Jennie W, Jason O, Masayuki N, Keita K, Jim W,

Summary: To check the function of the new EOM in chamber we made a measurement of the modulation indexes by locking the IMC and aligning the beam to AS_C with SR2. We couldn't get a good measurement of the sideband heights but this is probably due to the RF power being down by a factor of 100 from nominal. Will check with EE/Daniel on Monday.

First order of business was checking for stray beams at 100mW input power. Jason moved the BD we already placed for JM2 as we had moced this mirror position yesterday. We also put a new beam dump right after unused JAC port (output side there is tranismission through the curced mirror).

After this we turned the power up to 1W.

Lastly we found a stray beam exiting the table in the -Y direction, this was traced to the JAC REFL path. The REFL beam was hitting the side of a beam dump (near the -X side/PSL of the table) which is meant to cath a beam reflecting off the SEPTUM plate. This beam reflected off the beam dump causing a stray beam. We re-aligned the REFL path so the beam does not do this and instead bounces off the three REFL path steering mirrors and heads into a previously placed beam dump for this purpose on the -Y side of the table. This path will have to be re-aligned in order for the beam to get onto the IOT1 table.

No further stray beams were found so Jason de-energised the waveplate.

Photos to come.

After realising that the beam did not reach the AS_C,A and B QPDs yet we came to the control room to re-align to the output port. This is with the ITMY, PRM and SRM mirrors mis-aligned to allow us to mode scan the OMC in the 'single bounce' IFO configuration.

After Jim re-isolated HAM4,5 and 6 and BSC2 for us we were able to use SR2 to bring back the alignment to AS_C and then turn on the DC centering loops for AS_A and AS_B.

The OMC ASC did not work at first as the suspensions were railed. I cleared the ASC history, this did not help. We cleared the locking filter banks for OM1-3 and this unrailed the outputs and allowed us to turn on the OMC ASC.

We took an OMC scan at 1W input power, shown here. Roughly calibrated into MHz with the known FSR.

We cannot identify the 45MHz or 9MHz peaks, but after checking we realied that these RF driver powers were lowered 15 days ago. See image.

We will come back to this Monday.

Jason put back the rotation stage, locked it out and closed the light pipe.

In the control room, the alarm handler was complaining about opticsd lab dust monitor.

It seems that it surged up and stayed there for about half an hour. I acknowledged the alarm (the dust conts are already back to normal, it seems).

Not sure what happened but this seems to happen kind of regularly.

J. Wright, J. Oberling

As part of WP 13006, we added another beam dump and moved one to ensure all stray beams that we could find were properly dumped.

We added the required beam dump on the unused output port of the JAC, to dump the unused beam here.  We also moved the beam dump that catches the leakage beam through JM2 so that it continues to dump this leakage beam in JM2's new location (needed to move JM2 as a result of EOM installation).  See the 2 attached pictures.

While scanning for other stray beams, I noticed a beam on the outside of the large beam dump that was temporarily relocated to the +X side of the new JAC input periscope.  This was traced to the JAC REFL path.  Turns out that when the REFL path was installed, the beam was erroneously reflected off of this beam dump on its way from JACR-M1 to JACR-M2.  To fix this we had to loosen the dog clamps for JACR-M1 and physically rotate it until the beam was centered on JACR-M2 (there wasn't enough range in the yaw actuator).  We then had to loosen and physically rotate JACR-M2 so that the REFL beam was once again captured in its temporary beam dump (dump located on the -Y side of the ISI).  Both mirrors were re-secured to the table.  Unfortunately, this means that we will have to revisit REFL path alignment to the new IOT1 table.

Modulation depth measurement work has been completed for the day, so I have returned the PSL power in HAM1 to 0.1 mW and de-energized and locked out the PSL rotation stage.  The PSL shutter has also been closed and locked out for the weekend.

We will need to revisit the modulation depth measurement on Monday, so I am leaving WP 13006 open and extending its date.

Today Rahul and I worked on reducing the last bit of clipping in HAM7.  The power budget shows a couple of percent more loss than we've expected previously, but I don't think we can improve it much right now so this is good enough. QPDA segment 3 is railed. 

This morning we found that we had some loss on B:L2, see Rahul's power budget alog as of lunchtime: 88971.  In hindsight, this was also possible in the power budget that Kar Meng reported before the suspension work this week, 88847. We translated the beam in the -Y direction in the SFI2 aperture, so it would make sense that we might need to translate the lens in the -Y direction.  However, there is no space to move it because the mount is already as close as it can be to SFI2 (photo).  So, we translated the beam using B:M3, using the power meter to judge when we were improving the alignment.  We found that this aperture is very small, there isn't much of a plateau where we aren't clipping.  

After doing what we could to reduce the yaw clipping here we did a careful power budget with the thorlabs power meter, we seem to have  8% loss to SQZT7, 11-14% loss from output of the OPO to the homodyne, which is a bit worse than past measurements ( 65066): 

• Opo 0.97-1mw
• Input to sfi1 0.97 mW
• Output sfi1 0.95 to 0.97 mW
• Hitting zm1 0.95 to 0.97 mW
• Return from filter cavity after sfi1 0.92 to 0.97 mW
• After BL1 0.93 mW
• Input to sfi2 0.92-0.94 mW
• Output from sfi2 0.91-0.92 mW
• After B:L2 0.86-0.91mW 
• After bm4 0.86-0.90 mW
• On the table bottom of the periscope 0.87-0.89 mW
• Before the homodyne 0.86 mW
• Refl power 24mW

We attempted to move B:M3 in pitch to see if we could reduce clipping on B:L2 that way, but that did not improve the transmission.  In pitch we also saw that we increased the clipping with small moves in either direction.  I will try to look up the beam size and aperture size next week to see if this makes sense.  

We adjusted B:B4 and ZM4 a bit to align onto the two irises on SQZT7. 

We also walked the two picomirrors used to center the FC QPDs, with the seed beam which saturates the diode.  From the control room I reduced the power and was able to mostly center, but it seems that QPDA segment three has been railed at 33.9 since November 29th.  

After we finished up, I went back to check the FCGS alignment onto SQZT7, which was not good, so I went back in for a few minutes to get that beam onto the filter cavity reflection diode.  I also had a look at the red + green co-alignment, which looks similar to what Kar Meng posted in 88859.  

We also checked that the new cable routing doesn't block the beam onto H:PD1, we couldn't see the beam but we think it looks like a clear path.  Rahul also took a photo of where the beam exits SFI2. 

TITLE: 01/31 Day Shift: 1530-0030 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY:
JAC team seems to have made some progress today... the MC was locked in air today.  
SQZ Team went to align the beams in HAM7.

Rotation stage is de-energised, Lightpipe is currently open. The JAC team are hoping to get some tests done before EOD, and the LightPipe will be closed before they leave.

LOG:

[Keita, Jason, Masayuki]

Summary

The beam alignment inside HAM1 was carried out using JM2 and JM3 after the EOM installation. Alignment was optimized by observing higher-order modes (HOM) and maximizing TRANS peak power. After verifying the presence of a PDH error signal at IOT2, the demodulation phase was adjusted since the new EOM will change the modulation phase due to the location difference. The IMC was then successfully locked using the common mode servo, following the Guardian sequence manually. The tuned IMC-REFL_A_PHASE was 20.87°

Detailed Procedure 

• Beam alignment inside HAM1 was performed using JM2 (scratched) after EOM installation. The beam was aligned to an iris placed between JM2 and JM3 using JM2’s mirror position and angle. The beam position matched the iris within approximately ±1 mm.

• Further alignment between JM2 and JM3 was done using the iris after the periscope. A beam walking procedure was used: JM2 aligned the first iris and JM3 aligned the second.

• After this, the Septum window cover was removed. The beam reached the IOT2 table, but there was a yaw offset. JM2 was further adjusted to correct it (note: yaw in HAM1 corresponds directly to yaw on the IOT2 table).

• A small sweep of JM2 in pitch and yaw revealed a very weak resonance peak. To excite the cavity, a 0.1 Hz, 300 cnts signal was sent to the TEST filter of MC2 M1.

• The TRANS camera showed the presence of a higher-order mode (HOM) with a pitch misalignment. Beam walking was repeated: small adjustments to JM3, followed by peak maximization with JM2. After several iterations, yaw HOM became dominant, so the axis was adjusted accordingly. A final pitch correction increased the TRANS power to approximately 6 cnts, concluding the alignment.

• Returning to the control room, the IOT2 shutter was opened. A PDH error signal was observed, confirming that modulation was present. Since the signal appeared primarily in the Q-phase, the demodulation phase was rotated by 45° using a delay line circuit.

• The common mode servo gain was set to 14 dB. When the input switch was engaged, the system began to catch resonance. By enabling the Lock filter on MC2 M3, the cavity successfully locked. The Lock filter for MC2 M2 was then engaged with gain 0.1, and FM3 was turned on, allowing stable long-term lock. These steps followed the Guardian sequence.

• A 50 Hz, 400 cnts excitation signal was injected into the IMC_L filter, and the delay line phase was tuned to minimize the RF25_Q_ERR peak. The optimal demodulation phase (IMC-REFL_A_PHASE) was determined to be 20.87°.

Using Vibration Sensors To Gauge Health Of HVAC Fans Site Famis 27735
No big changes here, got a few spikes that are likely DAQ restarts.
 

TCS Monthly Trends Famis 38836
There are some large spikes in this data on days where we have someDAQ restarts.
 

(Randy Thompson, Corey Gray)

In preparation for the upcoming Bigger BeamSplitter Suspension (BBSS) Installation at BSC2 in a few weeks (~midMarch), a new type of cleanroom infrastructure was needed too allow for more vertical space for the cartridge to be craned in/out of BSC2.  Instead of using our standard large mobile cleanroom (which are used for HAM & BSC chamber work), a smaller clean space will be attached to the elevated work platform for BSC2.  There will be a "cleanroom tent" on this platform (here's the platform [white] with 2-sets of 4 "tent poles") and a new array of (qty-4) HEPA Filters Fans (same type as the ones on top of the large mobile cleanrooms which blow down) will be on the side of this cleanroom tent to push air flow horizontally for this elevated workspace for the BBSS install.

Randy designed a unistrut framework for this 4-HEPA fan Array (weighs 377lbs).  This morning this assembly was carefully craned into place on top of 3 unistrut brackets attached to the BSC work platform (in between BSC1 & BSC2).  For added support, this afternoon, Randy added a "leg support" on both ends of this HEPA Filter Fan Array (here is a photo of one of these legs that is in the Beer Garden).

Fri Jan 30 10:07:58 2026 INFO: Fill completed in 7min 54secs

TITLE: 01/30 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: 3mph Gusts, 1mph 3min avg
    Primary useism: 0.04 μm/s
    Secondary useism: 0.40 μm/s 
QUICK SUMMARY:
LVEA is LASER HAZARD with HAM1 & HAM7 still open for in chamber work.

Potential HAM7 work: 
 Tweak Alignment from cable Rubbing, OBO & TF

Potential HAM1 work: 
Align Path out
IOT2L Beam profile measurement at 100 mW
Replace JM1/JM3 fixed mirrors with HTTS
Lock MC with HAM1 in air
Bifricate LVEA HAM1/South Bay/Work at Height all Laser Haz, rest of LVEA Laser Safe



 

This morning Rahul took a transfer function of the OPO suspension and found that adding a zip tie to the new connector didn't help the transfer function, which is still similar to 88921.  We decided with Jeff to live with this as it is, and we spent the rest of the day working on resolving the clipping through the VIP introduced by alignment shifts that happened as we were addressing the cables.  

We moved A:M3 enough that we no longer see evidence of clipping in the SFI1 both passes, we measure 0.96mW out of the OPO and about the same power in transmission from SFI1 on the the return from the filter cavity.  We then saw that the beam was clipping in SFI2, and adjusted B:M1 until we were measuring about 0.88- 0.9mW after SFI2, but we had clipping on the aperture attached to B:L2.  We had nearly lost the beam to SQZT7 by this time, so we spent some time restoring that by adjusting pitch on B:M3 and yaw on B:M4 (with the platform unlocked it is difficult to adjust pitch on the tough pitch knob for B:M4).  This brought us to a point where we can see 0.7 counts on the OPO IR PD on SQZT7.  

At the end of the day, we were still seeing loss at B:L2, where the beam was only about 0.82mW.  We also need to restore the alignment onto the irises on SQZT7.  

We will need to readjust the alignment onto the filter cavity QPDs before we close the chamber. 

1. EOM was put in chamber and moved to its final location. One temporary iris, a cable bracket for the picomotors and one dog clamp for the last lens for JAC needed to be relocated as they interfered with the EOM pivot base.
2. In-vac cables were identified and were connected to the EOM. Minor annoyance about the cable strain relief.
3. EOM S11 coefficients were measured and were acceptable though the dip frequencies were not the same as in the lab, so we haven't retuned it.
4. EOM was connected to the RF sources (now we're modulating!).
5. The light goes into and comes out of the EOM.
6. We forgot that the EOM wedge has a big effect to deflect the beam. We started working on the alignment downstream of the EOM and this will continue tomorrow.

Details to follow.

TITLE: 01/30 Day Shift: 1530-0030 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: EOM is in!! Still some work to be done for HAM1 and HAM7. LVEA IS LASER HAZARD
LOG: