We have intalled the POP periscope stiffener.

Some dog clamps in the REFL path as well as the cable bracket for PM1 were relocated to accomodate. 1st and 2nd picture are "before" photo. 3rd one is after PM1 cable bracket relocation but before installing the stiffener.  There are also three "after" photos showing how things look on the table.

POP beam clearance:

I took the picture of the bottom periscope mirror through dichroic (HR for IR, transmission for green) to see the beam clearance. In the first such photo (POP_beam_clearance.jpg), the camera is close to the center of the dichroic and the short stiffener beam is close to the edge of the optic but not occulting the mirror, so we're OK. Just to make sure that we're absolutely safe, I moved the camera closer to the -Y edge (right on the picture) of the dichroic (POP_beam_clearance_extreme.jpg) and it still looks OK.

If it's hard to understand what was done, look at the annotated photo (the last attachment), the cellphone camera was inserted to "Camera" position.

REFL beam path:

I confirmed that the long stiffener beam doesn't interfere with the motion of the REFL beam diverter. Also, when the REFL beam diverter is open, I looked into the last steering mirror for the REFL air path from the viewport position to make sure that the short stiffener beam won't occulting the REFL path. 

Some hiccups:

We used D2500433 -11 variant S/N 4 and -1 variant S/N1 even though page 11 of T2500339 suggests it should be -10 and -2 variant, respectively.　We didn't have -10 variant, and -2 variant was absolutely too short.

B&K

We performed B&K hammer measurements before/after the stiffener installation. Before, there was a 70Hz-ish peak. After, it was pushed higher up in frequency. The transducer was attached to the ISI table and Jim hammered the top of the periscope.

Likewise we did B&K test for the input periscope of the JAC even though it was not absolutely necessary.

We haven't done B&K for the JAC output periscope because it's not even fully clamped down (we will move it).

Jim will post the data.

TITLE: 01/21 Day Shift: 1530-0030 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: Continued alignment for HAM7, and BNK measurements on HAM1 periscopes. Currently the LVEA is LASER HAZARD
LOG:                                                                                                                                                                                                                                                                                                                        

[Sheila, Karmeng]

FC1 alignment was adjusted to account for the buoyancy, and we coaligned the FC1 green/IR beam. We managed to recover the FC refl green on SQZT7 periscope, but not on the photodiode.

The OPO IR transmission is misaligned, and we managed to recover the IR on SQZT7 PD. As we recovered the IR refl (top) on SQZT7, we saw an improvement from ~600 to ~1680 (we may have been clipping on the refl PD previously).

By changing the setting on ZM2, we managed to improve the IR trans (bottom).

Old setting ZM2 PIT: 424 ; YAW: -235

New setting ZM2 PIT: 444 ; YAW: -315

Will need to check on the iris tomorrow, to make sure we did not deviate from the original path.

(Corey Gray, Randy Thompson)

This morning (during mostly laser Hazard) I assisted Randy with work on the eMod Platform. The eMod platform is the elevated large work platform which is installed over the TCSx In-Air Table and next to BSC3.  The eMod is an additional workspace to be used for the installation of the BBSS (Big BeamSplitter Suspension) into BSC2 in the coming months.

Today, we craned up handrails and installed them in place.  After this we rolled the white powdercoated spiral staircase into the LVEA from the HiBay and then used the crane to position the stairs next to the eMod.  The stairs were attached to the eMod floor via qty 3 long 3/8-16 bolts.  (attached is a top-view photo of the installed stairs).

After this we cleaned up our area and then staged the new horizontal HEPA filter assembly which will be used later for the BBSS installation.

Procedure checklist for both stations completed.  No issues were identified at this time.

MY: Scroll pump hours: 99.9
       Turbo pump hours: 238
       Crash bearings: 100%

EY: Scroll pump hours: 91.1
       Turbo pump hours: 1299
       Crash bearings: 100%
 
Closing WP 12986 FAMIS 31281 and 31289

FAMIS tasks 31322 and 31307, WP 12977

Procedure checklist for both stations completed.  No issues were identified at this time.

MX: Scroll pump hours: 238.6
       Turbo pump hours: 150
       Crash bearings: 100%

EX: Scroll pump hours: 7159.1
       Turbo pump hours: 1111
       Crash bearings: 100%

Tue Jan 20 10:09:37 2026 INFO: Fill completed in 9min 33secs

FAMIS 27832 TCS Chiller Water Level Top-Off - BiWeekly. 

Values added to spreadsheet. 
 

Workstations were updated and rebooted.  This was an OS packages update.  Conda packages were not updated.

TITLE: 01/20 Day Shift: 1530-0030 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    SEI_ENV state: MAINTENANCE
    Wind: 9mph Gusts, 5mph 3min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.25 μm/s 
QUICK SUMMARY:

Tuesday Maintenance Day today, but also we will be wanting to go back to Laser Hazard for the morning to finish up the HAM7 alignment, before doing some back and forth to and from laser safe.

Mon Jan 19 10:09:49 2026 INFO: Fill completed in 9min 46secs

Sun Jan 18 10:12:10 2026 INFO: Fill completed in 12min 6secs

[Jennie, Jason, Rahul, Keita, Masayuki]

We have observed the light coming out from the HAM2 after the MC1 reflection.
This is the summary report for the optics alignment in HAM1 after the JAC.

JAC_L1

An iris was placed and centered on the output beam from the JAC before installing the L1 lens. The lens was then installed such that the beam remained centered on the iris.

JM2

This optic will need to be repositioned after the EOM is installed. Therefore, we placed it without fine adjustment for now. The angular alignment was done using an iris located at the position where the HR surface of JM3 will be. Notes for final installation:

• The barrel must be cleaned before final installation.

• A beam dump must be installed behind the mirror.

JM3

Although JM3 also needs to be swapped to tip-tilt, the beam reflected from JM3 serves as the alignment reference after the EOM. Therefore, we performed careful alignment. An iris was placed at the planned location of JAC_M3, and the beam was centered on it by adjusting JM3.

JAC_L2, JAC_L3

The two lenses were then installed. They were centered using the same iris that had been used for the JM3 alignment.

JAC_M3

The angle of the reflected beam from JAC_M3 is critical, as it determines the polarization mismatch caused by the periscope’s rotation. An iris was placed at the output beam hole, and the beam was aligned parallel to the hole line. Previous measurements  confirm that the input beam axis to the IMC in HAM1 is parallel to the hole within ~1 mrad ([link]). Therefore, this alignment ensures that the polarization mismatch remains within acceptable limits.

Periscope (initial alignment attempts)

Initial alignment of the periscope was performed using the first iris (IR1) placed prior to installation.
Since the incoming beam was horizontal and parallel to the hole line, we expected the output beam to be rotated by exactly 90° and remain horizontal through the hole. After centering the beam on the iris by eye, we checked from the HAM2 viewport but did not observe the beam.

We attempted minor adjustments to the periscope, JM2, and JAC_M3. Some scattered light was eventually seen at the output periscope of the HAM2 IMC reflection path. However, IR camera footage from Keita showed that the focus did not match, and the light was deemed irrelevant. The detail can be found in Keita's alog.

Periscope (refined alignment)

On the following day, a second iris (IR2) was introduced to further constrain the horizontal alignment. This iris was placed approximately at the same height as IR1 and roughly aligned parallel to the hole line. The periscope was then re-aligned to pass through both irises.

From the POP septum window, we confirmed that the HAM2 periscope was visible and used it for alignment. Using an IR viewer, the beam was observed to hit the upper-left (10 o’clock) corner of the periscope structure. We switched to aligning JM2 and JAC_M3 using the top periscope mirror and IR1 as references (IR2 was removed at this point).

To identify the beam spot, we intentionally misaligned the pitch to make the beam hit the upper part of the periscope structure. To avoid blocking the beam, the iris was temporarily removed (its location was marked with three dog clamps; one clamp was slightly loose but the offset was minor, ~1 mm).
While keeping the pitch misaligned, yaw centering was performed using JAC_M3. Once centered visually, the iris was replaced, and JM2 was used to center the beam through it.
Fortunately, JM2 and the periscope top mirror are located at similar opical position, so the beam position remained nearly unchanged on the periscope mirror. This beam walking converged in two iterations.
The iris was removed again, and the beam was swept from top to bottom of the top periscope mirror using JAC_M3. The mirror was then centered using the midpoint of this motion. The iris was replaced, and pitch alignment was re-checked using JM2, again requiring just two iterations.

At this stage, some faint beam was observed using the viewer through the viewport. Although it wasn’t visible on a card, adjusting JAC_M3 slightly allowed us to confirm beam output from HAM2.

Final Checks

Finally, the IR1 centering was confirmed, and IR2 was placed near the periscope to act as a reference.
When checking the beam on JAC_L3, we found that it was offset by about 5 mm in the yaw direction. Further alignment is likely needed.
The beam spot on the periscope mirror is not perfectly centered, but it is close enough that no adjustment to the top mirror is deemed necessary.

[Sheila, Rahul, Karmeng]

A continuation of yesterday's progress. The additional power observed yesterday was due to the green for FC lock. We measured 0.75mW exiting the OPO, 0.74mW after SFI1 and also on the SQZT7 homodyne detector.

Today we reduced the saturation on ZM4 by clearing the offset and physically rotate the ZM4, we recovered the alignment on OMC QPDs and SQZT7 irises.

We also aligned the beam back to the HAM7 QPD A and B, at ~100nW for both of them, will need to re-centre the beam once we're back to laser hazard.

Betsy, RyanC, Rahul

This week we glued prisms (primary - sapphire and secondary - metal) to the HRTS OM0 fused silica Optic (D2100495-V5-OM0-0001). The gluing measurement details are recorded in the DCC - google spreadsheet (T2600012), link given below,

https://caltech-my.sharepoint.com/:x:/g/personal/rmcrouch_caltech_edu/IQBWQ2S3pJX9TZYxfDaXsCvfAcJh-mrpHPS2JGNtku6Srcg

Attachment01 and attachment02 shows the prism-optic in the prism gluing jig.

Attachment03 and attachment04 shows the base for the Bosem magnet/flag glued to the AR side of the optic.

Attachment05 and attachment06 shows the two prisms glued on both the sides of the barrel of the optic. Notice that the arrow points to the HR surface and there is only one scribe line on the optic. While in the jig the arrow should be pointing down and on the right hand side of the gluing fixture (facing down).

The optic is now on its way to LLO and will be suspended in OM0 in HAM6 chamber.

Since nobody seems to have made an alog, here it is.

We've steered the JAC transmission beam into HAM2 and removed the viewport cover on HAM2 on the +Y side to look inside. At first we had a hard time seeing anything. We steered the beam in YAW and PIT and still nothing.

After a while we found that if we position the IR viewer at a specific position and look into the baffle hole of the MC refl periscope (circled in yellow in the 1st attachment), we can see some kind of ugly IR that definitely comes from JAC, but no beam seemed to be coming out of the baffle hole.

2nd attachment shows the picture shot by an IR sensitive camra when we focused on the IR, and the 3rd attachment shows the same picture shot from the same position but focused on the  baffle.

The distance from the sensor to the subject according to the lens' indicator was something like 4m for IR and 1.5-2m for the baffle. The indicator is only good for visible light and not for IR, but empirically the scale is not a factor of 2 off for IR, so we're looking at something that is far from the baffle (i.e. we're looking at the image of the source reflected by the periscope mirrors).

Another possibility that Masayuki points out is that it could be some IR beam (probably not the main beam) hitting the vertical metal pillar of the periscope behind the bottom periscope mirror and we're looking at that through the space between the baffle hole and the periscope mirror (see the 4th attachment). I think that unlikely because the pillar is merely inches away from the baffle and the distance indicator of the lens doesn't agree. But we'll see.

Tomorrow we intend to remove the septum window cover for IFO REFL and POP and look into HAM2 from there, that way hopefully it's easier to find where the JAC beam lands in HAM2.

Attached is the mode-matching layout for the VOPO. The target primary waist of the VOPO (from TT1700104) is 221.2um(s), 206um(t) for 1064nm and 159.2um(s), 148.8um(t) for 532nm.

The mode matched minor and major beam waist is 198.6um, 204.2um for 1064nm and 152.6um, 185um for 532nm. For the fundamental injection via the rear mirror, the measured waist is 197.25um, 231.85um. These waist is measured at the position marked with a "star". The mode-matching calculation has been reviewed by a fur-low scientist.