Today Dripta and I went to EY and did what would have previously call a standard ES measurement with PS4.

And We also employed the new End Station procedure.

Details and analysis ccoming in a comment to this alog.

TITLE: 05/28 Eve Shift: 2300-0800 UTC (1600-0100 PST), all times posted in UTC
STATE of H1: Lock Acquisition
OUTGOING OPERATOR: Ibrahim
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 24mph Gusts, 16mph 5min avg
    Primary useism: 0.06 μm/s
    Secondary useism: 0.12 μm/s
QUICK SUMMARY:

The site is currently being hammered by high winds gusts have recently started approaching 40mph (H1 just had a lockloss during these high winds...and green arms have been having troubles, so I am taking H1 to IDLE and Observatory Mode to WINDY on an hr by hr basis....hoping winds cooperate after sundown.

When H1 is able to return to NLN, Camilla requested for SQZ that scan_alignment_fds & scan_sqzang be run.

Terry, Kar Meng

The second SHG seems to have the appropriate finesse (~60) at 1064 nm. Next steps remove high reflector from temporary mount and place it in the SHG housing, then recover modes then look for green light.

TITLE: 05/28 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Lock Acquisition
INCOMING OPERATOR: Corey
SHIFT SUMMARY:

IFO is in LOCKING at LOCKING_ARMS_GREEN.

We acquired NLN earlier but lost lock while some last min SQZ maintenance was being done. We lost lock from LOWNOISE_COIL_DRIVERS at 23:23 UTC and the wind is really picking up now (40mph gusts).

LOG:

I made two minor changes that I tested out during relocking today.

LOCKING_ARMS_GREEN state will not run increase flashes if the SEI state is not nominal in the respective arm. This is to stop increase flashes aligning to while an ISI is tripped and aligning to a bad spot. It will notify "Arm SEI not nominal, no I.F. until resolved", but I couldn't get it to stay up for long before other notifications would get in the way. Regardless, it wont run I.F. and will work for unattended times.

In ALS_DIFF  the find IR used to step the offset and then do an instantaneous check to see if there was any resonance with a low threshold. We've gotten unlucky a few times where it dipped just below the threshold during the check. To remove luck from this, I have it now grab data every step and look at the max. The downside to this is that if there is an nds issue, it will fail. I also increased the fine tune IR step size from 3 ->5 and it seemed to work well.

Sheila, Camilla, Jenne, Naoki

While Ibrahim was doing initial alignment during maintence today, I moved SR3 (using sliders) and SR2 using the osem, to the positions in the second column of 77719 (-P move of SR3, May 7 10:39 pacific). 

Alena has been working with the zeemax model of what happened when our OFI was damaged, and she believes that this location is more centered in the OFI, and this data may be useful to her modeling.  We haven't recovered the range or all of the optical gain that we thought was possible before the OFI was damaged (our OMC alignment wasn't optimized when this happened), so we are hoping that a different spot may help.

When we relocked after this the range was low (~145 Mpc), the attached screenshot shows that we have more LSC coherence now.  We should be able to adjust LSC feedforward during tomorow's commissioning time to address that. 

I have been testing a high voltage version of the cps in the staging building for several months now. These new sensors are supposed to have something like 4x lower noise than the cps we currently use, cps noise limits table motion between about .5-10 hz. This morning I tried to test them on the HAM7 ISI this morning. The test just required disconnecting the existing satellite chassis at the chamber and connecting a new set of in air electronics outside the chamber.

I did a couple quick transfer functions to check the sensor responses made sense, then turned on the isolation loops. Loops were stable, no problems there, but I didn't get good performance data. There were a number of people working near the chamber, so it wasn't very quiet. It also didn't seem like the HV cps noise floors were as low as I've been able to get on my test stand in the staging building.

Attached plot compares individual some cps noise floors, red and green are regular sensors from some time in the middle of the night, purple and black are the lowest noise high voltage sensors from my test this morning. Unfortunately, the other 4 HV cps were the same noise or higher than the regular sensors. I didn't have a lot of time to try to poke at the new sensors. I'll try again next week, it would help if I can have it quiet around the chamber it would help, but that doesn't affect the 100hz noise.

J. Kissel
EDIT :: False Alarm -- see comment below!

Since I'm at the "what does it all mean?" stage of madness with the OMC DCPD Transimpedance Amplifier (TIA), I decided to make it worse -- I remeasured the original transfer function that triggered me worrying about the TIA response in after the OMC swap (see LHO:75986). I did this to try to corroborate whether there is a change in the DCPDA response above 1 kHz as mentioned in LHO:78090. 

This transfer function is the remote, DAC-driven measurement of the whole DCPD sensing chain -- the transimpedance amplifier, the whitening chassis, and the front-end compensation for the frequency response of those -- this has been described most recently in LHO:71225. 

I *don't* see a difference above 1 kHz, but I *do* see more difference in response below 25 Hz than I had in 2024-Feb-26.

See the attached transfer functions of the DCPDA chain and the DCPDB chain.

Black is pre-OMC swap, 2023-Jul-11.
Brown is post-OMC swap, 2024-Feb-26.
Red is today, also-post OMC swap, 2024-May-28.
All measurements use the S2300003 whitening chassis, and the compensation from the 2023-Mar era compensation we've been using throughout O4.

The only "oh, well it could just be" that I can think of immediately is that the DCPDs had been powered down from 10:10a to 11:30a PDT today to characterize the measurement setup in analog (see LHO:78090), and these were measured "only" 20 minutes after being powered back on at 11:50a. So -- we'll have to take the measurement again at the next opportunity -- such that the TIA electronics have what we think it the appropriate amount of time to thermalize -- a few hours.

           Just maddening.

Data lives in 
    /ligo/svncommon/CalSVN/aligocalibration/trunk/Common/Electronics/H1/SensingFunction/OMCA/Data/
        20240528_H1_TIAxWC_OMCA_S2100832_S2300003_DCPDA_RemoteTestChainEXC.xml
        20240528_H1_TIAxWC_OMCA_S2100832_S2300003_DCPDB_RemoteTestChainEXC.xml

J. Oberling, R. Short

Our PMC Refl signal has been slowly increasing over the last several months; by extension this means that PMC Trans and the amount of power available to the IFO has been decreasing.  Ryan and I went into the PSL enclosure to take a look at things.

We began by using an IR viewer to look at the PSL optics.  All looked as expected except for M11, which was a bit brighter than we both recall; this is the 1st of the two turning mirrors that steer the beam into the PMC.  We noted to take a close look at this optic once we had things turned off.  We next took several power measurements around the PMC, all done with the ISS OFF; with the ISS OFF the power moves around a little bit more, so I've included the min and the max readings at each location:

• PMC In: 126.5W - 127.7W
• PMC Refl:
  • Locked: 20.3W - 20.8W
  • Unlocked: 125.9W - 126.2W
• PMC Trans: 106.1W - 106.6W
• Amp2 Out: 136.8W - 138.3W
• ISS Diffracted Beam: 3.8W (@ ISS offset of 4.3)

Things here match our PD calibrations OK.  One thing we noticed, the amount of ISS diffracted power was a little low for the amount of variation we were seeing in the output of Amp2; we therefore adjusted the ISS offset a little to bring that bank back up a bit, to ensure we have enough power available to counter the swings in Amp2 output.  We finished here with an offset of 4.7, and 4.2W in the ISS diffracted beam (again, this was with the ISS OFF).  The ISS now defaults to ~3.0% diffracted power when it is OFF (this change was accepted in both SAFE and Observe SDF).

This done we moved on to inspecting optics with our green flashlight.  With the PMC unlocked and the PSL external shutter closed, we looked at all of the optics between the external shutter and the PMC.  Sure enough, all optics looked good except for M11 (see first picture).  8 in situ, very careful drag wipes later the optic looked much better, and better yet no signs of damage (see 2nd picture).  Still some small dots on it that I couldn't remove, my guess is these are small coating defects that the green flashlight is really highlighting.  We then opened the shutter and viewed the mirror through the IR viewer, and while it was still a little bright it did look much better.  The PMC relocked without issue, but PMC Refl was higher than when we started (likely due to the PSL environmental controls being on and slight alignment shift during drag wiping M11).

Last, we checked centering on the PMC locking PD and the PD that reads PMC Refl.  These PDs were well centered, with no improvement made when we tried to adjust the alignment onto the PD.  This tells me that we have not seen an alignment shift between Amp2 and the PMC, which tracks with the fact we have acheived almost zero improvement to PMC Trans/Refl by tweaking beam alignment.  Since we already had a mutlimeter set up, we took a visibility measurement for the PMC:

• Unlocked: -0.463 V
• Locked: -0.038 V
• Visibility: 91.8% (!!!)

The visibility measurement looks good, really good, and does not match what we see with PMC throughput.  Using our power measurements from earlier, we're only transmitting ~83.7% of the incident light through the PMC, nowhere close to what our visibility measurement suggests.  This reminds me of the old loss issues that plagued the original glued aLIGO PMCs at LLO, and spurred the development of the all-bolted PMCs we're using now at both sites.  Could our issue be loss build-up in the PMC?  This suggests that is a likely possibility.

At this point we left the enclosure to consider next steps.  We do have a spare all-bolted PMC that we could swap in and see how it performs.  This is, theoretically, a quick process, as the all-bolted PMCs have magnetic ball mounts that help preserve PMC alignment upon removal (we tested this a little when we installed this PMC in April 2018, and it seemed to work well).  For now, the PMC Refl signal is still higher than when we went into the enclosure, by almost 3W.  This isn't entirely surprising, as I did clean mirror M11 and the PSL environmental controls were on for a couple hours.  We're watching things for time being, hoping that PMC Refl comes back to "normal" once the enclosure thermalizes; if it doesn't then either Ryan S. or myself will do a quick alignment tweak at an available opportunity (or next Tuesday if no opportunistic time pops up between now and then).  Probably more to come here.

This closes LHO WP 11881.

J. Kissel, [emotional support from L. Dartez remotely]

Executive Summary 
Contrary to the grand plan, I instead unplugged and re-plugged in some cables, and lost 4 hours of my life. The OMC DCPD electronics chain remains as it did before today. I'm confused yet again.

Full Summary
After we last left the saga of "the in-vacuum OMC DCPD Transimpedance Amplifier (TIA) frequency response has changed a little since the OMC Swap; let's re-measure it in analog" (LHO:77735), the 2024-May-13 plan was to swap the apparently broken S2300003, D2200215-style OMC DCPD Whitening Chassis, for a spare (I chose S2300002), in hopes that we'd be able to make a new analog measurement of the TIA without the non-linearity in the whitening chassis' measurement setup. 

Today, the installed-in-the-racks measurement setup using S2300002 got even more weird :: very different from the exact same setup of the same chassis in the EE shop. "Weird" is 
   :: 2 [V/V] rather than 1 [V/V], and 
   :: a very obvious, 10 [%] / 3 [deg] wiggle, frequency response above 1 kHz, rather than "subtle, slightly different nonlinear roll off." 
Indeed, to confirm my insanity, I quickly switched over to CH B of S2300003 while there with everything else the same, and it's similarly weird -- and different from the previous in-rack measurements taken only a few weeks ago where I'd probed its subtle non-linearity around 1 [V/V]. 

             Just maddening.

That being said, after dividing the maddening response of the measurement setup out of the data we really want -- the analog measurement of the in-vacuum TIA -- we see a good clean measurement, with finally with the same DC gain as the good old 2023-03-10 measurements. BUT -- DCPD A's response shows change from the best 2023-03-10 measurement data set -- but at *high* frequency rather than "below 25 Hz." I don't think this is real. More on this in a follow-up aLOG.

In the end, after four hours in front of the SR785, Louis and I decided to revert the signal chain back to using S2300003 as had and has been the case for all of O4.

I'll hang my head, eat my hat, put foot in mouth, and head back to the EE shop.

Attached is a collection of plots the shows today's results.
   :: Pages 1 & 2, for DCPDA and DCPDB, respectively, the TIA response, with the maddening measurement setup divided out. One can see that the for DCPDB (page 2) that today's 2024-05-28 measurement divided by the currently installed compensation (from 2023-03-10) agrees very well with the 2023-03-10 measurement over compensation. However, for DCPDA (page 1), we see a diverence from the model and old measurement above 1 kHz.

   :: Pages 3 & 4, for DCPDA and DCPDB, again show the obscene difference between today's measurement setup's response -- the 2 [V/V], with 10 % / 3 deg wiggle above 1 kHz -- and the previous "bad" result from 2024-04-23, and the originally "I'm happy with that" 2023-03-10 result, both of which are 1 [V/V] with "a little bit of phase loss, but that's it."

   :: Page 5 shows the ratio of all of today's measurement setup responses, showing that even from channel to channel and chassis to chassis, I get this exact same response. I even swapped out the SR785 accessory box for another to see if this was the issue, and I got the same response.

The only piece of electronics left as suspect is the SR785. But --
    (1) Out of the utmost caution, I run a factory reset on any SR785 I touch before I begin configuring it for measurement, and 
    (2) This is a *differential* transfer function measurement with the SR785. That means the ratio CH2 (A-B) / CH1 (A-B) is changing. I find it quite hard to believe that this could be happening.

And in case you're suspicious that "Oh, you must have blown the input electronics by driving too hard into it," We're careful to keep the input voltage for each A and B spigot of CH1 and CH2 below the specified 5 [V_pk], and we're watching for its ADC saturations at all times.

So, ya, maddening.

More details in the comments for posterity.

Andrei, Sheila

We've analyzed the time-traces of the effective range (H1:CDS-SENSMON_CAL_SNSW_EFFECTIVE_RANGE_MPC) along with the alignment channels FC_WFC_A(B) and AS_A(B)_RF42 (see attached figures). We found no observable dependance between those.

The LVEA has been swept, the FARO is being left plugged in as usual, there were some ladders left out along the yarm.

TITLE: 05/28 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Preventive Maintenance
OUTGOING OPERATOR: Ryan S
CURRENT ENVIRONMENT:
    SEI_ENV state: MAINTENANCE
    Wind: 6mph Gusts, 4mph 5min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.09 μm/s
QUICK SUMMARY:

IFO is in IDLE for TUESDAY MAINTENANCE

IFO was stuck at acquire PRMI when I arrived (recovering from an EQ seemingly) so I took it to idle (and set SEI_ENV to MAINTENANCE) for today's maintenance activities.

Tuesday Maintenance activities have ended and IFO is now RELOCKING

Nothing else of note

Sheila, Camilla.

Ran a Bruco from this weekend's 30 hour lock: 05/27/2024 14:37UTC, 15h30 after NLN, range 155MPc. Link here. 

PRCL looks better but still bad 10-25Hz, SRCL has <0.05 coherenece 100-350Hz, CHARD_Y is bad below 20Hz. 

Compared to Bruco in 77976 which was before the 78012 PRC move.

Pictures of the OMC IO Chassis.

LLO noted a 10 Hz comb that was attributed to the IRIG B monitor channel at the end station connected to the PEM chassis. (https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=71217)

LHO has agreed to remove this signal for a week to see how it impacts our DARM signal.

EX and EY cables have been disconnected.