Elenna, Sheila, Oli

I've added thermalization ramping for the PRCL2 gain so that it ramps from 1.0 to 1.9 over the first 75 minutes at max power. The 'unthermalized' (1.0) and 'thermalized' (1.9) values are taken from lscparams in the new dictionary 'prcl2_gain', so any changes to be made in the future to those values should be set in that dictionary, and then the THERMALIZATION guardian reloaded so that it grabs those new values.

This addition is pretty much a copy of the way we ramp the SRCL offset, but for PRCL gain of course..

This change to the THERMALIZATION guardian as well as the dictionary addition to lscparams have been committed to svn as r32157.

We continue to have 13 Hz ringups in the LSC that cause locklosses, so I took at look at what's going on with PRCL (it's the usual culprit). I measured the OLG every few minutes after we reached NLN. I found that PRCL loses a factor of 2 gain over the first 40 minutes of NLN. The current design is set to have PRCL with a UGF of 30 Hz once the gain settles after thermalization. However, this leads to >10 dB gain peaking at the start of the lock. There's overall not a lot of phase in the loop design, and if the gain gets too low this is causing the locklosses.

I looked at the loop design, and reminded myself of Gabriele's intentions with the PRCL redesign, here. His design applied the Dcntrl filter, which means to go back to the old design we only have to disengage this filter. You can see from the design comparison in his alog that the original design has a much broader phase. We might inject more noise by going back to the old design, but I'm not sure that will be an issue, especially if we continue to run the PRCL feedforward.

Turning off the Dcntrl filter gives more phase at high frequency, meaning we can increase the PRCL UGF. I increased the PRCL2 gain to 1.9 and got a UGF of 50 Hz, with about 35 deg phase. If we don't change this gain at all, PRCL will start in the lock with a UGF of 100 Hz and a phase margin of 18 degrees if the digital gain is always set to 1.9. This will then thermalize down to 50 Hz.

I also disengaged the 3.4 Hz resgain filter, because we no longer need to suppress motion at that frequency, and hopefully we'll get back a little more phase at low frequency as well.

Oli is reworking the thermalization guardian to ramp the PRCL2 gain from 1 to 1.9 over the first hour, starting after we reach max power.

I commented out the lines in lownoise_length_control that change the PRCL shape and loop gain.

I checked the PRCL noise injection with the feedforward template, and there slightly more noise injection from 20-30 Hz, but I'm not sure that's a problem.

I updated the SDF for the filter changes, and to unmonitor H1:LSC-PRCL2_GAIN since the guardian will now update that gain.

Plot 1 shows the evolution of PRCL olg with the 30 Hz UGF design, Plot 2 shows the evolution of the loop suppression

Plot 3 and Plot 4 show the OLG and loop suppression respectively with the 50 Hz UGF design

Plot 5 compares a PRCL coupling measurement from last week with today.

1435343011

It will probably register as an IMC lockloss, just wanted to make sure people know it was caused by an injection.

18:23 UTC lockloss alog85433

Mon Jun 30 10:12:57 2025 INFO: Fill completed in 12min 53secs

M. Todd, R. Crouch, E. Capote, S. Dwyer

After 5 minutes or so from stepping the CO2 lasers from 1.7W to 0.9W, we began to see the 13Hz ring-up again before losing lock.

We believe this to be PRCL losing gain because of the change in the CO2s. I'm also wondering if the CO2s may be miscentered and causing some roll modes via differential heating of the fibers -- the frequenices do not exactly match up I think but need to check on this.

15:40 UTC lockloss while we were running the CO2 stepper. alog85429

I ran the DARM offset stepping script using Jennie Wright's instructions from 85136.

Writing data to
/ligo/gitcommon/labutils/darm_offset_step/data/darm_offset_steps_2025_Jun_30_15_06_50_UTC.txt

TITLE: 06/30 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Observing at 145Mpc
OUTGOING OPERATOR: Ryan S
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 8mph Gusts, 4mph 3min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.07 μm/s
QUICK SUMMARY:

• We've been locked for just udner 19 hours
  • SQZing doesn't look the best, particularly at high frequency
• Low wind, secondary microseism is starting to creep up a little
• PI24 rang up 6 times overnight, but was damped
• Commissioning is planned from 15:00 - 19:00 UTC today

FRS34130

Upgrading Pylon on h1digivideo[4,5,6] has fixed the problem whereby camera processes continued to open files until they eventually reached the OS num_files limit and the camera crashed (new files were opened each time connection to the camera was restored, old files were not cleaned up).

Since the upgrade Tuesday 24 June 2025 the number of files open per process has remained static. Details in FRS, this ticket has been closed.

TITLE: 06/30 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Observing at 146Mpc
INCOMING OPERATOR: Ryan S
SHIFT SUMMARY:

IFO is in NLN and OBSERVING since 19:42 UTC (9 hr lock!)

An extremely calm shift in which the circumstancial lock-killing culprits of the world evidently and collectively decided to take a nap. In other words, there have been no earthquakes, the secondary microseism is as low as can be, wind is under 10mph, no SQZ locklosses, no ETM LLs.

The only thing worth commenting on is that the SQZ angle is probably not ideal but according to past instructions from Sheila, we shouldn't go to comissioning if there are other IFOs observing. Since this was the case the entire shift, I did not drop out to try and optimize SQZ so this will have to wait till tomorrow/another lock.

LOG:

None

Link to DQ Shift Summary

• The duty cycle for this week was 54.9%
• h(t) spectrograms were showing continuous high amplitude noise around 140Hz for all the days. 
• Seismic, wind and ground motion remained relatively low with some occasional exceptions being here and there, which cause noise in the PEMs. 
• Glitchgram showed large amount of high SNR glitches for some days with increase in glitch rate. 
• Corner BSC2 [Y[ chamber experience very high amplitude noise at below 10 hz continuously for all days. 
• FScan plots were available except for Sunday, June 29 with the line count remaining at around 2400 well below the threshold.

TITLE: 06/29 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Observing at 146Mpc
OUTGOING OPERATOR: Ryan C
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 12mph Gusts, 5mph 3min avg
    Primary useism: 0.03 μm/s
    Secondary useism: 0.05 μm/s
QUICK SUMMARY:

IFO is in NLN and OBSERVING since 19:42 UTC (3.5 hr lock)

Ryan C reports a very calm shift with the only comment that he had to run 2x initial alignments. I had to do this also a few days ago despite good DRMI flashes.

TITLE: 06/29 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Observing at 146Mpc
INCOMING OPERATOR: Ibrahim
SHIFT SUMMARY: One lockloss, I had to run 2 alignments to get DRMI to lock.
LOG: No log.

• 16:25 UTC PI24 rang up but was successfully damped back down.
• 16:38 UTC lockloss
  • 17:16 UTC I ran an alignment after not being able to get PRMI
  • Still couldn't lock DRMI or PRMI despite having good flashes around 100
  • 18:32 UTC trying another alignment
  • DRMI locked quickly now, I also adjusted the OPO temp while relocking
  • 19:42 UTC Observing

Sun Jun 29 10:13:36 2025 INFO: Fill completed in 13min 32secs

16:38 UTC lockloss

Oli, Elenna

Oli and I combed through some of the recent locklosses by hand, and noticed that there are at least two that have a 13 Hz oscillation in the LSC channels just before the lockloss.

1434317297

1434276630

This is reminiscent to us of PRCL losing gain due to thermalization which has caused 11 Hz ring ups before. We should keep an eye out. Note that one of the above locklosses has the "earthquake" tag, but it's very clear that the ring up caused the lockloss.

Oli and I went back about 1 week and checked the NLN locklosses by eye and only found these two so far.

To start, we can periodically check PRCL OLG or other LSC OLGs during thermalization to make sure we aren't losing significant optical gain. Or we can inject a line during commissioning.