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  464   Fri Dec 2 11:42:03 2022 KojiOpticsCharacterizationOMC #1 cleaning for water soluble contaminants
[Camille, Koji] Log of the work on Nov 30, 2022
The following is the notes from GariLynn

Cleaning for water-soluble contaminants:
It uses deionized water instead of acetone.
  • The first contact must go on the mirror before the water can dry,  so you will need a bigger brush. We have some that are 1cm, I think they are in the back wall cabinet of B119.
  • For the bigger brush, you will need a beaker and perhaps a bigger bottle of First Contact.  There is one in the mini-fridge in the back corner of B110
  • You use an alpha swab instead of a cotton bud
  • For this effort, I encourage you to get a bottle of DI water from stores.
  • I also encourage you to rehearse the motions beforehand - timing is critical, and your mirrors are in a tight spacing

(Attachment 1)
We obtained Regent grade DI water. It was poured into a smaller cup.
FC liquid was also poured into a small beaker.
Wash the mirror with a swab. We should have used a smaller swab that GariLynn has in her lab.

As soon as the mirror was wiped with the water, the FC was applied with a large brush. Don't let the water away!
Then more layer of the FC was added as usual.

The quick painting of FC made a mess around the mirrors due to excess liquid (Attachment 2). So, we decided to remove the FC remnants (on non-optic surfaces) with cotton swabs and then applied FC as usual.

This made the mess removed, however, we found the OMC loss was increased to >10%(!) (Attachment 3). We decided to continue tomorrow (Thu) with more weapons loaded consulting with GariLynn.


Attachment 1: PXL_20221130_234101575.jpg
Attachment 2: PXL_20221130_234013958.jpg
Attachment 3: PXL_20221201_021727724.jpg
Attachment 4: Screen_Shot_2022-12-02_at_12.43.02.png
  465   Fri Dec 2 12:38:15 2022 KojiOpticsCharacterizationOMC #1 cleaning for water soluble contaminants

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.

Attachment 1: PXL_20221202_034932211.jpg
Attachment 2: OMC_loss.pdf
  466   Fri Dec 2 23:58:33 2022 KojiOpticsCharacterizationOMC #1 cleaning for water soluble contaminants

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.

Attachment 1: PXL_20221203_063327268.jpg
Attachment 2: OMC_loss.pdf
  457   Tue Nov 15 10:58:53 2022 KojiOpticsGeneralOMC #1 damaged black glass removal

[Camille, Koji]

The damaged black glass was removed from the OMC breadboard leaving the glass base.
The black glass pieces were bonded very tightly on the FS base with EP30-2. The apparent amount of the bond was not so much but it was such hard that removal by hand was not possible.
We decided to give drips of Acetone on the base hoping the gradual dissolving of EP30-2. Using a knife edge, the "filets" of the bonds were removed, but the BD was still tight.

By wedging the black glass-black glass bonding with the nife edge, the left side (the directly damaged one) was taken off from the structure leaving a tiny fragment of the glass on the base.

The remaining one was even stronger. We patiently kept dripping Acetone on the base and finally, the black glass piece was knocked off and removed from the base.

Attachment 1: The base right after the black glass removal.

Attachment 2: The black glass pieces were stored in a container with Al foil + clean cloth bed. The damaged and fogged surfaces faced up.

Attachment 3: The zoom-in shot of the black glass pieces.

Attachment 4: The base was wiped with Acetone and cleaned with FC. We will bond another BD assembly on the base, presumably using the UV epoxy.

Attachment 1: PXL_20221114_222641455.jpg
Attachment 2: PXL_20221114_222544330.jpg
Attachment 3: PXL_20221114_222555849.jpg
Attachment 4: PXL_20221114_233748631.jpg
  458   Tue Nov 15 11:12:24 2022 KojiOpticsGeneralOMC #1 fogging on the AR side of BS1 cleaned

[Camille, Koji]

Photo of the BS1 AR cleaning process

Attachment 1: Before cleaning. Foggy surface is visible.

Attachment 2: After FC cleaning. The structure of the deposited material is still quite visible.

Attachment 3: Acetone scrubbing. Cotton Q-tip was used so that the stick does not melt with acetone.

Attachment 4: After acetone scrubbing. Nicely clean!

Acetone scrubbing was applied to HR/AR of BS1, FM1, FM2, BS2, and HR of CM1 and CM2. (total 10 surfaces)
Then final FC paint was applied to these 10 surfaces.

We'll come back to the setup on Thu for FC peeling and loss measurement.

Attachment 1: PXL_20221114_225338114.jpg
Attachment 2: PXL_20221114_232824245.jpg
Attachment 3: PXL_20221114_233714774.jpg
Attachment 4: PXL_20221114_233748631.jpg
  477   Thu Jan 26 23:46:13 2023 KojiOpticsGeneralOMC #1 input beam dump bonding

A beam dump was stacked on the base of the previous beam dump. The angle was determined so that the main transmission goes through while the stray OMC reflection is blocked without clipping at the edge.

The resulting alignment of the beam dump is shown in Attachment 1.

The beam dump tended to slip on the base. To prevent that a couple of weights were placed around the bonding area. (Attachment 2)


Attachment 1: PXL_20230127_052955482.jpg
Attachment 2: PXL_20230127_052949869.jpg
  475   Thu Jan 26 23:07:14 2023 KojiOpticsGeneralOMC #4: Input beam dump bonding

[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.

Attachment 1: PXL_20230126_221556977.jpg
  474   Thu Jan 26 22:57:19 2023 KojiOpticsGeneralOMC #4: One Invar block bonded with tilt

[Camille, Koji]

The bottom side template was separated into two pieces and successfully removed from the breadboard. The template was assembled together again and bagged to store it in a cabinet.

We found that the invar block for DCPD(R) was bonded with some air gap (Attachment2 1/2).


The Allen key used as a weight was too small, which caused it to get under one of the screws used as hooks and lift the block.


We've investigated the impact of this tilt.

- Bonding strength: The bonding area is ~60% of the nominal. So this is weak, but we can reinforce the bonding with an aluminum bar.
- Misalignment of the DCPD housing: The tilt will laterally move the position of the DCPD. However, the displacement is small and it can be absorbed by the adjustment range of the DCPD housing.
- Removal: From the experience with the removal of the beam dump glass, this requires a long time of acetone soaking.


- We don't need to remove the invar block.
- Action Item: Reinforcement of the bonding

Attachment 1: PXL_20230126_221425695.jpg
Attachment 2: PXL_20230126_221522416.jpg
  483   Thu Feb 2 03:09:41 2023 KojiOpticsGeneralOMC #4: One Invar block bonded with tilt

[Camille, Thejas, Koji]

We added a reinforcement bar at the back of the invar block which had the tilt issue.

The reinforcement bar was added to the backside rather than the side or front such that the DCPD housing does not interfere with the reinforcement bar.

Also, small amount of EP30-2 was added to the CM2 wire so that the repeated bend of the PZT wire cause the disconnection at the PZT.

Attachment 1: PXL_20230202_003156761.jpg
Attachment 2: PXL_20230202_003204058.jpg
  484   Sat Feb 4 03:16:10 2023 KojiOpticsGeneralOMC #4: One Invar block bonded with tilt

The attached photo shows the resulting bond spread.


Attachment 1: PXL_20230202_213114009.jpg
  479   Sat Jan 28 00:46:21 2023 KojiMechanicsGeneralOMC #4: Replaced the locks of the transport fixture

Yesterday, we noticed that we could not close the transport fixture for OMC #4. We could not fully rotate the knobs of the locks. Today, I took the hooks from the functioning locks of the spare transport fixture.

It turned out that the default dimension of the lock seemed too tight. The functioning one has the through holes elongated by a file or something. This modification will be necessary for future transport fixtures.

Attachment 1: PXL_20230128_022952669.jpg
  476   Thu Jan 26 23:16:35 2023 KojiOpticsConfigurationOMC #4: Top side bonding.

[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.


Attachment 1: PXL_20230126_235309334.jpg
Attachment 2: PXL_20230127_053008237.jpg
Attachment 3: PXL_20230127_053020709_2.jpg
Attachment 4: PXL_20230127_053042809.MP_2.jpg
Attachment 5: PXL_20230127_053058275_2.jpg
  471   Thu Jan 19 23:45:44 2023 KojiOpticsGeneralOMC #4: cavity mirror bonding

[Koji, Camille]

We worked on the bonding of the flat mirrors for the OMC cavity with UV epoxy.

- Prepared the UV illumination setup. Cleaned up the table a bit to spare some space for the illuminator.
- Checked the output power of the illuminator. The foot pedal worked fine. The timer was set to be 10s. The UV output from the fiber was nominally 6W. This is after some warming up for ~1min. (Checked the output power continuously with the UV power meter.)

- Checked the cavity alignment / FSR / TMS - it looked good at this moment

- We confirmed that the UV epoxy has an expiration of July 3, 2023. The bond capsule was brought from Downs right before the work started, and thawed at the lab.

FM1 bonding

- The bottom of FM1 and the breadboard were cleaned. Cleaning with lens cleaning paper + IPA remained a few specks of dust on the surface. We decided to use Vectra swabs to wipe the breadboard surface. This worked pretty well.
- Applied a tap of UV epoxy to FM1 and placed it on the template. The optic was constrained by a retainer clip.
- We found that the spot positions were significantly moved. Probably FM1 was not well touching the template before. We tried to recover the previous optical axis by aligning CM1 and CM2.
- Here is the tip: align the beam on CM1 at the desired spot. Move CM1 to bring the spot on CM2 to the desired spot. CM2 is aligned to have TEM00 as much as possible.

- We recovered reasonable spots on the mirrors. Measured the FSR and TMS (vertical and horizontal) to be 264.73MHz, 58.18MHz, and 58.37MHz, respectively. This makes the 9th-order modes well separated from TEM00. Very good.

- Gave UV illumination 10s x 2. Confirmed that the mirror is rigidly bonded.


FM2 bonding

- Continued to bond the other flat mirror. The same process was repeated.
- The bottom of FM2 and the breadboard were cleaned.
- Applied a tap of UV epoxy to FM2 and placed it on the template. The optic was constrained by a retainer clip.
- Measured the FSR and TMS (vertical and horizontal) to be 264.7925MHz, 58.15MHz, and 58.3725MHz, respectively. This makes the 9th-order modes well separated from TEM00. Very good.

- Gave UV illumination 10s x 2. Confirmed that the mirror is rigidly bonded.

SM1/BS2/BS3 bonding

- Continued to bond some less important mirrors.
- SM1 was placed on the template with the same step as above. BS2 (for QPD) and a dummy QPD housing were also placed just to check if the optical axis has any inconsistency. The good beam alignment on the QPD housing was confirmed.
- Applied a bond to SM1 and blasted the UV (20s)
- Applied a bond to BS2. Checked the alignment on QPD1 again. It looked good. UV illumination was applied.

- Placed BS3 to the cavity transmission. A dummy DCPD housing was placed at the reflection side of BS3. There was no inconsistency with the beam alignment.
- The UV illumination was applied (20s).

Optic Inventory

Breadboard: #6
BS1: E6
FM1: A1
FM2: A3
CM1: PZT ASSY #8 (M7+PZT11+C11)
CM2: PZT ASSY #11 (M14+PZT13+C13)
SM1: E9
BS2: B8
BS3: B6

  472   Mon Jan 23 19:51:20 2023 KojiOpticsGeneralOMC #4: cavity mirror bonding

[Camille, Koji]

We continued to bond two CM mirrors and the other two steering mirrors for QPD2.

Before the bonding work, the FSR and TMSs were checked again.

FSR: 264.7925 MHz
TMS_V: 58.15125 MHz
TMS_H: 58.33375 MHz

Checked the transmission: The OMC loss was 4.3 +/- 0.2 %.

This does not make the HOMs coincidently resonant until the 18th-order (+9MHz). Looks good.

CM1/CM2/SM2/SM3 bonding

- Applied the bond to CM1 and the UV illuminated.
- Applied the bond to CM2 and the UV illuminated.
==> The cavity bonding is completed.

Removed the micrometer for CM2 to allow us to bond SM2/SM3
- Checked the spot at QPD2: The spot was a couple of mm too left. This was too much off compared to the QPD adjustment range. ==> Decided to shim the SM3 position with a piece of Al foil.
- Otherwise everything looked good. SM2/SM3 were bonded.

Invar block bonding

Prepared EP30-2
- There are three tubes of EP30-2 that expires on 2/22, 2023.
- A tube was almost empty. Used this tube to fill/purge the applicator. The 2nd tube was then attached to squeeze out 8g of glue mixture. 
- 0.4g of fused silica beads were added to the glue mixture.
- Mixed the bond and a test piece was baked by the oven. (200F=95C, 5min preheat, bakeing 15min).
- The glue test piece was "dry" and crisp. Looked good.
- Applied the glue on the invar blocks. Confirmed that the bonding surfaces were made completely "wet".
- 4-40 screws were inserted to the blocks so that the blocks were pushed toward the template. See Attachments 3 and 4.


Optic Inventory

Breadboard: #6
BS1: E6
FM1: A1
FM2: A3
CM1: PZT ASSY #8 (M7+PZT11+C11)
CM2: PZT ASSY #11 (M14+PZT13+C13)
SM1: E9
BS2: B8
SM2: E11
SM3: E14
BS3: B6

Attachment 1: HOM_plot_PZT0_0.pdf
Attachment 2: PXL_20230124_032358482.MP.jpg
Attachment 3: PXL_20230124_032452805.MP.jpg
Attachment 4: PXL_20230124_032425638.jpg
  319   Tue Mar 19 17:30:25 2019 KojiGeneralCharacterizationOMC (002) Test items

OMC #002 Optical tests

  • FSR measurement (done, 2019/1/8-9, 2019/4/1)
  • TMS measurement (done, 2019/1/9)
  • TMS measurement (with DC voltage on PZTs) (done, 2019/1/10)
  • Cleaning (done, 2019/3/19)
  • Power Budget (done, 2019/3/19, 2019/4/1)
  • PZT DC response (done, 2019/3/27)
  • PZT AC response (done, 2019/3/27)
  • QPD alignment (done, 2019/4/5)
  • DCPD alignment (done, 2019/4/4)
  • Beam quality check (done, 2019/4/4)

(Backscattering test)

(Cabling / Wiring)

  • (Attaching cable/mass platforms)
  • (PZT cabling)
  • (DCPD cabling)
  • (QPD cabling)

(First Contact)
(Packing / Shipping)

  325   Fri Apr 5 23:30:20 2019 KojiGeneralGeneralOMC (002) repair completed

OMC(002) repair completed

When the cable harness of OMC(004) is going to be assembled, the cable harness of OMC(002) will be replaced with the PEEK one. Otherwise, the work has been done.

Note that there are no DCPDs installed to the unit. (Each site has two in the OMC and two more as the spares)

More photos: https://photos.app.goo.gl/XdU1NPcmaXhATMXw6

Attachment 1: P_20190405_222401.jpg
Attachment 2: P_20190405_222509.jpg
Attachment 3: P_20190405_222529.jpg
  547   Thu Jun 15 13:13:57 2023 KojiElectronicsConfigurationOMC (004) DCPD/QPD preparation

Work log for June 14, 2023

  • Selected QPDs from the stock: QPD#62 for QPD1 and QPD#70 for QPD2 were selected from the QPD stock T1200063.
  • The legs of the QPDs were trimmed so that the cable could completely flush with the mount.
  • A test PD (Excelitas) was mounted on a DCPD housing.
  • They are ready for installation and testing.
Attachment 1: PXL_20230615_001850494.jpg
  556   Mon Jul 10 20:23:47 2023 KojiOpticsCharacterizationOMC (004) Spot positions

Belated entry: OMC(004) Spot positions (Jun 15, 2023)

Photographs of the spot positions on the cavity mirrors and the DCPDs/QPDs as well as the reflected beams towards the beamdumps.

Attachment 1: FM1.jpeg
Attachment 2: FM2.jpeg
Attachment 3: CM1.jpeg
Attachment 4: CM2.jpeg
Attachment 5: DCPD1.jpeg
Attachment 6: DCPD1_R.jpg
Attachment 7: DCPD2.jpeg
Attachment 8: DCPD2_R.jpg
Attachment 9: QPD1_R.jpg
Attachment 10: QPD2_R.jpg
  558   Mon Jul 10 20:52:19 2023 KojiOpticsCharacterizationOMC (004) TMS measurement

Belated entry: OMC(004) TMS measurement with the PZT voltages scanned (Jun 12/15, 2023)

Attachment 1: HOM_plot_PZT0_0.pdf
Attachment 2: OMC_20230612.pdf
Attachment 3: HOM_PZTV_PZT1_0V.pdf
  482   Wed Feb 1 01:44:14 2023 KojiGeneralGeneralOMC (004) plan

2/1 2:30PM~ Bonding reinforcement (Last EP30-2 gluing)

2/2 1:00PM~ Peripheral attachment / Optical testing setup

  550   Sun Jun 25 21:08:37 2023 KojiGeneralCharacterizationOMC (004) transported to Downs for cable furnishing

OMC (004) + the transport fixture was transported to Downs 227 with the boxes for OMC cabling hardware and DCPD/QPD connector parts.

Attachment 1: PXL_20230624_073552303.jpg
Attachment 2: PXL_20230624_073531044.jpg
  595   Mon Aug 7 16:00:30 2023 KojiGeneralGeneralOMC (004): Cable installation

The writing of this elog is still on going

[Dean, Stephen, Koji]

4th OMC production was completed.

Today's Menu

  • PZT connector assembly
  • DCPD/QPD cable installation to the DCPD/QPD housings
  • Cable installation on the connector harness
  • Routing of the cables / Installation of the cable ties
  • Storage

== PZT connector assembly ==

Dean and Stephen already crimped the pins to the PZT wires in the previous session.
We wanted to complete this cable by inserting the pins into the mighty mouse connector

This MM connector has the pin1 at the top left and numbered clock wise when it is seen from the mating side with the center notch up. 

We looked at D1300589. This drawing has some inconsistency in the description (LV Piezo at the left side turns to HV Piezo at the right side), but it is not an issue as we are supposed to have two identical (or similar) PZTs.

Here the arrangement of the MM connectors:
- Pin 1:  PZT1 Pos
- Pin 2:  PZT1 Neg
- Pin 3:  PZT2 Pos
- Pin 4:  PZT2 Neg

== DCPD/QPD cable installation to the DCPD/QPD housings ==

We opened the cable bags and found that they were not completed. The cables didn't have face parts. We found the face parts in the cable parts plastic box, but the screws were missing. We had to send one to pick up screws from the OMC lab while the others were working on inserting helicoils into the cable ASSYs.

We also found the ancient elog about the cables. This told us that the cable set we had was not the proper one, but rather spares with all the long variants of the cables. This meant that the routing needed to be different from the past 3 OMCs.

The flex PCB boards have solder bumps sticking out. This prevented the front pieces from being flush with the back piece. It was slightly improved by clipping a few solder marks (Attachments 1/2). The cables were inserted into the DCPD/QPD housings. To align the connector heads properly, we installed dummy (i.e., non-high-QE PDs with caps) PDs to the housing. The QPDs were necessary to be removed from the housing as it was known that the insertion was very difficult.

DCPD cable for DCPD1 (Trans side): D1300372 S1301809
DCPD cable for DCPD2 (Refl side): D1300372 S1301807

QPD cable for QPD1 (Refl side): D1300375 S1301816
QPD cable for QPD2 (Trans side): D1300375 S1301814

Cable installation on the connector harness

We flipped the OMC (manually) so that we could work on the suspension side. The connectors were attached to the cable harness. The connector nuts were fastened by a nut spanner and/or a long-nose plier. (Attachment 3)

Routing of the cables / Installation of the cable ties

As mentioned above, some cables are longer than they used to be. So the routing required some creativity. The cables were attached to the cable pegs. We used Kapton sheets to distribute the cable tie's pressure to the wires and also protect the wires from the ties.


The OMC (004) and the transport fixture were so far placed in the 40m clean room.

Attachment 1: IMG_3546.jpg
Attachment 2: IMG_3547.jpg
Attachment 3: IMG_3564.jpg
Attachment 4: IMG_3571.jpg
  535   Thu May 4 15:12:14 2023 KojiGeneralCharacterizationOMC (004): Final Testing
  • FSR measurement (dip) - done May 3, 2023
  • FSR measurement (RFAM injection) - done May 3, 2023
  • TMS measurement with PZT1/2 swept from 0V~200V - 1st session Jun 12, 2023 / 2nd session Jun 15
  • Mirror cleaning / Power budget - done [OMC ELOG 530]
  • PZT response DC / AC - done May 17, 2023
  • DCPD shim height adjustment
  • QPD alignment / shim height adjustment
  • Alignment: beam spot photos
  541   Tue May 16 10:26:12 2023 KojiGeneralCharacterizationOMC (004): Final Testing
  • FSR measurement (dip) - done May 3, 2023
  • FSR measurement (RFAM injection) - done May 3, 2023
  • TMS measurement with PZT1/2 swept from 0V~200V
  • Mirror cleaning / Power budget - done [OMC ELOG 530]
  • PZT response DC / AC done May 11, 2023 [OMC ELOG 537]
  • DCPD shim height adjustment
  • QPD alignment / shim height adjustment
  • Alignment: beam spot photos


The OMC PZT ac response was resorded was not as expected and a remeasurement will be attempted this week. Data: https://www.dropbox.com/s/7pf0k6awoa4wg0z/230503.zip?dl=0 





  • FSR measurement (dip) - done May 3, 2023
  • FSR measurement (RFAM injection) - done May 3, 2023
  • TMS measurement with PZT1/2 swept from 0V~200V
  • Mirror cleaning / Power budget - done [OMC ELOG 530]
  • PZT response DC / AC
  • DCPD shim height adjustment
  • QPD alignment / shim height adjustment
  • Alignment: beam spot photos


  596   Mon Aug 7 16:01:05 2023 KojiGeneralGeneralOMC (004): Production completed

OMC (004) Production completed. The OMC together with the transport fixture is still placed at the 40m clean room.

Attachment 1: PXL_20230807_210716110.jpg
Attachment 2: PXL_20230807_210724685.jpg
  127   Tue May 14 19:06:00 2013 KojiCleanGeneralOMC Baking

The OMC is in the air bake oven now.


  387   Fri Dec 13 14:59:18 2019 StephenGeneralGeneralOMC Beam Dump Production Cure Bake

[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

Attachment 1: IMG_6080.JPG
Attachment 2: IMG_6079.JPG
  388   Wed Dec 18 21:54:53 2019 KojiGeneralGeneralOMC Beam Dump Production Cure Bake

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.

Attachment 1: P_20191218_160650_vHDR_On.jpeg
Attachment 2: P_20191218_160705_vHDR_On.jpeg
Attachment 3: P_20191218_160733_003.jpeg
  393   Mon Sep 28 16:03:13 2020 ranaGeneralGeneralOMC Beam Dump Production Cure Bake
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.

  394   Mon Sep 28 16:13:08 2020 KojiGeneralGeneralOMC Beam Dump Production Cure Bake

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.

  110   Sat Apr 13 21:06:02 2013 KojiOpticsGeneralOMC Bottom-side: cavity glued

[Jeff, Zach, Lisa, Koji]

Gluing of the cavity mirrors went very well!!!


- Checked if the cavity is still resonating. => Yes.

- Checked the FSR: 264.251MHz => 1.1345m
  2.5mm too long => Move each micrometer by 0.625mm backward

  Aligned the cavity again and checked the FSR: 264.8485MHz => 1.13194m
  TMS(V): 58.0875MHz => gamma_V = 0.219324
  TMS(H): 58.1413MHz => gamma_H = 0.219526
  the 9th modes of the carrier is 9.7-10.4 line width (LW) away from the carrier resonance
  the 13th modes of the lower f2 sideband are 9.2-10.2 LW away
  the 19th modes of the upper f2 sideband are 0.3-1.8 LW away
  We found that this coincidence of the resonance can be corrected by shortening the cavity round-trip by 0.5mm

- Spot positions (I)
The spots on the curved mirrors were ~1mm too much inside (FM side). In order to translate the cavity axis,
  MM2 and MM4 were pushed by θ
  θ/2.575 = 1mm ==> θ = 2.6 mrad
  The separation of the micrometers are ~20mm
  d/20mm = 2.6mrad ==> d = 52um

  1div of the micrometer corresponds to 10um => 5div = 50um

- Move the micrometers and adjusted the input steering to recover the alignment.

- In any case we were confident to adjust the FSR/TMS/spot positions only with the micrometers

BS1/FM1/FM2 gluing

- Aligned the cavity

- Glued BS1/FM1/FM2 one by one while the cavity resonance was maintained.
  FM2 was slipping as the table is not leveled well and the fixture was not supporting the optic.

  FSR: 264.964875MHz => 1.13144m (Exactly 0.5mm shorter!)
  TMS(V): 58.0225MHz => gamma_V = 0.218982
  TMS(H): 58.1225MHz => gamma_H = 0.219359
  the 9th modes of the carrier is 10.3~11.7 LW away
  the 13th modes of the lower f2 sideband are 7.4~9.3 LW away
  the 19th modes of the upper f2 sideband are 1.5~4.4 LW away

- Spot positions (II)
  Looked OK.

CM2 gluing

- Glued CM2. The mirror was supported from the back with allen keys.

FSR: 264.9665625MHz => 1.13144m
  TMS(V): 58.1275MHz => gamma_V = 0.219377
  TMS(H): 58.0813MHz => gamma_H = 0.219202
  the 9th modes of the carrier is 10.2~10.9 LW away
  the 13th modes of the lower f2 sideband are 8.5~9.4 LW away
  the 19th modes of the upper f2 sideband are 1.4~2.7 LW away

- Spot positions (III)
  Looked slightly off at CM2. Pushed MM2 by 4um.

CM1 gluing

- Glued CM1.

FSR: 264.964875MHz => 1.13144m
  TMS(V): 58.06625MHz => gamma_V = 0.219145
  TMS(H): 58.08625MHz => gamma_H = 0.219220
  the 9th modes of the carrier is 10.8~11.1 LW away
  the 13th modes of the lower f2 sideband are 8.2~8.6 LW away
  the 19th modes of the upper f2 sideband are 2.6~3.2 LW away

- Spot positions (final confirmation)
  Looked OK. 

Final measurement

- After everything was finished, more detailed measurement has been done.

- FSR&TMS (final)
FSR: 264.963MHz => 1.13145m
  TMS(V): 58.0177MHz => gamma_V = 0.218966
  TMS(H): 58.0857MHz => gamma_H = 0.219221
  the 9th modes of the carrier is 10.8~11.7 LW away
  the 13th modes of the lower f2 sideband are 7.3~8.6 LW away
  the 19th modes of the upper f2 sideband are 2.6~4.5 LW away

Final values for the micrometers

  • MM1: The one closest to the input mirror (CM1) 0.78mm
  • MM2: The other one on CM1 0.89
  • MM3: The one closest to the output mirror (CM2) 0.90
  • MM4: The other one on CM2 0.90

0.90         0.78
0.90         0.89


Attachment 1: Cav_scan_response_130412_Pitch.pdf
Attachment 2: Cav_scan_response_130412_Yaw.pdf
  155   Thu Aug 22 15:34:03 2013 KojiOpticsGeneralOMC Cavity side gluing

[Koji Jeff]

o BS1, FM1, FM2 prisms were glued
=> This fixed the unstability of the OMC locking

o Checked the spot position on the curved mirrors.

The height of the template was measured to be 6.16mm.
Using a sensor card, the heights of the spots on the curved mirrors were measured to be 7.4mm (CM1) and 7.9mm (CM2).
This means that the beam is ~1.5mm too low.

When the post clamps were applied to the PZT assemblies, the spot positions moved up a little bit (7.9mm - CM1, 8.2mm - CM2).
This is still ~1mm too low.

We can accommodate this level of shift by the curved mirror and the prisms.
We'll try other PZT assemblies to see if we can raise the beam height.

  235   Thu Aug 20 01:35:01 2015 KojiElectronicsGeneralOMC DCPD in-vacuum electronics chain test

We wanted to know the  transimpedance of the OMC DCPD at high frequency (1M~10M).
For this purpose, the OMC DCPD chain was built at the 40m. The measurement setup is shown in Attachment 1.

- As the preamp box has the differential output (pin1 and pin6 of the last DB9), pomona clips were used to measure the transfer functions for the pos and neg outputs individually.

- In order to calibrate the measurements into transimpedances, New Focus 1611 is used. The output of this PD is AC coupled below 30kHz.
This cutoff was calibrated using another broadband PD (Thorlabs PDA255 ~50MHz).

Result: Attachment 2
- Up to 1MHz, the transimpedance matched well with the expected AF transfer function. At 1MHz the transimpedance is 400.

- Above 1MHz, sharp cut off at 3MHz was found. This is consistent with the openloop TF of LT1128.


Attachment 1: OMC_DCPD_Chain.pdf
Attachment 2: OMC_DCPD_Transimpedance.pdf
  236   Wed Aug 26 11:31:33 2015 KojiElectronicsGeneralOMC DCPD in-vacuum electronics chain test

The noise levels of the output pins (pin1/pin6) are measured. Note that the measurement is done with SE. i.e. There was no common mode noise rejection.

Attachment 1: OMC_DCPD_OutputNoise.pdf
  623   Mon Sep 18 15:08:26 2023 Thejas OpticsGeneralOMC HEPA enclosure filter fan speed

I went in lab today and turned the HEPA filter (clsoe to the entrance) to high since we are not doing any measurements at the moment. 



  586   Thu Aug 3 09:42:36 2023 ThejasOpticsGeneralOMC Lab HEPA air filter noise

Koji mentioned that previously sarisfactory particle count was not acheived with the Med/Med HEPA filter setting once the enclosure was expanded, so a higher setting was used. This imparted noise to the cavity from the turbulent air flo. We noticed that the noise level in the laser control signal reduced with turning the HEPA filter next to the entrance to low and the current setting is Low/High. The particle count is zero (as below).



Yesterday, we measured the particle count in the enclosure to ensure that the lower setting on one of the HEPAs is still acceptable. The particle count is still zero for all measured particle sizes (0.3um, 0.5um, 1.0um, 2.0um, and 5.0um).

We also relocked the cavity and repeated the optimization efforts in https://nodus.ligo.caltech.edu:8081/OMC_Lab/584. The reflected signal was around 110mV (compared to 80mV on Tuesday).

We used a CCD camera to view the beam spots on the curved mirrors (pictures attached). We will compare the spot positions to the scatter plots for these mirrors and try to steer the beam spots accordingly.
(*Note: We did see some stray light scattering on the edge of FM2. We will further examine this and see where the stray light is coming from.)



  487   Sat Feb 4 03:33:22 2023 KojiGeneralGeneralOMC Lab Inventory

Attachment 1: North Cabinet 2nd from the left

Attachment 2: North Cabinet 3rd from the left

Attachment 3: South Cabinet (right)

Attachment 1: PXL_20230204_072749311.jpg
Attachment 2: PXL_20230204_072744686.MP.jpg
Attachment 3: PXL_20230204_073603041.MP.jpg
  503   Tue Mar 7 23:00:16 2023 Thejas OpticsCharacterizationOMC Lab clean up

Today, Koji and I cleaned up the the lab space and made some space on the optical table for radius of curvature measurement of the A+ OMC curved mirrors. 



  553   Thu Jul 6 10:19:23 2023 Thejas GeneralCharacterizationOMC Lab optic table

[Camille, Thejas]

The optics table in OMC lab was cleaned up, cameras and photodiodes used to measure the reflected and transmitted beam were unmounted to make space for the new cavity. The input beam for the new cavity is injected from the short side (unlike the long side previously) of the breadboard. A 45deg mirror was mounted to redirect the beam. Next step: Cavity assembly 

  414   Fri Jul 15 22:14:14 2022 KojiGeneralGeneralOMC Lab recovery for the OMC #002 test

- 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).

Attachment 1: PXL_20220716_035922673.jpg
Attachment 2: PXL_20220716_025319391.MP.jpg
Attachment 3: PXL_20220716_025334324.jpg
Attachment 4: PXL_20220716_035309066.jpg
Attachment 5: PXL_20220716_035411435.NIGHT.jpg
  43   Thu Nov 29 21:18:23 2012 KojiOpticsGeneralOMC Mounting Prisms have come



  382   Tue Oct 22 10:25:01 2019 StephenGeneralGeneralOMC PZT Assy #9 and #10 Production Cure Bake

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.


Attachment 1: OMC_ABO_PZT_Curing_Bake_effort_201906_thru_201909.xls
Attachment 2: production_cure_bake_pzt_assys_9_and_10_20190927.png
  1   Fri Jun 15 15:45:49 2012 KojiGeneralGeneralOMC Plan

LIGO Document G1200683-v1:
aLIGO OMC fabrication and testing plan

aLIGO OMC wiki

  108   Thu Apr 11 15:10:22 2013 KojiGeneralGeneralOMC Progress

[Zach, Jeff, Koji]

- Jeff configured the bottom side template to have a nominal value
obtained from the solid works model. Note that the thickness of the
curved mirrors are 6mm in the model. He added 0.3mmx2 to the dimensions.

- Jeff located the template on the breadboard such that each side has
the same amount of hanging out.

- Micrometer values

  • The one closest to the input mirror (CM1) 0.07
  • The other one on CM1 0.24
  • The one closest to the output mirror (CM2) 0.17
  • The other one on CM2 0.30

0.17         0.07
0.30         0.24

- Now the template is ready to accept the OMC optics.


- Zach and Koji finished a series of measurements for the test OMC.

Modulation depth:

- We scanned the laser PZT and recorded the data.
CH1: Reflection DC
CH2: PDH Error
CH3: Transmission (Magnified)
CH4: Transmission

- We should be able to obtain the estimation of the modulation depth and the finesse from this measurement.

- Rough calculation of the modulation depth is 0.19


- Incident 16.3mW
- Transmission 15.1mW
- This gave us the raw transmission of 92.6%ish.
- The modulation depth of 0.19 corresponds to 1.8% of the incident power
- The carrier reflection is almost dominated by the mode mismatch. (Note: We did not have a good resolution for the refl beam)  =>3.2%

- In total:The incident useful carrier power was 15.4mW ==> Throughput 98%
- There is slight headroom to increase the transmission by cleaning the mirrors.


- As our AOM is not functioning now, phase modulation sidebands are injected with the BBEOM.
- In principle, we can't expect any signal at the transmission at around the FSR frequency.
- If we apply small locking offset, the split peaks appear at the FSR frequency. The frequency of the dip corresponds to the FSR.
- We probably can extract the finesse of the cavity from this measurement. Lisa is working on this.


- The same PM injection gives us the frequency of the HOMs.
- We found that our EOM can work until ~500MHz.
- We could characterize the cavity resonance structure more than a single FSR.

  277   Tue May 16 19:05:18 2017 KojiOpticsConfigurationOMC SN002 fix - temporary optics

Working on the SN002 OMC fix. Checked the inventory. I think I am using C8 mirror as the new temporary CM1 and PZT24 as the new temporary CM2.

  70   Thu Mar 14 17:06:21 2013 KojiMechanicsGeneralOMC SUS work @LLO

EDIT (ZK): All photos on Picasa. Also, I discovered that since Picasa was migrated to Google+ only,
you no longer have the option to embed a slideshow like you used to. Lame, Google.

Photos sent from Zach



  25   Tue Oct 9 05:03:15 2012 KojiElectronicsGeneralOMC Test Electronics Setup


Attachment 2: electronics_setup.pdf
  24   Tue Oct 9 04:59:24 2012 KojiOpticsGeneralOMC Test Optical Setup



Attachment 2: OMC_test_setup.pdf
  81   Mon Mar 25 19:31:16 2013 KojiOpticsGeneralOMC Top-side gluing

[Koji Jeff Zach]









  69   Thu Mar 7 15:53:47 2013 KojiMechanicsGeneralOMC Transportation fixture, OMC PD/QPD mounts






ELOG V3.1.3-