cleaning cleanroom and particle count

• 3:37 pm: started particle count
  • zone 3:
    • 0.3 u: 1205
    • 0.5 u: 748
    • 1.0 u: 249
• zone 4:
  • 0.3 u: 1496
  • 0.5 u: 748
  • 1.0 u: 290
• 3:57 pm: began surface check and wipedown, including softwalls. NOTE: vacuum chamber insulation crumbling at edges, dropping loose flakes. Scatters residue whenever jostled, so wiping it down just releases more. Not enough flakes are being released for it to be a major issue, but definitely something to keep an eye on.
• 4:18 pm: started vacuuming the floor
• 4:29 pm: finished vacuuming the floor
• 4:30 pm: started mopping the floor
• 4:35 pm: finished mopping the floor
• 4:36 pm: started cleaning the buckets
• 4:41 pm: started mopping with IPA wipes
• 4:52 pm: finished mopping with IPA wipes
• 4:52 pm: changed sticky floor mats
• 4:53 pm: started particle count
  • zone 3:
    • 0.3 u: 3367
    • 0.5 u: 1787
    • 1.0 u: 914
• zone 4:
  • 0.3 u: 1039
  • 0.5 u: 498
  • 1.0 u: 249

[Luis, Luke, Tyler]

Vacuum chamber parts were finally received and assembled. After whipping down the parts, the blank was removed from the reducing cross. Then, the zero-length reducer was attached. Lastly, we installed the T that had the argon leak and RGA. The final pump down showed signs of an improved seal since the pressure dropped quite fast. This pressure is well bellow the limit required to use the RGA, argon test leak could be performed some time next week.

[Luis, Luke}

Three RGA scans were taken. The improvement in the amount of HC in the vacuum is visible across the different measurements. Images are attached.

The following images compare the RGA scans from 9/23/24, after the first bake with the new vacuum system, with those from 3/14/24, after bake 12 with the old system.

The first image shows a graph of the raw data and includes the calibrated leak for both curves. As we can see, our new system meets LIGO standards of cleanliness.

The second graph contains the plot of the normalized data.

The following figure displays data acquired on 10/09, and it shows that we are no longer below the cleanliness standard. Also, the system's pressure went up to 1.9x10^-8 Torr (approximately 7x10^-9 Torr previously). This might be due to a leak somewhere in the system. More tests will be performed later.

[Luke, Luis, Mary, Ma]

On 10/22/24 Luke, Ma, Mary and myself ran a leak test, the results are displayed below. The overall pressure of the vacuum was 2.0e-8 and the temperature readings were 26C for the RGA and 25C for the main volume.

[Luke, Luis, Mary, Ma]

On 10/22/24 Luke, Ma, Mary and myself ran a RGA scan, the results are displayed below. The overall pressure of the vacuum was 2.0e-8 and the temperature readings were 26C for the RGA and 25C for the main volume.

As we can see, the vacuum is passing cleanliness standards again.

[Luke, Luis]

On Friday, 11/1/24, the MR was unpackaged and cleaned under the flow bench. We noticed an ink stain on one of the corners of the material. After wiping it down with IPA and Vector Alpha wipes, the stain was removed. However, the material showed some wear.

After cleaning, we placed it in the bake station and applied a stainless steel baking protocol. On Tuesday, 11/4/24, the material was removed from the furnace and packaged in a static shielding bag. The MR was wrapped in Vector Alpha wipes.

[Luis, Luke, Ma Michael]

The isolation test was conducted on the vacuum system. Every pump was turned off under vacuum, and pressure measurements were taken every minute for 15 minutes. The results are displayed in the sheet linked at the end of this report. The pressure of the main volume dropped very slowly.

The pressure of the RGA Volume dropped in an exponential manner. The test had to be paused at 11 minutes due to concerns about the pressure exceeding the lowest permitted level for the RGA filament.

After the ISO test was performed, we attempted to tighten the bolts of the small turbo pump on the RGA Volume. However, we noticed that the pressure had increased by nearly an order of magnitude, going from 3.27 × 10^-9 Torr to 1.45 × 10^-8 Torr when both volumes were separated. We conducted a leak test for that particular flange and found a concerning leak of 2.15 × 10^-8 Torr, which had previously been 1.9 × 10^-9 Torr. We believe the copper seal was damaged during the ISO test.

View the results sheet

[Luis,Shane]

An RGA scan was taken on Dec 4th. The results are attached at the end of the e-log. As we can see, the scan results are under the allowed limits. After the scan, Shane and I worked on the vacuum connections. The filament was turned off, and the RGA was disconnected from Spica.

After we finished the tests, we reconnected the RGA and attempted to turn the filament back on. However, the program was unable to connect to the instrument. We checked for any loose connections but did not find anything. The RGA connection needs to be troubleshot and fixed.

[Luke, Luis]

After the gasket replacement performed on Monday (11/18/24) we let the vacuum pump down to UHV pressure for a couple days. Today (11/20/24) we measured the pressure to be 5.30*e^-9 with a temperature of 22C, and we performed a leak test and RGA Scan.

Here are the results:

[Luis]

I rebooted Spica and I was able to connect the RGA again. After Connecting the RGA, I left the filament on.

[Luis, Luke]

RGA Volume: T = 21°C, P = 1.74e-9 Torr
Main Volume: T = 22°C, P = 5.60e-9 Torr

We performed an RGA scan of the system. As we can see, we met cleanliness standards. The S/N ratio was roughly calculated and it is about 100. I will update the code to make this calculation and to have it displayed on the plot in the next scan we perform.

After this, we closed the RGA to the main volume valve, degassed the filament, and after the pressure came down to what it was initially, we reopened the valve. After the degassing, we took another scan. The overlaid plots are attached below.

The noise floor seemed to be about the same. I will take another scan tomorrow to verify whether it was the same or if the system just needed a little more time to be completely clean.

[Luis]

RGA Volume: T = 23°C, P = 1.71e-9 Torr
Main Volume: T = 22°C, P = 5.71e-9 Torr

On 12/13 I took another RGA scan to verify the state of the vacuum system and to see whether the degassing of the filament had worked. The results of the scan shows that we did get an overall improvement of the noise levels, though we still have some peaks that are higher than the rest.

Also, while I was around, I transferred the Viton O-rings to a bag and labeled it properly. They are ready to be put into the clean room.

[Luis, Luke]

The MR material was placed in the vacuum chamber following standard procedures to ensure the vacuum remained as clean as possible. During this process, we only opened the main volume while keeping the gate valve between the two volumes closed to maintain the UHV in the RGA section.

An RGA scan was taken before this process, this will be used to compare the state of the vacuum with the sample inside to determine whether the MR material is vacuum compatible.

[Luis]

The vacuum system is being baked. I disconnected the digital gages and the magnets, opened the Ar leak and started the bake by taking the temperature from 60C-90C-125C waiting about 15-20 minutes between each interval. The RGA electronics were left on since the temperature of the flange was 36.6C (bellow the 60C threshold)

[Luis, Luke]

RGA Volume: T = 23°C, P = 3.0e-9 Torr
Main Volume: T = 22°C, P = 9.90e-9 Torr

After letting the vacuum cool down for a couple days, we reattached the magnets and sensors, then we performed a RGA scan of the vacuum system, now containing the MR sample. The results are attached below. Something to notice is that we are technically not under UHV, though Luke and I believe the reading of the sensor is not completely accurate since it was still coming to a steady state, further test will be performed when the physics building is open again.

[Luis, Luke]

RGA Volume: T = 22°C, P = 2.10e-9 Torr
Main Volume: T = 21°C, P = 5.71e-9 Torr

Measurements of the current state of the vacuum systems were taken today, now that the system had reached UHV status, the results are attached bellow. The first plot overlays the data of the empty chamber taken on 12/16/24 before inserting the MR material, and the data of the system today, with the MR inside. The second plot displays the S/N Ratio of the system. The last plot displays the data of the system with the Ar leak open and closed. Notice that it is common for the Ar leak close data to fail due to the calculation of the gas flux per unit ion current, which is dependent on the Ar peak.

[Luis, Ma]

Feb/10/25 4:00pm

Bake was stopped.

[Luis]

Feb/11/25 9:30am

Pressure gages were connected.

[Luis, Luke, Ma]

February 12, 2025 - 4:00 PM

We performed an RGA scan with the vacuum system containing the heater elements. The results are attached below.

As we can see, we are not yet under cleanliness standards. The passing threshold is 4 × 10⁻¹⁰, and we are currently measuring nearly double this value. We will continue performing scans to monitor any changes in these readings.

[Ma, Luis]

February 20, 2025 - 3:30 PM

Ma performed an RGA scan with the vacuum system containing the heater elements. The results are attached below.

As we can see, we are not yet under cleanliness standards. The passing threshold is 4 × 10⁻¹⁰, we are very close to it.

[Ma, Luis]

February 24, 2025 - 1:00PM

Ma performed an RGA scan with the vacuum system containing the heater elements. The results are attached below.

I have been looking at the feasibility of an alternative heater element design for FROSTI that replaces the original ring-like heater elements with n rectangular elements with straight edges. They form an n-sided regular polygon that could well approximate the original annular ring if n is large enough. This eliminates curved surfaces requirement for the heater elements, which was the source of the many month production delay for the prototype parts.

This design was implemented in COMSOL, shown in the attached. From the face on view, each element has a trapezoid shape with straight edges. The edges between neighboring elements are parallel, with a space of 2 mm in between them.

The ray tracing and thermal analysis obtained from COMSOL are shown in the attached pdf.

In particular, the 2D irradiance profiles were obtained from the ray tracing (so far from the front heating surfaces only). The 1D radial profiles were integrated and shown in the attached. The power delivery efficiency for the original ring-like heater element design is integrated to be roughly 65%, for comparison. The plot also shows the radial irradiance profiles for three different straight-edge designs, which correspond to 16 edges, 18 edges, and 24 edges. We see that with the straight-edge designs, the irradiance profiles stay in a good Gaussian shape. In addition, with a larger number of edges, the power efficiency increases, but is always less than the case for the optimized ring-like design.

The thermal distortions for the TM were also obtained from COMSOL, using the irradiance profiles at the TM HR. As shown in the attached, with the straight-edge design, the effects on the thermal lens OPD and the HR surface deformation are similar to the ring design, but with less severe edge roll-off for instance.

In the previous post, we saw that for the heater element design with straight edges in replacement of the current eight-element ring-like design, it provides the similar Gaussian-like irradiance profiles, but with smaller power delivery efficiencies, as shown in the plot. This turned out to result in similar but less prominent thermal effects.

They only differ from the original baseline design by a source power rescaling, however, as shown in the plot, where we see the power-rescaled irradiance profiles for the straight edge designs are close to that for the ring design. The resulting temperature profiles and thermal distortions are shown in plot and plot. The thermal effects for the 16 straight-edge design with renormalized source power for instance are strikingly similar to that for the original ring design.

An alternative straightened heater element design has also been investigated with COMSOL FEA simulation. As shown in the attached, in this new design each heater element component is cut with multiple straight edges but remains connected, shown in the same colors (green and red). In the example, four straight edges are cut from each of the four heater components (4x4=16 edges in total). There is no spacing between the neighboring edges from the same element component, but the edges from different components are separated by 2mm, as can be seen in the attached. This new N-in-one straight edge design offers similar irradiance compared to that for the evenly-spaced N-sided regular polygon straight edge design with the same number of edges, as shown in the plot. It however has fewer heater components, four in this case, which makes it easier to implement in assembly and wiring, and less vulnerable to electrical and thermal shorts with their fewer heater element pins.

Drawings and CAD models of the straight-edge designs are exported, and are visualized in SOLIDWORKS. Two are attached. One is a single edge of the evenly spaced polygon design with 16 edges, and the other is the 8x2 design, with two neighboring edges grouped together to replace the original single curved heater.

For the straight edge design in COMSOL, ray power detectors were placed at the heater's front surface. The irradiance is shown in figure. The amount of light rays deposited back to the heater is small when close to the center, where it is closer to the original ring. The ray power increases as we move further away from the center toward the edges. In addition, the total power integrated at the heater's front surfaces is about 21% of the original heater's emitted power. This could account for the power efficiency difference between the straight edge design and the ring design, as shown in plot for instance.

For this study, we looked at a simple case with an aLIGO-like test mass geometry (R=0.17m, H=0.2m) plus a barrel RH with 0.02m width at 0.03m from the AR surface with FEniCSx. The irradiance profiles are constant inside the width along the longitudinal direction, and zero outside the width. For the baseline non-astigmatic actuation with constant irradiance azimuthally. We have obtained roughly equal quadratic actuations along the x and y directions, as shown in figure. The total delivered power on the entire barrel is normalized to 1 W. The actuation on the curvature per power Delta S/Delta P in this non-astigmatic case thus is 0.835 uD/W.

For the astigmatic case however, the irradiance for the regions from one diagonal is increased by a given amount, compared to the non-astigmatic case, whereas for the other diagonal regions is decreased by the same amount (thus the total power is unchanged at 1 W). The HR deformation when the power is changed by 50%, for instance, is shown in picture, where the deformation along the x direction is larger than the y direction. The deformation in each direction however remains quadratic, with different curvature per powers for the x and y components, as shown in plot. The actuation on the curvature per power for an increasing amount of astigmatism is shown in plot. In terms of Zernike polynomials, the maximum amount of Z22 (astigmatism) for 1 W of total power is 2um while the remaining curvature content (Z20) is 6nm. This is shown in plot.

For a quick projection for the resonant frequencies going from aLIGO to CE, the height and width of the BS are increased assuming the mass is increased from 14 kg to 70 kg, while keeping the aspect ratio fixed. The resonant frequencies for the two mechanical modes as a result becomes smaller, to 1.43 kHz and 2.11 kHz respectively, risking getting in the detection band.

Next step is to implement a mechanical ring with high stiffness outside the BS barrel to combat the decrement of the resonant frequencies of the relevant mechanical modes.

This is to optimize the FROSTI heating profile for ETM, by minimizing the residual RMSE of the HR surface deformation after the beam size weighted curvature is removed by the current RH. The parameters of the profile being explored are the location, width, and total power for the Gaussian Annulus. As shown in the attached series of plots, the optimal location is 9.9 cm, with a width of 7.7 cm, and a total FROSTI power of 12.7 W (for 1 W of Gaussian beam absorption). The residual RMSE is 1.2 nm. About 0.5% of the FROSTI power is lost at the edges of the TM.

For comparison, without FROSTI, the residual RMSE after the beam size weighted curvature removed by the current RH is 44.5 nm. When the width of the Annulus is set to be 3 cm however, the residual RMS is 3.1 nm, with much smaller FROSTI power needed at 4.7 W, and less power loss at 0.02%.

Today we started re-configuring the vacuum chamber components.

Particle count
• 10:45 am : Starting the particle count in the clean room.
• 11:13 am : Finished the particle count in the clean room.
• Zone 3 :
  • 0.3 u: 2535
  • 0.5 u: 1413
  • 1.0 u: 789
• Zone 4 :
  • 0.3 u: 457
  • 0.5 u: 290
  • 1.0 u: 207
  Starting the reconfiguration.
  • 11:21 am: Started removing up-to-air valve
  • 11:30 am: Finished removing up-to-air valve.
  • 11:33 am: Started removing calibrated Ar Leak and the elbow.
  • 11:35 am: Finished removing calibrated Ar Leak and started assembling the up-to-air valve.
  • 11:47 am: Finished assembling up-to-air valve.
  • 11:48 am: Started removing magnetron gauge.
  • 11:55 am: Finished removing magnetron gauge.
  • 11:57 am: Started installing the elbow and calibrated Ar Leak and started removing the RGA probe
  • 12:13 pm: Finished installing the elbow and calibrated Ar Leak.
  • 12:20 pm: Break for lunch.
  • 01:25 pm: Come back from lunch break.
  • 01:30 pm: Started removing RGA line.
  • 01:39 pm: Finished removing RGA line.
  • 01:39 pm: Started removing gate valve [RGA line] and finished removing gate valve.
  • 02:00 pm: Started installing gate valve in the new position.
  • 02:08 pm: Fished installing gate valve [RGA line].
  • 02:09 pm: Checked the screws in the elbow to gate valve. [RGA line].
  • 02:28 pm: Finished checking the screws in the elbow to gate valve [RGA line].
  • 02:29 pm: Started installing RGA line.
  • 02:39 pm: Finished installing RGA line.
  • 02:50 pm: Started installing magnetron gauge.(In this part we assembled gauge with the used gasket)
  • 03:02 pm: Finished installing magnetron gauge.
  • 03:04 pm: Started installing RGA probe [RGA line].
  • 03:13 pm: Finished installing RGA probe [RGA line].
  • 03:15 pm: Connected the cables to the magnetron gauge.
  • 03:20 pm: Started the testing in the vacuum chamber.
  • 04:30 pm: Started installing the RGA 200 and connected the cables (power cable and DB9 cable).
  • 04:52 pm: Finished installing the RGA 200 and connected the cables (power cable and DB9 cable).
  • 04:53 pm: Started testing the RGA connections. Logrus is able to recognize and connect to RGA unit. We are leaving the turbo pump on for a few hours before checking back for pressure readouts.
  • 05:00 pm : Starting the particle count in the clean room.
    1. Zone 3 :
       • 0.3 u: 2244
       • 0.5 u: 997
       • 1.0 u: 207
    2. Zone 4 :
       • 0.3 u: 2993
       • 0.5 u: 1579
       • 1.0 u: 498
  • 05:30 pm : Finished the particle count in the clean room.
  • 05:34 pm: Test pressure readout from the gauges.
    1. Channel 1 : 1.06E-5 mbar
    2. Channel 2 :8.89E-6 mbar
    3. Channel 3 :5.0E-4 mbar
  • 05:59 pm: Test pressure readout from the gauges.
    1. Channel 1: 9.09E-6 mbar
    2. Channel 2: 7.75E-6 mbar
    3. Channel 3: 5.0E-4 mbar

[Jon, Cao]

1. Re-routing of cables

We re-routed the connections between the turbo pump and its fan to the controller. Instead of going through the side of the server rack, they are now routed along the the cable tray and came down from the top of the server rack.

2. Planning for vacuum assembly re-configuration

• Move the entire RGA arm to the mirrored CF port, where the Up-to-Air valve is at
• Move the Up-to-Air valve to the calibrated leak port
• Move the calibrated Ar leak the main chamber full-range gauge port
• Move the full-range gauge to the RGA line port

3. First test pump-down

1. With all valves closed, we started scroll pump, pump line quickly got down to 6.08 mbar from atmospheric 1000 mbar (measured by Pirani gauge, channel 3 on controller )
2. We open Lesker angled valve and let the RGA arm pumped down, Pirani gauge read 6.3 mbar while the full-range guage on RGA line reads 4.9 mbar ( channel 1 on controller )
3. We open the pump line gate to expose the pump to the main volume, all gaugues readout immediate rise back up 1000 mbar. After 3 minutes, we started to see channel 3 slowly dropped down. A minute later channel 1 and 2 (main body) also dropped down. The slow pressure dropping speed and 6.3 mbar measured earlier got us suspected that there is some large leaks
4. We proceed to tighten all the ports as the vacuum is pumped down. In particular, we found that large feedthrough port still required a lot of tightening up
5. As we tighten up all the ports, after 40 minutes, the gauges are now
   • Channel 1 : RGA line full-range gauge: 2.55E-1 mbar
   • Channel 2 : Main chamber full-range gauge: 2.60E-1 mbar
   • Channel 3 : Pump line Pirani gauge: 2.94E-1 mbar
   Compare this to the scroll pump manual , Table 1, page 3, the ultimate pressure of the scroll pump is 2.5E-1 Torr (3.3E-1 mbar), we thus managed to achieve scroll pump ultimate pressure
6. Turn on turbo pump : Change turbo pump controller from REMOTE to FRONT PANEL mode by pressing both "COUNTERS" and "MEASURE" buttons at the same time, select "MODE=FRONT"
7. Shorting interlock pin: since we do not have an interlock signal for the controller, use the provided DB-9 connector that has pin 3 and 8 shorted and connect this to the P1 IN connection at the rear of the controller (see attachment 1 )
8. Press "START" on the controller to start the turbo pump
9. The pressure readout from the gauges quickly dropped down. After 3 minutes, the Pirani range is maxed out at 0.5E-3 mbar. After 20 minutes, we recorded the following values:
   • Channel 1 : RGA line full-range gauge: 1.50E-5 mbar
   • Channel 2 : Main chamber full-range gauge: 1.89E-5 mbar
   • Channel 3 : Pump line Pirani gauge: 5.0E-4 mbar
   This is Medium vacuum , we want to further reduce this by 2 orders of magnitude. However, we can run RGA test + helium leak test at this pressure
10. Turn off turbo pump, wait for 10 minutes, turn off scroll pump, open Up-to-Air valve, all pressure gauges indicated pressure returned back to atmospheric pressure

3. To-do actions

• Run RGA test to get information about contamination status of vacuum
• Implement suggested changes in section 2
• Check and modify suspected poor connection: Pirani gauge on pump line. A gap can be seen between connection. There's no good way to tighten it with the screw. Maybe use threaded pin + hex bolt?
• Controller communications

Summary : We resolved problems with heaters tripping power and were able to proceed with chamber baking

1. Circuit connection adjustment

After yesterday elog 137, today we resolved most of these issues. After Jon contacted Facilities, the LP3B 6 circuit was reset and the cleanroom filter & light panels resumed to work as normal.

Regarding the connection of the heaters. we made the following adjustments:

• High-temperature controller powering lid + upper volume heater: connect to LP3B 8 circuit (clean room sides, 2 outlets)
• High-temperature controller powering bottom + lower volume heater : connect to LP3B 4 circuit (workstation side, 2 outlets)

2. Replacement of vacuum nipple insulation

We had also received new insulation pieces from Worbo today to replace the existing insulation with the new ones (see images). These cover the 2 4" tubes (for 6" flanges ) and the 4 1.5" tubes (for 2.75" flanges). The new insulations fit perfectly on these tubes. I also placed all insulation taken off from the last elog back onto the chamber ( these are insulations for the pumps and RGA lines).

3. Baking

• Starting set point: 40 deg C
• Step increase: 10 deg C up to 80 deg C, 5 deg C from 80 deg to 120 deg C
• At each step, the temperature readouts show approx. 2.1 deg C overshooting, wait to settle back to approx 1.5 deg C overshoot before increase the set point again

The temperature of the chamber reached as stable 120 deg C without any power issues at 3:45 pm. I waited another 15 minutes to verify its stability and the official baking duration started at 4:00 pm Jun 29 2023. Since we are baking at 120 deg C instead of the standard 150 deg C for Aluminium, the duration for the bake will be over three days until Monday morning, upon which we will slowly ramp down the the temperature.