ID 
Date 
Author 
Type 
Category 
Subject 
50

Wed Dec 15 06:43:43 2021 
Jiri Smetana  General  General  Lagrangian Model  Translation & Pitch 
I've checked the validity of my state space model in a couple of ways so that we have confidence in the results that it gives. I've checked the DC gain of the transfer functions where it is nonzero. I did this by solving the static balance of forces problem in the extended body model by hand to get the DC CoM position as well as the pitch angle of both masses. In the previous ELOG entry I didn't quite do this for all transfer functions so here I completed the check. My values agree with the model's values to within 10% at the worst end and to within 0.1% at the best end. I performed a second check to see if the frequencies occur in the correct places by considering the case of very low coupling between the different resonant modes. It's difficult to check this in the case where the modes are strongly coupled (for example lengthpitch is strong or the two pitch modes are close together) but if I sufficiently separate them, I get very good agreement between my analytic approximation and the state space model.
The model can easily be converted from one that gives motion in X and RY into one that gives motion in Y and RX. Running the model for both directions gives the following list of resonances (note pendulum modes in X and Y direction are identical):
Resonance Type 
Frequency [Hz] 
Pendulum 1 
0.85 
Pendulum 2 
2.10 
Pitch 1 
0.46 
Pitch 2 
2.37 
Roll 1 
17.13 
Roll 2 
46.09 
Given that I think the model seems to give sensible values, I've pushed the updated model to the GitLab repository. It is now possible to quickly change the parameters of the suspension and very quickly see the corresponding shift in the resonances. To change the parameters, open the plain text file called 'params' and change the values to the new ones. Afterwards, run the file 'ss_extended.py', which will solve the state space model, save the resulting ABCD matrices to a folder and print out the values of the resonances to terminal.
Quote: 
I've been having a look at the transfer functions for the translation and pitch of both masses. I'm attaching the plot of all inputtooutput transfer functions of interest so far. Here I've identified the pitch resonances of the two masses (one each) as well as the two pendulum modes. I need to now investigate if they occur in the correct places. I have confirmed the DC response by directly solving the statics problem on paper.


53

Thu Jun 16 14:04:30 2022 
Juan  General  Suspension  Table for Mariner Suspension Cryo 
Today we looked at possible locations for where we will be setting up Mariner Suspension and Cryo chamber. The first option was the far left table in the CAML lab but it seems that there is going to be an issue with height clearance, so we have come up with another solution which takes a table from Koji's lab which is 3'x4' ft and moving it into CAML lab in the back right of the lab. To move the table we may need to call facilities to help us because we will most likely need to take the table apart to get it out of the lab. The aisle space in Koji's lab is about 43 inches, but the doorway, which is the tightest space, is 35 inches.
After we have set up the table in CAML we are planning on moving the Chamber in DOPOlab to CAML. We plan to use skyhook with has a load limit of 500lbs/227kg this should be more than enough to move the chamber. We still need to get the wheeled base for skyhook we are in the works in doing so.
Also, We want to remove the previous setup from the chamber and leave it at DOPOlab. Stephen is going to figure out how to keep it clean (sort of). Besides these transportation logistics, I am also working on the electronics as an immediate task and the electrical arrangement in the chamber.
to do list
 Check the table height
 Check the chamber height (base/cap)
 Check how much the chamber cap needs to be lifted (so that we can remove it)
 Is the weight capacity sufficient?

56

Mon Jun 27 08:22:22 2022 
Juan  General  General  General Update/ Need to do task 
I've managed to cut and crimp wires for the power board for coil driver. I will begin adding components to the coil driver board.
 Add Components to Coil Driver board
 Replace some Sat Amp Componetns
 Still working on moving optical table to CAML
 Unsure if cryochamber has been cleaned and moved 
Attachment 1: coildrive.jpg


58

Tue Jul 5 21:06:47 2022 
Juan  General  General  Work Update 
Update of my current work I have finished one coil driver board and started on the last two that I need here is the progress and Ideally, I'll finish by tomorrow. 
Attachment 1: IMG5362.jpg


Attachment 2: IMG5361.jpg


59

Thu Jul 7 10:23:04 2022 
Juan  General  General  Update 
Almost done with coil driver boards 
Attachment 1: IMG5378.jpg


Attachment 2: IMG5379.jpg


61

Fri Jul 8 17:09:10 2022 
Juan  General  General  Coil Driver and Sat Amp 
All three coil driver boards are complete and have been tested. Modification for all 4 sat amp have been completed. Ideally, I would like to finish all the chassis on Monday I have one just about done.

Attachment 1: IMG5434.jpg


Attachment 2: IMG5421.jpg


Attachment 3: IMG5420.jpg


64

Mon Jul 11 17:39:17 2022 
Juan  General  General  Coil driver chassis 
Finished all 3 Coil Drover chassis and power lines still need to install the rear cables will do that after I finish Sat Amp chassis tomorrow. 
Attachment 1: IMG5493.jpg


Attachment 2: IMG5494.jpg


65

Wed Jul 13 13:16:33 2022 
Juan  General  General  Finished coil driver and sat amp 
I have finished all coil driver and sat amp chassis they all seem to be functioning properly.

Attachment 1: IMG5553.jpg


69

Fri Jul 22 13:47:47 2022 
Juan  General  General  Update 
Just a general update of what I have been up to deriving Lagrange for double pendulum system and also been looking at code that koji gave to me I've add comment to some of the code also working on my report. 
70

Tue Jul 26 14:17:44 2022 
Juan  General  General  OSEMS 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: IMG6050.jpg


Attachment 2: IMG6045.jpg


Attachment 3: IMG6044.jpg


Attachment 4: IMG6051.jpg


Attachment 5: IMG6049.jpg


Attachment 6: IMG6046.jpg


Attachment 7: IMG6048.jpg


Attachment 8: IMG6047.jpg


72

Thu Aug 4 11:26:55 2022 
Juan  General  General  Sat 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: IMG6153.jpg


74

Mon Aug 8 13:00:56 2022 
Juan  General  General  Sat 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

57

Sat Jul 2 09:22:39 2022 
Juan  General  General  Progress 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: IMG5220.jpg


75

Mon Aug 15 16:37:51 2022 
Juan  General  General  Update on Sat Amp and OSEMs 
Sat Amp
 Changes to sat amp 15.8 k ohm resistors instead of 16k The change has been made on Sat Amp  S1103733 & S1103732 ONLY Channel 4 and 2 have been changed on both boards.
OSEM
 I developed a test bed for our OSEM to measure force
I will attach images of the setup and some of the results from 3 different OSEMs.
Future Work
 For the current test bed, we are using a clear plastic bin although not ideal it manages to get the job done and works for now there could be a better solution for this,
 Next step for OSEM we want to use 40 m single pendulum to test OSEM and measure the transfer function. 
Attachment 1: IMG6458.jpg


Attachment 2: IMG6355.jpg


Attachment 3: IMG6459.jpg


Attachment 4: IMG6460.jpg


Attachment 5: OSEMdata.png


1

Thu May 21 11:51:44 2020 
Koji  General  General  Mariner Elog Test 
The first entry of the Mariner elog post 
16

Tue Jun 22 22:28:09 2021 
Koji  General  Design specs  Test Mass wedge design 
The ETM wedge of 0.5deg will allow us to separate the AR reflections. We will be OK with the ITM wedge of 0.5deg too. 0.36 deg for ITM is also OK, but not for the ETM.
 Attachment 1 shows the deflection of the 2128mn and 1418nm beams by the test mass wedge. Here, the wedge angle of 1deg was assumed as a reference. For the other wedge angle, simply multiply the new number (in deg) to the indicated values for the displacement and angle.
 Attachment 2 shows the simplified layout of the test masses for the calculation of the wedge angle. Here the ITM and ETM are supposed to be placed at the center of the invacuum tables. Considering the presence of the cryo baffles, we need to isolate the pickoff beam on the BS table. There we can place a black glass (or similar) beam dump to kill the AR reflection. For the ETM trans, the propagation length will be too short for invacuum dumping of the AR reflection. We will need to place a beam baffle on the transmon table.
 I've assumed the cavity parameter of L=38m and RoC(ETM)=57m (This yields the Rayleigh range zR=27m). The waist radii (i.e. beam radii at the ITM) for the 2128nm and 1418nm beams are 4.3mm and 3.5mm, while the beam radii at the ETM are 7.4mm and 6.0mm, respectively,
 Attachment 3: Our requirement is that the AR reflection of the ALS (1418nm) beam can be dumped without clipping the main beam.
If we assume the wedge angle of 0.5deg, the opening of the main and AR beams will be (2.462+4.462)*0.5 = 3.46 deg. Assuming the distance from the ETM to the inair trans baffle is 45" (=1.14m), the separation of the beams will become 69mm. The attached figure shows how big the separation is compared with the beam sizes. I declare that the separation is quite comfortable. As the main and AR beams are distributed on both sides of the optic (i.e. left and right), I suppose that the beams are not clipped by the optical window of the chamber. But this should be checked.
Note that the 6w size for the 2128nm beam is 44mm. Therefore, the first lens for the beam shrinkage needs to be 3" in dia, and even 3" 45deg BS/mirrors are to be used after some amount of beam shrinkage.
 Attachment 4 (Lower): If we assume the same ITM wedge angle of 0.5deg as the ETM, both the POX/POY and the AR beams will have a separation of ~100mm. This is about the maximum acceptable separation to place the POX/POY optics without taking too much space on the BS chamber.
 Attachment 4 (Upper): Just as a trial, the minimum ITM wedge angle of 0.36deg was checked, this gives us the PO beam ~3" separated from the main beam. This is still comfortable to deal with these multiple beams from the ITM/ 
Attachment 1: wedge.pdf


Attachment 2: Layout.pdf


Attachment 3: ETM.pdf


Attachment 4: ITM.pdf


20

Fri Aug 6 04:34:43 2021 
Koji  General  General  Theoretical Cooling Time Limit 
I was thinking about how fast we can cool the test mass. No matter how we improve the emissivity of the test mass and the cryostat, there is a theoretical limitation. I wanted to calculate it as a reference to know how good the cooling is in an experiment.
We have a Si test mass of 300K in a blackbody cryostat with a 0K shield. How fast can we cool the test mass?
Then assume the specific heat is linear as
The actual Cp follows a nonlinear function (cf Debye model), but this is not a too bad assumption down to ~100K.
Then the differential equation can be analytically solved:
,
where the characteristic time of t0 is
.
Here T_0 is the initial temperature, cp0 is the slope of the specific heat (Cp(T_0) = c_p0 T_0). epsilon is the emissivity of the test mass, sigma is Stefan Boltzmann constant, A is the radiating surface area, and m is the mass of the test mass.
Up to the characteristic time, the cooling is slow. Then the temperature falls sqrt(t) after that.
As the surfacevolume ratio m/A becomes bigger for a larger mass, in general, the cooling of the bigger mass requires more time.
For the QIL 4" mass, Mariner 150mm mass, and the Voyager 450mm mass, t0 is 3.8hr, 5.6hr, and 33.7hr respectively.
 If the emissivity is not 1, just the cooling time is expanded by that factor. (i.e. The emissivity of 0.5 takes x2 more time to cool)
 And if the shields are not cooled fast or have a finite temperature in the end, of course, the cooling will require more time.
 1.25 t0 and 8 t0 tell us how long it takes to reach 200K and 100K.
This is the fundamental limit for radiation cooling. Thus, we have to use conductive cooling if we want to accelerate the cooling further more than this curve. 
Attachment 1: cooling_curves.pdf


21

Tue Aug 17 17:48:57 2021 
Koji  General  Equipment  Crackle SW model 
As a kickoff of the mariner sus cryostat design, I made a tentative crackle chamber model in SW.
Stephen pointed out that the mass for each part is ~100kg and will likely be ~150kg with the flanges. We believe this is with in the capacity of the yellow Skyhook crane as long as we can find its wheeled base. 
Attachment 1: Screen_Shot_20210817_at_17.44.32.png


29

Fri Sep 24 11:02:41 2021 
Koji  General  General  Actuation Feedback Model and Noise 
We had a meeting with the code open in ZOOM. Here are some points we discussed:
 The code requires another file ground.m. It is attached here.
 The phase of the bode plots were not wrapped. This can be fixed by applying the "PhaseWrapping" options as
opts=bodeoptions('cstprefs');
opts.PhaseWrapping = 'on';
bode(A,opts)
 We evaluated the openloop transfer function of the system. For this purpose, we added the monitor point ('F') at the actuator and cut the loop there like:
sys = connect(P, S, W, ADC, Winv, A2, DWinv, Dinv, DAC, DW, D, R, C, {'xg' 'nADC', 'nDAC', 'nd', 'nth'}, 'xt', {'F','VDAC'});
OLTF=getLoopTransfer(sys(1),'F');
figure(2)
clf
bode(OLTF,opts);
 We played with the loopgain (Ga2). When Ga2 is a positive number, the loop was stable. We had to shift the low pass cutoff frequency from 10Hz to 12Hz to make the damping of the 2nd peak stable.

Attachment 1: ground.m

function [grnd] = ground(freq)
grnd = 1e7*(freq<1)+1e7*(1(freq<1))./(freq.^2+1e50);
end

45

Wed Nov 3 02:52:49 2021 
Koji  General  Suspension  Mariner 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 440 screws
To Do:
 EQ Stops / Cradle (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
 Fine alignment adjustment
 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
 Thread holes for baffles
 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 
Koji  General  Suspension  Mariner 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_20211104_at_12.38.46_AM.png


Attachment 2: Screen_Shot_20211104_at_12.39.53_AM.png


51

Thu May 5 19:56:25 2022 
Koji  General  Suspension  Mariner Suspension Cryo shield Install / Removal steps 
Does this work? Is this insane? 
Attachment 1: 40m_Mariner_Suspension0062.png


Attachment 2: 40m_Mariner_Suspension.mp4

54

Thu Jun 16 19:43:36 2022 
Koji  General  Suspension  Table for Mariner Suspension Cryo 
 B246/QIL Skyhook
Find the base of Skyhook. It should be in the storage room (B246). Stephen contacted Chub for lab access. Done
 Assemble Skyhook with the base and check the stability/safety/capacity/height/etc
 DOPO
Ask Paco to move the delicate instruments from the table. Done
 Bring Skyhook to DOPO. The chamber seems already vented.
 Find the way to place the cap on the floor safely and cleanly. => Stephen
 Open the cap and then remove the crackle interferometer. Wrap it with something and place it somewhere in the room. How? => Stephen
 Move the base to a dolly or something. Then put a cap on the base. => It'd be better to ask Caltech Transp for the chamber transportation.
 Do we have to temporarily remove the laser safety curtain?
 OMC Lab
We probably need to separate the optical table and the base. Ask Caltech Transp to check how the work should be done.
Do we have to temporarily move anything on the way?
 The table can be rolled out to the corridor and then rolled in to the CAML.
 CAML
 Remove the grey rack and push the desk to the East.
 Place the optical table.
 Place the rack close to the table.

55

Thu Jun 23 21:11:03 2022 
Koji  General  Suspension  Table for Mariner Suspension Cryo 
Table moving effort in the OMC lab: See https://nodus.ligo.caltech.edu:8081/OMC_Lab/412

120

Mon Jan 9 21:03:53 2023 
Koji  General  General  Heavy item transport  preparation 
1) Paco cleared the path in the DOPO lab. We'll need a flat dolly or wooden bars (covered with a mylar sheet) to place the lid on it while we will remove the suspension. The suspension will be placed next to the wall and wrapped with mylar sheets.
We'll need:
(from the 40m) a dooly, mylar sheets, spare slings
(from Downs) heavyduty inline scale
(from OMC lab) some tapes
2) The crane base is in CAML right now.
3) The yellow crane is in QIL right now. We'll dismount the top part and mount it on the base.

Steps
 Remove the lid. Place it on a clean safe platform.
 Remove the suspension, wrap it, and place it next the wall.
 Put the lid on.
 The chamber will be moved to CAML on Thu morning. 
Attachment 1: DOPO.jpg


Attachment 2: CAML.jpg


Attachment 3: QIL.jpg


121

Tue Jan 10 23:30:25 2023 
Koji  General  General  Heavy item transport  preparation 
[JC, Stephen, Paco, Gabriele, Aidan, Radhika, Koji]
We have successfully extracted the crackle suspension from the chamber at the DOPO lab. We ended up using the engine hoist brought from the cryo lab instead of the yellow Skyhook as Skyhook's arm was too short.
Attachment 1 shows how the hoist is inserted to the table and how the lid was lifted. The lid was placed on a cardboard box wrapped with a Mylar sheet. It could be slid on the floor.
Attachment 2 shows how the suspension was lifted and placed on a similar Mylarwrapped cardboard box. Upon the removal of the suspension, the cables were disconnected from the suspension. A few OSEM wires needed to be cut so that the suspension to be free.
Attachment 3 We are ready for the chamber transportation.

Attachment 1: PXL_20230110_214532535.jpg


Attachment 2: PXL_20230110_221731553.jpg


Attachment 3: PXL_20230110_222947057.MP.jpg


122

Thu Jan 12 11:38:26 2023 
Koji  General  General  How to move the large engine hoist through the narrow door 
See the attachments. 
Attachment 1: PXL_20230110_223009017.jpg


Attachment 2: PXL_20230110_223015483.MP.jpg


Attachment 3: PXL_20230110_223026446.MP.jpg


Attachment 4: PXL_20230110_223035480.MP.jpg


123

Thu Jan 12 11:54:08 2023 
Koji  General  General  Heavy item transport 
[JC, Koji]
Caltech transport came in this morning. They first went to the OMC lab and moved the 3ft x 4ft table out. They lifted the heavy objects only with human power.
Then the suspension chamber was moved with a hydraulic lifter. (Attachment 1)
The chamber bottom was sled on the table. We asked them to leave the chamber lid on the mylar + cardboard sheet (Attachment 2) so that we can carefully close the lid with a crane (Attachment 3).
JC and I continued to work on the chamber closure, but it wasn't so straightforward.
The nominally planned location of the table (seen in Attachment 3) has a low ceiling and was not a great place to open/close the lid. It is high enough just to close the lid but we can't do anything else.
We worked on the crane operation close to the lab entrance (Attachment 4). We found that the chamber needed to be offset from the center of the table because the legs of the hoist turned out to be too wide to get in between the table legs. This low ceiling had ~3" gap to the crane when the lid was closed (Attachment 5). Meaning, we can't put anything in the chamber if the lid gets stuck with the low ceiling.
Anyway, the chamber was closed and the table was rolled to the end of the lab (for storage) (Attachment 6).
BTW, the rolling of the table further destroyed the floor (Attachment 7)
So, how high the ceiling should be, so that we can put a tall suspension in the chamber? We probably need to use the northeast part of the lab where the ceiling is much higher. But the crane itself can be another limitation. It needs careful consideration. 
Attachment 1: PXL_20230112_170305972.MP.jpg


Attachment 2: PXL_20230112_171359486.jpg


Attachment 3: PXL_20230112_171431974.jpg


Attachment 4: PXL_20230112_174337730.jpg


Attachment 5: PXL_20230112_174621059.jpg


Attachment 6: PXL_20230112_174923601.MP.jpg


Attachment 7: PXL_20230112_174929015.jpg


124

Thu Jan 12 15:36:22 2023 
Koji  General  General  Crane configuration for the suspension test chamber 
I made a quick investigation of the crane configuration for the suspension test chamber.
Conclusions:
 The table and the suspension test chamber need to be placed in the northwest corner of CAML where the ceiling height is 105"
 The engine hoist needs to be connected to the chamber with a shackle or something similar to avoid the interference of the chamber lid and the tilted crane jib.
This shackle needs to raise the hanging point by ~3".
CAML has three types of ceilings.
1) Low ceiling area (west side) the clearance height 75.5"
2) Mid ceiling area (most of the lab area) 85.5". This is limited by the height of the FL light cover.
3) High ceiling area (northeast corner) 105". This is limited by the height of the FL light cover there.
Attachment P1
Nominal closed state: The chamber top height is about 68". Even in the low ceiling area, there is 7.5" space and the crane can remove the lid when the chamber is empty.
Attachment P2
Open chamber with suspension (direct connection): If the lid and the hook are directly connected, the corner of the chamber is going to be very close to the jib arm when the chamber is fully opened with ~1" clearance. This is not a safe condition, considering that the chamber can oscillate due to the lateral motion associated with raising the jib arm.
Attachment P3
Open chamber with suspension (connection via a 3" shackle): When the lid and the hook are connected via a 3" shackle, we'll observe a safe amount of clearance between the chamber and the jib arm. And the crane height is still 96" which is lower than the ceiling height of the high ceiling area of the lab. 
Attachment 1: crane_config.pdf


12

Tue Apr 27 12:28:43 2021 
Nina Vaidya & Shruti Maliakal  General  Design specs  Arm Cavity Design 2021 
Rana’s code: R_c = 57.3
>New code with optimization: sweeping through a range of R_c, using a cost function that puts value on peak height, distance of the peaks from the zero order, and mode number. This cost function can be edited further to adapt to more aims (Slides attached). Currently (code attached) gives > R_c = 58.4 with very slightly different peaks and energy distribution in the modes
1) Range of R_c is 57 to 60, for some reason lower values of R_c in the range are giving error > debug this
2) Find how sensitive the model is for 1% change in R_c value
3) Make sure the side bands are not resonating 
Attachment 1: Arm_Cavity_Design_04232021.pptx

Attachment 2: Arm_HOM_optimization.ipynb

{
"cells": [
{
"cell_type": "markdown",
"metadata": {},
"source": [
"# Mariner: Higher Order Mode Analysis of Arm Cavities for PhaseI trial\n",
"\n",
"This notebook contains a study of modematching for optical FabryPerot cavities using Finesse\n",
"\n",
... 943 more lines ...

14

Fri May 7 17:50:31 2021 
Nina Vaidya & Shruti Maliakal  General  Design specs  Arm Cavity Design 2021 update 
Here are the final slides with all the results on the Arm Cavity Design, please review.
For RoC of 56.2 +/ 1% things are working well. Tolerance of 0.5% will be better however, 1% is still working; as long as we do not want any peaks ~50kHz away.
For length, 38+0.5% = 38.19 (with RoC 56.2) not ideal, peak is close (48.8kHz) but maybe ok? @Rana thoughts? and 380.5% = 37.81 (with RoC 56.2) works well.
To summarise the design:
RoC = 56.2 +/ 1%
L = 38 +/ 0.5% 
Attachment 1: Arm_Cavity_Design_05072021_with_tolerances.pptx

Attachment 2: HOMhelper.py

def add_cavmodel(kat, T=0.001, Loss=5e6, theta=60, L_rt = 2*12.240, R_c = 20, f1 = 11e6, gamma1 = 0, f2 = 55e6, gamma2 = 0):
'''
T: Transmission of mirror (ITM)
Loss: Loss of mirror ETM
L_rt: Round trip length of cavity
R_c: Radius of curvature of ETM
'''
... 98 more lines ...

Attachment 3: Arm_HOManalysis.ipynb

{
"cells": [
{
"cell_type": "code",
"execution_count": 376,
"metadata": {},
"outputs": [],
"source": [
"from pykat import finesse\n",
"from pykat.commands import *\n",
... 825 more lines ...

Attachment 4: HOMplot.py

import numpy as np
import scipy.constants as scc
import matplotlib as mpl, matplotlib.pyplot as plt
from matplotlib import cm
plt.rcParams.update({'text.usetex': False,
'lines.linewidth': 2,
'font.family': 'serif',
'font.serif': 'Georgia',
'font.size': 22,
... 132 more lines ...

4

Thu Mar 4 17:04:52 2021 
Paco  General  Design specs  Silicon 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 Silicatantala 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 "insanelooking" solutions). The top picks in Attachment 1 may be a good starting point for a manufacturer. In order of appearance, they are:
 ETM_210218_1632
 ETM_210222_1621
 ETM_210302_1210
 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:
 ITM_210303_1806
 ITM_210204_1547
 ITM_210304_1714

Attachment 1: ETM_coating_candidates.pdf


Attachment 2: ITM_coating_candidates.pdf


6

Wed Mar 17 19:51:42 2021 
Paco  General  Design specs  Silicon 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;
 Updated wavelengths to be 2128.2 nm and 1418.8 nm (PSL and AUX resp.)
 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)
 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.
 Included a third wavelength as transOPLV (for the OPLEV laser) which tries to get R ~ 99 % at 632 nm
 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.
 Adapted the MCMC modules (doMC, and cornerPlot) to check the covariance between the transmissivities at 2128 and 1418 for a given design.
 Reintroduced significant weights for TO noise and Brownian noise cost functions (from 1e11 to 1e1) 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


8

Wed Mar 24 17:36:46 2021 
Paco  General  Design specs  Least 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 mbilayers 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


9

Wed Mar 24 17:42:50 2021 
Paco  General  Design specs  Silicon 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?


10

Fri Apr 2 19:59:53 2021 
Paco  General  Design specs  Differential evolution strategies 
Differential evolution strategies 'benchmarking' for thin film optimization
Since I have been running the ETM/ITM coatings optimization many times, I decided to "benchmark" (really just visualize) the optimizer trajectories under different strategies offered by the scipy.optimize implementation of differential evolution. This was done by adding a callback function to keep track the convergence=val at every iteration. From the scipy.optimize.differential_evolution docs, this "val represents the fractional value of the population convergence".
Attachment 1 shows a modest collection of ~16 convergence trajectories for ETM and ITM as a function of the iteration number (limited by maxiter=2000 ) with the same targets, weights, number of walkers (=25), and other optimization parameters. The vertical axis plots the inverse val (so tending to small numbers represent convergence).
tl;dr: Put simply, the strategies using "binary" crossover schemes work better (i.e. faster) than "exponential" ones. Will keep choosing "best1bin" for this problem. 
Attachment 1: diffevostrategies.pdf


15

Fri Jun 4 11:09:27 2021 
Paco  General  Design specs  HR coating tolerance analysis 
The HR coating specifications are:
ETM Transmission specs
2128.2 nm 
5.0 ppm 2 ppm 
1418.8 nm 
50.0 ppm 2 ppm 
ITM Transmission specs
2128.2 nm 
2000.0 ppm 200 ppm 
1418.8 nm 
50.0 ppm 2 ppm 
Analysis
 Main constraint: Relative arm finesses @ 2128.2 nm should not differ by > 1%.
 Secondary constraint: Relative arm finesses @ 1418.8 nm may differ, but the ETM and ITM pair should ensure critically coupled cavity to benefit ALS calibration PD shot noise.
Just took the finesse of a single arm:
and propagated transmissivities as uncorrelated variables to estimate the maximum relative finesse. Different tolerance combinations give the same finesse tolerance, so multiple solutions are possible. I simply chose to distribute the relative tolerance in T for the test masses homogeneously to simultaneously maximize the individual tolerances and minimize the joint tolerance.
A code snippet with the numerical analysis may be found here.
Tue Jun 8 11:52:44 2021 Update
The arm cavity finesse at 2128 nm will be mostly limited by the T = 2000 ppm of the ITM, so the finesse changes mostly due to this specification. Assuming that the vendor will be able to do the two ETM optics in one run (x and y), we really don't care so much about the mean value achieved in this run as much as the relative one. Therefore, the 200 ppm tolerance (10% level) is allowed at the absolute level, but a 20 ppm tolerance (1% level) is still preferred at the relative level; is this achievable?. Furthermore, for the AUX wavelength, we mostly care about achieving critical coupling but there is no requirement between the arms. Here a 20 ppm tolerance at the absolute level should be ok, but a 2 ppm tolerance between runs is highly desirable (although it seems crazier); is this achievable? 
19

Tue Jul 27 11:38:25 2021 
Paco  General  Design specs  DOPO single pass PDC efficiency 
Here is a set of curves describing the singlepass downconversion efficiency in the 20 mm long PPKTP crystals for the DOPO. I used the "nondepleted pump approximation" and assumed a planewave (although the intensity matches the peak intensity from a gaussian beam). Note that these assumptions will in general tend to overestimate the conversion efficiency.
The parameters use an effective nonlinear coefficient "d_eff" of 4.5 pm/V, and assume we have reached the perfect (quasi) phase matching condition where delta_k = 0 (e.g. we are at the correct crystal operating temperature). The wavelengths are 1064.1 nm for the pump, and 2128.2 nm for degenerate signal and idler. The conversion efficiency here is for the signal photon (which is indistinguishable from the idler, so am I off by a factor of 2?)...
Attachment 1 shows the single pass conversion efficiency "eta" as a function of the pump power. This is done for a set of 5 minimum waists, but the current DOPO waist is ~ 35 um, right in the middle of the explored range. What we see from this overestimates is an almost linearinpump power increase of order a few %. I have included vertical lines denoting the damage threshold points, assuming 500 kW / cm ^2 for 1064.1 nm (similar to our freespace EOMs). As the waist increases, the conversion efficiency tends to increase more slowly with power, but enables a higher damage threshold, as expected.
At any rate, the singlepass downconversion efficiency is (over)estimated to be < 5 % for our current DOPO waist right before the damage threshold of ~ 10 Watts, so I don't think we will be able to use the amplified pump (~ 2040 W) unless we modify the cavity design to allow for larger waist modes.
The important figure (after today's group meeting) would be a single pass downconversion efficiency of ~ 0.5 % / Watt of pump power at our current waist of 35 um (i.e. the slope of the curves below) 
Attachment 1: singlepass_eff_overest.pdf


24

Thu Sep 9 11:25:30 2021 
Paco  General  Design specs  Rerun HR coatings with n,k dispersion 
[Paco]
I've rerun 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 lowtemperature estimates to roomtemperature measured (?) dispersions are able to push the HR transmission up by a few (23) 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 
Paco  General  Design specs  Rerun HR coatings with n,k dispersion 
[Paco]
Alright, I've done a reoptimization 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


28

Sun Sep 19 18:52:58 2021 
Paco  General  Design specs  HR coating emissivity 
[Paco, Nina]
We have been working on an estimate of the wavelength dependent emissivity for the mariner test mass HR coatings. Here is a brief summary.
We first tried extending the thin film optimization code to include extinction coefficient (so using the complex index of refraction rather than the real part only). We used cubic interpolations of the silica and tantala thin film dispersions found here for wavelengths in the 1 to 100 um range. This allowed us to recompute the field amplitude reflectivity and transmissivity over a broader range. Then, we used the imaginary part of the index of refraction and the thin film thicknesses to estimate the absorbed fraction of power from the interface. The power loss for a given layer is exponential in the product of the thickness and the extinction coefficient (see eq 2.6.16 here) . Then, the total absorption is the product of all the individual layer losses times the transmitted field at the interface. This is true when energy conservation distributes power among absorption (=emission), reflection, and transmission:
The resulting emissivity estimate using this reasoning is plotted as an example in Attachment #1 for the ETM design from April. Two things to note from this; (1) the emissivity is vanishignly small around 1419 and 2128 nm, as most of the power is reflected which kind of makes sense, and (2) the emissivity doesn't quite follow the major absorption features in the thin film interpolated data at lower wavelengths (see Attachment #2), which is dominated by Tantala... which is not naively expected?
Maybe not the best proxy for emissivity? Code used to generate this estimates is hosted here. 
Attachment 1: ETM_210409_120913_emissivity.pdf


Attachment 2: interpolated_TF_k.pdf


33

Fri Oct 1 11:52:06 2021 
Paco  General  Design specs  HR coating emissivity 
[Paco, Nina, Aidan]
Updated the stack emissivity code to use the Kitamura paper fused silica dispersion which has a prominent 20 um absorption peak which wasn't there before... (data was up to 15 um, and extrapolated smoothly beyond). The updated HR stack emissivities are in Attachments #1  #2. A weird feature I don't quite understand is the discontinous jump at ~ 59 um ... 
Attachment 1: ETM_210409_120913_emissivity.pdf


Attachment 2: interpolated_n_k.pdf


34

Fri Oct 1 12:01:24 2021 
Paco  General  Design specs  TM 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:
 * 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 # 13 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


36

Fri Oct 1 14:11:23 2021 
Paco  General  Design specs  TM Barrel coating emissivity 
Agree with this. Quickly running tmm on the same "stacks" gave the Attachment #13. (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


47

Fri Nov 5 11:51:50 2021 
Paco  General  Design specs  Estimate of inair absorption near 2.05 um 
[Paco]
I used the HITRAN database to download the set of rovibrational absorption lines of CO2 (carbon dioxide) near 2.05 um. The lines are plotted for reference vs wavenumber in inverse cm in Attachment #1.
Then, in Attachment #2, I estimate the broadened spectrum around 2.05 um and compare it against one produced by an online tool using the 2004 HITRAN catalog.
For the broadened spectrum, I assumed 1 atm pressure, 296 K temperature (standard conditions) and a nominal CO2 density of 1.96 kg/m^3 under this conditions. Then, the line profile was Lorentzian with a HWHM width determined by self and air broadening coefficients also from HITRAN. The difference between 2050 nm and 2040 nm absorption is approximately 2 orders of magnitude; so 2040 nm would be better suited to avoid inair absorption. Nevertheless, the estimate implies an absorption coefficient at 2050 nm of ~ 20 ppm / m, with a nearby absorption line peaking at ~ 100 ppm / m.
For the PMC, (length = 50 cm), the roundtrip loss contribution by inair absorption at 2050 nm would amount to ~ 40 ppm. BUT, this is nevery going to happen unless we pump out everything and pump in 1 atm of pure CO2. So ignore this part.
Tue Nov 9 08:23:56 2021 UPDATE
Taking a partial pressure of 0.05 % (~ 500 ppm concentration in air), the broadening and total absorption decrease linearly with respect to the estimate above. Attachment #3 shows the new estimate.
For the PMC, (length = 50 cm), the roundtrip loss contribution by inair absorption at 2050 nm would amount to ~ 1 ppm. 
Attachment 1: HITRAN_line_strenghts.pdf


Attachment 2: broadened_spectrum.pdf


Attachment 3: PP_broadened_spectrum.pdf


48

Tue Nov 16 11:47:54 2021 
Paco  General  Design specs  Estimate of inair absorption near 2.05 um 
[Paco]
There was an error in the last plot of the previous log. This was correctly pointed out by rana's pointing out that the broadening from air should be independent of the CO2 concentration, so nominally both curves should coincide with each other. Nevertheless, this doesn't affect the earlier conclusions >
The PMC loss by background, pressure broadened absorption lines at 2049.9 nm by CO2 is < 1 ppm.
The results posted here are reflected in the latest notebook commit here. 
Attachment 1: PP_broadened_spectrum.pdf


67

Mon Jul 18 18:34:29 2022 
Paco  General  Design specs  HR coating update 
I've been running the HR coating optimization for mariner TMs. Relative to the specifications found here we now are aiming for
 ITM HR coating of 2000 ppm @ 2050.15 nm, and 1000 ppm @ 1550 nm
 ETM HR coating of 25 ppm @ 2050.15 nm, and 1000 ppm @ 1550 nm.
Both the PSL and AUX cavity finesses range the few couple of thousands, and the goal is not to optimize the coating stack for noise, but more importantly for the transmission values and tolerances. This way we ensure the average finesse and differential finesse requirements are met. Anyways, Attachment #12 shows the transmission plots for the optimized coating stacks (so far). Attachments #34 show the dielectric stacks. The code still lives in this repository.
I'm on the process of assessing the tolerance of this design stacks against perturbations in the layer thicknesses; to be posted in a followup elog. 
Attachment 1: ETM_R.pdf


Attachment 2: ITM_R.pdf


Attachment 3: ETM_Layers.pdf


Attachment 4: ITM_Layers.pdf


68

Fri Jul 22 13:36:55 2022 
Paco  General  Design specs  HR coating update 
Here are some corner plots to analyze the sensitivity of the designs in the previous elog to a 1% gaussian distributed perturbation using MCMC.
Attachment #1 shows the ETM corner plot
Attachment #2 shows the ITM corner plot.
I let the indices of both high and low index materials vary, as well as the physical thicknesses and project their covariances to the transmission for PSL and AUX wavelengths.
The result shows that for our designs it is better to undershoot in the optimization stage rather than meet the exact number. Nevertheless, 1% level perturbations in the optical thickness of the stack result in 30% deviations in our target transmission specifications. It would be nice to have a better constraint on how much each parameter is actually varying by, e.g. I don't believe we can't fix the index of refraction to better than 1%., but exactly what its value is I don't know, and what are the layer deposition tolerances? These numbers will make our perturbation analysis more precise. 
Attachment 1: ETM_corner.pdf


Attachment 2: ITM_corner.pdf


76

Tue Aug 16 09:58:23 2022 
Paco  General  Design specs  HR coating update 
A couple of coating stacks with better tolerance (transmission + 10%). Attachments #12 show the spectral reflectivities for ETM/ITM respectively, while Attachments #34 show the corner plots. I think the tolerances are inflated by the fact that all the stack indices and thicknesses are varying, while in reality these two effects are degenerate because what matters is the optical thickness. I will try to reflect this in the MCMC code next. Finally, attachments # 56 are the hdf5 files with the optimization results. 
Attachment 1: ETM_R_220816_094640..pdf


Attachment 2: ITM_R_220816_095441..pdf


Attachment 3: ETM_corner.pdf


Attachment 4: ITM_corner.pdf


Attachment 5: ETM_Layers_220816_094640.hdf5

Attachment 6: ITM_Layers_220816_095441.hdf5

78

Tue Aug 23 17:10:50 2022 
Paco  General  Design specs  New 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 12 below. 
Attachment 1: ITM_corner.pdf


Attachment 2: ETM_corner.pdf

