Sam and I have been investigating a ~40 Hz peak in the HAM ISIs and PEM accelerometers, first noticed by Camilla and Sheila in alogs 79001 and 78879. Jim also investigated and suggested the peak may be caused by gain peaking from the isolation loops (alog 79145). The peak is strongest in HAMs 2, 6, and the LVEAFLOOR YCRYO Z accelerometer. We tracked the first appearance of the peak to May 20th. We've found there are actually two peaks roughly 0.2 Hz apart, which drift a bit in frequency from ~39.45 Hz (20/05/24 16:00 UTC) to ~40.2 Hz (20/05/24 22:00 UTC), measured from the point between the two peaks (see 1st attachment). The peaks consistently remain about 0.2 Hz apart in frequency but they do not always have the same magnitude ratio, even between channels measured at the same time (see 2nd attachment). Overall, the peaks vary in magnitude, occasionally disappearing altogether, but we have yet to find a time when one peak disappears and the other doesn't (see 3rd & 4th attachments for peaks disappearing and reappearing, respectively). We'll continue looking into surrounding peaks and the coherence with DARM.
The extra drive on HAM2 is likely from a very thin phase margin on the HAM2 X feedback loop. I measured this yester day and found that it had something like 5 deg of phase margin with a 32-ish hz ugf. I backed this off quite a bit, phase margin is now around 20deg and the ugf is more like 27 hz. Might be worth doing some quick checks on these for all the ISIs. Measurements of the X ugf and phase margin are attached. Red is the modified loop I installed yesterday, blue is the loop with the filters that have been running up to that point, not sure when the last measruements were run, it's been a while.
16:09 Tue 23 July 2024 PDT the atomic clock jumped to +0.42S out from the Timing system.
This is the third time this has happened in the past month. Prior to that it had only happened once in the past year, on 4th May. Here is a table of the atomic clock out-of-syncs for the past year
out-of-sync | resynced | uptime since last resync |
23rd July 2024 | still out | 4 days |
17th July 2024 | 19th July 2024 | 43 hours |
15th July 2024 | 15th July 2024 | 2 months 11 days |
4th May 2024 | 6th May 2024 | +1 year |
I have extended the timing comparator's tolerance to 0.9999999 seconds to 'green up' the corner station timing.
Wed Jul 24 08:05:48 2024 INFO: Fill completed in 5min 44secs
Jordan confirmed a good fill curbside.
TITLE: 07/24 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Corrective Maintenance
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
SEI_ENV state: MAINTENANCE
Wind: 4mph Gusts, 2mph 5min avg
Primary useism: 0.01 μm/s
Secondary useism: 0.05 μm/s
QUICK SUMMARY:
Close to getting the AUX laser aligned (79291)!
Sheila, Jason, Jennie, Keita, Jenne, Camilla, Naoki. Following 79274.'
Summary: We still need more work on the alignment laser tomorow. Today we believe that we understood the right process for setting it up, but we will need to iterate a few more times to get it set.
It's useful to know the geometry of this setup.
The SRM is a convex mirroor with R=5.678m ROC (and therefore a converging flat-convex lens with f=12.6m focal length).
All rays retro-reflected by the SRM HR surface converge at a single point. Because of the lensing effect of SRM, this point is NOT the center of the ROC but away from SRM by Rf/(R+f)=3.92m. OM1 is 3.65m away from SRM. These are all you need to know (plus a basic knowledge of thin lens), but I drew a cartoon for you (1st attached, top, but you can also see 2nd attachment for the math) where four different rays, all retro-reflected by SRM, are converging at one point.
Now, Sheila's 3rd bullet point from the bottom is like the green line in the cartoon. The green dot at the OM1 position marks the center of the OM1, however there's only one ray that is retroreflected and goes through the center of OM1 (green line), which happens to be VERY low on SRM.
Without touching SRM, we can walk the beam on SRM while keeping the retroreflection and bring up the position at SRM by deltax, and as a result the beam position goes up about 0.07*deltax at OM1 and about 3.7*deltax on SR2.
Note that a small pit offset on OM1 has a big effect on SRM and SR2, i.e. 1mm on OM1 will become 14mm at SRM and 54mm at SR2.
SR2 beam position when Sheila left was 1cm to +X, too low by 3"~76mm (i.e. the beam needed to move to -X by 1cm, up by 3"~76mm).
Now the task is to rotate the SRM, maintain the retroreflection while keeping the beam position on OM1. This is explained in the attached cartoon again. Anyway, conclusion is that if we want to move the beam up by deltay at SR2, we have to rotate SRM by deltay/215m, i.e. deltay/[SRM rotation] ~ 2mm/10urad.
(The calculation in the attached assumes that we're fixing the OM1 beam position, but in reality the iris is maybe 50cm or so closer to SRM, so L=3.15 instead of 3.65. This should have a large effect on one of the important numbers d-L=3.92m-L, it changes from 0.27 to 0.77. Mostly because of this, my calculation is severely overestimating the deltay/[SRM rotaion] maybe by a factor of 3, roughly.)
Anyway,we used 2mm/10urad number at the time, and moved SRM in PIT by negative 380urad (PIT slider 2121 -> 1741, YAW slider -3492 no change).
At this point we reset the position of the iris to the beam. Naoki, Jason and Jenne adjusted the steering mirror and the BS so the beam hits the center of the iris while keeping the retroreflection. We stopped the work there.
This is a picture of Sheila entering HAM4-HAM5 tube through the eye-shaped baffle.
Should also add that when restoring the aux laser alignment to OM1 position and the retroreflection iris in the afternoon, the alignment converged much quicker when using the beamsplitter to align the retroreflection and the steering mirror to align OM1 position. In the morning we were doing the opposite (beamsplitter to OM1, steering mirror to retroreflection), and while we were able to get the alignment to converge it was picky and had a tendency to diverge if we made large steps.
After working through the math Keita had said this might be the case. Our first run at restoring the aux laser alignment in the afternoon, still using beamsplitter to OM1 and steering mirror to retroreflection, was diverging when we were moving in the direction we clearly had to move, so we switched to beamsplitter to retroreflection and steering mirror to OM1; alignment went much smoother afterwards.
Tagging for EPO.
TITLE: 07/23 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Corrective Maintenance
INCOMING OPERATOR: None
SHIFT SUMMARY: Work today was just a continuation of work on aligning the AUX laser
LOG:
Start Time | System | Name | Location | Lazer_Haz | Task | Time End |
---|---|---|---|---|---|---|
17:09 | SAFE | LASER HAZARD | LVEA | YES | LVEA IS LASER HAZARD | 03:49 |
14:49 | FAC | Kim, Nellie | Optics Lab | y(local) | Tech clean | 15:15 |
15:16 | FAC | Nellie, Kim | LVEA | YES | Tech clean | 16:35 |
15:47 | OFI | Sheila, Jason, Camilla | LVEA | YES | Continuing OFI work (Camilla out 17:58) | 19:21 |
16:01 | FAC | Tyler, Ivan | LVEA | YES | Walking around | 16:43 |
16:05 | PCAL | Francisco | PCAL Lab | y(local) | PCALin | 16:20 |
16:09 | VAC | Jordan | LVEA | YES | Addressing HAM6 purge air and running an RGA | 17:27 |
16:19 | BIO | Sabby | Behind water tank | n | Taking soil for experiment | 16:54 |
16:26 | VAC | Gerardo | LVEA | YES | Joining Jordan at HAM6 | 20:07 |
16:32 | FAC | Chris | MY, EY, MX, EX | n | Picking up old light fixtures | 18:47 |
16:36 | SUS | RyanC, Rahul | HAM Shack | n | Looking for parts | 16:56 |
16:37 | CDS | Richard | LVEA | YES | Checking on computers | 17:00 |
17:03 | SUS | RyanC | CR | N | ETM OPLEV charge measurement | 18:46 |
17:04 | OFI | Keita | LVEA | YES | Joining OFI team | 19:21 |
17:09 | OFI | Jenne | LVEA | YES | Joining OFI team | 19:21 |
17:35 | OFI | Naoki | LVEA | YES | Joining OFI work | 19:00 |
17:51 | FAC | Richard | LVEA | YES | Because he can (checking in on OFI work) | 18:17 |
17:52 | FAC | Tyler | LVEA | YES | 3IFO checks | 18:07 |
18:15 | ISI | Jim | HAM Shack | n | CPS work on HAM8 | 19:08 |
18:45 | OFI | Camilla, Josh | Optics Lab | y(local) | Getting beam ready for KTP swap | 20:24 |
18:45 | FAC | Richard | LVEA | YES | Checking on OFI work status | 19:14 |
18:52 | PCAL | Tony | PCAL Lab | y(local) | Checking chassis for sending to LLO | 19:20 |
18:58 | PCAL | Dripta | PCAL Lab | y(local) | Joining Tony | 18:59 |
19:46 | FAC | Tyler | MX, MY | n | 3IFO checks | 20:07 |
20:00 | SUS | RyanC | LVEA | YES | Restarting dust monitor | 20:12 |
20:12 | FAC | Chris | MX | n | Finishing up light fixture pickup | 21:29 |
20:45 | OFI | Sheila, Jason, Naoki | LVEA | YES | Continuing OFI work (Sheila out 23:01) | 23:30 |
20:55 | OFI | Jenne | LVEA | YES | Continuing OFI work | 23:30 |
21:21 | OFI | Camilla | LVEA | YES | Helping out with OFI | 21:54 |
21:34 | VAC | Jordan, Gerardo | EX | n | Grabbing leak detector | 22:45 |
21:35 | SEE | Tony, Genevieve, Sam, Mattia | Roof | n | Looking at the beautiful landscape and arms | 21:48 |
21:50 | ISI | Jim | EX, EY | n | Recovering HEPI and ISIs | 22:17 |
22:06 | safe | McCarthy | LVEA | YES | checking on ofi work status | 22:44 |
22:45 | VAC | Gerardo | LVEA | YES | Doing vacuum checks | 23:02 |
22:55 | EE | Jim, Fil | EX | n | Figure out HEPI pump at EX | 23:32 |
23:11 | TOUR | Camilla + 3 others | LVEA | YES | Looking at OFI work |
23:33 |
Site wide power glitch at 13:43:30 PDT (20:43:30 UTC) Tue 23rd July 2024. Lights in corner station flickered. Both end station HEPI Pump Controller VFDs tripped.
Jim untripped the EX VFD, but the HEPI pump controller does not seem to have control. Jim and Patrick are investigating.
If it seems we have had a lot of power glitches recently, that's because we have, 6 in the past month.
(all times local PDT)
Tue 23 Jul 2024 | 13:43:30 |
Sun 21 Jul 2024 | 12:50:08 |
Tue 16 Jul 2024 | 10:58:55 |
Sun 07 Jul 2024 | 13:51:31 |
Mon 24 Jun 2024 | 09:46:28 |
Sun 23 Jun 2024 | 20:48:15 |
The ISI watchdogs for both ST1 and ST2 on the ETMs tripped seemingly randomly this afternoon at 20:43UTC. From the CPS sensors on ST2 and the T240s on ST1.
Dew point measurement done this morning, read at -43.4 oC. There was some demand already on the system from HAM5, since both soft covers were off. No demand from HAM6 or HAM7. Flow was opened later to HAM6, since more personnel started working in-chamber. HAM7 remains valved out.
I took the OPLEV charge measurement for the both the ETMs this morning as they were free. As I started I noted that ETMX had an FPU error (floating point unit), and during the measurement ETMY had lots of overflows, all stemming from H1:FEC-98_DAC_OUTPUT_3_3 (ETMX did not have any overflows).
To center the OPLEVs I had to do the following slider moves
ETMX sliders: P -42.7 to -57.8, Y -147.7 to -131.3
ETMX's charge appears to be increasing and high, its at or above 50V on all quads/DOF.
ETMY sliders: P 140.1 to 170.8, Y -162.8 to -149.0
ETMY's charge seems stable and low, hovering around 0-50 V on all the quads.
After I was finished I restored the sliders and re-misaligned the ETMs as they were when I found them.
We aligned the AUX laser in HAM5 so that it is roughly centered on OM1 AND is retroreflected by SRM. We haven't checked anything else.
Retroreflection was measured/evaluated using an iris right in front of the AUX laser launcher telescope. First the iris was well centered relative to the input light (1st attachment shows the scattering around the iris when it was closed down a bit), and we used a steering mirror and a beam splitter installed between the AUX laser and the SRM to get the SRM reflection coming back to the iris AND SRM transmission hitting the center of OM1 without touching SRM. It was easy. 2nd attachment shows the return beam on the iris after REALLY closing down the iris so the return beam clips on it. Centering on OM1 was based on just eyeballing using a sensor card.
We don't know where on the SRM or OFI the beam was (no easy reference). It seems that the beam was seen by ASC-AS_C but not centered on it.
The above was done before we were informed about a large ISI/HEPI rotation in YAW (alog 79272) so probably we'll do it again after moving SRM to compensate to get closer to the right alignment quickly (rather than walking the beam from where we are now slowly, checking the OM1 centering and SRM retroreflection many, many times).
In the end, we should make the SRM transmission hit the center of AS_C, make the beam retro reflected by SRM, and make the SRM reflection hit the center of SR2, all at the same time. For that, probably we'll have to make a minor adjustment to SRM.
We also did a bit more looking at the Fast Shutter. While the optical surface and wires appear fine, there is also a strange heat/burn mark on the side of the toaster optic, low. Possibly the heat mark from the bumper bar above reflected something down to this side surface??
Note, best last pictures of Fast Shutter from last vent are at alog 60724.
Tagging for EPO.
Rick Savage, Dan Chen, Shingo Hido, Emmanuel Makelele and Dripta.
We went down to EY on Thursday, July 18th, 2024 to do a Pcal measurement, mostly to show the measurement procedure to our visitors. We used the procedure outlined in T1500062-V17 as a guide. A scanned copy of the filled out measurement procedures and log is attached.
Before we began the measurement, a picture of the beam spot position was taken. It shows that the beams were centered on the Rx sensor apreture (BeamSpotBefore photo attached).
As noted in the scanned copy, after the first background measurement while WS was placed in the Tx module, the shutter stopped working. We could not open the shutter locally or remotely. The shutter has now been removed from the EY Tx module for troubleshooting. Pictures attached.
We continued with the measurement manually shuttering and unshuttering the laser. After taking all the measurements, a beam position picture was taken. It shows that the bemas remained centered and the Pcal beam spots did not drift significantly during the measurements (BeamSpotsAfter photo attached).
Analysis and results/plots to follow.
The analysis and report can be found in git: https://git.ligo.org/Calibration/pcal/-/tree/MergingBranch/O4/ES/measurements/LHO_EndY/tD20240718?ref_type=heads
The report LHO_EndY_PD_ReportV3.pdf shows that the latest Rx reponsivity measurement is within 5 hop (hundredths of a percent) of the mean value and the optical efficiency is within 10 hops of the mean optical efficiency value.
Genevieve and Sam asked about HAM1 and HAM2 motion around 40 hz. I hadn't look in detail in this frequency band for a while, this is typically higher frequency than we are worried about with ISI motion. But it turns out HAM2 is moving a lot more than HAM3 generally over 25-55hz, and particularly around 39hz. It looks like it might be due to gain peaking from the isolation loops, but could also be from something bad in the HEPI to ISI feedforward. The extra motion is so broad I don't think it's just one loop has a little too much gain, so I'm not sure what is going on here.
First image are spectra comparing the motion of the HEPIs for those chambers (HAM2 HEPI is red and HAM3 is blue) and the ISIs (HAM2 ISI is green, HAM3 is brown). The HEPI motion is pretty similar, so I don't think it's a difference in input motion. HAM2 is moving something like 10x as much as HAM3 over 25-55hz. The sharp peak at 39 hz looks like gain peaking, but I'm not sure that explains all the difference.
Second plot shows the transfer functions from HEPI to ISI for each chamber. Red is HAM2, blue is HAM3. The 25-55hz tf for HAM3 is not very clean probably because HAM3 is well isolated. HAM2 tf is pretty clean, it makes me wonder if maybe something is messed up with feedforward on that chamber. Maybe that is something I could (carefully) fix while other troubleshooting for the detector is going on.
I looked at some of my design scripts and realized that the HAM3 FF X filter is probably a bit better fit, so I copied that into the HAM2 foton file, loaded and engaged it on HAM2. It improved the 50ish hz motion quite a bit, but HAM2 is moving more than HAM3 still. Probably some tuning that could still be done here.
Looked further into the peak at ~40Hz and found an improvement in coherence after the re-tuning Jim did. Image 1 shows the peak pre-tuning, and image 2 shows it post-tuning.