40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
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ID Date Author Type Category Subject
8   Wed Mar 24 17:36:46 2021 PacoGeneralDesign specsLeast common multiple stacks and varL cost

## Update on ETM/ITM coating design;

- Following what seemed like a good, intuitive suggestion from Anchal, I implemented a parameter called Ncopies, which takes a stack of m-bilayers and copies it a few times. The idea here was to have stacks where m is the least common multiple of the wavelength fractional relation e.g. m(2/3) = 6 so as to regain some of the coherent scattering in a stack. Unfortunately, this didn't work as planned for m=6, 3, and 2.

- While the target transmissivities are reached with comparably fewer layers using this method, the sensitivity and the surface E field are affected and become suboptimal. The good thing is we can do the old way just by setting Ncopies = 0 in the optimization parameters yaml file.

- An example of such a coating is in Attachment 1.

- I decided to just add the 'varL' scalar cost to the optimizer. Now we minimize for the variance in the coating stack thicknesses. As a target I started with 40% but will play with this now.

Attachment 1: ETM_Layers_210323_0925.pdf
83   Wed Sep 28 22:11:31 2022 Jennifer HritzGeneralOptical ContactingLooked at Thor Lab slides

While finalizing my work plan for the quarter, I decided to look at the Thor Lab slides. This was instructive because they highlighted the troubles I will have with working with silicone. They are fragile and their small, thin sizes makes cleaning and manipulating them (without contamination) much more difficult compared to the glass sides from before.

I tried cleaning and bonding them the same way as the larger slides. Rubbing them together did not work like with the larger sides, but that may also be a function of being more careful, as not to break them. Once I cleaned them, it only took a tap from my finger to get the center to bond, but the bonded surface area still did not spread out like it did in the YouTube videos (http://youtu.be/se3K_MWR488?t=80). By pressing down around the bonded area, I could expand it slighty. Note that I did crack one slide in the process of doing this, as shown in the pictures.

Because the slides are so thin, I think they will benefit greatly from being left under a heavy object, although it may be difficult to put the weight on the slides without them breaking.

Attachment 1: thor_lab_slides_first_bond_PXL_20220929_045352675.MP.jpg
Attachment 2: thor_lab_slides_after_attempting_to_expand_bond_area_PXL_20220929_045510075.MP.jpg
84   Thu Sep 29 18:36:40 2022 Jennifer HritzGeneralOptical ContactingLooked at Thor Lab slides (continued)

Continuining with my casual exploration of the Thor Lab slides, I heated them from off --> low --> med --> high, with 10 minutes on each setting. The only pressure I applied was 3 larger glass slides, and that was only to flatten out the copper that the smaller, bonded slides sat on top of (so the contact with the heating plate was even).

The heat made the bonded area smaller, but it did not break. As the slides cooled, the bond area increased slightly but not back to the original size. Next I will try this with slower heating and additional pressure.

Attachment 1: before_heat_PXL_20220930_011031420.MP.jpg
Attachment 2: set_up_PXL_20220930_011050114.MP.jpg
Attachment 3: right_after_heating_PXL_20220930_014301900.MP.jpg
Attachment 4: after_4ish_hours_of_cooling_PXL_20220930_063533904.jpg
1   Thu May 21 11:51:44 2020 KojiGeneralGeneralMariner Elog Test

The first entry of the Mariner elog post

45   Wed Nov 3 02:52:49 2021 KojiGeneralSuspensionMariner Sus Design

All parameters are temporary:

Test mass size: D150mm x L140mm
Intermediate mass size W152.4mm x D152.4mm x H101.6mm
TM Magnets: 70mm from the center

Height from the bottom of the base plate
- Test mass: 5.0" (127mm) ==> 0.5" margin for the thermal insulation etc (for optical height of 5.5")
- Suspension Top: 488.95mm
- Top suspension block bottom: 17.75" (450.85mm)
- Intermediate Mass: 287.0mm (Upper pendulum length 163.85mm / Lower pendulum length 160mm)

OSEMs
- IM OSEMs: Top x2 (V/P)<-This is a mistake (Nov 3 fixed), Face x3 (L/Y/P), Side x 1 (S)
- TM OSEMs: Face x4
- OSEM insertion can be adjusted with 4-40 screws

To Do:
(Nov 3 50% done)
- Space Consideration: Is it too tight?
- Top Clamp: We are supposed to have just two wires
(Nov 3 50% done)
- Lower / Middle / Upper Clamps & Consider installation procedure
- Pendulum resonant frequencies & tuning of the parameters
- Utility holes: other sensors / RTDs / Cabling / etc

- Top clamp options: rigid mount vs blade springs
- Top plate utility holes
- IM EQ stops

Discussion with Rana

- Hoe do we decide the clear aperture size for the TM faces?
- OSEM cable stays

- Light Machinery can do Si machining
- Thermal conductivity/expansion

- The bottom base should be SUS... maybe others Al except for the clamps

- Suspension eigenmodes separation and temperature dependence

# Deleted the images because they are obsolete.

46   Thu Nov 4 00:42:05 2021 KojiGeneralSuspensionMariner Sus Design

Some more progress:

- Shaved the height of the top clamp blocks. We can extend the suspension height a bit more, but this has not been done.

- The IM OSEM arrangement was fixed.

- Some EQ stops were implemented. Not complete yet.

Attachment 1: Screen_Shot_2021-11-04_at_12.38.46_AM.png
Attachment 2: Screen_Shot_2021-11-04_at_12.39.53_AM.png
51   Thu May 5 19:56:25 2022 KojiGeneralSuspensionMariner Suspension Cryo shield Install / Removal steps

Does this work? Is this insane?

Attachment 1: 40m_Mariner_Suspension-0062.png
Attachment 2: 40m_Mariner_Suspension.mp4
52   Tue May 10 18:29:11 2022 ranaGeneralSuspensionMariner Suspension Cryo shield Install / Removal steps

cool

Here I describe the current radiative cooldown model for a Mariner test mass, using parameters from the most recent CAD model. A diagram of all conductive and radiative links can be seen in Attachment 1. Below are some distilled key points:

1. The source of cooling power is an infinite reservoir at 60K - realistically there will be finite cooling power and the system will be optimized within that constraint.
2. The outer shield surrounds the suspension system and some cooling power can be delivered conductively to the outer shield to hold it at an optimal temperature.
3. The suspension cage has 4 feet that insulate the cage from the table at RT.
4. The cage is composed of vertical beams and bottom and top lids. Radiative view factors from the cage to other components have been loosely estimated.
5. Suspension wires conduct heat from the cage to the upper mass, and from the upper mass to the test mass.
6. The inner shield and snout surround the test mass. Aperature openings in the inner shield (for wires) allow the test mass to radiatively "see" surroundings at ~outer shield T.
7. The snout openings and incident laser power are additional heat loads to the test mass.

All parameters have been taken from CAD, with the exception of:

1) snout length: originally 0.665m in CAD (end to end), but I doubled it to 1.33m following a discussion in group meeting
2) length of copper bar / conductive cooling pathway: set to the end-to-end length of snout. Though this is a conservative over-estimate
2) thermal conductivity of insulating feet: using 0.25 W/mK
3) radius of aperture in IS for suspension wires: using 1"

Attachment 2 contains the cooldown curves for the system components. With the above assumptions, the test mass takes ~59hrs to reach 123K, and the final steady-state temperature is 96K. (*This was edited - found a bug in previous iteration of code that underestimated the TM cooldown time constant and incorrectly concluded ~36hrs to reach 123K. The figures have been updated accordingly.)

Attachment 3-6 are power budgets for major components: TM, IS, Cage, OS (can produce for UM if there's interest). For each, the top plot shows the total heating and cooling power delivered to the component, and the bottom plot separates the heating into individual heat loads. I'll discuss these below:

- TM: The laser delivers 100mW of heating power to the test mass throughout the cooldown. The next most significant source of heating is snout - this warrants further optimization (see next ELOG).
- IS: Inevitably the test mass heats the inner shield, but the other heat loads are minimal. Note that the model does not consider radiation from the snout opening to the snout/inner shield walls, and this will be added in soon.
- Cage: The only significant heat load to the cage is conduction from the RT table through the feet. The feet can be made taller, or actively held at a colder temperature.
- OS: I've arbitrarily added conductive cooling to the OS which holds it around 175K. With the current model, adding more cooling power would only help, but in reality this will divert cooling power from going to the IS. This constraint needs to be added in before the optimal OS temperature can be determined. The most significant heat loads are from the chamber walls and the cage (see above).

The next post will describe optimization of the snout length/radius for cooldown.

Attachment 2: MarinerTMCooldown.pdf
Attachment 3: TMPowerBudget.pdf
Attachment 4: ISPowerBudget.pdf
Attachment 5: CagePowerBudget.png
Attachment 6: OSPowerBudget.pdf

Here is a more detailed analysis of varying the length and radius of the snout.

Attachment 1 plots the heat load (W) from the snout opening as a function of temperature, for different combinations of snout length and radius. The model using the CAD snout parameters (length=0.67m end-to-end; radius=5.08cm) results in ~0.3W of heat load at steady state. The plot shows that the largest marginal reduction in heat load is achieved by doubling the length of the snout (green curve), which cuts the heat load by over a factor of 2/3. This validates the choice in snout length used in the previous ELOG entry analysis. The bottom line is that the end-to-end snout length should be on the order of 1 meter, if physically possible.

The next marginal improvement comes from reducing the radius of the snout. Attachment 1 considers reducing the radius by a half in addition to doubling the length (red curve). A snout radius of an inch is quite small and might not be feasible within system constraints, but it would reduce the snout heat load to only 25mW at steady state (along with length doubling).

The cooldown model resulting from optimizing parameters of the snout (length=1.33m, radius=2.54cm) is shown in Attachment 2. The test mass reaches 123K in ~57hrs - only 2 hours faster than the case where only the snout length is doubled (see previous ELOG entry) - and the test mass reaches steady state at 92K - only 6K colder than in the previous case. This could discourage efforts to reduce the radius of the snout at all, since increasing the length provides the most marginal gains.

Attachment 1: VaryingSnoutparams.pdf
Attachment 2: MarinerTMCooldown_snout_optimal.pdf

The attached plot (upper) compares the heat load delivered to the test mass from various snout lengths (end to end), as a function of test mass temperature. (At steady state, our point of interest is 123K.) Note that these curves use the original CAD snout radius of 5.08cm (2").

The greatest marginal reduction in heat load comes from increasing the end-to-end snout length to 1m, as concluded in the prevous ELOG. This drops the heat load from just under 0.5W (from snout length 0.5m) to 0.15W. Further increase in snout length to 1.5m drops the heat load to well under 0.1W. After this point, we get diminishing marginal benefit for increase in snout length.

The effect on the TM cooldown curve can be seen in the lower plot. A snout length of 1m drops the steady-state TM temperature to under 100K. Then, like above, increasing the length to 1.5m makes the next non-negligible impact.

Attachment 1: SnoutLengthCooldownTM.pdf
30   Fri Sep 24 13:12:00 2021 RadhikaGeneralHeat LoadMariner cooldown model status + next steps

*Note: the current modeling script can be found at: CryoEngineering/MarinerCooldownEstimation.ipynb

Nina pointed me to the current mariner cooldown estimation script (path above) and we have since met a few times to discuss upgrades/changes. Nina's hand calculations were mostly consistent with the existing model, so minimal changes were necessary. The material properties and geometric parameters of the TM and snout were updated to the values recently verified by Nina. To summarize, the model considers the following heat sources onto the testmass (Pin):

- laser absorption by ITM bulk (function of incident laser power, PR gain, and bulk absorption)

- laser absorption by ITM HR coating (function of incident laser power and HR coating absorption)

The heat transfer out of the testmass (Pout) is simply the sum of the radiative heat emitted by the HR and AR faces and the barrel. Note that the script currently assumes an inner shield T of 77K, and the inner/outer shield geometric parameters need to be obtained/verified.

Nina and Paco have been working towards obtaining tabulated emissivity data as a function of temperature and wavelength. In the meantime, I created the framework to import this tabulated data, use cubic spline interpolation, and return temperature-dependent emissivities. It should be straightforward to incorporate the emissivity data once it is available. Currently, the script uses room-temperature values for the emissivities of various materials.

Future steps:

- Incorporate tabulated emissivity data

- Verify and update inner/outer shield dimensions

31   Mon Sep 27 17:01:53 2021 ranaGeneralHeat LoadMariner cooldown model status + next steps

How about a diagram so that we can understand what this model includes?

32   Wed Sep 29 16:15:19 2021 RadhikaGeneralHeat LoadMariner cooldown model status + next steps

Attachment 1 is a geometric diagram that reflects the current state of the ITM cooldown model, introduced in [30]. The inner shield is assumed to be held at 77K for simplicity, and 2 heat sources are considered: laser heating, and radiative heating from the room-temperature snout opening. The view factor Fij between the snout opening and test mass (modeled as 2 coaxial parallel discs separated by length L - equation found in Cengel Heat Transfer) is calculated to be 0.022. The parameters used in the model are noted in the figure.

Attachment 2 is a simplified diagram that includes the heating/cooling links to the test mass. At 123K, the radiative cooling power from the inner shield (at 77K) is 161 mW. The radiative heating from the snout opening is 35 mW, and the laser heating (constant) is 101.5 mW. Due to the tiny view factor betwen the snout opening and the test mass, most of the heat emitted by the opening does not get absorbed.

The magnitudes of heating and cooling power can be seen in Attachment 3. Lastly, Attachment 4 plots the final cooldown curve given this model.

My next step is to add the outer shield and fix its temperature, and then determine the optimal size/location of the inner shield to maximize cooling of the test mass. This is question was posed by Koji in order to inform inner shield/outer shield geometric specs. Then, I will add a cold finger and cryo cooler (conductive cooling). Diagrams will be updated/posted accordingly.

Attachment 3: heating_cooling_P_vs_T.pdf
37   Tue Oct 5 17:46:14 2021 RadhikaGeneralHeat LoadMariner cooldown model status + next steps

Building on [32], I added a copper cold finger to conductively cool the inner shield, instead of holding the inner shield fixed at 77K. The cold finger draws cooling power from a cyro cooler or "cold bath" held at 60K, for simplicity. I added an outer shield and set its temperature to 100K. The outer shield supplies some radiative heating to the inner shield, but blocks out 295K heating, which is what we want. The expanded diagram can be seen in Attachment 1.

I wanted to find the optimal choice of inner shield area (AIS) to maximize the radiative cooling to the test mass. I chose 5 values for AIS (from ATM to AOS) and plotted the test mass cooldown for each in Attachment 2. The radiative coupling between the inner shield and test mass is maximized when the ratio of the areas, ATM/AIS, is minimized. Therefore, the larger AIS, the colder the test mass can be cooled. Even though choosing AIS close to AOS increases the coupling between the 2 shields, the resulting heating from the outer shield is negligible compared to the enhancement in cooling.

I chose AIS = 0.22 m2 to model the inner shield and test mass cooldown in Attachment 3. The test mass reaches 123 K at ~ 125 hours, or a little over 5 days. I have pushed the updated script which can be found under mariner40/CryoEngineering/MarinerCooldownEstimation.ipynb.

Attachment 2: VaryingISA.pdf
Attachment 3: CooldownTM.pdf
42   Fri Oct 15 13:45:55 2021 RadhikaGeneralHeat LoadMariner cooldown model status + next steps

I used the same model in [37] to consider how test mass length affects the cooldown. Attachment 1 plots the curves for TM length=100mm and 150mm. The coupling between the test mass and inner shield is proportional to the area of the test mass, and therefore increases with increasing length. Choosing l=100mm (compared to 150mm) thus reduces the radiative cooling of the test mass. The cooldown time to 123K is ~125 hrs or over 5 days for TM length=150mm (unchanged from [37]), but choosing TM length=100m increases this time to ~170 hrs or ~7 days. (Note that these times/curves are derived from choosing an arbitrary inner shield area of 0.22 m2, but the relative times should stay roughly consistent with different IS area choices.)

Attachment 1: VaryingTMl.pdf
43   Fri Oct 15 14:31:15 2021 RadhikaGeneralHeat LoadMariner cooldown model status + next steps

I reran the cooldown model, setting the emissivity of the inner surface of the inner shield to 0.7 (coating), and the emissivity of the outer surface to 0.03 (polished Al). Previously, the value for both surfaces was set to 0.3 (rough aluminum).

Attachment 1: TM cooldown, varying area of the inner shield. Now, the marginal improvement in cooldown once the IS area reaches 0.22 m2 is negligible. Cooldown time to 123K is ~100 hrs, just over 4 days. I've kept IS area set to 0.22 m2 moving forward.

Attachment 2: TM/IS cooldown, considering 2 lengths for the test mass. Choosing l=100m instead of 150mm increases cooldown time from ~100 hrs to ~145 hrs, or 6 days.

Attachment 1: VaryingISA.pdf
Attachment 2: VaryingTMl.pdf
38   Mon Oct 11 15:22:18 2021 YehonathanGeneralGeneralMicrocomb alternatives

Following our discussion at the Friday JC meeting, I gathered several resources and made a small simulation to show how frequency combs might be generated on platforms other than microcombs or mode-locked lasers.

Indeed, frequency combs generated directly from a mode-locked laser are expensive as they require ultra-broadband operation (emitting few fs pulses) to allow for f-2f interferometry.

Microcombs are a fancy way of generating combs. They are low-power-consuming, chip-scale, have a high repetition rate, and are highly compatible with Silicon technology. While these are huge advantages for industry, they might be disadvantageous for our purpose. Low-power means that the output comb will be weak (on the order of uW of average power). Microscopic/chip-scale means that they suffer from thermal fluctuations. High rep-rate means we will have to worry about tuning our lasers/comb to get beat notes with frequencies smaller than 1GHz.

Alternatively, and this is what companies like Menlo are selling as full-solution frequency combs, we could use much less fancy mode-locked lasers emitting 50fs - 1ps pulses and broaden their spectrum in a highly nonlinear waveguide, either on a chip or a fiber, either in a cavity or linear topologies. This has all the advantages:

1. High-power (typically 100mW)

2. Low rep-rate (typically 100MHz)

3. Relatively cheap

4. "Narrowband" mode-locked lasers are diverse and can come as a fiber laser which offers high stability.

As a proof of concept, I used this generalized Schrodinger equation solver python package to simulate 1d light propagation in a nonlinear waveguide. I simulated pulses coming out of this "pocket" laser (specs in attachment 1) using 50mW average power out of the available 180mW propagating in a 20cm long piece of this highly nonlinear fiber (specs in attachment 2).

The results are shown in attachments 3-4:

Attachment 3 shows the spectrum of the pulse as a function of propagation distance.

Attachment 4 shows the spectrum and the temporal shape of the pulse at the input and output of the fiber.

It can be seen that the spectrum is octave-spanning and reaches 2um at moderate powers.

One important thing to consider in choosing the parameters of the laser and fiber is the coherence of the generated supercontinuum. According to this paper and others, >100fs pulses and/or too much power (100mW average is roughly the limit for 50fs pulses) result in incoherent spectra which is useless in laser locking or 1f-2f interferometry. These limitations apply only when pumping in the anomalous dispersion regime as traditionally have been done. Pumping in an all-normal (but low) dispersion (like in this fiber) can generate coherent spectra even for 1ps pulses according to this paper and others. So even cheaper lasers can be used. ps pulses will require few meter-long fibers though.

Attachment 1: ELMO_specs.png
Attachment 2: HNLF_specs.png
Attachment 3: SimulationResults1.png
Attachment 4: SimulationResults3.png
39   Tue Oct 12 12:44:44 2021 Jiri SmetanaGeneralGeneralNew Damping Loop Model

I've ironed out the issues with my MATLAB model so that it now shows correct phase behaviour. The problem seems to arise from infinite Q poles where there is an ambiguity in choosing a shift of +/- 180 deg in phase. I've changed my state space model to include finite but very high Q poles to aid with the phase behaviour. The model has been uploaded to the GitLab project under mariner40 -> mariner_sus -> models -> lagrangian.

78   Tue Aug 23 17:10:50 2022 PacoGeneralDesign specsNew corner plots

Instead of varying individual layer thicknesses using the MC sampler, I made sure both the thickness and index of refractions are varied as a global systematic error to estimate the design sensitivity. The results for ITM/ETM respectively, with 1e5 samples this time, are in Attachments 1-2 below.

Attachment 1: ITM_corner.pdf
Attachment 2: ETM_corner.pdf
70   Tue Jul 26 14:17:44 2022 JuanGeneralGeneralOSEMS actuators

we have 23 OSEMS they look all full built and I will try and test them this week and or next week.

Attachment 1: IMG-6050.jpg
Attachment 2: IMG-6045.jpg
Attachment 3: IMG-6044.jpg
Attachment 4: IMG-6051.jpg
Attachment 5: IMG-6049.jpg
Attachment 6: IMG-6046.jpg
Attachment 7: IMG-6048.jpg
Attachment 8: IMG-6047.jpg
2   Thu May 21 12:10:03 2020 StephenGeneralResourcesOngoing Mariner Resources

Mariner Chat Channel
Mariner Git Repository

13   Fri May 7 09:57:18 2021 StephenGeneralEquipmentOverall Dimensions for Mariner Suspension Test Chamber Concept

Koji, Stephen

Putting together Koji's design work with Stephen's CAD, we consider the size of a test chamber for the Mariner suspension.

Koji's design uses a 6" x 6" Si optic, with an overall height of about 21.5".

Stephen's offsets suggest a true shield footprint of 14" x 14" with an overall height of 24".

With generous clearances on all sides, a test chamber with a rectangular footprint internally of about 38" x 32" with an internal height of 34" would be suitable. This scale seems similar to the Thomas Vacuum Chamber in Downs, and suggests feasibility. It will be interesting to kick off conversations with a fabricator to get a sense for this.

This exercise generated a few questions worth considering; feel welcome to add to this list!

• do we need to have the suspended snout(s)?
• are we studying an ITM or ETM (or both)?
• relays or other optical components on the baseplate?
• angles of optical levers?
• off center mounting?
• two doors for front/back access?

Attachment 1: mariner_suspension_test_chamber_concept.jpg
18   Wed Jul 7 16:32:27 2021 StephenGeneralEquipmentOverall Dimensions for Mariner Suspension Test Chamber Concept

WIP - Stephen to check on new suspension dimensions and fit into 40m chamber

109   Sun Oct 23 21:01:40 2022 Jennifer HritzGeneralOptical ContactingPWM 3.0 (+280°C in 5)

I decided test how fast the plates would heat up if the heat was just on constantly on for 5 minutes. In general, these tests are raising a lot of questions in regards to controlling the temperature given the hysteresis in the system. It is also apparent that the bottom plate heats up signficantly faster than the top one, which means I need to heat the samples much longer than, say 10 minutes, if I want to avoid unevenly heating both parts of the optically contacted piece.

I also have to be conscientious that I am already half way through the quarter and ideally should be devoting time to bond strength testing rather than continuing to fiddle with the hot plate.

Attachment 1: PWM_plates_-_increase_280Â°C_in_5_minutes.pdf
112   Wed Oct 26 21:27:23 2022 JenniferGeneralOptical ContactingPWM 3.1 (more) very slow heating

[I'm (once again) behind on data processing, but I'm creating an entry on the day I actually run the tests]

110   Mon Oct 24 21:23:22 2022 Jennifer HritzGeneralOptical ContactingPWM 3.1 longer off times in cycle

To combat the bottom plate heating up much faster than the top plate, I decided to try increasing the cycle period from 1000ms (1s) to 10000ms (10s). In other words, taking the test I today ran as an example, the hot plate will now be on for 1000ms then off for 9000ms then repeat. Hopefully this should give more time for the heat to transfer to the top plate, but even in this short test, it still appears to be a problem.

Due to the slower heating times, this will be a bit more challenging to test as each test could take hours to complete, but this is more in line with the final intended use anyways. Perhaps my cycle of 1000ms on is too much (e.g. I should do 100ms on then 9900ms off, although I think that might be so slow that it will never heat up; this also raising the question as to how I will deal with mantaining this slow heat up at the higher temperatures).

Attachment 1: PWM_plates_-_1000_ms_on_9000_ms_off.pdf
Draft   Tue Oct 25 18:55:38 2022 Jennifer HritzGeneralOptical ContactingPWM 3.1 very slow heating

[I'm behind on data processing, but I'm creating an entry on the day I actually run the tests]

107   Fri Oct 21 22:22:37 2022 Jennifer HritzGeneralOptical ContactingPWM v2.6 on new thermocouple set up

I performed the same tests I have been doing prior (+180°C in 10 minutes) but now with the (correctly wired) thermocouples attached to the metal plates. The top plate is thermocouple #1 attached to the Fluke and the bottom plate is thermocouple #2 attached to the TPI (the lime green one).

The base heating rate for the new set up will require some tweaking to the code because the plates heat up much slower, but as I have mentioned previously, I do not think this will require a lot of extra work since I now know the tips and tricks to PWMing the hot plate. The only difficulty might come from the increase in hysteresis (i.e. the plates continue to increase in the temperature long after it turns off). For future tests, I need to remember to continue recording the temperature after program finishes its 10 min cycle.

On the positive, I think this test shows that taking the average of the two thermocouples to find the temperature in the center (where the optically contacted samples are) is a worthwhile endevor, considering how much the top plate lags behind the bottom plate in terms of heating speed.

Attachment 1: PWM_plates_-_increase_180°C_in_10_minutes.pdf
108   Sat Oct 22 21:18:56 2022 Jennifer HritzGeneralOptical ContactingPWM v3.0

With v3.0, I took a couple steps backwards by getting rid of the feature that increases the heating rate so I can isolate the base heating rate for the two plates. In my experience, the best way to figure out how to modify the program is to try a bunch of different target temperatures and heating times and look for correlations. I started with (attempting) to increase the plates by 280°C in 10 minutes.

For a future release, I am thinking of radically (relatively speaking) changing the function parameters: the user only inputs the target heating rate and how long the plates should be heated at this rate. This is to address the hysteresis in this new set-up, which I will elaborate on if I make the change.

Attachment 1: PWM_plates_-_increase_280°C_in_10_minutes.pdf
57   Sat Jul 2 09:22:39 2022 Juan GeneralGeneralProgress update

I've completed one coil driver board.
Hopefully next week I can finish the other 2 boards and make the modifications to the sat amp baords.

Attachment 1: IMG-5220.jpg
86   Fri Sep 30 21:51:31 2022 Jennifer HritzGeneralOptical ContactingQuick test heat and pressure test

Given that these glass slides are much thinner than the ones I worked with prior, I suspected they would be more receptive to pressure. I decided to replicate the tests I performed with the larger slides: I prepared 8 samples, 4 by smushing the slides together with methanol in the middle and another 4 by cleaning the slides with methanol before pressing them together with my fingers. I put 2 of each type under the cylindrical weight, and 2 of each type under the rectangular weight with the addition of heating. The heating consisted of switching the temperature from off --> low --> med --> high with 15 minutes on each setting.

I will check the results in the morning. I need to wait until the rectangular weight is completely cooled, otherwise I cannot remove it from the hot plate in manner that does not risk cracking the glass.

The first sample picture shows the pressed slides on the top and the smushed slides on the bottom. For the second picture, this is reveresed. Correction: the order is the same for both samples.

Attachment 1: pressure_set_up_PXL_20221001_040539385.MP.jpg
Attachment 2: samples_before_pressure_PXL_20221001_040441662.MP.jpg
Attachment 3: heat_w_pressure_set_up_PXL_20221001_033228622.MP.jpg
Attachment 4: samples_before_heat_w_pressure_PXL_20221001_034620991.MP.jpg
77   Tue Aug 16 19:54:29 2022 Jennifer HritzGeneralOptical ContactingRazor blade test

We succeeded in setting up an apparatus for quantifiying the razor blade test. After mounting the glass slides such that the razor edge rested against the gap, we slowly turned the knob to push the blade into the gap. We started with the knob at 0.111, and at 0.757, the bond between the glass slides failed. As we approached 0.757, the interference pattern in the glass shifted, foreshadowing the break.

(Edit by Koji. This 0.757 is 0.0757 I suppose...? And the unit is in inch)

Attachment 1: PXL_20220817_023737796.MP.jpg
Attachment 2: PXL_20220817_023741865.MP.jpg
82   Tue Sep 27 22:29:34 2022 Jennifer HritzGeneralOptical ContactingRazor test apparatus disassembly pictures

Pictures of the razor test apparatus before and after disassembly, to make future reassembly easier.

Attachment 1: razor_before_PXL_20220817_211123631.MP.jpg
Attachment 2: razor_after_PXL_20220911_062818511.MP.jpg
24   Thu Sep 9 11:25:30 2021 PacoGeneralDesign specsRerun HR coatings with n,k dispersion

[Paco]

I've re-run the HR coating designs for both ETM and ITM using interpolated dispersions (presumably at room temperature). The difference is shown in Attachment #1 and Attachment #2.

Basically, all features are still present in both spectral transmission plots, which is consistent with the relatively flat dispersions from 1 to 3 um in Silica and Tantala thin films, but the index corrections of a few percent from low-temperature estimates to room-temperature measured (?) dispersions are able to push the HR transmission up by a few (2-3) times. For instance, the ETM transmission at 2128.2 nm goes up by ~ 3. The new number is still well below what we have requested for phase I so this is in principle not an issue.

A secondary change is the sensitivity (the slope around the specified wavelength) which seems to have increased for the ETM and decreased for the ITM. This was another consideration so I'm running the optimizer to try and minimize this without sacrificing too much in transmission. For this I am using the stack as a first guess in an attempt to run fast optimization. Will post results in a reply to this post.

Attachment 1: etm_updated.pdf
Attachment 2: itm_updated.pdf
25   Thu Sep 9 20:42:34 2021 PacoGeneralDesign specsRerun HR coatings with n,k dispersion

[Paco]

Alright, I've done a re-optimization targetting a wider T band around 2128 nm. For this I modified the scalar minimization cost to evaluate the curvature term (instead of the slope) around a wide range of 10% (instead of 1%). Furthermore, in prevision of the overall effects of using the updated dispersion, I intentionally optimized for a lower T such that we intentionally overshoot.

The results are in Attachment #1 and Attachment #2.

Attachment 1: ETM210909190218.pdf
Attachment 2: ITMLayers210909204021.pdf
102   Sun Oct 16 14:20:32 2022 Jennifer HritzGeneralOptical ContactingSamples after 2 weeks under pressure

Since I was focusing on the hot plate code and therefore did not need my weights, I decided to leave them on top of my samples for roughly 2 weeks.

It appears that an increased amount of time under pressure does not result in any noticable differences. A slight increase in surface area (SA) in two places, and a slight decrease in SA in another place, but overall no change. Note that "(initally)" in the picture below refers to http://nodus.ligo.caltech.edu:8081/Mariner/89.

Attachment 1: 2_weeks_pressure_PXL_20221004_190652540_20221017_074745619.jpg
72   Thu Aug 4 11:26:55 2022 JuanGeneralGeneralSat Amp

Sat amp seems to be working just fine. There does seem to be a saturation issue with one of the outputs we may need to change a resistor on the board.

Attachment 1: IMG-6153.jpg
74   Mon Aug 8 13:00:56 2022 JuanGeneralGeneralSat Amp testing of OSEMS

In the following test, a single Sat Amp chassis that holds Sat Amp Board S1106078 and S1106077

Verification of Sat Amp

First, as the test of the LED driver circuits in the chassis, 8 of various color LEDs were inserted to the appropriate output pins of the chassis. This resulted in all the LED lit and the LED mon TP was confirmed to have voltage outputs of 5V. (See my previous ELOG)

OSEM tests

Connected OSEMs to the sat amp to test the OSEM LED/PD pairs. With the first test, the PD out gave us 15V. We wondered if this was just the problem of the OSEM or circuit, or just there are too much light for the transimpedance gain of 121K Ohm.

By blocking the OSEM light by a random heat shrink tube found on the table, we saw the number got reduced. This indicates that the OSEM/Satamp outputs are working and there are just too much light.

We decided to reduce the gain: The transimpedance gain R18 was reduced to 16k, which gave us a voltage range from 5V~7V  with some outlier OSEMS at 1V (See the attached table)

There are 24 total OSEMs:

• one apparently not functional
• 20 fell in the range of 5~7V
• 3 fell in the range of  ~1V

(These numbers given after the change of R18 to 16k Ohm)

Note: We originally aimed for 8~9V. However, from a previous study of OSEM at cryogenic temperature, we learned that there was about an about 30% increase in the response.
Therefore, we decided to leave a sufficient margin from 10V considering this expected increase in the response.

Attachment 1: OSEMs.xlsx
23   Thu Aug 26 17:40:41 2021 StephenGeneralSuspensionSelecting MOS-style frame

[Koji, Stephen]

Kind of a silly post, and not very scientific, but we are sticking to it. During our check in today we discussed Mariner suspension frame design concept, and we chose to proceed with MOS-style (4 posts, rectangular footprint).

- We looked at a scaled-up SOS (WIP, lots of things broke, just notice the larger side plates and base - see Attachment 1) and we were not super excited by the aspect ratio of the larger side plates - didn't look super stiff - or the mass of the base.

- We noted that the intermediate mass will need OSEMs, and accommodating those will be easier if there is a larger footprint (as afforded by MOS).

MOS-style it is, moving forward!

Also, Checked In to PDM (see Attachment 2 - filename 40mETMsuspension_small-shields.SLDASM and filepath \llpdmpro\Voyager\mariner 40m cryo upgrade ) the current state of the Mariner suspension concept assembly (using MOS). Other than updating the test mass to the 6" configuration, I didn't do any tidying up, so I'm not perfectly satisfied with the state of the model. This at least puts the assembly in a place where anyone can access and work on it. Progress!

104   Tue Oct 18 19:33:38 2022 Jennifer HritzGeneralOptical ContactingSetting up thermocouples

Firstly, last night's heating did not change the contacted surface area greatly, but there is too many factors to speculate as to why that is the case. I leave that for future testing.

I attached the thermocouples by adhering them to the two aluminum plates. I was careful to make sure that the thermocouple was in the dead center of the aluminum plate. The other end of the thermocouples—exposed positive and negative wires—were screwed into the K Type connector so they can be plugged into the thermometer/multimeter. Taking the average between the top and bottom plate will give a more precise estimate of the temperature of the samples.

Attachment 1: first_real_PWM_test_samples_before_after_PXL_20221018_080838426.MP.jpg
Attachment 2: K_Type_connector_PXL_20221019_000708969.MP.jpg
Attachment 3: thermocouple_plates_PXL_20221019_003002817.MP.jpg
4   Thu Mar 4 17:04:52 2021 PacoGeneralDesign specsSilicon TM dichroic coatings for phase I

Have been using the 40m Coatings repo code by Gautam (with some modifications to make dichroic designs under Ta2O5_Voyager), as well as the parameters compiled in the Mariner wiki for Silica-tantala thin films. Here are some of the top picks.

## ETM

For ETM, the target transmissivities are 5.0 ppm @ 2128.2 nm and 50.0 ppm @ 1418.8 nm. After different combinations of differential evolution walkers, numbers of layers, thickness bounds, a couple of different optimization strategies, the optimum design has consistently converged with 19 - 26 layer pairs (total of 38 - 52 layers). The picks are based on the sensitivities, E_field at the boundary, and a qualitatively uniform stack (discarded "insane-looking" solutions). The top picks in Attachment 1 may be a good starting point for a manufacturer. In order of appearance, they are:

1. ETM_210218_1632
2. ETM_210222_1621
3. ETM_210302_1210
4. ETM_210302_1454

## ITM

For ITM, the target transmissivities are 2000 ppm @ 2128.2 nm and 50.0 ppm @ 1418.8 nm (critically coupled cavity for AUX). The lower trans for 2128.2 nm made this easier faster to converge, although the number of thin film layers was equally centered about ~ 50 layers. Haven't explored as much in the parameter space, but the top picks in Attachment 2 are decent for approaching manufacturer. In order of appearance, they are:

1. ITM_210303_1806
2. ITM_210204_1547
3. ITM_210304_1714
Attachment 1: ETM_coating_candidates.pdf
Attachment 2: ITM_coating_candidates.pdf
6   Wed Mar 17 19:51:42 2021 PacoGeneralDesign specsSilicon TM dichroic coatings for phase I

### Update on ETM

New optima are being found using the same basic code with some modifications, which I summarize below;

1. Updated wavelengths to be 2128.2 nm and 1418.8 nm (PSL and AUX resp.)
2. The thickness sensitivity cost "sensL" previously defined only for 2128 nm, is now incorporating AUX (1418 nm) in quadrature; so sensL = sqrt(sens(2128) ** 2 + sens(1418)**2)
3. There is now a "starfish" plot displaying the optimized vector cost. Basically, the scores are computed as the inverse of the weighted final scalar costs, meaning the better stats reach farther out in the chart. One of these scalar costs does not actually belong to the optimization (stdevL) and is just a coarse measure of the variance of the thicknesses in the stack relative to the average thickness.
4. Included a third wavelength as transOPLV (for the OPLEV laser) which tries to get R ~ 99 % at 632 nm
1. Imagine,... a third wavelength! Now the plots for the transmissivity curves go way into the visible region. Just for fun, I'm also showing the value at 1550 nm in case anyone's interested in that.
5. Adapted the MCMC modules (doMC, and cornerPlot) to check the covariance between the transmissivities at 2128 and 1418 for a given design.
6. Reintroduced significant weights for TO noise and Brownian noise cost functions (from 1e-11 to 1e-1) because it apparently forces solutions with lower thickness variance over the stack (not definitive, need to sample more)

Still working to translate all these changes to ITM, but here are samples for some optimum.

• Attachment 1 shows the spectral reflectivity/transmissivity curves with a bunch of labels and the transparent inset showing the starfish plot. Kind of crazy still.
• Attachment 2 shows the stack. Surprisingly not as crazy (or maybe I have internalized the old "crazy" as "normal")
• Attachment 3 shows a very simple corner plot illustrating the covariance between the two main wavelengths transmissions.
Attachment 1: ETM_R_210317_1927.pdf
Attachment 2: ETM_Layers_210317_1927.pdf
Attachment 3: ETM_nominal_cornerPlt.pdf
7   Wed Mar 17 21:24:27 2021 gautamGeneralDesign specsSilicon TM dichroic coatings for phase I

I guess you have tried it already - but does enforcing the stacks to be repeating bilayer pairs of the same thickness fail miserably? When doing this for the PR3 optic @1064nm, I found that the performance of a coating in which the layers are repeating bilayers (so only 2 thicknesses + the cap and end are allowed to vary) was not that much worse than the one in which all 38 thicknesses were allowed to vary arbitrarily. Although you are aiming for T=50ppm at the second wavelength (which isn't the harmonic) which is different from the PR3 reqs. This kind of repetitive structure with fewer arbitrary thicknesses may be easier to manufacture (and the optimizer may also converge faster since the dimensionality of the space to be searched is smaller).

Cool starfish 🌟 . What is the interpretation of the area enclosed by the vertices? Is that the (reciprocal) cost? So the better solution maximizes the area enclosed?

Quote:

### Attachment 2 shows the stack. Surprisingly not as crazy (or maybe I have internalized the old "crazy" as "normal")

9   Wed Mar 24 17:42:50 2021 PacoGeneralDesign specsSilicon TM dichroic coatings for phase I

Yeah, the magnitudes are the inverse weighted scalar costs (so they lie on the appropriate relative scale) and indeed larger enclosed areas point to better optima. I would be careful though, because the lines connecting the scalar costs depend on the order of the vector elements (for the plot)... so I guess if I take the cost vector and shuffle the order I would get a different irregular polygon, but maybe the area is preserved regardless of the order in which the scalars are displayed...

 Quote: Cool starfish 🌟 . What is the interpretation of the area enclosed by the vertices? Is that the (reciprocal) cost? So the better solution maximizes the area enclosed?

Attached is a cartoon partial view into the heat load experienced by the Mariner assembly.

The omnigraffle file with more explicit arrow labelling in the 'layers' tab is available here. The dashed red lines along to top represent vacuum chamber radiation incident on all sides of the OS/IS, not just from the top. Off picture to the right is the BS, left is the beam tube/ETM chamber -- hence the lower absored laser power (solid line) absorbtion (PR power + no HR coating absorption).

Parameters:

• Emissivities are listed outside the cartoon.
• Shields consist of polished aluminum outer surfaces and high emissivity inner surfaces.
• 1 W input power, 50 W power recycling, 30 kW cavity power
• All shields held at 77K
• 20 ppm/cm bulk silicon absoprtion, 5 ppm coating absorption

Assumptions

• Steady state condition, where the shields are able to be cooled/held to 77K
• Holes punched into the inner shield for stops, magnets, etc are assumed to shine RT light onto 123K TM
• This is very conservative, MOS will stablize at some temp and the OS should block ~all vacuum chamber radiation not funneled through inner shield snout

Missing or wrong

• [M] Contribution of MOS conduction and emission on the outer shield heat budget
• [M] Inner shield
• [W] OS inner surface currently modelled as one surface seeing incident RT light, need to accomodate the view factor of each of the 5 high e sides to the open maw of the OS
• [M] Conduction through shield masses, how efficient is it to link them with straps
• [M] no AR coating absorption
• [M/W] Cold finger cooling power from room temp shield to 77K cryocooler ('wrong' label because 61W is only the heat load once shields are cooled):
• Worst case to reach: 1.5m connection between tank flange and shield (from flange at bottom of the tank)
• Phosphorous deoxidized copper:  5 cm diameter
• ETP copper:  3.5 cm diameter
• Best case: 0.5m connection, from flange at level of OS
• Phos deox Cu: 3 cm diameter
• ETP Cu: 2 cm diameter
• ​​​$q_{\text{conductive}} = \frac{A}{L} \left[\int_{4\, \text{K}}^{T_2} \lambda(T) dT - \int_{4\, \text{K}}^{T_1} \lambda(T)dT \right]$
73   Thu Aug 4 13:44:56 2022 Jennifer HritzGeneralOptical ContactingSuccess with slowly heating

Yesterday, I did two rounds of slowly heating 4 samples to the maximum hot plate temperature. This was to formally test if my success with a single sample earlier in the week was a fluke. Note that the hot plate takes about 10-15 minutes to reach a stable temperature when it is turned up one notch.

First round:
I bonded 4 samples by putting methanol in the gap between the glass slides and letting it dry to create a gap.
Starting at room temperature, I heated the slides on each setting for roughly 15 minutes, then let them cool down naturally over the course of an hour. 3 broke broke at medium heat, and 1 survived the whole process. I belive these broke because the bonds were weaker and I heated them slightly too quickly. In previous tests, I would manually switch the hot plate on and off, but I wanted to see if the hot plate could heat up slow enough on its own.

Second round:
I bonded 4 samples by scrubbing the slides with methanol, using a compressed air duster to blow off the fibers, rubbing them together with the pressure of my fingers, and repeating this whole procedure until they stuck (it took 2-4 repeats).
Starting at room temperature, I heated the slides on each setting for exactly 20 minutes, then let them cool down naturally over the course of an hour. All of them survived to the maximum temperature (the pictures show them at the start and end of the heating, note the temperature). I credit this to the stronger bonding proceedure and the extra 5 minutes for them to adjust to the temperature. I did not turn the hot plate on or off at any point, I just let it heat up at its own rate.

I cannot tell if the bonds are stronger. The size and shape of the Newtons rings did not change.

Attachment 1: PXL_20220803_232203193.jpg
Attachment 2: PXL_20220804_002433906.jpg
34   Fri Oct 1 12:01:24 2021 PacoGeneralDesign specsTM Barrel coating emissivity

[Paco, Nina, Aidan]

We ran our stack emissivity calculation on different AR stacks to try and make a decision for the TM barrel coatings. This code has yet to be validated by cross checking against tmm as suggested by Chris. The proposed layer structures by Aidan and Nina are:

1. *| Air || SiO2 x 800 nm || Ta2O5 x 5 um || Silicon |*
2. *| Air || Ta2O5 x 10 um || Sio2 x 20 nm || Silicon |*
3. *| Air || SiO2 x 100 nm || TiO2 x 1 um || Silicon |*

Attachments # 1-3 show the emissivity curves for these simple dielectric stacks. Attachment #4 shows the extinction coefficient data used for the three different materials. The next step is to validate these results with tmm, but so far it looks like TiO2 might be a good absorbing film option.

Attachment 1: stack_1.pdf
Attachment 2: stack_2.pdf
Attachment 3: stack_3.pdf
Attachment 4: interpolated_n_k.pdf
35   Fri Oct 1 13:24:40 2021 AidanGeneralDesign specsTM Barrel coating emissivity

I have to question whether this passes a sanity test. Surely in the case of Stack 2, the 10um thick Ta2O5 will absorb the majority of the incident radiation before it reaches the SiO2 layer beneath. It should at least be similar to just absorption in Ta2O5 with some Fresnel reflection from the AIr-Ta2O5 interface.

For example, at around 18um, K~2, so the amplitude attenuation factor in a 10um thick layer is 160,000x or a gain of 6E-6. So whatever is under the Ta2O5 layer should be irrelevant - there is negligible reflection.

 Quote: [Paco, Nina, Aidan] We ran our stack emissivity calculation on different AR stacks to try and make a decision for the TM barrel coatings. This code has yet to be validated by cross checking against tmm as suggested by Chris. The proposed layer structures by Aidan and Nina are: *| Air || SiO2 x 800 nm || Ta2O5 x 5 um || Silicon |* *| Air || Ta2O5 x 10 um || Sio2 x 20 nm || Silicon |* *| Air || SiO2 x 100 nm || TiO2 x 1 um || Silicon |* Attachments # 1-3 show the emissivity curves for these simple dielectric stacks. Attachment #4 shows the extinction coefficient data used for the three different materials. The next step is to validate these results with tmm, but so far it looks like TiO2 might be a good absorbing film option.

36   Fri Oct 1 14:11:23 2021 PacoGeneralDesign specsTM Barrel coating emissivity

Agree with this. Quickly running tmm on the same "stacks" gave the Attachment #1-3. (Ignore the vertical axis units... will post corrected plots) and extend the wavelength range to 100 um.

Attachment 1: stack_1.pdf
Attachment 2: stack_2.pdf
Attachment 3: stack_3.pdf
ELOG V3.1.3-