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  16011   Fri Apr 9 20:54:54 2021 YehonathanUpdateBHDSOS assembly

Today I assembled the skeleton of 6 towers, without clamps and sensor assembly (attachment 1).

Some of the side plates have this weird hole that doesn't fit any of the suspension blocks (attachment 2). I didn't notice when I counted the parts and now there are exactly enough side plates to assemble 7 towers.

Also found that one of the stiffener plates has a broken threading.

We will need more parts to go beyond the necessary 7 SOSs. I will do the recounting later.

Things to do next:

1. Find the capped spring plungers and send them to C&B.

2. Assemble the clamps onto the suspension blocks.

3. Push some Viton tips into the vented screws we got to make safety stops.

4. more C&B: Magnets, dumbells, dowel pins, OSEMs.

5. Push clean dowel pins into the last suspension block.

6. Assemble 7th Tower.

7. Assemble safety stops and clamps.

8. Glue magnets to dumbells.



Attachment 1: 20210409_202717.jpg
Attachment 2: 20210409_202755.jpg
  16018   Mon Apr 12 17:30:11 2021 YehonathanUpdateBHDSOS assembly

Today, I screwed the plungers on the sensor plates and installed them on the Towers. I also installed the wire clamps on the suspension blocks (attachment).

I ran into problems in 2 separate suspension blocks: one had a dowel pin that was slightly too fat for the wire clamp. In another, the tapped holes were too short so that the 4-40 screws couldn't be screwed all the way.


Attachment 1: 20210412_170913.jpg
  16111   Mon May 3 16:49:04 2021 YehonathanUpdateBHDSOS assembly

I found a "vice" in the cleanroom (attachment 1). I used it to push dowel pins into the last suspension block using some alcohol as a lubricant.

I then assembled the 7th and last suspension tower (attachment 2).

Things that need to be done:

1. Push Viton tips into vented screws and assemble the earthquake stops.

2. Glue magnets to dumbells.

Attachment 1: 20210503_161422.png
Attachment 2: 20210503_161456.jpg
  16170   Tue Jun 1 16:17:06 2021 YehonathanUpdateBHDSOS assembly

I tried to push the clean Viton tips into the vented screws just to find out that the vented holes are too small. We need to drill 0.1" diameter holes about 0.1" deep into these screws and clean them again.


  16172   Wed Jun 2 01:03:19 2021 KojiUpdateBHDSOS assembly

Can you just cut the viton tips smaller? If you cut it to have some wedge (or say, taper), it can get stuck with the vent hole.


  16215   Fri Jun 18 19:02:00 2021 YehonathanUpdateBHDSOS assembly

Today I glued some magnets to dumbells.

First, I took 6 magnets (the maximum I can glue in one go) and divided them into 3 north and 3 south. Each triplet on a different razor (attachment 1).

I put the gluing fixture I found on top of these magnets so that each of the magnets sits in a hole in the fixture. I close the fixture but not all the way so that the dumbells get in easily (attachment 2).

I prepared EP-30 glue according to this dcc. I tested the mixture by putting some of it in the small toaster oven in the cleanroom for 15min at 200 degrees F.

The first two batches came out sticky and soft. I discarded the glue cartridge and opened a new one. The oven test results with the new cartridge were much better: smooth and hard surface. I picked up some glue with a needle and applied it to the surface of 6 dumbells I prepared in advance. I dropped the dumbells with the glue facing down into the magnet holes in the fixtures (attachment 3). I tightened the fixture and put some weight on it. I let it cure over the weekend.

I also pushed cut Viton tips that Jordan cleaned into the vented screws. While screwing small EQ stops into the lower clamps I found some problems. 4 of the lower clamps need rethreading. This is quite urgent because without those 4 clamps we don't have enough SOS towers. Moreover, I found that the screws that we bought from UC components to hold the lower clamps on the SOS towers were silver plated. This is a mistake in the SOS schematics (part 23) - they should be SS.

Attachment 1: 20210618_115017.jpg
Attachment 2: Untitled_2.png
Attachment 3: 20210618_160041_HDR.jpg
  16216   Fri Jun 18 23:53:08 2021 KojiUpdateBHDSOS assembly

Then, can we replace the four small EQ stops at the bottom (barrel surface) with two 1/4-20 EQ stops? This will require drilling the bottom EQ stop holders (two per SOS).


  16221   Tue Jun 22 17:05:26 2021 YehonathanUpdateBHDSOS assembly

According to the schematics, the distance between the original EQ tap holes is 0.5". Given that the original tap holes' diameter is 0.13" there is enough room for a 1/4" drill.


Then, can we replace the four small EQ stops at the bottom (barrel surface) with two 1/4-20 EQ stops? This will require drilling the bottom EQ stop holders (two per SOS).



  16227   Mon Jun 28 12:35:19 2021 YehonathanUpdateBHDSOS assembly

On Thursday, I glued another set of 6 dumbells+magnets using the same method as before. I made sure that dumbells are pressed onto the magnets.

I came in today to check the gluing situation. The situation looks much better than before. It seems like the glue is stable against small forces (magnetic etc.). I checked the assemblies under a microscope.

It seems like I used excessive amounts of glue (attachment 1,2). The surfaces of the dumbells were also contaminated (attachment 3). I cleaned the dumbells' surfaces using acetone and IPO (attachment 4) and scratched some of the glue residues from the sides of the assemblies.

Next time, I will make a shallow bath of glue to obtain precise amounts using a needle.

I glued a sample assembly on a metal bracket using epoxy. Once it cures I will hang a weight on the dumbell to test the gluing strength.

Attachment 1: toomuchglue1.png
Attachment 2: toomuchglue2.png
Attachment 3: dirtydumbell.png
Attachment 4: cleandumbell.png
Attachment 5: assembly_on_metalbracket.png
  16229   Tue Jun 29 20:45:52 2021 YehonathanUpdateBHDSOS assembly

I glued another batch of 6 magnet+dumbell assemblies. I will take a look at them under the microscope once they are cured.

I also hanged a weight of ~150g from a sample dumbell made in the previous batch (attachments) to test the magnet+dumbell bonding strength.

Attachment 1: 20210629_135736.jpg
Attachment 2: 20210629_135746.jpg
  16235   Thu Jul 1 16:45:25 2021 YehonathanUpdateBHDSOS assembly

The bonding test passed - the weight still hangs from the dumbell. Unfortunately, I broke the bond trying to release the assembly from the bracket. I made another batch of 6 dumbell+magnet.

I used some of the leftover epoxy to bond an assembly from the previous batch to a bracket so I can test it.

  16259   Tue Jul 27 17:14:18 2021 YehonathanUpdateBHDSOS assembly

Jordan has made 1/4" tap holes in the lower EQ stop holders (attachment). The 1/4" stops (schematics) fit nicely in them. Also, they are about the same length as the small EQ stops, so they can be used.

However, counting all the 1/4"-3/4" vented screws we have shows that we are missing 2 screws to cover all the 7 SOSs. We can either:

1. Order new vented screws.

2. Use 2 old (stained but clean) EQ stops.

3. Screw holes into existing 1/4"-3/4" screws and clean them.

4. Use small EQ stops for one SOS.


Also, I found a mistake in the schematics of the SOS tower. The 4-40 screws used to hold the lower EQ stop holders should be SS and not silver plated as noted. I'll have to find some (28) spares in the cleanroom or order new ones.


Attachment 1: 20210727_154506.png
  16260   Tue Jul 27 20:12:53 2021 KojiUpdateBHDSOS assembly

1 or 2. The stained ones are just fine. If you find the vented 1/4-20 screws in the clean room, you can use them.

For the 28 screws, yeah find some spares in the clean room (faster), otherwise just order.

  16262   Wed Jul 28 12:00:35 2021 YehonathanUpdateBHDSOS assembly

After receiving two new tubes of EP-30 I resumed the gluing activities. I made a spreadsheet to track the assemblies that have been made, their position on the metal sheet in the cleanroom, their magnetic field, and the batch number.

I made another batch of 6 magnets yesterday (4th batch), the assembly from the 2nd batch is currently being tested for bonding strength.

One thing that we overlooked in calculating the amount of glue needed is that in addition to the minimum 8gr of EP-30 needed for every gluing session, there is also 4gr of EP-30 wasted on the mixing tube. So that means 12gr of EP-30 are used in every gluing session. We need 5 more batches so at least 60gr of EP-30 is needed. Luckily, we bought two tubes of 50gr each.

  16359   Thu Sep 23 18:18:07 2021 YehonathanUpdateBHDSOS assembly

I have noticed that the dumbells coming back from C&B had glue residues on them. An example is shown in attachment 1: it can be seen that half of the dumbell's surface is covered with glue.

Jordan gave me a P800 sandpaper to remove the glue. I picked the dumbells with the dirty face down and slid them over the sandpaper in 8 figures several times to try and keep the surface untilted. Attachment 2 shows the surface from attachment 1 after this process.

Next, the dumbells will be sent to another C&B.

Attachment 1: dumbell_before.png
Attachment 2: dumbell_after.png
  16426   Tue Oct 26 10:17:14 2021 YehonathanUpdateBHDSOS assembly

Things that I need to start suspending optics:

1. Winch adapter plate (D970314). Might need to make one.

2. Quad photodetector

3. Camera and camera mount

4. Beam height target

5. Height gauge

  16439   Thu Oct 28 23:13:19 2021 YehonathanUpdateBHDSOS assembly

{Tega, Yehonathan, Koji}

Suspension of a Dummy Optic

We gathered the components needed for suspending a 2" optic housed in a 3" ring adapter:

1. SOS Tower

2. Winches+Winch adapter plate (Attachment 3)

2. HeNe Laser + Power supply

3. A steering mirror

4. QPD + ND2 Filter + Electronic amplifier

5. Oscilloscope

6. Dummy optic housed in a ring adapter (Attachment 2)

An OpLev was built using the HeNe laser, steering mirror, suspended optic, QPD (Attachment 1).

The beam height was set with a ruler. The QPD was placed in front of the laser and its height was adjusted until the Y signal vanished.

The beam was made parallel to the table. First, roughly by using an iris. Then, more accurately, by measuring the beam directed at the suspended optic with the QPD and zeroing the Y signal by adjusting the steering mirror.

We suspended the dummy optic using a music wire we found in the cleanroom cabinet.

All the wire clamps on the ring adapter, SOS, and winches were loosened.

About 0.5m of music wire was cut. Then, the wire was threaded through the wire clamp on the adapter side block, around the ring adapter, and through the wire clamp on the other side block, keeping the wire untwisted. The optic was put on the safety stop and the height was roughly adjusted using the lower EQ stops.

The wire pair was then threaded through the wire clamp on the suspension block and held near the winches. The wire was made to go through the groves at the side blocks. The wire was clamped to the side blocks. The wires were clamped on the winches. The wires were pulled by the winches until the magnet marking on the side blocks was centered on the OSEMs' holes on the side plates of the SOS (attachment 4).

Once the heights were set, the wire was clamped at the suspension block.

We balanced the dummy optic using a counterweight.

We placed the QPD at the laser reflection from the optic. We adjusted the screw set going through the counterweights to adjust the balance. The pitch imbalance was monitored by observing the Y signal on the oscilloscope.


1. Turns out that for a 1/4" thick optic, the rear counterweight needs to be removed for achieving balance.

2. To fix the counterweight on the setscrew we will use some epoxy.

3. Seems like the left optical table in the cleanroom is slightly tilted. We need to fix it.

4. The bottom long EQ stop is not touching the adapter due to the balancing mass socket. We might want to put a nut on it.

5. Still need to glue 3 more side magnet+dumbell assemblies to rods and then glue them before gluing them to the side blocks which will take at least 2 more days until we can start suspending a real optic.

Attachment 1: OpLev_Setup.jpg
Attachment 2: suspended_optic.png
Attachment 3: 20211029_113011.jpg
Attachment 4: 20211029_113052.jpg
  16443   Tue Nov 2 15:02:03 2021 YehonathanUpdateBHDSOS assembly

{Yehonathan, Tega}

We took the free-swinging spectra of the OpLev in the X and Y direction.

To make the motion of the optic quiet we turned off the airflow on the optical bench and moved the QPD close to the SOS so that the laser beam stays more or less within the QPD sensitive area.

In the process, we realized that the cleanroom HeNe went bad. It turned off after a few minutes after turning it on. The behavior repeated with another power supply. We replaced the HeNe and realigned it coarsely.

The data was taken using an oscilloscope while the optic was swinging freely. The PSD was calculated afterward (attachment 1).

Surprisingly, the pitch has a resonance frequency of ~ 2.5 Hz. And this is after we removed the back counterweight.

Additionally, we aligned the tilt of the optical table. Using a spirit bubble we adjusted the tilt by using a wrench on the table legs. As we suspected, the table was slightly tilted in the north-south direction.

Attachment 1: FreeSwingingSpectra.pdf
  16446   Tue Nov 2 22:50:30 2021 KojiUpdateBHDSOS assembly

2.5Hz is surprising. Can you move it down to sub 1Hz by adding a socket cap screw at the top instead of the set screw for the Teflon piece? How much mass do you need to add?

  16456   Mon Nov 8 17:22:27 2021 YehonathanUpdateBHDSOS assembly

Big Gluing Day

Today I glued the magnet+dumbell assemblies on the optics adapters.

Unlike magnet gluing on a 3" optic where one can use a magnet gluing fixture, here I had to position the magnets manually. There is a complication though: the magnet is much heavier than the dumbell making it almost impossible gluing the dumbell side down onto the adapter since it is very unstable in this position. A workaround is to put the magnets on some paramagnetic sheet so that the magnets stick to it and then flip it over and glue it on the adapter dumbell sides down.

The problem here is that I need to position the magnets relatively accurately on the metal sheet. To make things slightly easier I printed some drawings of the positions of the magnet, laminated them, and cleaned them to have a decent starting point (attachment 1).

For each adapter:

1. I applied glue to the 4 circular grooves at the back of the adapter.

2. I picked 4 magnets (2 north, 2 south). Trying to match their strength.

3. Made a note of which magnets I picked for which adapter in the magnet+dumbell spreadsheet.

4. Clean the dumbells' surfaces when necessary.

5. Put the magnets on a laminated magnet-positions-drawing on a metal sheet that was precleaned in the right order.

6. Flip the metal sheet and position it on the adapter such that the dumbells go as precisely as possible into the circular grooves on the adapater.

7. Adjust the magnets' positions by pushing them slightly with a non-magnetic tip.

Attachment 2 shows the numbering on the adapters for future tracking.

I also glued some magnets and aluminum rods to side blocks. Next gluing session I will glue magnets to the aluminum rods. Probably some dumbells will not stick well to the adapters. These will have to be cleaned and reglued as well.



Attachment 1: Magnets_Positions.png
Attachment 2: Adapters_Order.png
  16459   Tue Nov 9 11:11:37 2021 YehonathanUpdateBHDSOS assembly

The gluing was mostly successful. Only two magnets didn't stick (see attachment).

Attachment 1: 20211109_110408.jpg
  16465   Fri Nov 12 23:47:29 2021 YehonathanUpdateBHDSOS assembly

{Tega, Yehonathan}

First attempt at the suspension of a Lambda Optic mirror

We found the box with the 2" Lambda Optic mirrors in the cleanroom. We choose to suspend a mirror with a ROC = 5m, probably LO1.

The mirror was put inside an adapter that was prepared beforehand, put the mirror in place by tightening the Teflon rod, and then clamp it using the clamping pads.

We decided to cut two wires and clamp them to the side blocks of the adapter, while it sits on the EQ stops. The wires were threaded through the winches' clamps, through the wire clamp on the suspension block, and through the side blocks' wire clamps. We adjusted the wire position while pulling on it. The wire was made to sit inside the wire grooves on the side blocks. While tightening the clamp on the side block with the magnet, the LN key fell knocking off two magnets from the back of the adaptercrying.

Next time we think it might be a better idea to do all the adapter wire clamping on the table instead of on the SOS tower.

In the meanwhile, here are some pictures from today.


  16470   Tue Nov 16 17:42:46 2021 YehonathanUpdateBHDSOS assembly

{Tega, Yehonathan}

Another attempt at the suspension of a Lambda Optic mirror

The lambda mirror was removed from the adapter whose magnets were knocked off. We tried to mount the mirror on a different adapter but we knocked off magnets from two adapters crying. We succeeded in mounting the mirror at the third attempt (Adapter number 6). In the meanwhile, Tega threaded wires through side blocks separated from the adapter. He positioned the wires inside the grooves of the side block under a microscope (attachment 1). This procedure is much more accurate and pain-free than doing it on the suspended mirror.

We took the adapter and put it on the EQ stops. The wires were threaded through the wire clamp on the suspension block and clamped at the winches.

The adapter was rotated until the side magnet was roughly at the center of the side OSEM port. We then, as before, put coils in OSEM ports and try to adjust the height of the side magnet and the magnet groove on the other side block such that they are roughly at the center of the coil. We used the winches for fine adjustment.

I used the Canon camera to make sure the side blocks are leveled (attachment 2). I used the macro lens for that purpose. I set up a live stream from the Canon camera using these instructions only that I use OBS instead of CamTwist. I painted a semi-transparent green rectangle to annotate the position of the side magnet socket (attachment 3). I did this several times to confirm the repeatability of the results. Again using the winches for fine adjustments.

Once the height of the side magnets was confirmed to be leveled. I clamped the wires to the suspension block and cut them above it.

I tried to balance the optic but again I see that the suspensions are hysteretic. I check to see whether the wire is touching anything and indeed it touches the corner of the side blockcryingcryingcrying (attachments 4, 5).




Attachment 1: 20211115_170320_HDR.jpg
Attachment 2: 20211116_163846.jpg
Attachment 3: magnet_height_check(1).png
Attachment 4: side_blcok_touching_1.png
Attachment 5: side_blcok_touching_2.png
  16471   Tue Nov 16 18:28:53 2021 KojiUpdateBHDSOS assembly

Yehonathan told me that the wires are touching between the clamps! I went back to the CAD and confirmed it is really happening. Sad.

The distance of the wires at the upper clamp is 17.018mm.
The distance of the lower clamps is 74.168mm
The vertical drop of the wire is 251mm
--> The wire angle from the vertical line is 0.114 rad

The lower wire block has a step of 1.016mm with the vertical extension of the piece by 11.684mm
--> The angle clearance of the lower clamp is 0.087 rad

So the clearance was not enough.

If we cut the top center of the wire block more than 2.77mm, we can make the wires free.
For safety, we can cut 0.25" = 6.35mm. This will give 0.4mm clearance between the block and the wire at the closest point.

I did this modification on the 3D model and modified the 2D drawing too, so that we can find the machine shop to do it quickly.

Attachment 1: D2100546_Wire_Block.pdf
Attachment 2: D2100546_Wire_Block.png
  16483   Wed Nov 24 14:15:15 2021 YehonathanUpdateBHDSOS assembly

Late update. We got 2 modified side blocks from Jordan a few days ago. Yesterday, I glued a side magnet to one of the modified side blocks.

I took the opportunity to reglue some magnets that were knocked off from the adapters. I did this for 2 adapters only since w need 4 shallow adapters and we already had 2 complete ones.

Today, Jordan gave us the rest of the modified side blocks clean and baked. We are ready to suspend a mirror today.

  16489   Wed Dec 1 12:57:08 2021 YehonathanUpdateBHDSOS assembly

{Yehonathan, Tega}

We glued some magnets onto modified side blocks. We followed pretty much the same procedure form last time. The music wires were clamped on the side blocks away from the optic adapter. The clamps were screwed down using the low profile screws the Jordan obtained from UC components to allow maximum clearance for the coils (Attachment 2).

The modified side blocks with wires already clamped in them were screwed onto the adapter. We put the adapter on the EQ stops and do rough adjustments, making sure the side magnet is roughly on the center of a coil we inserted to the side. The wires were threaded through the wire clamp on the suspension block and clamped on the winches. We realigned the Oplev beam such that it is parallel to the table using the quad photodiode.

We balanced the height of the adapter. This time we used a camera facing the adapter. The tilt of the camera was set by drawing a straight line (red line in attachment 1) such that the bottom clamps on the SOS are parallel to it.

Then, we adjusted the winches such that the screws on the side blocks are on the same green line on attachment 1.

Once the height was adjusted, we clamped the wire on the suspension block and cut it at the winches.

We balanced the optic. We had to take out the front counterweight to get the balance (attachment 3).

We checked whether the wire is touching anything. We confirmed that it doesn't. The wire goes nicely through the new hole on the side blocks (attachment 4, 5).

We measure the resonance frequency for both yaw (attachment 6) and pitch (attachment 7). They both seem to be sub-Hz. The pitch trace also shows that the oscillations are centered around 0 meaning the optic is balanced.

There's still the issue of what to do with the lower back EQ stop not touching the adapter.

Attachment 1: SOS_Roll_Balance.png
Attachment 2: IMG_20211201_120041570.jpg
Attachment 3: IMG_20211201_115551005.jpg
Attachment 4: IMG_20211201_115640728.jpg
Attachment 5: IMG_20211201_115454629.jpg
Attachment 6: IMG_20211201_115717907.jpg
Attachment 7: Pitch_oscillations.png
  16491   Mon Dec 6 18:23:04 2021 YehonathanUpdateBHDSOS assembly

I installed OSEMs on the LO1 SOS. To my surprise, the side magnet is not in the center of the side OSEM. It completely misses the LED as can be seen in the attachment.

Looking at the CAD model, it turns out the position of the OSEM on the left side plate is different from the position of the OSEM on the right side plate in the SOS tower.

We need to take the optic down, swap the right and left side blocks, and resuspend it.

There is not enough 🤦🏻‍♂️in the world

Attachment 1: signal-2021-12-06-165751_001.jpeg
  16497   Thu Dec 9 21:57:35 2021 YehonathanUpdateBHDSOS assembly

{Yehonathan, Tega}

We took the optic out of the SOS tower and removed the side blocks. We mounted new side blocks with wires already clamped in them in the reverse order.

The Adapter was placed back into the SOS and the wires were threaded through the wire clamp and suspended on the winches. The roll of the optic was balanced using a camera (attachment 1).

The pitch was balanced. this time I used 2 counterweights instead of 1 in order to not have to take so much of the weight out.

The mechanical resonances were measured by taking a 100 sec time series of QPD readout and doing PSD estimation (attachment 2). The mirror motion was damped as much as possible before taking the measurement.

3 peaks below 1.5Hz can be seen with frequencies of 755mHz (Yaw), 942mHz, 1040mHz (Pitch + Pos). The pitch/pos peaks are a bit close to each other, I bet if we go back to 1 counterweight the situation will be better.

While inserting the side OSEM I realized I didn't check the overall height of the adapter. The magnet was too high. I will fix it tomorrow and repeat the roll balancing.


Attachment 1: balancingsos2.png
Attachment 2: FreeSwingingSpectra.pdf
  16505   Tue Dec 14 14:02:33 2021 YehonathanUpdateBHDSOS assembly

{Yehonathan, Paco}

I fixed the overall height of the adapter (attachment 1). I put an OSEM next to the side magnet. I positioned a camera in front of the SOS and connected it to my laptop for live streaming. I painted a line indicating the height of the OSEM plates and a line in between with the mean height. I discarded the wire clamp on the suspension block I released the wires from the winches and pulled on them until the magnet was roughly in the right position. I clamped the wires back on the winches and adjusted them until the magnet was on the middle line. I also verified that the roll of the adapter is aligned as before by making sure that the horizontal features on the adapter are parallel to the horizontal features on the SOS tower.

The wires were clamped to the suspension block using a new wire clamp.

I Found that locking the counterweight setscrew changes the alignment. Today we verified this effect. We released the setscrew and pre-compensated by adjusting the counterweight such that when the setscrew was locked the mirror was aligned.

We measured mechanical resonances (attachment 2). This time the yaw motion was very quiet so we got a smaller peak for the yaw. The peaks are the same as before. Y readout has peaks around the pitch and pos resonances that don't appear in the X readout. I'm not sure what they are. Maybe coming from the QPD electronics.

We locked the adapter using the EQ stops. We made sure the alignment stays close to ideal.

We installed OSEMs on the SOS. We chose suboptimal OSEMs because LO1 will only be used for steering. I made a spreadsheet copying the OSEM catalog into it. There we mark which OSEM goes where.

I cleaned the optic using the ion gun with a pressure of 30 PSI.

The next steps are:

1. Engrave the SOS tower.

2. Cut the wire at the winches and remove the winch adapter plate.

3. Wrap the SOS with foil.

4. Install the SOS in the vacuum chamber.



Attachment 1: magnetcentring.png
Attachment 2: FreeSwingingSpectra.pdf
  16511   Wed Dec 15 22:09:53 2021 YehonathanUpdateBHDSOS assembly

{Paco, Yehonathan, Anchal}

I cut the wires from the winches and removed the winch adapter plate. I engrave  'LO1' on the SOS tower. Me and Paco wrapped the SOS with foil and transported it to Anchal who put it inside the ITMX chamber.

The transportation seems to be successful. Nothing broke. However, we found that even with the short side OSEM the LO1, as it is now, cannot sit in its designed position since ITMX's side OSEM stands in its way.

If there are magnets on both ITMX sides we can move its side OSEM to the other side. Another option is to resuspend LO1 with a side magnet on its left side.


  16518   Thu Dec 16 18:16:36 2021 YehonathanUpdateBHDSOS assembly

Today I glued magnets onto the new 3/4" mirror adapters. I also took the opportunity to make some more side magnets assemblies.

Yesterday I mounted PR3/SR2 3/4" thick mirror onto one of the new adapter. There seem to be no issues for now.

I started the process of suspending AS1 (E2000226-A). The Lambda Optic mirror with the closest specs has Rc = 2 m. I attached side blocks with clamped wires onto adapter number 7 - side block with a magnet on the right.

I then took one of the Lambda Optic mirrors and tried mounting it in the adapter. It was quite difficult to get it right. Unfortunately, I chipped the edge of the substrate (attachment 1) 🤦🏻‍♂️. I put the mirror back in the box and decided to use the spare mirror. I successfully mounted it into the adapter but when I put the clamping screws one of them fell on the mirror 🤦🏻‍♂️🤦🏻‍♂️. There is no visible damage though. I took some pictures (attachment 2-4).

I and Anchal then started suspending the mirror but then we found that one of the wires is dented in the middle 🤦🏻‍♂️🤦🏻‍♂️🤦🏻‍♂️. I'm burned out for today.

Late update: one nice thing that I found yesterday is that the glue is viscous enough to hold the dumbells without a metal sheet from above holding the magnets. This greatly simplifies the gluing process.


Attachment 1: chippedmirror.png
Attachment 2: IMG_6311.JPG
Attachment 3: IMG_6310.JPG
Attachment 4: IMG_6309.JPG
  16520   Fri Dec 17 17:50:17 2021 YehonathanUpdateBHDSOS assembly

I threaded a new wire through a different side block with a magnet and clamped it under a microscope. It was hard, but eventually, I was able to do it by holding the wire on both sides of the side block with weights.

The dented wire was discarded and the side block that was mounted on the AS1 adapter was put aside. I mounted the side block with the new wire on the AS1 adapter.


Anchal and I hanged the AS1 adapter and clamped the wires on the winches of an SOS tower. I balanced the roll and adjusted the height of the magnet with respect to a side OSEM using a camera (attachments 1 & 2).

I shoot the Hene laser on the optic and look at the reflection. I align the laser beam to be as close as possible to the center of the mirror. The OpLev needs to be realigned.

To my surprise, the ghost beam shoots up above the reflected beam! See attachment 3. I check to see that the arrow which marks the thinnest side of the mirror is horizontal (attachment 4). WTF?!

Also, now I realize that the marking on the Lambda optics are pencil markings 😵😵😵.

Attachment 1: AS1rollbalance.png
Attachment 2: AS1Magnet_height.png
Attachment 3: ghostbeam.png
Attachment 4: lambdaopticarrow.jpg
  16521   Fri Dec 17 19:16:45 2021 KojiUpdateBHDSOS assembly

We @40m do the convention of the arrow at the thinnest side & pointing the HR side, but nobody says Lambda does the same.

We can just remount the mirror without breaking the wires and adjust the pitching if you do it carefully.

Does this mean that the LO1 also likely to have the wedge pointing up? Or did you rotate the mirror to have the wedge reflection to be as horizontal as possible?

  16523   Fri Dec 17 22:16:07 2021 YehonathanUpdateBHDSOS assembly

I specifically checked the specification before mounting the mirror. It says clearly "Arrow at the thinnest location pointing towards Side 1". I guess they just ignored it.

As for LO1, I mounted it without noticing the location of the arrow. Later, I checked and the ghost beam was horizontal so I left it as it is. Yeah, I guess I will remount the mirror. Also, what do we do with the pencil markings? It's not vacuum-compatible.


We @40m do the convention of the arrow at the thinnest side & pointing the HR side, but nobody says Lambda does the same.

We can just remount the mirror without breaking the wires and adjust the pitching if you do it carefully.

Does this mean that the LO1 also likely to have the wedge pointing up? Or did you rotate the mirror to have the wedge reflection to be as horizontal as possible?


  16524   Sat Dec 18 00:56:14 2021 KojiUpdateBHDSOS assembly

Sad... We just need to check the wedge direction everytime, unfortunately.

Pencil: can you try to gently wipe it off with solvent & a swab? (IPA / Acetone)
If it does not come off in the end, it's all right to leave. Do we want to scribe the arrow mark? You need a diamond pen.

  16526   Mon Dec 20 13:52:01 2021 KojiUpdateBHDSOS assembly

LO1: No need to remove the pencil mark for the damping test. Until we see serious contamination on the LO1 optic, we don't need to take the optic off from the mount and clean it. If there is a chance of rehanging (because of a broken wire/etc), we do wipe the pencil mark.

Other optics: wipe the pencil mark as much as possible.

  16528   Mon Dec 20 17:26:13 2021 YehonathanUpdateBHDSOS assembly

{Yehonathan, Anchal}

I released the AS1 wires from the winches, removed the adapter from the SOS tower, and removed the Lambda optic from the adapter. Attachment 1 shows the pencil markings on the optic before cleaning. I cleaned the pencil marking from the side of the optic with acetone using swabs until there were no pencil residues on the swab (attachment 2 shows the swab I used next to an unused swab). I was not able to remove the markings completely though (attachment 3).

I remounted the optic with the arrow rotated by 90 degrees counterclockwise.

We hang the adapter on the winches and adjust the height of the magnet and the adapter roll using the winches. We monitor the height of the adapter using a live stream from the Cannon camera. The camera's tilt was adjusted using straight features on the SOS tower. When we ran out of winch travel we adjust the height using the lower EQ stops and pull tight the wires. Attachment 4 shows the alignment of the side magnet with respect to the SOS tower and a side OSEM.

We checked the ghost beam trajectory and it looks much better (attachment 5)

We started realigning the OpLev. We realize that the height of the beam should be 5+14/32" = 5.437 by measuring the height of the screw holding the side OSEM from the table. The real height from the schematics is 5.425 We make the beam parallel with the table first using an iris and then the QPD.

Today, I balanced the counterweight. First using an iris, then by placing a QPD close to the SOS measuring the reflection from AS1. I locked the counterweight's set screw and the QPD Y readout looks good. Attachment 6 shows the QPD y readout near the beat node between pitch and pos. The node comes very close to zero which indicates that the pitch is balanced.

I measured the free-swinging motion using the QPD x and y axes. Attachment 7 shows the spectra of that motion. The major peaks are at 755mHz, 953mHz, and 1.05Hz.


Attachment 1: IMG_6312.JPG
Attachment 2: IMG_6315.JPG
Attachment 3: IMG_6314.JPG
Attachment 4: AS1adapterbalancing.png
Attachment 5: as1ghostbeam2.png
Attachment 6: beat.png
Attachment 7: FreeSwingingSpectra.pdf
  16531   Tue Dec 21 18:04:46 2021 YehonathanUpdateBHDSOS assembly

I locked the EQ stops while retaining the XY alignment on the QPD and installed 5 green OSEMs. AS1 is ready for transfer into the vacuum chamber.

  16544   Wed Jan 5 19:18:06 2022 YehonathanUpdateBHDSOS assembly -- AS4

{Paco, Yehonathan, Anchal}

Today we suspended AS4 (E2000226-B). Anchal mounted Lambda Optic mirror with an RoC closest to AS4 in a thin optic mount. He noted that this optic as well as AS1 don't have a wedge angle. The specs claim that the wedge angle is 2 degrees what should have been clearly seen by inspecting the optic with a naked eye. All the ghost beam deflections probably come from the curvature of the mirror.

We did all the height and roll balancing using a camera (Attachment 1,2). We balanced that pitch of the adapter using a QPD not before we realigned the OpLev setup.

We measured the motion spectra (attachment 3). Major peaks are found at 755 mHz, 964 mHz, and 1.062Hz. I locked the counterweights setscrew and observed that the pitch balance doesn't change. I locked the EQ stops such that the alignment of the mirror remained the same by monitoring the QPD signals. I clamped the suspensions wires to the suspension block.

The only thing remaining is inserting the OSEMs.


Attachment 1: AS4_roll_balance.png
Attachment 2: AS_4_magnet_height.png
Attachment 3: FreeSwingingSpectra.pdf
  16550   Thu Jan 6 17:00:20 2022 YehonathanUpdateBHDSOS assembly -- LO2

{Paco, Yehonathan}

Today we suspended LO2 (E1800089) which Anchal has loaded into the thick optic adapter. Attachments 1,2 show the height and roll balance adjustments.

I realigned the opLev setup and balanced the suspended mass. We figured that if we use 2 counterweights we will be 1 short. We decided to use 1 mass at the back of the adapter. This has the additional advantage that the Viton tip on lower back EQ stop can touch it and act normally. The optic was successfully balanced in this way. Attachment 3 shows the motion spectra on the QPD. There are major peaks at 712 mHz, 854 mHz, 876 mHz, and 996 mHz. As expected using only 1 counterweight raised the center of mass and lowered the pitch resonance frequency. The optic was locked keeping the alignment fixed on the center of the QPD, OSEMs were inserted and the SOS tower was engraved.

We should apply some glue to the counterweight to prevent it from spinning on the setscrew.

Attachment 1: LO2_roll_balance.png
Attachment 2: LO2_magnet_height.png
Attachment 3: FreeSwingingSpectra.pdf
  16542   Tue Jan 4 18:27:23 2022 PacoUpdateBHDSOS assembly -- PR3

[yehonathan, paco, anchal]

We continue suspending PR3 today. Yehonathan and Paco suspended the thick optic in its adapter. After fixing some nominal height and undoing any residual roll angle (see Attachments 1,2 for pictures), we noticed a problem with the pitch angle, so we insert the counterweights all the way in. Nevertheless, we soon found out that we needed to shift one of the two counterweights to the back of the adapter side (so one on each side) in order to tare the pitch angle. This is a newly experienced maneuver that may apply for further thick optics.

After taring the pitch angle roughly, we noted another issue. The wedge (~ 1 deg) on the optic made it such that the protruding socket heads on the thick side bumped against the lower clamp (not the earthquake stop tip itself). Attachments #4,5 show the before/after situation which was solved provisionally by replacing the socket head screws with lower profile (flat) head screws in situ. Again, this operation was highly delicate and specific to wedged thick optics, so for future SOS we should keep it in mind.

Another issue that we had with the new thick optic adapters is that for some reason there is a recession in the upper backside of the adapter (attachment coming soon). This makes the upper back EQ stop too short to touch the adapter. We replaced it with a longer screw. When inserted it doesn't really hit the back of the adapter. Rather, it touches the corner of the recession, stoping the optic with friction.

While all this was happening, Anchal started mounting AS4 on its adapter. After one of the magnets broke off, he switched to another one and succeeded. This is the next target for suspension. We still need to check the orientation of the wedge. Furthermore, we started a gluing session in the afternoon to prepare as much as possible for further SOS during the week. 3 side magnets were glued to side blocks. 3 magnets were glued to 3 adapters that were missing 1 magnet each.

In the afternoon, Yehonathan and Paco set up the QPD and did all the usual balancing, and then Anchal took the data of which the result is shown in Attachment #3. The major peaks are located at 723mHz, 953mHz, and 1.05Hz. Very similar to the case of the thin optic adapters.

Anchal progressed with OSEM installation, and engraving and yehonathan glued the counterweight setscrew in place. After securing the EQ stops, and wrapping the wires in foil, we declare PR3 is ready to be installed.

Attachment 1: PR3_roll_balance.png
Attachment 2: PR3_magnet_height.png
Attachment 3: FreeSwingingSpectra.pdf
Attachment 4: PXL_20220104_231742123.jpg
Attachment 5: PXL_20220104_232809203.jpg
  16568   Tue Jan 11 09:53:14 2022 not KojiUpdateBHDSOS assembly -- Peek screws and nuts

I handed the Peek parts we got from McMaster to Jordan for C&B.

  16556   Fri Jan 7 17:59:45 2022 YehonathanUpdateBHDSOS assembly -- SR2

{Yehonathan, Paco}

{Paco, Yehonathan}

Today we suspended SR2 (E1800089) which Anchal has loaded into the thick optic adapter. Attachments 1,2 show the height and roll balance adjustments.

I realigned the opLev setup and balanced the suspended mass. Attachment 3 shows the motion spectra on the QPD. There are major peaks at 723 mHz, 832 mHz, and 996 mHz. I inserted OSEMs and tightened them in place. I adjusted the OSEM plates to make sure the magnets are at the center of the OSEMs, then I tightened the OSEM plates to the SOS tower.

The optic was locked keeping the alignment fixed on the center of the QPD.

Again, we should apply some glue to the counterweight to prevent it from spinning on the setscrew. Is there a glue other than EP30 that we can use?

Related: Peek nuts, screws and washers were ordered from Mcmaster.

Attachment 1: SR2_roll_balance.png
Attachment 2: SR2_magnet_height.png
Attachment 3: FreeSwingingSpectra.pdf
  16557   Fri Jan 7 18:24:25 2022 KojiUpdateBHDSOS assembly -- SR2

Vacseal in the freezer. It could have been expired sooooo many years ago, We need some cure testing.

Can you release the part numbers of the ordered components (and how/where to use them), so that we can incorporate them into the CAD model?


Again, we should apply some glue to the counterweight to prevent it from spinning on the setscrew. Is there a glue other than EP30 that we can use?

Related: Peek nuts, screws and washers were ordered from Mcmaster.

  16561   Mon Jan 10 14:00:44 2022 not KojiUpdateBHDSOS assembly -- SR2


For the thin optics adapter design, we want Peek 1/4-20 screw (part # 98885A131) to replace the lower back long EQ stop. On it, we will have a Peek washer (part # 93785A600) fastened between two Peek nuts (part #98886A813).

For the thick optics adapter design, we want Peek 1/4-20 screw (part # 98885A131) to replace both the upper and lower back EQ stop. On the upper stop, we need a single Peek nut (part #98886A813).

I will cure-test the Vacseal.


Vacseal in the freezer. It could have been expired sooooo many years ago, We need some cure testing.

Can you release the part numbers of the ordered components (and how/where to use them), so that we can incorporate them into the CAD model?


Again, we should apply some glue to the counterweight to prevent it from spinning on the setscrew. Is there a glue other than EP30 that we can use?

Related: Peek nuts, screws and washers were ordered from Mcmaster.


  6344   Thu Mar 1 09:26:50 2012 steveUpdateSUSSOS baffle plates are ready

 Green welding glass 7" x 9"   shade #14 with 40 mm hole and mounting fixtures are ready to reduce scatter light on SOS

PEEK 450CA shims and U-shaped clips  will keep these plates damped.


Attachment 1: 03011201.PDF
03011201.PDF 03011201.PDF
  14032   Thu Jun 28 16:48:27 2018 gautamUpdateSUSSOS cage towers

For the upcoming vent, we'd like to rotate the SOS towers to correct for the large YAW bias voltages used for DC alignment of the ITMs and ETMs. We could then use a larger series resistance in the DC bias path, and hence, reduce the actuation noise on the TMs. 

Today, I used the calibrated Oplev error signals to estimate what angular correction is needed. I disabled the Oplev loops, and drove a ~0.1 Hz sine wave to the EPICS channel for the DC yaw bias. Then I looked at the peak-to-peak Oplev error signal, which should be in urad, and calibrated the slider counts to urad of yaw alignment, since I know the pk-to-pk counts of the sine wave I was driving. With this calibration, I know how much DC Yaw actuation (in mrad) is being supplied by the DC bias. I also know the directions the ETMs need to be rotated, I want to double check the ITMs because of the multiple steering mirrors in vacuum for the Oplev path. I will post a marked up diagram later. 

Steve is going to come up with a strategy to realize this rotation - we would like to rotate the tower through an axis passing through the CoM of the suspended optic in the vertical direction. I want to test out whatever approach we come up with on the spare cage before touching the actual towers.

Here are the numbers. I've not posted any error analysis, but the way I'm thinking about it, we'd do some in air locking so that we have the cavity axis as a reference and we'd use some fine alignment adjust (with the DC bias voltages at 0) until we are happy with the DC alignment. Then hopefully things change by so little during the pumpdown that we only need small corrections with the bias voltages.

SoS tower DC bias correction

EPICS excitation

[V pk-pk]

Oplev error signal readback

[urad pk-pk]

Calibration [mrad/V] Current DC bias voltage [V] Required correction [mrad]
ETMX 0.06 110 1.83 -5.5305 -10.14
ITMX 0.02 180 9 -1.4500 -13.05
ITMY 0.02 120 6 -0.3546 -2.13
ETMY 0.06 118 1.97 0.5532 1.09

Some remarks:

  1. Why the apparent difference between ITMs and ETMs? I think it's because the bias path resistors are 400 ohms on the ETMs, but 100 ohms on the ITMs
  2. If we want the series resistance for the bias path to be 10 kohm, we'd only have ~800 urad actuation (for +10V DC), so this would be an ambitious level of accuracy. 
  7331   Fri Aug 31 17:50:41 2012 SteveUpdateSUSSOS centering target

The SOS centering target is 1.9 mm lower than it should be! 

The hole is 10mm for the  ~6 mm beam




  7469   Wed Oct 3 15:58:57 2012 SteveConfigurationIOOSOS coil drivers moved

The SOS coil drivers (Atm2) were moved from 1X1 to 1Y2 location. Is this the best place to locate the  IOO Tip-Tilt steering that will replace the PJ-PZT ?

See 40m wiki T-T

Attachment 1: SOScoildriversTT.jpg
Attachment 2: IMG_1680.JPG
  6039   Tue Nov 29 17:10:39 2011 DenUpdatedigital noiseSOS creation

One of the possibilities that we see a large low-frequency digital noise is due to Foton. I've checked the SOS coefficients that saves Foton with a Matlab coefficients. I used a 3 order low-pass cheby1 filter cheby1("LowPass",3,0.1,3) 

In matlab I generated SOS model using 3 approaches 

[A,B,C,D]=cheby1(3,0.1,3/1024) % create SS form

[sos,g]=ss2sos(A,B,C,D)  % convert to SOS form

[z, p, k]=cheby1(3,0.1,3/1024) % create ZPK form

[sos,g]=zp2sos(z,p,k)  % convert to SOS form

[b, a]=cheby1(3,0.1,3/1024) % create TF form

[sos,g]=tf2sos(b,a)  % convert to SOS form

As this is a 3 order filter, in the SOS representation we'll get 2 by 6 SOS - matrix. It is presented below. In each matrix place there 4 numbers - from the Foton file and obtained using these 3 methods.







1              1.0000000000000000      #           0                                              #       1      #         -0.9911172660954457     #       0

1              1.0005663179617605      #           0                                              #       1      #         -0.9911172660954457     #       0

1              1.0000000000000000      #           0                                              #       1      #         -0.9911172660954457     #       0

1              0.9999894976396830      #           0                                              #       1      #         -0.9911172660997303     #       0


1              2.0000000000000000      #          1.0000000000000000         #       1      #        -1.9909750803252266      #      0.9911175825477769

1              1.9994336820732397      #          0.9994340026283055         #      1       #       -1.9909750803252262       #     0.9911175825477765

1              2.0000000000000000      #          1.0000000000000000         #      1       #       -1.9909750803252262       #     0.9911175825477765

1              2.0000105023603174      #          1.0000105024706190         #      1       #       -1.9909750803209423       #     0.9911175825434912


It seems that smth analog to zp2sos is used in Foton. We can see that due to representation error we have derivations in the 4 and 6 digits for SS and TF forms. This means that a pretty big mistake can run due to digital transforms even using double precision as in the Matlab test.

Alex Ivanov said that he'll fix that single precision problem and in the 2.5 release we won't have any FLOAT variables. Though we still do not understand how that variables declared as FLOAT can cause filter calculations. 

ELOG V3.1.3-