[Camille, Koji]

1. Flipping the OMC

It turned out that the transport fixture for this OMC could not be closed. The locks are too short, and the knobs could not be turned. We temporarily fastened the long 1/4-20 screws to secure the box and flipped it to make the top side face up.

2. Setting up the top-side template

The top side template was attached to the breadboard. We took care that the lock nuts on the positioning screws were not touched. The margins between the template and the glass edges were checked with a caliper. The long sides seemed very much parallel and symmetric, while the short sides were not symmetric. The lock nut on the short side was loosened, and the template was shifted to be symmetric w.r.t. the breadboard.

3. UV epoxy work

The cylindrical glass pieces were wiped, and the bonding surfaces were cleaned so that the visible fringes were <5 fringes. We confirmed the hooking side is properly facing up. The UV epoxy and UV curing were applied without any trouble. (Attachment 1)

4. EP30-2 bonding of the invar mounting blocks

Six invar blocks were bonded. This time the Allen key weights were properly arranged, so they didn't raise the blocks. The bond properly wetted the mating surfaces.

---

The final step of the bonding is to remove the template.
And replace the locks of the transport fixture.

[Camille, Koji]

During the second UV epoxy session, we did not bond the input beam dump. This is because this beam dump was not the one planned from the beginning and if it was bonded in place, it would have created difficulties when removing the template.

First, we aligned a couple of Allen wrenches to define the location of the beam dump. We've checked that the main transmission is not blocked at all while the stray beam from the OMC reflection is properly dumped.

After the confirmation, the UV epoxy + UV alight were applied.

The resulting position of the beam dump is shown in the attachment.

Qty1 1/2 mounts
Qty2 prism mounts
Qty6 gluing fixures
Qty1 Rotary stage
Qty1 2" AL mirror
Qty1 Base for the AL mirror

=> Handed to Stephen -> Camille on Jan 27, 2023.

[Camille, Koji] Log of the work on Dec 15, 2023

The vertical and horizontal TMSs for OMC #4 were measured with the PZT voltages scanned from 0V to 200V.

We concluded that this alignment nicely avoids the higher-order mode structure up to ~19th order. We are ready for the cavity mirror bonding.

The RF transfer functions to the trans RF PD from the modulation on the BB EOM were taken with the presence of the vertical misalignment of the incident beam and the vertical clipping of the beam on the RFPD.

The typical measurement results and the fitting results are shown in Attachments 1/2.

The TFs were taken with the voltage 0, 50, 100, 150, and 200V applied to PZT1 while PZT2 were left open. The measurement was repeated with the role of PZT1 and PZT2 swapped.

The ratio between the TMS and FSR was evaluated for each PZT voltage setting. (Attachment 3)

When the PZTs are open, the first coincident resonance is the 19th-order mode of the 45MHz lower sideband. (Attachment 4)

When the PZT2 voltage is scanned with PZT1 kept at ~0V, no low-order sidebands come into the resonance (Attachment 5) until the PZT1 voltage is above 100V.

We found that the high voltage on PZT1 misaligns the cavity in yaw and the spot (presumably) moves to an undesirable area regarding the cavity loss.
This does not happen to PZT2. Therefore the recommendation here is that the PZT2 is used as the high voltage PTZ, while PZT1 is for the low voltage actuation.

[Camille Koji]

We quickly measured the basic parameters of the OMC as is.

=== FSR ===
Used the technique to find a dip in the transmission transfer function (TF) with offset locking + phase modulation. The FSR was 264.79003MHz = The cavity length of 1.13219 [m] (requirement 1.132+/-0.005 [m])

=== TMS ===

Used the technique to find the peaks in the trans TF with phase modulation + input misalignment + trans PD clipping.
TMS_V: 58.0727 / TMS_H: 58.3070 => TMS/FSR V:0.219316 H:0.220201

This makes the 9th-order modes nicely avoided (Attachment 1). A slightly longer FSR may makes the numbers close to the nominal.

=== Spot positions ===

The image/video capture board turned out not functional with the new Apple silicon mac. We decided to use a small CCD monitor and took a photo of the display.

All the spots are within the acceptable range. The scattering on CM2 was particularly bright on the CCD image and also in the image with the IR viewr.

The spot on FM1/2 are right at the expected location. The spot on CM1 is 0.5mm low and 0.7mm inside (left). The spot on CM2 is ~0.25mm too high and 0.3mm outside.
(Attachment 2, a small grid is 1 mm/div)

== Transmission ==

We made a quick simplified measurement (Attachment 3).

Assuming the reflectivity of the matched beam to be ~0, the mode matching is M=1-(59.2e-3-(-6.5e-3))/(3.074-(-6.5e-3))=0.979
==> The power of the coupled mode is M x 21.28mW = 20.83 mW
The measued transmission was 19.88 mW
==> The OMC transmission (total) was 0.954 (4.5% loss)

This number is not too bad. But the spot on CM2 has too bright scattering. Next week, we want to check if swapping CM2 may improve the situation or not.

[Camille Koji]

We replaced CM2 with a PZT mirror subassembly serialized by PZT "13" (Attachment 1).
This made the transmission increase to 96.x%. Therefore the quick measurement of FSR and TSM were done. Also more careful measurement of the transmission was done.

Next time

== Alignment ==

• CM2 was replaced from PZT "12" to PZT "13".
• The resulting position of the cavity spot were all over 1mm too "+" (convention T1500060 Appendix C).
• So we decided to rotate CM2 by 1mrad in CW. This was done with (-) micrometer of CM2 "pushed" by 20um (2 rotational div).
• The resulting spot positions were checked with CCD. (Attachment 2). The spot positions seemed to be within +/-1mm from the center as far as we can see from the images. (good)
• CM2 spot looks much darker. CM1 spot is almost invisible with a CCD and also an IR viewer. FM1/2 spots were nominal bright level. (Looks OK)

== Quick measurement of the transmission ==

Transmission: 20.30 mW
Reflection Voltage (locked): 65.0 mV
Reflection Voltage (unlocked): 3.094 V
Reflection Voltage (dark): -6.5 mV
Incident Power: 21.64 mW

---> Mode matching 1-0.023 / Pcoupled = 21.14 / OMC Transmission 0.96

96% transmission is not the best but OK level. We decided to proceed with this mirror combination.

== Quick measurement of FSR/TMS ==

FSR: 264.7837MHz
TMS_V = 58.2105MHz
TMS_H = 58.1080MHz

The HOM structure (with PZT Vs = 0) is shown in Attachment 3. 9th order modes look just fine. The excplicit coincidence is 19th order 45MHz lower sideband. (Looks good)

== Transmission measurement ==

The raw measurements are shown in Attachment 4. The processed result is shown in Attachment 5.
We found that data set 2 has exceptionally low transmission. So we decided to run the 4th measurement excluding the set 2.

Over all OMC loss
Set1: 0.029 +/- 0.014
Set3: 0.041 +/- 0.0014
Set4: 0.038 +/- 0.001

--> 0.036 +/- 0.004
(0.964 Transmission)
 

[Camille Koji]

We started buikding the OMC #4.

• Removed OMC #1 from the optical setup and placed it at a safe side on the optical table/
• Fixed OMC #4 in the optical setup
• Cleaned the OMC cavity mirrors
• Placed the OMC cavity mirrors
  • FM1: A1
  • FM2: A3
  • CM1: PZT #11
  • CM2: PZT #12
• Aligned the beam to the cavity
• Locked the cavity on TEM00
• Finely aligned the beam to the cavity

• Cleaning is based on this: LIGO-E1200326-v2
• Your effort will look more like this:  LIGO-T1800350-v1

Another set of FC cleaning was applied to FM1/FM2/CM1/CM2 and SM2. Some FC strings are visible on SM2. So I decided to clean SM2 as well as the cavity mirrors close to SM2 (i.e. FM2 and CM2)

As a result, the bright scattering spot on CM1 is now very dim. And the loss was reduced to 4.0%. This is 0.4% better than the value before the water cleaning.

It'd be interesting to repeat the water cleaning, at least on FM1. FM1 is the closest cavity mirror to the beam dump damaged by the high-power laser pulse.
Maybe we should also clean the AR side of FM1 and BS1, as they were right next to the damaged beam dump. It is not for the loss but for reducing the scattering.

The second trial of the water scrub

A bright scatter is visible on FM1, so I tried water scrub on FM1. This time, both surfaces of FM1 and both surfaces of BS1 were cleaned.

Smaller Vectra swabs were used for the scrub. Then the water was purged by IPA splashed from a syringe. Right after that FC was applied.
This was a bit messy process as the mixture of water/IPA/FC was splattered on the breadboard.
Nevertheless, all the mess was cleaned by FC in the end.

The transmission measurements are shown in Attachment 1, and the analyzed result is shown together with the past results.

The 2nd water scrub didn't improve the transmission and it is equivalent to the one after the two times of deep cleaning.
I concluded that the water scrub didn't change the transmission much (or at all). We reached the cleaning limit.

The Windows laptop for WincamD/Beam'R2 (DELL Vostro3300) was not functional.
- Windows 7 got stuck in the starting up process (Google "startup repair loop")
- The battery can't charge and the adapter connection is flaky

I decided to newly install Win10.
I made a new bootable Win10 DVD from the ISO downloaded from IMSS. The ISO file was converted to CDR using Disk Utility on Mac.
This deleted the past disk partitions. The installation process has no trouble and Win10 ran successfully. The machine is slow but still acceptable for our purpose.
Dataray Version 7.1H25Bk was downloaded from the vendor website https://dataray.com/blogs/software/downloads and installed successfully.
The devices ran as expected by connecting the heads and selecting the proper device in the software.

Then, the Win10 fell into "Hibernation Loop" and "Shutdown loop" (after disabling hibernation in the safe mode).
This is probably the combination of extremely slow windows update (feature update i.e. beta OS update) and the occasional shutdown due to the flakiness of the AC connection

Win10 was reinstalled and automatic Win update was disabled via windows policy manager or something like that. Still, it tries to download and update some of the updates (what's happening there!?

Here are my strong recommendations on how to use this laptop

• Do not use any network connection. It will enable Windows Update kicks in and destroy the machine.
• Use a USB stick for data transportation if necessary
• The laptop should always be connected to the power supply at a stable location. (The adapter connection is flaky and the battery is dead)
• Buy a replacement battery (maybe a 3rd-party cheap one
• The Win10 DVD should always be inserted into the laptop's drive so that we can reinstall the windows anytime.

Aaron took the set to Cryo lab

The four cavity mirrors in OMC #1 were each scrubbed using acetone and a cotton swab.
Then, the four mirrors were painted with First Contact (picture attached). The First Contact was allowed to dry for 20 minutes, then removed while using the top gun.

OMC Transmission measurement after the 2nd deep cleaning

The 2nd deep cleaning didn't improve the transmission. (See Attachment 2)
The measured loss was 0.044+/-0.002

Conclusion on the cleaning of OMC #001

- After a couple of first contact cleaning trials and deep cleaning, the total loss was measured to be 0.045+/-0.004.
  This indicated a slight improvement from the loss measured at LLO before any cleaning (0.064+/-0.004).
  However, the number did not improve to the level we marked in 2013 (0.028+/-0.004).

- This loss level of 4.5% is comparable to the loss level of OMC #3, which is currently used at LHO.
  Therefore, this OMC #1 is still a useful spare for the site use.

- Some notes / to-do regarding this unit:
  1) The beam dump with melted black glass was removed. A new beam dump needs to be bonded on the base.
  2) The connector bracket still needs to be replaced with the PEEK version.
  3) The PZT of CM1 has been defunct since 2013. Combining LV and HV drivers is necessary upon use at the site. (LLO used to do it).

[Camille, Koji]

- Removed the first contact we left on Monday.

- Measured transmission (Set1) Very high loss! Total optical loss of 18.5%! Observation with the IR viewer indicated that CM1 has bright scattering. We suspencted a remnant of FC.

- Applied the second FC on the four cavity mirrors. This made the CM1 sport darker.

- Measured the transmission (Set1~Set3). We had consistent loss of 4.2~5.0%. We concluded that this is the limitation of this OMC even with the cleaning.

[Camille, Koji]

Friday, Nov 11th, 2022

Setting up OMC #1 for transmission measurements:

The laser beam was aligned to the OMC cavity. The OMC cavity was locked and the transmission measurements were recorded.

The measured total optical loss of the OMC was

1st:   0.015 +/- 0.003
2nd: 0.085  +/- 0.005
3rd:  0.0585+/- 0.0008
4th:  0.047  +/- 0.002

In avegrage the estimated loss is
Loss = 0.055 +/- 0.014

This is unchanged from the measurement at LLO after the FC cleaning
Loss = 0.053 +/- 0.010

Clean Supply Ordered

• TexWipe TX8410 AlphaSat Vectra Alpha 10 50 sheets x 12 pk  (VWR TWTX8410)
• Mask KIMTECH PURE® M3 Pleat-Style Face Masks 50 masks x 10 pk (VWR 15628-213)
• Stainless Pan x3 (VWR 10193-562)
• Ansell Accutech Latex Gloves 6.5 25*8pk (Fisher 19162026)
• Ansell Accutech Latex Gloves 7.0 25*8pk (Fisher 19162027)

[Camille, Koji]

Began setting up fiber assembly for OMC testing:
-Aligned fiber mount to maximize transmission through fiber
-Adjusted polarization at output of fiber to minimize s-polarized output.

Power measurements:
fiber input: 56.7 mW
fiber output:43.2 mW
s-polarized output: 700 uW

Fiber matching: 43.2/56.7 = 76%
S/P-pol ratio 0.7/43.2 = 1.6%

OMC #001

• ICS Link: https://ics.ligo-la.caltech.edu/JIRA/browse/ASSY-D1201439-1
• Already marked as disassembled
• Removed two PDs
  • https://ics.ligo-la.caltech.edu/JIRA/browse/IHGQEX3000-0-00-A1-25
  • https://ics.ligo-la.caltech.edu/JIRA/browse/IHGQEX3000-0-00-A1-23
• Shipped to CIT
  • https://ics.ligo-la.caltech.edu/JIRA/browse/Shipment-12455

OMC #002

• ICS Link: https://ics.ligo-la.caltech.edu/JIRA/browse/ASSY-D1201439-002
• Disassemble to remove "assembled" mark
• Removed two Excelitas PDs
• Added IHGQEX3000-0-00-A1-23 and IHGQEX3000-0-00-A1-25
• Removed the cable connector bracket
• Added the new PEEK connector bracket 
  (This part was just "shipped" from CIT to LLO in ICS: https://ics.ligo-la.caltech.edu/JIRA/browse/Shipment-12458)
  https://ics.ligo-la.caltech.edu/JIRA/browse/D1300052-V3-00-0001
• Marked "Assembled"
• Stored: https://ics.ligo-la.caltech.edu/JIRA/browse/Storage-12456

Upon the LLO work, the current PD arrangement in the cages are:
CAGE B
B1 OMC1 PDT (A1-23)
B2 OMC1 PDR (A1-25)
B3 original (C1-03)
B4 OMC2 PDT (B1-22)

CAGE C
C1 OMC2 PDR (B1-23)
C2 original (C1-08)
C3 original (C1-09)
C4 original (C1-10)

== Initial Preparation ==

• [Done] OMC #002 placement
• [Done] OMC #002 locking
• Details OMC ELOG 414

== Measurements ==

• [Done] Transmission / Power budget before FirstContact OMC ELOG 416
• [Done] Transmission / Power budget after FirstContact OMC ELOG 417
• [Done] Backscatter measurement with a new deflection optics
  • [Done] Optics bonding done waiting for cure OMC ELOG 420 -> Returned the bond to Madeline OMC ELOG 424
  • [Done] Backscatter measurement
    • Measurement: 0.6 ppm OMC ELOG 422
    • (Transmission is 10~60mW. If the backscatter is the order of 1ppm or less, we expect the light level is ~10nW. Can we really detect it? How? ... OK... last time the measurement has been done with the stick PD type powermeter with baffles and the room light turned off (OMC ELOG 209). So it's not totally crazy.)
• [Done] High QE PD preparation / install / QE check
  • [Done] High QE PD inventory check
    • A1-23    LLO OMC#001
    • A1-25    LLO OMC#001
    • B1-01    LHO OMC#003
    • B1-16    LHO OMC#003
    • B1-22    @CIT Cage B1 Cleaned/Installed
    • B1-23    @CIT Cage B2 Cleaned/Installed
    • C1-03    @CIT Cage B3 Cleaned
    • C1-05    Dead / CIT contamination test cav
    • C1-07    Dead / CIT contamination test cav
    • C1-08    @CIT Cage C2
    • C1-09    @CIT Cage C3
    • C1-10    @CIT Cage C4
    • C1-11    @CIT Cage D1
    • C1-12    @CIT Cage D2
    • C1-14    @CIT Cage D3
    • C1-15    Dead / CIT Cage D4
    • C1-17    LHO Spare
    • C1-21    LHO Spare
    • D1-08    not @CIT, maybe LLO Spare?
    • D1-10    not @CIT, maybe LLO Spare?
  • [Done] Install & QE check
    • 1st attempt OMC ELOG 427
    • 2nd attempt OMC ELOG 429
• [Done] Fiber input beam characterization OMC ELOG 421

== Repair / Preparation ==

• [Done] Obtain: UHV Foil (done) / EP30 (found at the 40m OMC ELOG 434) / EP30-2 bonding setup OMC ELOG 442
• [Done] Crimper tool? LLO bought a new one and modify it.
• [Done] BeCu wire clamps:
  • [Done] Sufficient # of clamps found:OMC ELOG 428 / C&Bed
• [Done] FirstContact cavity mirror cleaning (see OMC ELOG 414)
• [Done] FirstContact for protection OMC ELOG 430
   
• Beam dump cleaning -> not necessary
   
• [Done] Replacing the cable bracket
  • [Done] Obtain all parts from Stephen.
  • [Done] Class B Torque wrench present in the lab
  • [Done] Replacement work
    • Recorded the original connections and the cable routing OMC ELOG 431
    • Unmounting the cable bracket OMC ELOG 432
    • Spare situation check OMC ELOG 433
    • Cable bracket replacement OMC ELOG 436
    • New cable tie installed OMC ELOG 437
• [Done] Delamination Repair
  • Delamination status OMC ELOG 414
  • More delamination check OMC ELOG 426
  • Reinforcement parts Inventory OMC ELOG 419
  • Cleaning of the reinforcement bars / Asking Madeline for C&B OMC ELOG 424
  • Delamination of the black glass pieces observed -> reinforcement required OMC ELOG 431
  • Delamination repair part1 OMC ELOG 438  OMC ELOG 439 OMC ELOG 440
  • Delamination repair part2 OMC ELOG 441 OMC ELOG 443 OMC ELOG 444 
• [Done] Check all the fasteners / Ready for the shipment OMC ELOG 445
• Check addon mass configuration OMC ELOG 446  OMC ELOG 447

== Shipping ==

• [Done] Tools to ship to LLO OMC ELOG 448
  • CLASS B special tool kit (Allens / Pliers / Mighty-Mouse spanner / Spatula / etc)
  • FC kit
  • Electronic kit (PD connector / trans-impedance amp)
  • Spare High QE PDs
  • Power meters
  • Glass Beamdumps (for optical testing)
  • Cable bracket replacement kit (PEEK cable bracket / cable pegs / fastners / spare fasteners / kapton sheet / cable ties)
  • Emergency EP30-2 kit (excluding the bond)
     
• [Done] OMC Pelican Filling (Stephen) / OMC Outerbox/insulation (Stephen/Downs) / OMC Shipment Aug 29, 2022 OMC ELOG 445

o Power Budget (2022/07/18)
NPRO ADJ -50 (min)
Fiber incident 62.8mW
Fiber output 45.1mW
Matching to the fiber 72%

DCPD T =  8.90  +/- 0.01  mW
REFPD  =  3.760  +/- 0.001 V

DCPD R =  8.82  +/- 0.01  V
REFPD  =  3.760 +/- 0.001 V

CM1    =  81.4  +/- 0.1   uW
REFPD  =  3.767 +/- 0.001 V

CM2    =  86.6  +/- 0.1   uW
REFPD  =  3.767 +/- 0.001 V

REFLPD
OFS    = -6.214 +/- 0.001 mV (beam blocked)
OFS_REF= +4.587mV

LOCKED =  57.5  +/- 0.5   mV
REFPD  =  3.970 +/- 0.003 V

UNLOCK =  2.816 +/- 0.003 V
REFPD  =  3.943 +/- 0.001 V

P_Inc  =  20.04 +/- 0.01  mW
REFPD  =  3.946 +/- 0.001 V
 

Analysis Result

- Cavity coupling 0.989 (1.1% junk&sidebands)

- Cavity R&T: R=756ppm, T=0.946
- OMC Throughput (Cavity T x First BS R): T=0.939
- Cavity loss per mirror 90 ppm / Round Trip Loss 432ppm

o Power Budget after FirstContact cleaning (2022/07/20)
NPRO ADJ -50 (min)
Fiber incident --.-mW
Fiber output --.-mW
Matching to the fiber ??%

DCPD T =  8.62  +/- 0.01  mW
REFPD  =  3.549  +/- 0.001 V

DCPD R =  9.46  +/- 0.01  V
REFPD  =  3.562 +/- 0.001 V

CM1    =  74.5  +/- 0.1   uW
REFPD  =  3.585 +/- 0.001 V

CM2    =  81.7  +/- 0.1   uW
REFPD  =  3.585 +/- 0.001 V

REFLPD
vOFS    = -6.197 +/- 0.001 mV (beam blocked)
vOFS_REF= +4.58mV

LOCKED =  47.6  +/- 0.2   mV
REFPD  =  3.596 +/- 0.003 V

UNLOCK =  2.700 +/- 0.003 V
REFPD  =  3.590 +/- 0.001 V

P_Inc  =  19.36 +/- 0.001  mW
REFPD  =  3.594 +/- 0.001 V

Analysis Result

- Cavity coupling 0.980 (2.0% junk&sidebands)

- Cavity R&T: R=229ppm, T=0.970 (previous T=0.946, 2.4% UP!)
- OMC Throughput (Cavity T x First BS R): T=0.963
- Cavity loss per mirror 42.8 ppm / Round Trip Loss 238ppm

Bond reinforcement blocks for the invar brackets:

• Attachment 1: CLASS A glass prisms (the surplus of the 2016 repair)
• Attachment 2: Dirty reiforcement bars made of Aluminum
• There are also many dirty prisms in the kit obtained from Stephen

The backscatter beam is supposed to appear in the backpropagation path. The transmission of the OMC has a couple of optics, it's not easy to access that beam.
To try to deflect the beam either horizontally or vertically, small optical pieces were made. (Attachment)

These are the combination of the optics

- Thorlabs PF05-03 Fused Silica Mirror Blank (dia12.7mm x t 6.0mm) + Thorlabs 1/2"sq BB Dielectric Mirror BBSQ05-E03

- Thorlabs PF05-03 Fused Silica Mirror Blank (dia12.7mm x t 6.0mm) + Thorlabs ME05-G01 Protected Al Mirror (dia12.7mm x t 3.2mm) + Thorlabs MRA10-K13 Right-Angle Prism Nd:YAG 10mm

Torr seal was used as the bonding epoxy. It uses a 1:2 volume mixture (not easy because of the viscosity) and is relatively fast to cure (in a couple of hours).
The test piece showed some softness after 3~4 hours so I left the parts cured overnight at room temp (i.e. 18degC)

The profile of the beam incident on the fiber input

The fiber input was deflected by a 45deg mirror. The beam profile was measured with WincamD. The beam was too strong (~60mW) even at the smallest pump power (ADJ -50) of the NPRO. So the two ND20 filters were added to the lens right before the 45 deg mirror and the camera.

The measured profile had some deviation from the nice TEM00 particularly around the waist. This could be a problem of the too small beam on the ND filter and the CCD.
This is not an issue as we just want to know the approximate shape of the beam.

For the fiber coupling, if we have the beam waist radius of ~200um it is sufficient for decent coupling.

Measure the power ratio between the forward-propagating and reverse-propagating beams.

1. Place a small deflecting mirror at the transmission.
2. Place a flat mirror at the deflected transmission. When the alignment of this mirror is adjusted to retroreflect this beam, the DC of the cavity reflection PD increases, and also the CCD shows spurious fringes.
3. This condition allows us to locate the power meter at the reverse-propagating spot of the transmission (Attachment 1)
4. Place a black glass beam dump for the main (bright) transmission (Attachment 2)
5. Now the power meter is receiving the counter-propagating beam. Turn off the room light and place an anodized Al baffle as shown in Attachment 2. Move the baffle to block only the counter-propagating. Move the baffle out. => Record the power meter reading with/without the baffle in the counter-propagating path. The difference is the power of the reverse-propagating beam.
6. Now measure the power of the reflected main transmission. This tells us the power ratio between the foward- and back-propagating beams.
7. Remove the small deflecting mirror and measure the power of the main transmission.
8. Now the back-propagating power can be estimated from 6 and 7. The same amount is going back to the IFO path.
9. The reflectivity can be calculated from the 7 and the transmission

- To increase the incident laser power, NPRO Current ADJ was set to be 0 (increased from -50)

- 1st:  Without the baffle 0.373 +/- 0.001 uW / With the baffle 0.318 +/- 0.001 uW
- 2nd: Without the baffle 0.370 +/- 0.001 uW / With the baffle 0.318 +/- 0.001 uW
- 3rd: Without the baffle 0.370 +/- 0.001 uW / With the baffle 0.317 +/- 0.001 uW

==> 53.3 +/- 0.6 nW

- The main transmission was 84.0mW
==> Backpropagation ratio was 0.634+/-0.007 ppm

- Direct measurement of the OMC was  after BS 96.6mW
==> Backpropagation power from the cavity: 61.3 +/- 0.7 nW

- Cavity transmission for the matched beam is Tcav RinputBS = 0.963
==> Incident resonant TEM00 power 100.3mW

- Reflection 61.3+/-0.7 nW x RinputBS = 60.8+/-0.7 nW
-> The effective reflectivity for the mode-matched resonant TEM00 beam incident on the OMC (1st steering mirror) is 0.606+/-0.007 ppm

OMC Reinforcement blocks

1. P/N D1600316; Version v4; Type 01; Qty 30; Source Chemistry Machine Shop
2. P/N D1600316; Version v4; Type 02; Qty 15; Source Chemistry Machine Shop
3. P/N D1600316; Version v4; Type 01; Qty 40; Source Resource MFG PO S422806
4. P/N D1600316; Version v4; Type 02; Qty 40; Source Resource MFG PO S422806

Stephen asked Srinath for the ICS entry.
Stephen made the C&B request https://cleanandbake.ligo.caltech.edu/clean_and_bake/request/1708/

Madeline was asked to take care of the C&B.

Also, the Torr Seal box was returned to Madeline.

- Installed the High QE PDs to OMC #002

• B1-22@Cage B1 was installed to the transmission DCPD
• B1-23@Cage B1 was installed to the reflection DCPD

Upon the installation, the legs of the PDs were cut by 3mm. Also, the tab of the PD could not be embedded in the DCPD housing. Therefore, the tabs were cut.

The alignment looked just fine. The weak reflections are directed to the black glass beam dumps.

- After the installation, the QEs were measured.

• With Thorlabs S130C power meter, the QE was estimated to be ~95%. (Accuracy +/-7%)
• With Thorlabs S401C power meter, the QE was estimated to be ~100%. (Accuracy +/-3%)

It is so confusing. So I decided to make the QE test setup.

Ophir RM9 with chopper (+/-5%): 8.97mW
Thorlabs S140C integrating sphere (+/-7%): 9.11mW
Thorlabs S130C PD power meter (+/-7%): 9.15mW
Thorlabs S401C thermal power meter (+/-3%): 8.90mW
So there looks ~3% discrepancy between S130C and S401C

Then tried to measure the QE of C1-03@Cage B3 with Ophir RM9
- Initial state: QE=0.95
- First FirstContact application: QE went up to 0.973
- Second FirstContact application: QE = 0.974, basically no change

To Do:
- Calibrate the trans-impedance amp with Keithley
- Apply FC to B1-22 and B1-23 to see if there is an improvement
- The power should be measured with S401C because the accuracy seems better (+/-3%).
- Take photos of the PD FC process

General To Do:

- Backscatter test 2nd trial

- Start applying the first contact to the optical surfaces
- Beam dump cleaning
- Apply FC cap to the PDs
- Delamination repair (light side)
- Delamination repair (dark side)
- Cable bracket replace (dark side)
 

- DLPCA-200 trans-impedance amplifier was calibrated.
  Keithley source meter 2450 was connected to the amp. Provide current and read the output voltage with the precision digital voltage meter (Agilent/Keysight).
  Gain: 999.7V/A@7mA, 999.6V/A@8mA

- From the power meter spec, Thorlabs S401C seemed the best (+/-3%). So the QEs of the 9 PDs were checked with this power meter again.

- All PDs exhibited the QE of 0.95~0.96. It's all relative as the power meter has a systematic error.
- Tried to clean B1-22 and B1-23 PDs. They didn't show significant improvement after the cleaning. To avoid the unnecessary risk of damaging the PDs, further cleaning was not performed. (Some photos were attached)

- What we can do is use this result as the relative measurements.
- For OMC#2, B1-22 is the DCPD(T) and B1-23 is the DCPD(R). C1-03 and C1-12 are the spares, according to this latest result.
- At LLO, we track down the source of the throughput reduction (-10%). The QEs of the PDs are going to be tested in the same setup at once to compare their PDs and our PDs.

Regarding: D1200971

- 4 CLASS A wire clamp obtained from the OMC spare
- 4 more DIRTY wire clamp obtained from WB experiments (they no longer use these)

Once the later ones are C&Bed, we have enough.

The optical surfaces were coated with FirstContact to keep them clean / somewhat protected during the transportation.
The PD aperture was sealed with FirstContact "caps" (made by Kate in 2016?).

Parts check

- D1300052-V3 SN001 is going to be used (Attachment 1)

- This is the PEEK version of the cable bracket (Attachment 2). The side thread holes have no Helicoils inserted. This needs to be done!
 

Connector arrangement check / cable routing check

Attachment 3: Connector Arrangement from the Northside

Attachment 4: Connector Arrangement from the South side

Attachment 5: Cable routing (Northside down)

At this point, the delamination of the V shape beam dumps was visible. This is the subject of bonding reinforcement.

Connector unmounting

- (Attachment 1) The connector nut rings were removed using an angled needle nose plier. The connector shell has a tight dimension relative to the hole on the bracket. But of course, they could be extracted.

- The 4 screws mounting the bracket to the invar blocks were successfully removed. No extra damage to the bonding.

- (Attachment 2) The plan was to remove the cable pegs by unfastening the button head 1/4-20 screws from the bracket and then just replace the bracket with the new one. However, these screws were really tight. The two were successfully removed without cutting the PEEK cable ties. Two cable ties were necessary to be cut to detach the bracket+pegs from the fragile OMC. Then one screw was removed. However, the final one could not be unfastened. This is not a problem as we are not going to recycle the metal cable bracket... as long as we have spare parts for the new bracket.

- (Attachment 3) Right now, the new bracket is waiting for the helicoils to be inserted. So the OMC lid was closed with the cables piled up. Just be careful when the lid is open.

Checking the spare parts

- Conclusion for OMC#2: need PEEK cable ties
- for more OMCs: need more BHCS / PEEK cable ties / Helicoils

• Helicoils: 1/4-20 0.375 helicoils / Qty 4 / Class A (Attachment 1)
  • looks like there are many more as the transport fixture bags (Attachment 2). Stephen noted that they are meant to be CLASS B
     
• Cable pegs: D1300057 / Qty 24 + 3 recycled from OMC#2 / Class A (Attachment 3)
  • Requirement: 3+3+4 = 10 for the 4th OMC / 3x4 =12 for the cable bracket replacement -> we have enough
     
• PEEK Cable Ties: Stephen reported they were deformed by baking heat... did not check how they are in the bags.
   
• Button Head Cap Screws 1/4-20 length ? none found in the bags.
  • Qty 4 spare (forgot to take a picture) + 3 recycled. So we have sufficient for OMC#2

[Stephen Koji]

Now we got the C&Bed parts to continue to work on the cable bracket replacement.

1) Helicoil insertion

1/4-20 Helicoils were inserted into the 6 thread holes of D1300052. It went mostly okay. We witnessed that the Helicoil insertion tool delaminated the plating of the Helicoils upon insertion (Attachment 1). Stephen mentioned that this is not usual, but we didn't find anything further such as increased friction, more debris, etc. So we decided to go forward.

2) EP30-2 Kit

The EP30-2 kit was transferred from the 40m clean room to the OMC lab. The EP30-2 kit tracking was updated via C1900343

3) D1300052 reinstallation -> FAIL

Now resumed to the installation of D1300052 bracket. However, the hole size of the bracket is just a bit too small compared with the size of the mighty mouse connectors. It was already quite tight with the metal version. However, this PEEK version seems to have 0.1 mm further small diameter, and then the connectors do not penetrate the holes. The plan could be
1) Use a razor blade to shave the hole inner circle.
2) Use a cleaned drill bit to make the hole size 0.2mm bigger.

- The hole size extension is going forwared now.

- Madeline and Chub are cleaning (sonicating) a drill (29/64=0.4531")
- The parts in a bag were brought to the 40m C&B lab.

- The hole is going to be 11mil=0.28mm larger than the recommendation (0.442").
  It's not a D-hole. The connector has a rounded-rectangular flange that fits into the PEEK parts.
  So I don't think it's an issue.

- Chub has a proper spanner to fasten the nuts. We want to use it here and LLO.

The cable bracket was successfully replaced.

• Looking from the QPD side (North side in Attachment 1), the connectors for the DCPDs and PZT are sticking out, and the ones for QPDs are sticking to the other side. So only two rectangular holes (for QPDs) are facing north.
  • Top left is DCPDT
  • Top right is DCPDR
  • Bottom center is PZT
  • Bottom left is QPD (far/long)
  • Bottom right is QPD (near/short)
     
• First, the cable pegs for the short sides are fastened with the original screws (Vented BHCS 1/4-20).
• Then, the cables are started to be inserted from the bottom so that the nuts can be rotated with the spanner. The spanner helped a bit but the nut only has two positions to hook the spanner and the clearance is not sufficient to insert the spanner when one of the hook positions is facing the bottom. The enlarged hole (29/64") perfectly worked . The flange of the connector can be held with a rectangular hole, so a bit bigger hole than the connector size was not an issue. Finally, all the cables were attached to the bracket.
• The bracket has not yet been fixed on the OMC breadboard yet. This was done with the four screws from the top. Along with the assembly document E1300201, the fastening torque was limited to 2 in-lb using a digital torque wrench.
• Attachment 2 shows the view from the "North" side. Attachment 3 shows the view from the "South" side. The cables were not yet tied on the cable pegs on the long side of the bracket.

[Stephen Koji]

New cable ties were installed on the cable pegs attached to the long sides of the cable bracket.

[Stephen Koji]

Checked the delamination status:

• The Invar bar on the cable bracket (DCPD side): Almost all delaminated (Attachment 1 left)
• The invar bar on the cable bracket (QPD side): Rims still intact, center delaminated (Attachment 1 right)
• The invar bar reinforced in 2016: One of the reinforcement bar half delaminated (Attachment 2)

EP30-2 preparation

• Two Al foil cups + A sheet of Al foil (for test cure)
• Set a tube on the glue gun
• Attach an applicator tube
• Push a couple of times, and dispense the glue for a single stroke on a waste Al cup
• Pour the 6g of glue to the other cup.
• Add 0.3g of silica beads powder to the cup
• Steer. Pick a few drops to the test cure Al foil
• Bake the test piece for 15min in 200F (95degC) ==> Very good

#1 The Invar bar on the cable bracket (DCPD side)

Added short (frosted) Al bars (Attachment 1) to the short sides of the invar bar. (Attachments 2/3). Some glue was sucked into the delamination gap by capillary action (=good) (Attachment 4)

#2 The Invar bar on the cable bracket (QPD side)

Added short (frosted) Al bars to the short sides of the invar bar. (Attachments 3/5). Maybe some glue was sucked into the delamination gap??? Not so clear. (Attachment 4)

#3 The Invar bar reinforced in 2016

Added a short (frosted) Al bars to a short side of the invar bar (Attachment 6). On both sides of the 2016 reinforcement, rectangular prisms are added (Attachment 6)
Some capillary action is visible beneath the invar bar (Attachment 7)

Leave it as it is for a day

Inspection of the bonding on the suspension interface side. All look good.

Inspection of the delaminations in the optics side

Bonding

Inspection

EP30-2 bonding setup

[Stephen Koji]

The OMC #002 is ready for shipment.

Attachment 1: Work done on Sept 19, 2022

Other attachments: Putting the OMC in the pelican case.

Inspected the past LLO add-on mass configuration.

There are unknown masses at the DCPD side. It looks like a small SS mass with an estimated mass of 5g. But the DCC number is unknown.

We are going to add 10g on each corner as well as the damping aterial. We should be able to figure out the fastener / mass configuration.

Here is the balance mass info for the LLO OMC#001 analyzed from the photographs

• Added masses are: 50+10g, 50+20, 10+20+5, and 20+20+10 for the mass right above FM1/CM1/FM2 and CM2, respectively.
• The length of the 1/4-20 screws seem L=3/4"~1"

If we attach the additional mass, longer 1/4-20 screws (1", 1" 1/8, 1" 1/4) are going to be used.

Shipping preparation for the LLO trip

Started July 15, 2022 and finished Aug 30. So it took ~1.5 months (with a couple weeks of break)

Class B special tools

• Screw Drivers 1
  • https://www.steritool.com/
  • https://www.steritool.com/precision-screwdrivers-mini.aspx
• Screw Drivers 2
  • What I have seems S555Z-7
  • https://www.starrett.com/
  • https://www.starrett.com/dms/flipbooks/Cat-33/index.html?page=354
• Allen Wrenches
  • Bondhus: These are not made of SS, but of so called protanium steel. I have a chrome finish one (BriteGuard) and K14 gold finish one (goldguard).
  • https://intl.bondhus.com/pages/goldguard-ball-end
  • https://intl.bondhus.com/pages/briteguard-ball-end
• Scissors
  • VWR - Stainless Steel
  • Unknown PN /  probably this?
  • https://us.vwr.com/store/product/4527635/vwr-dissecting-scissors-sharp-blunt-tip
• Forceps
  • VWR - Stainless Steel
  • https://us.vwr.com/store/product/4531765/vwr-hemostatic-forceps
• Wire cutters
  • Looks like they are orthodontic wire cutters. One has the marking "Orthomechanic Stainless Steel" but the company does not sell cutters anymore. The other has a marking "333" but the company is unknown. Similar products can be found on Amazon
• Long nose pliers - straight stainless steel
  • https://www.aventools.com/
  • https://www.aventools.com/long-nose-pliers-stainless-steel-6-2
• Bent nose pliers - stainless steel
  • unknown 
• Tweezers
  • Excelta 
  • The short one is 20A-S-SE. The longer one is 24-SA-PI, maybe?
  • https://www.excelta.com/
  • https://www.excelta.com/straight-laboratory-instruments-forceps
  • https://www.excelta.com/style-24-24-6-sa
• Mighty-Mouse spanner
• 2x driver bits for the digital torque wrench

First Contact Kit

• FC bottole / PEEK mesh

Bonding kit (excl EP30-2 bond)

• reinforcement bars (4 types)
• bonding liner powder
• tools: spatula / bond applying rod

Power meters (excl Power meter controller)

• Thorlabs Thermal
• Thorlabs Photodiode
• Thorlabs Integrating Sphere

Electronics

• preamp + power cable
• PD testing kit (PD connector / DB9 break out / grabber-BNC)
• Nitrile gloves

Cable bracket replacement kit

• PEEK cable bracket (Helicoiled)
• Cable pegs (x4 salvaged / spare)
• fastners
• kapton sheet
• cable ties

Optics / Optomechanics

• Optical fiber / spare fiber
• OMC transport feet
• OMC backscatter inspection prisms

Misc tools

• digital torque wrench

=== Action done on Aug 30 ===

Fiber MM setup / Fiber coupler mount
Glass Beamdumps (for optical testing)
Flipper mirror
Thorlabs fiber coupler tool
General bent nose plier for fiber
Thorlabs collimator tiny allen
Spare High QE PDs

Spare OMC bags / Zip bags

Balance Mass 10g Qty 8 (Different Type D11*** 1.25" dia), 20g Qty 10 / Mass damper D1700301 -04 / Mass damper screws SHCS 1/4-20 x 1.25 Qty 25 / 1" screws and 1 1/8" screws

Shipping request: https://services1.ligo-la.caltech.edu/FRS/show_bug.cgi?id=25002

=== Low supply! ===

• Masks
• 7.0 gloves supply low
• 7.5 glove completely gone
• Wet vectra cloth
• Dry vectra cloth

- The lab is chilly (18degC)

- Cleaned the lab and the optical table a bit so that the delicate work can be done. The diode test rig (borrowed from Downs - see OMC ELOG 408 and OMC ELOG 409) was removed from the table and brought to the office (to return on Monday)

- The rack electronics were energized.

- The OMC mirrors in use were returned to the cases and stored in the plastic box.

- The optical table was also cleaned. Removed the old Al foils. The table was wiped with IPA

- The OMC #4 was moved to the other part of the table, and then OMC #2 was placed in the nominal place (Attachment 1). Note that the "legs" were migrated from #4 to #2. There are three poles that defines the location of the OMC Transportation

- The lid was removed and the OMC was inspected (Attachment 2). Immediately found some more delamination of the epoxy beneath the cable bracket (Attachment 3). This needs to be taken care of before shipment.

- The cavity was already flashing as usual, and a bit of alignment made the TEM00 flashing.

- The locking was a little tricky because the LB unit seemed to have a gain-dependent offset. After some adjustment, robust locks were achieved. The cavity was then finely adjusted. Attachment 4 shows the CCD image of the reflection. The core of the spot is more or less axisymmetric as usual. There is also a large helo around the spot. I was not aware of this before. I may need to wipe some of the mirrors of the input path.

- As the satisfactory lock was achieved, I called a day by taking a picture of the table (Attachment 5).

More epoxy delamination check:

DCPD R (Attachment 1): Found half delaminated

DCPD T (Attachment 2): Found half delaminated

QPD1/QPD2 (Attachment 3): Looks fine

------

In total we need to fix bonding of three invar bases (including the one for the cable bracket)

Item loan: SRS LCR meter SRS720 borrowed from Downs. The unit is at the 40m right now for testing with an excelitas PD. Once it is done, the setup will be moved to the OMC lab for testing the high QE PDs

Attachment 1: System diagram. The reverse bias voltage is controlled by DS335. This can produce a voltage offset up to 10V. A G=+2 opamp circuit was inserted so that a bias of up to +15V can be produced. The capacitances of the photodiodes were measured with SR720 LCR meter with a probe. DS335 and SR720 were controlled from PC/Mac via serial connections.

Attachment 2: Overview

Attachment 3: How was the probe attached to the photodiode under the test

Attachment 4: The bias circuitry and the power supply

Attachment 5: G=+2 amp

Measurement result:

The capacitance at no bias was 460~500pF. This goes down to below 300pF at 1.0~1.5V reverse bias. At maximum +15V, the capacitance goes down to 200~220pF.

On this opportunity, the capacitances of a couple of Excelitas C30665 photodiodes were measured. In Attachment 2, the result was compared with one of the results from the high QE PDs. In general the capacitance of C30665 is lower than the one from the high QE PDs.

SRS LCR meter SRS720 was returned to Downs as before.

The table width was an inch too large compared to the door width. We need to tilt the table and it seemed too much for us. Let's ask the transportation for handling.

Photo courtesy by Juan

I've cleared the small optical table and wondered how to move it out of the room. Fortunately, the north side of the big table had wide enough clearance and let the 36" wide table go through. This was easy without moving other heavy stuff.

From here to the door, a bit of work is required. A possibility is to roll the laser blocking wall to the south side of the big table. This will require moving the shelving in the entrance area but it's not a lot of work compared to disassembling a part of the wall.

If this does not work somehow, we will consider removing the last panel of the wall and it will definitely allow the table to get out from the door.

OMC Unit 4 Build Machined Parts are currently located in Stephen's office. See image of large blue box from office, below.

Loaned item D1100855-V1-00-OMC08Q004 to Don Griffith for work in semi-clean HDS assy.

This includes mass mounting brackets, cable brackets, balance masses, etc. For full inventory, refer to ICS load Bake-9527 (mixed polymers) and Bake-9495 (mixed metals).

Inventory includes all items except cables. Plasma sprayed components with slight chipping were deemed acceptable for Unit 4 use. Cable components (including flex circuit) are ready to advance to fabrication, with a bit more planning and ID of appropriate wiring.

More explicit insights into the inventory for the Unit 4 build. Image of inventory included below.

Machined Parts:

• New fabrication = Contents of Storage-11112 are consistent with upgrade ECR.
• Old leftovers = Storage-9482 and Storage-9483 .

Cable Components:

• Hughes Circuits made us Kapton flex circuits. These have not been processed in any way.
• Rich had supplied a spool of Gore 4-conductor in-vacuum wire (see below image). I returned the sppol for Rich but it is living in Downs and available for use.
• PEEK cable ties were damaged during bake, and will be replaced by SYS inventory.

Retrofit/Repair Capabilities:

• Aluminum reinforcement brackets D1600316
• Glass reinforcement brackets (Edmund Optics 45-072 and 45-071)

ref: E1900034 and other associated documents.

Dark current measurement for InGaAs QPDs (OSI FCI-InGaAs-Q3000) has been done using Keithley 2450 and Frank's diode test kit. Frank's setup uses various custom instruments which are no longer exist, therefore the kit was used only for switching between the segments.

The diodes were serialized as 81, 82, 83, 84, continuing the numbering for the OMC QPDs. The numbers are engraved at the side and the back of the diode cans.

Overall, the QPDs nominally indicated the usual dark current level of <10nA.
SEG1 of #82 showed a lower voltage of reverse breakdown but this is not a critical level.
#83 showed variations between the segments compared to the uniform characteristics of #81 and #84.

To know any anomaly to the junction capacitance of the QPD segments, the RF impedances were tested with a hand-made impedance measurement.
All segments look almost identical in terms of capacitance.

Measurement setup:
The impedance of a device can be measured, for example, from the complex reflection coefficient (S11). To measure the reflection, a bidirectional coupler was brought from the 40m. Attachments 1 and 2 shows the connection. The quantity A/R shows S11. The network analyzer can convert a raw transfer function to an impedance in Ohm.

Calibration and Measurement limit:
The network analyzer was calibrated with 1) a piece of wire to short the clips 2) 50ohm resistor 3) open clips. Then the setup was tested with these three conditions (again). Attachment 3 shows the result. Because of the impedance variation of the system (mainly from the Pomona clip, I guess), there looks the systematic measurement error of ~1pF or ~25nH. Above 100MHz, the effect of the stray impedance is large such that the measurement is not reliable.

The setup was tested with a 10pF ceramic capacitor and this indicated it is accurate at this level. The setup is sufficient for measuring the diode junction capacitance of 300~500pF.

Impedance of the QPD segments:

Then the impedances of the QPD segments were measured (Attachment 4). The segments showed the identical capacitance of 300~400pF level, except for the variation of the stray inductance at high freq, which we can ignore. Note that there is no bias voltage applied and the nominal capacitance in the datasheet is 225pF at 5V reverse bias. So I can conclude that the QPDs are quite nominal in terms of the junction capacitance.

(Ed: 11/23/2020 The RF components were returned to the 40m)

The dark noise levels of the four Q3000 QPDs were measured with FEMTO DLPCA200 low noise transimpedance amp.

The measurement has been done in the audio frequency band. The amp gain was 10^7 V/A. The reverse bias was set to be 5V and the DC output of the amplifier was ~40mV which corresponds to the dark current of 4nA. It is consistent with the dark current measurement.

The measured floor level of the dark current was below the shot noise level for the DC current of 0.1mA (i.e. 6pA/rtHz).
No anomalous behavior was found with the QPDs.

Note that there is a difference in the level of the power line noise between the QPDs. The large part of the line noises was due to the noise coupling from a soldering iron right next to the measurement setup, although the switch of the iron was off. I've noticed this noise during the measurement sets for QPD #83. Then the iron was disconnected from the AC tap.
 

I see that these measurements are done out to 100 kHz - I guess there is no reason to suspect anything at 55 MHz which is where this QPD will be reading out photocurrent given the low frequency behavior looks fine? The broad feature at ~80 kHz is the usual SR785 feature I guess, IIRC it's got to do with the display scanning rate.

The amplifier BW was 400kHz at the gain of 1e7 V/A. And the max BW is 500kHz even at a lower gain. I have to setup something special to see the RF band dark noise.
With this situation, I stated "the RF dark noise should be characterized by the actual WFS head circuit." in the 40m ELOG.

FEMTO DLPCA200 low noise preamp (brand new)

Keithley Source Meter 2450 (brand new) => Returned 11/23/2020

were brought to the OMC lab for temporary use.

https://nodus.ligo.caltech.edu:8081/QIL/2522

Thorlabs' powermeter controler + S401C head was lent from OMC Lab. Returned to OMC Jul 15, 2022 KA

https://nodus.ligo.caltech.edu:8081/SUS_Lab/1856

See this entry: https://nodus.ligo.caltech.edu:8081/40m/15642

To spare some room on the optical table, I wanted to mount the two TFT monitor units on the HEPA enclosure frame.
I found some Bosch Rexroth parts (# 3842539840) in the lab, so the bracket was taken for the mount. This swivel head works very well. It's rigid and still the angle is adjustable.

https://www.boschrexroth.com/ics/cat/?cat=Assembly-Technology-Catalog&p=p834858

BTW, this TFT display (Triplett HDCM2) is also very nice. It has HDMI/VGA/Video/BNC inputs (wow perfect) and the LCD is Full-HD LED TFT.
https://www.triplett.com/products/cctv-security-camera-test-monitor-hd-1080p-led-display-hdcm2

https://www.newegg.com/p/0AF-0035-00016

https://www.bhphotovideo.com/c/product/1350407-REG/triplett_hdcm2_ultra_compact_7_hd_monitor.html

The only issue is that one unit (I have two) shows the image horizontally flipped. I believe that I used the unit with out this problem before, I'm asking the company how to fix this.

The image flipping of the display unit was fixed. The vendor told me how to fix it.

- Open the chassis by the four screws at the side.
- Look at the pass-through PCB board between the mother and display boards.
- Disconnect the flat flex cables from the pass-through PCB (both sides) and reconnect them (i.e. reseat the cables)

That's it and it actually fixed the image flipping issue.

The output of Mephisto 800NE (former TNI laser) was measured.
The output power was measured with Thorlabs sensors (S401C and S144C). The reference output record on the chassis says the output was 837mW at 2.1A injection.
They all showed some discrepancy. Thus we say that the max output of this laser is 1.03W at 2.1A injection based on the largest number I saw.

[Koji, Jordan, Stephen]

The beam dumps, bonded on Fri 06 Dec 2019, were placed in the newly tuned and configured small dirty ABO at the Bake Lab on Fri 13 Dec 2019.

Images are shared and references are linked below

Bonding log entry - https://nodus.ligo.caltech.edu:8081/OMC_Lab/386

Bake ticket - https://services.ligo-wa.caltech.edu/clean_and_bake/request/992/

OMC Beam Dump - https://dcc.ligo.org/LIGO-D1201285

The beamdumps were taken out from the oven and packed in bags.

The bottom of the V are completely "wet" for 17 BDs among 20 (Attachment 1/2).

3 BDs showed insufficient glue or delamination although there is no sign of lack of rigidity. They were separated from the others in the pack.

are there any measurements of the BRDF of these things? I'm curious how much light is backscattered into the incoming beam and how much goes out into the world.

Maybe we can take some camera images of the cleaned ones or send 1-2 samples to Josh. No urgency, just curiosity.

I saw that ANU and also some labs in India use this kind of blue/green glass for beam dumps. I don't know much about it, but I am curious about its micro-roughness and how it compares to our usual black glass. For the BRDF, I think the roughnesss matters more for the blackness than the absorption.

According to the past backscatter test of the OMC (and the black glass beamdump: not V type but triangular type on a hexagonal-mount), the upper limit of the back reflection was 0.13ppm. https://nodus.ligo.caltech.edu:8081/OMC_Lab/209

I don't have a BRDF measurement. We can send a few black glass pieces to Josh.

Check-in to the OMC lab to see the status. Nothing seemed changed. No bug. The HEPA is running normal. The particle level was 0.

Went into the HEPA enclosure and put a cover on the OMC. Because of the gluing template, the lid could not be close completely (that's expected and fine).

The IPA vector cloth bag was not dry yet but seemed expired (some smell). There is no stock left -> 5 bags to be ordered.

Black and Decker Glue Baking Oven came back to the OMC lab on Aug 10, 2020, Georgia had lent the unit for the SAMS assembly/testing.

Tara: Laser Safety goggle -> Returned

Evan:
HP signal generator (990MHz) (prev. setting 32.7MHz / +3dBm)
Black glass beam dump

Dmass:

LB1005 Oct 24.

Gabriele:

PZT HV Amp

Evan:
HP signal generator (990MHz) (prev. setting 32.7MHz / +3dBm)Returned March 23, 2016
Black glass beam dump

Dmass:

LB1005 Oct 24. This unit is permanently gone to Cryo lab. Acquired a new unit. Aug, 2016.

- The laser was removed and shipped to LHO today.

- UV illuminator / fused silica fiber light guide / UV power meter / UV face shield (Qty 2) will be shipped to MIT.
They are CIT properties except for the illuminator.

Shipment to MIT (L. Barsotti, J. Miller)

1. UV Illuminator (LESCO Super Spot MK III)

2. UV Power meter (American Ultraviolet AIB1001) Caltech property C30140

3. UV protection face shield (VWR UVC-803) Qty.2 Caltech property C30141/C30142

4. UV Fiber Optic Light Guide (American Ultraviolet OLB1081) C30143

All returned: Aug 30, 2016

Kate (ATF)

- 4ch color oscilloscope (Tektronix)

- Chopper controller

- Chopper with a rotating disk

To 40m

First Contact Kit by Calum

Class A Kapton sheets

Item lending as per Ian's request: Particle Counter from OMC Lab to QIL

The particle counter came back to the OMC lab on Aug 10, 2020

[Stephen, Koji]

20 glass beamdumps were bonded at the 40m cleanroom.

Attachment 1: We had 20 fused silica disks with a V-groove and 40 black glass pieces
Attachment 2: The black glass pieces had (usual) foggy features. It is well known to be very stubborn. We had to use IPA/acetone and wiping with pressure. Most of the feature was removed, but we could still see some. We decided to use the better side for the inner V surfaces.
Attachment 3: EP30-2 expiration date was 1/22/2020 👍. 7.66g of EP30-2 was poured and 0.38g of glass sphere was added. Total glue weight was 8.04g
Attachment 4: Glue test piece was baked at 200F in a toaster oven for ~12min. It had no stickiness. It was totally crisp. 👍👍👍
Attachment 5: Painted glue on the V-groove and put the glass pieces in. Then gave a dub of blue at the top and bottom of the V from the outside. In the end, we mostly had the glue went through the V part due to capillary action.
Attachment 6: The 20 BDs were stored in stainless vats. We looked at them for a while to confirm there is no drift and opening of the V part. Because the air bake oven was not available at the time, we decided to leave the assys there for the room temp curing, and then later bake them for the completion of the curing.
 

From Cryo Cav setup

Borrowed LB1005 Servo box -> OMC

The following is the current status of the epoxies used in assembly of the OMC (excerpt from C1900052)

Re-purchasing efforts are underway and/or complete

• DONE
  • Masterbond EP30-2 currently located in Downs 303, Modal Lab (see image)
    • ( WILL EXPIRE JANUARY 2020 )
    • ( tracked using THIS PCS LINK https://services.ligo-la.caltech.edu/Inventory/history.php?recid=1582&invtype=cit_noncap )
  • Electronic Materials Inc Optocast 3553-LV procured via PCard, will arrive today 22 October
    • plan to track using PCS is WIP
• WIP
  • Epoxy Pax EP-1730-1 quoted and requisitioned, PO is WIP

This post captures the curing timeline followed by OMC PZT Assys #9 and #10.

Source file posted in case any updates or edits need to be made.

OMC PZT Assy Production Cure Bake (ref. OMC elog 381) for PZT Assy #9 and #10 started 27 September 2019 and completed 28 September 2019. Captured in the below figure (purple trace). Raw data has been posted as an attachment as well.

We have monitored the temperature in two ways:

1) Datalogger thermocouple data (purple trace).
2) Checking in on temperature of datalogger thermocouple (lavender circles) and drive thermocouple (lavender diamonds), only during initial ramp up.

Comments on bake:

• No changes were made to the tuning or instrumentation of the oven between the successful qualifying bake obtained on 26 September (ref. OMC elog 380). However, the profile seems to have been more similar to prior qualifying bake attempts that were less successful (ref. OMC elog 379), particularly as the oven seems to have ramped to an overtemperature state. I am a bit mystified, and I would like to see the oven tuning characterized to a greater extent than I have had time and bandwith to complete within this effort.
• The maximum datalogger temperature was 104 °C, and the duration of the soak (94 °C or higher) was 68 minutes. This was in contrast to a programmed soak of 2.5 hours and a programmed setpoint of 84 °C.
• The drive thermocouple did appear to be under-reporting temperature relative to the datalogger thermocouple, but this was not confirmed during the soak period. Neither thermocouple was calibrated as part of this effort.

[Stephen, Shruti, Koji]

We worked on the gluing of the PZT sub-assy (#9 and #10) along with the designed arrangement by Shruti (OMC ELOG 374).

The detailed procedures are described in E1300201 Section 6.2 PZT subassembly and Section 7.3 EP30-2 gluing.

We found that the PZTs, which were debonded from the previous PZT sub assy with acetone, has some copper wires oxidized. However, we confirmed that this does not affect the conductivity of the wires, as expected.

The glue test piece cooked in the toaster oven showed excellent curing. GO SIGNAL

Stephen painted the PZT as shown in Attachment 1.

The fixtures were closed with the retaining plate and confirmed that the optics are not moving in the fixtures.

At this point, we checked the situation of the air-bake oven. And we realized that the oven controller was moved to another vacuum oven and in use with a different setting.

Stephen is going to retrieve the controller to the air bake oven and test the temp profile overnight. Once we confirm the setting is correct, the PZT sub assys will be heat cured in the oven.  Hopefully, this will happen tomorrow. Until then, the sub-assys are resting on the south flow bench in the cleanroom.

Friday: [Stephen, Koji]

As the oven setting has qualified, we brought the PZT assys in the air bake oven.

Monday: [Stephen, Shruti, Koji]

We brought the PZT assys to the clean room. There was not bonding between the flexture and the PZT subassy (Good!). Also the bonding o at each side looks completely wetted and looks good. The package was brought to the OMC lab to be tested in the optical setup.

Follow up on OMC elog 379

I was able to obtain the following (dark blue) bake profile, which I believe is adequate for our needs.

The primary change was a remounting of the thermocouple to sandwich it between two stainless steel masses. The thermocouple bead previously was 1) in air and 2) close to the oven skin.

The 40m Bake Lab's Dirty ABO's OMEGA PID controller was borrowed for another oven in the Bake Lab (sound familiar? OMC elog 377), so I have had to play with the tuning and parameters to recover. This bake seemed to inadequately match the intended temperature profile for some reason (intended profile is shown by plotting prior qualifying bake for comparison).

The parameters utilized here are exactly matching the prior qualifying bake, except that the autotuning may have settled on different parameters.

Options to proceed, as I see them, are as follows:

1. reposition the oven's driving thermocouple closer to the load and attempt to qualify the oven again overnight
2. retune the controller and attempt to qualify the oven again overnight
3. proceed with current bake profile, except monitor the soak temperature via data logger thermocouple and intervene if temperature is too high by manually changing the setpoint.

The 40m Bake Lab's Dirty ABO's OMEGA PID controller was borrowed for another oven in the Bake Lab, so I have had to play with the tuning and parameters to recover a suitable bake profile. This bake is pictured below (please excuse the default excel formatting).

I have increased the ramp time, temperature offset, and thermal mass within the oven; after retuning and applying the parameters indicated, the rate of heating/cooling never exceeds .5°C/min.

The ABO is controlled by a different temperature readout from the data logger used to collect data; the ABO readout is a small bead in contact with the shelf, while the data logger is a lug sandwiched between two stainless steel masses upon the shelf. I take the data logger profile to be more physically similar to the heating experienced by an optic in a gluing fixture, so I feel happy about the results of the above bake.

I plan to add the data source file to this post at my earliest convenience.

The following items are presently staged at the 40m Bake Lab (see photo indicating current location) (noting items broght by Koji as well):

1. Bonding fixtures, now modified with larger washers to constrain springs, and with modification from OMC elog 358.
2. Curved Mirrors and Tombstones as selected by Shruti in OMC elog 374.
3. PZTs as debonded from first iteration subassemblies (SN 12 and SN 13)
4. Epoxy-cure-testing toaster oven
5. Other items I can't think of but will populate later  =D

The following item is in its home in Downs 303 (Modal Lab)

1. EP30-2 epoxy (expiration 2020 Jan 22) with full kit (tracked in PCS via location update [LINK])

Here is a summary of the events of the last week, as they relate to EP30-2.

1) I lost the EP30-2 syringes that had been ordered for the OMC, along with the rest of the kit.

• Corrective action: Found in the 40m Bake Lab garbing area.
• Preventative action: log material moves and locations in the OMC elog
• Preventative action: log EP30-2 moves and locations in PCS via location update [LINK]
• Preventative action: keep EP30-2 kit on home shelf in Modal Lab unless kit is in use

2) The EP30-2 syringes ordered for the OMC Unit 4 build from January had already expired, without me noticing.

• Corrective action: Requested LHO ship recently-purchased EP30-2 overnight
• Preventative action: log expiration dates in OMC elog
• Preventative action: begin purchasing program supported by logistics, where 1 syringe is maintained on hand and replaced as it expires

3) LHO shipped expired epoxy on Thursday. Package not opened until Monday.

• Corrective action: Requested LHO ship current EP30-2 overnight, this time with much greater scrutiny (including confirming label indicates not expired)
• Preventative action: Packages should be opened, inspected, and received in ICS or Techmart on day of receipt whenever possible.

4) Current, unopened syringe of EP30-2 has been received from LHO. Expiration date is 22 Jan 2020. Syringe storage has been improved. Kit has been docked at its home in Downs 303 (Modal Lab) (see attached photo, taken before receipt of new epoxy).

Current Status: Epoxy is ready for PZT + CM subassembly bonding on Monday afternoon 23 September.

Aim: To find the combinations of mounting prism+PZT+curved mirror to build two PZT sub-assemblies that best minimises the total vertical beam deviation.

(In short, attachment 1 shows the two chosen sets of components and the configuration according which they must be bonded to minimize the total vertical angular deviation.)

The specfic components and configuration were chosen as follows, closely following Section 2.3.3 of T1500060:

Available components:

Mounting prisms: 1,2,12,14,15 (Even though there is mention of M17 in the attachments, it can not be used because it was chipped earlier.)

PZTs: 12,13

Curved mirrors: 10,13

Method:

For a given choice of prism, PZT and mirror, the PZT can be placed either at 0deg or 180deg, and the mirror can rotated. This allows us to choose an optimal mirror rotation and PZT orientation which minimises the vertical deviation.

Total vertical angle 

 was measured by Koji as described in elog 369.

,              are the wedge angle and orientation respectively and were measured earlier and shown in elog 373 . 

,               The measurement of the location of the curvature bottom (d, ) of the mirrors is shown in elog 372 . The optimal  is to be found.

These steps were followed:

1. For every combination of prism, PZT, and mirror, the total vertical deviation was minimized with respect to the angle of rotation of the curved mirror computationally (SciPy.optimize.minimize). The results of this computation can be found in Attachment 2: where Tables 1.1 and 2.1 show the minimum achievable deviations for mirrors C10 and C13 respectively, and Tables 1.2 and 2.2 show the corresponding angle of rotation of the mirrors  .
2. From the combinations that show low total deviations (highlighted in red in Attachment 2), the tolerances for 5 arcsec and 10 arcsec deviations with mirror rotation were calculated, and is shown in Tables 1.3, 1.4, 2.3, 2.4 of Attachment 2.
3. While calculating the tolerances, the dependence of the vertical deviations with rotation were also plotted (refer Attachment 3).
4. Two sets from available components with low total deviation and high tolerance were chosen. 

Result:

These are the ones that were chosen:

1. M14 + PZT13 at 0deg + C13 rotated by 169deg anticlockwise (tot vertical dev ~ -3 arcsec)
2. M12 + PZT12 at 0deg + C10 rotated by 88deg clockwise (tot vertical dev ~0 arcsec)

The method of attaching them is depicted in Attachment 1.

Yesterday I measured the thickness of the PZTs in order to get an idea how much the PZTs are wedged.

For each PZT, the thickness at six points along the ring was measured with a micrometer gauge.
The orientation of the PZT was recognized by the wire direction and a black marking to indicate the polarity.

A least square fitting of these six points determines the most likely PZT plane.
Note that the measured numbers are assumed to be the thickness at the inner rim of the ring
as the micrometer can only measure the maximum thickness of a region and the inner rim has the largest effect on the wedge angle.
The inner diameter of the ring is 9mm.



The measurements show all PZTs have thickness variation of 3um maximum.

The estimated wedge angles are distributed from 8 to 26 arcsec. The directions of the wedges seem to be random
(i.e. not associated with the wires)



As wedging of 30 arcsec causes at most ~0.3mm spot shift of the cavity (easy to remember),
the wedging of the PZTs is not critical by itself. Also, this number can be reduced by choosing the PZT orientations
based on the estimated wedge directions --- as long as we can believe the measurements.



Next step is to locate the minima of each curved mirror. Do you have any idea how to measure them?

Wedge and thickness measurements of PZTs 12 and 13 took place after debonding and cleaning - results are shown in the first image (handwritten post-it format).

These thickness measurements seem to have come back thinner than previous measurements. It is possible that I have removed some PZT material while mechanically removing glue. It is also possible that there is systematic error between the two sets of measurements. I did not run any calculations of wedge ange or orientation on these data.

Note that cleaning of debonded PZTs involved mechanically separating glue from the planar faces of PZTs. The second image shows the razer blade used to scrape the glue away.

There were thick rings of glue where there had been excess squeezed out of the bond region, and there was also a difficult-to-remove bond layer that was thinner. I observed the presence of the thin layer by its reflectivity. The thick glue came off in patches, while the thin glue came off with a bit of a powdery appearance. It was hard to be certain that all of the thin bond layer came off, but I made many passes on each of the faces of the 2 PZTs that had been in the bonded CM assemblies. I found it was easiest to remove the glue in the bonded

I was anticipating that the expected 75-90 micron bond layer would affect the micrometer thickness measurements if it was still present, but I did not notice any irregularities (and certainly not at the 10 micron level), indicating that the glue was removed successfully (at least to the ~1 micron level).

Using the measurements of PZTs 12,13 taken by Stephen, I estimated the wedging angle and orientation following Section 2.3.1 of T1500060. The results can be found in Attachment1 and is summarised as follows.

For PZT 12, PZT 13 respectively:

Avg. height = 2.0063 mm, 2.0035 mm

Wedge direction (from the same direction as in the doc: positive right) = 120 deg, 120 deg

Wedge angles = 45.8 arcsec, 30.6 arcsec

This was done assuming that the measurements were taken uniformly at intervals of 60deg along the inner rim of the PZT. The diameter (2r) of the inner rim, according to T1500060, is 9mm. The measured heights were fitted with the function

as depicted in Attachment2 to find wedging angle and orientation .

I attempted to fit the data taken by Koji of the beam spot precession at the CCD in order to find the location of the curvature bottom in terms of its distance (d) and angle () from the centre of the mirror. This was done using the method described in a previous similar measurement  and Section 2.1.3 of T1500060.

Initially, I attempted doing a circle_fit on python as seen in Attachment 1, and even though more points seem to coincide with the circle, Koji pointed out that the more appropriate way of doing it would be to fit the following function:

since that would allow us to measure the angle more accurately; is the anti-clockwise measured angle that the curvature bottom makes with the positive x direction.

As seen on the face of the CCD, x is positive up and y is positive right, thus, plotting it as the reflection (ref. Attachment 2) would make sure that  is measured anti-clockwise from the positive x direction.

The distance from the curvature bottom is calculated as 

r: radius of precession on CCD screen (value obtained from fit parameters, uncertainty in this taken from the std dev provided by fit function)

R: radius of curvature of the mirror 

L: Distance between mirror and CCD

R = 2.575  0.005 m (taken from testing procedure doc referenced earlier) and L = 0.644  0.005 m (value taken from testing doc, uncertainty from Koji)

	d (mm)	(deg)
C7	0.554  0.004	-80.028  0.005
C10	0.257  0.002	-135.55  0.02
C13	0.161  0.001	-79.31  0.06

Liyuan's scattering measurement for the A and C mirrors.

[Stephen, Koji]

The perpendicularity of some of the A and M prisms were tested.

Results

- The measurement results are listed as Attachment 1 and 2 together with the comparisons to the measurement in 2013 and the spec provided from the vendor.
- Here, the positive number means that the front side of the prism has larger angle than 90deg for the air side. (i.e. positive number = facing up)
- The RoC of the curved mirrors is 2.5m. Therefore, roughly speaking, 83arcsec corresponds to ~1mm beam spot shift. The requirement is 30 arcsec.
- The A prisms tend to have positive and small angle deviations while the M prisms to have negative and large (~50arcsec) angle deviations.
- The consistency: The measurements in 2013 and 2019 have some descrepancy but not too big. This variation tells us the reliability of the measurements, say +/-30arcsec.

Setup

- The photos of the setup is shown as Attachments 3/4/5. Basically this follows the procedure described in Sec 2.2.2 of T1500060.
- The autocollimator (AC) is held with the V holders + posts.
- The periscope post for the turning Al mirror was brought from Downs by Stephen.
- The turning mirror is a 2" Al mirror. The alignment of the turning mirror was initially aligned using the retroreflection to the AC. Then the pitching of the holder was rotated by 22.5deg so that the AC beam goes down to the prism.
- The prism is held on a Al mirror using the post taken from a prism mount.
- If the maximum illumination (8V) is used, the greenish light becomes visible and the alignment becomes easier.
- There are two reflections 1) The beam which hits the prism first, and then the bottom mirror second, 2) The beam which hits the bottom mirror first and then the prism second. Each beam gains 2 theta compared to the perfect retroreflection case. Therefore the two beams have 4 theta of their relative angle difference. The AC is calibrated to detect 2 theta and tells you theta (1div = 1 arcmin = 60 arcsec). So just read the angle defferencein the AC and divide the number by 2 (not 4).

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