Update on the FROSTI reflector design

slides

[Joshua, Mary, Ma, Abhi]

On Wednesday (7/15), the particle count measurement was sufficient, so the FROSTI was transferred into the cleanroom. We unmounted it from the plastic base, and secured it to the optical table. We also transferred the neccessary parts for the HBT setup and began assembly. The breadboard was built first (except for the lenses/beamsplitter) and mounted the the optical posts which will hold it. We placed the beamsplitter as close as possible to FROSTI without touching, and secured the feet. It is ready for the lenses/beamsplitter to be cleaned and placed in their mounts. Then we will align the setup for maximum power on the transmissive arm.

- the non-uniformity brought by annealing for ETM14 and 11 seems to be higher than expected, this meeting focused on discussing about annealing data for ETM014 and 11 : https://dcc-lho.ligo.org/LIGO-T2600213

    -we will receive more data for these, since there are some residual power left in the data/plots shown in the meeting because of the reference sphere, and the exact reference sphere radius is unclear

- reviewed the uniformity plot for HR ETM with TiGe coating again: https://dcc-lho.ligo.org/LIGO-T2600277

- not a lot of updates for ring heater: 40W delivered. Currently lock with 1.5W per segment on ETMy at LHO

- slides for HOM study for 250mW biased profile:

https://docs.google.com/presentation/d/1BWh_skxkCXBu_e_QkXkUs9CdvFIryu7H_jfpCgOenNg/edit?usp=sharing
https://docs.google.com/presentation/d/174XVLLpNpNgnL0uV-dSp6MO5pmZ9Yvnouf8V0LA2zE8/edit?usp=sharing

However, we did not focus on any surface profile related topics in the meeting so it was not presented

HBT setup was aligned for maximum power on the transmissive arm, then the beamsplitter was tilted to equalize the power in each arm. Then, we set the board at
Total power: 0.156 V
Power on each photodetector: 0.078 V
We left the FROSTI on and will collect data overnight. If we need more power, we can cut the breadboard notch further.

[Joshua, Mary]

Changed the sample rate of Cymac ADC channels V3 and VREF6 to 65 kHz for long-time recording. (65536 to be exact)

Here is a how-to for future reference:

• On Cymac, open Matlab and go to the medm model at '/opt/rtcds/usercode/models/c1msc.mdl'
• On the left hand side, there is a DAQ Channel block with text. Any Channel on this list will be recorded to the .gwf frame files as raw data. See alog 592 , and the attached picture.
• I have added all of our current channels to this list, with full sample rate to be recorded, but have commented out the ones that are not in use currently. For future, one can just uncomment the ones that they need to add. 
• Make sure that you save the model (by ctrl+S) after making changes
• Complile and install the model following this page.
• Restart the rts services. It's easiest to just restart all via: `sudo systemctl restart rts*`

I have resurrected the automatic backup script for the Cymac files as well. Will start running it in a few days. 

- using the change in surface from annealing, Hiro did some study on HOM scattering/losses from just this surface (shown in the email attachmnent O5testmass.pdf. We together went over these results again.

    - ETM11 annealing data to be used: https://dcc.ligo.org/T2600214
- more annealing data: https://docs.google.com/spreadsheets/d/1E138nNZk5b1yPm0g5jmwv_Z9FD9ArQtnlAk1d_1Ce1U/edit?usp=sharing

- Mostly discussed what to do about this annealing surface change when we are polishing the mirror: The idea now is to polish around it (the polish will include the negative of those surface deformation), but it's better to express it in an analytical form to the manufactuer. We try to explore if it is feasible to represent this surface introduced by annealing as Zernike coefficients

- New ITM meausrement shown as attachment below

- Kevin and Evan will take this surface after annealing as part of their error analysis for their 250mW biased surface profile in the furture, meanwhile I tried to see how will the HOM and PRG conditions change if we don't do anything about this surface, using same analysis we did before:

-
https://docs.google.com/presentation/d/1nkyOmivyaPKkvbgf3TPBjgV2YcgRum7N1EvapgcIMaA/edit?slide=id.p#slide=id.p

This is a measurement done to determine which heating elements output the most power. FROSTI was supplied 33V, and a photodetector was held to the center of each heating element directly at the aperture.

Element #1 (top), RTD0 - 0.33 V
Element #2 (bottom right), RTD1 - 0.21 V
Element #3 (top left), RTD2 - 0.15 V
Element #4 (bottom), RTD3 - 0.33 V
Element #5 (bottom left), RTD4 - 0.31 V
Element #6 (right), RTD5 - 0.25 V
Element #7 (top right), RTD6 - 0.00 V (shorted)
Element #8 (left), RTD7 - 0.31

We have tested the heater to find emissivity, mounted the heater system to the optical table, and have taken irradiance maps of the heater projected onto the screen.

The heater's emissivity was determined by using a thermocouple in conjunction with the FLIR's temperature calibration. To attach the thermocouple to the heater initially, I used Kapton tape and ran both the wires of the heater and the thermocouple through the heater bridge. This allowed for the heater to rest on an optical post and be observed without anyone directly holding it, but there were some measurement issues. The thermocouple had a very wide range of temperatures it was reading, which may have been due to intermittent contact or a short between the two legs of the thermocouple. To solve this and make the temperature measurements more stable, we pried apart the two ends of the thermocouple (to ensure there was no short) and put tape on either side, leaving the end connection bare. This was then taped to the heater, and the thermocouple was much more stable. We also used a K-type thermocouple that has an adhesive tape on it already, which assisted with the intermittent contact as well. With the thermocouple measuring the temperature of the heater, we could point the FLIR directly at the heater and calibrate the emissivity until the FLIR and the thermocouple agreed. Cassidy's emissivity calculator was also used, as I could input a temperature and observe what the emissivity of an area was based on that temperature. We found the emissivity of the heater to be 0.57.

As a note, when observing the heater with the FLIR, it appeared that there was a hot spot in the center, where the Kapton tape sat. Because the Kapton has a different emissivity than the 304 stainless steel of the heater, the FLIR will read it as having a different temperature than it actually does. When using the FLIR in the future, be sure to ascertain whether there is a temperature difference somewhere or if there may be different emissivities.

Additionally, the first heater that I used was taken to a very high temperature and oxidized. The emissivity of this oxidized heater is not known, but could be good information for knowing how oxidation affects these heaters specifically.

To mount the heater system in front of the screen, I used 1/2'' optical posts and the mount I designed using COMSOL's CAD program. The heater was originally 2.5 inches away from the screen, and has since been moved back by an additional two inches so that we could observe the heater side of the screen with the FLIR. We wanted to see what temperature the heater side of the screen was when irradiated by the heater, and how that compared to the camera side of the screen. When the heater ran at 1.12 W of input power, the heater side of the screen had a max temperature of around 29.7 C, and the camera side of the screen read at about 29.5 C. This means that there is very little thermal loss between the two sides of the screen, and any insulation that the screen's adhesive may have is largely negligible. Additionally, the camera was placed at an angle and undetermined distance for these tests, confirming that the temperature measurements compensate well/don’t depend on changes in angle or distance between the camera and the screen. However, there was spots on the back of the screen that the camera was measuring as hot spots where there shouldn’t have been any. I have included an example below. It would be useful to run a test where the camera is directly on the back of the screen without the heater to characterize the screen and see if the hot spots are physically present on the screen or if this is an artifice of the camera because of something like angle of viewing.

Taking irradiance maps of the screen was straightforward. After checking that the emissivity of the screen is 0.99 by viewing it at room temperature, we monitored the max temperature while slowing increasing the wattage the heater was running at. There is not a large change until the heater is at around 95 C, at which point the screen began to rise in temperature from 27 C to 28 C. We took measurements of this while the heater was 2.5 and 4.5 inches away from the screen. The irradiance map has a very symmetrical and circular shape, but does not have the ring pattern that we expected. There may be a few reasons for this: there could be some conduction between the two sides of the screen that is causing the pattern to spread further, the heater setup may not be as ideal as it was modeled to be, or there could be a different, unknown issue.

TO DO:

- It would be useful to run a test of the camera in multiple different positions to ensure our conclusion that the camera’s measurements don’t depend on angle or distance (or that these factors are well accounted for in the current temperature calculations) is correct.

- Measure the back of the screen straight on to identify bright spots and possible reasons as to their appearance.

- Recalibrate camera to ensure it is still correct after testing in multiple positions.

- Take another irradiance map of the screen at a higher input power, as well as moving the heater close/further away to try and replicate the COMSOL irradiance maps. It would be useful to also redo the COMSOL modeling at lower powers and variable distances.

Pictures included of full table setup, the heater mount, the heater with Kapton tape attaching the thermocouple as well as FLIR's measured irradiance map.

Following the problem with contamination particles observed in the the Leybold thermovac TTR 91, we have taken the following step to clean the gauge:

1. Wipe with IPA-wetted Vectra Alpha: Cover the tip of a ziptide with Vectra Alpha wipe corner that has been wetted with IPA, push the wipe around and remove visible particulates
2. Fill the gauge flange with IPA: (following Jon's recommendation to use Lesker's procedure for cleaning their Pirani gauge), flip the gauge up such that the CF flange points upward, fill the flange with IPA all the way up. Use the tip of a SSTL tweezer to agitate the IPA. Let it sits for 20 minutes, agitate every 5 minutes. After 20 minutes, pour the IPA out then spray with dry pure nitrogen
3. Passive drying : Let the gauge sit inside the flowbench for 3 hours (3:30 pm to 6:30 pm)to ensure all IPA has evaporated
4. Baking : Leave the gauge in oven at 50 degree C for 48 hours (maximum allowed temperature is 65 deg C, we use 50 deg C to ensure we are well below this limit). Baking started at 7pm, should finish on Sunday 7pm and ready for assembling to vacuum chamber on Monday morning

Pressure Measured Before Removing Gauge 2.31 E-7 Torr.

Went in and turned on the heating tape in increments of 30 degC until 120 degC was reached. I will let it equilibrate over night and then asses whether or not the chamber can be raised to 150 degC without having the flange to the turbo pump reach over 120 degC as it is not recommended for that flange to be any hotter.

If it can safely be raised to 150 degC, then only 2 days of baking is necessary. If 120 degC is the bake temperature, a week will be needed.

Below is the procedure we will follow to assemble the FROSTI prototype.

1. Install SS guide rods and bottom Macor spacers in bottom reflector
2. Install AlN elements on top of bottom Macor spacers
3. Install upper Macor spacers on top of AlN elements
4. Feed unterminated power and RTD leads through slots in upper reflector
5. Install upper reflector, using guide rods to slowly lower into position
6. Install vented SS bolts for reflectors; Macor bolts for heater elements
7. Remove SS guide rods
8. Bundle power and sensing cable with PEEK cable ties and SS cable mounts
9. Terminate power and sensing cable bundles with PEEK DB25M connectors

[Luke, Luis, Michael]

cleaning cleanroom and particle count

• 8:30 am: started particle count
  • zone 3:
    • 0.3 u: 1195
    • 0.5 u: 177
    • 1.0 u: 132
• zone 4:
  • 0.3 u: 619
  • 0.5 u: 0
  • 1.0 u: 0
• 9:00 am: began surface check and wipedown, including softwalls
• 9:35 am: started vacuuming the floor
• 9:43 am: finished vacuuming the floor
• 9:45 am: started mopping the floor
• 9:55 am: finished mopping the floor
• 9:56 am: started cleaning the buckets
• 10:00 am: started mopping with IPA wipes
• 10:05 am: finished mopping with IPA wipes
• 10:20m: started particle count
  • zone 3:
    • 0.3 u: 2213
    • 0.5 u: 398
    • 1.0 u: 0
• zone 4:
  • 0.3 u: 1150
  • 0.5 u: 177
  • 1.0 u: 44

[Luke, Luis]

Update of current state of vacuum chamber

Current temp: 24°C

Current pressure: Main 1.77e-8, RGA 5.3e-9 [torr] (Gate valve open)

Summary of recent work-->

To try and reduce the leak in the turbo pump by reducing cross-connection, we replaced the copper gasket. This made no improvement to the leaks.

Initially: 1.9e-9 --->

Left side: 1.33e-9, Right side: 3.37e-9 (Gate valve open)

This is still a significant leak. We have tried to tighten the bolts further, but they are as tight as reasonably possible. 

Things of note: While examining the knife edges, we found some very slight imperfections on the reducing cross's flange as seen in 474. This could be the source of our leak. We have replaced this gasket 1-2 times already and consistently have a slight leak. This imperfection is on the right side of the flange, which would be consistent with the measurements above. 

Unless we want to use the liquid sealant or replace the gasket with an annealed gasket, we could try baking the system again, as this allowed us to reach UHV in the main volume before. It also allowed us to pass the RGA scan, which we are currently failing. (see attached)

[Luke, Tyler, Cynthia, Shane, Michael]

Summary of Cleaning Activities:

We began cleaning Room 1119 at 2:00 PM.

At 2:30 PM, we moved to Room 1129 and continued cleaning.

Cleaning tasks included wiping down dust-collecting surfaces and vacuuming the floors.

Once the labs were clean, we proceeded to the cleanroom. 

• Wiping down surfaces and soft walls
• Vacuuming, mopping the floor, and finishing with IPA wipes

Particle Count Measurements:

• Pre-cleaning (2:30 PM):
  • Zone 3:
    • 0.3 µm: 973
    • 0.5 µm: 354
    • 1.0 µm: 132
  • Zone 4:
    • 0.3 µm: 486
    • 0.5 µm: 177
    • 1.0 µm: 0
• Post-cleaning (4:10 PM):
  • Zone 3:
    • 0.3 µm: 619
    • 0.5 µm: 132
    • 1.0 µm: 0
  • Zone 4:
    • 0.3 µm: 397
    • 0.5 µm: 0
    • 1.0 µm: 0

[Luke, Liu]

Over the winter break I have been working on this desmos toy model of the Frosti. There are still a few rough spots but I belive that it is a good visual representation of a 2D slice of the frosti. 

[Luke, Cece, Luis]

Particle Count Measurements:

• Pre-cleaning (12:15 PM):
  • Zone 3:
    • 0.3 µm: 1325
    • 0.5 µm: 265
    • 1.0 µm: 0
  • Zone 4:
    • 0.3 µm: 618
    • 0.5 µm: 132
    • 1.0 µm: 44

• Started Cleaning (3:20 pm)
• Finished Cleaning (4:20 pm)

• Post-cleaning (4:35 PM):
  • Zone 3:
    • 0.3 µm: 1106
    • 0.5 µm: 221
    • 1.0 µm: 0
  • Zone 4:
    • 0.3 µm: 530
    • 0.5 µm: 44
    • 1.0 µm: 0

[Luke, Luis]

The vacuum chamber is currently baking. 

We stepped up to 120°C by increments of 30°C starting at 60°C. We took about an hour break at 90°C to let the temperatures equilibrate.  

Current state as of 12:20:

The gate valve is open, the calibrated Argon leak is open, and the filament of the RGA is on.

The temperatures are as follows:

PID right barrel upper: 113°C,  RGA volume: 120°C

PID left barrel lower: 121°C, Lid: 114°C

The lower temperatures should climb as the whole system heats up. 

[Luke, Mary, Luis]

Particle Count Measurements:

• Pre-cleaning (8:40 am):
  • Zone 3:
    • 0.3 µm: 441
    • 0.5 µm: 44
    • 1.0 µm: 0
  • Zone 4:
    • 0.3 µm: 353
    • 0.5 µm: 176
    • 1.0 µm: 44

• Started Cleaning (3:16 pm)
• Finished Cleaning (4:10 pm)

• Post-cleaning (4:15 pm):
  • Zone 3:
    • 0.3 µm: 574
    • 0.5 µm: 265
    • 1.0 µm: 132
  • Zone 4:
    • 0.3 µm: 177
    • 0.5 µm: 44
    • 1.0 µm: 0

[Luke, Mohak, Luis]

We were also able to remove the residue that has built up on the soft walls by donning a skinny bunny suit and with two wipes rubbing both sides of the soft walls at the same time. The wipes would get gummy very quickly and need to be replaced frequently.

Particle Count Measurements:

• Pre-cleaning (1:20 pm):
  • Zone 3:
    • 0.3 µm: 3577
    • 0.5 µm: 1369
    • 1.0 µm: 485
  • Zone 4:
    • 0.3 µm: 1062
    • 0.5 µm: 442
    • 1.0 µm: 177

• Started Cleaning (3:00 pm)
• Finished Cleaning (4:00 pm)

• Post-cleaning (4:22 pm):
  • Zone 3:
    • 0.3 µm: 3577
    • 0.5 µm: 618
    • 1.0 µm: 132
  • Zone 4:
    • 0.3 µm: 2031
    • 0.5 µm: 397
    • 1.0 µm: 132

[Luke, Luis]

We’ve been looking into methods for evaluating the performance of the HEPA filters in the clean room. Measuring flow rate appears to be a promising approach, since the filter manual specifies a recommended minimum of 70 ft/min.

At the moment, we don’t have a flow rate measurement device on hand. We're currently looking into two options:

• A standard vane-style anemometer, which is more affordable but may lack sensitivity near the minimum required flow rate.
• A hot-wire anemometer, which offers better resolution and accuracy at lower speeds, though it's more expensive.

In the next few days, either Luis or I will contact Terra Universal to see if they have any measurement solutions that would integrate well with our clean room setup, or if they can recommend best practices for verifying HEPA performance.

• Looked at the mode mismatch using cavity_mismatch_table().
• Compared these finesse_ligo factory model mismatch values with those of the aLIGO katscript model.
• The latter does not have the cavity_mismatch_table(), looked at both models' mismatch values using cavity_mismatch().
• Ascertained that there is less mode mismatch in the katscript model (~10^-2) as compared to the factory model (~10^-6).
• Mismatch values are starkly different, not just for (PRC, XARM) but also for others like (OMC, XARM).

• Analysed the locking process for factory model and katscript model to find minor differences in the order.
• Tried applying the katscript locking function to the factory model and still seem to get the same results. (to recheck)

Today we started vacuum chamber assembly work

• 10:16 am: Particle count measurement of clean room
• 10:34 am: Particle counting finished: meets ISO 5 standard
  1. Zone 3 :
     • 0.3 u: 3159
     • 0.5 u: 789
     • 1.0 u: 83
  2. Zone 4 :
     • 0.3 u: 498
     • 0.5 u: 41
     • 1.0 u: 0
• 10:45 am: Assemble vacuum feedthrough
• 11:08 am: Finish assembling feedthrough
• 11:14 am: Assemble inverted magnetron pirani gauge
• 11:29 am: Finish assembling magnetron gauge
• 11:31 am: Assemble calibrated Ar Leak
• 11:47 am: Finish assembling Ar leak
• 11:49 am: Assemble up to up-to-air valve
• 11:59 am: Finish assembling up-to-air valve
• 12:00 pm: Break for Lunch
• 1:00 pm: Came back from lunch
• 1:20 pm: Assemble 45 degree elbow [RGA Line]
• 1:35 pm: Finish assembling 45 degree elbow
• 1:35 pm: Assemble Reducing nipple [Pump Line]
• 1:49 pm: Finish assembling Reducing nipple

• 1:53 pm: Attempt to install gate valve [Pump line] but bolts could not fit to the gap between 2.5" reducing nipple (0.95" length, shortest 5/16 bolt is 1.5" in total length).
  Thickness of of CF flange on reducing nipple is 0.75" inch. Ideally, we want to have 0.2" engagement to the gate valve, thus0.95" + 0.25" head thickness = 1.2" > 0.95" gap.
  We thus most likely will need a replacement for the reducing nipple. We decided we would hold up on installing the rest of the pump line until we have got components to fix this problem

• 2:05 pm: Assemble gate valve [RGA line]
• 2:15 pm: Finish assembling gate valve [RGA line]
• 2:18 pm: Assemble 4-way cross [RGA line]
• 2:30 pm: Finish assembling 4- way cross [RGA line]
• 2:37 pm: Assemble manual bellow sealed angle valve [RGA line]
• 2:43 pm: Finish assembling sealed angle valve [RGA line]
• 2:45 pm: Assemble inverted magnetron pirani gauge [RGA line]
• 2:55 pm: Finish assembling magnetron pirani gauge [RGA line]
• 2:56 pm: Assemble vacuum hose, thin wall [RGA line]
• 3:04 pm: Finish assembling vacuum hose, thin wall [RGA line]
• 3:45 pm: Packing up for the the day
• 4:00 pm: End-of-date particle count measurement
  1. Zone 3
     • 0.3 u: 1080
     • 0.5 u: 124
     • 1.0 u: 83
  2. Zone 4
     • 0.3 u: 540
     • 0.5 u: 83
     • 1.0 u: 83

[Pamella, Cao and Julian, Shane]

• Particles account
• 10:37 am: Starting the particles account
1. Zone 3:
   • 0.3u: 1662
   • 0.5u: 872
   • 1.0u: 415
2. Zone 4:
   • 0.3u: 831
   • 0.5u: 124
   • 1.0u: 0
• 11:14 am: Start removal of calibrated leak to install 45 deg elbow
• 11:21 am: Elbow installed, re-install calibrated leak back on
• 11:29 am: Finished re-install calibrated leak, start installing gate valve on pump line
• 11:47 am: Finished installing gate valve, start installing reducing cross onto gate valve
• 12:02 pm: Finished installing reducing cross, start installing 90 deg elbow to reducing cross
• 12:17 pm: Finished installing reducing cross, lunch break
• 01:24 pm: Come back to the lunch break.
• 01:26 pm: Start installing vacuum hose to elbow.
• 01:40 pm: Finished installing vacuum hose.
• 01:43 pm: Start installing turbo pump.
• 02:00 pm: finished installing turbo pump .
• 02:10 pm: Start installing standard wall hose from turbo pump to scroll pump
• 02:21 pm: finished installing hose onto scroll pump, start installing lid. Remove lid from chamber, insert viton O-ring. Place lid back
• 02:30 pm: Secure lids with screw. Start installing turbo pump controller cable: Pass cable from outside (controller) up the top of clean tent and connect to 8 pin connector on turbo pump
• 03:00 pm: Installing air cooling unit for turbo pump, found 8 M3 screws for air cooling unit in the C&B cabinet to install the fan bracket onto the back of turbo pump. Fan control cable is routed up to the top of the cleanroom to the controller
• 03:15 pm: Installing full-range gauge cable to the controller outside cleanroom. Ethernet cables 1 and 2 are used. Cable 1 is used on the RGA line gauge. Cable 2 is connected to the main body gauge. Cable1 and 2 are connected controller's channel 1 and 2 respectively.
• 04:00 pm: Finish installing gauges cables. Cables are routed up along the frame to the controller sitting outside the cleanroom
• 04:15 pm: Finished. End-of-date particle count
  1. Zone 3:
     • 0.3u: 3699
     • 0.5u: 1454
     • 1.0u: 872
  2. Zone 4:
     • 0.3u: 1662
     • 0.5u: 706
     • 1.0u: 290