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ID Date Author Type Category Subject
16078   Thu Apr 22 15:36:54 2021 AnchalUpdateSUSSettings restored

The mix up was my fault I think. I restored the channels manually instead of using burt restore. Your message suggests that we can set burt to start noticing channel changes at home point and create a .req file that can be used to restore later. We'll try to learn how to do that. Right now, we only know how to burt restore using the existing snapshots from the autoburt directory, but they touch more things than we work on, I think. Or can we just always burt restore it to morning time? If yes, what snapshot files should we use?

16079   Thu Apr 22 17:04:17 2021 gautamUpdateSUSSettings restored

Indeed, you can make your own snapshot by specifying the channels to snap in a .req file. But what I meant was, we should confirm that all the channels that we modify are already in the existing snapshot files in the autoburt dir. If it isn't, we should consider adding it. I think the whole burt system needs some cleaning up - a single day of burt snapshots occupies ~400MB (!) of disk space, but I think we're recording a ton of channels which don't exist anymore. One day...

 Quote: Your message suggests that we can set burt to start noticing channel changes at home point and create a .req file that can be used to restore later. We'll try to learn how to do that. Right now, we only know how to burt restore using the existing snapshots from the autoburt directory, but they touch more things than we work on, I think. Or can we just always burt restore it to morning time? If yes, what snapshot files should we use?
16086   Mon Apr 26 18:55:39 2021 Anchal, PacoUpdateSUSMC2 F2A Filters Tested

Today we tested the F2A filters created from the DC gain values listed in 16066.

### Filters:

• For a DC gain $G_{DC}$ required for balancing the coil at DC and $f_0$ being the resonance frequency of the mode (POS in this case), we calculate the filter using:
$\frac{1 + i \frac{f_z}{f Q} - \frac{f_z^2}{f^2}}{1 + \frac{f_0}{f} - \frac{f_0^2}{f^2}}$where $f_z = f_0 \sqrt{G_{DC}}$.
• Attachment 1 shows the motivation for choosing the resonant frequency in the formula above. It makes gain at DC as $G_{DC}$ while keeping AC gain as 1.
• Attachment 2 shows the transfer functions of the filters uploaded.
• Filters are named Eg2CtQ3, Eg2CtQ7 and Eg2CtQ10 for Q=3,7,10 filters respectively. (Named for Eigenmode Basis to Cartesian Basis conversion filters, aka F2A filters).

### Testing procedure:

• We uploaded the new input matrix listed in 16066.
• We then uploaded the coil output gains (AC gains) that are also listed in 16066.
• Then we reduced the C1:IOO-WFS_GAIN to 0.05 (by a factor of 20).
• Rana asked us to test the WFS sensors' impulse response to observe a minimum 10s decay to ensure that the UGF of WFS control loops is at or below 0.1 Hz.
• We were unable to have any effect on this decay actually. We tried setting offsets without tramps in multiple places but whenever we were able to excite this loop, it will always damp down in about 5-6s regardless of the value of C1:IOO-WFS_GAIN.
• So we moved on.
• Then, with MC locked we took reference data with no excitation or filters uploaded. (dotted curves)
• We took cross spectral density from C1:IOO-MC_F to C1:IOO-MC_TRANS_PIT_IN1, C1:IOO-MC_TRANS_YAW_IN1, C1:IOO-WFS1_PIT_IN1, C1:IOO-WFS1_PIT_IN1, C1:IOO-WFS2_PIT_IN1, and C1:IOO-WFS2_PIT_IN1.
• We were also looking at the power spectral density of these channels.
• Then using awggui (after the fix we did as in 16085), we added noise in C1:SUS-MC2_LSC_EXC as uniform noise between 0.05 Hz to 3.5 Hz with amplitude of 100 and gain of 100.
• We took a set of data without switching on the filters to have a comparison later. (Dash-dort curves)
• We then took data after switching on the filters. (Solid curves)

### Next:

• Tomorrow we'll repeat this for MC1 and MC3 if we get a favourable grade in our work here.
• Even if not, we'll jsut conclude the suspension optimization work tomorrow morning and get into main interferometer.
Attachment 1: f2a.pdf
Attachment 2: IMC_F2A_Params_MC2.pdf
Attachment 3: MC2_F2A_FilterChar_POS2Ang.pdf
16087   Tue Apr 27 10:05:28 2021 Anchal, PacoUpdateSUSMC1 and MC3 F2A Filters Tested

We extended the f2a filter implementation and diagnostics as summarized in 16086 to MC1 and MC3.

### MC1

Attachment 1 shows the filters with Q=3, 7, 10. We diagnosed using Q=3.

Attachment 2 shows the test summary, exciting with broadband noise on the LSC_EXC and measuring the CSD to estimate the transfer functions.

### MC3

Attachment 3 shows the filters with Q=3, 7, 10. We diagnosed using Q=3.

Attachment 4 shows the test summary, exciting with broadband noise on the LSC_EXC and measuring the CSD to estimate the transfer functions.

Our main observation (and difference) with respect to MC2 is the filters have relative success for the PIT cross-coupling and not so much for YAW. We already observed this when we tuned the DC output gains to compute the filters.

Attachment 1: IMC_F2A_Params_MC1.pdf
Attachment 2: MC1_POStoAng_CrossCoupling.pdf
Attachment 3: IMC_F2A_Params_MC3.pdf
Attachment 4: MC3_POStoAng_CrossCoupling.pdf
16089   Wed Apr 28 10:56:10 2021 Anchal, PacoUpdateSUSIMC Filters diagnosed

Good morning!

We ran the f2a filter test for MC1, MC2, and MC3.

Filters

The new filters differ from previous versions by a adding non-unity Q factor for the pole pairs as well.

$\frac{f^2 - i \frac{f_z}{Q}f + f_z^2}{f^2 - i \frac{f_0}{Q}f + f_0^2}$
This in terms of zpk is: [ [zr + i zi, zr - i zi], [pr + i pi, pr - i pi], 1] where
$z_r = -\frac{f_z}{2Q}, \quad z_i = f_z \sqrt{1 - \frac{1}{4Q^2}}, \quad p_r = -\frac{f_0}{2Q}, \quad p_i = f_0 \sqrt{1 - \frac{1}{4Q^2}}$$, \quad f_z = f_0 \sqrt{G_{DC}}$

• Attachment #1 shows the filters for MC1 evaluated for Q=3, 7,and 10.
• Attachment #2 shows the filters for MC2 evaluated for Q=3, 7, and 10.
• Attachment #3 shows the filters for MC3 evaluated for Q=3, 7, and 10.
• Attachment #4 shows the bode plots generated by foton after uploading for Q=3 case.

We uploaded all these filters using foton, into the three last FM slots on the POS output gain coil.

Tests

We ran tests on all suspended optics using the following (nominal) procedure:

2. Lower the C1:IOO-WFS_GAIN to 0.05.
3. Upload AC coil balancing gains.
4. Take ASD for the following channels:
• C1:IOO-MC_TRANS_PIT_IN1
• C1:IOO-MC_TRANS_YAW_IN1
• C1:IOO-MC_WFS1_PIT_IN1
• C1:IOO-MC_WFS1_YAW_IN1
• C1:IOO-MC_WFS2_PIT_IN1
• C1:IOO-MC_WFS2_YAW_IN1
5. For the following combinations:
• No excitation** + no filter
• No excitation + filter
• Excitation + no filter
• Excitation + filter

** Excitation = 0.05 - 3.5 Hz uniform noise, 100 amplitude, 100 gain

### Plots

• Attachment 5-7 give the test results for MC1, MC2 and MC3.
• In each pdf, the three pages show ASD of TRANS QPD, WFS1 and WFS2 channels' PIT and YAW, respectively.
• Red/blue correspond to data taken while F2A filters were on. Pink/Cyan correspond to data taken with filters off.
• Solid curves were taken with excitation ON and dashed curves were taken with excitation off.
• We see good suppression of POS-> PIT coupling in MC2 and MC3. POS->YAw is minimally affected in all cases.
• MC1 is clearly not doing good with the filters and probably needs readjustement. Something to do later in the future.
Attachment 1: IMC_F2A_Params_MC1.pdf
Attachment 2: IMC_F2A_Params_MC2.pdf
Attachment 3: IMC_F2A_Params_MC3.pdf
Attachment 4: IMC_F2A_Foton.pdf
Attachment 5: MC1_POS2ANG_Filter_Test.pdf
Attachment 6: MC2_POS2ANG_Filter_Test.pdf
Attachment 7: MC3_POS2ANG_Filter_Test.pdf
16091   Wed Apr 28 17:09:11 2021 AnchalUpdateSUSTuned Suspension Parameters uploaded for long term behavior monitoring

I have uploaded all the new settings mentioned in 16066 and 16072. The settings were uploaded through a single script present at anchal/20210428_IMC_Tuned_Suspension/uploadNewConfigIMC.py. The settings can be reverted back to old settings through anchal/20210428_IMC_Tuned_Suspension/restoreOldConfigIMC.py. Both these scripts can be run only through python3 in donatella or allegra.

GPSTIME of new settings: 1303690144

New settings include:

• New input matrices for MC1 and MC2.
• New Output coil gains for AC balancing on all three optics.
• Switching ON the FM8 filter modulae (Q=3 F2A filter) in POS column on output matrix of all optics.

We'll wait and watch the performance through summary pages and check back the performance on Monday.

16094   Thu Apr 29 10:52:56 2021 AnchalUpdateSUSIMC Trans QPD and WFS loops step response test

In 16087 we mentioned that we were unable to do a step response test for WFS loop to get an estimate of their UGF. The primary issue there was that we were not putting the step at the right place. It should go into the actuator directly, in this case, on C1:SUS-MC2_PIT_COMM and C1:SUS-MC2_YAW_COMM. These channels directly set an offset in the control loop and we can see how the error signals first jump up and then decay back to zero. The 'half-time' of this decay would be the inverse of the estimated UGF of the loop. For this test, the overall WFS loops gain,  C1:IOO-WFS_GAIN was set to full value 1. This test is performed in the changed settings uploaded in 16091.

I did this test twice, once giving a step in PIT and once in YAW.

Attachment 1 is the striptool screenshot for when PIT was given a step up and then step down by 0.01.

• Here we can see that the half-time is roughly 10s for TRANS_PIT and WFS1_PIT corresponding to roughly 0.1 Hz UGF.
• Note that WFS2 channels were not disturbed significantly.
• You can also notice that third most significant disturbance was to TRANS_YAW actually followed by WF1 YAW.

Attachment 2 is the striptool screenshot when YAW was given a step up and down by 0.01. Note the difference in x-scale in this plot.

• Here, TRANS YAW got there greatest hit and it took it around 2 minutes to decay to half value. This gives UGF estimate of about 10 mHz!
• Then, weirdly, TRANS PIT first went slowly up for about a minutes and then slowly came dome in a half time of 2 minutes again. Why was PIT signal so much disturbed by the YAW offset in the first place?
• Next, WFS1 YAW can be seen decaying relatively fast with half-life of about 20s or so.
• Nothing else was disturbed much.

• So maybe we never needed to reduce WFS gain in our measurement in 16089 as the UGF everywhere were already very low.
• What other interesting things can we infer from this?
• Should I sometime repeat this test with steps given to MC1 or MC3 optics?
Attachment 1: PIT_OFFSET_ON_MC2.png
Attachment 2: YAW_STEP_ON_MC2_complete.png
16102   Thu Apr 29 18:53:33 2021 AnchalUpdateSUSIMC Suspension Damping Gains Test

With the input matrix, coil ouput gains and F2A filters loaded as in 16091, I tested the suspension loops' step response to offsets in LSC, ASCPIT and ASCYAW channels, before and after applying the "new damping gains" mentioned in 16066 and 16072. If these look better, we should upload the new (higher) damping gains as well. This was not done in 16091.

Note that in the plots, I have added offsets in the different channels to plot them together, hence the units are "au".

Attachment 1: MC1_SUSDampGainTest.pdf
Attachment 2: MC2_SUSDampGainTest.pdf
Attachment 3: MC3_SUSDampGainTest.pdf
16110   Mon May 3 16:24:14 2021 AnchalUpdateSUSIMC Suspension Damping Gains Test Repeated with IMC unlocked

We repeated the same test with IMC unlocked. We had found these gains when IMC was unlocked and their characterization needs to be done with no light in the cavity. attached are the results. Everything else is same as before.

 Quote: With the input matrix, coil ouput gains and F2A filters loaded as in 16091, I tested the suspension loops' step response to offsets in LSC, ASCPIT and ASCYAW channels, before and after applying the "new damping gains" mentioned in 16066 and 16072. If these look better, we should upload the new (higher) damping gains as well. This was not done in 16091. Note that in the plots, I have added offsets in the different channels to plot them together, hence the units are "au".

Edit Tue May 4 14:43:48 2021 :

• Adding zoomed in plots to show first 25s after the step.
• MC1:
• Our improvements by new gains are only modest.
• This optic needs a more careful coil balancing first.
• Still the ring time is reduced to about 5s for all step responses as opposed to 10s at old gains.
• MC2:
• The first page of MC2 might be bit misleading. We have not changed the damping gain for SUSPOS channel, so the longer ringing is probably just an artifact of somthing else. We didn't retake data.
• In PIT and YAW where we increased the gain by a factor of 3, we see a reduction in ringing lifetime by about half.
• MC3:
• We saw the most optimistic improvement on this optic.
• The gains were unusually low in this optic, not sure why.
• By increasing SUSPOS gain from 200 to 500, we saw a reduction of ringing halftime from 7-8s to about 2s. Improvements are seen in other DOFs as well.
• You can notice rightaway that YAW of MC3 keeps oscillating near resonance (about 1 Hz). Maybe more careful feedback shaping is required here.
• In SUSPIT, we increased gain from 12 to 35 and saw a good reduction in both ringing time and initial amplitude of ringing.
• In SUSYAW, we only increased the gain to 12 from 8, which still helped a lot in reducing big ringing step response to below 5s from about 12s.

Overall, I would recommend setting the new gains in the suspension loops as well to observe long term effects too.

Attachment 1: MC1_SusDampGainTest.pdf
Attachment 2: MC2_SusDampGainTest.pdf
Attachment 3: MC3_SusDampGainTest.pdf
16120   Wed May 5 09:04:47 2021 AnchalUpdateSUSNew IMC Suspension Damping Gains uploaded for long term testing

We have uploaded the new damping gains on all the suspensions of IMC. This completes changing all the configuration to as mentioned in 16066 and 16072. The old setting can be restored by running python3 /users/anchal/20210505_IMC_Tuned_SUS_with_Gains/restoreOldConfigIMC.py from allegra or donatella.

GPSTIME: 1304265872

 UTC May 05, 2021 16:04:14 UTC Central May 05, 2021 11:04:14 CDT Pacific May 05, 2021 09:04:14 PDT

16133   Wed May 12 11:45:13 2021 Anchal, PacoSummarySUSNew IMC Settings are miserable

We picked a few parameters from 40m summary page and plotted them to see the effect of new settings. On April 4th, old settings were present. On April 28th (16091), new input matrices and F2A filters were uploaded but suspension gains remained the same. On May 5th (16120), we uploaded new (higher) suspension gains. We chose Sundays on UTC so that it lies on weekends for us. Most probably nobody entered 40m and it was calmer in the institute as well.

• On MC_F spectrum, we see that that noise decreased in 0.3-0.7 Hz but there is more noise from 1-1.5 Hz.
• On MC_TRANS_QPD, we see that both TRANS PIT and YAW signals were almost twice as noisy.
• On MC_REFL_DC too, we see that the noise during the locked state seems to be higher in the new configuration.

We can download data and plot comparisons ourselves and maybe calculate the spectrums of MC_TRANS_PIT/YAW and MC_REFL_DC when IMC was locked. But we want to know if anyone has better ways of characterizing the settings that we should know of before we get into this large data handling which might be time-consuming. From this preliminary 40m summary page plots, maybe it is already clear that we should go back to old settings. Awaiting orders.

Attachment 1: MC_F_Comparison.pdf
Attachment 2: MC_TRANS_QPD_Comparison.pdf
Attachment 3: IMC_REFL_DC_Comparison.pdf
16135   Wed May 12 14:23:20 2021 JordanUpdateSUSMass Properties of SOS Assembly with 3"->2" Optic sleeve, in SI units
Attachment 1: Moments_of_Inertia_SI.PNG
16136   Wed May 12 16:53:59 2021 KojiUpdateSUSMass Properties of SOS Assembly with 3"->2" Optic sleeve, in SI units

No, this is the property of the suspension assembly. The mass says 10kg

Could you do the same for the testmass assembly (only the suspended part)? The units are good, but I expect that the values will be small. I want to keep at least three significant digits.

16137   Wed May 12 17:06:52 2021 JordanUpdateSUSMass Properties of SOS Assembly with 3"->2" Optic sleeve, in SI units

Here are the mass properties for the only the test mass assembly (optic, 3" ring, and wire block). (Updated with g*mm^2)

 Quote: No, this is the property of the suspension assembly. The mass says 10kg Could you do the same for the testmass assembly (only the suspended part)? The units are good, but I expect that the values will be small. I want to keep at least three significant digits.

Attachment 1: Moments_of_Inertia_SI.PNG
16138   Thu May 13 11:55:04 2021 Anchal, PacoUpdateSUSMC1 suspension misbehaving

We came in the morning with the following scene on the zita monitor:

The MC1 watchdog was tripped and seemed like IMC struggled all night with misconfigured WFS offsets. After restoring the MC1 WD, clearing the WFS offsets, and seeing the suspension damp, the MC caught lock. It wasn't long before the MC unlocked, and the MC1 WD tripped again.

We tried few things, not sure what order we tried them in:

• Letting suspension loops damp without the WFS switched on.
• Letting suspension loops damp with PSL shutter closed.
• Restoring old settings of MC suspension.
• Doing burt restore with command:
burtwb -f /opt/rtcds/caltech/c1/burt/autoburt/snapshots/2021/May/12/08:19/c1mcsepics.snap -l /tmp/controls_1210513_083437_0.write.log -o /tmp/controls_1210513_083437_0.nowrite.snap -v <

Nothing worked. We kept seeing that ULPD var on MC1 keeps showing kicks every few minutes which jolts the suspension loops. So we decided to record some data with PSL shutter closed and just suspension loops on. Then we switched off the loops and recorded some data with freely swinging optic. Even when optic was freely swinging, we could see impulses in the MC1 OSEM UL PD var which were completely uncorrelated with any seismic activity. Infact, last night was one fo teh calmer nights seismically speaking. See attachment 2 for the time series of OSEM PD variance. Red region is when the coil outputs were disabled.

### Inference:

• We think something is wrong with the UL OSEM of MC1.
• It seems to show false spikes of motion when there is no such spike present in any other OSEM PD or the seismic data itself.
• Currently, this is still the case. We sometimes get 10-20 min of "Good behavior" when everything works.
• But then the impulses start occuring again and overwhelmes the suspension loops and WFS loops.
• Note, that other optic in IMC behaved perfectly normally throughout this time.
• In the past, it seems like satellite box has been the culprit for such glitches.
• We should look into debugging this as ifo is at standstill because of this issue.
• Earlier, Gautum would post Vmon signals of coil outputs only to show the glitches. We wanted to see if switching off the loops help, so we recorded OSEM PD this time.
• In hindsight, we should probably look at the OSEM sensor outputs directly too rather than looking at the variance data only. I can do this if people are interested in looking at that too.
• We've disabled the coil ouputs in MC1 and PSL shutter is off.

Edit Thu May 13 14:47:25 2021 :

Added OSEM Sensor timeseries data on the plots as well. The UL OSEM sensor data is the only channel which is jumping hapazardly (even during free swinging time) and varying by +/- 30. Other sensors only show some noise around a stable position as should be the case for a freely suspended optic.

Attachment 2: MC1_Glitches_Invest2.pdf
16139   Thu May 13 19:38:54 2021 AnchalUpdateSUSMC1 Satellite Amplifier Debugged

[Anchal Koji]

Koji and I did a few tests with an OSEM emulator on the satellite amplifier box used for MC1 which is housed on 1X4. This sat box unit is S2100029 D1002812 that was recently characterized by me 15803. We found that the differential output driver chip AD8672ARZ U2A section for the UL PD was not working properly and had a fluctuating offset at no input current from the PD. This was the cause of the ordeal of the morning. The chip was replaced with a new one from our stock. The preliminary test with the OSEM emulator showed that the channel has the correct DC value.

In further testing of the board, we found that the channel 8 LED driver was not working properly. Although this channel is never used in our current cable convention, it might be used later in the future. In the quest of debugging the issue there, we replaced AD8672ARZ at U1 on channel 8. This did not solve the issue. So we opened the front panel and as we flipped the board, we found that the solder blob shorted the legs of the transistor Q1 2N3904. This was replaced and the test with the LED out and GND shorted indicated that the channel is now properly providing a constant current of 35mA (5V at the monitor out).

After the debugging, the UL channel became the least noisy among the OSEM channels! Mode cleaner was able to lock and maintain it.

We should redo the MC1 input matrix optimization and the coil balancing afterward as we did everything based on the noisy UL OSEM values.

Attachment 1: MC1_UL_Channel_Fixed.png
16143   Sat May 15 14:54:24 2021 gautamUpdateSUSIMC settings reverted

I want to work on the IFO this weekend, so I reverted the IMC suspension settings just now to what I know work (until the new settings are shown quantitatively to be superior). There isn't any instruction here on how to upload the new settings, so after my work, I will just restore from a burt-snapshot from before I changed settings.

In the process, I found something odd in the MC2 coil output filter banks. Attachment #1 shows what it it is today. This weird undetermined state of FM9 isn't great - I guess this flew under the radar because there isn't really any POS actuation on MC2. Where did the gain1 filter I installed go? Some foton filter file corruption? Eventually, we should migrate FM7,FM8-->FM9,FM10 but this isn't on my scope of things to do for today so I am just putting the gain1 filter back so as to have a clean FM9 switched on.

 Quote: The old setting can be restored by running python3 /users/anchal/20210505_IMC_Tuned_SUS_with_Gains/restoreOldConfigIMC.py from allegra or donatella.

I wrote the values from the c1mcs burt snapshot from ~1400 Saturday May 15, at ~1600 Sunday May 16. I believe this undoes all my changes to the IMC suspension settings.

Attachment 1: MC2coilOut.png
16146   Wed May 19 18:29:41 2021 KojiUpdateSUSMass Properties of SOS Assembly with 3"->2" Optic sleeve, in SI units

Calculation for the SOS POS/PIT/YAW resonant frequencies

- Nominal height gap between the CoM and the wire clamping point is 0.9mm (cf T970135)

- To have the similar res freq for the optic with the 3" metal sleeve is 1.0~1.1mm.
As the previous elog does not specify this number for the current configuration, we need to asses this value and the make the adjustment of the CoM height.

Attachment 1: SOS_resonant_freq.pdf
Attachment 2: SOS_resonant_freq.nb.zip
16147   Thu May 20 10:35:57 2021 AnchalUpdateSUSIMC settings reverted

For future reference, the new settings can be upoaded from a script in the same directory. Run python /users/anchal/20210505_IMC_Tuned_SUS_with_Gains/uploadNewConfigIMC.py from allegra.

 Quote: There isn't any instruction here on how to upload the new settings
16149   Fri May 21 00:05:45 2021 KojiUpdateSUSNew electronics: Sat Amp / Coil Drivers

11 new Satellite Amps were picked up from Downs. 7 more are coming from there. I have one spare unit I made. 1 sat amp has already been used at MC1.

We had 8 HAM-A coil drivers delivered from the assembling company. We also have two coil drivers delivered from Downs (Anchal tested)

Attachment 1: F3CDEF8D-4B1E-42CF-8EFC-EA1278C128EB_1_105_c.jpeg
16157   Mon May 24 19:14:15 2021 Anchal, PacoSummarySUSMC1 Free Swing Test set to trigger

We've set a free swing test to trigger at 3:30 am tomorrow for MC1. The script for tests is running on tmux session named 'freeSwingMC1' on rossa. The script will run for about 4.5 hrs and we'll correct the input matrix tomorrow from the results. If anyone wants to work during this time (3:30 am to 8:00 am), you can just kill the script by killing tmux session on rossa. ssh into rossa and type tmux kill-session -t freeSwingMC1.

 Quote: We should redo the MC1 input matrix optimization and the coil balancing afterward as we did everything based on the noisy UL OSEM values.

16159   Tue May 25 10:22:16 2021 Anchal, PacoSummarySUSMC1 new input matrix calculated and uploaded

The test was succesful and brought back the IMC to lock point at the end.

We calculated new input matrix using same code in scripts/SUS/InMatCalc/sus_diagonalization.py . Attachment 1 shows the results.

The calculations are present in scripts/SUS/InMatCalc/MC1.

We uploaded the new MC1 input matrix at:

Unix Time = 1621963200

 UTC May 25, 2021 17:20:00 UTC Central May 25, 2021 12:20:00 CDT Pacific May 25, 2021 10:20:00 PDT

GPS Time = 1305998418

This was done by running python scripts/SUS/general/20210525_NewMC1Settings/uploadNewConfigIMC.py on allegra. Old IMC settings (before Paco and I started workin on 40m) can be restored by running python scripts/SUS/general/20210525_NewMC1Settings/restoreOldConfigIMC.py on allegra.

Everything looks as stable as before. We'll look into long term trends in a week to see if this helped at all.

Attachment 1: SUS_Input_Matrix_Diagonalization.pdf
16165   Thu May 27 14:11:15 2021 JordanUpdateSUSCoM to Clamping Point Measurement for 3" Adapter Ring

The current vertical distance between the CoM and the wire clamping point on the 3" Ring assembly is 0.33mm. That is the CoM is .33 mm below the clamping point of the wire. I took the clamping point to be the top edge of the wire clamp piece. see the below attachments.

I am now modifying the dumbell mechanism at the bottom of the ring to move the CoM to the target distance of 1.1mm.

Attachment 1: CoM_to_Clamp.PNG
Attachment 2: CoM_to_Clamp_2.PNG
16169   Tue Jun 1 14:26:23 2021 JordanUpdateSUSCoM to Clamping Point Measurement for 3" Adapter Ring

After changing the material of the Balance Mass from 6061 Al to 304 Steel, and changing the thickness to 0.21" from 0.25". The CoM is now 1.11mm below the clamping point.

Koji expected a mass change of ~ 4g to move the mass to 1.1mm. The 6061 mass weighed ~1.31g and the 304 mass weighs 4.1g.

A potential issue with this is the screw used the adjust the position of these balance masses, threads through both the aluminum ring and this now 304 steel mass. A non silver plated screw could cold weld at the mass, but a silver plated screw will gall in the aluminum threads.

 Quote: The current vertical distance between the CoM and the wire clamping point on the 3" Ring assembly is 0.33mm. That is the CoM is .33 mm below the clamping point of the wire. I took the clamping point to be the top edge of the wire clamp piece. see the below attachments. I am now modifying the dumbell mechanism at the bottom of the ring to move the CoM to the target distance of 1.1mm.

Attachment 1: CoM_to_Clamp_Updated.PNG
16173   Wed Jun 2 01:08:57 2021 KojiUpdateSUSCoM to Clamping Point Measurement for 3" Adapter Ring

How about to use the non-Ag coated threaded shaft + the end SS masses with helicoils inserted? Does this save the masses to get stuck?

16174   Wed Jun 2 09:43:30 2021 Anchal, PacoSummarySUSIMC Settings characterization

## Plot description:

• We picked up three 10 min times belonging to the three different configurations:
• 'Old Settings': IMC Suspension settings before Paco and I changed anything. Data taken from Apr 26, 2021, 00:30:42 PDT (GPS 1303457460).
• 'New Settings': New input matrices uploaded on April 28th, along with F2A filters and AC coil balancing gains (see 16091). Data taken from May 01, 2021, 00:30:42 PDT (GPS 1303889460).
• 'New settings with new gains' Above and new suspension damping gains uploaded on May5th, 2021 (see 16120). Data taken from May 07, 2021, 03:10:42 PDT (GPS 1304417460).
• Attachment 1  shows the RMS seismic noise along X direction between 1 Hz and 3 Hz picked from C1:PEM-RMS_BS_X_1_3 during the three time durations chosen. This plot is to establish that RMS noise levels were similar and mostly constant. Page 2 shows the mean ampltidue spectral density of seismic noise in x-direction over the 3 durations.
• Attachment 2 shows the transfer function estimate of seismic noise to MC_F during the three durations. Page 1 shows ratio of ASDs taken with median averaging while page 2 shows the same for mean averaging.
• Attachment 3 shows the transfer function estimate of seismic noise to MC_TRANS_PIT during the three durations. Page 1 shows ratio of ASDs taken with median averaging while page 2 shows the same for mean averaging.
• Attachment 4 shows the transfer function estimate of seismic noise to MC_TRANS_YAW during the three durations. Page 1 shows ratio of ASDs taken with median averaging while page 2 shows the same for mean averaging.

## Inferences:

• From Attachment 2 Page 1:
• We see that 'old settings' caused the least coupling of seismic noise to MC_F signal in most of the low frequency band except between 1.5 to 3 Hz where the 'new settings' were slightly better.
• 'new settings' also show less coupling in 4 Hz to 6 Hz band, but at these frequencies, seismix noise is filtered out by suspension, so this could be just coincidental and is not really a sign of better configuration.
• There is excess noise coupling seen with 'new settings' between 0.4 Hz and 1.5 Hz. We're not sure why this coupling increased.
• 'new settings with new gains' show the most coupling in most of the frequency band. Clearly, the increased suspension damping gains did not behaved well with rest of the system.
• From Attachment 3 Page 1:
• Coupling to MC_TRANS_PIT error signal is reduced for 'new settings' in almost all of the frequency band in comparison to the 'old settings'.
• 'new settings with new gains' did even better below 1 Hz but had excess noise in 1 Hz to 6 Hz band. Again increased suspension damping gains did not help much.
• But low coupling to PIT error for 'new settings' suggest that our decoupling efforts in matrix diagonalization, F2A filters and ac coil balancing worked to some extent.
• From Attachment 4 Page 1:
• 'new settings' and 'old settings' have the same coupling of seismic noise to MC_TRANS_YAW in all of the frequency band. This is in-line witht eh fact that we found very little POS to YAW couping in our analysis before and there was little to no change for these settings.
• 'new settings with new gains' did better below 1 Hz but here too there was excess coupling between 1 Hz to 9 Hz.
• Page 1 vs Page 2:
• Mean and median should be same if the data sample was large enough and noise was stationary. A difference between the two suggests existence of outliers in the data set and median provides a better central estimate in such case.
• MC_F: Mean and median are same below 4 hz. There are high frequency outliers above 4 Hz in 'new settings with new gains' and 'old settings' data sets, maybe due to transient higher free running laser frequency noise. But since, suspension settigns affect below 1 Hz mostly, the data sets chosen are stationary enough for us.
• MC_TRANS_PIT: Mean ratio is lower for 'new settings' and 'old settings' in 0.3 hz to 0.8 Hz band. Same case above 4 Hz as listed above.
• MC_TRANS_YAW:  Same as above.
• Conclusion 1:  The 'new settings with new gains' cause more coupling to seismic noise, probably due to low phase margin in control loops. We should revert back the suspension damping gains.
• Conclusion 2: The 'new settings' work as expected and can be kept when WFS loops are optimized further.
• Conjecture: From our experience over last 2 weeks, locking the arms to the main laser with 'new settings with new gains' introduces noise in the arm length large enough that the Xend green laser does not remain locked to the arm for longer than tens of seconds. So this is definitely not a configuration in which we can carry out other measurements and experiments in the interferometer.
Attachment 1: seismicX.pdf
Attachment 2: seismicXtoMC_F_TFest.pdf
Attachment 3: seismicXtoMC_TRANS_PIT_TFest.pdf
Attachment 4: seismicXtoMC_TRANS_YAW_TFest.pdf
16175   Wed Jun 2 16:20:59 2021 Anchal, PacoSummarySUSIMC Suspension gains reverted to old values

Following the conclusion, we are reverting the suspension gains to old values, i.e.

IMC Suspension Gains
MC1 MC2 MC3
SUSPOS 120 150 200
SUSPIT 60 10 12
SUSYAW 60 10 8

While the F2A filters, AC coil gains and input matrices are changed to as mentioned in 16066 and 16072.

The changes can be reverted all the way back to old settings (before Paco and I changed anything in the IMC suspensions) by running python scripts/SUS/general/20210602_NewIMCOldGains/restoreOldConfigIMC.py on allegra. The new settings can be uploaded back by running python scripts/SUS/general/20210602_NewIMCOldGains/uploadNewConfigIMC.py on allegra.

Change time:

Unix Time = 1622676038

 UTC Jun 02, 2021 23:20:38 UTC Central Jun 02, 2021 18:20:38 CDT Pacific Jun 02, 2021 16:20:38 PDT

GPS Time = 1306711256

 Quote: Conclusion 1:  The 'new settings with new gains' cause more coupling to seismic noise, probably due to low phase margin in control loops. We should revert back the suspension damping gains. Conclusion 2: The 'new settings' work as expected and can be kept when WFS loops are optimized further. Conjecture: From our experience over last 2 weeks, locking the arms to the main laser with 'new settings with new gains' introduces noise in the arm length large enough that the Xend green laser does not remain locked to the arm for longer than tens of seconds. So this is definitely not a configuration in which we can carry out other measurements and experiments in the interferometer.

16209   Thu Jun 17 11:45:42 2021 Anchal, PacoUpdateSUSMC1 Gave trouble again

TL;DR

MC1 LL Sensor showed signs of fluctuating large offsets. We tried to find the issue in the box but couldn't find any. On power cycling, the sensor got back to normal. But in putting back the box, we bumped something and c1susaux slow channels froze. We tried to reboot it, but it didn't work and the channels do not exist anymore.

Today morning we came to find that IMC struggled to lock all night (See attachment 1). We kind of had an indication yesterday evening that MC1 LL Sensor PD had a higher variance than usual and Paco had to reset WFS offsets because they had integrated the noise from this sensor. Something similar happened last night, that a false offset and its fluctuation overwhelmed WFS and MC1 got misaligned making it impossible for IMC to get lock.

In the morning, Paco again reset the WFS offsets but not we were sure that the PD variance from MC1 LL osem was very high. See attachment 2 to see how only 1 OSEM is showing higher noise in comparison to the other 4 OSEMs. This behavior is similar to what we saw earlier in 16138 but for UL sensor. Koji and I fixed it in 16139 and we tested all other channels too.

So, Paco and I, went ahead and took out the MC1 satellite amplifier box S2100029 D1002812, opened the top, and checked all the PD channel testpoints with no input current. We didn't find anything odd. Next we checked the LED dirver circuit testpoints with LED OUT and GND shorted. We got 4.997V on all LED MON testpoints which indicate normal functioning.

We just hooked back everything on the MC1 satellit box and checked the sensor channels again on medm screens. To our surprise, it started functioning normally. So maybe, just a power cycling was required but we still don't know what caused this issue.

BUT when I (Anchal) was plugging back the power cables and D25 connectors on the back side in 1X4 after moving the box back into the rack, we found that the slow channels stopped updating. They just froze!

We got worried for some time as the negative power supply indicator LEDs on the acromag chassis (which is just below the MC1 satellite box) were not ON. We checked the power cables and had to open the side panel of the 1X4 rack to check how the power cables are connected. We found that there is no third wire in the power cables and the acromag chassis only takes in single rail supply. We confirmed this by looking at another acromag chassis on Xend. We pasted a note on the acromag chassis for future reference that it uses only positive rails and negative LED monitors are not usually ON.

Back to solving the frozen acromag issue, we conjectured that maybe the ethernet connection is broken. The DB25 cables for the satellite box are bit short and pull around other cables with it when connected. We checked all the ethernet cabling, it looked fine. On c1susaux computer, we saw that the monitor LED for ethernet port 2 which is connected to acromag chassis is solid ON while the other one (which is probably connection to the switch) is blinking.

We tried doing telnet to the computer, it didn't work. The host refused connection from pianosa workstation. We tried pinging the c1susaux computer, and that worked. So we concluded that most probably, the epics modbus server hosting the slow channels on c1susaux is unable to communicate with acromag chassis and hence the solid LED light on that ethernet port instead of a blinking one. We checked computer restart procedure page for SLOW computers on wiki and found that it said if telnet is not working, we can hard reboot the computer.

We hard reboot the computer by long pressing the power button and then presssing it back on. We did this process 3 times with the same result. The ethernet port 2 LED (Acromag chassis) would blink but the ethernet port 1 LED (connected to switch) would not turn ON. We now can not even ping the machine now, let alone telnet into it. All SUS slow monitor channels are not present now ofcourse. We also tried once pressing the reset button (which the manual said would reboot the machine), but we got the same outcome.

Now, we decided to stop poking around until someone with more experience can help us on this.

Bottomline: We don't know what caused the LL sensor issue and hence it has not been fixed. It can happen again. We lost all C1SUSAUX slow channels which are the OSEM and COIL slow monitor channels for PRM, BS, ITMX, ITMY, MC1, MC2 and MC3.

Attachment 1: SummaryScreenShot.png
16210   Thu Jun 17 16:37:23 2021 Anchal, PacoUpdateSUSc1susaux computer rebooted

Jon suggested to reboot the acromag chassis, then the computer, and we did this without success. Then, Koji suggested we try running ifup eth0, so we ran sudo /sbin/ifup eth0 and it worked to put c1susaux back in the martian network, but the modbus service was still down. We switched off the chassis and rebooted the computer and we had to do sudo /sbin/ifup eth0 again (why do we need to do this manually everytime?). Switched on the chassis but still no channels. sudo systemctl status modbusioc.service' gave us inactive (dead) status. So  we ran sudo systemctl restart modbusioc.service'.

The status became:

● modbusIOC.service - ModbusIOC Service via procServ
start condition failed at Thu 2021-06-17 16:10:42 PDT; 12min ago
ConditionPathExists=/opt/rtcds/caltech/c1/burt/autoburt/latest/c1susaux.snap was not met

After another iteration we finally got a modbusIOC.service OK status, and we then repeated Jon's reboot procedure. This time, the acromags were on but reading 0.0, so we just needed to run sudo /sbin/ifup eth1and finally some sweet slow channels were read. As a final step we burt restored to 05:19 AM today c1susaux.snap file and managed to relock the IMC >> will keep an eye on it.... Finally, in the process of damping all the suspended optics, we noticed some OSEM channels on BS and PRM are reading 0.0 (they are red as we browse them)... We succeeded in locking both arms, but this remains an unknown for us.

16212   Thu Jun 17 22:25:38 2021 KojiUpdateSUSNew electronics: Sat Amp / Coil Drivers

It is a belated report: We received 5 more sat amps on June 4th. (I said 7 more but it was 6 more) So we still have one more sat amp coming from Todd.

- 1 already delivered long ago
- 8 received from Todd -> DeLeone -> Chub. They are in the lab.
- 11 units on May 21st
- 5 units on Jun 4th
Total 1+8+11+5 = 25
1 more unit is coming

 Quote: 11 new Satellite Amps were picked up from Downs. 7 more are coming from there. I have one spare unit I made. 1 sat amp has already been used at MC1. We had 8 HAM-A coil drivers delivered from the assembling company. We also have two coil drivers delivered from Downs (Anchal tested)

Attachment 1: P_20210604_231028.jpeg

We checked back in time to see how the BS and PRM OSEM slow channels are zero. It was clear that they became zero when we worked on this issue on June 17th, Thursday. So we simply went back and power cycled the c1susaux acromag chassis. After that, we had to log in to c1susaux computer and run

sudo /sbin/ifdown eth1
sudo /sbin/ifup eth1

This restarted the ethernet port acromag chassis is connected to. This solved this issue and we were able to see all the slow channels in BS and PRM.

But then, we noticed that the OPLEV of ITMX is unable to read the position of the beam on the QPD at all. No light was reaching the QPD. We went in, opened the ITMX table cover and confirmed that the return OPLEV beam is way off and is not even hitting one of the steering mirrors that brings it to the QPD. We switched off the OPLEV contribution to the damping.

We did burt restore to 16th June morning using
burtwb -f /opt/rtcds/caltech/c1/burt/autoburt/snapshots/2021/Jun/16/06:19/c1susaux.snap -l /tmp/controls_1210622_095432_0.write.log -o /tmp/controls_1210622_095432_0.nowrite.snap -v

This did not solve the issue.

Then we noticed that the OSEM signals from ITMX were saturated in opposite directions for Left and Right OSEMs. The Left OSEM fast channels are saturated to 1.918 um for UL and 1.399 um for LL, while both right OSEM channels are bottomed to 0 um. On the other hand, the acromag slow PD monitors are showing 0 on the right channels but 1097 cts on UL PDMon and 802 cts in LL PD Mon. We actually went in and checked the DC voltages from the PD input monitor LEMO ports on the ITMX dewhitening board D000210-A1 and measured non-zero voltages across all the channels. Following is a summary:

C1-SUS-ITMX_XXSEN_OUT
C1-SUS-ITMX_xxPDMon
(Slow Acromag Monitors) (cts)
Multimeter measurements at input to Dewhitening Boards
(V)
UL 1.918 1097 0.901
LL 1.399 802 0.998
UR 0 0 0.856
LR 0 0 0.792
SD 0.035 20 0.883

We even took out the 4-pin LEMO outputs from the dewhitening boards that go to the anti-aliasing chassis and checked the voltages. They are same as the input voltages as expected. So the dewhitening board is doing its job fine and the OSEMs are doing their jobs fine.

It is weird that both the ADC and the acromags are reading these values wrong. We believe this is causing a big yaw offset in the ITMX control signal causing the ITMX to turn enough make OPLEV go out of range. We checked the CDS FE status (attachment 1). Other than c1rfm showing a yellow bar (bit 2 = GE FANUC RFM card 0) in RT Net Status, nothing else seems wrong in c1sus computer. c1sus FE model is running fine. c1x02 (the lower level model) does show a red bar in TIM which suggests some timing issue. This is present in c1x04 too.

### Bottomline:

Currently, the ITMX coil outputs are disabled as we can't trust the OSEM channels. We're investigating more why any of this is happening. Any input is welcome.

Attachment 1: CDS_FE_Status.png

After sliding the alignment bias around and browsing through elog while searching for "stuck" we concluded the ITMX osems needed to be freed. To do this, the procedure is to slide the alignment bias back and forth ("shaking") and then as the OSEMs start to vary, enable the damping. We did just this, and then restored the alignment bias sliders slowly into their original positions. Attachment 1 shows the ITMX OSEM sensor input monitors throughout this procedure.

At the end, since MC has trouble catching lock after opening PSL shutter, I tried running burt restore the ioo to 2021/Jun/17/06:19/c1iooepics.snap but the problem persists

Attachment 1: shake_and_damp.png
16222   Wed Jun 23 09:05:02 2021 AnchalUpdateSUSMC lock acquired back again

MC was unable to acquire lock because the WFS offsets were cleared to zero at some point and because of that MC was very misaligned to be able to catch back lock. In such cases, one wants the WFS to start accumulating offsets as soon as minimal lock is attained so that the mode cleaner can be automatically aligned. So I did following that worked:

• Made the C1:IOO-WFS_TRIG_WAIT_TIME (delay in WFS trigger) from 3s to 0s.
• Reduced C1:IOO-WFS_TRIGGER_THRESH_ON (Switchin on threshold) from 5000 to 1000.
• Then as soon as a TEM00 was locked with poor efficiency, the WFS loops started aligning the optics to bring it back to lock.
• After robust lock has been acquired, I restored the two settings I changed above.
 Quote: At the end, since MC has trouble catching lock after opening PSL shutter, I tried running burt restore the ioo to 2021/Jun/17/06:19/c1iooepics.snap but the problem persists

16223   Thu Jun 24 16:40:37 2021 KojiUpdateSUSMC lock acquired back again

[Koji, Anchal]

The issue of the PD output was that the PD whitened outputs of the sat amp (D080276) are differential, while the successive circuit (D000210 PD whitening unit) has the single-ended inputs. This means that the neg outputs (D080276 U2) have always been shorted to GND with no output R. This forced AD8672 to work hard at the output current limit. Maybe there was a heat problem due to this current saturation as Anchal reported that the unit came back sane after some power-cycling or opening the lid. But the heat issue and the forced differential voltage to the input stage of the chip eventually cause it to fail, I believe.

Anchal came up with the brilliant idea to bypass this issue. The sat amp box has the PD mon channels which are single-ended. We simply shifted the output cables to the mon connectors. The MC1 sus was nicely damped and the IMC was locked as usual. Anchal will keep checking if the circuit will keep working for a few days.

Attachment 1: P_20210624_163641_1.jpg
16252   Wed Jul 21 14:50:23 2021 KojiUpdateSUSNew electronics

Jun 29, 2021 BIO I/F 6 units
Jul 19, 2021 PZT Drivers x2 / QPD Transimedance amp x2

Attachment 1: P_20210629_183950.jpeg
Attachment 2: P_20210719_135938.jpeg
16281   Tue Aug 17 04:30:35 2021 KojiUpdateSUSNew electronics

Aug 17, 2021 2x ISC Whitening

Delivered 2x Sat Amp board to Todd

Attachment 1: P_20210816_234136.jpg
Attachment 2: P_20210816_235106.jpg
Attachment 3: P_20210816_234220.jpg
16296   Wed Aug 25 08:53:33 2021 JordanUpdateSUS2" Adapter Ring for SOS Arrived 8/24/21

8 of the 2"->3" adapter rings (D2100377) arrived from RDL yesterday. I have not tested the threads but dimensional inspection on SN008 cleared. Parts look very good. The rest of the parts should be shipping out in the next week.

Attachment 1: 20210824_152259.jpg
Attachment 2: 20210824_152259.jpg
Attachment 3: 20210824_152308.jpg
16326   Tue Sep 14 16:12:03 2021 JordanUpdateSUSSOS Tower Hardware

Yehonathan noticed today that the silver plated hardware on the assembled SOS towers had some pretty severe discoloration on it. See attached picture.

These were all brand new screws from UC components, and have been sitting on the flow bench for a couple months now. I believe this is just oxidation and is not an issue, I spoke to Calum as well and showed him the attached picture and he agreed it was likely oxidation and should not be a problem once installed.

He did mention if there is any concern from anyone, we could take an FTIR sample and send it to JPL for analysis, but this would cost a few hundred dollars.

I don't believe this to be an issue, but it is odd that they oxidized so quickly. Just wanted to relay this to everyone else to see if there was any concern.

Attachment 1: 20210914_160111.jpg
16328   Tue Sep 14 17:14:46 2021 KojiUpdateSUSSOS Tower Hardware

Yup this is OK. No problem.

16342   Fri Sep 17 20:22:55 2021 KojiUpdateSUSEQ M4.3 Long beach

EQ  M4.3 @longbeach
2021-09-18 02:58:34 (UTC) / 07:58:34 (PDT)
https://earthquake.usgs.gov/earthquakes/eventpage/ci39812319/executive

• All SUS Watchdogs tripped, but the SUSs looked OK except for the stuck ITMX.
• Damped the SUSs (except ITMX)
• IMC automatically locked
• Turned off the damping of ITMX and shook it only with the pitch bias -> Easily unstuck -> damping recovered -> realignment of the ITMX probably necessary.
• Done.
16343   Mon Sep 20 12:20:31 2021 PacoSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

[yehonathan, paco, anchal]

We attempted to find any symptoms for actuation problems in the PRMI configuration when actuated through BS and PRM.

Our logic was to check angular (PIT and YAW) actuation transfer function in the 30 to 200 Hz range by injecting appropriately (f^2) enveloped excitations in the SUS-ASC EXC points and reading back using the SUS_OL (oplev) channels.

From the controls, we first restored the PRMI Carrier to bring the PRM and BS to their nominal alignment, then disabled the LSC output (we don't need PRMI to be locked), and then turned off the damping from the oplev control loops to avoid supressing the excitations.

We used diaggui to measure the 4 transfer functions magnitudes PRM_PIT, PRM_YAW, BS_PIT, BS_YAW, as shown below in Attachments #1 through #4. We used the Oplev calibrations to plot the magnitude of the TFs in units of urad / counts, and verified the nominal 1/f^2 scaling for all of them. The coherence was made as close to 1 as possible by adjusting the amplitude to 1000 counts, and is also shown below. A dip at 120 Hz is probably due to line noise. We are also assuming that the oplev QPDs have a relatively flat response over the frequency range below.

Attachment 1: PRM_PIT_ACT_TF.pdf
Attachment 2: PRM_YAW_ACT_TF.pdf
Attachment 3: BS_PIT_ACT_TF.pdf
Attachment 4: BS_YAW_ACT_TF.pdf
16345   Mon Sep 20 14:22:00 2021 ranaSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

I suggest plotting all the traces in the plot so we can see their differences. Also remove the 1/f^2 slope so that we can see small differences. Since the optlev servos all have low pass filters around 15-20 Hz, its not necessary to turn off the optlev servos for this measurement.

I think that based on the coherence and the number of averages, you should also be able to use Bendat and Piersol so estimate the uncertainy as a function of frequency. And we want to see the comparison coil-by-coil, not in the DoF basis.

4 sweeps for BS and 4 sweeps for PRM.

16358   Thu Sep 23 15:29:11 2021 PacoSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

[Anchal, Paco]

We had a second go at this with an increased number of averages (from 10 to 100) and higher excitation amplitudes (from 1000 to 10000). We did this to try to reduce the relative uncertainty a-la-Bendat-and-Pearsol

$\delta G / G = \frac{1}{\gamma \sqrt{n_{\rm avg}}}$

where $\gamma, n_{\rm avg}$ are the coherence and number of averages respectively. Before, this estimate had given us a ~30% relative uncertainty and now it has been improved to ~ 10%. The re-measured TFs are in Attachment #1. We did 4 sweeps for each optic (BS, PRM) and removed the 1/f^2 slope for clarity. We note a factor of ~ 4 difference in the magnitude of the coil to angle TFs from BS to PRM (the actuation strength in BS is smaller).

For future reference:

With complex G, we get complex error in G using the formula above. To get uncertainity in magnitude and phase from real-imaginary uncertainties, we do following (assuming the noise in real and imaginary parts of the measured transfer function are incoherent with each other):
$G = \alpha + i\beta$

$\delta G = \delta\alpha + i\delta \beta$

$\delta |G| = \frac{1}{|G|}\sqrt{\alpha^2 \delta\alpha^2 + \beta^2 \delta \beta^2}$

$\delta(\angle G) = \frac{1}{|G|^2}\sqrt{\alpha^2 \delta\alpha^2 + \beta^2 \delta\beta^2} = \frac{\delta |G|}{|G|}$

Attachment 1: BS_PRM_ANG_ACT_TF.pdf
16364   Wed Sep 29 09:36:26 2021 JordanUpdateSUS2" Adapter Ring Parts for SOS Arrived 9/28/21

The remaining machined parts for the SOS adapter ring have arrived. I will inspect these today and get them ready for C&B.

Attachment 1: 20210929_092418.jpg
16371   Fri Oct 1 14:25:27 2021 yehonathanSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

{Paco, Yehonathan, Hang}

We measured the sensing PRMI sensing matrix. Attachment 1 shows the results, the magnitude of the response is not calibrated. The orthogonality between PRCL and MICH is still bad (see previous measurement for reference).

Hang suggested that since MICH actuation with BS and PRM is not trivial (0.5*BS - 0.34*PRM) and since PRCL is so sensitive to PRM movement there might be a leakage to PRCL when we are actuating on MICH. So there may be a room to tune the PRM coefficient in the MICH output matrix.

Attachment 2 shows the sensing matrix after we changed the MICH->PRM coefficient in the OSC output matrix to -0.1.

It seems like it made things a little bit better but not much and also there is a huge uncertainty in the MICH sensing.

Attachment 1: MICH_PRM_-0.34.png
Attachment 2: MICH_PRM_-0.1.png
16374   Mon Oct 4 16:00:57 2021 YehonathanSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

{Yehonathan, Anchel}

In an attempt to fix the actuation of the PRMI DOFs we set to modify the output matrix of the BS and PRM such that the response of the coils will be similar to each other as much as possible.

To do so, we used the responses at a single frequency from the previous measurement to infer the output matrix coefficients that will equilize the OpLev responses (arbitrarily making the LL coil as a reference). This corrected the imbalance in BS almost completely while it didn't really work for PRM (see attachment 1).

The new output matrices are shown in attachment 2-3.

Attachment 1: BS_PRM_ANG_ACT_TF_20211004.pdf
Attachment 2: BS_out_mat_20211004.txt
9.839999999999999858e-01 8.965770586285104482e-01 9.486710352885977526e-01 3.099999999999999978e-01
1.016000000000000014e+00 9.750242104232501594e-01 -9.291967546765563801e-01 3.099999999999999978e-01
9.839999999999999858e-01 -1.086765190351774768e+00 1.009798093279114628e+00 3.099999999999999978e-01
1.016000000000000014e+00 -1.031706735496689786e+00 -1.103142995587099939e+00 3.099999999999999978e-01
0.000000000000000000e+00 0.000000000000000000e+00 0.000000000000000000e+00 1.000000000000000000e+00

Attachment 3: PRM_out_mat_20211004.txt
1.000000000000000000e+00 1.033455230230304611e+00 9.844796282226820905e-01 0.000000000000000000e+00
1.000000000000000000e+00 9.342329554807877745e-01 -1.021296201828568506e+00 0.000000000000000000e+00
1.000000000000000000e+00 -1.009214777246558503e+00 9.965113815550634691e-01 0.000000000000000000e+00
1.000000000000000000e+00 -1.020129700278567197e+00 -9.973560027273553619e-01 0.000000000000000000e+00
0.000000000000000000e+00 0.000000000000000000e+00 0.000000000000000000e+00 1.000000000000000000e+00
`
16375   Mon Oct 4 16:10:09 2021 ranaSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

not sure that this is necessary. If you look at teh previous entries Gautam made on this topic, it is clear that the BS/PRM PRMI matrix is snafu, whereas the ITM PRMI matrix is not.

Is it possible that the ~5% coil imbalance of the BS/PRM can explain the observed sensing matrix? If not, then there is no need to balance these coils.

16383   Tue Oct 5 20:04:22 2021 PacoSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

[Paco, Rana]

We had a look at the BS actuation. Along the way we created a couple of issues that we fixed. A summary is below.

1. First, we locked MICH. While doing this, we used the /users/Templates/ndscope/LSC/MICH.yml ndscope template to monitor some channels. I edited the yaml file to look at C1:LSC-ASDC_OUT_DQ instead of the REFL_DC. Rana pointed out that the C1:LSC-MICH_OUT_DQ (MICH control point) had a big range (~ 5000 counts rms) and this should not be like that.
2. We tried to investigate the aforementioned thing by looking at the whitening / uwhitening filters but all the slow epics channels where "white" on the medm screen. Looking under CDS/slow channel monitors, we realized that both c1iscaux and c1auxey were weird, so we tried telnet to c1iscaux without success. Therefore, we followed the recommended wiki procedure of hard rebooting this machine. While inside the lab and looking for this machine, we touched things around the 'rfpd' rack and once we were back in the control room, we couldn't see any light on the AS port camera. But the whitening filter medm screens were back up.
3. While rana ssh'd into c1auxey to investigate about its status, and burtrestored the c1iscaux channels, we looked at trends to figure out if anything had changed (for example TT1 or TT2) but this wasn't the case. We decided to go back inside to check the actual REFL beams and noticed it was grossly misaligned (clipping)... so we blamed it on the TTs and again, went around and moved some stuff around the 'rfpd' rack. We didn't really connect or disconnect anything, but once we were back in the control room, light was coming from the AS port again. This is a weird mystery and we should systematically try to repeat this and fix the actual issue.
4. We restored the MICH, and returned to BS actuation problems. Here, we essentially devised a scheme to inject noise at 310.97 Hz and 313.74. The choice is twofold, first it lies outside the MICH loop UGF (~150 Hz), and second, it matches the sensing matrix OSC frequencies, so it's more appropriate for a comparison.
5. We injected two lines using the BS SUS LOCKIN1 and LOCKIN2 oscilators so we can probe two coils at once, with the LSC loop closed, and read back using the C1:LSC-MICH_IN1_DQ channel. We excited with an amplitude of 1234.0 counts and 1254 counts respectively (to match the ~ 2 % difference in frequency) and noted that the magnitude response in UR was 10% larger than UL, LL, and LR which were close to each other at the 2% level.

[Paco]

After rana left, I did a second pass at the BS actuation. I took TF measurements at the oscilator frequencies noted above using diaggui, and summarize the results below:

TF UL (310.97 Hz) UR (313.74 Hz) LL (310.97 Hz) LR (313.74 Hz)
Magnitude (dB) 93.20 92.20 94.27 93.85
Phase (deg) -128.3 -127.9 -128.4 -127.5

This procedure should be done with PRM as well and using the PRCL instead of MICH.

16384   Wed Oct 6 15:04:36 2021 HangUpdateSUSPRM L2P TF measurement & Fisher matrix analysis

[Paco, Hang]

Yesterday afternoon Paco and I measured the PRM L2P transfer function. We drove C1:SUS-PRM_LSC_EXC with a white noise in the 0-10 Hz band (effectively a white, longitudinal force applied to the suspension) and read out the pitch response in C1:SUS-PRM_OL_PIT_OUT. The local damping was left on during the measurement. Each FFT segment in our measurement is 32 sec and we used 8 non-overlapping segments for each measurement. The empirically determined results are also compared with the Fisher matrix estimation (similar to elog:16373).

Results:

Fig. 1 shows one example of the measured L2P transfer function. The gray traces are measurement data and shaded region the corresponding uncertainty. The olive trace is the best fit model.

Note that for a single-stage suspension, the ideal L2P TF should have two zeros at DC and two pairs of complex poles for the length and pitch resonances, respectively. We found the two resonances at around 1 Hz from the fitting as expected. However, the zeros were not at DC as the ideal, theoretical model suggested. Instead, we found a pair of right-half plane zeros in order to explain the measurement results. If we cast such a pair of right-half plane zeros into (f, Q) pair, it means a negative value of Q. This means the system does not have the minimum phase delay and suggests some dirty cross-coupling exists, which might not be surprising.

Fig. 2 compares the distribution of the fitting results for 4 different measurements (4 red crosses) and the analytical error estimation obtained using the Fisher matrix (the gray contours; the inner one is the 1-sigma region and the outer one the 3-sigma region). The Fisher matrix appears to underestimate the scattering from this experiment, yet it does capture the correlation between different parameters (the frequencies and quality factors of the two resonances).

One caveat though is that the fitting routine is not especially robust. We used the vectfit routine w/ human intervening to get some initial guesses of the model. We then used a standard scipy least-sq routine to find the maximal likelihood estimator of the restricted model (with fixed number of zeros and poles; here 2 complex zeros and 4 complex poles). The initial guess for the scipy routine was obtained from the vectfit model.

Fig. 3 shows how we may shape our excitation PSD to maximize the Fisher information while keeping the RMS force applied to the PRM suspension fixed. In this case the result is very intuitive. We simply concentrate our drive around the resonance at ~ 1 Hz, focusing on locations where we initially have good SNR. So at least code is not suggesting something crazy...

Fig. 4 then shows how the new uncertainty (3-sigma contours) should change as we optimize our excitation. Basically one iteration (from gray to olive) is sufficient here.

We will find a time very recently to repeat the measurement with the optimized injection spectrum.

Attachment 1: prm_l2p_tf_meas.pdf
Attachment 2: prm_l2p_fisher_vs_data.pdf
Attachment 3: prm_l2p_Pxx_evol.pdf
Attachment 4: prm_l2p_fisher_evol.pdf
16385   Wed Oct 6 15:39:29 2021 AnchalSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

Note that your tests were done with the output matrix for BS and PRM in the compensated state as done in 40m/16374. The changes made there were supposed to clear out any coil actuation imbalance in the angular degrees of freedom.

ELOG V3.1.3-