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.

FRS37572 ISI HAM and BSC WD Plots Not Working

Ryan C, Erik, Dave:

The MEDM buttons to plot the latest ISI WD trips (see attached) have not been working for some time.

We found the issue was due to the wd_plot python code running in the conda environment had pydv issues, but if ran in native debian it worked.

Fixing the conda pydv issue would take significant resouces, so we chose to change the MEDM launcher to explicitly run local /usr/bin/python3.

The common MEDM file ISI_CUST_CHAMBER_WATCHDOG.adl in the isi/comon/medm/[hamisi, bscisi]/ directories were changed accordingly.

I tested with HAM2 and BSC3.

[D. Kapasi, S. Dwyer]

We can calculate the SR3 hot radius of curvature (sr3_roc_hot) from the HWS measurements [1] and readback heater power for SR3 [2].

• The average wavefront change, delta_W = (5.9 µD/W + 5.4µD/W)/2 * 1.9W. This is also called as the spherical power (delta_S since it is a differential measurement). delta_W = delta_S = 1.0735e-05 D.
• The spherical power is the inverse of ROC. Therefore, delta_S = 1/delta_ROC where delta_ROC = sr3_roc_hot - sr3_roc_cold (this is a positive quantity since we know that heating an optic (assuming uniformity) will increase the ROC).
• In diopter units, for a curved mirror we can write : D = 2/ROC. Therefore, delta_D = D_cold - D_hot (since ROC_hot > ROC_cold).
• Hence, 2/delta_ROC = 2/sr3_roc_cold - 2/sr3_roc_hot -> 2(delta_S) = 2/sr3_roc_cold - 2/sr3_roc_hot. Solving this gives sr3_roc_hot. 
• The factor of 2 highlighted above is independent of the factor of 2 used for double pass on SR3.

In our case - 
sr3_roc_cold = 36.013; % radius of curvature in m [3].
Therefore, 2*(1.0735e-05) = 2/36.013 - 2/sr3_roc_hot -> sr3_roc_hot = 36.027 m.

Sources
[1] alog 88413 - this give HWS values in µD/W.
[2] alog 88155 - gives the reported readback power and requested power for SR3 heaters.
[3] git issue #33.

J. Kissel

As I'm building up the MEDM screens for SPI, I'm finding some bugs in the Simulink model. This one: 
According to D2400111-v6, and the ADC/DAC Channel Usage Table in G2401479-v3, ADC3 CH20 = PWRIN_REF and ADC3 CH21 = PWRIN_MEAS. 

The initial release of the SPI model at LHO (LHO:89777, ${USERAPPS}/spi/h1/models/h1spih23.mdl userapps svn rev r34928, ${USERAPPS}/spi/common/models/SPI_LIBRARY.mdl rev r30005) had these flipped with ADC3 CH20 = PWRIN_MEAS and ADC3 CH21 = PWRIN_REF.
 
I've fixed the bug, and the top level and library are now at rev r35060 and r35059 respectively, and Dave's installing / restarting for me. No DAQ restart required, as it's just simulink wires getting uncrossed.

Closes FAMIS 39955

Last checked in alog 89599.

All trends look consistent and/or similar with last month's with the exception of the EX pump, which Jim commented on last time. This pump was seen going up in pressure. This pressure has since remained stable.

Closes FAMIS 39863. Last checked in alog 89728.

EY_FAN2_470_1 (green) and both EX fans are going through some quiet lapses that were only seen once in the last alog. Nothing is near the "noisy" threshold though.

Plots attached.

Thu Apr 16 10:10:09 2026 INFO: Fill completed in 10min 6secs

TITLE: 04/16 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: 20mph Gusts, 13mph 3min avg
    Primary useism: 1.01 μm/s
    Secondary useism: 0.27 μm/s 
QUICK SUMMARY: More work in BSC2 planned for today to prepare for dome and cartridge removal. A M6.0 earthquake from New Zealand is passing through.

This afternoon Mitch and I went to the chamber and after putting a little extra pressure on the locking screws, we started taking tension off of the springs. All springs started around 2k lbs each, we left them with about 400lbs each. Before transferring load to the stops, I used the screws to push HEPI about 100 um above the reference position. RX,RY and RZ were all within 25urad, X&Y were about 80um away from the reference. Right now Z has settled about 100 um below the reference position, all of the other positions are nearly unchanged. First thing in the morning we will drop all of the springs to ~150lbs each and re-assess the position. If things are still good we will attach dial indicators and get ready to remove the actuators.

First attached image are the after (left side readouts) and before (right) IPS readings. Second image are the cartesian IPS locations in nm or nrad, left column is after spring relief, right is before.

TITLE: 04/15 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY:

IFO is in IDLE and MAINTENANCE

Did not end up taking the dome off but went in for more measurements/FARO of the beamsplitter. Most of the setup from dome removal is done and dome removal is slated for tomorrow.

LOG:

This afternoon, Ryan C and I hopped into BSC2 (via BSC1) and took a few more measurements of the optic position relative to the cage for Jason and the IAS mapping.  Jason will periodically post some data which consolidates these more nicely visually.  In the end, we found the BS optic rotated clockwise in it's cage a small amount (likely how we installed it), namely 1mm out of plane from one side to the other.

I retook the ETM OPLEV charge measurements this afternoon after the changes we made last week (HV switched off for ETMY digitally, and the sign of the bias offset flipped for ETMX from alog89809). I'm not sure why the error is larger on EX than EY, the wind was medium high but that would effect EY more than EX, the ends were seeing similar ground motion in the 0.03 - 0.1 band. I had no issues running the script, I switched it from scipy to numpy last week.

The sign change appears to be successful in reducing the charge on ETMX, every DOF/quadrant saw its' charge reduced from last week. We will be trying to measure this weekly now to confirm and possibly fine tune the settings.

ETMYs' charge looks to be  approximately the same as the last measurement, although 2/3 of the DOF/qs saw a small trend away from zero of <5 [V] at most compared to last week. The trend of the charge on EY from Nov (previous measurement) to last week was toward zero on all DOF/qs but there was a much larger time difference between those two sets of measurements (~five months vs ~a week).

Following up on this report ALOG89822 and this work permit WP13164 we replaced two Kepco Power Supplies at EX.  These supplies source power to ISC and TCS racks in the EX CER room.

The +/- supplies were still running but the fan on the -18V supply had siezed up, and the supply was overheating.  The +18V supply seemed ok, but when I turned them both off it would not restart.

The +18V supply is now S1201904 has improved fan installed.
The -18V supply is now (no serial number) has improved fan installed.

Both supplies were set back to their original voltage configurations and power sequenced back on, this was completed yesterday afternoon.  The pulled supplies will be upgraded with new fans and placed back into spares inventory.

FAMIS 31133

On Friday, h1psl0 was rebooted as part of updates to its timing card firmware and RCG (see alog89859), which unlocked the PMC briefly and left the ISS off (on purpose, the autolocker is turned off in SDF so that it can be turned on later once the PMC thermalizes). It looks like the PMC (as usual) relocked at a slightly different temperature; it doesn't appear to have much effect this time on the transmitted power, but the reflected power is very slightly lower. I've turned the ISS autolocker back on.

Nyath, Jonathan:

Nyath has started the upgrade of the subversion repository server. This service will be down for a few hours.

Wed Apr 15 10:09:01 2026 INFO: Fill completed in 8min 58secs

Attahed and in the table below are oplev positions for ITMY, ITMX and BS since last DRMI lock on 03/19/2026 at 11:02 PDT

Note 1: The BS Oplev Damping loops were still on during some FARO work and were shaking the BS. We turned these off on morning of April 14.

Note 2: The right-most T-cursor marks the corner-station vent

(Travis, Randy, Gerardo)

On Monday, the -Y door went on the HAM1 chamber with some minor issues not noted on previous installations, for some reason we had two minor misalignments: one, the door did not hung parallel to the HAM's flange,small tilt towards the outside on the upper part of the door, maybe the pick point slid forward.  Two, the door required a clocking move, we pinned two holes spanning 5:12 O'clock, then rotated the door clockwise a bit until all of the holes aligned, then a small movement on the -Z to complete the alignment about 1/8".  After all of that the door looks pretty concentric to the chamber flange.

Something to note, a dirty glove was found inside the chamber, yes inside the chamber under the support tube on the -Y side of the chamber, as I write, I nod, because it does not take much time to get this dirty thing out of the chamber.