The temperature swing shown in this aLOG is relatively small (~ +/-0.4 deg F), entirely explained by the maintenance day activities on the HVAC system, and recovered to 67 +/- 0.2 deg F by 17:00 PDT. See LHO:70428.

Here are the plots of ASC-AS_C_NSUM, OMC-QPD_A_NSUM, OMC-QPD_B_NSUM and OMC-REFL_A_LF, during these measurements. ASC-AS_C_NSUM shows between 22.8 and 32.1mW, OMC-QPD_A_NSUM 23.4mW, OMC-QPD_B_NSUM 23.0mW, and OMC-REFL_A_LF 24.8mW. According to Keita OMC-REFL_A_DC has an incorrect calibration and shows 25.2mW. The average of the 2 QPDs would be 23.2mW, which is about 6.5% lower than 24.8mW.

Second screen shots shows a time when the IMC was unlocked. The DC offsets are in the 10s of uW at most.

Using data from the scan I adapted labutils/OMCscan class to plot the fitted scan and adapted labutils/fit_two_peaks.py to fit a sum of two lorentzians functions for distinguishing carrier 20/02 modes.

The first graph is the OMC scan plot, the second is the curvefit for the second order carrier modes.

We expect the HOM spacing to be 0.588 MHz as per this entry and DCC T1500060 Table 25.

The spacing for the modes measured is 0.592 MHz.

From the heights of the two peaks this suggests mode-mismatch of the OMC to be C02+C20/C00 = (0.83+1.158)/(15.32+0.83+1.158) = 11.0% mode mis-match.

From the locked/unlocked powers on the OMC REFL PD the visibility on resonance is 1-(3.51+0.03/24.73+0.03) = 85.7% visibility.

If the total loss is 14.3%, this implies that the other non mode-matching losses are roughly 1.3%.

To run the OMC scan code go to 

/ligo/gitcommon/labutils/omc_scan/ and run 

python OMCscan_nosidebands.py 1370712036 100 "Sidebands off, 10W input" "single bounce" --verbose --make_plot -o 2
in the labutils conda environment and on git branch dev.

To do the double peak fitting run:

python fit_two_peaks_no_sidebands.py  
in the labutils conda environment and on git branch dev.

These scans were done with OM2 cold.

For comparison with new OMC measurements I used Sheila's code to process the visibility, but updated dit to use nds2utils instead of gwpy as I was having trouble using it to get data.

The code is attached and should be run in the nds2utils conda environment on the CDS workstations.

Power on refl diode when cavity is off resonance: 24.757 mW

Incident power on OMC breadboard (before QPD pickoff): 25.239 mW

Power on refl diode on resonance: 3.525 mW

Measured effiency (DCPD current/responsivity if QE=1)/ incident power on OMC breadboard: 70.4 %

assumed QE: 100 %

power in transmission (for this QE) 17.760 mW

HOM content infered: 13.472 %

Cavity transmission infered: 82.111 %

predicted efficiency () (R_inputBS * mode_matching * cavity_transmission * QE): 70.367 %

omc efficency for 00 mode (including pick off BS, cavity transmission, and QE): 81.323 %

round trip loss: 1605 (ppm)

Finesse: 371.769

For archive: here are the original EY HEPI Pump Controller Settings.

and here are the CS settings for completeness

AHU 2 Cooling Coil 3's strainer cleaning has had minimal impact on LVEA temperature value, nor fluctuations. Excellent!
(Note, we've been calling these Fans, but I found out in talking with Bubba and Tyler today that this is a liquid strainer that filters the line that feeds the cooling coils. The *numbering* is still legit, they cleaned AHU2 Cooling Coil 4 strainer on May 30 2023 and today they cleaned AHU2 Coiling Coil 3 strainer)

Separately, the change to have AHU 1 Damper at 60% is OK (Bubba had adjusted from 70% he mentions in his above aLOG to 60% shortly after posting; comments on its effect in the timeline below). 

After unplugging the drain of the air handler, and holding the damper open at 60% in "manual" mode (as opposed to servo controlled "auto" mode), the AHU 1 cooling coils 1 and 2 have now restored to much better/cooler, normal temperatures (~47 deg F) that we had lost by May 30th 2023 (the fateful fire-alarm chaos day; see timeline in LHO:70284). Excellent!

LVEA temperature excursions in Zones 1A (this BSC2 / Beam Splitter), Zone 4 (Output Arm), and Zone 5 (Input Arm) never exceeded 0.4 deg F outside of 67 deg F range, and restored to normal ~67 deg F temperatures with small diurnal fluctuations within 7 hours. Excellent!

Slowly but surely, I think these maintenance activities are good, and not only restoring expected system behavior, but making it better. We now have a much tighter collection of temperatures in the LVEA, cooling coils are operating at a nice low temperature, and more zone heaters are coming alive such that we have the expected "constant heat, constant cool in order to keep the LVEA temperature nice and controlled" behavior.

I now have much more confidence that we can continue to do this kind of maintenance and not have it impact the IFO.

Timeline of today's work all within today's Tuesday Maintenance:
See Today's trend compared against a 7 day and 21 day trend.

Jun 13 2023 08:26 PDT 
    Bubba and Tyler start work, bringing down Air Handler 2, valving out AHU2's cooling coil 3's strainer and clean it.
    Understandably, all zones temperatures start to rise from 67 +/- 0.1 deg F but only max out 67.4 +/- 0.1 deg F.

    Also while out there, this is when they find that air handler 1 AHU 1 is flooded "again."

Jun 13 2023 09:03 PDT 
    Within a half hour, they're done with AHU2 strainer cleaning, AHU1 drain de-clogging, turn AHU2 back on, and temperatures begin to drop accordingly.
    
    Upon restoration, though, and back at the control room work station -- they still see AHU 1's cooling coil temperatures high (~ 61 deg F), as its been since May 30 2023.
    Indeed, also, the damper for AHU 1 is closed at 0%, as it has been doing diurnally since May 30 2023 -- the HVAC servo opens up AHU 1's damper each day (around when outside temperatures exceed 70 deg F), and then gradually ramps closed again by nightfall's temperature drop.
    Prior to May 30 2023, AHU 1 damper stayed around ~35% open throughout the day and night.

Jun 13 2023 09:03 PDT
    Bubba intuits that there's too much condensation gathering in AHU 1 because its damper is closed too often, and that condensation doesn't get drained out because its drain is clogged. As a mitigation attempt, instead of having the HVAC servo drive the damper open percentage, he switches over to Manual mode and holds it at 70% as described in his aLOG.

    This drops both cooling coil's 1 and 2's temperature down from 61 to ~47 deg F. Awesome.
    But, this starts to scare the wimpy scientists (me) who are paying too close attention too quickly, because they see the temperatures in the LVEA drop below the 67 deg F set point.

Jun 13 2023 10:02 PDT
    Zone 4 (input arm) zone heater turns on, and begins to bring the Zone 4 temperature back in line.

Jun 13 2023 11:00 PDT
    Bubba makes a further adjustment of the AHU 1 damper percent open from 70% to 60% open to try to decrease the cooling in the LVEA.

Jun 13 2023 12:07 PDT
    Zone 1A's zone heater collection turns on (human controlled? servo controlled?) for the first time, much like Zones 4 and 5 heaters came on for the first time after AHU2's cooling coil 4's strainer was cleaned, ramping up to ~70% in 5 minutes by 12:15 PDT.

    This really starts to turn around the LVEA temperatures for the better; the temperatures bottom out turn back up, overshoot a bit, and settle to yesterday's mid-day value. 

Jun 13 2023 17:00 PDT
   Temperatures are all restored within to ~67 +/- 0.2 deg F, and again, they never exceeded +/- 0.4 deg F.
   The "natural experiment" reveals the impulse response of the Zone 1A is about 5 hours, as long at the zone heater for that zone comes on!

The fault codes listed correspond to:

0x16 - reboot alert
0x07 - CBT signal degradation.

So this looks like a reminder that we have had the clock running for a long time and it is getting older.

Lockloss ndscopes seem to show a csoft ringup?

You can see MICH and SRM increase in the minute preceding lockloss which agrees with the increase in wind to 20mph, see attached.