Ed, Patrcik, Kiwamu,

In addition to the ISS issue (alog 22863), tonight we had two other issues with the alignment loops (DHARD instability and SRC2 instability, reported in alog 22859). After some investigation, we found that IM1 and IM2 had different alignment than usual, mainly in pitch. Even though we are not sure how exactly this affected all three issues we had tonight, we realigned them so that the OSEMs read the same values as the past. This resulted in two positive consequences as follows.

(1) Realigning IM1 and IM2 brought IM4 trans and POP_B QPDs back to where they were.

(2) The realignment increased the carrier power in both PRC and arm cavities by 5 or 6 %.

See the first attachment for the increased carrier power. We aligned IM1 and 2 while the interferometer was locked at low noise. We accepted the new IM alignments in SDF (see the third attachment). Even though we still suffer by the DHARD instability, at least the SRC2 instability seems to have gone away after the realignment. I did not attempt to maximize the carrier power but it makes me think that there might be a "sweep spot" for IMs' alignment where the carrier power is maximized in the interferometer. Also, note that IM4 trans sum increased as well with the newly aligned IMs, but only 0.6% perhaps due to the beam on IM4 trans getting centered.

IM1 and IM2 moved likely due to the untrip of HAM2

According to trends, it seems that both IM1 and 2 changed the alignment at the time when Ed untripped HAMs 2 and 3 (alog 22835). This effect is something we already knew (alog 22719). For some reason, this time it changed mostly IM1 and IM2 in pitch. See the second attachment for the trend. IM1 moved by about 1 urad, and IM2 moved by about 50 urad as seen by the OSEMs. Also, yaw of IM1 and 2 also moved, but neither IM4 trans nor POP_B see a significant change in yaw. The MC mirrors seems to have been unchanged.

DHARD is still unstable

I was hoping that the realignment of IMs would magically fix all the issues we had, but the DHARD instability seems to remain. The symptom is that both pitch and yaw DHARD oscillate at around 0.6 Hz. As was suggested by Jenne, we decreased their loop gain which fixed the instability. I have no idea why they oscillate at 0.6 Hz and why the gain reduction helped. The pit gain is set to 7 (which was 10 originally), and the yaw gain is set to 10 (was 15 originally). For this lock stretch, we accepted these values in SDF and this means that they will show up in the SDF next time when we lock the interferometer. See the fourth attachment for the SDF.

To those who will relock next time

Since we have aligned IM1 and IM2 in situ when the interferometer was locked at low noise, the interferometer alignment in the cold state will be somewhat far from the optimum. I would recommend running the full initial alignment before relocking.

10:35UTC

These all appear to be test injections that occured between Oct 5-6. I looked at the page out of curiosity and I saw this list on the home tab. I'll defer attention to these to someone who was involved in those activities. 

09:25UTC

07:51UTC

TITLE: Oct 27 OWL Shift 7:00-15:00UTC (00:00-08:00 PDT), all times posted in UTC

STATE Of H1: Locking

OUTGOING OPERATOR: Patrick

QUICK SUMMARY: Jenne and Patrick discussing the state of affairs with Doug at Livingston. They’ve been down for 30+ hours and we’re currently having issues with ISS second loop not engaging. Kiwamu is on his way in. It looks as if my shift will get cut short when L1 goes into maintenance day (04:00PDT)

Yet again, we had trouble with engaging the ISS. 

I put in a notification during ENGAGE_ASC_PART3 for the operator to check the diffracted power level if it is more than 0.8% away from nominal.  While it's probably okay if it's within 1% (other alogs say 2%, but I've had more consistent success with 1%), I chose a somewhat smaller number out of an abundance of caution. 

However, even though the diffracted power was within a few tenths of a percent of nominal, the ISS would stall, and not engage.

As part of the PREPARE_ISS state, the guardian changes some setpoint values such that the H1:PSL-ISS_SECONDLOOP_SIGNAL_OUTPUT channel becomes small.  We need to do this so that the DC-coupled ISS doesn't kick us out of lock when it is engaged.  (For unknown reasons, this convergence has seemed to be more successful when the diffracted power is close to 8%).  This SECONDLOOP_SIGNAL_OUTPUT wasn't converging though.  It was bouncing around between +/-5 counts.  The absolute value of this channel must stay below 2.5 counts in order for the ISS to close the second loop. 

In the end, what I did, was cheat and change the gain H1:PSL-ISS_SECONDLOOP_SIGNAL_GAIN to 0.1 so that the ISS second loop would turn on.  Then, VERY slowly I turned the gain back after we had arrived at NomLowNoise.  As I increased the gain in steps of 0.1, the diffracted power dropped by half a percent or so.  So, at each step, I waited for the diffracted power to come back near 7% or so before going to the next step.  While this worked once, it has failed a few times after that, so let's not make it the new plan.

Patrick and I called Kiwamu, and followed the instructions in aLog 22449 to manually turn on the second loop (basically, turn on the button next to "second loop input to first loop" on the second loop screen, when the second loop output (near bottom right of that screen) is close to zero).  Anyhow, that is making the diffracted power go super low (less than 1% sometimes), until the outer loop loses lock, and the diffracted power jumps up really high (45% or more).  At this point, it's not at all clear why this isn't working, so Kiwamu is on his way in to try to diagnose things.  

We've checked in with Mike, and since LLO is still down, if Kiwamu and Ed can't figure out the ISS, we'll call off the rest of the owl shift. 

TITLE: 10/26 [EVE Shift]: 23:00-07:00 UTC (16:00-00:00 PDT), all times posted in UTC
STATE Of H1: Lock acquisition
SHIFT SUMMARY: Initially had trouble locking DRMI. Went to LOCK_PRMI and aligned the BS. Jenne had put the ISI blends back to 45 mHz. Could this have moved the BS alignment? Successfully moved from LOCK_PRMI to LOCK_DRMI. No trouble locking DRMI since. Evan, Jenne and Sheila worked on ASC SOFT loop instability (see alog 22858). We made it to nominal low noise but loss lock while running the a2l script (see alog 22860). Second lock at nominal low noise was lost after trouble with the ISS second loop.

Still having trouble with ASC loops and also with the ISS second loop. Jenne and I called Kiwamu about the ISS second loop and he decided he will drive in. Also contacted Mike. We have permission to call off the second half of the owl shift if no progress is made.
INCOMING OPERATOR: Ed

03:58 UTC GRB alert. Neither IFO locked.
04:21 UTC Locked at NLN. Set H1:SUS-ETMY_L2_DAMP_MODE3_GAIN to 10 and H1:SUS-ETMY_L2_DAMP_MODE9_GAIN to 200 as per SDF differences.
05:04 UTC Lock loss.
05:13 UTC ISI EMTY Stage 2 WD tripped after locking on DRMI 1F. Jenne reset it.
05:39 UTC Locked at NLN.
05:41 UTC Lock loss. Trouble with ISS second loop.

It may have gotten lost in all of the alogs over the weekend, but I mentioned in a comment to an old alog (22789) that we had not been getting any real data for the ETMY spot positions. 

Since LLO is still down, and I've been here all day trying to get the IFO locked, I rewarded myself with ~15 minutes of A2L investigation. 

It turns out that we have had the input to the ETMY L2 DITHER filter bank off, so we weren't actually dithering ETMY.  So, that explains why all of the data we have been getting looked so poor.  Anyhow, I have turned those on and accepted them in SDF, so when the oscillators turn on with the a2l script, we should actually be sending some signal out.

Evan and Sheila have left. Jenne is still here. We have made progress but the ASC loops may still be unstable (but in a different way than before). The wind has come down below 10 mph. The microseism is between .2 and .5 um/s.

Patrick, Jenne, Sheila, Evan

When the wind died down and we were able to relock using 45mHz blends, we decided to have a quick look to see if we can fix the problems we've been having with soft loops.  In the end we just made the low gain that we have been using with the soft loops when we are using 45mHz blends permanent.

Background:  some gain peaking in the soft loops unfortunately seems to be at the same frequency as the gain peaking in the 45mHZ blends, making it dangerous to turn the soft loops up to their full gain when we are on the 45mHz blends because of the microseism.  The operators have been manualy turning down the gain in these loops in the last week when they are using 45mHz blends.  

We wanted to try to fix the instability in these loops but didn't suceed.  Along the way we noticed that we have 20dB more gain in the offloading path for the ITMs than the ETMs.  In the words of Daniel sigg, this is the underbrush of historical growth.  

We made a few attempts to make the offloading paths have the same gain: first we turned the gain down in the ITM top masses, this worked fine until we increased the power when the ITMs saturated the pums.  Then we turned up the offloading gain in the etms to match the ITMS, this caused a problem with the SRC asc loops and also broke the lock.  In the end, we have just gotten rid of the increase in gain for the soft loops all together.  This means that the ugf of the soft loops is now probably 3 mHz or so.  

What this means for operators:

You don't have to worry about the soft loops anymore when you change blends.  

There is no longer a long wait for the soft loops to converge in ENGAGE_ASC_PART3, but there is a check in DC readout to make sure the soft loops converge before we increase power. 

Strong glitch signals are present in several of the top BBH trigger times on October 23. They can be viewed here:

https://ldas-jobs.ligo-wa.caltech.edu/~jacob.broida/Oct23/BBH/GW/1129610330/
https://ldas-jobs.ligo-wa.caltech.edu/~jacob.broida/Oct23/BBH/GW/1129664910/
https://ldas-jobs.ligo-wa.caltech.edu/~jacob.broida/Oct23/BNS/GW/1129627593/

No clear correlation in any auxiliary channels, though they are potentially electrical in origin.

I've added red warning boxes around the monitor bars when each mode gets rung up above a certain threshold (~3 order of magnitudes above its noise floor). Note that it is normal for the boxes to go red during lock acquisitions and the begining of the lock. But once you've reached NLN for a while and if the red boxes still show up (RMS values reached 3). The action must be taken to damp those modes. Due to limited filter bank I can only monitor 2 lines at a time. So make a 0.01Hz BW spectrum and zoom in to see which one really rung up. Almost all of the fundamentals damping filters are already turned on by Guardian. I will be making a monitor for 2nd harmonics soon. Stay tuned.

TITLE: 10/26 [EVE Shift]: 23:00-07:00 UTC (16:00-00:00 PDT), all times posted in UTC
STATE Of H1: Lock acquisition.
OUTGOING OPERATOR: Cheryl
QUICK SUMMARY: Lights appear off in the LVEA, PSL enclosure, end X, end Y and mid X. I can not tell from the camera if they are off at mid Y. Seismic appears to have recovered from earthquake in Afghanistan. Microseism is still high but trending down. Winds are back below 20 mph. Jenne put ISI blends back to 45 mHz.

Jenne, Evan and Sheila are here and helping with lock acquisition and violin mode damping.

TITLE: Ops Day Summary: 15:00-23:00UTC, 8:00-16:00PT, all times in UTC

STATE of H1:  major interference in locking the from earthquake after effects, useism, and wind - locking is getting progressively better

Support:  Jenne, Evan, and Sheila

Quick Summary:  IFO is locking well up to DRMI, and gotten past DRMI, but not to ENGAGE_ASC, can now get to DARM_WFS

Details: 

- Ground motion significantly effecting arms, with arm powers in green and red dipping down to as low as 0.5-0.7

- Stopping at DARM_WFS to damp ROLL mode early - this is the stage where the signal becomes useful

- Switched to Quiet_90 ISI blend filters - alogged earlier

- Needed higher gain to lock X arm in IR, while doing an initial alignment

- Day spent considering and sometimes trying new approaches to improve locking with high ground motion

Shift Activities: work around the site

- Joe and Chris on X arm sealing the beam tube, morning and afternoon

- Richard to Electronics Room, 20:45-21:15UTC

- Kyle on Y arm at the y28, doors closest to End Station

Control Room Display:

- restarted cameras on video4 (camera's froze)

- restarted nuc4's dtt, DRMI_FOM_displacements

- Carlos working on nuc5 (couldn't get to lower screen when logged in)

Currently:

- locking is getting progressively better

- earthquake (~14 hours ago) effects are gone 

- useism is slowly coming down

- wind is dying down

In light of the violin mode stuff over the weekend, I wanted to make sure we aren't going to be caught unawares by other harmonics ringing up.

We have paid considerable attention to damping the fundamentals and second harmonics of the violin modes, but in general we leave the higher harmonics undamped. (We have had some isolated cases in which we have had to temporarily apply damping to high harmonics; see, e.g., LHO#18599).

I checked the heights of the third harmonics during the first long lock (25 hours long) that we had after the power outage. I chunked the DCPD sum timeseries into 1000 s segments and then took ASDs of each. To identify the violin modes, I simply looked for peaks in the DCPD spectrum that were higher than some threshold above the noise (in this case, the noise floor is about 1×10⁻⁷ mA/Hz^1/2, and the threshold I chose was 5×10⁻⁶ mA/Hz^1/2). This resulted in 25 peaks being identified. For each ASD, I integrated under each peak to get an rms mode amplitude. Since the violin modes are anharmonic, I believe that these peaks (which range in frequency from 1456.18 Hz to 1484.67 Hz) are truly third harmonics, rather than upconverted first harmonics (which range from 498 to 509 Hz, and hence we would expect upconversion to appear from 1496 to 1527 Hz).

All 25 peaks appear to be ringing down, with time constants on the order of 2×10⁵ s (≈50 hours). I fitted each ringdown to an exponential, which resulted in Qs ranging from 0.55×10⁹ to 1.28×10⁹. [For similar results on lower-order mode Qs, see, e.g., Keiko's measurements on L1 IY.]