Dew point measurement taken this morning read at -43.6 ^oC.  Measurement taken before any activity inside chambers.  Soft covers were on HAM5 and HAM6, HAM7 is isolated.

A slow motion video of the fast shutter, firing with the high voltage driver in air, is here:  slow motion video

Thu Aug 01 08:07:40 2024 INFO: Fill completed in 7min 36secs

TITLE: 08/01 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: 1mph Gusts, 0mph 5min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.05 μm/s
QUICK SUMMARY:

Today we'll be closing upu HAM6!

After transition to laser safe, I unlocked HAM6 ISI, did a small balance adjustment and ran some close out tfs. TFs look okay. I think SEI is ready for doors to go on.

TITLE: 07/31 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Corrective Maintenance
SHIFT SUMMARY:
I know that there have been a lot of Laser trasitions done today...
But

The LVEA IS  currently in LASER SAFE.

OFI work has continued all day :

1. ✅Measure Isolation - new simpler plan suggestion from LLO (cube between SRM and OFI…)  Backup - Need Aux laser in HAM6 as LLO#58791, 58848
   1. If out of spec, adjust TGG crystal location (slots in mount)
2. ✅ Inspect/deal with beam dumps if not done already
3. ✅Squeeze beam alignment Check, AS and WFS
4. ✅Check OFI rejected PD path alog59906 KPT fwd rejected (use WP before OFI)

Before closeout 

1. ✅ Robert in-chamber pictures
2. ✅Finish testing Fast Shutter, trigger HV
3. See HAM6 closeout checklist
4. ✅ Correct OFI osem magnet(s)
5. ✅ Rebalance  OFI
6. Reinstall OFI Glass shroud
7. ✅ Re Check AS and WFS (Not checking WFS)
8. ✅ Turn on laser for final alignment check 
9. ✅ Remove all retro reflector, iris and AUX laser parts
10. Unlock ISI ( Jim is unlocking HAM5 but not HAM6)

LOG:

Ryan Crouch has Transitioned the LVEA to LASER SAFE.

Work Permit 12014

Betsy, Rahul

This afternoon, Betsy adjusted the SD magnet on the OFI and we confirmed that it is sitting correctly in it's place. Next, she inserted the AOSEM and centered it on the magnet (polarity was already checked). We also took this opportunity to take the OLC/offsets/gain for the SD aosem, which is given below,

OLC = 17000, offsets = -8500, Gain = 1.739 (30,000/OLC). This has accepted in the SDF.

The in-air transfer function measurement results are attached below (we took only 3 averages) and they look healthy for all three dof - template at /ligo/svncommon/SusSVN/sus/trunk/OFIS/H1/OFI/SAGM1/Data

We then started attaching the OFI shroud as per D11800103 - the top two, side (+X side) and front shroud has been attached. Mitchell joined us to help with attaching the top and one of the shrouds. There are two/three more panels left to be attached, which will be done once Sheila is done with the beam alignment check.

Sheila has Transitioned the LVEA to LASER Hazard.

Work Permit 12013

Sheila, Betsy, Keita, Camilla. Continuing from 79373. Measured in 2021 in the lab in 59410.

Betsy and Sheila set up of the power meter in location B of 79373 with the wave-plate rotated such that the beam is visible. Distance between OM1 and retro-mirror is ~350mm, before the fast shutter.

The retro-refection wasn't perfect. Betsy and Sheila found that the HAM5 iris centered on the forward aux laser isn't well centered on the beam retro-reflected from the mirror in HAM6. This made it hard to block the ghost beam (direct reflection, no change in polarization) without also blocking the retro-beam that we want to measure. There is also a bright rejected beam headed to ZM6 which is only there as the waveplate is changing polarization is making some of the beam rejected by the TFP.  They touched the retro mirror to improve it.

They alternated power measurements from position B (the beam that should be isolated by the OFI) and then position A (to measure the power from the laser). Used 10 seconds of statistics mode data for each with the Thorlabs power meter.

Starting measurements at 10:01 PT:

• Position B (isolated by the OFI): 1) mean 1.025uW stdev 25.55nW, Blocked/Background 809.0nW stdev 2.227nW, 2) mean 1.056uW stdev 12.11nW, Blocked/Background 845nW stdev 8nW, 3) mean 1.015uW stdev 1212nW, Blocked/Background 822nW stdev 4nW
• Position A (power from the laser): 1) mean 7.589mW, stdev 96.83uW. Blocked/Background 685.7nW stdev 12nW 2) mean 7.708mW, stdev 41.13uW 3) mean 7.742mW, stdev 47.93uW

Similar measurements by LLO in 58791 and 2021 from LHO in lab 59410.

AS_C sees this beam, measuring 360uW. It is not centered, -0.4 in Pit and -0.4 Yaw, see attached. When we set up the aux laser it was also off in this direction (-0.6, -0.6) 79300: similar enough.

Betsy and Shieal added a waveplate before the OFI in the AUX path and checked that the forward KTP rejected beam to OFI_B was seen, attached.

In parallel, we turned on the SQZ laser and checked that the SQZ dither lock was stable (0.94mW on OPO_IR_PD) with 75mW of SEED injected. Keita and I opened SQZT7 and adjusted ZM4 and ZM5 to be better centered on the irises. We still didn't have much beam on AS_C but after I further adjusted ZM4 (sdf's not saved), we could see it, see attached.

Betsy is working on replacing the osem magnet I knocked from it's correct position in 79316.

Dew point measurement taken this morning read at -43.9 ^oC.  Measurement taken before any activity inside chambers.  Soft covers were on HAM5 and HAM6, HAM7 is isolated and a bit pressurized.

Keita, Sheila

Summary:  We chipped the spare KTP crystal this morning, and this afternoon installed the back up spare that Rodica had shipped.  We've adjusted the roll, and the pitch angle seems better than the crystal that we removed.  So this should be ready to go into the chamber first thing Monday morning.  We have many photos from today, which will be attached and annotated to this alog later. 

Following on From Jason's alog 79319

With this placement of the damaged KTP in it's assembly, where the assembly is bolted perpendictular to the beam path, and a wave plate to mix the polarizatoins upstream of the KTP,  we have 13.5mW in the p polarized beam (see first attachment which is a diagram Paul sent us this morning), 16.3mW in the s polarized beam, and 2.3 mW in the AR surface.  This is not set up with the AOI that the AR coating is designed for, which is why the AR beam is large, we can take advantage of this to set the pitch by setting the AR reflection parallel to the table.. 

With the original KTP in place, the AR reflection isn't parallel to the table it is pitched up by 10/(530 +405 mm) about 11 mrad. The optic lab beam is hitting the KTP a little below the burned spot, which would have been on the +X side in chamber.  The burned spots are on the side closer to our alignment laser.

Before taking it out of the mount we took a variety of photos showing the damage spots position.  We did not find any indium foil in the mount, Paul had warned us that there might be indium between part 5 and part 9 of D2000038. 

As we were placing the new crystal in the mount, we left the set screws (11) that hold the peek loose, and held the piece upsidedown while we screwed in the bolts labeled #10 to hold on the aliuminum plate.  It chipped as we were tightening the bolts labeled 10 in D2000038. After some discussion with Rodica, Paul, Gabriele, we went back to the lab to take photos of the chip and try to understand how the chip happened.  We have photos showing that the crystal was proud of the top of part 5, the orientation of the black metal piece.  After we removed the black front plate, we could see that the KTP was firmly stuck in part #5, with the wedge stuck.  Keita had to push on the back of the crystal to get it loose. 

Keita made a series of measurements using calibers:

Chipped KTP: (agrees well with the drawing: E1900284)

• height on thicker side: 0.8850 inches
• heght on thinner side: 0.8845 inches
• width (center to center): 0.8870 inches
• width from one corner to the other (longest width): 0.9360 inches
• thickness: 0.5055 for thicker side

part 5: https://dcc.ligo.org/DocDB/0171/D2000567/001/D2000567_A%2B_OFI_KTP_Wedge_Holder.pdf

• side to side width of the opening for the crystal (measured on the side where the black part attaches) 0.9225 inches
• depth of the slot 0.515 inches on the deeper side.
• depth of the slot 0.458 on the thinner side
• height of the slot, including space for peek, 1.003 inches

peek:

• thickest part 0.1105 inches
• thinnest part: 0.1095 inches

total height (max): crystal + peek = 0.885+0.1105 = 0.9955 inches, smaller than 0.2mm than the height of the slot.

cratered KTP:

• height of crystal at thick side 0.8855 inches
• height of crystal at thinner side: 0.8835 inches
• width (center to center): 0.887 inches
• width diagonal: 0.9345 inches
• thickness of thicker side: 0.5095 inches

We then did a trial run (using the chipped KTP) of an approach that we think avoids the problem of letting the KTP get wedged in the holder.  We set the KTP on several wipes on the bench, and set the peek underneath it.  We then slid the holder (part #5) over this whole thing, which went smoothly, and tightened the set screws.  After flipping it over, we can see that the KTP is not proud of part #5, and it sits nearly flush to the front of the holder.  We could then easily attach the black front plate.  We decided to do this with the final spare, which had 2 small chips on the edge. 

With that spare installed in the assembly, we adjusted roll using the alignment laser that Camilla and Jason set up.  We wanted to adjust roll so that the transmitted beams were level to the table, since we know that the laser bea we started with were parallel to the table.  The roll adjustment was sticky, and tightneing the set screw tended to lower the transmitted beams.  The beams transmitted are off in yaw compared to the ones from the cratered KTP, by about 7mm/870mm + about 8 mrad.  We had difficulty seeing the AR reflected beam, but we can see a tiny beam with all the lights off (this suggest that the reason the beam was so bright before was the coating damage, not the AOI of the crystal in our set up.). At 820 mm from the KTP, the AR beam was about 1 mm too low, so it's pitched down by 1mrad. 

We think this is about as good as we can do by adjusting with this mount, so we are satisfied and will leave the KTP assembly under wipes and foil to be reinstalled on Monday.

C. Compton, S. Dwyer, J. Oberling

This afternoon we prepared the KTP wedge assembly for swap and realignment.  Camilla had already mostly prepped a beam path for this using the beam reflected from the PBS cube in front of the Prometheus laser, but there was some oddness with the beam so Sheila and I moved one of the mirrors so we could use the beam transmitted by the PBS cube.  There was still oddness with the beam when at low power (looked like it had a bit of a halo around it), but it went away at a slightly higher power (a couple mW vs just under 1 mW).  Moving on, we aligned the beam along a row of holes and then installed the KTP wedge assembly (after Sheila wiped the area down several times with IPA wipes).  We had removed the beam dump assembly before placing the KTP wedge in the beam path, and the bolts were very tight.  It looked like the black coating on the assembly was also in the threaded bolt holes; this coating had been rubbed off by the bolts during assembly, and it looked like this was the cause of the difficulty in removing the beam dump assembly (there was coating visiblt deep in the threads but none on the outside where the bolt fully contacts the threads).  A HWP was placed in the beam so we could adjust the power in the beams transmitted by the KTP wedge.

With the KTP wedge assembly in place we found the two transmitted beams and set irises in the near and far field, 2 irises for each beam.  We also found the beam reflected from the front surface of the KTP wedge and placed an iris in this beam as well.  I placed beam dumps to block the beams so there are not unblocked beams when the laser gets turned on.  To preserve the cleanliness of the KTP wedge assembly I placed several layers of dry wipes over the assembly and then covered it with foil; I then wiped the area down again with IPA wipes.  The KTP wedge assembly is now ready for the damaged KTP wedge to be swapped with a spare and realigned; Keita and Sheila plan on starting the swap and realignment tomorrow.

I've attached several pictures of the setup and they are, in order:

1. The 2 near field irises behind the KTP wedge (with beam dump between KTP wedge and the irises)
2. The near and far field irises
3. The reflected beam iris and its beam dump
4. Another picture of the KTP wedge assembly
5. Foil covering over KTP wedge assembly (with several layers of dry wipes between the foil and the KTP wedge assembly)

NOTE: There is now a Class A assembly in the Optics Lab.  Please observe ALL posted contamination control signs when entering the Optics Lab, and DO NOT enter the far cleanroom (with the Prometheus laser on it) unless you are working on the KTP wedge assembly swap.  This assembly is going back into the vacuum envelope, so we have to do our absolute best to preserve its cleanliness.  Thank you.

C. Compton, S. Dwyer, J. Oberling

This morning we removed the KTP wedge assembly (D2000038) from the OFI and moved it into the OSB Optics Lab.

We began by trying the "transport shims" that are supposed to help secure the OFI.  Unfortunately, these did not work.  The slot in the shims was not wide enough to fit around the OFI Earthquake Stop Posts we were supposed to fit them around, and the shims were too skinny (the posts bottomed out before contacting the shims).  So we had to pivot to Plan B, which was to use dog clamps instead.  This mostly worked, but the OFI still moved around enough that we decided one of us would try to support the OFI while the other turned bolts.  Camilla has some pictures of this and will post as a comment to this alog.  Even still, we managed to almost immediately dislodge one of the OSEM magnets (the one near the lone +X/+Y OSEM) as soon as we started trying to remove the KTP wedge assembly (the magnet is still stuck to the flag on the OFI, will need to have its polarity checked and be put back in place).

We first placed a teflon sheet in between the KTP wedge and the quartz rotator assembly.  Using non-magnetic tools (a titanium hex key that had been bent so it would fit in the space between the KTP and FS wedges, and a beryllium copper one that had been cut short) we attempted to remove the beam dump assembly from the KTP wedge assembly.  Camilla held the OFI and I tried to loosen the bolts holding the beam dump on the KTP wedge.  I say "tried" because the bolts are frozen in place.  We were unable to get them to move, at all.  Pivoting again, we found that the beryllium copper hex key was short enough to fit under the beam dump assembly, so we began loosening the two bolts on the +Y side of the KTP wedge assembly; Camilla had to crawl in the -X door to access the -X bolt while I held the OFI.  This worked until the -X bolt was loose enough that we could no longer fit the hex key under the beam dump assembly.  At this point Sheila used a T-shaped titanium hex key to loosen the -Y bolt on the KTP wedge (the bolt directly under the quartz rotator) while I held the OFI, and then I loosened the +X bolt.  With these 2 bolts loose we were able to lift the KTP wedge assembly enough that Camilla could fit the hex key under the beam dump assembly again.  In this way were able to slowly work the -X bolt free.  With all bolts free I carefully removed the KTP wedge assembly while Sheila held the OFI.  We Ooohh'd and Ahhhh'd at the craters in the KTP wedge for a bit and took some photos (see attached), and Camilla and Sheila grabbed some more pictures of the back side of the FS wedge (more access, and therefore better viewing, with the KTP assembly out of the way).  We also removed the teflon sheet from in front of the quartz rotator.

We ensured all of the non-magnetic tools were separate from other tools in the cleanroom, safely wrapped up the tools we would need as well as the KTP wedge assembly, and moved everything to the optics lab to start prepping for swapping and realigning the KTP wedge assembly (the beam dump assembly will have to be removed in the Optics Lab).  I've attached a few closeup pictures of the KTP; 2 are viewing the front surface and one is viewing the back surface (better view of the coating damage around the craters).  Camilla has several other pictures that she'll attach as a comment to this alog.

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:

• 1 1/4 in above EQ stop
• 1cm in +x from the center

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:

• 1 1/2 in above EQ stop
• 1cm in +x from the center

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:

• 2 1/4 in above EQ stop
• 3/4 in from +x EQ stop
• yaw got "worse"

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:

• 1/2 in away from horizontal EQ stop
• Went wrong direction

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:

• 1 1/4 in away from horizontal EQ stop (nice.)
• 2 1/2 in above bottom of EQ stop

*LUNCH BREAK*
 

Sheila back to SR2;

• 2 1/2 inch above bottom of EQ stop
• yaw is still good

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

• 1.72mW before SRM
• just after SRM 0.605mW
• before OM1 0.380mW
• 0.45mW after TGG before TFP

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.