Thu Jul 25 08:08:24 2024 INFO: Fill completed in 8min 20secs
Jordan confirmed a good fill curbside.
TITLE: 07/25 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: 0.06 μm/s
QUICK SUMMARY: We went to laser safe yesterday afternoon and are ready for today's work
Today's plan:
Jason, Jenne, Camilla, Keita, Francisco, Naoki, Sheila. (Please see Francisco's alog for more details 79300)
Today we got the alignment laser set up and the sqz beam checks done in a way that we think is good enough to move forward with removal of the KTP tomorow. There are more detailed notes in other alog drafts, and photos coming.
We found this morning that the beams were not where they were left last night on the OM1 + retro reflection irises. We decided that this was likely due to the wobbly mount with sticking knobs that the steering mirror was in, this would change the alignment from being touched, and sometimes turning the knob did not adjust the alignment because the knob wasn't engaged. We decided to swap this mount out which took some time, but after that things went smoothly, and with about 3 iterations we were able to center the beam on SR2. We then did a quick check of the squeezer beam, which goes through the OFI and returns to OM1. We got some cool photos of showing a hole in the middle of the beam; we intentionally set it's alignment to go through the most recent crater.
We are ready to go to laser safe, and the door crew plans to take HAM6 door off in the morning. After that we will remove the KTP assembly.
Camilla, Jason, Jenne, Keita, Sheila, Francisco, Naoki
Summary: We are done for AUX laser alignment and power measurement of AUX laser. SQZ beam got to OM1, but we did not do power measurement due to noisy seed dither lock. The following are a mixture of notes between Camilla, Francisco, and Naoki regarding the changes done today:
Aiming for 2 1/4" above EQ stop as 4" between vertical stops and the center of SR2 optic is 5.5mm above center line of EQ stops.
At start of the day, someting had drifted (mainly pitch), re-centered AUX laser on irises.
*Iterating moving auxiliary laser mirror and beamspiltter to center in om1 and retroreflection irises.*
Checking position at SR2:
Swapped the AUX laser steeing mirror to a better optic mount and not woberly perdistal, we are blaming this for our drift.
Jenne also adjusted SRM sliders to yesterdays values.
*Iterating moving auxiliary laser mirror and beamspiltter to center in om1 and retroreflection irises.*
Checking position at SR2:
Moved SRM osems from (175, 140) to (50,190). In pitch moved -125urad from 175 to 50 on osems. In yaw moved +50urad. this was 140 to 190 on osems
Aiming to center the beam on SR2
*Iterating moving auxiliary moving mirror to center in om1 and retroreflection irises.*
Checking position at SR2:
EQ stops are 2 1/2 in away from each other; center is 1 1/4 in from horizontal EQ stop
Will do 100 microrad in -YAW, then check retro in OM1. -100urad in yaw is 190 to 90 on osems
*Iterating moving auxiliary moving mirror to center in om1 and retroreflection irises.*
Checking positions at SR2:
In yaw going +300 urad. This is 90 to 390 on osems.
*Iterating moving auxiliary moving mirror to center in om1 and retroreflection irises.*
Checking positions at SR2:
*LUNCH BREAK*
Sheila back to SR2;
earlier today SRM P moved from 179 to 50. 1 1/4 inch move on SR2
Moved 1/4 inch backward. moved SRM P from 50 to 76
Sheila is happy with SR2 centering.
Jason is setting iris on OM1. Beam on OM1 ugly? due to crater on OFI?
ASC_AS_C P -0.6 Y -0.6
open GV for HAM7. send SQZ beam. seed dither lock is very noisy.
SQZ beam is close to AUX laser?
AUX power measurement
First three attached photos are of the aux laser steering mirror we swapped in, original mirror in 79253.
Fourth photo is the iris we places between the aux laser beamsplitter and SRM. Once we were finished with the alignment Jenne and Sheila recentered this iris on the beam.
The power measurements recorded are with the AUX laser as we had trouble dither locking the SQZ seed beam. More details:
Sixth image is the SQZ beam and aux laser beam (smaller) after SRM. They are misaligned in yaw.
Seventh image is te SQZ beam and aux laser beam (below) before OM1. They are misaligned in pitch.
Tagging for EPO.
Dew point measurement taken this morning by Jordan, read at -43.9 oC. Some demand by HAM5/6, small crew at work.
End of the day dew point measurement, -43.6 oC. No demand, all soft covers closed for HAM5/6 and HAM7 is under small pressure and isolated.
Note regarding HAM7: before the 10" gate valve is open, chamber needs a blow down, see a vacuum representative.
TITLE: 07/24 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Corrective Maintenance
INCOMING OPERATOR: None
SHIFT SUMMARY: The OFI team was able to get the AUX laser aligned and verified that the SQZ beam can get to OM1. Tomorrow morning first thing we will be transitioning the LVEA to laser safe and continuing the OFI work by taking the KTP out and taking the HAM6 -X door off.
LOG:
- Continuing work on aligning AUX laser
- Aligning sqz beam
- Getting ready to transition to laser safe
| Start Time | System | Name | Location | Lazer_Haz | Task | Time End |
|---|---|---|---|---|---|---|
| 15:11 | FAC | Kim, Karen | LVEA | YES | Tech clean, (Karen out at 1600) | 16:23 |
| 15:20 | VAC | Jordan | LVEA | YES | Checking purge air | 15:31 |
| 15:41 | OFI | Camilla, Jason, Sheila | HAM5 | Y | AUX laser work | 19:41 |
| 16:10 | OFI | Keita | LVEA | YES | OFI work | 19:41 |
| 16:11 | FAC | Richard | LVEA | YES | Checking in on OFI work | 17:34 |
| 16:38 | FAC | Karen | WoodShop | n | Tech clean | 17:27 |
| 17:25 | FAC | Kim | MX | n | Tech clean | 18:27 |
| 18:09 | FAC | Karen | EY | n | Tech clean | 18:58 |
| 18:28 | OFI | Francisco | LVEA | YES | Helping with OFI | 19:41 |
| 19:12 | ISI | Jim | EY | n | Recovering EY from HEPI/ISI trip | 19:46 |
| 19:15 | Richard | LVEA | YES | Checking in on OFI peeps | 19:41 | |
| 20:41 | OFI | Camilla | LVEA | YES | More AUX aligning for OFI | 23:30 |
| 20:50 | OFI | Jenne, Naoki, Sheila, Jason | LVEA | YES | Continue AUX alignment work for OFI (Sheila, Jenne out 22:55)(Naoki our 23:08)(Jason out 23:27) | 23:27 |
| 21:51 | VAC | Gerardo | LVEA | YES | Purge air for HAM7 | 22:02 |
| 21:29 | VAC | Janos | EY | n | Purge air photos | 21:48 |
| 21:49 | FAC | Tyler | LVEA | YES | Prepping for HAM6 door removal | 21:52 |
| 22:10 | OFI | Keita | LVEA | YES | OFI help | 22:55 |
| 23:08 | EE | Marc, Fil | MY | n | Looking for parts | ongoing |
| 23:09 | FAC | Tyler | LVEA | YES | More prep work for HAM6 door | 23:13 |
Keita, Jennie W
Keita and I worked out the distance behind SRM we have to place the AUX launcher to match the beam radius the IFO beam normally has on SRM on its way into the OFI.
This is based on measurements of beam profile Keita made in the optics lab with the aux laser mounted with a collimator on it.
The code used to do this is saved in ligo/home/jennifer.wright/ModeMatching/beam_diverg.py
The graph attached shows the measured points in orange and the fitted points in blue.
Beam waist, w0 is 0.916 mmBeam waist position in relation to front of launcher , z0 is -1.423 mRayliegh range for beam, z_R is 2.477 m Move launcher 3.986 m away from SRMDistance between OM1 and SRM is 3.646 m
FAMIS 21009
The stabilization trends are especially interesting this week; PMC reflected power is steadily increasing while transmitted power (along with RefCav transmission and ISS diffracted power) is decreasing. This is particularly interesting as we thought this behavior might disappear when we swapped in the new PMC.
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.
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.
End of the day dew point measurement, -43.0 oC.
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.
