Displaying reports 48681-48700 of 85922.Go to page Start 2431 2432 2433 2434 2435 2436 2437 2438 2439 End
Reports until 01:55, Wednesday 23 August 2017
H1 General (CDS)
edmond.merilh@LIGO.ORG - posted 01:55, Wednesday 23 August 2017 - last comment - 02:05, Wednesday 23 August 2017(38319)
Restarting NUCs/FOMs

All times in UTC:

07:46 Nuc2 restarting

07:49Nuc3 restarting

07:56 Nuc6 restarting

07:57 Nuc5 restarting

08:05 Nuc4 doesn't seem to take the "Restart Command" going to try "Shutdown" and manually reboot.

08:16 Nuc1 restarting

08:32 Nuc0 restarting

Comments related to this report
edmond.merilh@LIGO.ORG - 02:05, Wednesday 23 August 2017 (38320)
Link

It seems LLO has now appeared on the graph. I guess I was a bit hasty. I do, however, have to go and turn off the symbols for each of the plots so that they look as they usually do. Perhaps I'm still not running the correct template?

H1 General
edmond.merilh@LIGO.ORG - posted 00:03, Wednesday 23 August 2017 (38318)
Shift Transition - Owl

TITLE: 08/23 Owl Shift: 07:00-15:00 UTC (00:00-08:00 PST), all times posted in UTC
STATE of H1: Observing at 49Mpc
OUTGOING OPERATOR: Jeff
CURRENT ENVIRONMENT:
    Wind: 5mph Gusts, 3mph 5min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.08 μm/s
QUICK SUMMARY:

 

H1 General
jeffrey.bartlett@LIGO.ORG - posted 00:01, Wednesday 23 August 2017 (38317)
Ops Evening Shift Summary
Ops Shift Log: 08/22/2017, Evening Shift 23:00 – 07:00 (16:00 - 00:00) Time - UTC (PT)
State of H1: Locked at NLN, 29.2w, 50.4Mpc  
Intent Bit: Observing
Support: Sheila, Corey
Incoming Operator: Ed
 
Shift Summary: Relock after maintenance and commissioning work. Corey did mini sweep (turned off lights in LVEA and checked the WAP was unplugged. After clearing a few SFD differences back into Observing mode.
Ran A2L script – Yaw is elevated to 0.9 coherence. Have not run repair script due to triple-coincident Observing.
No significant issues or occurrences during the shift.  
 
Activity Log: Time - UTC (PT)
23:00 (16:00) Take over from Corey
23:15 (16:15) Corey – Mini sweep (lights and WAP) of LVEA
23:22 (16:22) Locked at NLN – Turn over to commissioners
23:33 (16:33) Lockloss – Commissioning
00:19 (17:19) Locked at NLN
00:35 (17:35) Cleared SDF differences and back to Observing
00:36 (17:36) Damp PI Mode-28
00:46 (17:46) Damp PI Mode-27
01:45 (18:45) Turn off extra lights and secure the OSB doors
06:10 (23:10) Run A2L – Yaw elevated to 0.9 coherence  
07:00 (00:00) Turn over to Ed
H1 General
jeffrey.bartlett@LIGO.ORG - posted 20:08, Tuesday 22 August 2017 (38316)
Ops Evening Mid-Shift Summary 
   Relocked after maintenance and commissioning work finished, and back into triple coincident observing. No issues to report at this time.
LHO VE
kyle.ryan@LIGO.ORG - posted 19:22, Tuesday 22 August 2017 - last comment - 10:09, Sunday 27 August 2017(38315)
TMDS training session at X-end 
Rai W., Mike Z., Daniel S., Jeff K., Chandra R., Kyle R. 

Today the TMDS Gas Delivery Table was transported to the X-end VEA and set it up for operation.  The actual Surface Discharge Ionizer was mounted on a stand for today's demonstration purposes.  Nominally, it would be mounted to the dedicated TMDS port of BSC9's East Door.  The Vent/Purge air supply was ran and dry air supplied to the TMDS setup.  Prior to exposing the Ionizer to the conditioned air supply, the plumbing connection at the Ionizer was decoupled and connected to a test setup that facilitated the measurement of > 0.3 micron and > 0.5 micron particulate in the conditioned air. The air line was then re-coupled to the Ionizer.  An approximate 50/50 mix of Ethylene Glycol to Alcohol along with "chunks" of dry ice was used as a cold trap to the path.  

Rai W. gave an overview of the theory and a detailed tutorial as to the operation of the setup.  Daniel S. and Jeff K. noted details related to the ion production while Kyle R. and Chandra R. noted detail related to the vacuum related issues.  

The Ionizer setup performed satisfactorily (with caveats) at making comparable amounts of positive and negative ions.  

The plan now is to connect the Ionizer to BSC9 and perform an actual discharge of the ETMx during next Tuesday's maintenance day.  

My notes from today; 

1. Oscillations were noted and attributed to electronics design -> Daniel S. will address.  
2. Rai W. requested that we provide a means of support to take the weight of the Ionizer when mounted to the 1 1/2" valve on the BSC -> Kyle R. will address.  
3. Confirmation of the preferred means to pump to rough vacuum the X-end VE between cycles of discharge gas admission -> Chandra R. will address.
Non-image files attached to this report
TMDS_training_08222017_1.pdf
Comments related to this report
chandra.romel@LIGO.ORG - 09:53, Wednesday 23 August 2017 (38327)
Link

We will use the QDP80 to pump down the chamber between discharge cycles, with the turbo spun down and, as needed, use purge air to regulate the pump-side pressure to match the chamber pressure as to not break the 10" gate valve rated for 10 Torr differential pressure. Attached is a plot from LLO discharge. They spun up and down the turbo between cycles, but decided later it was not worth the trouble.

Images attached to this comment
jeffrey.kissel@LIGO.ORG - 20:30, Thursday 24 August 2017 (38358)CDS, DetChar, ISC, SUS, SYS, VE
Link 

Refer to Figure 1 of T1400713, TMDS design document for elements of setup.

A couple of useful videos of the oscilloscope readouts during the experiment:

Lesson 1: Control and readback of the electrometer from the TMDS inferface chassis, D1500152.
    Rai has set up the readback of the electrometer with the square-wave input shown on the blue trace, and the electrometer readback in yellow. One is looking for an even balance in voltage from the positive and negative ions. The electrometer has a negative voltage bias at the time of recording, so it appears as though we're getting more positive than negative ions, but, rest assured, we're good. 

Lesson 2: Demonstration of ionic discharge against TMDS chamber walls, if HV supply to ion generator is too high.
    The readback of the HV current is shown on the yellow trace. The video starts out with the ion generator discharging, as is evident by the rattiness of the waveform. At the last few seconds of the video, he reduces the VARIAC HV transformer gain, bringing the ion generator back to the desired level.

Lesson 3: Demonstration of electrometer readback once HV voltage is reduced
    Once the HV is tuned with the VARIAC, with the initial max amplitude of the square wave generator, then the square wave amplitude may be reduced to ~ 3 V pkpk (assuming a flow rate of about 30-50 [mL/s ?? not sure about those units]). Once we did this, we saw evidence for a ~3 MHz oscillation on the electrometer readback. Investigating the circuit drawing for the electrometer board (D1500061), Daniel and Mike agreed to replace the readback's output resistors R9 & R10 with ~100 [ohm] resistors. 
This has been done already, and the electrometer has been reinstalled

Lesson 4: Final setup of readback / monitor system, in the "ready to discharge into chamber" configuration.
    Once again, Rai demonstrates the control of the HV VARIAC and the desire to keep the ion generator current readback from any rattiness in its waveform, which is indicative of ionic breakdown discharge against the TMDS chamber walls.

I attach a ton more pictures of the setup as well. Hopefully the filenames are a good enough caption.
Images attached to this comment
kyle.ryan@LIGO.ORG - 10:09, Sunday 27 August 2017 (38386)
Link 

Desired gas flow rate 30 - 50 Liters per Minute (LPM)
H1 SEI
hugh.radkins@LIGO.ORG - posted 16:54, Tuesday 22 August 2017 - last comment - 16:58, Tuesday 22 August 2017(38313)
Why would the T240 trip the WD when trying to untrip the watchdog?

The simple excuse might be that apparently not all the Isolation Gains were zero.

Okay, HEPI and ISI tripped from a HEPI Pump Station VFD OU3 fault.  Upon trying to recover, operator was unable to untrip the WD.  The T240 was riled up and touching the 32k limit and pressing the WD Reset button just tripped the platform again immediately with T240.  Additionally, JeffK noticed that the H1:ISI-ETMX_ST1_WD_MON_CURRENTTRIG was not RED(on T240) even when the T240 was still banging on the rail [indicating the T240 was being ignored although I can't say I know that based on model.]

Checking the model as a refresher, if all the ISO gains are zero, the ST1 ISO STATUS is zero and the T240 is ignored (text read, not my understanding of the model logic at this time although I believe it to be true from experience.)

So looking at ISO gains & WD signals, first plot, 10 minutes: You see the three attempts where the WD_MON_STATE goes to 1 and immediately tripping back to damp only (state3) and the first trigger remains 2 (T240.)  So even though the ISO GAINs are zero and the ISO STATUS remains zero, attempts to clear the WD trips it back blaming the T240s.

The fourth attempt to clear the watchdog state succeeds but shows a situation I do not understand.  You see all the ISO gains going to 0.1 with the ISO status switching to 1 and then back to zero when the gains go back to zero, as expected.  Did the Guardian do this?  The first step of the ISO gain ramp up is to 0.01, not 0.1; you can see this on the gains toward the end of the traces.

My second plot shows the 6 horizontal T240 signals (the verts never hit 32k) and I checked overlying the curves that no attempt to clear the WD was made when none of the signals were at 32k.  The last attempt to clear the WD was after all the T240s are off the rail and while the weird brief gain switch to 0.1 occurred, the WD state remained 1 and recovery succeeded.

So why did the gains step up to 0.1?  That may be an aside study.  And, why did the WD fail to clear while the T240s were hitting the rail even though the T240 should have been out of the 'loop?'

I'll keep looking.  Is it related to the HEPI tripping?  That was kinda why the T240 MON was developed.  In this case, HEPI was reset and had completed its isolation steps.  Was the WD circuit not getting the ignore the T240 signal?  Work ongoing, guess I should do an FRS.

Images attached to this report
Comments related to this report
hugh.radkins@LIGO.ORG - 16:58, Tuesday 22 August 2017 (38314)
Link

FRS 8823

H1 General
jeffrey.bartlett@LIGO.ORG - posted 16:39, Tuesday 22 August 2017 (38312)
Ops Evening Shift Transition
Ops Shift Transition: 08/22/2017, Evening Shift 23:00 – 07:00 (16:00 - 00:00) - UTC (PT)
State of H1: Unlocked
Intent Bit: Commissioning/Corrective Maintenance
Weather: Wildfire smoke haze has returned to the area. Winds are a Light to Moderate breeze.  Temperatures are in the mid-90s.
Primary 0.03 – 0.1Hz: 0.02um/s
Secondary 0.1 – 0.3Hz: 0.06um/s
Quick Summary: Relocking after maintenance day. Commissioning work continues.
Outgoing Operator: Corey
LHO General
corey.gray@LIGO.ORG - posted 16:27, Tuesday 22 August 2017 (38306)
DAY Operator Summary

TITLE: 08/22 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Preventive Maintenance
INCOMING OPERATOR: Jeff
SHIFT SUMMARY:

Most of Maintenance was complete around noon.  Around 1pm started on an InitialAlignment, & unfortunately, the Y-arm was a bit off and this took me a long time to get back (but Sheila helped out).  Finally after getting ALSy back, the 

Had several tours today.

HEPI Pump Controllers died.  Hugh & I brought them back (he had to drive to both end stations).

TCSx flow rate trippped TCSx laser.  Rebooted interlock box & reset the servo relock the laser.  (Peter & Thomas)

Made a pseudo LVEA Sweep post-Maintenance Day (Turned OFF lights and confirmed WAP was OFF).
H1 to NLN at 23:22utc & Sheila is currently running a quick measurement.

LOG:

Maintenance Activities:

H1 CDS
david.barker@LIGO.ORG - posted 13:26, Tuesday 22 August 2017 (38310)
outside temperature drop during yesterday's partial solar eclipse (as seen from LHO)

here is a 12 hour, minute trend plot of the outside temperatures at LHO in degF. The time axis is centered around the time of the eclipse.

Images attached to this report
H1 SUS (SUS)
borja.sorazu@LIGO.ORG - posted 12:49, Tuesday 22 August 2017 - last comment - 07:00, Tuesday 10 October 2017(38309)
Violin mode frequency changes from in-air measurements to in-vacuum complete results for LHO and LLO

I have compiled the results of in-air measurements during installation and in-vacuum measurements from the alogs; 14231 LLO (including corrections mentioned in alogs 21652 and 27901) and 17610 at LHO (including corrections mentioned on the comments).

In the case when a frequency split is shown on in-vacuum measurements we have taken the average of both frequencies. I have grouped these numbers per front and back fibres, then per test mass and then per detector, finally I obtained the difference as (in-vacuum – in-air) including the sign:

We notice that in most cases the frequency difference is always positive, so frequency increases when moving the suspension to in-vacuum.

The increase in frequency is always a few hundred mHz (mean of 0.3Hz and median of 0.4Hz), with a clear outlier on LLO_ITMY_FL (which as explained here seems to be involved with uncertainty in the identification).

There is not clear difference in frequency variation between front and back fibres (especially no sign difference) which would indicate pitch effect.

However, notice that as per the Technical document T1700399 the expected increase in frequency due to buoyancy is of 0.14Hz, and the variation in frequency due to pitch angles of 2mHz is of 0.33Hz (although that would be an opposite sign change between front and back fibres). Therefore while the observed changes cannot be explained through pitch and buoyancy alone, they are of the same order.

Images attached to this report
Non-image files attached to this report
Violin_mode_frequency_difference_from_inair_to_vacuum_Table_Only.docx
Comments related to this report
borja.sorazu@LIGO.ORG - 05:41, Wednesday 23 August 2017 (38323)
Link

Further discussions on the results presented here has led to realize that the in-air measurements of the violin modes fundamental frequencies have a potential error of about 0.25Hz (as an example here are measurement results for LHO ITMX suspension). In base of this and to better understand the actual differences between in-air and in-vacuum measurements, now that we have very accurate measurements in-vacuum, it would be informative to measure in-air values once the suspensions are taken out. 

The in-air measurements have so far been done by acoustically driving the violin mode resonances. During this measurements the frequency of the driving acoustic signal is changed as a sweep sine. Because the in-air Q of the violin modes is considerably less than the in-vacuum values of 1 billion, if the sweep sine drive is not done with suitable slow pace then the observed a violin mode excitation at a frequency on the sweep sine which actually correspond to a previous frequency of the sweep but took some time to  ring up. Under this assumption, if the sweep sines were driven down (from high frequencies to lower frequencies) then there would be a consistent error on the measured in-air frequencies with values being lower than in-vacuum ones.

A way to improve the acoustic excitation could be by building a tower of speakers so that they could inject more energy into the violin modes of the fibres. Also be sure to drive the sweep sine at enough low pace or inject random noise excitation instead. Finally a lot of information could be gained by in-air measurements of higher order harmonics, this would help on characterization and understanding of higher order inharmonicity as well as higher order mode identification. 

 

borja.sorazu@LIGO.ORG - 10:46, Tuesday 29 August 2017 (38415)
Link

In order to proceed with the in-air measurements of the violin mode and its harmonics during the installation of the suspensions in the near future (as well as measuring the already install suspensions once removed), we have built in Glasgow a line array of 24 speakers of 60 cm length to match the length of the fused silica fibres. Its lightweight and compact design make it suitable to locate it parallel and in close proximity to the fibre that wants to be excited.

This line array produces considerable sound from 300Hz and well above several kHz making it suitable to excite the fundamental mode and up to the 6th harmonic and beyond.

A more complete description can be found on the technical document T1700414T1700414.

Images attached to this comment
borja.sorazu@LIGO.ORG - 11:20, Tuesday 29 August 2017 (38416)
Link

It is relevant to this alog to remember that while preliminary FEA modelling of the actual fibre profiles measured during installation of the LHO ITMX suspension (end of March 2014), has been used to predict in general terms the observed departure of the frequencies of the violin mode harmonics from whole multiples of the fundamental (“inharmonicity”):

 

However this preliminary results show that this prediction is not yet accurate to the few Hz level required for identification:

 

Images attached to this comment
borja.sorazu@LIGO.ORG - 07:00, Tuesday 10 October 2017 (38960)
Link

In order to complete the list of possible causes for the different inair and invacuum measured violin mode frequencies, I add next the contributions suggested recently by Norna, Dennis and Jon Feicht:

Violin modes frequency variations due to air damping

Air damping lowers the in-air measured violin mode frequency by a value inverse proportional to the violin mode’s Q-factor. Such that the maximum frequency for a damped oscillator (fm) is related to the undamped maximum frequency (f0) by:

fm = f0 ∙ sqrt[1-1/(2∙Q2)]

A quick look at recent in-air measurement on the LHO alog 38743 suggest a Q of at least 100 in-air at the ~ 500 Hz fundamental mode. This would give a in-air measured frequency value of the fundamental of 0.012Hz lower than in-vacuum.

Violin modes frequency variations due to mass/length of the fibre decreasing as the water desorbs from the silica fibre in vacuum

The mass loading on the fibre, due to water adsorption in-air, should in principle cause the in-air measurement of the violin mode fundamental frequency to be lower than in-vacuum, as once much of the water is pumped off the fibre in vacuum the frequency should increase. Dennis Coyne calculated that about ~3500 monolayers of water (each 2.5 angstroms thick) would be necessary to cause a 1 Hz shift at 500 Hz, due to mass loading alone. It is commonly asserted in vacuum literature that stainless-steel surfaces of a vacuum system exposed to air can start with "hundreds of monolayers of water".

However fused silica is hydrophilic and the interaction of silica surfaces and water is complex; Surfaces of silica under water can swell and form layers of silica gel1. The modification of the fused silica surface by the chemisorption and physisorption of water may even lead to a reduction in the elastic modulus of the fused silica in the outer layers.

References

[1] V.V. Yaminsky, et. al., "Interaction between Surfaces of Fused Silica in Water", Langmuir 1998, 14, 3223-3235.

H1 SEI (SEI)
corey.gray@LIGO.ORG - posted 11:30, Tuesday 22 August 2017 - last comment - 15:49, Tuesday 22 August 2017(38308)
Seismon Dead

Didn't catch when this happened, but see on the Seismon (compact) medm window that "SEISMON DEAD".  The "Keep Alive" is flashing on both Seismon screens.

Comments related to this report
jim.warner@LIGO.ORG - 15:49, Tuesday 22 August 2017 (38311)OpsInfo
Link

When there haven't been any earthquakes for a while (I think about 7 hours, but I sure of how to verify this), there are processes that clean up the event files that seismon generates and leave the directory empty. The way the epics code is written, this means the clock that we use for the diag_main test and "seismon dead" light on the compact seismon screen stops updating, which makes that diagnostic confusing.  I just noticed that last night, and I'm not sure what to do about it, but it's one of the few tests I can think of that are visible outside of the machine.  The only way to be sure at this point is check that the list mostly agrees with the USGS page (seismon spams some events, occasionally misses one) and watch to see if the diag_main message clears when a new eq shows up.

H1 PSL
jason.oberling@LIGO.ORG - posted 09:44, Tuesday 22 August 2017 (38307)
PSL Weekly FAMIS Tasks (FAMIS 3664 & 8436)

This morning I completed the weekly PSL FAMIS tasks.

HPO Pump Diode Current Adjustment (FAMIS 8436)

With the ISS OFF, I adjusted the operating current of the HPO diode boxes.  All currents were increased by 0.2 A, changes summarized in the table below:

  Operating Current (A)
Old New
DB1 49.6 49.8
DB2 52.5 52.7
DB3 52.5 52.7
DB4 52.5 52.7

I did not adjust the operating temperatures of the DBs.  The ISS is now back ON and the HPO is outputting 155.0 W; I have attached a screenshot of the PSL Beckhoff main screen for future reference.  This completes FAMIS 8436.

PSL Power Watchdog Reset (FAMIS 3664)

I reset both power watchdogs at 16:34 UTC (9:34 PDT).  This completes FAMIS 3664.

Images attached to this report
LHO General
corey.gray@LIGO.ORG - posted 08:12, Tuesday 22 August 2017 (38305)
Transition To DAY

TITLE: 08/22 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Preventive Maintenance
OUTGOING OPERATOR: Jim
CURRENT ENVIRONMENT:
    Wind: 4mph Gusts, 2mph 5min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.10 μm/s
QUICK SUMMARY:

Maintenance Day!

Jumping headlong into Maintenance day.  Have a pretty full board.  Full steam ahead!

H1 General
jim.warner@LIGO.ORG - posted 07:57, Tuesday 22 August 2017 (38303)
Shift Summary

TITLE: 08/22 Owl Shift: 07:00-15:00 UTC (00:00-08:00 PST), all times posted in UTC
STATE of H1: Observing at 52Mpc
INCOMING OPERATOR: Corey
SHIFT SUMMARY: Quiet shift, 1 lockloss, PCAL lines turned off briefly
LOG:

12:30 Lockloss, no apparent cause, back to observing 13:00

14:20 Turned off PCALX lines for a measurement, back on 14:35

H1 AOS
jim.warner@LIGO.ORG - posted 07:41, Tuesday 22 August 2017 (38302)
PCALX lines turned off for remote measurement

Adam Mullavey called and said he needed to run a measurement for today's maintenance. His measurement needed the PCAL X lines turned off, so he had me turn the amplitudes on those lines down to 0. Unfortunately, he ran into some permissions issues and couldn't do his measurement. LHO was out of OBSERVE from 14:21 to 14:34 for this, but as far as I know the only differences during that time were from turning off the pcal lines. Attached screen shot shows the settings we were running while observing. All the oscsin and osccos amplitudes were zero'd for the planned measurement. I've reverted them to the pictured settings now.

Images attached to this report
H1 SEI
jim.warner@LIGO.ORG - posted 01:56, Tuesday 22 August 2017 (38301)
BRSY getting close to out of range, should make it through the end of the run

The end Y BRS is continuing it's slow drift and is getting close to going out of range, but should survive through the end of the run. It's possible, however, if it gets rung up by people working in the area, it could cause a problem for the damping loops and leave the BRS in an unusable state. 

Images attached to this report
LHO General
thomas.shaffer@LIGO.ORG - posted 00:02, Tuesday 22 August 2017 (38300)
Ops Eve Shift Summary

TITLE: 08/22 Eve Shift: 23:00-07:00 UTC (16:00-00:00 PST), all times posted in UTC
STATE of H1: Observing at 50Mpc
INCOMING OPERATOR: Jim
SHIFT SUMMARY: 39.5hr lock, many tours for the eclipse party. Quiet shift overall.

H1 CAL (CAL, DetChar)
alexander.urban@LIGO.ORG - posted 23:32, Monday 21 August 2017 (38299)
Updated C01 comparison through Aug. 1

A. Urban, on behalf of the calibration group

The C00 vs. C01 comparison pages have been updated and include all C01 data from 2016-11-30 through 2017-08-01.

As part of this analysis, I've got updated PCAL-to-DARM ratio trends at 36.7, 331.9 and 1083.7 Hz (attached below).

Plots of both magntidue and phase residual timeseries trends are attached. These trends are computed by demodulating 300-second segments at each PCAL line frequency, then averaging to get a magnitude and phase out of each channel. In practice, I break up each 300-second segment into overlapping 100-second chunks, apply a Kaiser window, and then average over chunks to get a less noisy measurement. (It's basically Welch's method, except I'm demodulating rather than computing a PSD.) Finally, I remove most outliers that are due to locklosses and loud transient glitches. The same analysis was done on Livingston data; see L1 aLOG 35501.

In each plot below I show PCAL/strain trends for C00 (blue) and C01 (red) data. The trend shown in aquamarine applies a correction for f_cc to C01 data at the appropriate PCAL line frequency. Gray shaded regions correspond to times when we had a break in O2, once during the holiday season and once for commissioning work.

At mid and high frequencies, everything continues to be in order at the PCAL lines. You can see that in the bucket (331.9 Hz) all systematics are accounted for by f_cc and only very small (~1%) statistical fluctuations remain in C01. At high frequency (1083.7 Hz) there's a slight systematic offset at the level of 1% or so in magnitude and 1-2 degree in phase, which is consistent with Craig's error budget. However, in the C01 low frequency line there is a mounting phase offset prior to the May vent that becomes worse after the break: the offset is 2-3% in magnitude and about 2 degrees in phase from June all the way through August. I suspect this has to do with spring detuning in the signal recycling cavity, and will follow up on it soon.

Images attached to this report
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