The Linux workstation (ws2) that used to sit on the blue workbench (now inside the cleanroom) has been mounted on a mobile cart, as pictured below. This is intended to be a clean cart that will be housed inside the cleanroom.

The cart is currently dirty and will need to be throughly wiped down (along with the computer monitor and peripherals) prior to being moved into the cleanroom. Once the cleaned cart has been moved inside, it should never be brought back outside the cleanroom and should never be touched with ungloved hands.

I also upgraded the OS to Debian 11.6 and upgraded the CDS workstation tools.

Jon, Cao

In effort to try to reduce the noise level inside the cleanroom, we have dialed all four HEPA fan-filter units (FFUs) down from HIGH to MEDIUM speed. These dials can only be accessed from inside the cleanroom, by bringing in the large ladder and opening adjacent ceiling tiles.

We tested three configurations, in each case with all the FFUs on either HIGH (initial state), MEDIUM, or LOW. We measured the ambient noise in each configuration.

Going from HIGH to MEDIUM yields the largest improvement, reducing the ambient sound intensity by 6 dB (i.e., by a factor of 4, corresponding to a ~35% reduction in perceived volume).

An additional 3 dB of noise reduction can be achieved by further reducing the fan speeds to LOW. However, even after allowing some extended settling time (few hours), we found the particle counts to be fluctuating right at the threshold zone for ISO Class 5. Thus we dialed the fan speeds back up to MEDIUM with the expectation that this will be sufficient for Class 5 performance.

The cleanroom now needs to be recertified with a fresh round of five-zone particle count measurements.

Jon, Cao, Peter

This morning Facilities delivered and installed two new cabinets with sliding glass doors.

The smaller of the two (36" W x 13" D x 84" H) has been installed in the Clean & Bake area adjacent the flow bench. The larger one (48" x 16" D x 84" H) has been installed in the back of the room next to the electronics bench. Both cabinets have been securely anchored to the wall in two places each for earthquake safety.

We also installed the sliding glass doors and leveled them. However, we have not installed any of the shelves yet because the cabinets are quite dirty from the installation. Everything needs to be wiped down with IPA wipes, and it will be easier to do that before the shelves are in place.

Jon, Cao

Today we raised the height of the shelf overhanging the cleanroom laser table by 8 inches. This was done to create more vertical clearance between the top-loading vacuum chamber and the bottom of the shelf. The added clearance should make both removing the chamber lid and inserting large parts easier.

The procedure required unmounting the shelf and removing all eight vertical support posts (1" x 1" x 18.5" pieces of 80/20 unistrut). The support posts were taken to the machine shop and cut, retapped, and cleaned (coarsely, with IPA wipes) prior to reinstallation. We took care to minimize the contamination introduced into the cleanroom, but some amount of particulate from disturbing the shelf was unavoidable.

This work is completed, and the cleanroom is now ready for final cleaning (HEPA vac, mopping, and wiping down of all surfaces including the softwalls).

Today I fixed the final bit related to the nitrogen gas tank, which is to apply sealing tape to M-NPT connector of the hose to prevent leakage (file: AirGunSealed.jpg)
After application of the tape, no audible leak can be heard from connection between the hose and the air gun.

The general operating procedure for the gas tank is as following:

1. Turn the regulator (blue handle) anti-clockwise still it's loose
2. Turn the valve on nitrogen as tank anti-clockwise, immediately the RHS meter of the regulator would jump to approx 2000 psi. This is the standard pressure for high pressure gas tank
3. Turn the regulator clock-wise slowly until the pressure one the LHS meter face reads approx 60 psi. This is sufficient for drying parts with. At this point, the flow pressure still should register zero
4. Press the trigger on the air gun, a high pressure air flow should come out and the flow meter should increase
5. When finished, close the gas tank valve, turn the regulator anti-clockwise, then press the air gun trigger to release gas left in the hose/gun

I set up the new Windows 10 laptop (pictured below), which arrived yesterday. This laptop is intended to be used for running lightweight Windows-only programs, such as the Thorlabs beam profiler software or the SRS RGA client. However, none of that software is installed yet.

Configuration details

As usual, the computer is configured with one shared account (username: controls) and the standard password. Note that it is connected to the campus wifi (UCR-SECURE).

If a connection to the lab's local network is required, then the laptop must be connected by an Ethernet cable to the switch in the top of the server rack.

1. Macor spacer (drawing: LIGO_Redesign_Macor_Spacer_Drawing_v4.pdf attached below), quantities: 40
   • No defects, damages observed
   • Parts are free from grease/ machining fluid
   • Wall thickness of 1 mm appear to provide sufficient stiffness to part
   • Images of parts: Macor_spacer_0.jpg, Macor_spacer_1.jpg
2. Macor 5-40 UNC screw (drawing: LIGO_Redesign_Macor_Screw_Drawing_v6.pdf attached below), quantities: 20
   • One screw broke, location of break: should edge between head and shaft (see image Macor_screw_5.jpg )
   • All other screws look ok, no damage observed, clean surface overall
   • Images: Macor_screw_0.jpg , Macor_screw_4.jpg

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.

There were no issues with the physical replacement of the post, except that the fork clamp on the post needs to be on one of the perpendicular, not diagonal, axes in order to be secure. I chose the front axis (towards the screen) as before in order to easily access the alignment knobs.

To align, I followed the same process as last time except for a more purposeful original rough alignment. For alignment purposes, the visual camera was used. For the first rough alignment, I pulled the camera as far back as possible on the x axis (with the z axis roughly centered), then moved the entire stage setup back until I could just see both the top and bottom edge of the screen. Then, I set the z-axis to an extreme in order to use the edge of the screen to align the rotational and y-axis pieces for the fine alignment.

For the fine alignment, starting with the z and x axis at extremes, I began by aligning the rotational axis. To do this, I used the gaps between the top of the screen and the camera window on the far left and right of the image. When these gaps were equal I knew the rotation was adequately set. Then, I set the y-axis so that the pattern was centered. If the gaps were no longer even, I redid the rotation alignment and ditto with the y axis until both were set. This resulted in a rotation of about two degrees and a y axis at just under 3.5.

To set the z and x axis, I centered the z-axis using the top and bottom of the screen, which should both be visible if the rough alignment was done correctly. Then, I adjusted the x axis by pushing it forward until the top and bottom of the screen were just out of the frame. As with the rotational and y-axis, I iteratively fine tuned the x and z axis until both the image was centered in the z axis and only the screen was in view. This resulted in a z-axis value of just over 5.5 and an x axis value of nearly 1.75.

Pictures are included of all alignment knobs and the new post/stage setup!