This is a follow up on 90181.  

Confirming that we understand the profiler data for nominal psams setting, and that the mode has changed

Tony, Ryan Short and I went back onto the floor the week of May 11th.  We followed the alignment procedure for the M2MS profiler extension kit, which did result in different results.  Because we have been confused about how to interpret the results from M2Ms, especially the "Original Waist position" Tony, Ryan and I took a scanning slit profiler out to the table and measured beam diameters at similar locations to where Leo, Camilla and Jennie measured in 85917.  The scanning slit measurements are shown as dots in the attached comparison, each of them is fit by the finesse BeamParamFit shown by the solid line of the same color.  Leo also did a fit to the 2025 data as reported in 86365, the finesse fits have overlaps of 98.7% and 97.5% with Leo's fits.  

The M2Ms profiler reports Rayleigh length, and also "Original Waist position".  From my conversations with tech support I believe that the "Original Waist position" is a distance from the reference plane as shown in this diagram, in mm (they say they will update the software to reflect that it is mm not um), where a positive number means that the waist is on the side of the reference plane closer to the source.  From 90181 I believe that the reference plane is 5.678 meters from ZM5, and all these beams are converging as they leave ZM5, so the real part of q should be negative.  So the real part of the q parameter is -1*(5.678-"Original beam waist position"*1e-3.  )  The dashed lines in the comparison are qs from the M2Ms software, for the M2Ms overlaps with the scanning slit fit by 98.7% (vertical) and 98.9% (horizontal).  

Although the different fitting and measurement types don't exactly agree with each other, the mode is clearly different after the OPO swap, the overlap of the beam width measurements now vs Summer 2025 is 87% for vertical and 85% for horizontal.   In summer 2025 the overlap of the horiztonal mode with the verical mode was 98%, now it is 99.5%.  

Sw plot for various psams settingsThis plot shows the measured beam parameters, both from this recent data set and from Leo's fits in  86365,propagated to SRM, with contours showing constant mode matching to the OMC for reference.  This can be compared to plots that Evan Hall has made in G2600435.  In O4, this confirms that we our choice for a nominal psams setting did bring us as close to good mode matching to the OMC with the psams that we had, but that we couldn't access the best mode matching parts of the space.  This also confirms that the astimgatism of the squeezer beam would have limited our mode matching if we had been able to move the psams to bring the beam closer to the OMC mode.  

Guess and check for psams actuation strength

Using this May 2026 set of q measurements, I've attempted to check the actuation strength of ZM4+ ZM5 psams.  Since we don't have a measurement of the q before ZM4, we don't actually have information in this dataset about the curvature of ZM4 (we can't distinguish between the curvature of the beam incident on ZM4 with the curvature of ZM4). Alog 90218 summarizes what we expect for the ROC of the psams with 0V applied to the PZT based on the preload that was applied.  I've taken a set of guesses for the ROCs at nominal psams settings, and mD/V for each psams, and used the measured horizontal and vertical q for the nominal psams settings to propagate back to a q incident on ZM4.  Then I propagated that forward for each different psams voltage, to predict the qs and compare to the measured qs in the attached plot.  We have no information about the ZM4 ROC here, since we don't know the curvature of the beam incident on ZM4, so that parameter doesn't matter.  There is also a degeneracy between the nominal ZM5 ROC and the actuation strength of ZM4, they both change the spacing between the group of 5 measurements taken at different ZM4 voltages.  

We can find the nominal psams actuation strengths from E2100288,(we have ZM4 SN1 and ZM5 SN4 at H1), although those measurements were from before the pre-load was changed Camille tells me they should be about the same.  I cannot get a reasonable match to the measured data without reducing the actuation strength of ZM5 to about half of what it should be.  For ZM5 ROC, we can make an estimate based on 90186 and the nominal -0.58mD/V pzt reponse that the nominal ROC should be around 3meters, this doesn't seem to give us a good match to the measured q parameters.  

IM4 (and IM4 baffle) beam position

This is a belated alog from Tuesday.

Starting point: Same alignment for MC123, IM123 as last Friday, i.e. the IM4 baffle NOT centered nor unclipped.

Without touching IMC and IM1/2/3, we rotated IM4 to steer the beam close enough to the nominal beam position in front of PR2, and measured the beam position horizontally and vertically relative to the known screw hole in front of PR2 and PRM.

The distance between IM4-PRM beam line as of now relative to the nominal PRM-PR2 center line was calculated to be 3.9+-1.1mm in -Y direction and too low by 2.9+-1.1mm. See measurement_cartoon.jpg for the horizontal position case. Height is derived in the same way. Since the beam position in front of PR2 is not grossly off, and since IM4 is much, much closer to PRM than PR2, you can use these numbers as the spot position on PRM, too.

From IM4baffle_20260526.jpg, centering the beam on PRM will correct the height on IM4 baffle (HA12). Horizontally it will within a couple mm or so from the center.

What we should do

As we're running out of time, give up the idea to understand what happened to the alignment during the vent before closing HAM2. We should recenter things whenever possible (but only when the IFO REFL path and POP sled path are not disturbed to the point we clip or lose the beam).

For IMC, 

• Since MC3 beam spot is great but MC2 spot is off by 3.6mm in -Y direction, center the beam spot on MC2 (i.e. move it by 3.6mm in +Y direction using JM3) but don't move the beam spot on MC3.
• This is a scaled-down version of the yellow-orange trace in the plot ("Rotation around MC3" case in cartoon_IMC_alignment_to_unclip.png)  from alog 90295, causing about 220urad angle change for the beam coming out of MC3 and will shift the beam by 3*3.6/11~1mm on PRM in positive Y direction.
• This is done by:
  • Measure the beam spot of MC1 transmission in front of MC2. Rotate JM3 until the beam comes to the expected position.
  • Measure the beam spot on MC2 reflection in front of MC3. Rotate MC2 until the beam comes to the expected position.
  • Use MC3 to roughly make the 1 round-trip beam (MC3 reflection reflected by MC1) go on top of the input beam near MC1.
  • Use MC1 to roughly make the 1-round trip beam go on top of the input beam near MC2.
  • Only use MC3 and MC1 to refine.

For IMs,

following is the table of slider offsets as of now.

Even though the physical PIT angle of the optics relative to the local vertical axis is arbitrary, it seems that IM1 is bringing the beam down on IM2, IM2 is bringing down the beam further on IM3, and IM3 is bringing up the beam on IM4 and PRM. But IM2 is twise as efficient as IM3 for changing the beam position on PRM. Besides, the beam is already coming down from MC2 to MC3 (about 10mm height difference over 16m, or about 220urad) and I don't know if it makes sense to use IM2 to bring the beam further down. It's worth redistributing PIT as well as YAW offsets to relieve big offsets.

However, note that ultimately IM1-IM2 line defines the IFO REFL path when PRM retroreflects. (Even if you rotate IM2, as far as IM1-IM2 line doesn't change the IFO refl beam won't move.) I won't touch IM1 as moving the beam on e.g. IM2 even just a few mm using IM1 (i.e. a few mm over ~1.8m leverarm) will result in a much bigger change for REFL path in HAM1, potentially risking yet another clipping or maybe the loss of the REFL beam. IMC alignment noted above will change the IM1-IM2 line, but that's basically the angle change of ~3.6mm/16m (i.e. an order of magnitude smaller than when moving IM1 to steer the beam on IM2 in a meangful amplitude). That's small enough it's hard to imagine that the beam will be clipped by IFO refl baffle nor the downstream optics.

So,

• Don't touch IM1 as the lever arm for IM1 to anything in HAM2 is much shorter than MC2-MC2 length and it will affect the IFO refl path in a meaningful manner. Don't try to center the beam on IFI input baffle using IM1, it's not too bad (see this picture from alog 90295). It's not ideal but we can live with that, IFI aperture is 20mm and the IFI input baffle aperture is 16mm.
• Before starting to move IM2/3, make sure that PRM is retroreflecting. Adjust PRM if not.
• Look at IFO refl on IFO refl baffle. If it's clipped, something is wrong, come out of the chamber and talk to others before proceeding.
• If IFO refl baffle looks fine, confirm that the flashing is visible in HAM1 LSC and ISC sensors.
• Look at the beam spot on IFI output baffle, if possible at all. Depending on how it looks, we could try something like below.

 Of course this is assuming that the slider calibration is correct, so take this as a qualitative reference to get the sense of sign of angle changes. Anyway, when this is done, the DAC counts for IM2 and IM3 will be smaller while the beam height on PR2 will be fine. 

After doing the above,

If centering HA12 (IM4) baffle is important, relocate HA12. I'll ask Rodica.

Make sure that PRM retroreflects. Readjust if not. Check IFO REFL beam on IFO REFL baffle, LSC REFL and ASC REFL sensors. 

Recenter IM4_TRANCE by pico. 

Realign ISS array (simply because it's easier to do it in air than in vacuum).

Homework

Think about POP sled path. Is it conceivable that we'll somehow miss the beam there because we change the beam spot position on PRM?

FAMIS 63900

No major events of note this week.

J. Freed

Update from last time 90273:

I took phase noise (PN) measurements of the SPI RF chain yesterday and found that nothing drastically changed in performance from test stand set up to final set up DM_Install.png. And that Oscillator noise is not a noise limit for SPI DM_Install2.png (The shape changed is calculated by the same equation as 88457) Note that PN measurments can be limited by the reference frequency. As such, the plots of PN are plotting a maximum noise. The actual noise could be even less (see notes).

The main thing a phase noise set up needs is a reference signal with the same frequency as the RF signal being tested with good performance. An OCXO that is timing locked to LIGOs 1pps timing signal or a frequency generator that is locked to a 10MHz signal produced by that OCXO is required. Where to get this specific requirement in the LVEA? J. Kissel gave the idea to use the Frequency generator that produces the TCS 40.68MHz signal to be delivered to the TCS-R2 rack about 12ft away from SUS-R2. 

SPI_PN_layout.png Shows the layout of this set up. A 40.68MHz signal is produced in the MER TCS-M1 rack by a SRS SG382 function generator Screenshot2026-05-27at103451 AM.png. Where it is sent to the LVEA rack TCS-R1. The signal then is sent into an RF distributor Screenshot2026-05-27at103458 AM.png where it is split into signals for TCSx, TCSy, and a mon channel. TCSy is then sent to TCS-R2 Screenshot2026-05-27at103806 AM.png. I could then run a long cable to SUS-R2 from TCS-R2 Screenshot2026-05-27at103523 AM.png and by adjusting the frequency of the frequency generator so I could perform the PN test. Before switching the frequency on the SRS, I made sure to replace the wires in TCS-R1 going to TCSx and the mon channel with terminators and replace the wire going to TCSy in TCS-R2 with my own long cable. I then did the reverse order to put TCS back. (SPI_Install_PN_TestPlan.png is the plan I followed.)

Notes: 

The TCS SRS SG382 function generator N-Type Connector is burnt out. I cannot find a report on this but will add a comment if that changes

The SRS SG382 function generator has 2 ports, a BNC and a N-type. The BNC typically handles lower power and lower frequency while the N-type handles higher power and higher frequency. The 40.68MHz nominal signal can go through either port while the 80MHz I need for the PN test must go through the N-Type port. This means the PN measurements I took went through the burnt out N-type. 

I confirmed this by checking the power of the signal at sus R2, then by only changing the port, checked the power again. With the nominal 40.68MHz signal outputted at 13dBm from the TCS function generator BNC Port. I measured 11.2dBm at SUS-R2. By only swiching to the N-type port, I measured -18dBm. A ~30dBm drop. Technically I also switched out a cable from BNC/N-Type to N-type/N-type so I checked that too by using another N-Type/N-type and there was no change in power between cables. 

This did not seem to have a drastic effect on the PN measurements except for a slightly higher general noise floor and alot of noise at high frequency which SPI is insensitive to. This has no effect on the conclusion that Oscillator noise is not a noise limit for SPI.

After figuring out the damping issues for the BBSS yesterday (90341), we took some transfer functions to check for rubbing or anything else weird after all the alignment work that has been occurring.

These measurements were taken using BOSEMs, and have the correct DAC compensation value of gain(4096) in the COILOUTF filter bank.

Data
/ligo/svncommon/SusSVN/sus/trunk/BBSS/H1/BS/SAGM1/Data/2026-05-26_1700_tfs/2026-05-26_1700_H1SUSBS_M1_WhiteNoise_{L,T,V,R,P,Y}_0p02to50Hz.xml
r13020
Results
/ligo/svncommon/SusSVN/sus/trunk/BBSS/H1/BS/SAGM1/Results/2026-05-26_1700_tfs/2026-05-26_1700_H1SUSBS_M1_ALL_TFs.pdf
r13021

TITLE: 05/27 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    SEI_ENV state: MAINTENANCE
    Wind: 8mph Gusts, 5mph 3min avg
    Primary useism: 0.06 μm/s
    Secondary useism: 0.23 μm/s 
QUICK SUMMARY:

The LVEA is LASER SAFE

TITLE: 05/26 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: Work continued today in HAM2 and currently there is still work going on at the test stand on the BBSS.

The LVEA is currently LASER SAFE

LOG:

J. Kissel, O. Patane, B. Weaver, I. Abouelfettouh

Executive Summary: For now, we can damp the BBSS Glass BS with BOSEMs and old Level 2 BSFM Glass BS damping loops as long as the L and P EPICs gains are -0.5, all other DOFs are -1.0, and we turn OFF all DOFs of the BSFM bounce/roll mode notches.

Debugging damping loops for BBSS with BOSEMs mounted to the table cloth, we found that with direct copy of "old" level 2 damping loops for BS (a BSFM) was unstable, ringing up in L and P at 2.668 Hz (measured with t-cursors on an ndscope session). 

This is not a huge surprise; we'd already modeled the phase margin with this direct copy SWG:12301 has very low phase margin (modeled to be 23.8 [deg], with the highest upper unity gain frequency crossing at ~2.5 Hz; see dampingfilters_BBSS_2025-07-09.pdf page 33). Plus, experience has taught us that measured TFs often have more phase loss than models, so the phase margin of the loops is likely even less -- hence instability from 1/(1+G) gain peaking.

Ibrahim took some preliminary undamped TFs to confirm the (undamped) dynamical TFs of the BBSS with a glass optic. With what poor coherence we have in air, we can at least eye-ball confirm that they're not substantially different from the metal build on the test stand. Good! Great! We'll try to get these TFs better and Ibrahim will post for reference.

OK, with the dynamics checked out, on to the damping loops. Thus far the team had just rammed all the Level 2 BSFM loops on with a gain of -1.0, as we'd run them for years with the BSFM BS.

So, we did the dumb things first: 
    - We turned OFF the BSFM's BS highest bounce ("SB17.79" FM8) and roll ("SB26.06" FM9) mode frequency notch filters. We know these are the wrong frequency, and they're just eating up phase. (We plotted them, and it's not much at ~2 Hz, but they're the wrong frequency for a BBSS, so we just turned them OFF.) 
    - Turned on DOFs one or two at a time to narrow down which DOF(s) are problematic. T, V, R, and Y close fine and are stable with the old BSFM filters with a gain of -1.0. L and P are the loops that buzz at the 2.625 Hz (0.005 Hz resolution ASD with DTT).
    - Just reduce the overall gain of the loop(s) -- tried P at -0.5 and -0.25 with L still at -1.0. That was still unstable. But, L, P = -0.5, -0.5, is nicely stable, and damps stuff.

Getting slightly smarter, we checked in with the hard work of Vlad from LHO:81178 and found that the L and P filters have an EPICs gain of -1.0, and are identical in frequency response -- but the *filter* overall gain is a factor of 1.88x lower (i.e. essentially a factor of 2.0x). So -- he had to do essentially the same thing we did (though if I know Vlad, he actually measured this factor of 1.88x rather than blind guess like we did). Note that LLO's already using QOSEMs.

So, for now, we have something stable. Over time, we'll work on improving it, but this'll do. Once we have time, we'll take open loop gains, see exactly where we need phase, and adjust. Smart: Shouldn't need that much, change honestly. 
Just as I said in the acceptance review; Slides 33 and 34 of E2500057, we can easily relax the P low-pass filter and then regain the on-resonance pitch damping that we lost from dropping the overall gain by 2.0x.

Mitchell and I placed the new central beard baffle with a cutout for SPI on HAM2. It went on without issue after Mitch reminded me how to adjust the panels.

I then attached the accelerometer to the L bracket and tried hammering in various places. There wasn't much real estate, so I'm not sure how this will turn out. Data still needs to be analyzed, and I'll post pictures of hit locations then as well.

On May 19th, 2026, we took our first set of transfer functions for the BBSS after swapping in the glass optic. They all came out looking good, albiet very noisy because the suspension wasn't covered.

Comparing them to the last measurement we did in the staging building, the peaks still all match up well. There is just a consistance difference in magnitude, but that is probably just due to the difference in electronics between the QUAD stand in the staging building and the BS electronics in the LVEA.

Data
/ligo/svncommon/SusSVN/sus/trunk/BBSS/H1/BS/SAGM1/Data/2026-05-19_2000_tfs/2026-05-19_2000_H1SUSBS_M1_WhiteNoise_{L,T,V,R,P,Y}_0p02to50Hz.xml
r13018
Results
/ligo/svncommon/SusSVN/sus/trunk/BBSS/H1/BS/SAGM1/Results/2026-05-19_2000_tfs/2026-05-19_2000_H1SUSBS_M1_ALL_TFs.pdf
r13018
/ligo/svncommon/SusSVN/sus/trunk/BBSS/Common/Results/allbbss_May2026_BBSS_teststand_vs_staging/allbbsss_May2026_BBSS_teststand_vs_staging_ALL_TFs.pdf
/ligo/svncommon/SusSVN/sus/trunk/BBSS/Common/Results/allbbss_May2026_BBSS_teststand_vs_staging/allbbsss_May2026_BBSS_teststand_vs_staging_ALL_ZOOMED_TFs.pdf
r13017

Ryan Short, Tony Sanchez, Sheila

We took beam profiles of the sqz beam in the homodyne path using the Thorlabs M2Ms beamprofiler extension.  It made collecting data for a variety of psams settings much faster than using a scanning slit profiler alone.  

Tips for using this very nice extender kit:

• The visible alignment laser made alignment easy.
• We used the lens LA1461-C for 1064nm, the list of lenses and wavelengths is here: lens list
• make sure that the unit is plugged in, powered on with the power button, and connected to the laptop before you start the software.  Close and re-open the software if "translation stage control" and "M2 set" don't show up for you at the bottom of the "beam settings" window.  Once they show up you just have to go to the M^2 button and hit play to make a measurement.  
• You can get the fit beam parameters by saving a pdf by clicking the button that says "Save test Protokol", you have to hit save twice on the screen where you type a file name and again on the next screen.  "Save Measurement Data and results" gives you all the data, but not the fit beam parameters.  You again have to hit save twice.  
• Sivananda Reddy contacted Thorlabs and posted a diagram of where the reference plane is in the dcc: T2500077

We spent some time refinding the IR beam on the SQZT7 IR PD, documented this in it's own alog so it's easy to search: 90183

We set the profiler as shown in the attached photo.   The flipper mirror is 50.75" from the bottom persicope mirror, a steering mirror is 225mm from that, and the reference plane is 260mm from the steering mirror, so the reference plane is 1.774 meters from the bottom periscope mirror.  Leo Schrader has a helpful list of distances in the google document linked to T2500228.

• In 85282 Leo measured the beam distance from the top to bottom periscope mirrors to be 574mm. 
• The distance from the top of the persicope to the beam diverter was measured to be 84.5" in 61755.   
• In 75749 the distance from the beam diverter to ZM5 is listed as 1183.54mm based on a CAD drawing from Don Griffith. 
• This means the total distance from the reference plane to ZM5 is 5.678 meters.  We have left the profiler and temporary mirrors in place so that we can use them during the upcoming HAM7 vent.  

J. Oberling, R. Crouch, J. Warner, B. Weaver, I. Abouelfettouh

This week we surveyed the position of the components that reside in WBSC2: The BS SUS cage (BSS), the ISI optics table (ISI Stage 2), and the 2 ITM Elliptical Baffles.

BS and the SUS Cage

The first picture shows our FARO survey of points on the BS SUS cage, chiefly along the bottom of the main support structure.  These were surveyed by holding the FARO SMR against the hole being measured; the PolyWorks software handles the compensation from the center of the SMR to the point being measured.  As can be seen, each point is very close in both X and Y axis position, being less than 0.1mm from its nominal location.  The Z axis deviations are larger, but the largest of them is just over 0.25 mm, so every point is well within the positioning specifications used during installation and alignment in 2013.

Line 1 in the picture was created from the first and last survey points and represents the pointing of the BS SUS cage; all angles are reported in degrees.  Some things to note here: I'm using the Acute Angle datum in PolyWorks, which is the angle measured from the closest axis.  For the HR surface normal of the BS, the X Acute Angle is measured from the -X axis, the Y Acute Angle is measured from the +Y axis, and the Z Acute Angle is measured from the +Z axis.  Since Line 1 is roughly perpendicular to the surface normal of the BS HR face, the axes the angles measure from are changed: The X Acute angle is now measured from the +X axis, the Y Acute Angle is still from the +Y axis, and the Z Acute Angle is now from the -Z axis.  In addition, since Line 1 is nominally perpendicular to the BS HR surface normal I would expect the X and Y Acute angles to be swapped (BS X Acute = Line 1 Y Acute; BS Y Acute = Line 1 X Acute), but they aren't exactly.  This appears to be a small error in the CAD model, if we make the assumption that the BS HR surface and the HR side of the BS SUS cage are nominally pointing in the same direction.  This does, however, change the deviations for the X and Y Acute angles for Line 1.  The table below shows what the data for Line 1 should be:

This means the BS SUS cage is yawed 0.0626°, or ~1.09 mrad, in the clockwise (CW) direction when looking from the top down (since Line 1 is closer to the +X axis than it should be).  The Z Acute Angle represents a slight counterclockwise (CCW) roll of the SUS cage, when looking directly at the HR surface of the BS.

To attempt to better locate the BS in the IFO coordinate system, several measurements were taken with a ruler from points on the "Figure 8" section of the BS SUS cage to the BS optic itself.  All measurments except one were done using a scale with 0.5 mm tic marks (so accurate to +/- 0.25 mm).  The 10:00 "Figure 8 face to BS HR face" measurement had to be done using the side of the scale in inches, with 1/32" tic marks (so accurate to +/- 1/64") and then converted to mm (so accurate to +/- 0.4 mm).  The measurements positions are listed like the BS HR surface is a clock, and assumes you are looking directly at the HR surface.  The below table gives those results:

The BS sits decently centered in the Figure 8 portion of the SUS cage, a little bit low and to the +X/+Y side.  I would say not as much horizontally as it looks from the table, given the inherent error with reading the scale (the BS is not wider than its 370.0 mm specification, it's actually 0.15 mm narrower at 369.85 mm).  The pointing implied by this measurement, however, is more than a little alarming.  The 2:00 and 10:00 measurements show a significant yaw of the BS optic w.r.t. the SUS cage, and in the same direction as the yaw of the SUS cage as measured by the FARO.  There is ~320.0 mm between the 2:00 and 10:00 positions on the BS, so that 1.45 mm difference in depth is a 4.53 mrad CW yaw.  When added to the CW yaw of the SUS cage, this measurement shows that the BS optic is yawed 5.62 mrad CW from its nominal yaw.  Even assuming the errors fall in our favor (so the 2:00 at 25.0 mm and the 10:00 at 25.8 mm), that's still a 3.59 mrad CW yaw (2.5 mrad BS and 1.09 mrad SUS cage).  In addition, the 6:00 measurement implies a significant downward pitch of potentially several mrad, although with no way to measure the top of the optic we can't actually measure it.  I have to be honest, I'm having a very hard time believing this measurement; we will revisit this once the BS cartridge has been moved to the test stand, where we have a better field of view for the FARO, more room to work and much better lighting around the BS, and can take direct measurements of the BS position and pointing using a total station and laser autocollimator (although there is no guarantee that the optic will be pointing in exactly the same direction after being craned across the LVEA).  More to come on this.

ISI Optics Table

The second attachment shows the ISI positions as measured by the FARO.  I've corrected the Z axis positions for the length of the rod we use to hang the SMR from the ISI so they give a better idea of the Z axis position.  Not much can be said here, as LLO discovered that while these rods are good for measuring the Z axis position, they are not at all good at measuring X and Y.  This makes sense as they were designed to be accurate in length and only length, so there's no guarantee that X and Y are repeatable.  We plan on measuring the X and Y errors of this particular set of rods in the coming days (align to a table with a known hole pattern, attach the rod and measure with the FARO, repeat multiple times to see how the X and Y positions change).  For now, we can say that the ISI is lower on the -X side vs the +X side, and lower on the +Y side vs the -Y side.  I'm not alarmed by the deviations in Z axis position, as this ISI was supposed to be lower by ~2.5 mm (to place the BS in proper Z axis position, since it's lower in the IFO coordinate system but the SUS is the same length as the QUADs), but this was never captured in the CAD files.

ITM Elliptical Baffles

The final four attachments show our survey of both ITM elliptical baffles.  Our view of the baffles and available fiducials to take measurements from were both limited, but we can say a few things.

ITMx Elliptical Baffle

We were able to get two points along the +Y bottom edge of the baffle, a single point along the +Y top edge, and single point near the center of the -X bottom edge of the baffle.  From this I made a couple of planes that represent the +Y and bottom sides of the baffle and are shown in the third and fourth attachments; I, J, and K are the direction cosines of the surface normal of the plane, while the listed angles are the angle from the surface normal to the +X, +Y, and +Z axes. Interestingly, the point on the top edge looks very well aligned, within 1.0 mm all around, while the points along the bottom of the baffle are all low by several mm.  In addition, there appears to be a significant upward pitch to the baffle.  Jim did note that when attaching the transport bracket he had to push the baffle in the +X direction to clear ~0.5 mm at the point where the bracket attaches to the suspended portion of the baffle.  This point is roughly 476 mm away from the baffle's suspension blade, so this is an ~1.05 mrad angle.  Applying this same angle along the bottom of the baffle box gives an ~ -0.33 mm Z axis move of that bottom -X edge of the baffle, so this does not account for the measured deviation.  In addition to the pitch, the bottom plane also shows a large roll (CCW when looking at the ITMx in WBSC3), while the side plane shows a large yaw (CCW when looking from the top down).  We know these baffle panels aren't exactly straight, so it's hard to say if this significant pointing is also present on the elliptical hole of the baffle (we couldn't see it, so we couldn't measure it directly).

ITMy Elliptical Baffle

Similar to the ITMx baffle, we were only able to get a handful of points along the -X side and the bottom of the baffle.  I made planes from these points representing the -X side and the bottom of the baffle (fifth and sixth attachments).  As seen with the ITMx baffle, the points along the top of the baffle all look good while the points on the bottom are too low by several mm.  There is a significant upward pitch to this baffle as well, as well as a large roll (CCW when looking at ITMy in WBSC1) and yaw (CCW when looking from the top down), although none are as large those as seen on the ITMx elliptical baffle.  Again, we could not see the elliptical hole in the baffle to measure it, so we can't say if this pointing is an artifact of the panels or also present on the actual baffle portion of the baffle.

This completes our in-chamber measurements of the WBSC2 cartridge assembly, and closes LHO WP 13171.

I also want to note, Ryan and I also preformed some in-chamber FARO measurements in WHAM3 (ISI, MC2 SUS cage, PR2 SUS cage, MC2 and PR2 baffles) on April 10th; I will post those as soon as I get a chance to process the data in PolyWorks.