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  SUS Lab eLog, Page 37 of 37  Not logged in ELOG logo
ID Date Author Type Categorydown Subject
  1811   Fri Aug 23 15:22:59 2019 DuoDailyProgress L1 noise and average

Going to see if # of average makes any difference.

  1812   Mon Aug 26 14:57:47 2019 DuoDailyProgress ETMY noise vs. ITMX noise

The formula used to calculate the noise is

Noise = Sqrt[1 - coherence] * drive

ETMY is about the same as ITMX.

  1813   Mon Aug 26 15:13:41 2019 DuoDailyProgress Noise vs number of avg

More avg - more smoothiness but the shape of the noise curve is the same.

  1814   Tue Aug 27 14:41:04 2019 DuoDailyProgress Average 10

Trying to see if I can reproduce https://alog.ligo-la.caltech.edu/aLOG/uploads/43363_20190213151300_subtraction_offset.png when I use average of 10.

  1815   Tue Aug 27 14:59:00 2019 DuoDailyProgress Average 10

No. Did not reproduce it. Attachment 3 is the same plot without restrictions on the y axis range.


Trying to see if I can reproduce https://alog.ligo-la.caltech.edu/aLOG/uploads/43363_20190213151300_subtraction_offset.png when I use average of 10.


  1816   Wed Aug 28 13:20:01 2019 DuoDailyProgress Window changed to BMH

The result is lower when I change the window but still not the same as alog post. A factor of 2 larger at 30Hz.

  1817   Wed Aug 28 13:39:29 2019 DuoDailyProgress Changed bin size to 0.1Hz and got it

The bin size was 1Hz. I changed it to 0.1Hz. Now we get some real data.

  1818   Wed Aug 28 16:15:51 2019 ranaDailyProgress Changed bin size to 0.1Hz and got it

Can't tell what's going on. Pleaese make the plots readable and describe in the elog what precisely is being calculated.

  1823   Wed Oct 2 13:50:03 2019 DuoDailyProgress ITMY noisemon

This is the DAC noise of ITMY PUM coil driver in L1. The data is from September 25, 2019 00:00:00 UTC. I did not subtract the ADC noise and the noisemon noise since I did it for ITMX. The noisemon noise is far below the total noise, and the ADC noise only dominates high frequency. After subtraction, the mismatch above 500Hz will disappear.

There are some lines around 65Hz. I checked the data a few days arounds 9/25. I see them in all the data. I do not understand why yet.

Spectra of the PUM drive signal is attached in 3, noisemon output in 4. I do not see anything at 65Hz in those channels.

ADC noise and Noisemon noise are subtracted in attachment 5.

I checked these data

9/23 00:00, 8:00, 20:00

9/24 8:00,

9/25 0000,0800,2000

9/26 0800,2000

9/27 0000.0800.2000

10/1 0800

The 65Hz harmonics stays there.

I checked time domain for 9/15. It is not saturating. (Attachment 6&7)

Attachment 8 is a check on the output of the noisemon signal when L1 is down. It is from 9/24 1600. Surprisingly, I see the 65Hz harmonics in UL spectrum while I cannot see it when the interferometer is online. I do not see the harmonics in the other three channels.

In attachment 9, I checked ITMX from the same time (9/24 1600, interferometer down). The 65Hz harmonics is there in all channels, and the UL output is higher.

  1824   Tue Oct 8 17:31:27 2019 DuoSummary Noisemon check

Noisemon has been installed at L1 for a while. Now we have it on ITMX and ITMY. ITMX was installed first and ITMY was installed on September 11.

Recently, after it was installed at ITMY, we were trying to check the functionality of the circuit - if it measures DAC nosie properly between 20 - 100Hz. When we were doing that, we encountered some strange harmonics of 65Hz in UL channel. It is shown in attachment 6, data from 9/25 ETMY.

We traced back to where it was installed at ETMY, 9/11, and we still see the lines there (attachment 5).

Then we went to check ITMX, since the data was consistent when it was first installed. However, when we use 9/25 data, we see attachment 4. The UL channel measurement is way above the other three channels. Tracing back the dates, we found in ITMX it started 9/10 (attachment 3), comparing to 9/9 (attachment 2) when it was still good.

All the data and scripts are in attachment 1.

Notes (in case you read about noisemon for the first time):

All the plots are

drive\times \sqrt{1-coherence}

It is suppose to be DAC nosie + Noisemon noise + ADC noise, which DAC noise being dominant between 20 - 100Hz. The purple curves are DAC noise model. The measurements are expected to be close to it between 20Hz and 100Hz.


  1825   Wed Oct 23 20:37:53 2019 DuoDailyProgress Nosiemon check

Although L1 has been down since the beginning of October, I checked the spectrum at the output of the nosiemon at L1 ITMY. It looks like the UL channel, as we have seen before, still has the lines,

  1826   Fri Nov 8 13:32:15 2019 DuoDailyProgress Noisemon and FastIMON at L1

I checked the October 25 data at L1. The drive signal is zero, according to the bottom plot in attachment 1 and 2. The fastimon channel has a lot of lines. Noisemon still has the 65Hz harmonics.

I also checked the Nov 7 noisemon and fastimon data. We still see the harmonics on Nov 7. Also, one channel is completely dysfunctioning. The fastimon is similar to Oct 25.

Attachment 1: Oct 25 noisemon. We still see the harmonics in the noise.

Attachment 2: Oct 25 fastimon. Two channels are messy.

Attachment 3,4,5: Nov 7 noisemon data. Analyzed in attachment 4. Data in attachment 5.

Attachment 6: Nov 7 fastimon data. Similar to Oct 25 - a lot of lines.

  1827   Mon Nov 11 20:35:13 2019 DuoDailyProgress First sign of ITMY LL noisemon saturation

Noisemon has been installed in LLO ITMY station. Its LL channel starts to saturate at 10/30 00:00:00. I checked the noisemon output at that time (attachment 1).

  1828   Thu Nov 14 15:04:25 2019 DuoDailyProgress ETMY check

The first noisemon board was installed at the ETMY station. It was a prototype board that we brought to LLO and installed there since then. I checked the data today (11/14) and its LL channels is not working.

I checked the time series in the attachment 2 and 3. There are some problem causing the circuit to saturate.

I checked the drive signal below 10Hz in attachment 4. The drive signals across all channels are the same.

  1829   Thu Nov 14 15:54:57 2019 DuoDailyProgress Issue consistency among ETMY, ITMX and ITMY

I checked the behavior of noisemon in the three stations where they are installed. It is consistent that there is always one channels that is saturating and one channel that has excess noise. However, they are not always the same channels.

ETMY, attachment 1, LL saturating, UL excess noise (UR a little more noise)

ITMY, attachment 2, LL saturating, UL excess noise

ITMX, attachment 3, UL saturating, UR excess noise

  1830   Thu Nov 14 17:14:32 2019 DuoDailyProgress Noisemon problem observation

Saturation occurs suddenly after running for hours without problem.

I tracked it since the drive was turned on (around 00:36:18) and found that it has been running ok for hours before this happens (attachment 1). Around 3:04:51, the LL channel saturated and then dropped back to normal level. After that, this kept happening and crashed the LL channel (attachment 3).

Attachment 2 is data corresponding to attachment 1.

  1831   Mon Nov 25 16:43:50 2019 DuoDailyProgress Time domain projection is consistent with LLO data (except LL channel, which saturates)

We see a report of noisemon problem from LLO: https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=49892

The time domain data is projected with the transfer function measured here: https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=43212

We projected the output of the noisemon signal on time domain (attachment 1).

Attachment 2 is data from LLO posted in the alog above. Compare this with attachment 1, we can see our projection has roughly the same values with the other three channels. This means those channels have high number of counts because the drive signal is bigger. In other words, the other three channels should be working ok.

I attached the drive signal being projected in attachment 3.

Attachment 4 has all the data and code.

  1832   Wed Nov 27 23:45:29 2019 DuoDailyProgress Noisemon Debug Progress

I found that two of the channels misbehaves after the board runs for a couple hours. Turning the power off and back on returns the circuit to normal functionality.

I sent 100 counts amplitude 10Hz sine into the board.

  • I saw channel 4 has some bad behavior - about 3V of offset with a lot of noise and one spike goes up to saturation.

Then I switched power off and back on. It worked normally. I increase amplitude to 2500, same as Carl's 10000. It worked normally as well. However, when I came back after a couple hours,

  • I saw two channels (1&4) saturates about 4 times a second. The other two still ok. (attachment 1)

 Then I turned power off and on again. I got attachment 2 - normal behavior again.

  1833   Mon Dec 2 15:28:03 2019 DuoMisc S1900296 board damaged

I think I shorted somewhere near the RTN testpoint on the board today while testing it. I saw some sparks. After that the board becomes non-responsive - it is not responding to whatever signal I send in. I will use another board and go on with testing.

  1834   Tue Dec 3 09:50:18 2019 DuoDailyProgress Interesting observation on noisemon debugging

We have observed that the noisemon bug happens after it is powered on for about 1.5 hour. Noisemon has been powered on overnight and the following morning I came in and found

- Channel 1, 3, 4 bad (with signals like attachment 1. Green: normal behavior driven with 250 count, 10Hz signal. Brown: abnormal behavior with no drive)

- Then I used the oscilliscope and did the following on channel 4:

1. Connected channel 1 to measure the voltage between one side of C2 and GND.

2. Connected channel 2 to measure the voltage between another side of C2 and GND.

3. Use MATH on the oscilliscope to measure the voltage difference

- Then I found channel 4 is good! I did not turn the power off or do anything else.

- I repeated exactly the same procedure on channel 3 and it is repeatable.

- I left channel 1 as comparison and made attachment 2.

- Then I just use the probe of oscilliscope to connect one side of C2 on channel 1 to GND and got attachment 3, which channel 1 is good again.

I think this is a very strong hint that this whole problem is due to C2 charging up.

  1835   Wed Dec 4 19:00:37 2019 Noisemon board modifiedDailyProgress Noisemon board modifications

According to previous post 1834, we think the noisemon problem is very likely caused by C2 charging. Hence we did the following modifications on a noisemon board:

1. Split R2 into two 400 Ohm resistors, with grounding between them.

2. Split C2 into two 3.3uF capacitors, with grounding between them.

We hope these modifications will provide a path for the bias current to go to ground, instead of charging up C2.

  1836   Thu Dec 5 12:37:58 2019 Noisemon board modifiedDailyProgress Noisemon board modifications

The modification is successful. The attachment shows the result after the board runs for 12 hours. We modified channel 1 and 2 so we see FM0 and FM1 channels are still decent. We only split C2 but not R2 for channel 3 and 4 so FM2 and FM3 are bad.


According to previous post 1834, we think the noisemon problem is very likely caused by C2 charging. Hence we did the following modifications on a noisemon board:

1. Split R2 into two 400 Ohm resistors, with grounding between them.

2. Split C2 into two 3.3uF capacitors, with grounding between them.

We hope these modifications will provide a path for the bias current to go to ground, instead of charging up C2.


  1839   Mon Dec 9 22:06:19 2019 DuoDailyProgress Two boards tested

I finished testing S1900294 and S1900297 and plan to ship them to the sites.

I got stuck at a couple things. I think it is good to make a note of these stuff.

1. Diaggui gives "unable to start excitation".

Solution: restart diaggui

2. Drive signal does not go in

Solution: check the status of the digital system - it crashed and needs restart.

3. FASTIMON gives too much noise that the transfer function looks like junk.

Solution: I use 50ohm resistors to replace the coils and 500 counts noise to measure the transfer function. If the resistance is large and the input signal is small, the current will be too small.

  1840   Thu Dec 12 16:48:39 2019 DuoDailyProgress Modifying the board changes the transfer function

The noisemon board has been modified according to 1835. We do not expect any change in the transfer function but we see an increase in the gain above 20Hz.

Attachment 1 shows the comparison between modified board transfer function and the original board transfer function.

Attachment 3 shows the difference of the transfer functions in attachment 1. There is about 8-10dB increase at 100Hz after the modifications.

Attachment 4 is a comparison of LISO simulations. I calculated the transfer functions of the whole noisemon circuits before and after the modifications. I substracted them and found the difference.

Without putting attachment 3 and 4 in the same picture we can see that they are very different. LISO basically says there will not be any significant change in the transfer function but actually our measurement shows that there is.

  1841   Mon Jan 13 16:48:52 2020 DuoDailyProgress Noisemon updates

I did some documentation work these days.

- Noisemon Test Plan: https://dcc.ligo.org/LIGO-E2000007

- Updated DCC, new schematics, PCB layout and BOM (due to changes logged in 1835)

- Two more boards are modified and will be tested.

  1842   Tue Jan 14 17:07:49 2020 DuoDailyProgress Testing another two boards

I am testing another two boards to be shipped to Hanford today. I found and fixed some bad soldering. However, the frontend crashed and I needed to restart it. I could not log into cymac somehow. It says "no route to host" but the internet is still working. I cannot go on testing anymore. Let's wait and try again tomorrow.

Chris fixed the problem - I went on finishing the tests and the boards are ready to go now. They will be shipped tomorrow.

  1843   Tue Jan 21 16:13:03 2020 DuoDailyProgress Distortion of noisemon

We have sent version 2 noisemon boards (modifications from version 1 noted in 1835) to Livingston and Hanford. Chris noticed that there might be some upconversion problems under 20Hz (attachment 1 and 2). These plots from Chris are noisemon output with drive subtracted. Attachment 1 is the spectrum after replacement of noisemon board (version 2 board used), compared to attachment 2 which is before the replacement (version 1 board used). There is something going on near 15Hz. We think it might be due to upconversions under 15Hz.

We still have a spare board here. I modified it, tested it and looked at this issue, trying to reproduce. I sent a 10Hz 100 count amplitude signal to the board and compared it to the output with no input. This produces attachment 3. We see that once the 10Hz sine signal is sent, there are  lines above 10Hz, which is a sign of distortion.

I changed the input frequency to 5Hz and got attachment 4.

Attachment 5 is a linear plot to see where exactly those lines are. It seems they are indeed harmonics of 5Hz when the input signal is 5Hz.

I also tried higher frequencies up to 100Hz and saw similar harmonics.


  1847   Thu Feb 13 00:25:36 2020 DuoDailyProgress Noisemon at L1

I calculated the DAC noise for L1. Attachment 1 has all the plots and data. Attachment 2 is the result in strain.

We have noisemon at all four stations: ITMX, ITMY, ETMX, ETMY. DTT gives me the CSD, the coherences and the ASD of all the channels at all the four stations. I use this to calculate the transfer functions of the coil driver and the noisemon.

H(f) = CSD_{ab}(f)/ D^2(f)

where D(f) is the drive and CSD is the CSD between the drive and the output of noisemon. The absolute value of H(f) will be the gain of the circuit, in ADC counts / DAC counts. Then I use the coherence to calculate the total noise

N_{drive}(f)=D(f)\sqrt{1 - C_{ab}(f)}

This noise has DAC noise, ADC noise, noisemon noise in it. This noise is in DAC counts. I will call this "DriveNoise".

Then I picked another time when the interferomter is not running and the drive is zero. I measured the noisemon spectrum N(f) at that time. The plots and data of these spectrum can be found in attachment 1. The plots are considered to be a result of the noisemon noise and ADC noise, which I will call "NoDriveNoise" (in ADC cts). Since the drive is zero, there is no DAC noise in it - just ADC noise and noisemon noise. I use the transfer function to covert it to DAC counts


Then I subtract the noise drive noise from the drive noise to get the DAC noise to get the DAC noise, which is then converted to DAC volts
N_{DAC}(f) = \sqrt{N_{drive}^2(f)-N_{noDrive}^2(f)}\frac{20V}{2^{18}cts}

Then I find the current on the coil using the transfer functions of the coil driver, assuming the coil driver is in LP OFF and ACQ OFF state. The transfer function can be found in attachment 1.


where the transfer function H is a voltage-to-current transfer function.

Then we have the force

F(f)=I(f) \times 0.0309N/A

Lastly we have the displacement and strain

h(f)=\frac{F(f) (10Hz/f)^43\times10^{-8}}{4000}\sqrt{Hz}

For each station I summed all the four channels, LL, LR, UL, UR and then I calculated for all the four stations and summed as


I tried to compare this with the GWINC model - it is much higher. I do not have real L1 noise at the moment. I will see once we have real noise data.

  1883   Wed Dec 23 15:43:01 2020 PacoDailyProgress OPO cavity assembly

Laseroptik optics (4x pairs of cavity mirrors) arrived earlier this week, so I began assembling the input mirror with Noliac (NAC2124) PZT. The (15 mm OD) pzt will sit between a 1" post spacer and the mirror. I applied a thin layer of BT-120-50 (bondatherm) adhesive, which I found in EE shop. From what I gather this adhesive doesn't have softeners (almost doesn't smell) and is a good electrical insulator. The PZT + spacer is sitting below a metallic weight block on the left corner of the table (by the electronics test bench corner), and should finish hardening in a little over 24 hours at room temperature. The PZT was labeled 520 nF (spec. 510 nF).

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