IMC LSC/ASC Comparison from Satellite Amplifier Swap

Satellite amplifiers for MC1 and MC3 were swapped during maintenance (15:00-19:00 UTC) on July 22, 2025 (85922), and MC2 satamp had been swapped before that (85770). I wanted to see if we could determine any improvement in noise in the LSC and ASC input mode cleaner channels.

LSC Channel: 
    - H1:IMC-L_OUT_DQ
ASC Channels:
    - H1:IMC-MC2_TRANS_PIT_OUT_DQ
    - H1:IMC-MC2_TRANS_YAW_OUT_DQ
    - H1:IMC-WFS_A_DC_PIT_OUT_DQ
    - H1:IMC-WFS_A_DC_YAW_OUT_DQ
    - H1:IMC-WFS_B_DC_PIT_OUT_DQ
    - H1:IMC-WFS_B_DC_YAW_OUT_DQ
    - H1:IMC-WFS_A_I_PIT_OUT_DQ
    - H1:IMC-WFS_A_Q_PIT_OUT_DQ
    - H1:IMC-WFS_A_I_YAW_OUT_DQ
    - H1:IMC-WFS_A_Q_YAW_OUT_DQ
    - H1:IMC-WFS_B_I_PIT_OUT_DQ
    - H1:IMC-WFS_B_Q_PIT_OUT_DQ
    - H1:IMC-WFS_B_I_YAW_OUT_DQ
    - H1:IMC-WFS_B_Q_YAW_OUT_DQ

I looked at many times before and after these swaps looking for the lowest noise for each to be the best representative of the noise level we can achieve, and have settled on a set of before and after times that differ depending on the channel.
BEFORE:
2025-06-18 09:10 UTC (DARK RED)
2025-07-07 09:37 UTC (DARK BLUE)
AFTER:
2025-08-01 07:05 UTC (GREEN)
2025-08-01 10:15 UTC (PINK)
2025-08-02 08:38 UTC (SEA GREEN)
2025-09-05 05:23 UTC (ORANGE)
These measurements were taken for 47 averages with a 0.01 BW.

Results:

Channel	Comments
H1:IMC-L_OUT_DQ	Here the best 'after swap' time that I was able to find is noticeably worse than the best before time, so either the swap made the LSC noise worse, or we just haven't been able to reach that level of lowest noise again since the swap.
H1:IMC-MC2_TRANS_PIT_OUT_DQ	Small noise drop between 0.8-3 Hz
H1:IMC-MC2_TRANS_YAW_OUT_DQ	Slight noise drop between 0.6-3 Hz?
H1:IMC-WFS_A_DC_PIT_OUT_DQ	Looks about the same as before, maybe a bit of improvement between 7-9.5 Hz
H1:IMC-WFS_A_DC_YAW_OUT_DQ	Noise between 6-10 Hz has dropped slightly
H1:IMC-WFS_B_DC_PIT_OUT_DQ	No difference
H1:IMC-WFS_B_DC_YAW_OUT_DQ	No difference
H1:IMC-WFS_A_I_PIT_OUT_DQ	Looks like the noise above 1 Hz has dropped slightly
H1:IMC-WFS_A_Q_PIT_OUT	No difference
H1:IMC-WFS_A_I_YAW_OUT	No difference
H1:IMC-WFS_A_Q_YAW_OUT	No difference
H1:IMC-WFS_B_I_PIT_OUT	Looks about the same as before, maybe a bit of improvement between 7-9.5 Hz. Showing the sea green AFTER trace to verify that the pink AFTER bump seen at 10 Hz is not an issue caused by the satamp swap.
H1:IMC-WFS_B_Q_PIT_OUT	Looks about the same as before, maybe a bit of improvement between 7-9.5 Hz. Showing the sea green AFTER trace to verify that the pink AFTER bump seen at 10 Hz is not an issue caused by the satamp swap.
H1:IMC-WFS_B_I_YAW_OUT	Looks about the same as before, maybe a bit of improvement between 7-9.5 Hz
H1:IMC-WFS_B_Q_YAW_OUT	Looks about the same as before, maybe a bit of improvement between 7-9.5 Hz

The plots from LHO:86253 show the before vs. after M1 OSEM noise performance for 
    MC1
    MC2, and
    MC3.

Comparing the page 3 summaries of each of these .pdfs show that 
    - We only expect change between ~0.2 and ~8 Hz. So, any improvement seen in the 7 to 9.5 Hz region is very likely *not* related to the sat amp whitening change.
    - For MC2, the LF and RT OSEM degrees of freedom --  both the before and after traces show that L and Y are well above the expected noise floor below for the entire region below 10 Hz.
    - The change all DOFs is a broadband change in noise performance; not only is there nothing *sensed* by these OSEMs above ~5 Hz, but there's also no change and thus any resonance-like features that change in the IMC signals will not be related to the sat amp whitening filter change.

We should confirm that the data used for the MC2 "before vs after" were both taken with the IMC length control OFF (i.e. the IMC was OFFLINE).

Back to the IMC metrics -- 
    (1) Only IMC-L and the MC TRANS signals appear to be dominated by residual seismic / suspension noise below 10 Hz. Hence
        (a) I believe the improvement shown in the MC TRANS QPD, tho I would have expected more.
        (b) I believe that we're seeing something that is limited by seismic / suspension noise in IMC-L, but the fact that got worse doesn't agree with the top-mass OSEM's stated improvement from LHO:86253, so I suspect the story is more complicated.
    (2) it's clear that all of the DC "QPD" signals from the IMC WFS are not reading out anything seismically related below 10 Hz. Maybe this ASD shape is a function of the beam position? Maybe the real signal is drown out by ADC noise, i.e. the signal is only well-whitened above 10 Hz? Whatever it is, it's drowning out the improvements that we might have expected to see -- we don't see *any* of the typical residual seismic / suspension noise features.
    (3) WFS B RF signals appear to also be swamped by this same color of noise. WFS A RF signals show a similar color, but it's less in magnitude, so you see some residual seismic / suspension peaks popping up above it. But it's not low enough to show where we might expect the improvements -- the troughs between resonances. So given the quality of this metric, I'm not mad that we didn't see an improvement.

So -- again -- I really only think that metrics (1), i.e. IMC-L and MC2 TRANS are showing noise that is/was dominated by residual seismic / suspension noise below 10 Hz, so that's why we see no change in the IMC WFS signals; not because we didn't make an improvement in what they're *supposed* to be measuring.

We'll have to figure out what happened with IMC-L between June and Sep 2025, but the plethora of new high-Q (both "mechanical" and "digital") features between 3 and 10 Hz suggests that it's got nothing to do with the sat amp whitening improvement. The slope of increased broadband noise between 1 to 3 Hz doesn't match what we would  expect, nor does it match the demonstrated improvement in the local M1 OSEM sensors. We should check the DC signal levels, or change the window type, to be sure this isn't spectral leakage. 

Range drop during this lock

Our range hasn't been the most stable during this lock. There's one drop in particular that goes down about 8Mpc to 145Mpc for 20min or so (attachment 1). Running our range comparison script, and changing the span appropriately (thanks Oli!), it looks to be a very broadband from ~40-200Hz. The SQZ BLRMS see something around that time (attachment 2).

Sheila had me run another template for that time. The template, which was copied from one of Camilla's, I've now saved in the sqz userapps - attachment 3. Green being the trace from this lock.

Wed CP1 Fill

Wed Sep 10 10:07:21 2025 INFO: Fill completed in 7min 17secs

Gerardo confirmed a good fill curbside.

Ops Day Shift Start

TITLE: 09/10 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Observing at 152Mpc
OUTGOING OPERATOR: Corey
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 10mph Gusts, 6mph 3min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.11 μm/s
QUICK SUMMARY: Locked for 5.5 hours, automated relock. Calm environment. Some dust alarms at the LAB1 station in the night, odd.

Plan for today is to observe.

Tuesday Ops Eve Shift End report.

TITLE: 09/10 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Observing at 154Mpc
INCOMING OPERATOR: Corey
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 14mph Gusts, 10mph 3min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.09 μm/s
SHIFT SUMMARY:
Only thing note worthy was a possible Superevent candidate : S250910b @ 00:07:52 UTC.

I didn't really hear any thunder either.

LOG:
No log

 

Tuesday Ops Eve Shift Start

TITLE: 09/09 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Observing at 154Mpc
OUTGOING OPERATOR: TJ
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 9mph Gusts, 4mph 3min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.08 μm/s
QUICK SUMMARY:
H1 has been locked for 2.75 hours.
All subsystems seem to be running smoothly.
The weather report suggests that there may be thunderstorms soon.

 

Ops Day Shift End

TITLE: 09/09 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Observing at 154Mpc
INCOMING OPERATOR: Tony
SHIFT SUMMARY: It was a pretty standard maintenance day with a few aftershocks from the oregon earthquake to slow down the reacquisition. Observing for 2.75hours.
LOG:

• 0820 Lock loss, lots of maintenance activities.
• 1843 Started initial alignment
  • Lost lock a few times on the way up due to more aftershocks from the Oregon quake.
  • Elenna touched up POP90 via PRM after DRMI to help inscrease our chances of surviving.
  • Just after power up there was an odd ring up that started in ASC. MICH P error clearly saw it, as well as CSOFT P. After about 1.5min of making us nervous in the control room, it turned around and started to relax back to normal values.
• 2047 Observing

Start Time	System	Name	Location	Lazer_Haz	Task	Time End
14:44	SYS	Betsy	Opt Lab	n	In and out of lab for stuffs, quick into the LVEA for more parts	16:35
14:47	CEBEX	Bubba, contractors	MY	n	Drilling and surveying	22:41
15:00	SYS	Randy	OSB	n	Forklifting to mech room	15:22
15:00	FAC	Kim	EX	n	Tech clean	16:02
15:00	FAC	Nelly	EY	n	Tech clean	15:49
15:08	VAC	Jordan, Gerardo, Anna	LVEA	n	NEG pump regen, GV checks, valve in NEG	17:58
15:10	FAC	Chris	site	n	Forklifting from staging to woodshop area	17:00
15:15	CDS	Fil	LVEA	n	Cable trays near HAM5 with Ken & Drilling with Randy	18:54
15:15	FAC	Ken	LVEA	n	LVEA light replacement	18:49
15:22	FAC	Christina	VPW	n	Fork lifting	15:42
15:22	SYS	Randy	LVEA	n	W & E bay craning	17:22
15:30	SYS	Mitchell	LVEA	n	Grabbing parts	15:50
15:43	OPS	Richard	LVEA	n	Checking on things	16:03
15:47	VAC	Janos	MX, MY	n	Pump install work continuing	18:55
15:49	FAC	Nelly, Kim	FCES	N	Tech clean	16:55
15:58	GRD	TJ	CR	n	h1guardian1 reboot	16:07
16:38	PEM	Sam, Jonathan (student)	LVEA	n	Tour/ looking at PEM things	17:34
16:50	ISC	Daniel	LVEA	n	OMC whitening chassis removal	17:16
16:51	FAC	Mitchell	Mid X	N	moving pelican cases	17:38
16:51	TSC	TJ	Mech rm -> LVEA	N	Folling chiller lines	17:32
16:55	safety	McCarthy	LVEA	N	Checking on the LVEA safety	17:42
16:56	FAC	Kim & Nelly	High bay & LVEA	N	Technical cleaning garbing supplies	18:34
17:07	SUS	Ryan C	Crtl Rm	N	ETMX OPLEV SUS charge measurements	18:41
17:27	OPT	Camilla	LVEA, OpticsLab	n	Looking for parts	18:04
17:39	PCAL	Tony, Mitchell	PCAL Lab	-	Looking for parts	17:53
17:52	SYS	Randy	EY	n	Check in receiving	18:17
17:54	CDS	Marc	LVEA	n	Check in with Fil	18:04
18:18	SYS	Randy	LVEA	n	Take some measurements	18:34
18:32	-	Richard, student	OSB roof	n	Roof tour	18:47
18:42	VAC	Jordan, Anna, Gerardo	LVEA	n	Shut down NEG pump	19:14
18:51	-	Oli	LVEA	n	Sweep	18:58
19:09	FAC	Tyler	MY	n	Checking with crew down there	21:11
19:51	-	Fil, Betsy	LVEA	n	Measure something	20:11
21:47	SPI	Jeff	OpticsLab	n	Figuring out what is in the bag	21:59

The correlated noise in O4b is different than O4c

I processed one hour of no-squeezing data taken in November 2024 (81468) for the purpose of running a correlated noise budget. This data was taken shortly after noise budget injections were run (80596), so I was able to use the measurement of the jitter noise to perform jitter subtraction from 100-1000 Hz, similar to my work in 85899.

I followed the same procedure as I documented in 85899: I plotted the whitened time series and saw two glitches, which I excised from the data by removing the individual segments with the glitches. I then mean-averaged the remaining segments. As a part of the correlated noise data collection in Nov 2024, we took a full calibration measurement, which I was able to use to generate a model to calibrate the DCPD signals. I used the IMC WFS yaw signal as a witness to subtract jitter from 100-1000 Hz. I then calculated the full correlated noise estimate also as described in 85899 (in that log I called it the "full classical noise estimate", which I now realize is confusing).

The comparison of the Nov 2024 time (O4b) and June 2025 time is shown here.

The noise below 100 Hz is lower in June 2025, however the noise above 100 Hz is higher in June 2025. It also appears that the slope of the noise above 100 Hz has changed slightly. The high frequency noise is also different, possibly because the frequency noise coupling to DARM has changed.

I also plotted the ratio of the noise from 40-300 Hz, showing that the noise below 100 Hz is reduced by up to 10% in amplitude, and above 100 Hz increase by up to 10% in amplitude.

I added the GWINC thermal noise trace to the plot above, and took the ratio of the correlated noise to the total thermal noise to that trace to highlight the change in noise. The ratio shows that the overall slope and amplitude of the excess noise, compared to the full thermal noise trace, has changed.

And going back even further, the correlated noise budget was run in O4a in Dec 2023, which we used in the O4 detector paper. We only had 900 seconds of data, so the results are more noisy. Comparing the three traces and comparing their ratios to the GWINC thermal noise trace. I did not do a jitter subtraction on the Dec 2023 data. The nearest valid calibration report is on Oct 27, which is what I used to calibrate the data.

Observing 2047 UTC

Maintenenace recovery was fairly straight forward but there were a few more aftershocks from Oregon that caused us to lose lock while acquiring. We eventually made it up at 2047UTC, with violins very elevated. I'll work on damping those a bit faster that the automated settings.

HAM5 Cable Tray

A cable tray support was installed near HAM5.

F. Clara, R. McCarthy, Randy

Timeline of Monday night's watchdog activity due to Oregon M5.8 earthquake

Attached plot show trends of OSEM movements and subsequent watchdog activity.

Summary: we had three SWWD SEI trips (ETMY, ITMY, ITMX) followed by two SWWD SUS trips (ETMY, ITMY). We had one HWWD trip, ITMY.

Color code ETMY=BLUE, ITMY=RED, ITMX=GREEN, ETMX=GOLD.

Top panel: ETMY top stage 6 OSEMS

Second panel: ITMY top stage 6 OSEMS

Third panel: ITMX top stage 6 OSEMS

Fourth panel: ETMX top stage 6 OSEMS

Fifth panel: SWWD

Bottom panel: HWWD

Time Line (all times PDT Monday 8th September 2025)

(1) [21:11:44]: all four SWWD SEI timers start countdown

(2) [21:15:27]: ETMX goes good again (not shown, but ditto for ETMX HWWD)

(3) [21:16:42]: SWWD SEI trip, SEI IOP countdowns start, they trip in five minutes time

(4) [21:26:41]: ETMY SWWD SUS trip, its second timer is 10 minutes

(5) [21:31:54]: ITMY SWWD SUS trip, it has the original 15 minute timer, closely followed by:

(6) [21:32:29]: ITMY HWWD trip after its 20 minute countdown

(7) [21:38:14]: ITMY HWWD input goes good, ready for its reset button to be physically pushed

(8) [21:38:00]: ITMX SWWD SUS does not trip, it occasionally dips into the good region resetting the timer

(9) [21:42:00]: All SWWDs are reset, their inputs a good after the EQ has cleared

OSEM Satellite Amplifier Fundamentals: US8CH Sat Amps Have a different Overall Sign in Transimpedance than US or UK 4CH Sat Amps

J. Kissel

Continuing my low-level, background, fact building exercises on satellite amplifiers (the only previous installment thus far being LHO:85348) here I compare the three types of satellite amplifiers
    (a) D0900900 / D0901284 :: UK 4CH SatAmp 
    (b) D1002818 / D080276 :: US 8CH SatAmp 
    (c) D1900089 / D1900217 :: US 4CH SatAmp
again, but instead now comparing their transimpedance sign and frequency response. 

Namely, if the systems design intent was
    - the US 8CH SatAmp has been wired up to the OSEM in a POSITIVE reverse bias configuration, with ANODE (A) connected to the NEGATIVE terminal of the transimpedance opamp, and 
    - the US and UK 4CH SatAmps have been wired up to the OSEM in a NEGATIVE reverse bias configuration, with CATHODE (K) connected to the NEGATIVE terminal of the transimpedance opamp,
then these better have differently signed overall transimpendance in order to achieve the same sign at the ADC.

As such, I performed a similar frequency response measurement on an example instantiation of a D1002818 and D1900089 chasses as I've been doing for the UK 4 channel satamps -- see T080062 for the full procedure, and the "only" difference is the physical connection of the SR785 to the device under test. To describe that, I attach here a collection of diagrams of the physical setup for each chassis.

The results are clear: driving a POSITIVE voltage through a series resistor into the NEGATIVE input of the transimpedance op amp (i.e. mimicking the flow of PD current [conventional current, not electron flow] into the NEGATIVE input) results in a
    (a) NEGATIVE differential output voltage for a D0900900 UK 4CH chassis,
    (b) POSITIVE differential output voltage for a D1002818 US 8CH chassis,
    (c) NEGATIVE differential output voltage for a D1900089 US 4CH chassis.

Note, the NEGATIVE input to each chassis transimpedance amp is connected to across pages of the circuit diagram to connector pins labeled as 
    (a) K (CATHODE) for a D0900900 UK 4CH chassis,
    (b) A (ANODE) for a D1002818 US 8CH chassis,
    (c) K (CATHODE) for a D1900089 US 4CH chassis.
implying the correct outer-layer usage.

The second attachment shows the frequency response of the three chassis. Note all of the tested instantiations are pre-ECR E2400330 whitening filter change, so they all have the old z:p = ~0.4:10 Hz frequency response. The legend in the caption of the upper right panel shows the predicted z:p values from the schematic, and the data in the upper and lower right panels show that particular z:p divided out of the data to show how close these instantiations are to the ideal. Yes, the 8CH satamp frequency response is slightly different than the two 4CH responses; this will be rectified with ECR E2400330. The deviation of all three responses from ideal is consistent with the diversity of the instantiations of the UK 4CH sat amps, namely the uncertainty in whitening filter stage capacitance value (which should be a total of 20 [uF], but can vary up to 5%; see LHO:85396).

As such, when using these chassis, it is critical that the chassis-to-flange and in-vacuum wiring is connected in such a way that connects this NEGATIVE input to the right terminal of the OSEM PD.

For detailed breakdown of each stage of the sat amp frequency response and sign, to understand *why* and *how* they're different, check out G2500980.

LVEA Sweep

LVEA Swept and ready for Observing

ETMX OPLEV charge measurement

I was getting lots of overflows when I started the measurement, I tried lower the drive_amp by 20% and retrying. This didn't work, I went from the usual 11000 down to under 100 and still saw lots of overflows. Rahul suggested to halve the gain of the ESD output filters with the original 11000 drive_amp, from 1.0 to 0.5 and this stopped all the overflows during the measurements. I got a few thousand overflows when the script ended and was restoring settings though.

This measurement like previous recent ones (since the ESD bias voltage increase?) has very large errors, there wasn't any work going on at EX and the wind wasn't too bad, gusting up to 20mph.

Despite the huge error bars the charge generally seems lower than the last measument in most quadrants/dofs.

H1 ISI CPS Noise Spectra Check - Weekly (FAMIS #26656)

FAMIS Link:  26656

Only CPS channels which look higher at high frequencies (see attached) would be the following:

1. HAM3 H2
2. ITMx St1 V1
3. ITMy St1 H3 (noted below)
4. ITMy St1 V3

In the bash window we get this note:

"BSC high freq noise is elevated for these sensor(s)!!!:        ITMY_ST1_CPSINF_H3 "

Tue CP1 Fill

Tue Sep 09 10:06:51 2025 INFO: Fill completed in 6min 47secs

 

Remote Owl Wake Up 338amPDT

Got the wake up call at 338amPDT.  And literally while I was waking up and trying to remember what to do for the NOTIFY + MANAGER guardian nodes (I just "init-ed" both...is that the right thing?  that's what both of their User Messages said to do), I noticed that there was a Message that said there was an issue with the SQZ MANAGER.  

As I was getting ready to open up the SQZ guardians and assess (I'm pretty sure I spelled that right--I remember Hugh giving me grief for misspelling it in an alog before!), H1 was already back to OBSERVING.  I literally did nothing!  H1 was in OMC Whitening at 932utc, sent wake up call at 1037utc, and automatically went to Observing on its own at1043utc.  I'm going to go back to bed ASAP!  
 

Great job getting H1 thru all the environmental catastrophes at the end of your shift, Ibrahim! :)

Electrical storm power glitch rebooted h1susaux[h2,ex]. PSL is having problems.

After the watchdogs were reset a lightening strike caused a power glitch. GC UPS reported going into and off of battery power.

h1susauxh2 and h1susauxex went offline, turned out they were rebooting themselves and came back after a few minutes.

PSL is in a bad way, Ibrahim is calling for support.

The lights in my house flickered at the time I saw the sus-aux machines go down. We have been having a storm roll over us for the past hour, moving from Oregon northwards.