% optical gain. For example, see this alog about comparing modulation depth tests.

However, after looking closer at the DARM offset measurement results, and especially investigating the effect of whether leaving the OMC ASC on during the measurement matters, I would like to revise the previously reported measurement results.

Some background: this test aims to measure the contrast defect light by changing the DARM offset in mA while injecting strong PCAL lines to capture the DARM optical gain. We expect the relationship between optical gain (mW/pm) and DARM offset power (mW) to be quadratic. We assume by fitting the data to a parabola, the resulting y-intercept can tell us the contrast defect light on the DCPDs, if we had zero DARM offset.

Some considerations:

First question, does leaving the OMC ASC on matter? Jennie has been doing a lot of these measurements, and her experience has been, yes, because the OMC ASC offsets are set at one DARM offset and are not reset at each different offset. We do not expect the OMC alignment to drift significantly during the 15 minutes of this measurement, so the best practice has been to turn the OMC ASC OFF for the measurement. However, I didn't do it the first time I measured last week, but I got significantly better results (using Craig's code) with the ASC ON than I did with the ASC OFF.

Second question, what is the best way to fit this data? This apparently has been a question for a long time, see Gabriele's comment to 30573 in 2016. I believe the model I described above suggests that the vertex of the resulting parabola should be centered around x=0, that is zero optical gain. However, I discovered this week that Craig's code, which I used to report the results in October and last week (see first two links), fits a nonzero vertex (i.e. y = a(x-x0)^2 + b instead of y = ax^2 + b). Of course, that will change the answer significantly! I don't understand the mechanism that would cause us to move the center of this vertex away from x=0, so I refitting the data to follow y = ax^2 + b.

Results:

I am revising the fitted contrast defects to be:

Conclusions:

This measurement shows that the contrast defect is higher now than it was in October. I don't know if we can attribute all of this to the power outage; we lost 1% optical gain comparing kappa c from before and after the vent, giving us at least 2% less optical gain between October and now. It also shows that there is perhaps a small effect related to the OMC ASC being off: slightly higher contrast and a better overall fit.

This also increases our upper limit on the possible homodyne angle- in October I stated that the homodyne angle upper limit would be about 7 degrees, but with this revised value it should have been more like 8.8 degrees. Now it is 9.3 degrees.

During Tuesday maintenance, we swapped the HAM6 AIP (Starcell). Note this annulus system is connected to HAM5 via the septum plate. We vented the lines with dry nitrogen and left a continuous nitrogen purge(~.3 psi) of the line during the pump swap. Nitrogen attached to HAM5 pump out port while HAM6 pump out port was left open to atmosphere.

No issues during the swap, annulus system is now pumping at both HAM5 & 6 ports with an aux cart and turbo pair. As of end of maintenance, the HAM6 cart was at ~3E-5 Torr, HAM5 cart at ~1E-4 Torr. These pumps will continue running until pressure is <1E-5 Torr at which point the ion pumps will be powered on.

Carts are placed on foam for isolation, and a piece of foam between the flex hose running up to HAM6 pump out port and HAM6 chamber. See attached pictures. 

Work permit will be closed once pumps are disconnected from chambers.

Elenna Capote, Camilla Compton, Sheila Dwyer, Derek Davis

This afternoon we had a repeat of the bad low frequency noise that we have been suspecting was from filter cavity backscatter 86596.  We saw that the symptom of elevated noise in the filter cavity error signal was similar to previous incidents plot. 

We compared squeezing with and without the filter cavity, and no squeezing, and see that this noise is there when squeezing is injected no matter what the filter cavity state is.  plot and plot with mean sqz and anti squeezing. 

We repeated the fringe wrapping measurements, we saw a higher scattered amplitude when moving ZM5 than last week. (shelf is higher by 10dB). the ZM2 shelf is about the same. plot

We also did some 30 Hz excitations in ZM5 + ZM2, we can see a bilinear coupling of these but the background didn't change during this excitation. plot

Derek and Elenna looked at the glitches in DARM that showed up at the time of the noise.  Derek ran some hveto runs for times with frequency dependent squeezing and frequecy independent squeezing, and saw that filter cavity length signals are a good witness when the filter cavity is locked, when the filter cavity is not locked the giltches stay but aren't witnessed by the FC error signal. 

Camilla found that she could reproduceably make the noise go away by moving the ZM4 +5 PSAMs small amounts.  She moved the PSAMs and adjusted the alignment to get a good level of high frequency squeezing back.  She also tried to do this with alignment only.