R. Crouch, J. Oberling

Yesterday we began measuring the locations of the vacuum chamber support tube ends using the FARO laser tracker.  We started with the support tubes for the WBSC3 chamber and the +X ends of the WBSC2 support tubes as these were the most readily accesible.  The remaining support tubes in the LVEA (WBSC1, WBSC2 -X ends, and all WHAM chambers except WHAM7) have iLIGO-era PEM Interface Plates on them that block the support tube; some of these plates have undocumented spacers between them and the support tubes they are attached to, meaning we cannot accurately locate the support tube end w.r.t. the PEM interface plate and therefore making an accurate measurement of the support tube location impossible.  As an aside, Jim is in the process of removing these plates from the chambers (so far WHAM3 and WHAM4 are complete, WHAM1 and WHAM2 are 75% complete), so we can get at these support tube ends as the opportunity arises (he will then reinstall these plates, as they make for very convient mounts for dial indicators).

Measurement Method

This is a fairly straightforward measurement, but there is a somewhat subtle "gotcha" that needs to be accounted for to get an accurate measurement.  But first things first, we aligned the FARO to the LVEA's Building Coordinate system using our red alignment nests, then applied the X and Y axis rotations required to align the FARO to the site global coordinate system (see T0900340 for a brief overview of the coordinate systems in use).  We then loaded CAD models of the support tubes, that Ryan downloaded from the SolidWorks vault with each model in the site global coordinate system, into the FARO's control software, PolyWorks.  PolyWorks automatically reads the coordinate system information contained in the CAD files and places these models in position w.r.t. to the site global coordinate system.  This gives us nominal locations of the support tube ends, a guide for our measurements, and also a nice visual reference for where everything is positioned.

Now for the "gotcha."  The physical support tubes have a hole in the center of each end that is not represented in the CAD model, and this hole is large enough that the FARO target (a Spherically Mounted Retroreflector, or SMR, with a 1.5" diameter) sits slightly inside the hole.  This means that when you're taking a measurement of the center of the support tube end using this hole the SMR is not measuring the location of the actual support tube end, it is a few mm inside of it.  To account for this we did the following:

1. Use the SMR to get the coordinate corresponding the the axial length of the support tube on either side of the end and calculate the average (to remove any yaw in the support tube)
   • Using WBSC3 as an example, the support tubes lie parallel to the y-axis.  So we touch the SMR to either side of the support tube and record the y-axis coordinate, then calculate the average
   • We do this for each individual support tube end, as each one is slightly different
2. Use the SMR to get the same coordinate, but this time with the SMR sitting in the center of hole of the support tube
3. Calculate the difference between the two, to get the offset required for an accurate measurement
4. In the PolyWorks software:
   • Use the CAD model to create points representing the center of each end of the support tube
   • Create a line between each end point, representing the theoretical centerline of the support tube
   • Create a Measurement Point by offsetting the support tube end point along the centerline and to the inside of the support tube by the amount calculated in steps 1-3
5. Congratulations, you now have a measurement point that represents the nominal location of the support tube end, taking into account the offset required due to SMR positioning inside the center hole

To take the measurement we used the Build/Inspect mode in PolyWorks.  In this mode we have to be sure to select the "Towards Object" compensation method, which automatically compensates for the radius of the SMR (3/4", or 19.05 mm).  If "None" is selected the FARO measures to the center of the SMR, but our measurement point is at the edge of the SMR, since that's what is physically touching the support tube, so we need to compensate for that radius.  This gives us the deviations of the measurement point, which can then applied to the point representing the center of each support tube end to give their measured location.  The results of our measurements are shown in the attachment.  Since we had measurements for each end of the WBSC3 support tubes I also added a distance feature representing the measured length of each WBSC3 support tube.

Wrapping Up

Some points for discussion/further thought.  Keep in mind that the BSC support tubes are not exact representations of where their respective optics are; we only aligned the optic during aLIGO install, and in the end didn't really care where the support tubes ended up as long as HEPI had enough range to work.  This means that any deviation from nominal seen in the support tube ends is not an indication of misalignment of that chamber's optic.

1. The WBSC2 support tubes were supposed to be lowered by ~2.5 mm to account for the BS z-axis position being at -82.9 mm instead of -80.0 mm; this was done because, while the 4km arm cavities are flat in global coordinates the IFO input and output arms are not, so the BS had to be lowered to properly direct the beam (which rises in elevation while traversing the PRC) into the arms.  Therefore our expectation is that the WBSC2 support tubes are below the nominal z-axis coordinate of 1130.3 mm (we recently discovered that this change was not accounted for in the SolidWorks models for the sites).  While the global z-axis coordinate for all BSC support tubes is 1130.3 mm, if WBSC2 was lowered as required we would still expect to see a z-axis deviation in the measured points, but this is clearly not the case.
   • I was at LLO working on PRC alignment when the WBSC2 in-chamber alignment was started, so I have no memory of the initial positioning of the BS in-chamber; this was done by Hugh Radkins and Doug Cook (I had returned in time for pitch/yaw alignment).  Looking back at their notes they had to move HEPI +X by 4.6 mm, -Y by 2.3 mm, and +Z by 0.4 mm to position the BS, so this does not fully account for apparent lack of support tube lowering.  But as stated above, this does not necessarily mean the BS is too high (we'll know that for sure when we measure it once WBSC2 is opened in March 2026).
2. The measured length for the WBSC3 support tubes is shorter than their as-designed length of 3657.6 mm.  Not sure why at this point.
   • Once we get more full BSC support tube measurements we'll have more info to work from
3. The WBSC3 +X/-Y support tube end is a decent bit further in the +Y axis than expected.  Again, not sure why.
   • Looking back at my notes from install we had to move WBSC3 HEPI in the +Y dircection to properly place ITMx, so the overal deviation direction of these support tubes isn't a surprise.

This work was associated with LHO WP 12947, which also included the WBSC1 +X support tube ends.  Those support tubes still have PEM interface plates installed, so we are currently unable to measure them (will do in the future once the plates are removed).  Since we completed the rest of the measurements involved, I've closed the WP.

J. Kissel, D. Sigg, D. Barker
ECR E2100485
ECR E2200401
WP 12901

Continuing on the deprecation of 18-bit DAC path (ECR E2100485), we upgraded the h1iscex's DAC0 card today from an 18- to a 20-bit DAC. One of the front-end models that use that DAC is the h1pemex model.

Here's the before vs. after for the models. While there, I found and left the new ADC card from ECR E2200401's PEM sensor array expansion. I'd thought it was installed solely for characterizing the 32CH LIGO DAC, but it had only been temporarily used for that. It should be there! And also, the electric field meter ADC should also remain there.

If the PEM team wants to account for the factor of 4x gain change in the DAC calibration, I installed new DACOUTF filters upstream of the GDS filters that are used to drive the DACs.

The model has been committed to
    /opt/rtcds/userapps/release/pem/h1/models/
        h1pemex.mdl : r28026 --> r34059

Randy and I installed new CR ceiling.

Betsy had a local company fabricate a C3 ceiling for our Mega Cleanroom. This ceiling has velcro opening to allow access for Septum removal. Opening extends to end of CR opening on the -X side and ends just short of the +X opening. 

J. Kissel, M. Todd, S. Dwyer

Just recording this for posterity in case: Matt and I wanted to (continue) parallelizing our work on characterizing the ISS Array at full / nominal power (60W into the PSL) and characterizing RPM dynamics for future HSTS Estimator modeling, respectively. The estimator team discovered a week or two ago that PRM has a different dynamical response when the SUS is ALIGNED vs. MISALIGNED. So, I misaligned IM4 and PR2 to ensure the 60W didn't go anywhere but a fixed location, and aligned PRM. 

The worry is that IM4 doesn't have a "safe" designated fixed location to dump its reflected beam when misaligned -- there's no "parking dump" like there is for PRM. So -- this an aLOG to indicate the times of high power with IM4 misaligned and what little info we have about the physical position.

I say "what little information about the position we have" because IM4, which is a HAUX suspension -- while IM4 has recently had its OSEM sensor PD sat amp upgraded, we have not measured or installed an absolute calibration for the sensors with an ISI injection. We know from other suspensions, that OSEM PDs can have factors of 2x to 3x errors between the "generic calibration based on electronics and [likely ancient] open light current measurement" and the modern absolute calibration from the ISI GS13s.

There *is* a calibration of the IM4 alignment sliders -- installed in Apr 2024 (LHO:77211). 
However, that calibration was based on the OSEM sensor PDs. 
So we have to take the fidelity of this calibration with a huge grain of salt a la the above distrust in OSEM PD calibration.

So -- IM4 had the following alignment offsets requested of its sliders: 
              OFFSET       OUT16
             ["urad"]    [EB-DAC ct]
    P        +114.539     +1248.53
    Y        +111.103      +625.387

and its *misalignment* offsets -- which are not calibrated in the front-end, but I've calibrated them using the (P,Y) = (10.9005 , 5.6289) [EB-DAC ct / "urad"] calibration from LHO:77211 here: 
              OFFSET       OUT16
             ["urad"]   [EB-DAC ct]
    P         +50.915      +555.0
    Y         +98.598      +555.0

So, misaligned, that give a total requested displacement of  
              OFFSET       OUT16
             ["urad"]   [EB-DAC ct]
    P         165.454     1803.532
    Y         209.701     1180.388

IM4 was misaligned, with PRM aligned and PR2 misaligned, and 60W into the IMC from 2025-10-28 16:08 UTC to 2025-10-28 17:06 UTC. 

After 17:06 UTC, the IMC power remained at 60W, but I aligned IM4 and PR2 and misaligned PRM. (The normal "IFO DOWN" configuration).
(So yes, we didn't turn the IMC power down before we went from misaligned to aligned, either.)

Trying to narrow down why TMS x is involved in lock losses we have replaced the TMS coil driver that works on F1,2,3 and LF.  Chassis S1102670 was replaced with S1102666.  The operator returned the system to damping.  This is a wait and see test.

We're assembling the first unit that incooporates all upgrades including the QPD tilt and here are minor problems we've stumbled upon. (No ISS array unit with an upgrade to tilt the QPD (E1400231) has been assembled before as far as I see and nobody seems to have cared to update all drawings.)

First picture is an example of the QPD before upgrade. QPD assembly (D1400139) and the cable connector assembly (D1300222) are mounted on the QPD platform by the QPD clamp plate (D1300963-v1, an older version) and a pair of split QPD connector clamps (d1300220). Two pieces of kapton insulation sheets are protecting the QPD assy from getting short-circuited to the platform.

After the upgrade, the QPD assy sits on top of a tilt washer (D1400146, called beveled C-bore washer) that tilts the QPD by 1.41deg in a plane that divides YAW and PIT plane by 45 degrees (2nd picture). The bottom kapton will go between the washer and the QPD platform plate.

Problem 1: Insulation between the QPD clamp and the QPD pins is a bit sketchy.

Titled QPD means that the bottom of the QPD assy is shifted significantly in YAW and PIT. A new asymmetric QPD clamp plate with tilted seating for the screws  (D1300963-v2) has been manufactured to accommodate that. But we have no record of updated kapton insulators, so the center of the clamp bore doesn't agree with the kapton (3rd picture, note that the QPD rotation is incorrect in this picture, which had to be fixed when connecting the cable). Since the tilt washer is not captured by anything (it's just sandwiched between the clamp and the platform plate), it's not impossible to shift the QPD assy such that some of the QPD pins will be grounded to the clamp and thus to the QPD platform plate.

You must check that there's no electrical connection between the QPD assy and the platform each time you adjust the QPD position in the lab.

Problem 2: New QPD connector clamp posts are too long, old ones are too short.

Old posts for the QPD connector are 13/16" long, which is too short for the upgrade because of the tilt washer, see 4th picture where things are in a strange balance. It seems as if it's working OK, but you can wiggle the post a bit so the post slides laterally relative to the clamp and/or the platform, it settles to a different angle and suddnly things become loose. To avoid that, you tighten the screws so hard that they start bending (which may be already starting to happen in this picture).

Also, because the clamp positions are 45 degrees away from the direction of tilt, one clamp goes higher than the other.

To address these, somebody procured 1" and 15/16" posts years ago, but they're just too tall to the point where the clamps are loose. If anything, what we need are probably something like 27/32" and 7/8" (maybe 7/8" works for both).

We ended up using older 13/16" posts, but added washers. Two thin washers for the shorter clamp, two thin plus one thick for the taller one (5th picture). This works OK. Shorter screw is the original, longer screw was too long but it works.

Problem 3: It's easy to set the rotation of the QPD wrong.

When retrofitting the tilt washer and the newer QPD clamp plate, you must do the following.

1. Completely loosen the connector clamps and the QPD clamp to remove the QPD/connector assy as one unit.
2. Put the tilt washer on top of the kapton insulation sheet at the bottom. The notch mark on the washer must be pointing the 45deg edge of the platform plate (D1300719-v2), see the 6th picture.
3. Separate the cable connector from the QPD to free the now-obsolete QPD clamp (-v1) that is captured between the QPD and the connector. I inserted a razor blade between the connector and the QPD assy and pried.
4. Put the assymmetric QPD clamp (-v2) on the top kapton insulation, paying attention to the direction of the new clamp using the 3rd picture as the reference.
5. Make sure that the rotation of the QPD assy is the same as before because the pins of the QPD are not symmetric. There's no physical mark on the QPD assy itself.
   1. If you're unsure, rotate the QPD assy such that the QPD pins will go to the right sockets on the connector using picture 7. Remember that QPD surface faces the platform down and the drawing of the connector is viewed from the top.
   2. After checking it several times, tighten the QPD clamp.
   3. Put the connector on. Again use picture 7 to put it on at the correct angle.
   4. After checking it several times, tighten the connector clamps.

I screwed up and put the QPD on the connector at a wrong angle. It's easy to catch the error because no quadrant responds to the laser, but it's better not to make a mistake in the first place. It will help if the QPD assy barrel is marked at the cathode-anode1 corner.

It seems that D1300222 and D1101059 must be updated. Systems people please have a look.

D1300222: A tilt washer (D1400146), a new QPD clamp (D1300963-v2) and two sheets of kapton insulation are missing. Spacers are longer than 13/16".

D1101059: Explicitly state that part #28 (D1300963, QPD clamp) must be D1300963-v2.

To investigate the 70Hz feature in HAM1 chamber, which Jim reported in his alog (LHO 84638) I started looking into the structural resonances of the periscope which is installed in HAM1 (see two pictures which TJ sent me, was taken by Corey here - view01, view02) .

Betsy, handed me a periscope (similar but not exactly the same) for investigation purpose, which is now setup in staging building. I attached an accelerometer to the top of the periscope and connected it to the front end of the B&K setup for hammer impact measurements - see picture of the experimental setup here. 

At first I used two dog clamps to secure the periscope. The results of the two dog clamp B&K measurement is shown in this plot (data from 0.125 to 200Hz)) - one can see a 39Hz feature in the Z hit direction. See zoomed-in (30-100Hz) figure here.

Next, I attached a third dog clamp, just like in HAM1 chamber and took a second round of measurements (especially for Z direction impact). 

This plot compares the two vs three dog clamps scenario on the periscope and one can see that the resonance mode has been pushed up from 39Hz to 48Hz. 

Morning (JennieW, Rahul, Keita)

We used the PRX flashes to align the POP path.

POP periscope location is good but the drawing is not.

The POP periscope position, which was set yesterday by Camilla and others, was right. That means that the drawing on D1000313-v19 is wrong. The periscope in reality is about an inch toward -Y direction relative to D1000313-v19. See the first picture, which was shot with a cellphone inserted under the top periscope mirror and looking straight down the bottom mirror. This means that the dichroic (M12) needed to be shifted by the same amount too.

Since the distance betwen the IFO and the lens for POP WFS doesn't matter that much, everything downstream (i.e. 90:10, PM1 tip-tilt, a lens, 50:50 and POP LSC as well as POP WFS) will be installed using the drawing.

We mainly rotated the periscope mirror clamps around the post for rough alignment, but we might have changed the mirror height by a millimeter or two in the process. 

PM1, which is calld that because it's the 1st (and the last) suspended Mirror for POP, is somehow called RM3 in D1000313. Systems please fix it.

Set the IR beam spot height/position on the periscope as well as the dichroic

The IR beam is supposed to be about 6mm or 1/4" lower than the center line of both of the periscope mirrors as well as the dichroic. This is because the green ALS beams are supposed to be ~13mm higher than IR. See L1200282 “CPy-X, CPx-Y” case on Table 1.

Top Periscope Mirror

It was almost impossible to see how much the beam is lower than the center of the top and bottom periscope mirror. Using the IR viewer card, I and Jennie agreed that the beam is lower than the center, but we could not quantitatively say how much especially on the top. We'll leave it as is, and if the green beam from the end station is too high we will have to use pico because we periscope is already as high as possible.

Bottom peri mirror

If everything is as intended, the bottom periscope mirror is 4" high from the ISI surface and the POP beam is 1/4" lower than that, therefore the POP beam is (1-0.25*sqrt(2)) = 0.646" = 16.4mm away from the bottom edge of the mirror.

Using a ruler in chamber (and measuring the dimensions of a spare Siskiyou mount using caliper), the height of the bottom periscope mirror center was calculated to be ~4.07" from the ISI surface, i.e. 0.7" too high. This means that, when the beam height measured from the ISI is as designed (i.e. 4"-1/4"), the POP beam is (1-(0.25+0.07)*sqrt(2))=0.547"=13.9mm away from the bottom edge of the mirror.

If you have difficulty understanding this, see the cartoon.

POP beam radius is ~2mm, so 13.9mm (or even 13mm for that matter) looks like a safe distance to me. I don't see the need to readjust the height of the bottom periscope mirror.

I adjusted the top periscope mirror to set the beam height right after the bottom peri mirror to be ~3.75" using the IR viewer card and a ruler.

Dichroic

I placed the dichroic about 1" into -Y direction relative to the drawing (because I had to), and used the bottom periscope mirror to set the beam height close to the dichroic to be ~3.75".

Then I used the dichroic to steer the beam into the direction of the location for PM1 without placing 90:10.

For the beam profile measurement, the downstream alignment is done without 90:10. Later we will install 90:10 back in place and do the final alignment.

Fil Marc Daniel

We noticed that the photodiode pins of the in-air cable that connects to RM1 and RM2 were flipped. This will flip cathode and anode which will only matter if there is a bias applied.

Going thru the schematics it seems that with 1:1 wiring the PD anode and cathode are flipped compared to what is shown in Sat Amp D080276. I assume somebody noticed this and flipped the corresponding pins of the in-air cable to correct for it back in 2013.  The polarity of the PD doesn't really matter, if there is no bias. We checked the RM sat amps and they have no bias.

If the Sat Amp PDs are connected as shown om D080276, the OSEM values will be negative. Indeed, the RMs had negative OSEM values as expected. However, all ZMs have positive values, since nobody bothered to flip the pins. We propose to no longer flip the PD pins for the RMs and work with positive OSEM values in the future.

J. Kissel scribing for S. Koehlenbeck, J. Freed, and R. Short
ECR E2400083
IIET 30642
WP 12453

Just writing a separate explicit aLOG for this for ease of reference in the future.

Before, during and after the SPI install we measured power along respective paths,
(1) The p-pol in-coming power into the whole ALS / SQZ / SPI pick-off path,
(2) The "ALS COMM" path: p-pol power in transmission of the ALS-PBS01 with the newly modified ALS-HWP2 position to get more power total power in the paths (3) and (4),
(3) The "SPI pick-off" path: The ~s-pol power in reflection of SPI-BS1,
(4) The "ALS/SQZ Fiber Distribution" path: ~s-pol power in transmission of SPI-BS1,
(see discussion in LHO:83978 as to why we're not so confident the reflection from ALS-PBS01 is entirely s-pol, which is why I say "~s-pol" here.)

The BEFORE vs. AFTER power in these paths is as follows:
  Path   Measured Between        Raw Power [mW]  PMC TRANS [W]     Date/Time Measured      Scaled Power [mW]  Fractional Power [%]
  (1)    ALS-L1 and ALS-HWP2         2060          103.2           2025-04-15 21:39 UTC       2095.9               ---

      % BEFORE
  (2)    ALS-M2 and ALS-L2           1970          102.8           2025-04-15 22:17 UTC       2012.2               96%
  (4)    ALS-M9 and ALS-FC2          48.7          103.0           2025-04-15 21:48 UTC         49.646              2%

      % AFTER
  (2)    ALS-M2 and ALS-L2           1790          103.3           2025-04-17 21:13 UTC       1817.7               87%
  (3)    SPI-L1 and SPI-L2            186          103.5           2025-04-16 22:43 UTC        188.7                9%
  (4)    ALS-M9 and ALS-FC2            50.5        103.5           2025-04-16 22:43 UTC         51.232              2%
where I've scaled all the raw power measurements by the rough nominal PMC TRANS power during recent observing times, 105 [W], i.e. 
(Scaled Power [mW]) = (Raw power) * (105 [W] / PMC TRANS [W])
and
(Fractional Power [%]) = 100 * {Scaled Power [mW]; paths (2)-(4)} / {Scaled Power [mW]; path 1}


As Ryan mentions in LHO:83989, for the purposes of safe long term storage, after all was said and done, we rotated SPI-HWP1 such that only 20 [mW] would go toward the SPI-FC1 fiber collimator, and it's dumped upstream just after SPI-L1. These AFTER power levels are what we anticipate running the rest of O4 in, with the SPI pick-off path safely out of commission.

2W Measurements
Head:    Ophir    10A-V2-SH SN122042 
Readout: Ophir    20C-SH    SN171175
Accuracy: +/-3%

200 mW Measurements:
Head:    Thorlabs S401C
Readout: Thorlabs PM100-D
Accuracy: +/- 7%

The attached picture summarizes all this info. The picture was take midday 2025-04-17, so you see the Ophir power meter in the middle of the ALS COMM 

S. Koehlenbeck, J. Freed, R. Short, J. Kissel

The mode matching of the PSL pick-off beam to the SPI fiber collimator has been implemented using two lenses. The target beam has a mode radius of 550 µm at a position 63.5 cm downstream from the SPI beamsplitter (SPI-BS).

The lens configuration that produced the closest match to the target mode used:

• L1: Focal length = 100 mm

• L2: Focal length = 60 mm

Attached is a beam profile fit performed using JaMMT on data acquired with a WinCamD of the beam after SPI-L2. The measured beam radii at various distances from the SPI-BS are as follows:

Both lenses are oriented such that their planar sides face the small beam waist between the two lenses. The arrows on the lens mounts point toward the convex surfaces.

The power transmission through the fiber has been measured to be 83 %.

J. Kissel scribing for S. Koehlenbeck, J. Oberling, R. Short, J. Freed
ECR E2400083
IIET 30642
WP 12453

Another quick summary aLOG at the end of the day, with more details to come:
- With the power in the ALS/SQZ pick-off path to 10 [mW] for beam profiling,
- Installed a two lens system to handle the unexpectedly different beam profile of the ALS/SQZ pick-off path
- Remeasured the resulting mode after the two lens system, and we're happy enough. We're gunna call them SPI-L1 and SPI-L2.
- Installed steering mirrors SPI-M1 and SPI-M2.
- Rotated ALS-HWP2 to increase the s-pol light in the ALS/SQZ/SPI path to return the power transmitted through SPI-BS1 going to the ALS/SQZ fiber collimator back to 50.5 [mW]. This set the SPI path to 186 [mW] with the PMC TRANS measured at 103.5 [W]. The ALS_EXTERNAL PD in transmission of ALS-M9 measured 31 [mW] ***. 
- Installed SPI-HWP1 and SPI-PBS01
- Measured the power at each port of SPI-PBS01, with the intent to optimize the SPI-HWP1 position to yield maximum p-pol transmission through SPI-PBS01.

*** We expect this is lower than the goal of ~45 [mW] (from LHO:83927) because we've not yet re-aligned the ALS/SQZ fiber collimator path after the install of the SPI-BS1, which translates the beam a bit due to the thickness of the beam splitter. We intend to get back to this once we're happy with the SPI path.

J. Kissel scribing for S. Koehlenbeck, R. Short, J. Oberling, and J. Freed
ECR E2400083
IIET 30642
WP 12453

During yesterday's initial work installing the SPI pick-off path (LHO:83933), the first optic placed was SPI-BS1, the 80R/20T power beam-splitter that reflects most of the s-pol light towards the new SPI path. The pick-off is to eventually be sent into a SuK fiber collimator (60FC-SF-4-A6.2S-03), so we wanted to validate the beam profile / mode shape of this reflected beam.


The without changing any power in the ALS/SQZ/SPI pick-off path, the power now reflected from newly installed SPI-BS1 measured ~40 [mW] (see LHO:83946). This is too much for the WinCam beam profiler, so they used ALS-HWP2 to rotate the polarization going into ALS-PBS01, and thus reduced the reflected s-pol light in this ALS/SQZ/SPI pick-off path to ~10 [mW]. That necessarily means there's a little more of the ~2 [W] p-pol light transmitted and going toward the HAM1 light pipe, so they placed a temporary beam dump after ALS-M2 so as to not have to think about it.

The they set up a WinCam head on a rail and gathered the beam profile. With the WinCam analysis software on a computer stuck in the PSL, they simply gathered the profile information which I report here: 
# Distance[cm]	Radius[um]   Radius[um]
                   X             Y
    0.0           680.5         717
    17.78         465           504
    25.4          389           428.5
    30.48         346.5         368
    38.1          281.5         300.5

where "X" is parallel to the table, and "Y" is orthogonal to the table. The "0.0" position in this measurement is the "front" of the rail (the right most position as pictured in the attachment), which is Column 159 of the PSL grid. SPI-BS1 has the center of its reflective surface is set in +/- X position in Column 149 (within the existing ALS-PBS01 to ALS-M9 beam line). It's +/- Y position is set to create a reflected beam line along Row 30 of the grid, and the WinCam head and rail are centered in +/- Y on that Row to capture that beam.

Using this profile measurement, we find it to be quite different than expected from when this path was installed circa 2019 (see e.g. LHO:52381, LHO:52292, LHO:51610). Jason shared his mode matching solution from LHO:52292 with us prior to this week, and I've posted it as a comment to that aLOG, see LHO:83957.

We think we can trace the issue down to an error in the as-build drawing for the PSL:
- the whole beam path running in the +/-X direction from ALS-M1 to ALS-M2 is diagrammed to be on row 23 -- however, we find in reality, the path lies on row 25. That's 2 inches more between the (unlabeld) pick-off beam splitter just prior to ALS-M1 and ALS-M1 itself. Easily enough to distort a mode matching simulation.
- Jason confirms that he used the *drawing* to design the lens telescope for this ALS/SQZ fiber distribution pick-off path.

More on this as we work through a lens solution for the SPI path.

As of this entry, we elect to NOT create a new solution for the whole ALS/SQZ fiber distribution pick-off i.e. we *won't* adjust ALS-L1 or ALS-L5 in order to fix the true problem. But, we report what we found in the event that a case is better made to help mode matching and aligning into the ALS/SQZ fiber distribution pick-off easier -- as we have verbal confirmation that it was quite a pain.
For the record the fiber collimator used in the ALS/SQZ distribution pick-off is a Thor Labs F220 APC-1064.

J. Kissel, S. Koehlenbeck, J. Oberling, R. Short, J. Freed
ECR E2400083
IIET 30642
WP 12453

After this morning's kerfuffle / belated power-outage recovery with the PSL HVAC system was resolved, Sina, Ryan, and Josh began the procedure we're walking thru outlined in Section 1 of T2500024. We're keeping running notes on the fly at the bottom of the google-doc for now.

In summary here, with more details to come, we got as far as 
- Clearing out some old IO equipment that unused and in the way of the SPI pick-off path
- Measuring the power around ALS-PBS01
- Installing the new ALS/SPI 80R/20T beam splitter
- Measuring the beam profile along the future SPI path, in reflection of this 80R/20T beam splitter.

J. Kissel, B. Lantz, E. Bonilla, D. Barker
ECR E2400405 
IIET 32526
WP 12459

Using a linear combination of LHO:83724, the google slides in G2402303, and talking to Brian/Edgard who arrived for their week long visit today -- we installed the OSEM estimator infrastructure today on PR3 *and* SR3. 

We've only filled in enough infrastructure to ensure that it's function is entirely OFF.
Hopefully we'll get further this week.

The new channels have been initialized in the safe.snap for PR3 and SR3. 
    /opt/rtcds/userapps/release/sus/h1/burtfiles/
        h1suspr3_down.snap
        h1sussr3_safe.snap

We made edits to Brian / Edgard's work on common library parts,
    /opt/rtcds/userapps/release/sus/common/models
        HLTS_MASTER_W_EST.mdl
        SIXOSEM_T_STAGE_MASTER_W_EST.mdl
medm screens
    /opt/rtcds/userapps/release/sus/common/medm/hxts
        SUS_CUST_HLTS_OVERVIEW_W_EST.adl
    /opt/rtcds/userapps/release/sus/common/medm/estim/
        ESTIMATOR_OVERVIEW.adl
        CONTROL_6.adl
(see attached notes for details).

And then I made edits to
    /opt/rtcds/userapps/release/isi/h1/models/
        h1isiham2.mdl
        h1isiham5.mdl
to add PCIE Dolphin IPC senders to send out the calibrated ISI HAM ST1 GS13s that are pre-projected into the PR3 and SR3 suspension point euler basis, and then modified
    /opt/rtcds/userapps/release/sus/h1/models/
        h1suspr3.mdl
        h1sussr3.mdl
top level models to receive those IPC, and pipe them in to top of the new main libary part, the HLTS_MASTER_W_EST.mdl

Finally, after Dave installed the model changes and restarted the ISIs and HLTSs, we edited the sitemap
    /opt/rtcds/userapps/release/cds/h1/medm/
        SITEMAP.adl
 to use the HLTS_OVERVIEW_W_EST.adl.

Everything file I mention above has been committed to its respective location in the svn.
Screenshots of stuff will come in the comments.

J. Oberling, R. Crouch

Today we took pre-deinstall measurements of the position of the optical table surface of the WHAM1 passive stack.  The plan was to use the FARO to measure the coordinates of several bolt holes, using a threaded nest that locates the Spherically Mounted Retroreflector (SMR) precisely over the bolt hole, on both the +Y and -Y side of the chamber.  This, unfortunately, did not happen in full due to the untimely death of the FARO's climate sensor (or the FARO's ability to read the climate sensor, we're hoping for the former).  The FARO cannot function without this sensor as it relies on accurate measurements of the air temperature, relative humidity, and air pressure to feed into a model of the refractive index of air, which it needs to accurately calculate the SMR distance from the FARO.  We did manage to get a few points measured before the sensor died.  I've reached out to FARO tech support about getting a new climate sensor and should hear back from them tomorrow (they usually replay in 1 business day).

Summary

We were able to get measurements of 3 bolt holes, all in the furthest -Y line of bolt holes, and an old IAS monument from aLIGO install before the FARO's climate sensor died.  The results are listed below under the Results heading.  The most interesting thing here is there appears to be an error in WHAM1 placement in the x-axis, as the bolt holes we measured are all ~37.25 mm too far in the -X direction from nominal.  We also set a scale on the wall across from the -Y door of the WHAM1 chamber that is registered to the current elevation of the optical table; placing an autolevel so it sights 150.0 mm on this scale (sighting the side of the scale with the 0.5 mm tick marks) places that autolevel 150.0 mm above the surface of the passive stack's optical table.

Details

We started on the -Y side of the WHAM1 chamber.  The FARO was set with a good view of its alignment monuments and the passive stack's optical table.  We ran through the startup checks and calibrations without much issue (we did see a return of the odd 'ADM Checks Failing' error, which had been absent for about 1 month, but it immediately went away and didn't come back when we performed a Go Home operation).  FARO monuments F-CS026 through F-CS035, inclusive, were used to align the FARO to the LHO LVEA local coordinate system; the 2 standard deviation device position uncertainty after this alignment was 0.016 mm (PolyWorks does 100 Monte Carlo simulations of the device position).  This complete, we started measuring.

First, as a quick test of the alignment we took a look at old IAS monument LV24.  This monument was used to align the WHAM2 ISI during aLIGO install, and its nominal X,Y coordinates are [-20122.0, -3050.7] mm (there is no z-axis coordinate as we were not setting these in Z back then, a separate set of wall marks was used for z-axis alignment).  The results are shown in the 1st attached picture; again, ignore the z-axis results as I had to enter something for the nominal or PolyWorks wouldn't accept the entry, so I rounded to the closest whole number (this isn't even the surface of the monument, it's the point 2" above it where the SMR was, due to use of the Hubbs Center Punch Nest (which has a 2" vertical offset when using a 1.5" SMR)).  Knowing how we had to set these older monuments, since I'm one of the people that set them, I'm not entirely surprised by the X and Y deviations.  The monuments we set for aLIGO install (the LV monuments) were placed w.r.t. a set of monuments used to align iLIGO, which themselves were placed w.r.t. the monuments used to install the vacuum equipment during facility construction (the PSI monuments), which themselves were placed w.r.t. the BTVE monuments which define the interface between the arm beam tubes and the LVEA vacuum equipment, which we then found errors in their coordinates during our alignment of the FARO during the O4a/b commisioning break in 2024.  Not at all surprised that errors could have stacked up without notice over all of those monuments set off of monuments set off of monuments set off of...  Also, take note of the x-axis coordinate of this monument, this will be important later.

We then set about taking measurements of the passive stack optical table.  To map the bolt holes we measured we used an XY cartesian basis, assuming the bolt hole in the -X/-Y corner was the origin.  We then proceeded to increment the number by the bolt hole (not distance), following the same XY axis layout used for the IFO.  Using this scheme the bolt holes for the table corners were marked as:

• -X/-Y: (0,0)
• -X/+Y: (0,32)
• +X/-Y: (36,0)
• +X/+Y: (36,32)

We were able to get measurements for bolt holes (0,0), (14,0), and (25,0).  We were in the process of measuring bolt hole (36,0) (the +X/-Y corner bolt hole) when the FARO's climate sensor died.

To get the coordinates for the bolt holes I used the .EASM file for WHAM1 with the passive stack configuration located at D0901821-v4.  From the assembly, using eDrawings, I was able to get coordinates w.r.t. the chamber origin for the bolt holes we measured.  Those were then added to the coordinates for the WHAM1 chamber, in the LVEA local coordinate system, to get nominal coordinates for the bolt holes.  I also had to add 25.4 mm to the z-axis coordinates to account for the 1" offset of the nest we were using for the SMR; the center of the SMR sits 1" above the point being measured, so I needed to manually add that offset to the nominal z-axis coordinate of the bolt hole.  For reference, according to D0901821 the global coordinates for WHAM1 are [-22692.0, 0.0, 0.0] mm; when converted to the LVEA local coordinate system (removing the 619.5 µrad downward tilt of the X-arm) this becomes [-22692.0, 0.0, +14.1].  The measurement results are shown in the 2nd attached picture.  Notice those x-axis deviations?  Remember the measurement we made of LV24?  Clearly the FARO alignment is not 37 mm off, as the measurement of LV24 showed, so something is definitely up with the x-axis coordinate of the WHAM1 chamber (error in chamber placement?  aLIGO WHAM1 is the iLIGO WHAM2 chamber, moved from its old location next to WHAM3).

Results

We can do some analysis of the numbers we have, although limited since we only have 3 points in a line.  This really only applies to the furthest -Y line of bolt holes on the table, since we weren't able to get measurements of the +Y side to get a more full picture of where the table is sitting, but it's something.  Position tolerances at install in 2012 were +/-3.0 mm in all axes.

• X-axis position: Not much we can do here without knowing what the actual x-axis coordinate of WHAM1 is.  It clearly isn't where the SYS drawings say it should be.
• Y-axis position: ~0.41 mm +Y from nominal
• Z-axis position: ~0.76 mm +Z from nominal
• Pitch: ~99 µrad down
• Yaw: ~83 µrad CCW

I do want to note that D0901821-v4 claims the table surface should be -187.8 mm in LVEA local coordinates (-201.9 mm in global), but this is not the number we used when installing the passive stack in 2012.  In 2012 we used -185.9 mm local (-200.0 mm global), as can be seen in D0901821-v2.  To compare our measurements to the install numbers I changed the nominal z-axis coordinate to match that of our install target (-185.9 + 25.4 mm SMR offset = -160.5 mm) and the results are shown in the final attached picture.

Wall Scale Registered to Current Table Surface Elevation

To finish, we set a scale on the -Y wall directly Crane East of the WHAM1 chamber and registered it to the current elevation of the passive stack's optical table.  To do this we used a scale provided by Jim (the scale was in inches, with 0.01" tick marks) and an autolevel.  We set the autolevel at a fixed elevation on the -Y side of the chamber.  The scale was then placed at each corner of the optical table, starting with the -X/+Y corner, and the autolevel was used to sight the scale; only the scale was moved, the autolevel was fixed (rotated only to follow the scale, but not moved otherwise).  We then averaged the 4 scale readings to get the table elevation, set the autolevel to this reading with the scale back at our starting point (we actually didn't have to move it, thankfully), and then set a scale on the wall using the autolevel.  The 4 scale readings:

• -X/-Y: 5.89"
• -X/+Y: 5.90"
• +X/-Y: 5.90"
• +X/+Y: 5.91"

The average of the 4 readings is 5.9", and since the autolevel was already sighting 5.9" on our starting point at the -X/+Y corner we left it there.  This may seem high, but we had to have the autolevel high enough that we could see over the various components mounted to the table surface.  We then turned the autolevel and set a scale on the wall.  This scale was in mm (since that's what we had), but this worked out OK.  5.9" is ~149.9 mm (149.86 mm to be exact), so we set the wall scale so it read ~149.9 mm when sighted through the autolevel.  So a 150.0 mm reading on this scale (sighting the side with the 0.5 mm tick marks) is ~150.0 mm above the current position of the passive stack's optical table.

This closes LHO WP 12442.

Jeff asked me to plot a comparison for SR3 M1 between all degrees of freedom comparing it in vacuum versus in air. I've plotted the last two measurements taken for SR3 from last August at the end of the OFI vent. One measurement was taken in air, and the other was taken in vacuum The pressure for the in vacuum measurement wasn't all the way down to our nominal, but as Jeff said in his alog at the time when we were running these measurements: "most of the molecules are out of the chamber that would contribute to buoyancy, so the SUS are at the position they will be in observing-level vacuum" (79513).

HAM1 Before Photos:  (HAM1 chamber open just under 90min for this activity)

This morning before the deinstall activities begin, took the opportunity to photo document the HAM1 optical layout.  Keita requested I take photos to record the layout wrt to the iLIGO bolt pattern, because rough alignment of optical components on the new SEI ISI for HAM1 will be done utilizing the bolt patterns of the Optics Tables; so I took a few more photos than normal (top view and angled with a focus on the REFL path).  Took large photos with the Canon 60D DSLR camera as well as my camera phone.  

The photos are being populated in this Google Drive folder:  https://drive.google.com/drive/folders/1yDKp7aByA_TYJ12c8j8BnZM_pd1Q2DBZ?usp=sharing

Naming each photo referencing an updated layout Camilla Compton made which labels all beam dumps, but I also had to use an older layout to preserve naming since the layout on HAM1 currently looks like D1000313v16 (which is also referenced for naming the photos).

The above folder has the Canon photos, and I'll be adding the camera phone images next.

Contamination Control Notes:

• Dust Monitor on the West side of HAM1 had 0.0 counts (0.3+0.5um) BEFORE the work started and AFTER the work was done the counts were under 100.0 counts (0.3+0.5um).
• Travis touched up the Purge Air a little before the covers were rolled down.
• The Contamination Control wafer roughly in the middle of the table was pulled out and Betsy encapsulated in a container.

J. Kissel, R. McCarthy, M. Pirello, O. Patane, D. Barker, B. Weaver
2025-04-06 Power outage: LHO:83753

Among the things that did not recover nicely from the 2025-04-06 power outage was the +18V DC power supply to the SUS ITMY / ITMX / BS rack, SUS-C5. The power supply lives in VDC-C1 U23-U21 (Left-Hand Side if staring at the rack from the front); see D2300167. More details to come, but we replaced both +/-18V power supplies and SUS ITMY PUM OSEMs satamp did not survive the powerup, so we replaced that too.

Took out 
    +18V Power Supply S1300278
    -18V Power Supply S1300295
    ITMY PUM SatAmp S1100122

Replaced with
    +18V Power Supply S1201919
    -18V Power Supply S1201915
    ITMY PUM SatAmp S1000227

J. Kissel, M. Pirello
2025-04-06 Power outage: LHO:83753

Among the things that did not recover nicely from the 2025-04-06 power outage was the Timing Comparator D1001370 that lives in ISC-C2 U40 (see component C261 on pg 3 of D1900511-v9). The symptom was that its time-synchronizing FPGA was caught in a bad state, and the timing fanout in the CER Beckhoff status for the comparator was reporting that H1:SYS-TIMING_C_FO_A_PORT_13_NODE_UPLINKUP was in error (a channel value of zero instead of one). 

We didn't know any of this at the start of the investigation.
At the time of investigation start, we only new of an error by following through the automatically generated "SYS" screens (see attached guide),
   SITEMAP > SYS > Timing > Corner A Button [which had a red status light] 
   > TIMING C_FO_A screen Port 13, dynamically marked as a "C" for comparator [whose number was red, and the status light was red] 
   > Hitting the "C" opens the subscreen for TIMING C_FO_A NODE 13, which shows that red "Uplink Down" message in the middle right
The screenshot shows the NODE 13 screen both in the "now" fixed green version state, and a time-machined "broken" version.

Going out to the CER, we found that status light for Digital Port 13 == Analog Port 14 on the timing fanout (D080534; ISC-C3 U11) was blinking. 
Marc tried moving the comms cable to analog port 16, because "sometimes these things have bad ports." That didn't work, so we moved it back to analog port 14.

That port's comms fiber cable was not labeled, so we followed it physical to find its connection to the SQZ timing comparator (again in ISC-C2 U40, thankfully "right next door"), to find it's "up" status light also blinking.
Marc suggested that the comparators may lose sync, so we power cycled it. This chassis doesn't have a power switch, so we simply disconnected and reconnected its +/-18 V power cable.
After waiting ~2 minutes, all status lights turned green.

#FIXEDIT