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

Toward the end of day two of install (LHO:83961), the team set the power at the input of the ALS-FC2 by rotating ALS-HWP2, to be 50.5 [mW] (with PMC TRANS at 103.5 [W]). The reported power for the on-table ThorLabs SM1PD1A, however, measured consistently lower at "31 [mW]," lower than the goal for this PD, a reported power of "45 [mw]" (LHO:83927), when the power of the beam between ALS-M9 and ALS-FC2 was physically measured at 48.7 [mW] (with PMC TRANS at 103.0). 

We think lower reported power on the PD is related to 
(1) The slight translation of the what-used-to-be ALS-L5 to ALS-M9 beam, because of the thickness of the SPI-BS1 that was inserted into that path, and 
(2) a change in the amount of s- and p- polarization in reflection of the ALS-PBS01 after rotating ALS-HWP2 to increase the power in the ALS/SQZ/SPI path, because the polarization state of the reflection of a PBS can be power dependent.

To support (2), we measured the polarization today between ALS-M9 and ALS-FC2 with a temporary PBS and power meter. On 2025-04-17 at 19:02 UTC with PMC power at 103.7 [W], we measure
    s-pol = 49.7 [mW]
    p-pol = 1.8 [mW]
    (total = 49.7 + 1.8 = 51.5 [mW])
Regrettably, we did not measure this polarization state prior to changing anything.

However, because we've *measured* equal total power at ALS-FC2 before vs. after, we're confident that at least the total power going into ALS-FC2 is the same. 

As such, we called in Jason to help couple the beam into ALS-FC2 using ALS-M9 and what alignment screws are on ALS-FC2 itself. Attached is the trend of that process, where we used the SPI distribution chassis PD in two forms: 
    H1:ALS-C_FIBR_INTERNAL_DC_POWER         never calibrated version, used to be 0.1 [cts]
    H1:ALS-C_FIBR_INTERNAL_DC_POWERMON      version we'd been using, calibrated into [mW]

In the end, we landed with the values of these channels at 

    H1:ALS-C_FIBR_INTERNAL_DC_POWER         0.1 [cts]
    H1:ALS-C_FIBR_INTERNAL_DC_POWERMON      31.4 [mW]
which matches our goals from LHO:83927.

The team also adjusted the position of the SM1PD1A in transmission of ALS-M9 to account for (1). However, even after moving the PD out of maximum and back, they were not able to find any position where the PD readout exceeded
    H1:ALS-C_FIBR_EXTERNAL_DC_POWERMON      31.0 [mW]
This why we expect that something more like (2) is going on. Though we looked through 
    - E1300483 (doesn't list ALS-M9), 
    - E1900246 (calls the optic ALS-M6, which is not for 1064 nm in E1300483), 
    - E0900325 (isn't new enough to have this mirror), 
    - Peter King's purchase orders circa 2019 (Req 122638553 for the fiber collimator parts, and Req 122583017 for the SM1PD1A parts)
we couldn't find anything that was clearly and obviously the ALS-M9 optic, so we can't validate or reconstruction the reflectivity in each polarization to model the factor of 31 [mW] / 45 [mW] = 0.7x (or 30% drop) reported value change.
In any event, this EXTERNAL PD channel will need to be recalibrated to better reflect the real power in this path.

Also, when we re-start up anything that uses the output of the ALS / SQZ fiber distribution, it may need to be adjusted to account for the polarization change described in (2)

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

The SPI pick-off path installation on the H1 PSL table is now complete. The beam in the new SPI path has been reduced to 20mW and is currently being dumped with a razor dump between SPI-L1 and SPI-L2. Pictures attached reflect the final installation and layout, which will be be reflected in the updated as-built layout at a later date.

Associated entries: 83925, 83933, 83956, 83961, 83978, 83983 (and more to come)

Still on schedule!

Currently in the Stand-down in HAM1 such that the corner pump down can get to a more exercised safe state.  

Attached is a snapshot of what is planned for the next few days.  

(Things un-checked on today's list are expected to continue early next week per plan.)

RyanC, Rahul

SUS Tip Tilt - RM1, RM2 and PM1 (picture attached) are now ready to be installed into HAM1, once the chamber is ready to accept them. The blade springs of all three suspensions have been un-muted and bosem connectors have kapton take inserted to prevent grounding issues. This morning we cleaned all three optics using First Contact - see picture for reference.

PM1 Beam Dump (rear)

Camilla, Betsy, RyanC, Rahul

SUS PM1 (Tip Tilt) has a new beam dump attached to it's rear - as shown in several pictures attached below. We had to design a new plate (D2500101_V1) to attach the beam dump. I can confirm that all the components integrates well with PM1 and there is some scope for adjustability as well.

Team SUS is now ready for HAM1 installation work.

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 %.

FAMIS 27813
HEPI trends for the last month.

The sudden drop in the HEPI trends happened on the same day at the same time as the Power outage .

The last week can be see here and looks good except for today which show multiple DAQ restarts.

Brian, Oli, Edgard

Testing the implementation of the OSEM estimator installed on SR3. The models were installed on Monday. We don't have the model transfer functions yet. We were testing the basic OSEM path and the switch. We were testing SR3 YAW. It all looks good so far - the OSEM signal is getting to where it should be, and fader-switch is working correctly.

-- detailed testing notes --

ISI is damped. vacuum is still pumping pressure is ~16 torr. Looks like the suspension is still moving because of temperature changes so we can't do useful TFs yet.
GPS time 14289 57082
Look at the drive level of the classic damper, the pk-pk with normal damping is about  -0.04 to +0.04

channels all start with H1:SUS-SR3_

Look at channels: M1_YAW_DAMP_EST_OUTPUT,  M1_YAM_DAMP_OSEM_OUTPUT,  M1_YAW_DAMP_SIGMON, M1_DAMP_Y_OUTPUT,  M1_DAMP_Y_IN1

Y osem damper gain is -0.5 instead of -1.0.  Gabriele changed this.

Test 1 - are the OSEM signals getting to the OSEM path, and is the damper control set correctly? - YES!

Set the YAW_DAMP_OSEM filter bank to be the same at the DAMP_Y bank
The output switch for the estimator is OFF - so the OUTPUT signal from the YAW_DAMP_OSEM filter does not get to the osem drives

Output signals of the 2 damping controllers should be the same - and they do look the same. Put them on top of each other and they seem identical

Test 2 - use the classic damping and the YAW_OSEM path, does it work? - Yes!

1. set the YAM_DAMP_OSEM gain to -0.4 (from -0.5)
2. set the classic damping gain to -0.1 (from -0.5)  (so 20% of the gain is in the classic path, 80% in the estimator path)

gps time ~...58716, Turn on the estimator. This should recover the previous normal damping.
Switch looks smooth - no glitching, no drama. comes on well
The drive levels look like 4 to 1 by eye (correct). total drive looks about the same as before.

Turn off estim path at ...58900 ish. OSEM input signal doesn't look any different (gah, really?!, of course not, it's all sensor noise)

Test 2 successful - switch seems smooth, damping paths look good

Test 3 - test the switch between OSEM path and Estimator path - is it smooth and well behaved? - YES!

Set Estim damping control to be the same as the OSEM damping control.

Set the OSEM Bandpass to 1 so OSEM_DAMPER and ESTIM_DAMPER inputs should match (they do) and the outputs should match (they do).

these three signals should all be the same now during the switch from OSEM to Estim
M1_YAW_DAMP_SIGMON (this is the switch output)
M1_YAW_DAMP_OSEM_OUTPUT  (first input)
M1_YAW_DAMP_EST_OUTPUT  (second input)
start around 59720 -

then switch back and forth several times - these signals all stay on top of each other and are indistinguishable.

GPS is about ...60100
Zoom in for a close look at the start and stop of the fade to look for glitching - I don't see any, see plot in comment.
Test3 - success - by eye we can no see any difference in the 3 channels.

In 82097 we got some constraint on the circulating power in the arm from the squeezer data set.  I'm working on looking at the data that Camilla took in 83660, and realize that with the higher nonlinear gain the frequency independent squeezing gives us a better constraint on the arm power.

Using known injection losses of 8.2%(google sheet),   and  6% extra HAM7 losses from 83070 gives 13.7% minimum injection losses for squeezing, and our known readout losses are 8.4%.  Based on 16.1dB of anti squeezing (for NLG of 19 as reported by Camilla) and -4.97 dB squeezing, the infered NLG is 18.7 and the total sqz efficiency is 0.694 (with 0 phase noise). This means that in addition to the 6% extra losses measured on the homodyne, we have another 12% unknown squeezer losses.  We can assign those 12.2% losses to either injection losses (unlikely since there isn't much between homodyne pick off point and injection into the OFI), readout losses that also impact the IFO readout, or squeezer readout losses that don't impact the IFO (SQZ to OMC mode matching). 

If the only IFO readout losses are the known losses, the IFO readout efficiency is 91.6%, and we can use the shot noise level without squeezing injected to estimate that the minimum arm power is 310kW.  Using the total squeezer efficiency and the known losses, we can place bounds on the readout efficiency between 80.4% and 91.6%.  The level of shot noise measured without squeezing mostly depends on arm power and readout efficiency, so this maximum readout efficiency gives us a minimum arm power of 310kW (all squeezer losses are injection losses, readout efficiency is 91.6% and arm power is minimum), while the minimum readout efficiency gives us 353kW (all unknown squeezer losses are common to IFO, which probably wouldn't be the case for mode mismatches). 

Ryan C, Rahul

L1BHDM1 which is the suspended configuration of HRTS (HAM Relay Triple Suspension) for O5 is now ready to be shipped to LLO (using ground freight). The suspension (all stages locked with EQ stops, torqued double nuts and tension removed from wires ) has been wrapped in several layers of clean foil/clean cloth and clean bag as shown here.

This shipment is expected to reach LLO sometime at the end of next week (25th April), if it leaves LHO today. The details of the shipment are given below,

Tracking Site Link: https://www.shipdbi.com/ HWB Number for TRK: 139289

FRS ticket - https://services1.ligo-la.caltech.edu/FRS/show_bug.cgi?id=33849

ICS (assembly record) - https://ics.ligo-la.caltech.edu/JIRA/browse/ASSY-D1900449-L1BHDM1

ICS (shipment load) - https://ics.ligo-la.caltech.edu/JIRA/browse/Shipment-13842

This is first of the total six HRTS which will be transported to LLO.

Jim, Tony, Dave:

We restarted h1isiham1 model four times and the DAQ twice:

1. Internal wiring change to model, no DAQ retstart for that but new common part with "missing ADC chans" fix was included which did require a DAQ restart. No issues with DAQ restart other than gds0 needed a second restart.

2. A copy-paste binary parts issue was found, HAM6 parts were included in HAM1. BIO parts were renamed, no DAQ restart was neeed.

3. HAM1 differs from HAM6 in BIO inputs in that it reads 64 input channels instead of just 32. Upper32 channel BIO part was added, which added slow channels, so DAQ restart was required. No issues with DAQ restart other than gds0 second restart.

4. To minimize binary chassis hardware, HAM1 and HAM6 share the first BIO card's binary output chassis, HAM6 uses lower 32 chans, HAM1 uses upper 32 chans. h1isimodel was changed to use BIO-0 U32 for outputs. No DAQ restart was required.

Current BIO hardware as see by models:

Thu Apr 17 10:09:38 2025 INFO: Fill completed in 9min 34secs

Late entry

4-16 (Wednesday) activities:
- The previously received, poorly packaged Inficon gauge has been tested, and found functional. These tests continue, and also the HAM1 vacuum interlock gauge will be installed soon
- The BSC8 Annulus Ion Pump - after some aux cart pumping - is now able to hold the annulus pressure, at the mid- E-6 Torr region
- The rough pumpdown of the corner has started at 16:20, at the OMC turbo station, with a pair of ISP-1000 mobile pumping carts. In 4 hours, ~185 Torr was achieved, which means 1930 l/s effective pumping speed, which well corresponds with the 2000 l/s theoretical speed of the pumps
- The rough pumping still needs to be terminated in the end of the days, and so it was at 20:20
- All the turbo stations have been prepared for the HV pumping at the corner

Closes FAMIS26039 , last checked in alog83802

Most of the HAMs looks more elevated than last time, due to the vent activities.

The BSCs look the same as when they were last checked.

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.

Janos - 9:50, LVEA

The X-manifold is valved out from the main volume both sides, the main turbo is pumping on it.
On the X-manifold I slightly opened up the suspicious blanked-off small Varian gate valve (see photo), to find out if it is opened or closed.
I moved very slowly the hand-actuator, and the pressure spiked up to the E-5s, then it immediately started to go down, now it is already at ~3E-7 (the initial value was ~1E-7).
So, the valve was closed and blanked off, therefore it wasn't stored appropriately, thus at the next opportunity (when the X-manifold will be vented), it will be removed, and blanked off.

Edgard, Oli

In 83662 it was discussed that the osem compensating filter z:p = 10:0.4 wasn't as accurate as it should be. Jeff worked out that the zero and pole from the satamp are 0.3835 Hz and 10.6103 Hz, respectively, so our compensating filter should be the opposite of that, with a zero at 10.6 Hz and a pole at 0.38 Hz.

Today we updated those filters for PR3 and SR3. They appear in all three stages in the initial OSEMINF filter bank (FM1) (H1:SUS-PR3_M{1,2,3}_OSEMINF_{sensor})  as well as in all three stages of the watchdog bandpass filter bank (FM6) (H1:SUS-PR3_M{1,2,3}_WD_OSEMAC_BANDLIM_{sensor}). So where before those filters there were 10:0.4, they now read 10.6:0.38 and have these updated zero and pole values. We've loaded in the coefficient changes.

I've attached the script that we used to update these filters below. It's an edit of Jeff's script in 80189

Jason O, Georgia M

ECR 1900246

This week we have been in the PSL installing a new fiber pick-off for the ALS and squeezer lasers. The old pick off is on transmission of the reference cavity while the new one is on the ALS bypass, after the PMC. Peter K started this work a month ago (alog 51610).

We currently have installed a mode matching lens (f=200mm f=150mm) between the beam splitter and the steering mirror, and achieved ~73% ~82% power transmission through the fiber so far.

We think we can get more light through the fiber by tweaking the mode matching lens position. We will need to go back into the PSL again to finish this work and feed the fiber and photodiode cable out to the rack. 

Once the layout is finalised I'll update the psl table layout document (D1300348).

Modifications to the fiber distribution box are also ongoing.