[Ma, Luis, Shane]

Working theory for the timing chassis issues had been that the 1A breaker was tripping and causing the failure of the Valon 5015 and 3010 to output the timing signal correctly. We just tried bypassing the breaker, running 6 V on the benchtop power supply (set the current limit to 1.5A), with the 5010 generating the sine wave to pass to the 3010. All worked correctly, and there were no issues. Square wave outputted by the 3010 was exactly as desired (image attached) at the correct frequency, and this confirms the issue was the breaker, not the valon 5015. Ready to go ahead with ordering a new replacement breaker.

We replaced the 1A breaker in the timing chassis today with a 4A one, and tested that all is working well. The chassis successfully outputted the correct signal (image attached). The real time models have also been restarted and the CyMAC diagnostics screen is showing all green flags. Timing chassis has been closed up and reinstalled in the server rack.

I conducted separate tests on the '5015' and '3010a'. When powered individually, the '5015' outputs a signal at 33.55 MHz with an amplitude of 608 mV. It draws 1 A of current from the power source. The input signal for the '3010a' is 33.54 MHz with an amplitude of 670 mV (peak-to-peak) and a 15 mV DC offset. The output signal from channel 1 is a 65.5 kHz square wave with an amplitude of 3.28 V. The '3010a' draws 0.1 A of current.

Both the '5015' and '3010a' work fine when powered separately. However, when both are powered together, the power source behaves as if there is a short circuit. The current theory is that the switch or breaker is tripping, as it has a 1 A current rating. Since the combined current demand of both devices exceeds 1 A, this may be causing the issue.

Slides for 10/16/2024 Group Meeting

After Jon's comment yesterday that some of the connection did not seem to have good metal-metal contact, in particular the gate valve connection, I went through the ConFlat connections today and retighten them. I found a lot of the CF connections are not particularly tightened and there were a lot of range left that can be tightened with the wrench. After re-tightening, the copper gaskets are not visible anymore. For example, see the attached images for the difference before and after tightening.

Note for future installation of CF

• After tightening the bolts/ screws in jumping order (to provide uniform torque) and there is resistance appearing in further tightening, start going through each screw/ bolts in a direction, each time applying a small torque until it resists to further tightened
• After each time going all the bolts/ screw and returning to the starting point, one will find they can further tighten the screws/ bolts. Repeat the process until no further tightening can be achieved
• The copper gasket should not be clearly visible at the connection

• I collected data to plot a calibration with the heater. I took measurements with current and temperature (the thermocouple - thermometer) to compare with the FLIR measurements.
• I made a plot with this data and we can see how temperature vs current behaves. Note: This data I measured manually.

• I noticed that these measurements have some issues with the weather on different days. We can see in the photo attached below how different the temperatures are on different days, I took the data with the same procedure every day, but we can see the differences between them.
• To Do: I will do a new data collection using FLIR and thermocouple at the same time to plot comparison between both.

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.

Luis and Aiden vented the chamber today. We closed off the RGA section and then proceeded to open the the vent on the main body after turning off the turbo and backing pump. We then opened the lid and placed in all the stainless steel hardware that will be used in evaluating the FROSTI optics and heater elements. We also inspected the weldments before closing it up. Check the clean and bake data base where there is now a new section outlining the parts in each test. We then closed the lid, tightened the bolts, turned the backing pump back on and let the pressure drop until it was below 1e-1 torr. Then turned the turbo pump back on and after a few hours the pressure was back down to 4.16e-7 torr. The RGA was turned off during all of this and was turned back on when done even though we closed both valves to keep the RGA volume under vacuum.

Installed a Synology NAS server (Synology RackStation RS1221) in lab room 1129, with host name “scribe” and ip “192.168.1.17”. It is mounted on the rack and each of its 8 storage bays has a 2TB SSD disk. It will be used to set up automated backups of all the lab machines (e.g., chimay, logrus, megatron).

One shared storage is set on it with SHR-2 as its RAID type. It can tolerate the failure of two disks and has 10.4TB of total capacity. 

We can use both rsync and dd to create backups of the system. A suggested backup schedule could be daily rsync backups and bi-weekly disk snapshots using dd. 

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.

I measured the temperature of the flanges and reconnected the RGA turning on its filament. I then turned off the PID controllers.

Here is a table that has the temperature of the different parts of the vacuum chamber.

Fuse replacement

• Replace blown 10A fuse in ucontroller outside cleanroom
• Replace 10 A fuse in main power connection slot of the controller unit inside cleanroom
• Pamella wiped down unit outside cleanroom.
• Controller units turned on and temperature setpoint set to be 80 deg C
• Temperature settle in approx. 15 minutes(as recorded by the RTD). No problems with fuses observed
• Recording of pressure gauges (in Torr) :
  1. Before turning heater on :
     1. Gauge 1(main chamber): 3.73E-7
     2. Gauge 2(RGA line): 3.65E-7
     3. Gauge 3(Pump line): 3.8E-4
  2. After 15 minutes :
     1. Gauge 1(main chamber): 7.07E-7
     2. Gauge 2(RGA line): 6.12E-7
     3. Gauge 3(Pump line): 3.8E-4
• Reduce setpoint temperature to 60 deg C due to Pinrani gauge (Gauge 3) temperature limit
• Upon returned to lab to reduce temperature (35 minutes after turned on):
  1. Gauge 1(main chamber): 1.22E-6
  2. Gauge 2(RGA line): 9.98E-7
  3. Gauge 3(Pump line): 3.8E-4
• Once temperature has settled to 60 C (approx 20 mins after changing setpoint), pressure readout showed:
  1. Gauge 1(main chamber): 1.37E-6
  2. Gauge 2(RGA line): 1.10E-6
  3. Gauge 3(Pump line): 3.8E-4
• Heater left on for the whole afternoon, pressure readout upon returning to lab at 5:30 pm:
  1. Gauge 1(main chamber): 3.43E-6
  2. Gauge 2(RGA line): 2.61E-6
  3. Gauge 3(Pump line): 3.8E-4

• Today I tried get data the heater with the black screen but doesn't looks possible have just one "energy" point straight to FLIR camera. Tyler and I tried different current and temperatures but keep very bad data. I attached a snap below.
• I attached a photo about the new setup below. The FLIR is in the most close point possible/safety with the heater. The heater is very close to the black wall but is not touch the screen so is safety.

Attached is a brief recap PDF file. A video file showing separate HOMs plots for the cavity scan with ETM08 surface map is also attached.

The codes are available at https://git.ligo.org/uc_riverside/hom-rh/-/tree/main/SIS

Ringheater Update

If the link does not work here is the file.

Power point slides

After the feedback from last meeting and Liu's help narrowing down what I should do to improve the model. I made some changes: First with Liu's help I made the proportions of the test mass and ring heater much more reasonable and parametrized by constants. Second from Cao's paper "FROSTI Nonimaging Reflector Design" Liu showed me what I should do to define the elliptical mirrors. Third during Friday's modeling/programming meeting walked me through getting the different irradiance plots to work. 

Heater 1= 72.8; 80.6

Heater 2= 69.5; 80.8

Heater 3= 70; 83.2

Heater 4= 70.6; 78.7

Heater 5= 69.9; 80.6

Heater 6= 71.1; 78.2

Heater 7= 68.5; 76.8

Heater 8= 70.1; 82.8

Heater 1= 73.6; 81.8

Heater 2= 70.4; 82.1

Heater 3= 71; 84.5

Heater 4= 71.5; 80

Heater 5= 70.5; 81.7

Heater 6= 72; 79.4

Heater 7= 69.2; 78.2

Heater 8= 71.1; 84.2

The Red Pitaya ecosystem has been upgraded to OS 2.00-35, with a key feature being greater freedom in adjusting the sampling frequency for signal analysis. Before, decimation factors could only be applied if they were a power of 2 (i.e 2,4,8,16,...) up to 65536. Now, the factors can be any power of two up to 16, and any whole number greater than 16 up to 65536. Further information can be found here.

Some changes have been made to the FLIR readout code to help improve its functionality:

• More accurate temperature readings than before due to updates in the calculation procedure. A bug was causing one of the parameters to not update correctly; this is now fixed.
• Saved data now stored in HDF5 files rather than CSV.
• User can now enable automatic data storage by specifying a collection interval (in minutes). The choice of manually saving data is still present if desired.

Summary

Today I finished implementing an RTS model to read out the integrated FROSTI RTDs (temperature sensors) via the CyMAC. The model is named "MSC" and is located at cymac:/opt/rtcds/usercode/models/c1msc.mdl. We successfully tested it with the heater elements operating in vacuum at low power (12 VDC), finding them to reach an average steady-state temperature of 160 C.

From the cymac host, the MEDM control screen can be accessed with the terminal command "sitemap" (from any directory).

Measurement Technique

Each FROSTI heater element [299] contains an internal two-wire RTD placed near the front emitting surface, which enables the temperature of the blackbody emitter to be directly monitored. From the measured temperature and the emissivity of the uncoated aluminum nitride surface (known to be ~1 in the IR), the radiated source-plane power can also be estimated.

The resistance of each RTD is measured via a ratiometric technique. The RTDs are powered in series with a 1 kΩ reference resistor located inside the readout chassis [305], whose temperature is not changing. The signal is obtained by taking the ratio of the voltage difference across each individual RTD to the voltage difference across the reference resisitor. The advantage of this technique is that the ratio of  the voltage differences is insensitive to changes in the current through the resistors (since they are all in series; see [271] for wiring diagram).

Implementation Detail

The signal flow is shown in Attachment 1. The eight RTD signals enter through ADC channels 0-7, along with the reference resistor signal on channel 8. The first set of filter modules apply a calibration gain to convert the signals from raw ADU counts to units of input-referred voltage. The ratio of each RTD signal to the reference resistor signal is then taken. The second set of filter modules multiply the voltage-difference ratios by the resistance of the reference resistor, 1 kΩ ± 0.01%, to obtain the RTD resistances in physical units of ohms.

Finally, a freeform math module is used to invert the quadratic relation between each RTD's resistance and temperature. The final signals passed to the third set of filter modules are the RTD temperatures in physical units of degrees C. The temperatures of the tungsten RTDs are estimated assuming TCR coefficients of A=0.0030 C^-1 (±10%) and B=1.003E-6 C^-2, which were provided by the manufacturer.

One DAC channel is used to provide the excitation voltage for the RTD measurement, which is visible on the far right of the control screen. At its maximum output voltage of +10 V, the DAC can drive a maximum current of 10 mA.

I performed another continuity test on the RTD chassis wiring, and everything seems to be set up correctly. The chassis should be ready for installation.

Below is the current state of the RTD readout chassis wiring. Initial continuity tests seem good, will run through one more time to confirm.

Today the FROSTI RTD readout chassis underwent a redesign:

Instead of the original ratiometric method, which involved wiring the FROSTI RTDs in series, each element is individually powered by separate excitations. Each element additionally possesses its own reference resistor of 100 Ohm. Now, if an RTD experiences an electrical short, it should not affect the measurements of the others in sequence, as it had with the original design.

The custom front and rear panels for the RTD readout chassis arrived last Friday. I installed them in the chassis frame to check their fit. They fit very well, so all that now remains is to complete the internal wiring and test the connections.

The chassis panel designs are archived to LIGO-D2300452 and LIGO-D2300453.

We noticed that the RTD temperature readings given on the Cymac were off, and traced the issue to miscalibration in the relationship between the resistance and temperature of each RTD (Callendar-Van Dusen eqn). Below is the table of values inferred from independent measurements of temperature and resistance to rectify this problem. This data was then fitted to better determine the coefficients present in the temperature-resistance relation:

       R_0 (ohm)   Alpha    Beta

RTD 0   80.8674   0.001315   4.273e-6

RTD 1   79.5704   0.001887   3.7873e-6

RTD 2   81.7334   0.002014   2.1724e-6

RTD 3   74.3060   0.003677   3.6022e-8

RTD 4   81.1350   0.001761   2.3598e-6

RTD 5   77.9610   0.002423   -7.5192e-7

RTD 6   78.7980   0.001373   6.2909e-6

RTD 7   83.8616   0.001890   3.3529e-6

       R_0 (ohm)   Alpha (1/C)

RTD 0   79.3962   0.002031

RTD 1   78.2874   0.002530

RTD 2   80.9775   0.002381

RTD 3   74.2947   0.003684

RTD 4   80.3199   0.002157

RTD 5   78.2106   0.002297

RTD 6   76.6825   0.002438

RTD 7   82.6645   0.002458

Measurements taken can be found here. An uncertainty of 1 C was assumed for temperature.

Another re-fit, but this time the quadratic coefficient (beta) is set to 1.003e-6:

       R_0 (ohm)   Alpha (1/C)

RTD 0   79.7386   0.001863

RTD 1   78.6248   0.002359

RTD 2   81.3254   0.002211

RTD 3   74.6127   0.003509

RTD 4   80.6652   0.001988

RTD 5   78.5450   0.002127

RTD 6   77.0144   0.002268

RTD 7   83.0204   0.002288

Using the data taken during the FROSTI testing at Caltech, I attempted to find a better calibration of the RTD sensors, given our past issues with inaccurate readings. The fit parameters, alpha and beta, are still all different from the initial values given to us by Fralock (alpha = .003, beta = 1.003e-6, R_0 was not given), but the true values will differ based on factors such as part geometry.

Below are a basic diagram of what the RTD measurement circuit logically looks like and an example schematic of the actual wiring. The schematic wiring will be placed internally into a chassis, connected to the RTDs via DB25 cable.

After updating the wiring in the RTD Chassis, a signal is now seen at each ADC input. However, there seems to be a discrepancy between the voltages I measured out with the multimeter (see below). Next steps include:

• Finish final debugging
• Calibrate ADC inputs with known voltage source (likely to use DAC).

Voltage Readings:

RTD 1: 0.576 V

RTD 2: 0.578 V

RTD 3: 0.598 V

RTD 4: 0.563 V

RTD 5: 0.477 V

RTD 6: 0.463 V

RTD 7: 0.456 V

RTD 8: 0.491 V

Reference Resistor: 5.463 V

Total Voltage: 9.665 V

After further modification of the RTD readout chassis (i.e. adding resistors, placing reference resistor in front of RTDs), here are the following direct measurements:

RTD 1: 0.484 V

RTD 2: 0.486 V

RTD 3: 0.503 V

RTD 4: 0.474 V

RTD 5: 0.495 V

RTD 6: 0.483 V

RTD 7: 0.476 V

RTD 8: 0.510 V

Reference: 5.847 V

Here are the Cymac signal readings:

RTD 1: 74

RTD 2: 67

RTD 3: 73

RTD 4: 45

RTD 5: 82

RTD 6: 75

RTD 7: 70

RTD 8: 71

Reference: 884

The one (possible) discrepancy here is the readout for RTD 4 via Cymac, since it's signal reading is ~30 counts lower than the others. I do not believe this is a wiring issue due to the direct measurements taken.

After initial analysis from last week on a single RTD, I then extended to looking at all 8 in series with R_ref (set to 1 kOhm). Shown below are the edge cases for the setup:

• RTDs are all at ambient lab temperature. This would correspond to a minimum resistance value.
• RTDs all read out 400 C. This gives the maximum resistance value.

The results show that indeed only a few mA of current is drawn even at room temperature (a little above 5.5 mA), and this will continue to decrease with increasing temperature. The voltage across a single terminal, at a maximum, is only about 5.4 V.

I tried adjusting the gain settings on the photodetectors to check if this would help improve the RIN spectra measurements. Overall, it doesn't look like it does, and if anything, looks worse. I assume this is so because as the gain is lowered, the amount of detectable signal from the FROSTI becomes smaller and smaller.

We've added two low-pass filters in hopes of reducing any potential aliasing that may be introducing additional noise into the power spectra for the RIN measurements. It still looks like the noise levels are too high. Attached below are some recent measurements taken with the FROSTI powered on and off.