Tara: Laser Safety goggle -> Returned

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

Dmass:

LB1005 Oct 24.

On breadboarfd cabling for 3IFO OMC

D1300371 - S1301806
D1300372 - S1301808
D1300374 - S1301813
D1300375 - S1301815

DCPD Connector Face: Qty2 https://dcc.ligo.org/LIGO-D1201276
QPD Connector Face: Qty2 https://dcc.ligo.org/LIGO-D1201282

PD faster: 92210A07 Qty 4: MCMASTER #2-56 x .25 FHCS

Spare DCPD

Jan 15, 2015 3rd OMC completed

The face caps of the DCPD/QPD cables were installed (Helicoils inserted)
PD7&10 swapped with PD11(for DCPD T) and PD12(DCPD R).
Firct Contact coating removed

Note on the 3rd OMC

Before the 3rdOMC is actually used,

- First Contact should be applied again for preventing contamination during the installation

- DCPD glass windows should be removed

Gabriele:

PZT HV Amp

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

Dmass:

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

- The laser was removed and shipped to LHO today.

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

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

1. UV Illuminator (LESCO Super Spot MK III)

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

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

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

All returned: Aug 30, 2016

LLO has one empty OMC transportation fixture.

LHO has one empty OMC transportation fixture.

LHO has one OMC transportation fixture with 3IFO OMC in it.

LHO has the Pelican trunk for the OMC transportation. Last time it was in the lab next to the optics lab.

Kate (ATF)

- 4ch color oscilloscope (Tektronix)

- Chopper controller

- Chopper with a rotating disk

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.

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.

TEST Result: S1500118

Additional notes

- Checked the power supply. All voltages look quiet and stationary.

- Checked the internal RF cables too see if there is any missing shield soldering => Looked fine

- Noticed that the RFAM detector board has +/-21V for the +/-24V lines => It seems that this is nominal according to the schematic

- Noticed that the RFAM detector sensitivity were doubled fomr the other unit.
  => This is reated to the modification (E1500353) of  "Controller Board D0900761-B Change 1" (doubling the monitor output gain)

- Noticed that the transfer function of the CTRL signal on the BNC and the DAQ output.
  => This is reated to the modification (E1500353) of  "Servo Board D0900847-B Change 1"  (servo transfer function chage)
  => The measured transfer function did not agree with the prediction from the circuit constants in this document
  => From the observation of the servo board it was found that R69 was not 200Ohm but 66.5 Ohm (See attachment 1).
       This explained the measured transfer function. The actuator TF has: P 2.36, Z 120., K -1@DC (0.020@HF)

- Similarly, the TF between the CTRL port on the unit and the CTRL port on the test rig was also modified.

Noise level

Attachment 2

- The amplitude noise in dBc (SSB) was measured at the output of 27dBm. From the test sheet, the noise level with 13dBm output was also referred. From the coherence of the MON1 and MON2, the noise level was inferred. It suggests that the floor level is better than 180dBc/Hz. However, there is a 1/f like noise below 1k and is dominating the actual noise level of the RF output. Daniel suggested that we should check nonlinear downconversion from the high frequency noise due to the noise attenuator. This will be check with the coming units.

The Glasgow polarizer was passed to Kate on Dec 17, 2015.

As of Jul 22, 2016
As of Aug 11, 2016
As of Aug 16, 2016

A1-23 in Cage G https://ics-redux.ligo-la.caltech.edu/JIRA/browse/IHGQEX3000-0-00-A1-23
-> Shipped to LLO https://ics-redux.ligo-la.caltech.edu/JIRA/browse/Shipment-8181
-> Now in https://ics-redux.ligo-la.caltech.edu/JIRA/browse/ASSY-D1201439-1
= Replaced C30665 eLIGO PD (SN 01 in Cage G now) ICS: C30665GH-0-00-0001
-> Removed PD@LLO, Waiting for the shipment to CIT

A1-25 in Cage G https://ics-redux.ligo-la.caltech.edu/JIRA/browse/IHGQEX3000-0-00-A1-25
-> Shipped to LLO https://ics-redux.ligo-la.caltech.edu/JIRA/browse/Shipment-8181
-> Now in https://ics-redux.ligo-la.caltech.edu/JIRA/browse/ASSY-D1201439-1
= Replaced C30665 eLIGO PD (SN 02 in Cage G now) ICS: C30665GH-0-00-0002
-> Removed@LLO, Waiting for the shipment to CIT

B1-01 in Cage A https://ics-redux.ligo-la.caltech.edu/JIRA/browse/IHGQEX3000-0-00-B1-01
-> Shipped to LHO https://ics-redux.ligo-la.caltech.edu/JIRA/browse/Shipment-8182
-> Now in https://ics-redux.ligo-la.caltech.edu/JIRA/browse/ASSY-D1201439-3_2
= replaced C30665 eLIGO PD (SN 11 in Cage A now) ICS: C30665GH-0-00-0011
-> Removed PD@LHO
-> Shipped from LHO to CIT https://ics-redux.ligo-la.caltech.edu/JIRA/browse/Shipment-8187

B1-16 in Cage A https://ics-redux.ligo-la.caltech.edu/JIRA/browse/IHGQEX3000-0-00-B1-16
-> Shipped to LHO https://ics-redux.ligo-la.caltech.edu/JIRA/browse/Shipment-8182
-> Now in https://ics-redux.ligo-la.caltech.edu/JIRA/browse/ASSY-D1201439-3_2
= replaced C30665 eLIGO PD (SN 12 in Cage A now) ICS: C30665GH-0-00-0012
-> Removed PD@LHO
-> Shipped from LHO to CIT https://ics-redux.ligo-la.caltech.edu/JIRA/browse/Shipment-8187

C1-05 in Cage F https://ics-redux.ligo-la.caltech.edu/JIRA/browse/IHGQEX3000-0-00-C1-05
-> @CIT contamination test cavity

C1-07 in Cage F https://ics-redux.ligo-la.caltech.edu/JIRA/browse/IHGQEX3000-0-00-C1-07
-> @CIT contamination test cavity

C1-17 in Cage E https://ics-redux.ligo-la.caltech.edu/JIRA/browse/IHGQEX3000-0-00-C1-17
-> Shipped to LHO https://ics-redux.ligo-la.caltech.edu/JIRA/browse/Shipment-8182
-> Left @LHO as a spare

C1-21 in Cage E https://ics-redux.ligo-la.caltech.edu/JIRA/browse/IHGQEX3000-0-00-C1-21
-> Shipped to LHO https://ics-redux.ligo-la.caltech.edu/JIRA/browse/Shipment-8182
-> Left @LHO as a spare

D1-08 in Cage E https://ics-redux.ligo-la.caltech.edu/JIRA/browse/IHGQEX3000-0-00-D1-08
-> Shipped to LHO https://ics-redux.ligo-la.caltech.edu/JIRA/browse/Shipment-8182
-> Moved to Cage A3
-> Shipped from LHO to CIT https://ics-redux.ligo-la.caltech.edu/JIRA/browse/Shipment-8186
-> Arrived at CIT (Aug 16)

D1-10 in Cage E https://ics-redux.ligo-la.caltech.edu/JIRA/browse/IHGQEX3000-0-00-D1-10
-> Shipped to LHO https://ics-redux.ligo-la.caltech.edu/JIRA/browse/Shipment-8182
-> Moved to Cage A4
-> Shipped from LHO to CIT https://ics-redux.ligo-la.caltech.edu/JIRA/browse/Shipment-8186
-> Arrived at CIT (Aug 16)

Previous H1 OMC shipped from LHO to CIT

https://ics-redux.ligo-la.caltech.edu/JIRA/browse/Shipment-8196

- FS base + Mounting Prism

- FS or SF2 1/2" piece + FS or SF2 1/2" piece

- FS? plate + FS or SF2 1/2" piece + FS or SF2 1/2" piece + FS? plate

To 40m

First Contact Kit by Calum

Class A Kapton sheets

D1102211 OMC Diode Mount Glass Block (11pcs) have been given to Calum@Downs

- About 1.5 month ago, an 700mW LWE NPRO has been brought to OMC Lab.

- The SOP can be found here.

- The base was made for the beam elevation of 3" height. Four 1" pedestals were attached to rise the beam elevation to 4".

- The output from the laser is ~740mW

- After the faraday and the BB EOM, the output is ~660mW

- After the usual struggle, the beam was coupled to the SM fiber. The output is 540mW. The coupling efficiency is >80%.

- Will proceed to the OMC cavity alignment.

FIber Input Mount 132deg
Fiber output mount 275deg
-> 525mW P: 517mW S: 8mW extinction ratio: 0.016

The OMC mode matching sled was fixed on the nominal part of the table. Then the OMC was located at the nominal position marked by three poles.

The input periscope was adjusted to have the input beam roughtly centered on the OMC QPDs. This made the beam from FM2 aligned to the missing CM1, and the beam just went through the hole of the mounting prism. Very promising!

I wanted to use the new (modified) mirror gluing fixture to hold a curved mirror on the mounting prism. It turned out that the fixture was neither cleaned nor assembled. I will ask Downs Team to help me to get the cleaned and assembled fixtures.

Meanwhile, I just reused the original gluing fixture upside down in order to proceed cavity alignment and locking. (Attachment 1)
In fact, once the mirror is placed on the mounting prism, the cavity started to flash without further alignment. I thank for the very precise (repeatable) alignment of the OMC optics and PD/QPDs.

The next steps are initial cavity locking, more alignment, and mode matching.

The OMC cavity was locked. The alignment was precisely adjusted. The mode matching was optimized by the lens positions. The reflection during the lock is ~0.01 compared to the full reflection on non-resonance, meaning the mode matching is ~99%. The error signal was maximized (i.e. demod pahse was adjusted) by sweeping the modulation frequency. Note that the EOM is broad band. The modulation freq chosen today was 34.6MHz.

Some notes:

- The error signal has not been preamplified at all yet. Because of this, the reflection is very much sensitive to the input offset.

- The OMC needs wind shield to prevent from the noise caused by air turbulance.

- The laser PZT was actuated via the Thorlabs HV amp. Otherwise, the thermal path needs to be configured.

- One of the CCD monitor is dead. Needs more replacement.

- All the electronics should be moved to the rack. This required long BNC and SMA cables.

- The optical table needs cleaning.

Ordered:

Office Depot
v AA battery Qty. 24
v 9V battery Qty. 4
v Floor cable cover (6ft)

Thorlabs
v HV PZT Driver
v Lenses

• BNC Patch Panel
  • 8x Amphenol Connex 112443 / Isolated BNC FEMALE TO FEMALE BULKHEAD ISOLATED ADAPTER - 50 ohm
    • http://www.newark.com/amphenol-rf/112443/bulkhead-adapter-bnc-jack-bnc/dp/99H4399
    • Hole Diameter: 13mm (0.512") D width 12.10mm (0.477")
  • 4x Amphenol RF 31-4803-75 (75Ohm)
    • http://www.newark.com/amphenol-rf/31-4803-75/bulkhead-adapter-bnc-jack-bnc/dp/50B8959
    • same as above
  • 2x Handle HAMMOND 98H1240
    • http://www.newark.com/hammond/1427b/equipment-handle/dp/98H1240
    • Hole Diameter: #4-40 (0.1120") Distance 1.25"
       
• SMA Patch Panel
  • 8x Isolated SMA-SMA adapter
    • https://www.pasternack.com/sma-female-sma-female-straight-adapter-pe9067-p.aspx
    • Hole Diameter: 0.312" D width 0.295"

[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.