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New entries since:Wed Dec 31 16:00:00 1969
ID Date Authorup Type Category Subject
  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)

- radiative heating from room-temp tube snout (function of snout radius and length, and TM radius)

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

 

 

 

 

  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 1: Heat_Load_Sketch_geometry.pdf
Heat_Load_Sketch_geometry.pdf
Attachment 2: Heat_Load_Sketch_diagram.pdf
Heat_Load_Sketch_diagram.pdf
Attachment 3: heating_cooling_P_vs_T.pdf
heating_cooling_P_vs_T.pdf
Attachment 4: CooldownTM_radiative.pdf
CooldownTM_radiative.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 1: Heat_Load_Sketch_all.pdf
Heat_Load_Sketch_all.pdf
Attachment 2: VaryingISA.pdf
VaryingISA.pdf
Attachment 3: CooldownTM.pdf
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
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
VaryingISA.pdf
Attachment 2: VaryingTMl.pdf
VaryingTMl.pdf
  79   Fri Aug 26 14:24:57 2022 RadhikaGeneralHeat LoadMariner TM Cooldown model

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 1: Mariner_Heat_Load_Sketch.pdf
Mariner_Heat_Load_Sketch.pdf
Attachment 2: MarinerTMCooldown.pdf
MarinerTMCooldown.pdf
Attachment 3: TMPowerBudget.pdf
TMPowerBudget.pdf
Attachment 4: ISPowerBudget.pdf
ISPowerBudget.pdf
Attachment 5: CagePowerBudget.png
CagePowerBudget.png
Attachment 6: OSPowerBudget.pdf
OSPowerBudget.pdf
  80   Mon Aug 29 15:44:46 2022 RadhikaGeneralHeat LoadMariner TM Cooldown model

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
VaryingSnoutparams.pdf
Attachment 2: MarinerTMCooldown_snout_optimal.pdf
MarinerTMCooldown_snout_optimal.pdf
  81   Wed Sep 7 10:42:12 2022 RadhikaGeneralHeat LoadMariner TM Cooldown model

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
SnoutLengthCooldownTM.pdf
  128   Wed Apr 12 12:03:34 2023 RadhikaGeneralHeat LoadMariner TM Cooldown model

Here we lay out the Mariner cryocooler requirements and discuss the most recent cooldown model, which includes a cryocooler that cools down the inner shield and a separate LN2 dewar that cools the outer shield.

The chosen cryocooler must supply at least 2x the cooling power to the TM than the heat loads on the TM, at 123 K. Implicit in this requirement is that in the absense of temperature control, the cooling power must be enough to cool the TM to well below 123 K.

Attachment 1 is the latest Mariner ITM cooldown model. This updated model is pushed to mariner40/CryoEngineering/MarinerCooldownEstimation.ipynb. Before running the notebook you can toggle between IS cooling sources: LN2, DS30, CH-104, or in the future any crycoolers we are considering. All attachments are generated using the cooling curve of the DS30. 

Since the OS is no longer a heat load on the cryocooler, the IS gets cooled more efficiently and reaches within 5 K of the coldhead. The heat loads on the TM (snout, apertures, laser heating) make its temperature plateau just under 100 K. It reaches 123K in ~50 hours.

Attachment 2 is a power budget for the TM. We see that at 123K, the heat loads sum to ~0.4 W. The cooling power at this temperature is around 1 W. The DS30 satisfies our cryocooler cooling requirement; however vibration requirements / vacuum interface compatibility still need to be determined.

Lastly, Attachment 3 is an updated block diagram of the heat transfer couplings considered by the model. (The model also considers radiative links between the inner shield and cage, and inner shield and upper mass; these are omitted from the diagram for simplicity.)

Attachment 1: MarinerTMCooldown_LN2_OS.pdf
MarinerTMCooldown_LN2_OS.pdf
Attachment 2: TMPowerBudget.pdf
TMPowerBudget.pdf
Attachment 3: mariner_block_diagram_joints.pdf
mariner_block_diagram_joints.pdf
  129   Fri Jun 2 11:31:29 2023 RadhikaGeneralHeat LoadMariner TM Cooldown model

Summarizing the current Mariner ITM cooldown model assumptions:

- Inner shield and outer shield have snouts of equal length (1 m end-to-end)

- Laser off during cooldown

- Inner shield cooled by DS30; outer shield cooled by LN2 tank

- ITM barrel emissivity = 0.9

Takeaways:

1) Time to cool to 123 K: ~30 h (radiative cooling limit: 20 h). See Attachment 1
2) 1W cooling power delivered to ITM at 123 K [Attachment 2]
3) ~5W cooling power delivered to inner shield at steady state [Attachment 3]
4) ~28W cooling power delivered to outer shield at steady state [Attachment 3]

A simplified block diagram can be found in Attachment 4. 

Attachment 1: MarinerITMCooldown_2023-05-31_ref.pdf
MarinerITMCooldown_2023-05-31_ref.pdf
Attachment 2: MarinerTMPowerBudget.pdf
MarinerTMPowerBudget.pdf
Attachment 3: MarinerTotalCoolingPower.pdf
MarinerTotalCoolingPower.pdf
Attachment 4: Mariner_ITM_SUS_blockdiagram4.pdf
Mariner_ITM_SUS_blockdiagram4.pdf
  130   Fri Jun 23 15:37:39 2023 RadhikaGeneralHeat LoadMariner TM Cooldown model

I simulated the Mariner cooldown with an additional LN2 tank connected to the main cold strap shared by the cryocooler. LN2 can aid in the initial cooldown from room temperature, and once the inner shield is sufficienly cold the cryocooler can take full control. (The LN2 should not be on the whole time - once the inner shield crosses 77K the LN2 would be contributing heat.) In the model I chose the inner shield temperature of 90K to signal when to turn off the LN2 (any lower and the IS temperature starts to flatten out as it approaches 77K).

The closer the LN2 tank sits towards the chamber/IS (and away from the cold head), the better. This is because the cold head of the cryocooler drops rapidly to ~60K, and the LN2 joint would contribute to heating the cold head. Plus, the cooling of the IS is more efficient if the LN2 source is closer. The model assumes the LN2 tank sits halfway between the coldhead of the cryocooler and the inner shield.

The last assumpion made is that the LN2 tank volume is large enough such that the tip in contact with LN2 remains at 77K. 

In Attachment 1, the dashed traces show the cooldown of the cold head, inner shield, and test mass without the additional LN2 cooling. The solid traces include LN2 cooling and use the assumptions above in green. We see that the inner shield is cooled significantly faster with LN2 (on par with the cold head until 150K). As a result, the heat load the inner shield puts on the cold head is reduced, and that reduction more than compensates for the additional heating on the cold head from the LN2 at 77K. Thus the cold head cools much faster in the first 10 hours. The kinks in the cold head/inner shield traces are presumably from the system re-equilibriating after the LN2 source is shut off - it's not clear why the cryocooler doesn't immediately continue the downward trend.

The effect on the test mass is more subtle, but we see the test mass cools to 123K ~2 hours faster (in 28 h). I was then curious if we could get the same gains by simply moving the cryocooler/cold head halfway closer to the inner shield. This simulation is in Attachment 2 - it takes ~1 h longer for the test mass to reach 123K, since we don't get the added cooling power from the LN2.

While there's merit to the additon of LN2, maybe an improvement of a few hours isn't enough to justify the increase in complexity.

 

Attachment 1: MarinerCooldown_withLN2.pdf
MarinerCooldown_withLN2.pdf
Attachment 2: MarinerITMCooldown_halfCstrapL.pdf
MarinerITMCooldown_halfCstrapL.pdf
  132   Fri Aug 4 17:07:41 2023 RadhikaGeneralHeat LoadMariner TM Cooldown model

Here is the model including an additional LN2 tank aiding in inner shield cooldown, applied to Voyager [Attachment 1]. The same assumptions have been made as in the previous ELOG. The LN2 is switched off once the inner shield reaches 90K.

Using LN2 in such a way cools down the test mass to 123K 5 hours faster. This is a ~6% improvement from the original 85 hours of cooldown [Attachment 2]. Note that the fundamental radiative cooling limit for a Voyager-like test mass is ~68 hours.

Attachment 1: VoyagerITMCooldown_with_LN2.pdf
VoyagerITMCooldown_with_LN2.pdf
Attachment 2: VoyagerITMCooldown_2023-05-31_ref.pdf
VoyagerITMCooldown_2023-05-31_ref.pdf
  138   Fri Aug 25 13:25:05 2023 RadhikaGeneralGeneralSummary of JPL/Ball cryocooler discussion

Here is a summary of the cryocooler discussion hosted at JPL. 

Dave Glaister of Ball Aerospace presented on their low-vibration cryocooler assemblies (CCAs). A summary of their work can be found in this paper. Ball has their own cryocooler vibration testing setup that they use to assess/characterize their platforms. They did not show frequency-dependent vibration noise with/without their assemblies, but they advertized up to 50x reduction in noise at 50-60 Hz. The paper above does show a spectrum of sorts (unknown units) but it does not display data below 50 Hz. Notably, they have experience in augmenting the Sunpower DS-30 cooler which meets the Mariner cooling requirements (though their CCAs should be cooler-agnostic). 

Notes from their meeting:

- Fanciest Sunpower DS-30 CCA (with all the bells+whistles): $2 million; 12-24 month lead time. Results in few mN of vibration.

- Yukon Soft Ride CCA for Sunpower DS-30 - lowest cost; in the $100,000 range if they use cheaper electronics.

          -vibration attenuation 8x

- They suggested the option of circulating gas instead of a cryocooler for our needs: helium gas lines; keep compressor outside IFO to eliminate almost all vibration.

The Yukon CCA seems to be a reasonable baseline to discuss with them. They can customize to our needs. We should ask them to provide us with vibration measurements of the DS-30 cooler with and without their Yukon CCA down to 1 Hz.

  3   Fri Jun 5 11:13:50 2020 RaymondGeneralHeat LoadSteady state heat load example

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 
  • IS snout radius is equal to TM radius
  • 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]
Attachment 1: Heat_Load_Sketch.pdf
Heat_Load_Sketch.pdf
  118   Sat Jan 7 17:08:47 2023 Sophia AdamsGeneralOptical Contacting 

I am getting started on building the arduino circuit as well as setting up my computer so I can communicate between jupyter notebook and the arduino. I will need a USB adapter for my computer before I can make much more progress.

  119   Mon Jan 9 16:18:50 2023 Sophia AdamsGeneralOptical Contacting 

I was able to get a USB adapter for my computer so I could test my code. The Arduino can read the temperature of the room and output the values with a tenth of a second time delay. Jupyter Notebook recognizes the Arduino and can receive temperature data from it.

Attachment 1: arduinoRoomTempReading.jpg
arduinoRoomTempReading.jpg
  125   Thu Feb 2 17:28:37 2023 Sophia AdamsGeneralOptical ContactingTest of Temperature Reading of One Plate

The arduino was able to read temperature data and send it to a python program that graphed the data.

Attachment 1: bokeh_plot.png
bokeh_plot.png
  131   Mon Jun 26 13:53:40 2023 Sophia AdamsGeneralOptical Contactingcantilever geometry to find the quality factor of a silicon bond

I am trying to design a cantilever setup to find the quality factor of optically bonded silicon. The cantilever will be given an impulse, and the ring down will be measured. In order to determine the Q of the bond, the relative energy contributions from each part of the cantilever must be analyzed. The primary energy contribution should come from the bond.

 

The below equations come from https://roymech.org/Useful_Tables/Beams/Strain_Energy.html. I believe the relevant ones are the bending and traverse shear energies.

 

c = distance from neutral axis to outer fibre(m)

E = Young's Modulus (N/m2)

F = Axial Force (N)

G = Modulus of Rigidity (N/m2)(m)

I = Moment of Inertia (m4)(m)

l = length (m)

M = moment (Nm)

V = Traverse Shear force Force (N)

x = distance from along beam (m)

z = distance from neutral (m)

γ = Angular strain = δ/l

δ = deflection (m)

τ = shear stress (N/m2)

τ max = Max shear stress (N/m2)

θ = Deflection (radians)

 

 

 

 

 

The young’s modulus (E) of silicon is 130 to 188 GPa from a quick google search. The shear modulus (G) is 50 – 80 GPa. The calculation is easier when using a rectangular beam. In that case, (U traverse) / (U bending) ~ 1.2 * V^2/(50 * bh * M^2) * (bh^3/12 * 188) = (.376 to .16) * (V^2)(h^2)/(M^2) where M depends on the distance from the applied force.

 

For a circular beam, height is swapped out for diameter, K is 1.11, and I = pi/64 d^4. (U traverse) / (U bending) ~ (.26 to .11) * (V^2)(d^2)/(M^2), which means (U bending) / (U traverse) ~ (3.8 to 9) * (M^2)/((V^2)(d^2)).

 

However, for a cantilever beam with the bond on the neutral axis, the maximum shear energy would be at the bond. For gentle nodal suspension, the maximum bending energy would be at the top and bottom.

 

 

Attachment 1: Picture1.jpg
Picture1.jpg
  133   Tue Aug 22 10:16:54 2023 Sophia AdamsGeneralOptical ContactingMatlab fminsearch Cantilever Geometry Optimization

I am trying to use fminsearch to find the best cantilever dimensions to maximize the bond/cantilever energy ratio. Fminsearch takes in a function and a set of intial parameters. The function that is passed in should be a function of the parameters, but my getEnergy function does not work unless the COMSOL model is passed in as an argument. I tried to make a helper function, but I run into the same problem.

 

After running getRatio (attempted helper function):

 

>> getRatio
The COMSOL model is now accessible using the variable 'model'
Unrecognized function or variable 'model'.

Error in getRatio (line 3)
ratio = getEnergy(model, L, h, d)
 
>> 

Attachment 1: getEnergy.m
function ratio = getEnergy(model, L, h, d)
model.param.set('base_width', append(num2str(d), '[mm]'));
model.param.set('base_height', append(num2str(h), '[mm]'));
model.param.set('length', append(num2str(L), '[cm]'));
model.study('std2').run
data = model.result.numerical('int1').getReal;
bondenergy = model.result.numerical('int2').getReal;
min = data(3)/bondenergy(1);
for i = 1:1:6
    if data(i*3)/bondenergy(i) < min
... 5 more lines ...
Attachment 2: getRatio.m
function ratio = getRatio(L, h, d)
mphopen('C:\Users\sadams\Downloads\RectangularCantilever.mph')
ratio = getEnergy(model, L, h, d)
end
Attachment 3: fminSearch.m
mphopen('C:\Users\sadams\Downloads\RectangularCantilever.mph')
x0 = [2, 0.3, 0.55];
x = fminsearch(getEnergy, x0)
  134   Tue Aug 22 12:12:05 2023 Sophia AdamsGeneralOptical ContactingMatlab fminsearch Cantilever Geometry Optimization

The code works now. If the function is specified by a file, there should be an @ symbol front of it when it is passed into fminsearch.

Quote:

I am trying to use fminsearch to find the best cantilever dimensions to maximize the bond/cantilever energy ratio. Fminsearch takes in a function and a set of intial parameters. The function that is passed in should be a function of the parameters, but my getEnergy function does not work unless the COMSOL model is passed in as an argument. I tried to make a helper function, but I run into the same problem.

 

After running getRatio (attempted helper function):

 

>> getRatio
The COMSOL model is now accessible using the variable 'model'
Unrecognized function or variable 'model'.

Error in getRatio (line 3)
ratio = getEnergy(model, L, h, d)
 
>> 

 

  135   Tue Aug 22 13:14:22 2023 Sophia AdamsGeneralOptical ContactingMatlab fminsearch Cantilever Geometry Optimization

Restricting the search to nothing less than the initial parameters (L = 2 cm, h = 0.3 mm, d = 0.55 mm), fminsearch outputs L = 2.0088 cm, h = 0.3000 mm, d = 0.5776 mm.

With the search restricted to L >= 1 cm, h >= 0.1 mm, and d >= 0.5 mm, fminsearch outpus L = 1.0313 cm, h = 0.1000 mm, and d = 0.5033 mm.

Quote:

The code works now. If the function is specified by a file, there should be an @ symbol front of it when it is passed into fminsearch.

Quote:

I am trying to use fminsearch to find the best cantilever dimensions to maximize the bond/cantilever energy ratio. Fminsearch takes in a function and a set of intial parameters. The function that is passed in should be a function of the parameters, but my getEnergy function does not work unless the COMSOL model is passed in as an argument. I tried to make a helper function, but I run into the same problem.

 

After running getRatio (attempted helper function):

 

>> getRatio
The COMSOL model is now accessible using the variable 'model'
Unrecognized function or variable 'model'.

Error in getRatio (line 3)
ratio = getEnergy(model, L, h, d)
 
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  136   Wed Aug 23 11:13:58 2023 Sophia AdamsGeneralOptical ContactingMatlab fminsearch Cantilever Geometry Optimization

I am trying to get a plot of the fminsearch data, but I was not sure how to extract the data. But fminsearch has built in plots that I think capture the data pretty well.

Attachment 1: fminsearch_fvalplot.fig
Attachment 2: fminsearch_graph.pdf
fminsearch_graph.pdf
  137   Wed Aug 23 16:34:47 2023 Sophia AdamsGeneralOptical ContactingMatlab Cantilever Geometry Optimization

Here is the code to generate a random list of parameters and evaluate the energy ratio of each. 

Attachment 1: optimizingParameters.m
mphopen('C:\Users\sadams\Downloads\RectangularCantilever.mph')
L = rand(100) * 200 + 10;
d = rand(100) * 10 + 0.3;
h = rand(100) * 5 + 0.1;
y = zeros(300);
for i = 1:1:length(L)
    model.param.set('base_height', append(num2str(h(i)), '[mm]'));
    model.param.set('length', append(num2str(L(i)), '[mm]'));
    model.param.set('base_width', append(num2str(d(i)), '[mm]'));
    model.study('std2').run
... 9 more lines ...
Attachment 2: RectangularCantilever.mph
  2   Thu May 21 12:10:03 2020 StephenGeneralResourcesOngoing Mariner Resources

Ongoing points of updates/content (list to be maintained and added)
Mariner Chat Channel
Mariner Git Repository
Mariner 40m Timeline [2020-2021] Google Spreadsheet
 

  5   Fri Mar 5 11:05:13 2021 StephenGeneralDesign specsFeasibility of 6" optic size in CAD

6" vs 4" optic size comparison using CAD - worth hopping into the 3D geometry using the link below, but also posting a couple of images below.

1) We can adjust all parameters relating to the suspension frame except the beam height. Is there enough clearance under the optic for the internal shield?

--> Using the representation of the MOS structure as-is, there is about 1" of clearance between the bottom panel of the first/internal shield under the 6" case, compared with 2" of clearance in the 4" case. This is not very scary, and suggests that we could use a 6" optic size.

2) Any other concerns at this point?

--> Not really, there are degrees of freedom to absorb other issues that arise from the simple 4" --> 6" parameter shift

EASM posted at https://caltech.app.box.com/folder/132918404089

 

Attachment 1: 4in_from_20210305_easm.png
4in_from_20210305_easm.png
Attachment 2: 6in_from_20210305_easm.png
6in_from_20210305_easm.png
  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
mariner_suspension_test_chamber_concept.jpg
  17   Wed Jun 30 16:21:53 2021 StephenGeneralDesign specs 

[Stephen, Koji]

WIP - check layout of 60 cm suspension in chamber at 40m, will report here

WIP - also communicate the

  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

  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!

Attachment 1: no_sos_cad_screenshot.png
no_sos_cad_screenshot.png
Attachment 2: vault_check_in_of_mariner_suspension_cad.png
vault_check_in_of_mariner_suspension_cad.png
  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
ELMO_specs.png
Attachment 2: HNLF_specs.png
HNLF_specs.png
Attachment 3: SimulationResults1.png
SimulationResults1.png
Attachment 4: SimulationResults3.png
SimulationResults3.png
  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")

  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?

  52   Tue May 10 18:29:11 2022 ranaGeneralSuspensionMariner Suspension Cryo shield Install / Removal steps

Transformers Optimus GIF - Transformers Optimus Prime - Discover & Share  GIFs

cool

 

  60   Thu Jul 7 15:20:04 2022 ranaGeneralOptical Contactingsome useful links

For our optical contacting, Jennifer and I are starting out with glass (microscope slides), with the setup in the EE shop next to the drill press (photos from Jennifer to follow).

Some interesting links:

  • https://www.laserfocusworld.com/optics/article/16546805/optical-fabrication-optical-contacting-grows-more-robust is a write up on contacting, and the link to Dan Shaddock's paper is also useful (need to sign up to get the acutal TSP writeup)
  • Thesis on Silicon Bonding (https://escholarship.org/uc/item/5bm8g42k)
  • https://youtu.be/qvBoGoh_-AE
  114   Thu Oct 27 22:12:21 2022 ranaGeneralOptical Contactingplotting and PID

The Arduino / AC PWM interface looks good. I recommend that you maintain the code in GitHub and post a link to the repo whenever you update the code. Use detailed commit messages so that it makes sense.

For the plotting, it would be good if you can use grid lines and markers for the data points. Then we can see the difference between the data and the fits, etc.

And to avoid the hysteresis, etc. you can record the temperature in your Arduino and use feedback to make the heater just go to whatever temperature you specify. So you would have a prescribed T(t) and the PID feedback loop would just make the heater take you there. Can your Arduino read the thermocouple?

ELOG V3.1.3-