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.

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.

Attached below are the initial results of the CIT FROSTI testing analysis.

Upon further inspection, one adjustment was made to the FROSTI profile analysis: changing the transmission value of the ZnSe viewport. It was initially assumed that the viewport possessed an AR coating, which would bring the transmission into the 90% range. Without the coating, it drops to roughly 70%. Assuming no coating, the estimated delivered power was calculated to be 11.7 W. This is consistent with the estimated power given from the Hartmann sensor analysis, thus it is believed that the viewport indeed had no coating.

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.

I have begun moving parts into the cleanroom for the upcoming FROSTI RIN tests that will be conducted within the next few weeks. While waiting for the rest of the equipment to arrive to perform the full-scale tests, I have additionally moved the FROSTI under the shelf above the optical table, where it will stay for the meantime. As always, please use caution when in the cleanroom. Aside from the FROSTI, the IR photodetectors that will be used for the test are delicate and costly to replace.

For some preliminary tests, I moved the IR photodetectors outside of the cleanroom and onto the other optical table. The basic goal was to obtain a signal from both photodetectors. To achieve this, one of the heater cartridges used for early FLIR measurements months ago was hooked up to a power supply (PS). The PS was set to supply 0.20 A with a voltage of 2.8 V; the corresponding power is thus 0.56 W. With this, I was able to measure a signal using the Red Pitaya, the device that will be used for following RIN measurements.

The timing chassis used for the cymac has been shut off due to an unknown issue causing its supplied current to fluctuate. All real-time models will be suspended until a solution is found.

Below is the dark noise spectrum of the Red Pitaya, which was measured over the course of a weekend. Additionally, I have successfully measured a signal from the photodetectors with the FROSTI as the IR source, so it seems there shouldn't be any worry of these particular detectors not being feasible for the RIN measurement.

A quick update on the effective emissivity analysis for the CIT FROSTI testing:

I was able to (roughly) match the OPD data to a referenced COMSOL model, with an applied power of 12.6 W (as seen below). However, when changing the emissivity of the ETM in COMSOL, the dT profiles do not seem to change much. I am not sure as to why this is the case at the moment, and will continue to look further.

Additionally attached are the current RIN measurements of the FROSTI prototype. Shown is the PSDs of both channels, in reference to their individual backgrounds.

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.

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.

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.

I downgraded the Red Pitaya back to OS 2.00-18 due to runtime errors during measurement. Once I did this, the device appeared to work much better than it has the last few weeks. First, it appears we can actually see the cutoff of the added low-pass filters that were added in to the RIN setup. Second, there does appear to be a difference again between the FROSTI ON state versus the dark state (i.e. FROSTI OFF). A long measurement of the ADC noise floor in the current configuration still needs to be recorded, but it does appear that the recent highlighted issues with the Red Pitaya have been solved.

Attached below are updated ASD plots for the FROSTI RIN measurements. The parameters set for this are the following:

• DFT Size (N): 16384
• Sampling Frequency (F_s): 7.629 kHz
• Resolution (F_s/N): 0.47
• CH0 DC Voltage w/FROSTI ON: 113.6 mV
• CH0 DC Voltage w/FROSTI OFF: -5.7 mV
• CH1 DC Voltage w/FROSTI ON: 113.0 mV
• CH1 DC Voltage w/FROSTI OFF: -5.7 mV

Each measurement was recorded over a roughly two-day period. Before each spectrum was computed, the time-series signals were AC-coupled (i.e. the DC offset was subtracted from the data). The low-pass filters are still attached for dark and light noise measurements. ADC noise is measured with two 50-ohm terminators attached to the Red Pitaya inputs rather than the IR photodetectors.

I have begun the (hopefully) final RIN measurements at 3:30 PM today. If you need to go into the cleanroom at any time between now and Sunday (the 22nd), please do not touch the FROSTI, the Red Pitaya, the photodetectors, or any of the wiring.

Attached below are updated plots for the FROSTI RIN measurements for Jan 14 group meeting.

On Tuesday, we prepared the FROSTI for disassembly in anticipation of the APS filming that is set to take place in the labs. The FROSTI has been unbolted from the optical table in the cleanroom, with its wires weighted down and the majority of its screws removed to ensure an easy removal of the reflectors during the filming process.

On Tuesday (Jan 21), we took the FROSTI apart in front of a filming crew. It was a success! The footage is going to be used in an APS video detailing the experimental cosmology research conducted in the department.

The FROSTI reflectors, heater elements, and legs were all bagged separately and a currently being stored in the cleanroom. If you need to do any work in there, please be mindful of these parts. The elements are currently on the shelf above the optical table, and the reflectors are placed on the table in the back corner.

Below is a preview of the final RIN figure that will be included in the FROSTI instrument paper. A quick summary of what is shown below:

The original RIN CSD measurement is shown on the top panel in red. Frequency bins that exhibit external electronics noise (ex. ADC, photodetector noise, etc.) are identified and shaded in gray. These noisy bins are then excluded from the dataset before beginning the next step in the analysis process: rebinning. Here, the resolution of the spectrum can be changed by averaging frequency bins together within a specified interval, with the goal of pushing the measurement curve closer to the A+ requirement shown in the figure. For demonstration below, the spectrum goes from a resolution of ~0.93 Hz to 14.90 Hz.

cleaning cleanroom and particle count

• 12:30 pm: Tyler and Aiden started organizing cables in cleanroom
• 12:35 pm: started particle count in flow bench
• 0.3 u: 11681
• 0.5 u: 3284
• 1.0 u: 1039
• 12:50 pm: started cleanroom particle count
  • zone 3:
    • 0.3 u: 14549
    • 0.5 u: 10351
    • 1.0 u: 6194
• zone 4:
  • 0.3 u: 10808
  • 0.5 u: 4655
  • 1.0 u: 1953
• 1:07 pm: began surface check and wipedown, including softwalls
• 1:19 pm: started vacuuming the floor
• 1:28 pm: finished vacuuming the floor
• 1:29 pm: started mopping the floor
• 1:33 pm: finished mopping the floor
• 1:34 pm: started cleaning the buckets
• 1:37 pm: started mopping with IPA wipes
• 1:39 pm: finished mopping with IPA wipes
• 1:40 pm: changed sticky floor mats
• 1:41 pm: started particle count
  • zone 3:
    • 0.3 u: 8397
    • 0.5 u: 5071
    • 1.0 u: 2618
• zone 4:
  • 0.3 u: 6651
  • 0.5 u: 4323
  • 1.0 u: 2120

Today's CyMAC work:
• Finished assembling external power supply cable for the timing chassis (see attached image)
• Also did some debugging of AA and AI chassis re: power issues. After testing voltages at various test points on the power regulator board (TP1-TP6) in the AA chassis, it seems like it's the source of the problem. Used bench DC power supply to test, running 15V, and the correct voltage is coming in to the board but something significantly smaller is being output. We're also getting unexpected negative signs on voltage at certain test points, with leads in correct positions
• Upon further examination, it looks like the lights on the filter boards are actually turning on (in both the AA and AI chassis), though it's only 2/4 lights on each board and they are very faint
• Corrected DC on/off switch spade lug orientation in AI chassis.
• Tested AI chassis power regulator board to see if the problem was the same, and found again that voltage coming in was correct, and voltage going out was not.
• In case of interest in exact numbers, results were as follows:
  • Voltage difference between TP1(+Vin) and TP6(-Vin) is ~30V
  • Voltage difference between grounded chassis wall and TP1 (+Vin) is ~15V
  • Voltage difference between grounded chassis wall and TP6(-Vin) is ~-15 V
  • voltage difference between TP2(+Vout) and TP5(-Vout) is ~3V
  • Voltage difference between TP3 (gnd) and TP2(+Vout) is -0.065V
  • Voltage difference between TP5(-Vout) and ground is ~3V

With the new change in wiring configuration described in elog 136, we tried to power up the heaters for baking the vacuum chamber again.

1. Evidence of smoke originating from CoolSkin insulation

We then removed most of the CoolSkin insulation on the Pump and RGA lines ( apart from the one around the flexible bypass line connecting the two ) (see image Pumpline_afterRemoveInsul and RGAline_afterRemoeInsul) . Upon removal of the insulation, we noticed that the insulating foam melted onto the heating tape (see image MeltedInsulation1 and MeltedInsulation2). This is the first indication that the smoke had most likely coming from the insulating foam itself

Once we started baking, upon reaching 80 degree range. We observed no smoke at the location that we removed the insulation. However, We observed smoked coming from underneath the insulation around the flexible pipe, and not from the velcro areas.

2. The heaters still trip our power

cleaning cleanroom and particle count

• 11:08 am: started particle count
  • zone 3:
    • 0.3 u: 4198
    • 0.5 u: 1080
    • 1.0 u: 581
• zone 4:
  • 0.3 u: 1247
  • 0.5 u: 623
  • 1.0 u: 415
• 11:24 am: break for removal of vac chamber insulation (pictures attached), with counts before removal as seen above, and counts after removal/replacement for zone 3 as follows:
  • zone 3:
    • 0.3 u: 2993
    • 0.5 u: 415
    • 1.0 u: 207
• 12:02 pm: began surface check and wipedown
• 12:13 pm: started vacuuming the floor
• 12:25 pm: finished vacuuming the floor
• 12:26 pm: started mopping the floor
• 12:32 pm: finished mopping the floor
• 12:32 pm: started cleaning the buckets
• 12:37 pm: started mopping with IPA wipes
• 12:43 pm: finished mopping with IPA wipes
• 12:45 pm: changed sticky floor mats
• 12:47 pm: started particle count
  • zone 3:
    • 0.3 u: 2951
    • 0.5 u: 290
    • 1.0 u: 41
• zone 4:
  • 0.3 u: 290
  • 0.5 u: 0
  • 1.0 u: 0