TITLE: 07/02 Owl Shift: 07:00-15:00 UTC (00:00-08:00 PST), all times posted in UTC
STATE of H1: Observing at 145Mpc
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 14mph Gusts, 9mph 5min avg
    Primary useism: 0.06 μm/s
    Secondary useism: 0.06 μm/s
QUICK SUMMARY:

- H1 has been in observing for ~30 minutes

- CDS/DMs ok

- Ground motion still ringing down from the EQ, wind is relatively high ~30 mph

TITLE: 07/02 Eve Shift: 23:00-07:00 UTC (16:00-00:00 PST), all times posted in UTC
STATE of H1: Observing at 144Mpc
SHIFT SUMMARY:

Lock#1:

We successfully rode through a 5.6 EQ from Tonga at 3:10 UTC, in EQ mode at 03:23 UTC back to calm at 04:04, seismon peaked around 1900 and we got to over 1 in the 0.03-0.01 ground motion..

Lockloss at 04:15UTC

Lock#2:

Xarm struggled a bit, went through increase flashes twice, it took around 20 minutes. Went through PRMI twice, lockloss PRMI after 2nd attempt, I interviened during the 3rd attempt and adjust PRM and SRM in yaw since AS AIR was very yawed and it caught. ISC_LOCK went into error during DRMI_1F, I reloaded it and it was fine but it lost DRMI and it had to be relocked but it relocked quickly but a few minutes later lost lock at BS_STAGE2. Ground motion is still elevated

Lock#3:

Smooth relocking this time, until we got to OMC_WHITENING at 05:41UTC where the we had to stop and damp violins, they are quite rung up. 2 million ADC counts. So we'll be here damping for a while, a lot of the gains were reduced by guardian since they were rung up, I'll step them up as I'm able to.

Back into NLN and Observing at 06:30 UTC

LOG:

No log for this shift

I've made it back up to OMC_WHITENING but the violins are very rung up (2 million DCPD ADC counts) so we're probably going to be here damping for a while.

We were ringing down from a large EQ from Tonga(5.6) at the time, DCPD saturation then an immmediate lockloss. Winds gusting in the 30s and elevated ground motion from the EQ at the time.

STATE of H1: Observing at 140Mpc

In Observing since 23:31UTC

The wind has just as yesterday started to pickup, gust of over 30mph and arm ground motion increasing. The violins have come down a good amount but there's still more to go.

TITLE: 07/01 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Observing at 145Mpc
SHIFT SUMMARY:

H1 continues to be ailing with rung-up violins.  

Today's additional issues:

• Power Glitch which took down EX/EY SEI systems, but this was recoverable fairly easily.
• Post-power glitch, Guardian did not like the alignment of the BS (because the guardian log said something along the lines of BS too far out of alignment).  At any rate, this mystery remains a mystery, because as I was beginning to pull my gray hair out, toward the end of the shift--ISC LOCK finally locked PRMI!!
  • I mentioned this issue to Keita, and he ended up doing an investigation on this---apparently the alignment of the BS was fine, and it was more that MICH BRIGHT wasn't locking and/or triggering properly---he may post an alog later.  
  • Note:  This is a new-to-me issue.
• Violins still take atleast an hour to damp before one can go to NOMINAL LOW NOISE :(

LOG:

• 1528 Lockloss (seismically quiet)
• 1559 H1 stuck at CHECK VIOLINS BEFORE POWER UP due to rung up violins.....usually (i.e. last couple days) we can make it to 50W & then we have to address violins, but this issue occured at 2W (right before powering up).
• 1622 Small power glitch takes down EX & EY seismic. (lights flickered in the control room, and later found out MSR briefly switched to UPS power, but that is all that affected H1 for this glitch.
  • Took OBSERVATORY MODE to CORRECTIVE MAINTENANCE & worked with Jim to address (Richard & Dave also phoned in)
  • 1806 SEI restored
• 1808 Locking
  • DRMI, PRMI, and CHECK MICH FRINGES didn't look good (latter said BS was too misaligned)
  • 1824 ISC LOCK node in ERROR (it was RED, I hit the LOAD button to clear it up---not really sure why this happened....it occurred while I was chatting with Keita on TeamSpeak and ISC LOCK was trying to acquire PRMI).
• 1844 Initial Alignment run
  • MICH BRIGHT and SRC ALIGN did NOT complete (even with BS & SRM tweaks)
• Stuck here trying to figure out why Guardian thought the BS was to misaligned---I had looked back at the last time we were at 2W last night and it was fairly close.
  • Flashes for CHECK MICH FRINGES for isc_lock and the MICH BRIGHT and SRC ALIGN did not look wildly out of alignment
• 2049 Went for another lock (I could have swore I selected CHECK MICH FRINGES), but apparently I selected PRMI ASC
  • While I was on Teamspeak talking with Keita, PRMI locked, ASC tweaked up the alignment, and then continued with locking.
• 2020 Stuck at CHECK VIOLINS BEFORE POWER UP.
  • MANUALLY skipped this step to continue with POWER10W (& onward.)
• Ended off shift stuck at CLOSE BEAM DIVERTERS (just before OMC WHITENING), just so I could help with damping violins.  Spent about 30min assisting all (4) test masses with their violin damping gains.  Then went to OMC WHITEING.
• Basically needing to wait about 1hr for the rung up violins to get past OMC WHITENING---the latter had this status message:
  • "ADC Counts for the DCPDs are at 1152340, larger than the 524288 available counts!  Cannot turn on OMC whitening! Stay here and damp violins"
  • I've not seen counts this high!
  • At any rate, H1 finally was able to get to the OMC_WHITENING step.  Ryan is going to wait a little longer since turning omc whitening on is bumps up the violins again...but they are all damping down nicely.

TITLE: 07/01 Eve Shift: 23:00-07:00 UTC (16:00-00:00 PST), all times posted in UTC
STATE of H1: Corrective Maintenance
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 19mph Gusts, 15mph 5min avg
    Primary useism: 0.05 μm/s
    Secondary useism: 0.07 μm/s
QUICK SUMMARY:

We've recovered from a power glitch, currently waiting for violins to damp a bit more before bring us to NLN

CDS/VAC/Dust looks good, winds a little high

Back into observing at 23:31

In brief, looking at the bicoherence of DARM with itself, there is evidence that broadband noise in the 10 to 50 Hz region is non-stationary and modulated at about 2.6 Hz, and at 13.2 Hz.

The analysis is performed by computing the bicoherence of DARM with itself. In the case of a quadratic process generating noise in DARM, frequencies can be mixed, meaning that the signals at frequencies f_1 and f_2 can be mixed to generate a signal at f_1 + f_2 and f_1 - f_2. The bicoherence is a way to look for phase coherence between pairs of frequencies f_1, f_2 and the product frequency f_1+f_2 (or f_1 - f_2 or the other combinations).

The usual linear coherence is a function of only one frequency. The bicoherence is instead a function of two frequencies f_1 and f_2. If the bicoherence of DARM with itself at (f_1, f_2) is high, this is an indication that some quadratic process is mixing the frequencies and generating noise at f_1+f_2.

The attached plot shows the bicoherence of DARM with itself, using one hour of data. Several different times have been used, with consistent results. The bicoherence plot shows three interesting features:

1. a broadband feature with "high" bicoherence that shows correlation of boardband noise between 10 and 40 Hz with a 2.6 Hz peak visible in DARM (and the first two or three harmonics). This indicates that the DARM noise in the 10-40 Hz region is modulated at 2.6 Hz. More below on what could be the origing of this 2.6 Hz peak visible in DARM (and in many many other channels)
2. another broadband feature, again in the low frequency region (20-50 Hz) that has elevated bicoherence with a 13.2 Hz frequency. It's not clear what is the origin of this 13.2 Hz modulation, or whether this is related to the bumps at multiples of 13 Hz reported elsewhere (those are at 13.1 Hz which is probably different from what we see here).
3. calibration lines show also bicoherence with the 2.6 Hz peak, and this is enough to explain the bumps just above the calibration lines, that appear to be spaced from the lines by 2.6 Hz

The attached plot shows the bicoherence in the (f_1+f_2, f_2) plane. Therefore the x axis shows the "target" frequency where the quadratic noise ends up in DARM, and the y axis shows the modulation origin. The full bicoherence plot is typically plotted in the (f_1, f_2) plane and spans positive and negative frequencies. I show here only part of the plane, since the rest contains the same information. The bicoherence plot on the full plane has a lot of symmetries.

I'm convinced this is a real evidence of quadratic noise coupling, since the bicoherence pattern is repeatible for several different times in the past few days. I also did some numerical experiments to confirm that the results is not likely to be due to an artifact, but it is very likely to be due to modulated noise. More details in the attached PDF file.

What is the origin of the 2.6 Hz peak in DARM?

I don't have conclusive evidence yet, but a 2.6 Hz peak coherent with DARM is visible in many signals. A full list is attached, in alphabetical order. The peak is visible

• in all DARM related signals as expected
• in many angular signals: CHARD, CSOFT, INP1, MICH, PRC1, PRC2, SRC2, many of the DC centering loops 
• ETMX M0 and R0 signals. Looking at M0_L and R0_L, the 2.6 Hz peak has a ratio of almost exactly -1. I'm not sure about the sign of the top stage OSEMs, this might mean that ETMX M0 and R0 are moving in opposite directions at 2.6 Hz

What's next?

I suggest we perform some noise injections at 2.6 Hz in the ASC loops and in the ETMX M0 vs R0 controls. If we can add a 2.6 Hz line that is just a bit larger than the current level in any of those signals, we might be able to see the DARM noise in the 10-50 Hz region increase. That could help us find the origin of the 2.6 Hz motion and possibly fix it.

More investigations are needed to find the origin of the 13.2 Hz modulation.

Richard, Corey, Jim, Dave:

At 09:22 the site experienced a power glitch. The MSR UPS went onto battery backup for 3 seconds (logs shown below).

As was the case last Monday, the VFD chassis for the end station HEPI Pump Controllers tripped (see attachment). We don't see any other obvious issues at this time.

Corey is driving to the end stations, with remote support from Jim, to reset the VFD chassis.

Date: 07/01/2023
Time: 09:22:22
Code: 0x0109
Warning - UPS: On battery power in response to an input power problem.

Date: 07/01/2023
Time: 09:22:25
Code: 0x010A
Informational - UPS: No longer on battery power.

Sat Jul 01 10:06:23 2023 INFO: Fill completed in 6min 22secs

I'm trying to go through the same commissioning procceedure that LHO went though to get simulines optimised and working.

Essentially:

1. Start with really small injections. Looking at actuators to make sure that we have made sane choices in amplitudes by looking at all actuator outputs through the injection and making sure that we are far, far, from the DAC limits, as we would expect from the intended overall injection amplitude reduction.
2. Increase injection amplitudes and look for harmonics in odd places. In LLO, PCALY would have harminc sidebands and various frequencies. However due to the choice of frequencies, those never coincided with other injected frequencies. In a quick check I saw that Jeff implemented my suggested list of frequencies at the start of the year - so I hope to see that this will not be an issue.
3. We will aim for around 50% of the effective injection SRN (scaled by increased injection lengths, the amplitudes would be lower), and then analyse the data to selectively increase amplitudes where needed, to get results comparable to the old dtt templates.

I have built a set of injection templates in my gitlab which take 20 minutes each to run. I'm currently testing a version of my simuLines that is supposed to catch locklosses and ramp everything down, but if there is an issue we can revert to the previous version that doesn't do that, which is in an svn directory.

The news hot-off-the-press is that Louis implemented support for my file products in the pyDARM report generation and it looks good for some of our LLO data.

Me, Louis and maybe Jeff remotely; have planned a time section on, tentatively, Wednesday morning 10 am in LHO time to run a number of these and get this working there.

While dealing with rung up violins, we had a lockloss at 16:22:16utc which tripped EX & EY HEPI & ISIs, but at the same time I also noticed a flash in the Control Room lights (kind of similar to Ryan C's experience (alog70829) 5-days ago.

Attaching a look at the EX MAINS (need to find EY & CY....I couldn't find those channels when I swapped EX for those building) :0/

But the EX MAINS step at 16:22:16utc, does not seem too out of the ordinary and occurs every few hours.  At any rate, I will work on restoring next.

We just had a lockloss during lockloss....more in separate entry.

While locking somewhat normally through ISC LOCK states, happened to look up and see H1 stuck at CHECK VIOLINS BEFORE POWER UP (H1 was at 2W).  As noted earlier, one could easily see (from early stages of locking) violins were rung up pretty bad.  This is a new scenario for me (I could have sworn we had this check at a later state....i.e. where Guardian would look at violins and hold until we violins damped down to a safe value before powering up). 

At this state, there was no violin damping via guardian.  So I was looking through the violin damping materials, to find a starting place.  From this table, I tried to start here, but this table does not cover every mode (i.e. ETMY mode8 was really rung up, but I didn't see any entries for it).  So I moved on to an entry and then tried settings for 2W (i.e. ETMy mode1).  Unfortunately, this did nothing, or it started ringing up this mode. 

I then went to the VIOLIN DAMPING guardian to go from the TURN OFF DAMPING ALL  ----to-----> ENGAGE DAMPING 2W.  While in the 5min sleep, there was a lockloss (which I'm suspecting was a power glitch).

This is going to be a lovely shift.

While I was putting snacks in the fridge and turning off lights in the OSB, came back to find H1 down--seismically quiet on-site. 

Good News:  ALSx had NO PLL issues.  We'll see about violins (will get prepared to help damp them).

Bad News:  Can already see violins are rung up (while at ENGAGE ASC).  So I'll hold at DAMP VIOLINS FULL POWER and then help guardian damp all the violins....it's been taking an hour to do this though for the few locks.

TITLE: 07/01 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Observing at 146Mpc
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 8mph Gusts, 5mph 5min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.06 μm/s
QUICK SUMMARY:

Receiving a nicely locked H1 which has been locked 5.75hrs. 

Austin gave me a rundown of items to look out for with his lockloss experience:

1. X-arm PLL still was an issue (so may need to employ workarounds:  lower threshold & possibly reset Crystal Frequency
2. Sounds like Violins continue to get rung up after locklosses and result in ~1hr of waiting for the violins to damp down enough to allow one to engage OMC Whitening.
3. Hopefully there's no lockloss today!  *knock on wood*

Oh, and the winds have died but the high temperatures continue outside.

Looking at intensity noise in reflection of the interferometer allows us to measure the mode matching as well as the reflection coefficient.

The idea is that fluctuations above the cavity pole are promptly reflected by the interferometer, whereas the DC field will be resonant and have a reflectivity smaller than unity. In our case, where we are close to critically matched but still over-coupled, the reflected DC field also picks up a minus sign. Any field that is not mode matched will simply be prompt reflected and not acquire a minus sign. The later is true for both the fluctuations and the DC field.

Including the total reflected power, one can then invert the equation and determine both mod matching and reflectivity. A note detailing the derivation can be found in LIGO-T2300249.

Using the values measured in alog 70982, we get

For this derivation we neglected to include the RF sidebands. Typically, they are small, but the note details how they can be included if the power is measured as function of the modulation index. The 75W interferometer wasn't thermalized yet, when the measurement was taken and we can expect an additional 1.2% of power increase in reflection. If we attribute all to mode mismatch, we would have a total of ~4.4% of the input power not mode matched.

The mode mismatch power is important for figuring out the impedance matching of the PRM, see alog 68451.