Supply Fan 1 at EX had faulty bearing(s) which was causing excessive noise. Macdonald Miller was on site this week to carry out the repairs. The work began Monday (5/6) and was completed Tuesday (5/7). The duration of the work was approximately the same on both days (8am-4:30pm) with brief lunch breaks around noon. All of the work was contained to the mechanical space of the end station. 

T. Guidry

Lockloss @ 18:35 UTC - link to online lockloss tool

No immediately obvious cause; ETMX saw the first erratic movement as usual.

Fri May 10 10:10:49 2024 INFO: Fill completed in 10min 45secs

Travis confirmed a good fill curbside. Note we are now in "summer mode" with TC-mins railing at -200C.

I made a quick plot of low noise % vs wind speed for O4a and thought it was interesting enough to share. This is by no means an analysis, just a quick look. Someone should probably do something similar to what Laurence and Sheila made for O3 for O4a (alog49682), but that someone is not me at the moment. Unlike on Figure 6 of Sheila's similar ER7 plot (T1500368), there isn't a clear drop off at a particular speed. This could be due to directional impacts and the wind fence, or a plethora of other factors. Figure 19 on this paper (<a href="https://dcc.ligo.org/DocDB/0150/P1800038/005/BRSLIGOCQG.pdf">P1800038</a> is again similar with O1 and O2 data, but in m/s. I'm very curious about looking around times of lock losses or failed acquisitions, but I'm not making promises if I'll ever get to those.

This is minute trends of the max wind, binned in integers, then taking the percent of time we were in ISC_LOCK states of >=600.

FAMIS 26243

Laser Status:
    NPRO output power is 1.819W (nominal ~2W)
    AMP1 output power is 66.92W (nominal ~70W)
    AMP2 output power is 138.6W (nominal 135-140W)
    NPRO watchdog is GREEN
    AMP1 watchdog is GREEN
    AMP2 watchdog is GREEN
    PDWD watchdog is GREEN

PMC:
    It has been locked 37 days, 21 hr 50 minutes
    Reflected power = 18.77W
    Transmitted power = 108.1W
    PowerSum = 126.8W

FSS:
    It has been locked for 0 days 7 hr and 12 min
    TPD[V] = 0.8582V

ISS:
    The diffracted power is around 2.3%
    Last saturation event was 0 days 7 hours and 12 minutes ago

Possible Issues:
    PMC reflected power is high (this is known, pending further alignment plans)

H1 was out of observing from 14:53 to 15:36 UTC to fix some issues with the SQZ system as we were seeing last night.

After Sheila adjusted the fiber polarization (alog77754), I reverted Corey's changes to the SQZ Guardians' nominal states (listed in his alog77740), then optimized the SQZ angle by running SQZ_MANAGER through 'SCAN_ALIGNMENT_FDS' and 'SCAN_SQZANG,' increasing BNS range by ~10Mpc.

Vicky pointed out that we have picos to adjust the fiber polarization for the new TTFSS fiber beatnote.  Adjusting that did bring our beatnote back to a similar level to what it was before the box was swapped on Tuesday, just below 8dBm.

There were many SQZ SDFs, I think related to going to OBSERVE with no squeezing.  I think it would be better to ignore these SDF files from the checks when we are in no sqz than to accept many new settings into the OBSERVE.snap, which kind of defeats the purpose of SDF. 

The RF Scanner resides in the MSR and its antenna is located on the LVEA roof, close to the GPS receivers. It scans for RF signals in the MHz range, producing a time-freq png plot every 10 minutes.

The freq plots are now available via the DTS web server, URL is  https://badger.ligo-wa.caltech.edu/rfscan/pngs/ (one directory per UTC day).

I converted the 144 daily plots into a mp4 movie for the days May 01-08, for example  03 May MP4 Movie. Note that there are some 700-800MHz bursts in the second half, which represents LHO business hours on site (5am - 5pm PDT Friday 3rd May).

TITLE: 05/10 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Observing at 131Mpc
OUTGOING OPERATOR: Ryan C
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 4mph Gusts, 3mph 5min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.12 μm/s
QUICK SUMMARY: H1 has been locked and observing (without SQZ) for almost 5 hours.

• Wind and microseism low
• All other systems nominal

I finally got round to comparing the visibility measurements we took in this entry and comparing them with the mode scan taken on April 16th before our mysterious drop in optical gain possibly due to the OFI.

April 16th Measurement:

HOM mis-match from scan = 0.09825 = 9.83% calculated using inferred height of carrier 02 and carrier 20 modes and the measured height of the carrier 00 mode.

HOM mis-match from visibility =  9.763 %

round trip loss: 3504 ppm

Measurement taken on April 30th - old alignment 

HOM mis-match from scan = 0.08454 = 8.45% calculated using inferred height of carrier 02 and carrier 20 modes and the measured height of the carrier 00 mode.

HOM mis-match from visibility = 19.870 %

round trip loss = 3289 ppm

Measurement taken on April 30th - new SR2 and SR3 alignment:

HOM mis-match from scan = 0.09954 = 9.95% calculated using inferred height of carrier 02 and carrier 20 modes and the measured height of the carrier 00 mode.

HOM mis-match from visibility = 14.415 %

round trip loss = 3495 ppm

The round trip loss seems to have been worse after the OFI problems started but I can't reconcile the two methods of measuring mode mis-match. In any case it seems like out current alignment has brought our current OMC round trip loss and the mode mis-match (as inferred from mode scans) back to the April 16th values.

TITLE: 05/09 Eve Shift: 2300-0800 UTC (1600-0100 PST), all times posted in UTC
STATE of H1: Observing at 153Mpc
INCOMING OPERATOR: Ryan C
SHIFT SUMMARY:

H1 is in No-Squeezing configuration (see procedure).  These SQZ nodes will need their nominal states  changed in their python files to return to Observing WITH-Squeezing: 

• MANAGER (back to FREQ_DEP_SQZ)
• OPO_LR (back to LOCKED_CLF_DUAL)
• LR (back to LOCKED)
• LO_LR (back to LOCKED_OMC)
• FC (back to IR_LOCKED)
• SHG (back to LOCKED)
• PMC (back to LOCKED)

LOG:

• 0158 H1 dropped out of Observing due to SQZ TTFSS nosediving since the box was re-installed in the afternoon.  Adjusted threshold to get another 1-2hrs of observing, but then ISS Pump and SHG locking issues bumped H1 out of Observing again.
• 0409 Lockloss
• 0441-0501 Initial Alignment
• 0650 NLN but no squeezing
• 0707 Back to Observing

Since the A2L script that measures a transfer function isn't quite minimizing our ASC noise in DARM, Sheila suggested re-finding the old A2L script that we used to use, which just looks at the height of the peak in DARM.

I think I've found it, in /opt/rtcds/userapps/release/isc/common/scripts/decoup/al2_min_LHO.py .  I made sure that it, and other scripts in that directory, were checked in to svn (they were last modified somewhere between 2018 and 2019, depending on the script).

The script (as wrtitten) uses the ADS to actuate each of the quads, and uses the demods to find the size of the signal (it does a sum of the squares of the I and Q of the demodulated signal).  The script just guess-and-checks several A2L gain values for each optic, makes a step, and checks again.  Once it's finished, it does a linear fit to find the A2L value at which the peak height is expected to be zero.  The script runs 8 dither lines (pit and yaw from each quad) around 20 Hz, so that it can do this guess-and-check for all the optics at the same time. 

The values in the script are out of date (we've slightly modified the frequencies we use for ADS while locking), so those values and the filter numbers for the matching bandpasses need to be checked.  Also, the excitation amplitude in the script is probably higher than we need (they are set to be 300 counts, but we use 30 counts at full power right now, but we may want a little better SNR so we might want to find a value that is between those two.

Also, we may find that we want to instead do the optics one at a time, at 30 Hz, where the coupling of ASC to DARM is more important to our range.

We can try this out during one of our commissioning windows later this week, to see how it goes.

Sheila asked a good question the other day of, Did SR2 alignment change between the beginning of O4b (when things were still good) and when we had the bad losses through the OFI (when things were bad, before the big shift).  The answer: no, I don't think SR2 moved very much (according to its top mass osems) when the the losses through the OFI showed up. It did move about 10 urad in yaw (see table below), which I plan to look into further.

I looked at several times throughout the last few weeks when ALIGN_IFO guardian had just finished up state 58, SR2_ALIGN at 10 W, which it now does every time initial alignment is automatically run.  These should all be single bounce off of ITMY, with the beam centered on AS_C by adjusting the SR2 sliders, for some given SR3 slider position (nothing automatic touches the SR3 sliders). 

In the table, I summarize the SR3 and SR2 top mass osems.  I've got 3 categories of times for the IFO situation:

• (1) Well before the large losses in the output arm,
• (2) With big losses in the output arm, but SR3 in its old position, and
• (3) After SR3 and SR2 moved to steer around the bad spot in the OFI (just for comparison).

Note that this table is not chronological, since I've grouped rows by IFO situation rather than time.  The SR2 and SR3 osem values that are in bold are the ones to compare amongst each other.  There does seem to be a 10 urad shift in SR2 yaw between the April 21st and April 23rd times.  There are no other run-throughs of the SR2_ALIGN state of ALIGN_IFO between these times to check.  This SR2 yaw shift (which is consistent even when we revert sliders to the 'pre shift' values and run SR2_ALIGN) is notable, but not nearly as large as what we ended up using for steering around the spot in the OFI.

Sheila, Jenne, Tony, Camilla

We've had locklosses in DRMI because the PRCL gain has been to high when locked on REFL1F.  Tony looked and thinks that this started on 77583, the day of our big shift in the output alignment.

Today we acquired DRMI with half the gain in the PRCL input matrix for 1F, this one acquisition was fast.  I've attached the OLG measurements for PRCL and MICH after the change. 

Tony is working on making histograms of the DRMI acquisition times, before the 23rd, from the 23rd to today, and eventually a histogram from today for the next few weeks to evaluate if this change has an impact on the DRMI acquisition times.

Jenne also found that it seems out POP18 build up seems higher in DRMI since the 23rd.

Jennie W, Sheila

Today we took OMC scans to help diagnose what is going on with our alignment through the OFI - that is, what is the mode-matching at our the old alignment (as of Monday 22nd) and our new alignment (as of this morning).

Sheila turned off the sidebands before the test and we had the ETMs and the ITMX mis-aligned initially for single bounce configuration.

Old alignment: SR3 M1 YAW OFFSET = -125 microradians

SR3 M1 PIT OFFSET = -437 microradians

SR2 M1 YAW OFFSET = -421 microradians

SR2 M1 PIT OFFSET = -64 microradians

Due to PEM measurements we switched from single bounce off ITMY to single bounce off ITMX.

Locked time = 1 minute from GPS 1398534847

Unlocked time = 1 minute from GPS 1398534984

Scan = 200 s starting at 1398535070 GPS

New alignment: SR3 M1 YAW OFFSET =  120.2 microradians

SR3 M1 PIT OFFSET = 437.9 microradians

SR2 M1 YAW OFFSET = 2061.7 microradians

SR2 M1 PIT OFFSET = -5.5 microradians

Locked time = 1 minute from 1398538330 GPS

Unlocked time = 1 minute from 1398538461 GPS

Scan = 200 s starting at 1398537927 GPS

Dark time with IMC offline and fast shutter closed = 1398538774 GPS

Mode mis-match measurments pending...

I went to FCES this morning to try to troubleshoot the sort of busted H1 GS13 on HAM8. I suspect there is something going on with the cable or interface chassis, but it's not something I think I've seen before. I tried swapping cables at both the rack and the chamber, and whenever the corner 1 chassis was connected to the H1 sensor, the transfer function from the H1 CPS to the H1 sensor would be half the magnitude of the other two sensor pairs. ASDs also show the H1 GS13 has half gain when the corner 1 sensors are connected to the corner 1 chassis. However, when the H1 sensor was plugged into the corner 2 or 3 chassis, all three sensor pair tfs would have the same amplitude. I could repeat this consistently, didn't matter how I swapped the cables around, as long as the H1 sensor wasn't plugged into the correct chassis all the l2l sensor tfs would look normal.

Attached plot shows two sets of data I took during this period, red blue and light green are the normal config, dark green, pink and light blue are with the H1 sensor on the corner 3 chassis, H3 sensor on the corner 1 chassis.

I will talk to Fil, but maybe in a couple weeks we can try running a temp cable from the FC mezzanine to the chamber, and see if that changes anything.

J. Kissel

As we continue to investigate both ADC noise (both broadband, in-general behavior) as well as down-converted aliasing noise in the new fast 524 kHz OMC DCPD signal chain, I needed to wrap my head around all the available channels in order to begin thinking about how to compare / take advantage of the differences between the channels.

I don't understand anything until I diagram it, so here's my diagram of the existing OMC DCPD signal chain as I understand it, hoping it helps others.

As mentioned in each of the previous aLOGs where I've started the investigation (LHO:67552, LHO:67530, LHO:67465, LHO:67297, LHO:67439), studies of the 524 kHz portion of the system are severely limited in that 
    (a) no 524 kHz channel stored in the frames,
    (b) one can only look at 3 test points at a time,
    (c) we don't have any analog measure of the noise between 524 kHz and 102.4 kHz (the upper limit of the SR785) to compare against

But, we'll do what we can!
Hopefully this visual aide will help understand future studies.

For example, because we *don't* have any digital anti-aliasing filters in the OMC-PI SIG filter bank, we can compare these test point channels, 
    - H1:OMC-DCPD_A0_OUT (524 kHz, w/ digital anti-aliasing)
    - H1:OMC-PI_DOWNCONV_SIG_OUT (524 kHz, w/o digital anti-aliasing)
    - H1:OMC-PI_DPCD_64KHZ_AHF  (65 kHz, w/o digital anti-aliasing)
    - H1:OMC-DCPD_A_IN1  (16 kHz, w/ digital anti-aliasing)
to explore the effectiveness of the digital anti-aliasing filters to better understand the aliasing that Evan Hall found in LHO:67328.


Note -- and this is something that I'm still learning (via conversations with Erik von Ries and Daniel Sigg and their aLOGs, including but not limited to LHO:67587, LHO:67560, LHO:67291) -- the h1iopomc0 model actually runs at 65 kHz (really, 2^16 kHz). In order to achieve a pseudo-524 kHz data stream, there's a for loop within the h1iopomc0 model that's able to complete 8 iterations (thus 2^16 kHz * 8 = 2^19 kHz = 524 kHz) during any given 65 kHz clock cycle.