Just to confirm that there's nothing grossly wrong with the beam coming into PSL ISS 2nd loop array, I tried to minimize the jitter coupling from IM3 dither to PDSUM_INNER. If there is something terrible, we might have to change the IM2 and IM3 angle again, which will change the input alignment into the IFO, so it makes sense to say that IM2/IM3 are good now. That way, ISS alignment will be truly isolated from the IFO.

I moved two picos for ISS and ended up with the following coupling in RIN/m:

• RIN_INNER: PIT 3.3, YAW 2.3
• RIN_OUTER: PIT 17.5, YAW 43.9.

This looks to be consistent with October/2025 measurements in the lab: https://dcc.ligo.org/T2500077-v4, the screenshot of which is attached here as 2025October_T2500077.png. INNER (i.e. PD1/2/3/4) PIT is somewhat worse, INNER_YAW is at least a factor of 3 better. (OUTER_PIT is somewhat better and OUTER_YAW is a factor of 2 worse, but I haven't tried to make OUTER sensor better.)

I went away from the center of the QPD: PIT=-0.603 YAW=-0.295, which corresponds to -84um in PIT and -41um in YAW. This is to say that the displacement is not huge at all. Don't try to center.

The first pico (ch1 for HAM2) was moved from (X,Y)=(0,0) to (569,-476), the second (ch8) from (0,0) to (685, -541).

Though individual diode outputs are all different from O4 days because of different alignment, PDSUMINNER and PDSUMOUTER are the same as in O4 (compare ISSpath_align_20260817.png with ISS_INNER_and_OUTER_in_O4.png).

I didn't make a huge scan so I don't know how far the beam is from the edge of the diodes, but this already looks OK to me. If needed we can search for a better spot position further without changing IM2/3.

What was done:

• Dither IM3 in PIT (6Hz, 40 counts into H1:SUS-IM3_M1_OPTICALIGN_P_EXC) and YAW (8Hz, 40 counts).
• Look at the peak height in each PD like H1:PSL-ISS_SECONDLOOP_PD1_OUT_DQ.
• Move two picos. At first maximize the DC of PDs, then tune further to roughly minimize the dither peaks in the INNER group (I cannot minimize both INNER and OUTER at the same time).
• Measure TF from ISS 2nd Loop QPD P and Y output to RIN_INNER and RIN_OUTER.
• QPD output is 7.2 counts/mm for the displacement of the beam along the QPD surface, assuming that the beam size in chamber is the same as the beam we used in the lab (see https://dcc.ligo.org/T2500077).
  • disp_[P|Y] = QPD_[P|Y] / 7200[ct/m].
• Coupling for [P|Y] in RIN/m = H1:PSL-ISS_SECONDLOOP_RIN/disp_[P|Y] = 7200[ct/m]*H1:PSL-ISS_SECONDLOOP_RIN/QPD_[P|Y] .

DTT template and my detailed memo of what was done are available in /ligo/home/keita.kawabe/ISS2ndAnd3rdLoop/ISS2ndLoopAlignment

This has been wrong for forever, I fixed it at one point a long long time ago (alog 29798) but apparently didn't put it in SDF.

Anyway, FM4 of H1:PSL-ISS_SECONDLOOP_QPD_SEG filters named 0.4:40 was OFF, it should be ON all the time like in the attached screenshot.  When it's wrong the signal looks noisier than it actually is and is annoying even though it's not used for control and doesn't matter during observing.

I accepted the change in the SDF.

[Matt, Jason O, Maik F (remote)]

We wanted to see the run hours on the PSL systems at both sites to check on the health of everything (and as an easy kickoff on the FCA review of the detector itself....see slide 10 of G2610464). The chillers we swap out regularly to get refurbished so we have no concerns there, but the PSL laser diode lifetimes are the point of interest here. 

LLO

LLO finished the O4 upgrade of the PSL circa November 2022.

LLO appear in very good shape. The run hours LLO have are:

AMP1: 30,427 hours

AMP2: 30,399 hours

From Maik "The diodes have the standard specifications of 20,000h but the vendor typically says that they will do more than 30,000h which you proved !"!

The diode currents for the laser diodes at LLO has not been changed from its initial set points at install.

Note: The laser diode current has to be changed as the laser diodes start to die to maintain the same output power from the diode itself and retain the thermal lens profile of the crystals inside the amplifier. 

LHO

LHO finished their O4 upgrade of the PSL circa February 2022. 

LHO are in a bit more of a concerning shape than LLO. The run hours LHO have are:

Amp1: 38,512

Amp2: 38,365

More concerningly from LHO's point of view, LHO HAVE had to start adjusting their laser diode currents to maintain output form their laser diodes. From Jason "We’ve been able to keep output power good by increasing the injection currents, but our PMC reflected power has more than doubled since install (~12 W -> ~28 W).  I can’t get it lower with injection current increases, further increases only increase PMC Refl; at this point we’d have to redo the mode matching to the PMC to restore our original power available to the IFO"

Summary

Both sites laser diodes are beyond the manufacturers specifications for runtime. 

LHO have around a year of extra runtime on their laser diodes and the LHO diodes have started to degrade in terms of performance. 

Each site does have a complete set of spare diode boxes that can be swapped in. LLO's have hours on them as they are part of the T&T lab setup, but LHO's should still be brand new (other than burn in time). However we do need to starting thinking/planning about refurbishing (or buying new), laser diodes for the PSL system. So at this point in time both sites should be fine for the IR1 run (however laser diodes typically degrade at a non-linear rate and so LHO will have to keep an eye on their performance and make a judgment call on if they think they need to swap theirs at some stage). However for O5 (or even the upgrades/commissioning before them), both sites are going to have to swap out to fresh laser diodes. 

J. Oberling, R. Short, T. Shaffer

This morning we swapped the temporary SPI shutter cable, for the shutter in the SPI pickoff path on the PSL table, with the permanent one.  Once the old cable was removed we fed it out of the PSL enclosure wall penetration to TJ, who then fed the permanent cable into the PSL enclosure for us (thank you, TJ!).  The cable was secured in the same was as the temporary cable was, see attached pictures.  We tried to physically move the cable into the ALS beam path and were unable to do so; at rest the cable is ~2.5" from the ALS path and the closest we could get it was ~2", so the cable is well secured and unable to drift into the ALS path.  This cable had been successfully tested with a spare shutter before installation, but due to the ongoing CDS upgrade we were unable to test it with the installed shutter; this will be done once everything is back up and running.  This completes LHO WP 13464.

We're checking the grounding of things in HAM2. IM4_TRANS QPD, ISS array QPD and all 8 ISS array PDs are fine.

IM4_TRANS and ISS array QPD:

Disconnected the DB25 cable from the transimpedance amp (ISC R4 slot 31) and measured the resistance between the pins and the chamber ground. (Ground potential for the chamber and the racks are significantly different, so we connected one cable directly to the chamber and measured the resistance between that cable and the pins.) 

All pins are isolated from the chamber. pin13 is tied to the shielding.

ISS array PDs:

Disconnected two DB25 cables from the second loop chassis (D1600229) in the PSL rack and measured the resistance between the pins and the chamber ground. Same caveat about chamber VS rack ground.

All pins are isolated from the chamber. Pin 13 is not connected to the shielding. This is fine, as this is a special cable made to convert four pairs of coax cables (total 8 coax) into DB25. Shielding of 8 coax is connected to pin14 through pin21 which are tied to the ground inside the second loop chassis. Pin13 is also connected to the ground inside the chassis. See D1600321.

Fil is done with SUS, some issues were found and he'll work with Rahul to try to fix them. He will also test picomotor grounding later.

R. Short, J. Oberling, J. Kissel

This afternoon we installed the shutter in the SPI pickoff path on the PSL table.  We installed it in between the 2 SPI lenses.  The cable was tied down with some dog clamps and cable ties, and we checked to make sure it was well clear of all known beams (it doesn't really look like it in the picture, but the shutter cable is ~3 inches away from the ALS beam and cannot drift into its path).  Once we ran the cable outside the enclosure, Jeff plugged it into the driver and we ran several on/off tests, with the shutter successfully actuating as expected, every time.  I'll update the as-built PSL table layout to include the shutter.

This afternoon I went into the LVEA (HAM2 clean room area) and canned & stored the old unit of the ISS PD - s/n S1202971. This unit was uninstalled on May 13th, 2026 and replaced with a new unit (S1202965) - see LHO alog 90237 for details.

I have moved this old unit (s/n S1202971) to the vacuum prep area of the optics lab (OSB) and stored it in the blue cabinet. 

Please see pictures attached below for reference.

Good news is that we're done with the alignment of the ISS path. Pictures and details are to follow.

Then I reinstalled the last IFO REFL baffle right in front of the HAM2-HAM1 septum window. (The baffle was removed after marking the exact position using three temporary dog clamps on the ISI on day 1 because it was in the way, I was supposed to record that in alog 90158 but forgot. I'm absolutely sure that the position of the baffle was restored within 0.1mm of the original position.)

Bad news is the IFO REFL was clipped on that baffle. 00 mode flash isn't clipped that much but horizontal modes certainly are. That was not THAT surprising because the IMC alignment was/is not great (see my comment 90224). This looks to me that the uncontrolled degree of freedom of the IMC is wrong regardless of the reason why a huge alignment change had to be made to center the MC2 TRANS QPD.

Good news is the ISS path alignment is not impacted by that, at least greatly, because we made sure that the beam hit the right location of IM4 TRANS as well as ISS array QPD before we did anything in the ISS path. Note that the baffle clipping the beam is not in the ISS path.

In other words,

• the beam position on MC3 might have been poor but we used IM3 and IM2 to steer the beam INTO the ISS path such that the alignment there is reasonably close to in-vac alignment,
• when the beam coming out of MC3 is brought back to the good position/angle, we can bring the beam back onto IM4 trans using IM3 and IM2,
• if the beam is not found on the ISS QPD at that point, we can scan IM3 (and IM2 if necessary) further to find the beam,
• and use the first pico for the ISS array path to keep the beam on the array QPD while slowly bringing IM3 (and IM2 if that's touched) back to the good angle.

However, since we don't want to revisit HAM2 once we close it, I'd like to understand what's going on for the IMC/IFO alignment. 

This is for FAMIS #39758.
Laser Status:
    NPRO output power is 1.841W
    AMP1 output power is 70.55W
    AMP2 output power is 138.4W
    NPRO watchdog is GREEN
    AMP1 watchdog is GREEN
    AMP2 watchdog is GREEN
    PDWD watchdog is GREEN

PMC:
    It has been locked 27 days, 19 hr 55 minutes
    Reflected power = 27.29W
    Transmitted power = 103.6W
    PowerSum = 130.9W

FSS:
    It has been locked for 0 days 2 hr and 22 min
    TPD[V] = 0.484V

ISS:
    The diffracted power is around 4.3%
    Last saturation event was 0 days 21 hours and 25 minutes ago
Possible Issues:
    PMC reflected power is high

F. Clara, J. Kissel, S. Koehlenbeck, J. Oberling, M. Pirello
D2400110

Today we picked up where we left off with the install of SPI into H1. 
Where we last left things, we'd installed a new SPI pick-off of ALS/SQZ beam in Apr 2025 (see ECR E2400083 and results in LHO aLOGs 83989, 83996, 83978). Back then, we had ended the work with the input to the fiber collimator within the PSL dumped.

With Jason and Sina in the PSL, we confirmed that the SPI path was still blocked. 

However, we also realized/remembered/confirmed that the entire ALS/SQZ/SPI path had 25% less power -- We've been running the PSL at lower power allocation downstream of the PMC since Sep 2025 to prevent issues we'd found with the currently installed EOM after a power outage triggered a dust monitor to spew out dust into the PSL (see that saga in e.g. LHO:87109 LHO:86966). They found the power at the SPI pick-off was 140 [mW] instead of the 188 [mW] we left in Apr 2025 (see LHO:83996).

(Using labels in the half-up-to-date drawing D1300348)
Jason and Sina rotated ALS-HWP2 upstream of ALSPBS01 to restore the nominal 50 [mW] into the ALS/SQZ pick-off and ~200 [mW] (190 [mW] measured). This means there's ~50 [mW] less out to ALS / ISCT1 than before today.

Then with the SPI pickoff still dumped, we installed a 30 [m] patch cord*** from the PSL optical table, out the mouse hole between the +X wall of the PSL enclosure and HAM1, then up running along the upper racks to waterfall down at SUS-H2. The fiber sits within the typical orange tubing. Per D2400110, this is SPI_PSL_001, and it's labeled as such on both ends.

After install, I connected the SUS-R2 end to a Thorlabs S121C power meter with S120-APC2 fiber adapter. 
With this installed (making the system laser safe at SUS-R2 end), Jason/Sina unblocked the SPI pickoff input. 
With 190 [mW] in, we measure 187 [mW] out on the other end. 98% transmission, pretty excellent. Almost unbelievably excellent but we weren't rigorous with our uncertainty and systematics.

Happy with this result, we then blocked the SPI path again, and re-capped the SUS-R2 end for final dressing in the racks.
We'll unblock again when we're read to connect it to the Laser Prep Chassis.

***Patch cord details:
Manufacturer DIAMOND
DIAMOND Part Number: ENS/1094388
Customer Part Number: 9711228
Patchcord SM L=30 PM
2xFC 2mm APC (i.e. 2mm narrow key FC/APC on both ends)
tran 6,6/125/245 PAND 980nm



 

J. Kissel, R. Short, J. Oberling

This is the first installment of aLOGs documenting the setup of a new stand-alone 1064 nm NPRO laser system whose current "end game" intent is to provide ~100 [mW] of fiber-coupled p-pol light to the SPI laser prep chassis.

Step 1: Gathering materials, find what optics / mounts we had vs. what would be need, and physically layout the plan.

Jason lets Ryan and I know that there are three NPROs in the optics lab, two of which are PSL spares that cannot be used. 
The remaining laser is S/N 1661, the laser used in the PSL during O3 which is *functional* but was briefly installed during O4 circa Fall/Winter 2024 then removed from use in the PSL because of reported glitching / incompatibility with the frequency stabilization servo (FSS) issues -- see the bottom of LHO:81391 for a nice summary, and LHO:81409 for record of its removal.

Inspired by the setup at Stanford Sina shared with us, we're looking to build up the following system to accomplish the goal:
    - NPRO (presumed to be elliptically polarized with Is / Ip = 5:1)
    - QWP (to linearize the polarization)
    - HWP1 (to rotate the polarization into horizontal)
    - FI (accepts horizontal linear polarization, to ensure back-reflections from down-stream components don't seed the NPRO causing glitches/mode hopes/frequency noise)
    - HWP2 (to rotate the FI output polarization into the desired amount of vertical polarization -- aka the desired amount p-polarization)
    - PBS (to filter out and dump the unneeded horizontal / s-pol light, and transmit the desired power of p-pol)
    - SM1 (one of two steering mirrors to align the beam into the fiber collimator)
    - L1 (the single-lens mode-matching solution to convert the NPRO beam into what the fiber collimator needs)
    - SM2 (two of two steering mirrors for alignment into the fiber collimator)
    - 50:50 PWR BS (45 [deg] AOI, optimized for p-pol; to provide a pick-off port for live power measurement)
    - Fiber Collimator

Ryan started with a 24" by 12" breadboard that was lying around in the optics lab. He build up a makeshift stand from three posts and dogs in the lower left corner such that the S/N 1661 NPRO projects the beam at 4" height. The 0.5" thick breadboard has a 1 inch hole pattern offset by 0.5" from the edges. I'll refer to this grid as having axes "m" and "n" where the m-axis are the "row" holes running from 0 to 23, and the "column" n-axis holes run from 0 to 11. I chose (m,n) breadboard coordinates so as to not confuse them with traditional beam profile coordinates of (z [propagation distance], x (transverse horizontal), y (transverse vertical)). 

Thus, the NPRO being in the "lower left" means it projects the beam along the m = 3 row, and the front face of the NPRO is sitting at n = 8. We'll call this beam position z = 0.

We then proceeded to gather as much as we could of optical components from the optics lab drawers, and ended up with this pictured preliminary version of the setup.

Step 2. Power up the NPRO.
Here's were we ran into our first snag. Normally, NPROs are paired/tuned with specific controller boxes. However, when Ryan turned on the S/N 1661 laser with the S/N 1661 control box, the crystal temperature readback reported the temperature was quickly, linearly rising well beyond the desired temperature of 24.7 [deg C]. At ~42 [deg C], (but still below the internal automatic watchdog threshold of 50 [deg C]), Ryan knew something was wrong and turned it all off. He repeated the turn on just in case, and it did the same.

After conversing with Jason, we figure it's good enough to run with one of the other controllers for now, and in the mean time figure out how what's wrong and repair the S/N 1661 controller.

So, we're running with the S/N 7974, and things seem fine. 
    Laser Diode Temp Setup:
        Diode 1 33.7 [deg C]
        Diode 2: 33.1 [deg C]
        Laser diode injection current readback 2.08 [A] (for both diodes)
    Crystal Temp setting is 24.7 [deg C]

We measured the output power*** with no optical elements at all as 1.820 +/- 0.005 W (not noisey, but a slow drift around).
Good enough! Onward and upward!

*** Power measured by ThorLabs power meter
	Model S302C
	SN 111149
	Sensing factor of 316.25 [mV/W]
	(last calibrated Feb 3 2012).

We replaced the failed +/-12V Kepco supplies in VDD-C6 U34 which power the PSL dome cameras
U34_LHS: +12V supply S1201947 removed due to failed fan, replaced with upgraded supply S1202017
U34_RHS: -12V supply S1201992 removed due to failed fan, replaced with upgraded supply S1300289

F. Clara, M. Pirello

This is for FAMIS #39750.

Laser Status:
    NPRO output power is 1.841W
    AMP1 output power is 70.43W
    AMP2 output power is 139.4W
    NPRO watchdog is GREEN
    AMP1 watchdog is GREEN
    AMP2 watchdog is GREEN
    PDWD watchdog is GREEN

PMC:
    It has been locked 0 days, 21 hr 23 minutes
    Reflected power = 27.19W
    Transmitted power = 103.9W
    PowerSum = 131.1W

FSS:
    It has been locked for 0 days 18 hr and 54 min
    TPD[V] = 0.4791V

ISS:
    The diffracted power is around 4.0%
    Last saturation event was 0 days 0 hours and 0 minutes ago

Possible Issues:
    PMC reflected power is high

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.

[Jason, Jennie, Masayuki]

• We swapped and installed three new lenses—IO_MB_L1 (Rc = 250 mm), L2 (Rc = −150 mm), and L3 (Rc = 750 mm)—replacing the existing lenses with the same notation. The former two are 1″ diameter lenses, and the latter is a 2″ lens. All lenses were mounted in Newport lens mounts, with posts and post holders installed on Thorlabs BA2 bases.
• Set the power stage to 2 W with 100 W of PMC output. The power along the path where the new lenses were installed was then reduced as much as possible using IO_MB_HWP1.
• Before swapping the lenses, two irises were placed to provide alignment references. The final reference is the set of irises in HAM1; however, the in-PSL iris allowed alignment without external communication and made the process easier. These irises were placed downstream of the existing IO_MB_L2.
• After removing the old lenses, the new IO_MB_L1 was installed such that the distance from IO_MB_M2 to L1 was 0.22 m. The beam was centered on the iris by adjusting the lens position. Subsequently, L2 was installed 6 cm downstream of L1 using the same procedure.
• After alignment, we verified that the beam path around the beam adjustment stage was not clipped by any optics. All beam positions appeared nearly identical to those before the work began.
• The third lens was then installed between IO_MB_M4 and M5 (the bottom mirror of the periscope) with a separation of 9 cm. To ensure the lens was centered on the beam, we centered the iris on the beam reflected from IO_AB_BS1 before and after installation. To observe the transmitted beam from M4, higher power was required; therefore, IO_MB_HWP1 was rotated to increase the EOM output power to 4–5 W.
• The first and second pictures document the original lens positions, in case recovery of the mode matching directly to the IMC is required.
• After completing the work, all power levels were restored. During this period, the new lenses were inspected with an IR viewer to confirm the absence of unusual stray light or unintended beam exposure.
• Remaining work: alignment of the photodiodes monitoring the EOM output and PSL output. Since the overall beam profile has changed, it may be necessary to reposition the lenses to properly focus the beam onto the PDs.
• During the work we found the beam is almost clipped on the beam dump capturing the mispolarized beam difracted by the EOM. So, we move the beam dump. The third picture shows this beam dump.

TITLE: 12/26 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: 25mph Gusts, 16mph 3min avg
    Primary useism: 0.05 μm/s
    Secondary useism: 0.90 μm/s 
QUICK SUMMARY:
Cameras:
Everything looks fine currently.  
Lights were left on in the Woodshop & OSB 163, ifsomeone is heading to site. 


SEI: Looks as I'd expect it to look. HAM7 is red because it's had people in and out of it since before the break. I imagine leaving that watchdog tripped is fine.
SUS: Seems to be looking reasonable as well considering the OPO and Jack work that was being done before break.

PSL Status: 

Laser Status:
    NPRO output power is 1.84W
    AMP1 output power is 70.51W
    AMP2 output power is 139.4W
    NPRO watchdog is GREEN
    AMP1 watchdog is GREEN
    AMP2 watchdog is GREEN
    PDWD watchdog is GREEN

PMC:
    It has been locked 16 days, 17 hr 48 minutes
    Reflected power = 25.41W
    Transmitted power = 106.2W
    PowerSum = 131.6W

FSS:
    It has been locked for 2 days 23 hr and 15 min
    TPD[V] = 0.5254V

ISS:
    The diffracted power is around 3.7%
    Last saturation event was 2 days 22 hours and 25 minutes ago

Possible Issues:
        PMC reflected power is high
 

VEA Temps:

LVEA looks good for the last day.

The HAM Shaq looks good.

Arm VEAs

Betsy, Rahul

We found that SUS JM1 had a faulty quadrupus cable, which we replaced it today. Next, I took OLC for both JM1 and JM3 in HAM1 chamber. I applied the offsets, gains and then centered the BOSEMs - and they look good. Next, I will start checking the health of the electronics chain and the suspension itself (i.e. by taking the transfer function measurements).

The offsets and gain for JM1 is recorded in this screenshot - accepted in the SDF (safe).

The offsets and gain for JM3 is recorded in this screenshot - accepted in the SDF (safe).

For the upcoming ISS array swap, we plan to bypass the IMC, which is known to be a pain, but we need a stable beam for the array alignment.

Once the corner volume is vent, we use the QPD on the old array and IMC-IM4_TRANS as the initial reference for bypassing the IMC. Once IMC is bypassed, we will center REFL WFS BEFORE removing the old array and record the RM1/RM2 PIT and YAW. This way, even if we somehow suspect e.g. the pointing of the beam going to the IM4 moved after removing the old array, we can still restore the pointing by looking at the REFL WFSs in addition to IM4.

We measured the beam positions on these QPDs today even though we'll repeat this later.

IFO configuration:

• IMC was locked with 2W.
• REFL beam diverter was closed so no light comes out. (POP bdv was also closed just because.) 
• The cover on the REFL septum window was removed.
• PRM, all IMs and RMs are aligned. (Watchdog of RMs were reset.) ITMs are misaligned.

Arrow ("->") means before and after the REFL centering servo (DC1 and DC2) was turned ON:

Septum cover is left OFF but the PSL light pipe was closed after this. REFL centering was turned off but I didn't bother to offload the ASC output to RM sliders.

REFL WFS nubmers as of now are not super meaningful as we'll still have to lock HAM2 down, which potentially change the relative alignment between HAM1 and HAM2. (But it's good that the beam is still hitting REFL WFSs after HAM1 was locked down even though Jim noted that the ISI position of HAM1 is not good. )

I'll open the light pipe tomorrow and quickly repeat the measurement after Jim locks down HAM2 HEPI.

Betsy, Fil, Rahul

Today we kicked started the installation activities in HAM1 chamber for the Jitter Attenuation Cavity (JAC). Given below are the things we placed on the ISI table - they are all roughly positioned and dog clamped. 

1. Tip Tilt JM1 - now connected to electronics chain, having some issues with the bosem adc counts etc, will continue looking into it.

2. Tip Tilt JM3 - now connected to the electronics chain, bosem centered, will proceed for health checks once the chassis and electronics chain looks okay.

3. The two periscopes for the JAC, Type 121 and 132 - assembly report posted by Jennie - 88574.

4. Some optics on Siskiyou mount were also added to the table.

I am attaching pictures which shows the above mentioned things added to the table - and for comparison a picture showing before any addition was (here) made.

Fil also performed group loop checks on JM1 and JM3 and did not find any issues with them.

[Jason, Betsy, Masayuki]

Two arises are installed into HAM1 chamber. They will be used as the alignment reference for new PSL modematching lens installation.

• Assembled a Thorlabs ID12 iris mounted on a 0.5-inch post with a post holder and BA2 base.
• The assembled iris was temporarily placed inside the chamber and secured with a dog clamp.
• Transitioned to laser hazard.
• Performed rough alignment using a sensor card, followed by fine alignment with an IR viewer, to center the beam through the iris.
• The beam path is offset by ~+5 mm in the +y direction from the ISI design center; this is not considered a significant issue.
• The iris location is marked with a blue circle in the attached figure.

Next step: move to the PSL and install the new mode-matching lens, likely tomorrow. This will break the IMC mode matching; IMC relocking will not be possible until the JAC installation is completed.