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Reports until 20:06, Tuesday 09 December 2025
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jenne.driggers@LIGO.ORG - posted 20:06, Tuesday 09 December 2025 - last comment - 11:24, Wednesday 10 December 2025(88450)
Locking progress today

[RyanS, Jenne, all the other control room people, of whom there were many]

Summary: We can get to PREP_DC_READOUT_TRANSITION (at least once), but had trouble with OMC locking.  

We tried some locking earlier in the day, first starting with doing the same trick as yesterday (alog 88432) and moving ITMX while ETM and TMS were controlled by green WFS to improve the COMM beatnote.  However, I only ended up moving ITMX 0.3 urad in yaw.  Because this was a small change and Sheila reminded me that we can lock (when the wind is low) with comm down at -10 dBm-ish, so I decided that next lock we'd just use the camera setpoints (which we did and was successful).  During this time, we had to disable SRC1 and PRC1 in DRMI ASC because they were pulling the alignment away, and we weren't really on the POP QPDs at all.  Anyhow, we got to PREP_ASC_FOR_FULL_IFO twice, but the alignment never looked excellent.  We tried ENGAGE_ASC_FOR_FULL_IFO once, and it was really bad and killed the lock.  The other time, we think that the seismic state changing from useism to windy caused us trouble (but, in retrospect, likely was only troublesome because the alignment was so poor).

We then realized that, after the big earthquakes from this weekend, our input pointing wasn't good.  RyanS then set the IMs 1, 2, and 3 such that they matched their top mass osems (not necessarily their sliders).  We then moved IM3 a little bit to get back to where we had been on IM4 Trans QPD before the power outage (pit of 0.239, yaw of -0.071).  We were able to quite easily run through an initial alignment with this.  During this and all subsequent initial alignments, we used the pre-power outage green setpoints (including cameras).  The COMM beatnote was around -9 dBm, so that's pretty good. 

Some time around here we had the -18 V failure, see alog 88446 for details. 

Then, we did another initial alignment.

Then, the CDS team let us know that they needed to reboot all the models, see alog 88448 for details.  After all the models were back, Ryan restarted the ALS_[X,Y]ARM guardians using "guardctrl restart NODE", so they would know how to start their AWGs in case SCAN_ALIGNMENT needs to be run.

We then restored sliders to just after one of our recent inital alignments, and Ryan then reset the IMs 1-3 to their top mass osems again, and again moved IM3 to get us back to the pre-power outage spot on IM4.  ....And did yet another initial alignment.

After this, we finally were able to try to lock for the first time in several hours!  And things went really, really quite well.  We basically didn't touch anything at all (PRC1 and SRC1 still disabled in DRMI ASC), and were able to lock to PREP_FOR_DC_READOUT!  Yes, you read that right, ENGAGE_ASC_FOR_FULL_IFO did just fine on its own.  The buildups went down then came back again, so we were a bit scared, but it kept hold of everything and was able to converge.  The PRM's ADS alignment took a loooonng time to converge, which we've seen before after a power outage (eg, alog 86944), so after all of the ASC was on (including SOFT_LOOPS) and converged, I reset the POP_A offsets, and Ryan accepted them in safe.snap.

(Later, after some relocks, we're able to use PRC1 in DRMI ASC now that its offsets have been set.  But, still SRC1 is left out since it's pulling things away).

The violin modes are quite high, but not so bad that it's impossible to get 2W locked. 

We went to PREP_DC_READOUT_TRANSITION, and noticed that we were having trouble locking the OMC.  We're still not sure what's going on here, and we're going to leave it for the night.  We're hoping to leave it at PREP_DC_READOUT_TRANSITION, however the second time that we did ENGAGE_ASC_FOR_FULL_IFO, something pulled us away and we lost lock. We'll let it try one more time.

OMC locking troubles and symptoms:

Comments related to this report
ryan.short@LIGO.ORG - 20:30, Tuesday 09 December 2025 (88451)

Screenshot attached of newly SDF accepted POP A offset values.

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jenne.driggers@LIGO.ORG - 20:31, Tuesday 09 December 2025 (88452)

Okay, we tried *one* more time, this time doing the same skip-over-tune_offsets thing, but having remembered to do the critical first few lines in the main state. We seemed to successfully get onto DC readout, the ISC_LOCK state DC_READOUT finished, and we  started to see the DARM trace on the wall come down.  However, we lost lock pretty suddenly.  Ryan and I are giving up for the night.

Also, during engage ASC for full IFO, as part of getting up to attempting DC readout, we turned SRC1 off by hand since it was starting to pull things away.  Ryan by-hand aligned SRM to get us back to good alignment.  Ryan tried turning on SRC1 pit after the SOFT loops were converged, but that immediately started pulling us away, so we turned it back off and re-touched up SRM.

sheila.dwyer@LIGO.ORG - 22:40, Tuesday 09 December 2025 (88453)
  • Next lock attempt we lost lock on during the CARM offset reduction. 
  • Next time I stopped in DRMI_CHECK_ASC since the sideband build ups didn't look great, I struggled to fix them by moving SRM, then lost lock to some strange glitches (see screenshot).  I think the reason I was having trouble adjusting the alignment by hand may have been that SRC2 was on (SR1 off as Jenne said above).  I've set the useSRC2 flag to false in DRMI ASC now.  
  • Had ALS locklosses for a little while, and DRMI was poorly aligned, so I ran initial alignment. 
  • After that initial alignment locked well, like Jenne + Ryan's last comment above I had to turn off the SRC1 loop in engage ASC for full IFO.  I've commented these out of ENGAGE_ASC_FOR_FULL IFO for now, so we don't need to be manually turning it off to avoid locklosses. Then as the soft loops came on I adjusted SRM by hand to keep the sideband powers OK.  The guardian ran through OMC locking and tune offsets without issue, so I let it try DC readout without looking into the issues that Jenne and Ryan had with the OMC, this did not work.  One thing that could be an issue is that we recently moved teh DARM offset step (which also requests the OMC guardian to lock and do tune_offsets) 88346.  A few weeks ago this was aparently happening after engage ASC but before the soft loops, SVN diffI've now set the DARM_OFFSET step back to it's older place, after the first round of ASC is engaged, so that TUNE_OFFSETS should be happening at the same place in the sequence that it's been at since shortly before the OFI break. 
  • Because of the manual stepping of the SRM, I'm asking it to run initial alignment now so that in the morning the IFO will be well aligned.  
  • Made one last attempt.  This time I tried stepping through DC_READOUT state, we lost it as soon as we ramped the matrix, although that looked to be stable in the previous attempt.  
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jenne.driggers@LIGO.ORG - 11:24, Wednesday 10 December 2025 (88460)

Looking back at the locklosses at DC readout transition, Ryan and my lockloss at ~8:30pm seemed to be successful through the matrix ramp and beyond.  However, we got a bit of a ringup at ~18.5 Hz in LSC DARM. 

Sheila's lockloss around 1030pm is similar, although did lose lock right at the end of the matrix transition.  This lockloss had a DARM oscillation a little lower, closer to 14 Hz.

There is some data-getting issue, but once that gets solved Oli plans to try re-running the lockloss tool so we can see if there is anything else suggestive of why we might have struggled. 

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