Displaying reports 15221-15240 of 86496.Go to page Start 758 759 760 761 762 763 764 765 766 End
Reports until 11:19, Thursday 12 October 2023
H1 SQZ (ISC)
regina.lee@LIGO.ORG - posted 11:19, Thursday 12 October 2023 - last comment - 19:13, Friday 22 December 2023(73400)
Squeeze Data with PSAMS ZM4/5 at 120/120V

Vicky, Regina, Naoki, Sheila 

We took squeeze data with PSAMs on ZM4 and ZM5 both at 120V, and four squeeze angles. Summary screenshot here, with these trends of squeezed BLRMS. All of the following data was done with frequency dependent squeezing. 

With ZM4/5 at 120/120 V, +/- mid squeeze have noticibly different misrotations across the band. In alog 71902 from Aug. 2 with PSAMS at 200/200V, we didn't see strong misrotations down to ~80 Hz. From FDS data on Aug 2, compare today's green/blue lines to the green and yellow +/- mid squeeze lines in this plot.

DTT saved at $(userapps)/sqz/h1/Templates/dtt/DARM/PSAMS_tests_Oct112023.xml

Images attached to this report
Comments related to this report
regina.lee@LIGO.ORG - 19:32, Wednesday 11 October 2023 (73405)

For reference, with ZM4/5 PSAMS at 200/200V (what we've been operating with in O4). 

H1:AWC-ZM4_PSAMS_STRAIN_VOLTAGE 7.52377
H1:AWC-ZM4_PSAMS_DEFOCUS_MON_MDIOPTER 201.544
H1:AWC-ZM5_PSAMS_STRAIN_VOLTAGE 3.49813
H1:AWC-ZM5_PSAMS_DEFOCUS_MON_MDIOPTER -1030.69

victoriaa.xu@LIGO.ORG - 22:05, Wednesday 11 October 2023 (73408)

I took more data with PSAMS ZM4/5 = 200V/200V, using the same injected sqz angles as above.

See comparisons of anti-squeezing and squeezing with PSAMS @ 200/200V (dotted lines) vs. 120/120V (solid lines).

  • This dataset started about 35 min after NLN, so not totally thermalized yet.
  • -mid sqz (600 sec) 
    • Start: 1381116279
    • Phase demod at +32 degrees
  • +mid sqz (600 sec)
    • Start: 1381117087
    • Phase demod at +200 degrees
  • Anti sqz (600 sec)
    • Start: 1381117845
    • Phase demod +241.91 degrees
  • No Sqz (600 sec)
    • Start: 1381118732
  • Sqz (600++ sec), back in observing
    • Start: 1381120124
    • Phase demod +150 degrees

Notes / thoughts:

  • Unsqueezed DARM looks comparable before and now. Compare end of this dataset (black) with start of the last dataset (red). A bit quieter now below 40 Hz.
  • Maybe more anti-squeezing at kHz (upper pink vs. black). Played with sqz angles, did not get more anti-sqz than the same +242deg angle.
    • From SQZ-OMC mode scans with cold OM2 (e.g. Jan 2023, LHO:66946) and maximizing ADF-OMC transmission (e.g. July 2023, LHO:71270), I thought it suggests that 200/200V improves SQZ-OMC mode matching. Still leaves SQZ-IFO mode-matching unconstrained. I have not thought about anything relatd to mismatch phases. But if PSAMS 200/200 is minimizing a mismatch that introduces loss, that could be consistent with 200/200 giving more anti-squeezing at >kHz?
  • SQZ might be flatter with 200/200V?

BLRMS trends here. All traces saved to same DTT file, $(userapps)/sqz/h1/Templates/dtt/DARM/PSAMS_tests_Oct112023.xml

Images attached to this comment
regina.lee@LIGO.ORG - 15:11, Thursday 12 October 2023 (73425)

Vicky, Sheila, Regina, Dorotea

We followed up by checking ZM Sliders to see if there is misalignment with different PSAMS was a factor in addition to the mode mismatches from changing PSAMS. There seems to be a large static alignment shift from changing PSAMS, we're not sure if it is fully compensated by ASC especially in yaw. We might do more measurements tomorrow to follow up. 

Squeezing ZM4/ZM5 Voltage Demod Phase (deg) ZM4 P ZM4 Y ZM5 P ZM5 Y ZM6 P ZM6 Y
+Mid SQZ 120/120 +200 -41 255 -176 339 780 805
+Mid SQZ 200/200 +200 -9.5 254 -241 439 807* 801*
-Mid SQZ 120/120 +32 -12 257 -176 351 753 793
-Mid SQZ 200/200 +32 -9.6 254 -244 450 792 790
ASQZ 120/120 +242 -41 257 -165 343 765 792
ASQZ 200/200 +242 -9.55 254 -238 439 843 787
FDS 120/120 +150 -41 257 -177 391 756 797
FDS 200/200 +150 -9.48 254 -244 446 800 789

*+Mid SQZ: ZM6 was not flat for the 200/200 squeezing. It was increasing in P and Y for +Mid SQZ, didn't seem to reach the steady state. It seems like the ASC is keeping up better with 120/120 because the angles converged, whereas the angles of ZM5 and ZM6 for the 200/200 case kept increasing and did not reach steady state in the time given. 

ASQZ: ZM5 pitch for 120/120 has some shaking, ZM6 pitch is rising and yaw is dropping

Images attached to this comment
H1 General (DetChar)
max.trevor@LIGO.ORG - posted 10:50, Thursday 12 October 2023 (73418)
DetChar DQ Shift Report: Oct 2 to Oct 8
Full DQ shift report is at: https://wiki.ligo.org/DetChar/DataQuality/DQShiftLHO20231002
Overall a relatively uneventful week.
Range frequently stable around 150 Mpc with some drops down to 140
Found that hveto was looking at unsafe channels to generate vetos, should be fixed now
Some safe channels also found by hveto as good witnesses:
    H1:PEM-EX_EFM_BSC9_ETMX_Y_OUT_DQ
    H1:SUS-ETMX_L3_OPLEV_PIT_OUT_DQ
    H1:SUS-ETMX_L3_OPLEV_YAW_OUT_DQ

Glitches continue to be problematic, much higher glitch rate than L1.
Some of the glitches most affecting the PyCBC search have werd morphologies
Images attached to this report
LHO VE
david.barker@LIGO.ORG - posted 10:43, Thursday 12 October 2023 (73417)
Thu CP1 Fill

Thu Oct 12 10:11:05 2023 INFO: Fill completed in 11min 1secs

Jordan confirmed a good fill curbside.

Images attached to this report
H1 SEI
oli.patane@LIGO.ORG - posted 08:49, Thursday 12 October 2023 (73415)
SEI Seismometer Mass Position Check - Monthly

Closes FAMIS#26482, last checked 72639

check_T240_centering.py - 2023-10-12 08:41:09.262244

There are 12 T240 proof masses out of range ( > 0.3 [V] )!
ETMX T240 2 DOF X/U = -0.918 [V]
ETMX T240 2 DOF Y/V = -1.076 [V]
ETMX T240 2 DOF Z/W = -0.32 [V]
ITMX T240 1 DOF X/U = -0.87 [V]
ITMX T240 1 DOF Z/W = 0.428 [V]
ITMX T240 3 DOF X/U = -0.842 [V]
ITMY T240 3 DOF X/U = -0.56 [V]
ITMY T240 3 DOF Z/W = -1.111 [V]
BS T240 1 DOF Y/V = -0.456 [V]
BS T240 3 DOF Y/V = -0.358 [V]
BS T240 3 DOF Z/W = -0.573 [V]
HAM8 1 DOF Z/W = -0.306 [V]

All other proof masses are within range ( < 0.3 [V] ):
ETMX T240 1 DOF X/U = 0.219 [V]
ETMX T240 1 DOF Y/V = 0.125 [V]
ETMX T240 1 DOF Z/W = 0.152 [V]
ETMX T240 3 DOF X/U = 0.1 [V]
ETMX T240 3 DOF Y/V = 0.114 [V]
ETMX T240 3 DOF Z/W = 0.097 [V]
ETMY T240 1 DOF X/U = -0.013 [V]
ETMY T240 1 DOF Y/V = 0.058 [V]
ETMY T240 1 DOF Z/W = 0.124 [V]
ETMY T240 2 DOF X/U = -0.082 [V]
ETMY T240 2 DOF Y/V = 0.146 [V]
ETMY T240 2 DOF Z/W = 0.028 [V]
ETMY T240 3 DOF X/U = 0.128 [V]
ETMY T240 3 DOF Y/V = 0.002 [V]
ETMY T240 3 DOF Z/W = 0.09 [V]
ITMX T240 1 DOF Y/V = 0.267 [V]
ITMX T240 2 DOF X/U = 0.086 [V]
ITMX T240 2 DOF Y/V = 0.217 [V]
ITMX T240 2 DOF Z/W = 0.188 [V]
ITMX T240 3 DOF Y/V = 0.107 [V]
ITMX T240 3 DOF Z/W = 0.112 [V]
ITMY T240 1 DOF X/U = 0.068 [V]
ITMY T240 1 DOF Y/V = -0.008 [V]
ITMY T240 1 DOF Z/W = -0.14 [V]
ITMY T240 2 DOF X/U = 0.061 [V]
ITMY T240 2 DOF Y/V = 0.13 [V]
ITMY T240 2 DOF Z/W = 0.014 [V]
ITMY T240 3 DOF Y/V = 0.039 [V]
BS T240 1 DOF X/U = -0.225 [V]
BS T240 1 DOF Z/W = -0.009 [V]
BS T240 2 DOF X/U = -0.184 [V]
BS T240 2 DOF Y/V = -0.084 [V]
BS T240 2 DOF Z/W = -0.226 [V]
BS T240 3 DOF X/U = -0.295 [V]
HAM8 1 DOF X/U = -0.131 [V]
HAM8 1 DOF Y/V = -0.094 [V]

check_sts_centering.py - 2023-10-12 08:43:32.265464

There are 2 STS proof masses out of range ( > 2.0 [V] )!
STS EY DOF X/U = -4.106 [V]
STS EY DOF Z/W = 2.601 [V]

All other proof masses are within range ( < 2.0 [V] ):
STS A DOF X/U = -0.614 [V]
STS A DOF Y/V = -0.874 [V]
STS A DOF Z/W = -0.437 [V]
STS B DOF X/U = 0.519 [V]
STS B DOF Y/V = 0.874 [V]
STS B DOF Z/W = -0.547 [V]
STS C DOF X/U = -0.365 [V]
STS C DOF Y/V = 0.808 [V]
STS C DOF Z/W = 0.217 [V]
STS EX DOF X/U = -0.246 [V]
STS EX DOF Y/V = 0.01 [V]
STS EX DOF Z/W = 0.059 [V]
STS EY DOF Y/V = 0.13 [V]
STS FC DOF X/U = 0.4 [V]
STS FC DOF Y/V = -0.74 [V]
STS FC DOF Z/W = 0.793 [V]

H1 PSL
oli.patane@LIGO.ORG - posted 08:34, Thursday 12 October 2023 (73414)
PSL Status Report - Weekly

Closes FAMIS#26212, last checked 73167

Everything looking good besides ISS diffracted power low


Laser Status:
    NPRO output power is 1.822W (nominal ~2W)
    AMP1 output power is 67.6W (nominal ~70W)
    AMP2 output power is 136.1W (nominal 135-140W)
    NPRO watchdog is GREEN
    AMP1 watchdog is GREEN
    AMP2 watchdog is GREEN

PMC:
    It has been locked 20 days, 1 hr 15 minutes
    Reflected power = 16.57W
    Transmitted power = 109.4W
    PowerSum = 125.9W

FSS:
    It has been locked for 0 days 10 hr and 20 min
    TPD[V] = 0.7294V

ISS:
    The diffracted power is around 1.7%
    Last saturation event was 0 days 10 hours and 20 minutes ago


Possible Issues:
    ISS diffracted power is low

LHO General
thomas.shaffer@LIGO.ORG - posted 08:04, Thursday 12 October 2023 (73413)
Ops Day Shift Start

TITLE: 10/12 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Observing at 150Mpc
OUTGOING OPERATOR: Ibrahim
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 3mph Gusts, 2mph 5min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.21 μm/s
QUICK SUMMARY: Locked for 9 hours, useism trending down to good levels.

CDS Overview OK, no alarms

DIAG_MAIN - ITMY HWS code has stopped

LHO General (TCS)
ryan.short@LIGO.ORG - posted 00:00, Thursday 12 October 2023 (73411)
Ops Eve Shift Summary

TITLE: 10/12 Eve Shift: 23:00-07:00 UTC (16:00-00:00 PST), all times posted in UTC
STATE of H1: Observing at 148Mpc
INCOMING OPERATOR: Ibrahim
SHIFT SUMMARY: Two mystery locklosses with some opportunistic commissioning activities interspersed throughout the shift since L1 has been down.

HWS ITMX code is stopped and has been for the majority of this shift, tagging TCS.

LOG:

Start Time System Name Location Lazer_Haz Task Time End
23:48 PEM Robert CER - Adjust PSL chassis grounding 23:57
00:28 SQZ Vicky, Naoki, Regina CR - SQZ tests 01:57
H1 General (Lockloss)
ryan.short@LIGO.ORG - posted 22:19, Wednesday 11 October 2023 - last comment - 23:07, Wednesday 11 October 2023(73410)
Lockloss @ 05:10 UTC

Lockloss @ 05:10 UTC - no immediately obvious cause. Another quick lockloss, no DCPD saturation this time.

Images attached to this report
Comments related to this report
ryan.short@LIGO.ORG - 23:07, Wednesday 11 October 2023 (73412)

Back to observing at 06:04 UTC

H1 General (DetChar)
ryan.short@LIGO.ORG - posted 21:56, Wednesday 11 October 2023 (73409)
H1 Out of Observing for Opportunistic SQZ Tests

While L1 was down this evening, H1 dropped out of observing between 03:23 and 04:26 UTC to opportunistically continue SQZ tests (see alog 73408).

Tagging DetChar: although gwistat reported H1 was "Ready" for much of this time (where the GDS range was being computed since we could have flipped the intent bit to start observing), H1 was not observing between 03:23 UTC and 04:26 UTC for commissioning time.

LHO General
ryan.short@LIGO.ORG - posted 20:00, Wednesday 11 October 2023 (73406)
Ops Eve Mid Shift Report

H1 has just started observing at 146Mpc as of 02:54 UTC.

There's a M5.5 earthquake coming in from Alaska, so hopefully we can hold on through the rest of the evening.

H1 General (Lockloss)
ryan.short@LIGO.ORG - posted 18:56, Wednesday 11 October 2023 - last comment - 20:01, Wednesday 11 October 2023(73404)
Lockloss @ 01:50 UTC

Lockloss @ 01:50 UTC - no immediately obvious cause, happened quickly with a DCPD saturation.

H1 had reached NLN at 23:52 UTC and resumed with commissioning since L1 was not locked. There were SQZ-related tests being run at this time, but it's very unlikely they were the cause of this lockloss.

Comments related to this report
ryan.short@LIGO.ORG - 20:01, Wednesday 11 October 2023 (73407)

Back to observing at 02:54 UTC.

H1 PEM (DetChar)
robert.schofield@LIGO.ORG - posted 18:36, Wednesday 11 October 2023 (73403)
Broad 120 Hz peak no longer in DARM after PSL periscope tuning and shutdown of SF2

On Tuesday I tuned the periscope in the PSL by adjusting weights and Tyler and I shut down SF2, which was responsible for the new 120 Hz HVAC peak ( https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=73378 ). Figure 1 shows the reduction of the periscope peak from tuning, and from tuning plus the fan shutdown. The fan shutdown had the greatest effect.

Figure 2 shows the disappearance of the peak from the summary pages, as well as the 3+ MPc increase in range from the fan change only.

Non-image files attached to this report
H1 PEM
robert.schofield@LIGO.ORG - posted 18:07, Wednesday 11 October 2023 (73402)
Inconclusive search for 13.1 Hz source during commissioning time today

During commissioning today I looked for the source of the 13.1 Hz harmonics that began to appear on Oct. 3, by testing some of the things that were done that Tuesday. First  I temporarily shut down the DC-DC converter and oplev laser for ITMX that had been worked on. But the noise, likely from the very high microseism, made my tests inconclusive. I also tried disconnecting the new grounding on the TCS and PSL chassis. Since DARM noise was too high for me to tell if this helped, I have left them disconnected and will reconnect the grounds when we can tell that they are not part of the problem.

H1 CDS
david.barker@LIGO.ORG - posted 16:54, Wednesday 11 October 2023 - last comment - 17:12, Wednesday 11 October 2023(73399)
Disk issue on h1hwsmsr

Camilla, Jonathan, Dave:

h1hwsmsr had issues this afternoon, and then got stuck on reboot. Jonathan looked at the console and found it was reporting a SMART error on its hard disk drive. We will schedule a replacement.

Jonathan manually progressed the boot past this point and Camilla restarted the code. The EDC was disconnected from its 88 HWS ITMX channels between 16:15 - 16:48 PDT.

Comments related to this report
ryan.short@LIGO.ORG - 17:12, Wednesday 11 October 2023 (73401)TCS

Shortly after h1hwsmsr was restarted and the HWS code resumed, the HWS ITMX code stopped again.

There were also several SDF differences that I am assuming are from the computer being restarted (attached). These have been REVERTED.

Images attached to this comment
H1 ISC
camilla.compton@LIGO.ORG - posted 14:52, Wednesday 11 October 2023 - last comment - 16:21, Wednesday 11 October 2023(73393)
MICH and SRCL LSC FF Remeasured

Camilla, Jenne. Started in 73345. H1 had been locked ~5 hours.

Didn't exactly follow instructions in lsc/h1/scripts/feedforward/README.md, as took residual measurements with no FF and took FF measurements with actuation through ETMY PUM rather than ETMX. 

Non-image files attached to this report
Comments related to this report
camilla.compton@LIGO.ORG - 16:21, Wednesday 11 October 2023 (73398)

Gabriele helped fit the filters and we saved them to MICHFF and SRCLFF as 10-11-23-EY. 

H1 SQZ
sheila.dwyer@LIGO.ORG - posted 14:03, Tuesday 10 October 2023 - last comment - 18:31, Tuesday 17 October 2023(73365)
homodyne measurements today

Vicky, Sheila, Camilla, Dorotea, Naoki

We went to SQZT7 this morning with the new homodyne (73241).  In the end we wer able to see decently flat shot noise and decent visibility.  On the way, we ran into some difficulties that caused some confusion:

In the end we have flat shot noise, and a visibility of 98.5% measured on PDA (3.07% loss) and visibility of 97.8% (4.44% loss) measured on PDB.  The nonlinear gain of 11 measured with seed max/ no pump. A comment to this alog will contain the measured sqz/asqz/mean sqz.

Comments related to this report
victoriaa.xu@LIGO.ORG - 13:47, Wednesday 11 October 2023 (73376)

Screenshot summarizing homodyne measurements today. With measured carrier NLG=11 (for generated squeezing ~14.7-14.8 dB), we observe

  • squeezing           = - 6 dB
  • anti-squeezing    = +13.5 dB
  • mean-squeezing = +10.5 dB

Comparing sqz/anti-sqz to generated sqz: ~7% unexplained homodyne losses. This is consistent with our last estimate of excess HD losses (8/29/2023, LHO:72802, ~7% mystery loss). Since then, we swapped the HD detector and improved readout losses (visibility). We now measure more homodyne squeezing at 6 dB, consistent with expected loss reductions. That is compared to 8/29 (LHO:72802), we have less total loss, less budgeted hd loss && more squeezing, but the same unexplained hd losses as before.

Comparing mean-squeezing to generated sqz: could be consistent with sqz/asqz losses. I think there is a mis-estimate of the generated squeezing level from non-linear gain. If we ignore our NLG11 measurement, and instead use the generated squeezing level to match observed 13.5 dB of anti-squeezing, then we allow losses to determine the measured 6 dB squeezing level, we would have an NLG=10 (not 11) for a generated squeezing level of 14.5 dB. This would suggest 7% unexplained losses, same as the sqz/asqz measurements.

For ~7% mystery losses, this is compared to total HD losses of 21%, of which we budget 15% losses. From the sqz wiki, the budgeted losses are:

  • opo escape 98.5% 
  • in-chamber ham7 95.3%
  • beam diverter 99%
  • SQZT7 on-table optics losses 2% (72604)
  • HD PD QE 97.7%  (73241)
  • visibility 95.6%  (from 97.8% fringe visibility on PD B) 

If we include phase+dark noise that degrades squeezing but is not loss, then 21% total loss can explain the 6dB measured squeezing, see e.g. from the gsheet calculator (edited to include ranges for NLG=10 and NLG=11):

    SQZ   ASQZ
NLG                    10 - 11
x  (0.68, 0.70)  (0.68, 0.70)
gen sqz (dB)  (-14.5, -15.01)   (14.5, 15.01) 
with throughput eta =                       0.79
meas sqz (dB)  (-6.24, -6.29)  (13.54, 14.03) 
with phase noise (mrad) =                      20.00
meas sqz (dB)  (-6.08, -6.11)  (13.54, 14.03)
with dB(Vtech/Vshot) =                    -22.00
var(v_tech/v_shot)   0.0063   0.0063
meas sqz (dB)   (-5.97, -6.00)    (13.54, 14.03) 

DTT homodyne template saved at $userapps/sqz/h1/Templates/dtt/HD_SQZ/HD_SQZ_101023.xml .

Edited to include some history of homodyne measurements:

  • 6 dB SQZ -  10/10/23 LHO:73365 = 21% total loss, 15% known loss, 7% mystery (this time)
  • 5.2dB SQZ - 8/31/23, LHO:72802 = 27% total loss, 21% known loss, 7% mystery (bad PD-B QE, lower visibility?)
  • 5.5dB SQZ -   2/3/23, LHO:67219 = 25% total loss, 15% known losses, < 10% mystery (tech noise -10dB), NLG was varied.

It could still be interesting to vary NLG to see if we can obseve any more squeezing, or if an additional technical noise floor (aside from dark noise) is needed to explain the NLG sweeps.

Images attached to this comment
sheila.dwyer@LIGO.ORG - 17:02, Wednesday 11 October 2023 (73395)

We revised the sqz loss wiki table again today, and are including it to explain what we think our current understanding of losses is. 

It seems likely that the 7% extra losses we see on homodyne measurements are in HAM7, so we've nominally added that to the loss budget. 

In addition to this, there would be an additional 8% loss on the sqz beam if we didn't correct it's linear polarization with a half wave plate.  72604  At the time of the chamber close out, (65110) we measured throughput from HAM7 to HAM5 that would implies that two passes through the OFI were giving us 97.6% transmission, so this is not compatible with the polarization being wrong by this much.  We haven't included this as a loss in the loss budget because it seems incompatible with our measurement in chamber. 

The wiki currently lists the OMC transmission as 92%, and the PD QE as 98%.  The PD QE may be worse than this (see 61568), but measurements of the product of QE and OMC transmission for 00 mode seem to indicate that is in the range 90-92%, so this is close. 

With the infered losses of from the measured sqz/anti-sqz in the IFO, the plausible range of losses is 30-35%, we are using 32%.  With only known losses (including the values for OMC trans and PD QE), we have 14% unexplained loss. If we include the 7% apparent HAM7 losses, we have 9% unexplained losses in the IFO.  This does seem similar to the 8% polarization problem, but it would also include SQZ-OMC mode matching.  

Possible future scenarios:  We may be able to reduce the 7% HAM7 losses, and we may be able to swap the OMC to reduce those losses from 92% to 97%.  

  total efficiency resulting sqz measured without subtraction (technical noise -12dB below shot, 20mrad phase noise) if technical noise is 20dB below unsqueezed shot noise
fix HAM7 losses 0.73 4.4dB 5dB
swap OMC (92%-> 97%) 0.71 4.14dB 4.8dB
swap OMC and fix HAM7 losses 0.77 4.85dB 5.6dB
swap OMC, fix HAM7 losses, and fix 8% from polarization issue (if that is real) 0.84 5.83dB 6.8dB

These numbers come from the aoki equations that Vicky added to the google sheet here: gsheet

 

Images attached to this comment
victoriaa.xu@LIGO.ORG - 18:31, Tuesday 17 October 2023 (73537)

Don G. and Sheila have very likely resolved the homodyne polarization issue as being due to the SQZT7 periscope. So, the mis-polarization is likely not an issue for squeezing in the interferometer.

The sqz beam leaves HAM7 via reflection off the sqz beam diverter. From the latest CAD layout from Don, the outgoing reflected beam (blue) is ~75.58 degrees from global +X. The periscope re-directs the beam to travel along SQZT7, approximately along +Y. The CAD layout thus suggests that the SQZT7 periscope re-directs the beam in yaw (counter-clockwise) by an estimated 90 - 75.58 = 14.4 degrees

From recent homodyne measurements LHO:72604, of the sqz light leaving HAM7 and arriving on SQZT7, ~8% of the power was in the wrong polarization, this calculates to a ~16.5 degrees polarization misrotation. Compared to this 16.5 degree misrotatation we were searching for, the 14.4 degrees polarization rotation induced by the periscope image rotation can plausibly explain the misrotation.

Images attached to this comment
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