[Alena, Koji]

Jun 21: Alena and Koji worked on gluing of the CM1 mirror on the OMC breadboard #002. This is an irregular procedure. Usually, the PZT mirror subassembly is prepared before the mounting prism is glued on the breadboard. In this occasion, however, a PZT and a mirror are bonded on an existing prism because only the damaged mirror and still functional PZT were debonded from the mouting prism.

For this purpose, the mirror and the PZT were fixed on the mounting prism with the modified fixture set (D1600338). The original PZT was reused, and the new mirror #8 was used. The alignment of the mirror was checked OK using the cavity beam before any glue was applied. The arrow of the CM mirror is facing up.

We mixed 8g EP30-2 (it was almost like 3~4 pushes) and 0.4g glass sphere bond lining. Along with EP30-2 procedure, the bond was mixed in an Al pot and tested with 200degF (~93degC) preheated the oven for 15min. The cured bond showed perfect dryness and crispness. The bond was painted on the PZT and the PZT was placed on the fixture. Then more bond was painted on the other side of the PZT. The mirror was placed in the fixture. The spring-loaded front plate was fixed, and the breadboard was left for a day. (Attachment 1~3)

Jun 22: The fixture was removed without causing any visible delamination or void. The attachment 4~6 show how wet the joint is (before baking). There were some excess of EP30-2, which bonded the fixture and the mounting prism as usual. The fixture was detached by prying the front piece against the rear piece with a thin allen key. Some of the excess bond on the mounting prism was removed by scratching.

The alignment of the cavity was checked with the cavity beam and it is still fine.

More photos can be found here: Link to Google Photos Album "OMC #002 Repair - CM1 gluing"

I wondered why the black glass beam dumps looked not as shiny as before. It was in fact a layer of dusts (or contaminants) accumulated on the surface.
The top part of the internal surface of the black glass was touched by a piece of lens tissue with IPA. The outer surface was already cleaned. IPA did not work well i.e. Required multiple times of wiping. I tried FirstContact on one of the outer surface and it efficiently worked. So I think the internal surfaces need to be cleaned with FC.

[Alena, Koji]

Report of the work on June 30.

1. Cleaning of the black glass beam dumps

As reported in the previous entry, the beam dumps on the OMC breadboard exhibited accumulation of dusts or contaminants on the black glass surfaces. We worried about transfer of the dusts over a period or of the contaminant during baking. It was already known that the contaminants are persistent and not easy to remove only by drag wiping with IPA. So Alena brought a set fo tools to try. Here is the procedure described.

- Inventory (Attachment 1): A small glass beaker, TX715 Alpha® Sampling Swab, plastic brushes, syringes with pure IPA, inspection flash light, Vectra IPA soaked wipes

- Apply clean IPA on a brush. Some IPA should be removed by the IPA soaked wipe so as not to splash IPA everywhere. Rub a glass surface with the brush while the surface is inspected by the flash light. The strokes migrate the contaminants to the direction of wiping. So the brush should be moved outward. This does some cleaning, but it is not enough to remove smudges on the surface. Occasionally clean the brush with IPA poured in the small beaker.

- Apply clean IPA on a swab. Rub the surface with the swab outward. This removes most of the visible smudges.

We decided not to apply FirstContact on the beam dumps at this occasion. In any case, we need to apply FC on all the optical surfaces after the baking. We judged that the current cleanliness level of the beam dump does not affect the over all contamination of the OMC considering the FC application after the baking.

2. Gluing of the reinforcement Al bars on the delaminated Invar mounting brackets
One of the mounting bracket (=invar shim) on the top side (= suspension I/F side) showed the sign of delamination (Attachment 3). This invar is the one at the beam entrance side (Attachment 2).

EP30-2 was mixed as usual: 6g of EP30-2 was mixed with 0.3g glass sphere. The glue was tested with a cooking oven and the result was perfect. The glue was applied to two Al bars and the bars were attached on the long sides of the invar shim with the beveled corner down (to avoid stepping on the existing original epoxy) (Attachments 4, 5). The photo quality by my phone was not great. I will take better photos with a better camera next week.

Glue condition was checked on Monday Jul 3rd. It was all good. New photos were taken. OMC #002 Repair - Gluing of reinforcement AL bars

- Forgot to close the cylinder valve...

v HEPA prefilter (20"x20"x1" MERV 7)

- Replace the filter for the air conditioning

v Texwipe TX715 SWAB http://www.texwipe.com/store/p-817-tx715.aspx

v Gloves ~3 bags
VWR GLOVE ACCTCH NR-LTX SZ7.0 PK25 79999-304 x3
VWR GLOVE ACCTCH NR-LTX SZ7.5 PK25 79999-306 x1

v Vectra IPA soaked cloths

v Sticky mats

• GLOVE ACCTCH NR-LTX SZ7 PK25 / 79999-304 / PK4
• GLOVE ACCTCH NR-LTX SZ7.5 PK25 / 79999-306 / PK1
• WIPER 100% IPA 23X23CM PK50. / TWTX8410 / PK2
• SWAB CLEANTIPS ALPHA PK100. / TW-TX715 / PK1
• MAT CLEAN ROOM 18X36IN BLUE / 89021-748 / CS1 (Qty4)
• FILTER PLET AIR MERV8 20X20X1 / 78002-422 / EA4 / Direct from Supplier

ORDERED AUG 9, 2017

[Stephen Koji]

The OMC #002 was packed for the transportation to Downs.

===> And transported to Downs 227 on Jul 6th.

[Steve, Aaron, Koji]

We've finished the preparation for the forthcoming plumbing work on (nominally) Sept 16th Saturday.
We've covered most of the west side of the OMC lab with plastic sheets and wraps.

Some tips:

• The plastic sheets Eric gave us were a bit too thin and pron to got torn. Thicker sheets are preferable.
• The blue tape that Eric gave us was very useful.
• The stretch wrap film, which I bought long time ago, was so useful. Office Depot "Office Depot(R) Brand Stretch Wrap Film, 20 x 1000 Roll, Clear" PN: 445013
• We also used patches of Kitchen Trash Bags to cover some small opening of the large sheets. Office Depot "Glad(R) Tall Kitchen Trash Bags, 13 Gallon, White, Box Of 28" PN 269268

Attachment 1: The PD was removed from the transmission side of the OMC #002 (former LHO OMC - the one blasted by the optical pulse in Aug 2016).
It was confirmed that the PD has the scribing mark saying "A".

Attachment 2: This diode had no glass cap on it. The photodiode sensitive element is still intact. For ease of handling, it should be kept in a cage. There are four cages in the OMC lab, but they are ocuppied with the High QE PDs and others. So, the cage for this PD was offered by Rich from his office, meaning the cage was not clean.

Attachment 3: The sensor side is capped by a plate. This cap can be removed by unscrewing the two cap screws in the photo.

Attachment 4: The PD legs are shorted. (Just to match the style with the LLO one).

Attachment 5: Wrapped with AL foil and double bagged. (Repeat: It is not anything clean.)

Attachment 6: The bag was left on Rich's desk.

Norna Robertson, Stephen Appert ||  29 Nov 2017, 2 pm to 4 pm  ||  227 Downs, CIT

We made some preparations for modal testing, but did not have enough time to make measurements. Below is an after-the-fact log, including some observations and photos of the current state of the OMC bench.

1. Previous testing results at T1700471 (technical note in progress as of 30 Nov 2017).
   1. One goal of the next round: add damping material to equate with damping material of T1600494.
   2. Second goal of the next round: use a more localized sweep to better resolve the body mode around 1080 Hz -1100 Hz
2. Transport Fixture was opened without issue, revealing the "Top" (suspending and cable routing) surface of the bench. Damping stacks were still in place from previous testing
3. We removed the bolts from the damper stacks, but found that all masses with metal-viton interfaces had adhered to viton washers, causing the stacks to stick together.
   1. By using an allen key as a lever to wedge apart bottom mass and the bracket where they were joined by a viton washer, we separated the masses from the bracket.
   2. An allen key was used as a lever to push apart the two masses, which were also joined by a viton washer
   3. Once exposed, viton washers were pried from metal surfaces.
4. After the damper stacks had been detached from the  No viton washer appeared to leave any residue or particulate - the separated parts all appeared as clean as they had been at the onset.

The 3IFO EOM test performed at the 40m. Result: 40m ELOG 13819

Qs' were estimated with a lorentzian function (eye fit)

Current LHO EOM (final version, modulation depth measurement 2018/4/5)
f0=9.1MHz, Q=18
f0=45.38MHz, Q=46
f0=118.05MHz, Q=30

Prev LHO EOM (RF transmission measurement 2018/4/13)
f0=9.14MHz, Q=53
f0=24.25MHz, Q=55
f0=45.565MHz, Q=62;

3IFO EOM (RF transmission measurement 2018/4/23)
f0=8.627MHz, Q=53
f0=24.075MHz, Q=60
f0=43.5MHz, Q=65

Koji, Rich

We took apart the unit removed from the 3rd IFO (Unit serial number aLIGO #3, XTAL 10252004) to see what makes it tick.  Koji has done a fine job of adding the plots of the impedance data to this log book.  Attached are some details of the physical construction showing the capacitor values used in shunt before the coils.

0. If you have an RF signal whose waveform is , the amplitude is constant and 1.

1. If the waveform , the amplitude has the DC value of 1 and AM with the amplitude of 0.1 (i.e. swing is from 0.9 to 1.1). Therefore the RMS RIN of this signal is 0.1/1/Sqrt(2).

2. The above waveform can be expanded by the exponentials.

Therefore the sideband carrier ratio R is 0.025/0.5 = 0.05. This corresponds to 20 log10(0.05) = -26dBc

In total, we get the relationship of dBc and RIN as , or R = RIN/sqrt(2)

[Koji Gautam]


With Gautam's help, I ran a coating design code for an HR mirror with the standard quarter-wave design. The design used here has 17 pairs of lambda/4 layers of SiO₂ and Ta₂O₅ (=34 layers) with the fused silica as the substrate to realize the transmission of tens of ppm. At the AOI (angle of incidence) of 4 deg (=nominal angle for the aLIGO OMC), there is no significant change in the reflectivity (transmissivity). With 95% of the case, the phase difference at the AOI of 4 deg is smaller than 0.02 deg for given 1% fluctuation (normal distribution) of the layer design and the refractive indeces of the materials. Considering the number of the OMC mirrors (i.e. 4), the total phase shift between P and S pols is less than 0.08 deg. This makes P and S resonances matched well within 1/10 of the cavity resonant width (360/F=0.9deg, F: Finesse=400).

Of course, we don't know how much layer-thickness fluctuation we actually have. Therefore, we should check the actual cavity resonance center of the OMC cavity for the polarizations.

Attachment 1 shows the complex reflectivity of the mirror for P and S pols between AOIs of 0 deg and 45 deg. Below 30 deg there is no significant difference. (We need to look at the transmission and the phase difference)

Attachment 2 shows the power transmissivity of the mirror for P and S pols between AOIs of 0 deg and 45 deg. For the purpose to check the robustness of the reflectivity, random fluctuations (normal distribution, sigma = 1%) were applied to the thicknesses of each layer, and the refractive indices of Silica and Tantala. The blue and red bands show the regions that the 90% of the samples fell in for P and S pols, respectively. There are median curves on the plot, but they are not well visible as they match with the ideal case. This figure indicates that the model coating well represents the mirror with the transmissivity better than 70ppm.

Attachment 3 shows the phase difference of the mirror complex reflectivity for P and S pols between AOIs of 0deg and 45deg. In the ideal case, the phase difference at the AOI of 4deg is 1x10^-5 deg. The Monte-Carlo test shows that the range of the phase for 90% of the case fell into the range between 5x10^-4 deg and 0.02 deg. The median was turned to be 5x10^-3 deg.

Attachment 4 shows the histogram of the phase difference at the AOI of 4deg. The phase difference tends to concentrate at the side of the smaller angle.

I started some analytic calculations of how OMC mirror motion would add to the noise in the BHD. I want to make some prettier plots, and am adding the interferometer so I can also compute the noise due to backscatter into the IFO. However, since I've pushed the notebook I wanted to post an update. Here's the location in the repo.

I used Koji's soft limit of 0.02 degrees additional phase accumulation per reflection for p polarization.

I'm still not satisfied/done with the solution to this, but this has gone too long without an update and anyway probably someone else will have a direction to take it that prevents me spinning my wheels on solved or basic questions.

The story will have to wait to be on the elog, but I've put it in the jupyter notebook. Basically:

• I considered the polarization-separated OMC in several configurations. I have plots of DARM referred noise (measured free-running and controlled noise for the current OMC, thermal theoretical noise curve, scattered light) for the case of such an OMC with one lambda/2 waveplate oriented at 45 degrees. This is the base case.
• I also considered such an OMC with a lambda/2 both before and after the OMC, where their respective polarization axes can be arbitrary (I look at parameter space near the previous case's values).
  • I optimize the BHD angle to balance the homodyne (minimize the E_LO^2 term in the homodyne readout).
  • I then optimize the rotations of the lambda/2 polarization axes to minimize the noise
  • For the optimum that is closest to the base case, I also plotted DARM referred length noise.

It's clear to me that there is a way to optimize the OMC, but the normalization of my DARM referred noise is clearly wrong, because I'm finding that the input-referred noise is at least 4e-11 m/rt(Hz). This seems too large to believe. 

Indeed, I was finding the noise in the wrong way, in a pretty basic mistake. I’m glad I found it I guess. I’ll post some plots and update the git tomorrow. 

A simple COMSOL simulation was run to see how the PZT deforms as the voltage applied.

Use the geometry of the ring PZT which is used in the OMCs -  NAC2124 (OD 15mm, ID 9mm, H 2mm)
The material is PZT-5H (https://bostonpiezooptics.com/ceramic-materials-pzt) which is predefined in COMSOL and somewhat similar to the one used in NAC2124 (NCE51F - http://www.noliac.com/products/materials/nce51f/)
The bottom surface of the ring was electrically grounded (0V), and mechanically fixed.
Applied 100V between the top and bottom.

== Office Depot ==
Really Useful Box 9L x 6 (delivered)
Really Useful Box 17L x 5 (ordered 4/4)
P-TOUCH tape (6mm, 9mm, 12mmx2, 18mm) (ordered 4/4)

== Digikey ==
9V AC Adapter (- inside, 1.3A) for P-TOUCH (ordered 4/4)
12V AC Adapter (+ inside, 1A) for Cameras (ordered 4/4)

== VWR ==
Mask KIMBERLY CLARK "KIMTECH Pure M3" ISO CLASS 3 (ordered 4/4)

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

Preparation for the PZT subassembly bonding (Section 6.2 and 7.3 of T1500060 (aLIGO OMC optical testing procedure)
- Gluing fixture (Qty 4)
- Silica sphere powder
- Electric scale
- Toaster oven for epoxy mixture qualification

- M prisms
- C prisms
- Noliac PZTs

- Cleaning tools (forceps, tweezers)
- Bonding kits (copper wires, steering sticks)
- Thorlabs BA-2 bases Qty2
- Razor blades

Also brought to the 40m on 10 April, in preparation for PZT subassembly bonding:

- new EP30-2 epoxy (purchased Jan 2019, expiring Jul 2019 - as documented on documents attached to glue, also documented at C1900052.

- EP30-2 tool kit (maintained by Calum, consisting of mixing nozzles, various spatulas, etc)

Already at the 40m for use within PZT subassembly bonding:

- "dirty" ABO A with temperature controller (for controlled ramping of curing bake)

- clean work areas on laminar flow benches

- Class B tools, packaging supplies, IPA "red wipes", etc.

Upon reviewing EP30-2 procedure T1300322 (current revision v6) and OMC assembly procedure E1300201 (current revision v1) it appears that we have gathered everything required.

[Koji Stephen]

The four PZT sub-assemblies were glued in the gluing fixtures. There were two original gluing fixtures and two additional modified fixtures for the in-situ bonding at the repair of OMC(002).

- Firstly, we checked the fitting and arrangements of the components without glue. The component combinations are described in ELOG 329.
- Turned on the oven toaster for the cure test (200F).
- Then prepared EP30-2 mixture (7g EP30-2 + 0.35g glass sphere).
- The test specimen of EP30-2 was baked in the toaster oven. (The result shows perfect curing (no stickyness, no finger print, crisp fracture when bent)
- Applied the bond to the subassemblies.
- FInally the fixtures were put in airbake Oven A. We needed to raise one of the tray with four HSTS balance weights (Attachment 2).

[Stephen Koji]

The baking of the PZT subassemblies was more complicated than we initially thought.

The four PZT subassemblies were placed in the air bake oven A. We meant to bake the assemblies with the ramp time of 2.5h, a plateau of 2h at 94degC, and slow ramp down.

The oven controller was started and the temperature has been monitored. The ramping up was ~20% faster than expected (0.57degC/min instead of 0.47degC/min), but at least it was linear and steady.

Once the temperature reached the set temperature (around t=120min), the temperature started oscillating between 74 and 94degC. Stephen's interpretation was that the PID loop of the controller was not on and the controller falled into the dead-bang mode (=sort of bang-bang control).

As the assembly was already exposed to T>70F for more than 2.5hours, it was expected the epoxy cure was done. Our concern was mainly the fast temperature change and associated stress due to thermal expansion, which may cause delamination of the joint. To increase the heat capacity of the load, we decided to introduce more components (suspension balance weights). We also decided to cover the oven with an insulator so that the conductive heat loss was reduced.

However, the controller thought it was already the end of the baking process and turned to stand-by mode (i.e. turned off everything). This started to cause rapid temp drop. So I (Koji) decided to give a manual heat control for mind cooling. When the controller is turned off and on, it gives some heat for ramping up. So the number of heat pulses and the intervals were manually controlled to give the temp drop of ~0.5degC/min. Around t=325, the temperature decay was already slower than 0.5degC/min without heat pulse, so I decided to leave the lab.

We will check the condition of the sub-assemblies tomorrow (Fri) afternoon.

[Koji Stephen]

(Friday afternoon) We retrieved the PZT sub-assemblies to the clean room.

We started removing the ASSYs from the fixtures. We noticed that some part of the glass and PZT are ripped off from the ASSY and stuck with the fixture. For three ASSYs (except for #9), the effect is minimal. However, ASSY #9 has two large removals on the front surface, and one of the bottom corners got chipped. This #9 is still usable, I believe, but let's avoid to use this unit for the OMC. Individual inspection of the ASSYs is posted in the following entries.

This kind of fracture events was not visible for the past 6 PZT sub-ASSYs. This may indicate a few possibilities:
- More rigorous quality control of EP30-2 was carried out for the PZT ASSY bonding. (The procedure was defined after the past OMC production.) The procedure leads to the strength of the epoxy enhanced.
- During the strong and fast thermal cycling, the glass was exposed to stress, and this might make the glass more prone to fracture.

For the production of the A+ units, we think we can avoid the issues by modifying the fixtures. Also, reliable temperature control/monitor technology should be employed. These improvements should be confirmed with the bonding of spare PZTs and blank 1/2" mirrors before gluing any precious components.

Sub-ASSY #7

Probably the best glued unit among the four.

Attachment #1: Mounting Block SN001

Attachment #2: PZT-Mounting Block bonding looks completely wet. Excellent.

Attachment #3: The other side of the PZT-Mounting Block bonding. Also looks excellent.

Attachment #4: Overall look.

Attachment #5: The mirror-PZT bonding also look excellent. The mounting block surface has many EP30-2 residue. But they were shaved off later. The center area of the aperture is clear.

Attachment #6: A small fracture of the mirror barrel is visible (at 7 o'clock).

Sub-ASSY #8

Probably the best glued unit among the four.

Attachment #1: Mounting Block SN007

Attachment #2: Overall look.

Attachment #3: Some fracture on the barrel visible.

Attachment #4: It is visible that a part of the PZT removed. Otherwise, PZT-Mounting Block bonding looks pretty good.

Attachment #5: The other side of the PZT bonding. Looks fine.

Attachment #6: Fractured PZT visible on the fixture parts.

Attachment #7: Fractured glass parts also visible on the fixture parts.

Attachment #8: MIrror bonding looks fine except for the glass chip.

Sub-ASSY #9

The most fractured unit among four.

Attachment #1: Mounting Block SN017

Attachment #2: Two large removals well visbile. The bottom right corener was chipped.

Attachment #3: Another view of the chipping.

Attachment #4: PZT-mounting block bonding look very good.

Attachment #5: Another view of the PZT-mounting block bonding. Looks very good too.

Attachment #6: Fractures bonded on the fixture.

Attachment #7: Front view. The mirror-PZT bonding look just fine.

Sub-ASSY #10

Attachment #1: Mounting Block SN021

Attachment #2: PZT-Mounting Block bonding looks just excellent.

Attachment #3: The other side of the PZT-Mounting Block bonding is also excellent.

Attachment #4: The mirror-PZT bonding also look excellent. Some barrel fracture is visible at the lower left of the mirror.

Apr 16, 2019
Borrowed two laser goggles from the 40m. (Returned Apr 29, 2019)
Borrowed small isopropanol glass bottole from CTN.

Apr 19, 2019
Borrowed from the 40m:
- Universal camera mount
- 50mm CCD lens
- zoom CCD lens (Returned Apr 29, 2019)
- Olympus SP-570UZ (Returned Apr 29, 2019)
- Special Olympus USB Cable (Returned Apr 29, 2019)

[Stephen, Philip, Koji, Joe]

Breadboard D1200105 SN06 was selected as described in eLOG 338. This log describes unwrapping and preparation of the breadboard.

Relevant procedure section: E1300201 section 6.1.5

Breadboard was unwrapped. No issues observed during unwrapping.

• Attachment 1: packaging of SN06.

Visual inspection showed no issues observed in breadboard - no large scratches, no cracks, no chipping, polished area (1 cm margin) looks good.

• Attachment 2: engraving of SN06.

Initially the breadboard has a large amount of dust and fiber from the paper wrapping. Images were gathered using a green flashlight at grazing incidence (technique typical of optic inspection).

PROCEDURE IMPROVEMENT: Flashlight inspection and Top Gun use should be described (materials, steps) in E1300201.

• Attachment 3: particulate before Top Gun, large face.
• Attachment 4: particulate before Top Gun, small face.

Top gun was used (with medium flow rate) to remove large particulate. Breadboard was placed on Ameristat sheet during this operation.

• Attachment 5: particulate after Top Gun

Next, a clean surface within the cleanroom was protected with Vectra Alpha 10 wipes. The breadboard, with reduced particulate after Top Gun, was then placed inside the cleanroom on top of these wipes. Wiping with IPA Pre-wetted Vectra Alpha 10 wipes proceeded until the particulate levels were acceptable.

Joe and Koji then proceeded with placing the breadboard into the transport fixture.

[Joe, Koji, Liyuan, Philip, Stephen]
Work done on 16.04.2019

Finishing assembly of transport box
Assembly worked fine except for the clamping structure to clamp the lid of the transport box to the bottom part.
It seemed that some of the plastic of these clamps became brittle during the baking. The plastic was removed and the
clamps where wiped clean. It appears that the clamps can't be locked as they should. Still the transport box should be fine
as the long screws will mainly clamp the two parts together.

Preparing the transport box to mount the breadboard
The lid of the the transport box was placed upside down and clamped to the table. All peak clamping structures where pulled back as far as possible.

Preparation and cleaning of the breadboard
We unpacked the breadboard and found lots of dust particles on it (most likely from the soft paper cover which was used). We used the ionized nitrogen gun
at 25 psi to get rid of the majority of particles and cross-checked with a bright green flash light before and after blowing. The second stage of cleaning was done
below the clean room tent and included the wiping of all surfaces. The breadboard was then placed into the prepared lid of the transport box and clamped with peak
screws.

Unpacking of the template
The previously cleaned template was unpacked while the last layer of coverage was removed below the cleanroom tent.

Template adjustment on the breadboard
All peak screws of the clamping structure of the template where removed. The template was placed onto the breadboard only seperated by peak spacers.
All peak screws have been inserted for horizontal clapming. A calipper was used to measure the distance of each edge of the template to the edge of the
breadboard. For documentation the labeled side of the bradboard (facing away from the persons on the pictures) of the upside down breadboard is defined to 
be the south side, continuing clockwise with west, north and east. First rough alignment was done by shifting the template on the breadboard and then the 
peak screws where used for fine tuning. The caliper values measured where:
North   C 8.32mm     E 8.52 mm     W 8.41 mm
East     C 8.08 mm
South   C 8.32 mm
West    C 8.02 mm
(E indicating east side position, W indicating west side position and C indicating center position)

[Stephen, Koji]

As mentioned in eLOG 331, either increased thermal cycling or apparent improvements in cured EP30-2 strength led to fracture of curved mirrors at unintended locations of bonding to the PEEK fixture parts.

The issue and intended resolution is summarized in the attached images (2 different visualizations of the same item).

Redline has been posted to D1600336-v3.

Drawing update will be processed shortly, and parts will be modified to D1600336-v4.

Notes on the OMC cavity alignment strategy

- x3=1.17 γ + 1.40 δ, x4=1.40 γ + 1.17 δ
- This means that the effect of the two curved mirrors (i.e. gouy phases) are very similar. To move x3 and x4 in common is easy, but to do differentially is not simple.
- 1div of a micrometer is 10um. This corresponds to the angular motion of 0.5mrad (10e-6/20e-3 = 5e-4). ~0.5mm spot motion.
- ~10um displacement of the mirror longitudinal position has infinitesimal effect on the FSR. Just use either micrometer (-x side).
- 1div of micrometer motion is just barely small enough to keep the cavity flashing. => Easier alignment recovery. Larger step causes longer time for the alignment recovery due to the loss of the flashes.

- After micrometer action, the first move should be done by the bottom mirror of the periscope. And this is the correct direction for beam walking.

- If x3 should be moved more than x4, use CM2, and vise versa.
- If you want to move x3 to +x and keep x4 at a certain place, 1) Move CM2 in (+). This moves x3 and x4 but x3>x4. 2) Compensate x4 by turning CM1 in (-). This returnes x4 to the original position (approximately), but leave x3 still moved. Remember the increment is <1div of a micrometer and everytime the cavity alignment is lost, recover it before loosing the flashes.

Suddenly something dirty emerged in the lab. What is this? It looks like an insulation foam or similar, but is quite degraded and emits a lot of particulates.

This does not belong to the lab. I don't see piping above this area which shows broken insulation or anything. All the pipes in the room are painted white.

The only possibility is that it comes from the hole between the next lab (CRIME Lab). I found that the A.C. today is much stronger and colder than last week. And there is a positive pressure from CRIME Lab. Maybe the foam was pushed out from the hole due to the differential pressure (or any RF cable action).

That is an expanding fire pillow, also known as firebrick.  It is used to create a fire block where holes in fire-rated walls are made and prevents lab fires from spreading rapidly to adjacent labs.  I had to pull cable from B254 to our labs on either side during a rather narrow window of time.  Some of the cable holes are partially blocked, making it difficult to reach the cable to them. The cable is then just guided to the hole from a distance.  With no help, it's not possible to see this material getting shoved out of the hole.  I can assure you that I took great pains not to allow the CYMAC coax to fall into any equipment, or drag against any other cables.   

[LiyuanZ, StephenA]

Downs B119

Summary: Beginning on 20 May 2019, two CM PZT assemblies were soaked in Acetone in an effort to debond the EP30-2 bonds between tombstone-PZT and between PZT-optic. Debonding was straightforward after 8 days of soaking. 24 hours of additional acetone soaking will now be conducted in an attempt to remove remnant EP30-2 from bonding surfaces.

Procedure: The assemblies were allowed to soak in acetone for 8 days, with acetone level below the HR surface of the optic. No agitation of the solution, mechanical abrasion of the bond, or other disturbance was needed for the bond to soften.

GariLynn contributed the glassware and fume hood, and advised on the process (similar to debonding of CM and PZT from OMC SN002 after damaging event). The equipment list was (WIP, more detail / part numbers will be gathered today and tomorrow):

• crystallizing dish (no spout, like a deep petri dish)
• curved lid
• wax sheet (to seal)
• acetone
• fume hood

Results: Today, 28 May 2019, I went to the lab to check on the optics after 8 days of soaking. Liyuan had monitored the acetone level during the first 4 days, topping up once on 24 May. All bonds were fully submerged for 8 days.

There were 2 assemblies soaked in one crystallizing dish. Debonded assemblies - ref OMC eLOG 328 for specified orientations and components:

PZT Assy #9 - ref. OMC eLOG 334 - M17+PZT#12+C10

PZT Assy #7 - ref. OMC eLOG 332 - M1+PZT#13+C13

PZT Assy #7 was investigated first.

• C13 was removed with no force required.
• PZT#13 was removed with no force required.
• EP30-2 remained at the bond surfaces and tracing the diameters of each bond on each of the 3 bonding surfaces of the PZT and tombstone - these components were returned to the dish to soak.
• No EP30-2 remained on the surface of the curved mirror - C13 was removed and stored.

A video of removal of C10 and PZT#12 from PZT Assy #9 was collected (See Attachment 8), showing the ease with which the debonded components could be separated.

• C10 was removed with no force required.
• A slight force - applied by gripping the barrel of the PZT and pushing with the index finger on the surface of the tombstone - was required to separate PZT#12 from M17,
  • likely due to excess glue at the barrel of the PZT
• EP30-2 remained at the bond surfaces and tracing the diameters of each bond on each of the 3 bonding surfaces of the PZT and tombstone - these components were returned to the dish to soak.
• No EP30-2 remained on the surface of the curved mirror - C13 was removed and stored.

Photos and video have been be added to supplement this report (edit 2019/07/08).

https://www.airscience.com/purair-flow-laminar-flow-cabinets

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.

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])

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.

[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.

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.

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.

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.

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.

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.

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

[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.
 

[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.

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