Comparing Visibility of OMC and HOM content after alignment change of SR2 and SR3

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.

Thurs EVE Ops Summary

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

H1 Back To Observing: No-Squeezing Configuration

Unfortunately, the Squeezer was not able to lock this evening.  In addition to the TTFSS issue from this week, the SHG could only stay locked for a few seconds at a time this evening (see attached screenshot), and we have the SQZ ISS Pump off as well.

• DIAG_MAIN gives this message:  "SQUEEZING:  ISS Pump is off.  See alog 70050."
  • Tried following the steps in this alog, but had no luck getting 
• So, to get us through the night, ended up transitioning H1 to the No-Squeezing configuration.  But even with that, had an issue with getting the SQZ Manager & SQZ LO_LR nodes to their NOMINAL states.  Luckily Vicky checked in on me and was able to ultimately find the issue (I believe she said a checker for SQZ_LO_LR was getting a FALSE due to the issue with the TTFSS.  So she edited the script to output a true and H1 was finally able to get to Observing at NLN +No Squeezing.
• Attached are SDF diffs from this round of taking H1 to No Squeezing.

pump polarization adjusted, TTFSS beatnote threshold decreased again, Squeezer seems like it should be OK

The pump ISS would not lock, it seems that the pump rejected polarization in HAM7 has been trending upward for 10days.  I adjusted the half and quarter wave plates at the input of the fiber and got the rejected power down to 23 uW, with 22mW launched into the fiber.  This probably could have been better adjusted, but each time I moved the pico I was having to wait for the PMC and SHG to relock so I decided this is good enough for tonight.

The second attached screenshot shows some trends related to the beatnote dropping.  The powers into the box all say they have been stable, and the power on the beatnote PD also seems stable,  so I'm not sure why the reported beatnote strength is falling.  The current beatnote level does seem like it's enough for the TTFSS to lock without an issue.  I've reset the lower limit to -50, and right now the beatnote strength is increasing again to -7dBm. 

It seem like if the IFO get relocked the squeezer should work, so this would be better than no squeezing for tonight.

Mid-Shift Status (thurs night)

The TTFSS beatnote continued a nosedive this afternoon/evening.  Fearing the remedy for this was a hardware fix tomorrow, I opted to prepare to take H1 to a No-Squeezing state, but during my preparations, H1 was dropped out of Observing for a different SQZ reason.  At this point, I stayed out of observing and focused on following the procedure for No-Squeezing operations.  I mostly was there, but there were still issues with the SQZ MANAGER and SQZ LO LR nodes not making it to their "No Squeezing" nominal states (i.e. they had orange boxes).  At this point I phoned TJ (per No-Squeezing wiki instructions), but Sheila also connecting with me via mattermost.  

Sheila has thinks Squeezing should work and is working on that.  

I am currently working on H1 because at 409utc (909pmPDT), H1 lost lock.

SQZ TTFSS Beatnote Drops H1 Out Of OBSERVING Again

H1 was taken out of Observing due to SQZ TTFSS Beatnote continuing to drop (even after the TTFSS box was swapped this afternoon [alog77734]).  Lowered the Beatnoe RF Minimum from -12 to -20 to give us a few hours.

SDF with new minimum accepted (see screenshot of SDF, trend of beatnote since the Tues & today TTFSS swaps, and TTFSS medm).

Annual LN2 dewar jacket pumpdown report

The annual dewar jacket pumpdown - which is now part of the annual LN2 maintenance FAMIS task - is now complete, the pressures, and the pumpdown completion dates are the following:

- CP1 (corner): 04/24: 8 mTorr
- CP2 (corner): 05/26: 5 mTorr
- CP7 (EY): 04/30: 4 mTorr
- CP8 (EX): 04/26: 6 mTorr
- CP3 (MY): 05/03: 4 mTorr
- CP4 (MY): N/A (decommissioned)
- CP5 (MX): 05/08: 4 mTorr
- CP6 (MX): 05/08: 4 mTorr

Measured position on PR2, PRM

Robert and Anamaria found that there are some stray beams in HAM3 (alog 77631).  As part of understanding where that could be coming from, Anamaria suggested measuring our position on PR2.  TL;DR: we're the same 15mm off center in yaw that we have been, but now maybe we're starting to realize that it's too much.

Throughout O4, it looks like we've measured the beam position on PR2 three times (including today).  April 2023 (alog 690225), Dec 2023 (alog 74789), and today (this alog). 

As with the previos times, changing the PR2 A2L coefficients doesn't really seem to effect the line height in DARM, but I can reduce it in PRCL_CTRL.  I didn't confirm that PRCL_IN1 agrees on minimum line height with PRCL_CTRL, but I don't have reason to guess that they'd be different from one another.  Today I used 29 Hz, with a line amplitude of 1 in the ADS oscillator.  This made  a line in DARM about 100x above the ambient for the pitch excitation (maybe a little less than that for the yaw excitation).  Also, the peak in DARM seemed quite broad, with upconversion wings around it, more than I expected.  I don't recall seeing such strong upconversion when doing this similar measurement recently in alog 77443.

I also measured the spot position on PRM, again with a 1 count amplitude at 29 Hz.  The peak in DARM was much less broad than it was for the PR2 excitations. PRM started with no A2L gains at all. 

All of my fine-tuning step sizes today were at the level of 0.03 (which is 3x smaller than my SR2/SRM steps a few weeks ago). So, indeed the PRC optics seem a little more sensitive to A2L coefficients. I left both PR2 and PRM with the coefficients I measured today. 

	PRCL_CTRL reduction factor	Start A2L gain	End A2L gain	Start inferred position [mm]	End inferred position [mm]	Difference in beam position [mm]
PR2 P2L	10x	-0.61	-0.38	-1.2	-0.8	+0.3
PR2 Y2L	very little	-7.40	-7.45	-14.9	-15.0	-0.1
PRM P2L	~3.5x	0	1.76	unmeasured	3.5	N/A
PRM Y2L	5x	0	0.52	unmeasured	1.0	N/A

Talking through numbers out loud with TJ, Corey, and Oli, and looking at D1002640 which shows the 70mm aperture size that Minhyo quotes in alog 77637, it sure seems like this is a plausible explination for the source of the light that Anamaria and Robert found. If the beam is off center on PR2 and the baffle by about 15 mm, and then 15mm away from that is the point at which, if we were clipping, we'd see a few tens of mW clipped, that clipping point total of 30 mm is starting to sound suspiciously similar to the baffle aperture radius of 35 mm. 

This motivates that perhaps we really should consider trying to get closer to center on PR2. So far we haven't done so, because there are lots of alignment follow-ons that would also need to happen for the leakage beams in transmission of PR2 (eg ALS to ISCT1, POP ASC beams, POP LSC beams).  But, the only one of those that we actually need in full lock is the LSC POP, so we could make some moves and as long as we're staying on LSC POP, we could see if that improves things enough to motivate making a new alignment permanent (and doing all the follow-on not-easily-reversible alignments).

Ops Day Shift End

TITLE: 05/09 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Observing at 154Mpc
INCOMING OPERATOR: Corey
SHIFT SUMMARY: Commissioning time this morning and two brief out of Observing times this afternoon to fix the SQZ TTFS box. Other than that it has been straight forward today. Locked for 13 hours.
LOG:

• 1600 Commissioning start
• 1858 Observing
• 19250-1958 Briefly out of Observing to fix SQZ fiber TTFSS issue.
• 2223-2254 Briefly out of Observing to swap TTFSS SQZ box

Start Time	System	Name	Location	Lazer_Haz	Task	Time End
15:28	SQZ	Terry, Kar Meng	Opt Lab	local	SHG work	19:28
15:55	FAC	Karen	Opt Lab	-	Tech clean	17:55
17:25	CDS	Fil	Ends, Mids	n	Look at/for equipment	19:25
17:56	VAC	Janos	FCES	n	Grabbing data in receiving area	18:24
18:31	ISC	Sheila	LVEA	n	Plug in excitation at PSL racks	18:51
21:45	SQZ	Terry, Kar Meng	Opt Lab	local	SHG work	22:13
22:27	PCAL	Dripta, Francisco	PCAL lab	local	PCAL work	23:12
22:36	SQZ	Fil	LVEA	local	Swap TTFSS box	22:51

Thurs EVE Ops Transition

TITLE: 05/09 Eve Shift: 2300-0800 UTC (1600-0100 PST), all times posted in UTC
STATE of H1: Observing at 153Mpc
OUTGOING OPERATOR: TJ
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 20mph Gusts, 16mph 5min avg
    Primary useism: 0.05 μm/s
    Secondary useism: 0.13 μm/s
QUICK SUMMARY:

H1 had just come back into Observing by TJ as I walked in (w/ H1 locked 13hrs).  Not much else to pass off from TJ (he mentioned LLO have been recovering from a power glitch most of today...but there  are signs of life from L1!).  Winds have steadily increased over last 8hrs with gusts touching 25mph now (but forecast has calm-down after sunset).  Microseism continues a slow trend down to/below the 50th percentile.

Briefly out of Observing 1950-1958UTC to fix SQZ TTFSS issue

The SQZ fiber beatnote has been dropping since the new box was installed this past Tuesday. It dropped below threshold and the autolocker turned off, but held lock. Sheila bumped this min dB to -14 for now, but we will talk with Fil about replacing that box soon since it doesn't look OK. See second attachment.

check of AS_A yaw offset

In March, Louis and Gabriele found an AS_A yaw offset that reduced the coupling of DHARD Y to DARM (76407)   We've been running with this offset since.

Today I quickly checked that this is still the offset that minimizes the coupling, it still is close to the right offset.

Thu CP1 Fill

Thu May 09 10:10:18 2024 INFO: Fill completed in 10min 14secs

Jordan confirmed a good fill curbside.

SRCL feedforward depends on DHARD P offset

Gabriele looked at the nonstationarity of the SRCL coupling in 77666, and proposed DHARD P as a degree of freedom that could be responsible. 

This morning I measured the SRCL to DARM transfer function with and without a small offset in the DHARD P error point.  I chose an offset of 10 counts which is about the rms of the DHARD P error signal (spectrum attached). This changed the coupling from SRCL to DARM (with the feedforward on) by 20%.  So indeed it seems that we need to reduce the RMS of the DHARD P loop to have a stationary SRCL coupling.

Excitation with offset on: 5/9/24 16:16:52 UTC - 16:20:39 UTC  with offset off we took a longer stretch of data in case it is useful to look at: 16:21:47-16:34:18 UTC.

Out of Observing at 1600UTC for planned commissioning

Out from 1600-1900UTC (9-12PT).

Re-finding old A2L scripts that look at peak height

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.

 

 

OMC Scans to investigate possible OFI bad throughput

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...