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ID Date Authorup Type Category Subject
  17314   Sun Nov 27 15:30:22 2022 ChrisUpdateOptimal ControlIMC alignment controller testing

Five more mode cleaner alignment controllers were tested this morning (remotely). These were designed to run in tandem with the standard controller, instead of supplanting it. Before the test, c1ioo was burt restored back to the settings of the previous test on Oct 28, and in MC TRANS PIT/YAW filter banks the 80 dB gain filters were disengaged and outputs were enabled. Subsequently, all settings were returned to the original values. Each test consisted of five minutes with pitch alignment uncontrolled, five minutes with the standard controller only, and twenty minutes with both controllers enabled. GPS times for each phase of testing are the following:

  • musgo
    • OL start 1353602764
    • CL start 1353603074
    • policy start 1353603410
  • musgo_ghost
    • OL start 1353604697
    • CL start 1353605007
    • policy start 1353605355
  • musgo_stumble
    • OL start 1353606574
    • CL start 1353606884
    • policy start 1353607229
  • musgo_goldfish
    • OL start 1353608446
    • CL start 1353608756
    • policy start 1353609099
  • musgo_late
    • OL start 1353610321
    • CL start 1353610631
    • policy start 1353610971
  1694   Wed Jun 24 10:53:34 2009 Chris ZimmermanUpdateGeneralWeek 1/2 Update

I've spent most of the last week doing background reading; fourier transforms, shm, e&m, and other physics that I didn't cover at school.  I also read a few chapters in Saulson, especially the chapter on noise and shot noise.  To get a better grip on what I'm going to be doing I read through the polarization chapter in Hobbs' "Optics" text, mostly on wave plates since that's a large part of this readout.  Since then I've been working up to calculating the shot noise, starting with the electric field throughout the new interferometer readout.

  1710   Wed Jul 1 10:56:42 2009 Chris ZimmermanUpdateGeneralWeek 2/3 Update

I spent the last week working a lot with the differences between a basic Michelson readout and the new one as a displacement sensor.  The new one (w/ wave plates) ends with two differently polarized beams and should have better sensitivity; I've also been going through noise/sensitivity calculations for each, although that hit a road block when I had to start the 1st SURF progress report, which has taken up most of my time since Saturday.

  1720   Wed Jul 8 11:05:40 2009 Chris ZimmermanUpdateGeneralWeek 3/4 Update

The last week I've spent mostly working on calculating shot noise and other sensitivities in three michelson sensor setups, the standard michelson, the "long range" michelson (with wave plates), and the proposed EUCLID setup.  The goal is to show that there is some inherent advantage to the latter two setups as displacement sensors.  This involved looking into polarization and optics a lot more, so I've been spending a lot of time on that also.  For example, the displacement sensitivity/shot noise on the standard michelson is around 6:805*10^-17 m/rHz at L_=1*10^-7m, as shown in the graph.  NSD_Displacement.png

  1750   Wed Jul 15 12:44:28 2009 Chris ZimmermanUpdateGeneralWeek 4/5 Update

I've spent most of the last week working on finishing up the UCSD calculations, comparing it to the EUCLID design, and thinking about getting started with a prototype and modelling in MATLAB.  Attached is something on EUCLID/UCSD sensors.

Attachment 1: Comparison.pdf
Comparison.pdf Comparison.pdf
  1779   Wed Jul 22 16:15:52 2009 Chris ZimmermanUpdateGeneralWeek 5/6 Update

The last week I've started setting up the HeNe laser on the PSL table and doing some basic measurements (Beam waist, etc) with the beam scan, shown on the graph.  Today I moved a few steering mirrors that steve showed me from at table on the NW corner to the PSL table.  The goal setup is shown below, based on the UCSD setup.  Also, I found something that confused me in the EUCLID setup, a  pair of quarter wave plates in the arm of their interferometer, so I've been working out how they organized that to get the results that they did.  I also finished calculating the shot noise levels in the basic and UCSD models, and those are also shown below (at 633nm, 4mw) where the two phase-shifted elements (green/red) are the UCSD outputs, in quadrature (the legend is difficult to read).

 

 

Attachment 1: Beam_Scan.jpg
Beam_Scan.jpg
Attachment 2: Long_Range_Michelson_Setup_1_-_Actual.png
Long_Range_Michelson_Setup_1_-_Actual.png
Attachment 3: NSD_Displacement.png
NSD_Displacement.png
  14305   Mon Nov 19 14:59:48 2018 ChubUpdateVACVent 81

Vent 80 is nearly complete; the instrument is almost to atmosphere.  All four ion pump gate valves have been disconnected, though the position sensors are still connected,and all annulus valves are open.  The controllers of TP1 and TP3 have been disconnected from AC power. VC1 and VC2 have been disconnected and must remained closed. Currently, the RGA is being vented through the needle valve and the RGA had been shut off at the beginning of the vent preparations.  VM1 and VM3 could not be actuated.  The condition status is still listed as Unidentified because of the disconnected valves. 

  14350   Thu Dec 13 10:03:07 2018 ChubUpdateGeneralOMC chamber

Bob, Aaron, and I removed the door from the OMC chamber this morning.  Everything went well.

  14364   Tue Dec 18 11:42:40 2018 ChubUpdateGeneralAcromag box wired

The Auxiliary DAQ Chassis, or Acromag box, is now wired and ready for testing.  I will be sorting the cables at the vacuum rack to make connection to the box easier.

 

  14395   Thu Jan 10 11:32:40 2019 ChubUpdateVACManual valve interfaced with CDS

Connected the manual gate valve status indicator to the Acromag box this morning.  Labeled the temporary cable (a 50' 9p DSUB, will order a proper sized cable shortly) and the panel RV2.  

  14420   Tue Jan 29 16:12:21 2019 ChubUpdate  

The foam in the cable tray wall passage had been falling on the floor in little bite-sized pieces, so I investigated and found a fiber cable that had be chewed/clawed through.  I didn't find any droppings anywhere in the 40m, but I decided to bait an un-set trap and see if we'd find activity around it. There has been none so far.  If there is still none tomorrow, I will move the trap and keep looking for signs of rodentia.  At the moment, the trap is in a box in front of the double doors at the north end of the control room.  Next it will be place in the IFO room, up in the cable tray. 

gautam: the fiber that was damaged was the one from the LSC rack FiBox to the control room FiBox. So no DAFI action for a bit...

  14437   Wed Feb 6 10:07:23 2019 ChubUpdate pre-construction inspection

The Central Plant building will be undergoing seismic upgrades in the near future.  The adjoining north wall along the Y arm will be the first to have this work done, from inside the Central Plant.  Project manager Eugene Kim has explained the work to me and also noted our concerns.  He assured me that the seismic noise from the construction will be minimized and we will always be contacted when the heaviest construction is to be done.

Tomorrow at 11am, I will bring Mr. Kim and a few others from the construction team to look at the wall from inside the lab.  If you have any questions or concerns that you want to have addressed, please email them to me or contact Mr. Kim directly at x4860 or through email at eugene.kim@caltech.edu . 

  14572   Thu Apr 25 10:13:15 2019 ChubUpdateGeneralAir Handler Out of Commission

The air handler on the roof of the 40M that supplies the electronics shop and computer room is out of operation until next week.  Adding insult to injury, there is a strong odor of Liquid Wrench oil (a creeping oil for loosening stuck bolts that has a solvent additive) in the building.  If you don't truly need to be in the 40M, you may want to wait until the environment is back to being cool and "unscented".  On a positive note, we should have a quieter environment soon!

  14601   Fri May 10 13:00:25 2019 ChubUpdateGeneralcrane inspection complete

The 40M jib cranes all passed inspection!

Attachment 1: 20190510_110245.jpg
20190510_110245.jpg
  14749   Thu Jul 11 13:08:36 2019 ChubSummaryCDSP2 interface board

It's nice and compact, and the cost of new 15-pin DSUB cables shouldn't be a factor here.  What does the 15p cable connect to?

  14869   Tue Sep 10 16:10:40 2019 ChubUpdate Rack Update

Still removing old cable, terminal blocks and hardware.  Once new strain reliefs and cable guides are in place, I will need to disconnect cables and reroute them.  Please let me know dates and times when that is not going to interrupt your work! 

Attachment 1: 20190910_154018.jpg
20190910_154018.jpg
Attachment 2: 20190910_154006.jpg
20190910_154006.jpg
  15222   Mon Feb 24 08:36:32 2020 ChubUpdateGeneralHVAC repair

The HVAC people replaced a valve and repaired the pneumatic plumbing on the roof air handler.  Temperature has been stable during the day since Thursday.  If anyone is in the control room during the evening, please make a note of the temperature.

Chub

  15304   Wed Apr 15 15:15:17 2020 ChubUpdateVACnitrogen cylinders delivered

Four nitrogen cylinders replaced the empties in the rack at the west entrance.  Additionally, Airgas will now deliver only once a week.  Let me know via email or text when the there are four empties in the rack and I'll order the next round.

  15314   Thu Apr 30 07:29:01 2020 ChubUpdateVACN2 delivered.

Hi All,

The new nitrogen cylinders were delivered to the rack at the west entrance.  We only get one Airgas delivery per week during the stay-at-home order, but so far they've not let us down.

  15416   Fri Jun 19 11:02:10 2020 ChubUpdateGeneralcustom feedthrough flanges are here!

The four 4x25DSUB and single 8x25DSUB feedthrough flanges have arrived and will be picked up from the dock and brought to the 40M lab.

  15680   Tue Nov 17 13:24:40 2020 ChubUpdateGeneralbig UPS on the way

Ordered 11/16 from CDW, on PO# S492940, the high voltage Tripp Lite SMART5000XFMRXL  for TP-1.  Should be arriving in about a week.

  15722   Thu Dec 10 11:07:24 2020 ChubUpdateVACUPS fault

Is that a fault code that you can decipher in the manual, or just a light telling you nothing but your UPS is dead?

  15723   Thu Dec 10 11:17:50 2020 ChubUpdateVACUPS fault

I can't find anything in the manual that describes the nature of the FAULT message.  In fact, it's not mentioned at all.  If the unit detects a fault at its output, I would expect a bit more information.  This unit does a programmable level of input error protection, too, usually set at 100%.  Still, there is no indication in the manual whether an input issue would be described as a fault; that usually means a short or lifted ground at the output.

Quote:

Is that a fault code that you can decipher in the manual, or just a light telling you nothing but your UPS is dead?

  16058   Wed Apr 21 05:48:47 2021 ChubUpdateGeneralPSL HEPA Maintenance

Yikes!  That's ONE filter.  I'll get another from storage.

  16074   Thu Apr 22 14:41:55 2021 ChubUpdatePSLNew HEPA speed control

When adjusting the blower speed, give the blower at least 30 seconds to speed up or slow down to the set speed.  The flywheel effect of the big motor armature and blower mass requires time to follow the control current.  Note the taller Flanders HEPA filters.  These and the new intake filters should keep the PSL air clean for a long time!

Quote:

The new HEPA speed controllers are attached at the middle of the HEPA unit (not at the edge of the unit)... (Attachment 1)
You still need a step./stool to touch the knob and need a ladder for a more precise setting.

We still don't know the optimal speed of the nominal IFO operation. For now, the HEPAs are running at the max speed (Attachment 2).
Once we know the optimal setting, we mark the knobs so that we can see them only with the step.

 

Attachment 1: 40M_PSL_HEPA.jpg
40M_PSL_HEPA.jpg
  16121   Wed May 5 13:05:07 2021 ChubUpdateGeneralchassis delivery from De Leone

Assembled chassis from De Leone placed in the 40 Meter Lab, along the west wall and under the display pedestal table.  The leftover parts are in smaller Really Useful boxes, also on the parts pile along the west wall.

Attachment 1: de_leone_del_5-5-21.jpg
de_leone_del_5-5-21.jpg
  16155   Mon May 24 08:38:26 2021 ChubUpdateElectronics18-bit AI, 16-bit AI and 16-bit AA

- High priority units: 2x 18AI / 1x 16AI / 3x 16AA

All six are reworked and on the electronics workbench. The rest should be ready by the end of the week.

Chub

  16160   Tue May 25 17:08:17 2021 ChubUpdateElectronicschassis rework complete!

All remaining chasses have been reworked and placed on the floor along the west wall in Room 104. 

Attachment 1: 40M_chassis_reworked_5-25-21.jpg
40M_chassis_reworked_5-25-21.jpg
  16472   Wed Nov 17 07:32:48 2021 ChubUpdateGeneralwire clamp plate mod

This will be difficult to modify with the magnets and dumbells in place.  Even if someone CAN clamp this piece into an endmill machine with the magnets/dumbells in place, the vibration of the cutting operation may be enough to break them off.

  16513   Thu Dec 16 15:04:12 2021 ChubUpdateElectronicsITMX feedthroughs and in-vac cables installed

The ITMX 10" flange with four DSUB-25 feedthroughs has been install with the cables connected at the in-vac side.  See photo; as requested, LO1-1 and LO1-2 are connected to the top row of feedthroughs from left to right respectively and the opposite ends of the cables placed left to right on the laser table.  PR2-1 and PR2-2 are connected to the lower row of feedthroughs from left to right respectively, with the opposite ends placed on the surface below the laser from left to right.  This seemed the easiest way to keep the cable orientation clear.

Attachment 1: ITMX_feedthrough_install_12-16-21.jpg
ITMX_feedthrough_install_12-16-21.jpg
  16644   Thu Feb 3 14:47:12 2022 ChubUpdateElectronicsnew UPS in place

Received the new 1100VA APC UPS today and placed it at the bottom of the valve rack.  I'd connected the battery and plugged the unit into the AC outlet, but did not turn it on due to the power outage this weekend.

  16646   Fri Feb 4 10:04:47 2022 ChubUpdateGeneraldish soap and clean scrub sponges!

Bought dish soap and scrub sponges today and placed them under the sink with the other dish supplies.

Attachment 1: 40m_supplies.jpg
40m_supplies.jpg
  16921   Wed Jun 15 17:12:39 2022 CiciSummaryGeneralPreparation for AUX Loop Characterization

[Deeksha, Cici]

We went to the end Xarm station and looked at the green laser setup and electronics. We fiddled with the SR-785 and experimented with low-pass filters, and will be exploring the Python script tomorrow.

  16926   Thu Jun 16 19:49:48 2022 CiciUpdateGeneralUsing the SR785

[Deeksha, Cici]

We used a python script to collect data from the SR785 remotely. The SR785 is now connected to the wifi network via Ethernet port 7.

  16933   Tue Jun 21 14:59:22 2022 CiciSummaryGeneralAUX Transfer Function Loop Exploration

[Deeksha, Cici]

We learned about the auxillary laser control loop, and then went into the lab to identify the components and cables represented by our transfer functions. We connected to the SR785 inside the lab so that we can use it to insert noise next time, and measure the output in various parts of the control loop.

  16950   Mon Jun 27 13:25:50 2022 CiciUpdateGeneralCharacterizing the Transfer Loop

[Deeksha, Cici]

We first took data of a simple low pass filter, and attempted to perform a fit to both the magnitude and phase in order to find the Z of the components. Once we felt confident in our ability to measure tranfer functions, we took data and plotted the transfer function of the existing control loop of the AUX laser. What we found generally followed the trend of, but was lower than, 10^4/f, which is what we hoped to match, and also had a strange unexplained notch ~1.3 kHz. The magnitude and phase data both got worse after around 40-50 kHz, which we believe is because the laser came out of lock near the end of the run. 

Edit: 

[Attachment 2 and 3] are the frequency response of the low pass filter, curves fitted using least squares in python.

[Attachment 1 and 4] is the same measurement of OLTF of the actual AUX circuit, and the control diagram pointing out the location of excitation and test point.

Attachment 1: TF_measurement_b.png
TF_measurement_b.png
Attachment 2: transfer_function_mag_fit.png
transfer_function_mag_fit.png
Attachment 3: transfer_function_phase_fit.png
transfer_function_phase_fit.png
Attachment 4: control_flow.png
control_flow.png
  16955   Tue Jun 28 16:26:58 2022 CiciSummaryGeneralVector fitting open loop transfer function/Audio cancellation of optical table enclosure

[Deeksha, Cici]

We attempted to use vectfit to fit our earlier transfer function data, and were generally unsuccessful (see vectfit_firstattempt.png), but are much closer to understanding vectfit than before. Couple of problems to address - finding the right set of initial poles to start with has been very hard, and also however vectfit is plotting the phase data is unwrapping it, which makes it generally unreadable. Still working on how to mess with the vectfit automatically-generated plots. In general, our data is very messy (this is old data of the transfer function from last week), so we took more data today to see if our coherence was the problem (see TFSR785_28-06-2022_161937.pdf). As is visible from the graph, our coherence is terrible, and above 1kHz is almost entirely below 0.5 (or 0.2) on both channels. Figuring out why this is and fixing it is our first priority.

In the process of taking new data, we also found out that the optical table enclosure at the end of the X-arm does a decent job of sound isolation (see enclosure_open.mp4 and enclosure_closed.mp4). The clicking from the shutter is visible on a spectrogram at high frequencies when the enclosure is open, but not when it is closed. We also discovered that the script to toggle the shutter can run indefinitely, which can break the shutter, so we need to fix that problem!

Attachment 1: vectfit_firstattempt.png
vectfit_firstattempt.png
Attachment 2: TFSR785_28-06-2022_161937.pdf
TFSR785_28-06-2022_161937.pdf
Attachment 3: enclosure_open.MP4
Attachment 4: enclosure_closed.MP4
  17051   Mon Aug 1 17:19:39 2022 CiciSummaryGeneralRPitaya Data on Jupyter Notebook

Have successfully plotted data from the Red Pitaya on Jupyter Notebook! Have lost years of my life fighting with PyQt. Thanks to Deeksha for heavy contribution. Next task is to get actually good data (seeing mostly noise right now and haven't figured out how to change my input settings) and then to go to set up the RPi in the lab.

  17070   Wed Aug 10 15:33:59 2022 CiciUpdateGeneralWorking Red Pitaya VNA

TL;DR: I am now able to inject a swept sine and measure a transfer function with python on my Red Pitaya! Attached is a Bode plot for a swept sine from 1 - 30 MHz, going through a band pass filter of 9.5 - 11.5 MHz.

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  • Spent too long trying to get pyRPL to work, do not recommend. The code on their website has a lot of problems (like syntax-error level problems), and is ultimately designed to open up and start a GUI, which is not what I want even if it did work.
  • Found some code on the git repository of someone at Delft University of Technology, worked better but still not great (oscilloscope/spectrum analyzer functions were alright, but couldn't successfully run a VNA with it, and overcomplicated). Helped me figure out appropriate decimation factors. Realized it was not using the FPGA to get TF data but instead just collecting a lot of time trace data and then taking an FFT in the code to get the TF, which wasn't ideal.
  • Eventually switched to using the Red Pitaya SCPI server to talk to the Red Pitaya myself, successful! I inject a swept sine with a for loop that just cycles through frequencies and takes the transfer function at each one.
    • Was originally getting the transfer function by using scipy.signal.csd() and scipy.signal.welch() to get Pxy and Pxx and dividing, and then just finding the closest point in the frequency spectrum to the frequency I was inserting.
    • Switched to doing IQ demodulation myself: where x(t) is the measurement before the band pass filter and y(t) is the measurement after, taking the mean of (x(t) * cos(2pi*freq)) = a1, mean(x*sin()) = a2, mean(y*cos()) = b1, mean(y*sin()) = b2, and then TF(freq) = (b1 + i b2)/(a1 + i a2).
    • Unfortunately still taking time trace data and then calculating the TF instead of using the FPGA, but I have not found anything online indicating that people are able to get VNA capabilities on the Red Pitaya without collecting and sending all the time trace data... I'm still not sure if that's actually a Red Pitaya capability yet.

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To do:

  • Will go take measurements of the AUX laser loop with the RPi! Have a good diagram of when I did it with the SR785 so it shouldn't be too hard hopefully.
  • Figure out how to get coherence data!!
  • Figure out how to get the RPi on the wifi. Right now I'm just plugging the RPi into my computer. Paco and I were working on this before and had trouble finding old passwords... Hopefully will not be too much of a roadblock.
Attachment 1: rpi_vna_test.pdf
rpi_vna_test.pdf
  17076   Thu Aug 11 17:15:33 2022 CiciUpdateGeneralMeasuring AUX Laser UGF with Red Pitaya

TL;DR: Have successfully measured the UGF of the AUX laser on my Red Pitaya! Attached is one of my data runs (pdf + txt file). 

---------------------------------------------------------------

  • Figured out how to get a rudimentary coherence (use scipy.signal.coherence to get Cxy = abs(Pxy)**2/(Pxx*Pyy), then find what point is the closest to the frequency I'm inserting on that iteration of the swept sine and get the coherence closest to that). Not precisely the coherence at the frequency I'm inserting though, so not perfect... more of a lower bound of coherence.
  • Figured out how to get the UGF from the data automatically (no error propagation yet... necessary next step)
  • Put my red pitaya in the X-arm AUX laser control electronics (thank you to Anchal for help figuring out where to put it and locking the x-arm.) Counts dropped from 4500 to 1900 with the x-arm locked, so 58% mode matching. I lose lock at an amplitude >0.05 or so.
  • Wrote a little script to take data and return a time-stamped text file with all the parameters saved and a time-stamped pdf of the TF magnitude, UGF, phase, and coherence, so should be easy to take more data next time!

----------------------------------------------------------------

  • need to take more accurate coherence data
  • need to propagate uncertainty on UGF (probably high...)
  • take more data with higher coherence (the file attached doesn't have great coherence and even that was one of my better runs, will probably increase averaging since increasing amplitude was a problem)
Attachment 1: rpi_OLG_2022_08_11_16_51_53.pdf
rpi_OLG_2022_08_11_16_51_53.pdf
Attachment 2: rpi_OLG_2022_08_11_16_51_53.txt
# frequency start: 500.0
# frequency stop: 50000.0
# samples: 50
# amplitude: 0.01
# cycles: 500
# max fs: 125000000.0
# N: 16384UGF: 9264.899326705621
# Frequency[Hz] Magnitude[V/V] Phase[rad] Coherence
4.999999999999999432e+02 5.216612299292965105e+01 -7.738468629291910261e-01 7.660920305860696722e-02
5.492705709937790743e+02 3.622076363933444298e+01 -5.897393740774580229e-01 3.183076012979469405e-01
... 49 more lines ...
  17087   Wed Aug 17 10:27:49 2022 CiciUpdateGeneralLocking X-arm AUX laser

TL;DR: Got the x-arm aux laser locked again and took more data - my fit on my transfer functions need improvement and my new method for finding coherence doesn't work so I went back to the first way! See attached file for an example of data runs with poor fits. First one has the questionable coherence data, second one has more logical coherence. (ignore the dashed lines.)

------------------------------------------------------------------------------------

  • The aux laser on the x-arm was still off after the power shutdown, so Paco and I turned it back on, and realigned the oplev of the ETMX - initial position was P = -0.0420, Y = -5.5391.
  • Locked the x-arm and took another few runs - was calculating coherence by I/Q demodulation of the buffers and then recombining the I/Q factors and then taking scipy.signal.coherence(), but for some reason this was giving me coherence values exclusively above 0.99, which seemed suspicious. When I calculated it the way I had before, by just taking s.s.coherence() of the buffers, I got a coherence around 1 except for in noisy areas of the data where it dropped more significantly, and seemed to be more correlated to the data. So I'll go back to using that way.
  • I also think my fits are not great - my standard error of the fits (calculated using the coherence as weight, see Table 9.6 of Random Data by Piersol and Bendat for the formula I'm using) are enormous. Now that I have a good idea that the UGF is between 1 - 15 kHz, I'm going to restrict my frequency band and try to fit just around where the UGF would be. 

--------------------------------------------------------------------------------

To do:

  • Reduce frequency band and take more data
  • Get fit with better standard error, use that error to calculate the uncertainty in the UGF!
Attachment 1: rpi_OLG_2022_08_16_17_00_41.pdf
rpi_OLG_2022_08_16_17_00_41.pdf
Attachment 2: rpi_OLG_2022_08_16_17_01_21.pdf
rpi_OLG_2022_08_16_17_01_21.pdf
  17090   Thu Aug 18 16:35:29 2022 CiciUpdateGeneralUGF linked to optical gain!

TL;DR: When the laser has good lock, the OLTF moves up and the UGF moves over!

-----------------------------------------------------------

Figured out with Paco yesterday that when the laser is locked but kind of weakly (mirrors on the optical table sliiightly out of alignment, for example), we would get a UGF around 5 kHz, but when we had a very strong lock (adjusting the mirrors until the spot was brightest) we would get a UGF around 13-17 kHz. Attached are some plots of us going back and forth (you can kind of tell from the coherence/error that the one with the lower UGF is more weakly locked, too). Error on the plots is propagated using the coherence data (see Bendat and Piersol, Random Data, Table 9.6 for the formula). 

-------------------------------------------------------------

Want to take data next week to quantitatively compare optical gain to UGF!

Attachment 1: rpi_OLG_2022_08_17_18_03_52.pdf
rpi_OLG_2022_08_17_18_03_52.pdf
Attachment 2: rpi_OLG_2022_08_17_18_00_50.pdf
rpi_OLG_2022_08_17_18_00_50.pdf
  17101   Wed Aug 24 10:49:43 2022 CiciUpdateGeneralMeasuring DFD output/X-arm laser PZT TF with Moku

We measured the TF of the X-arm laser PZT using the Moku so we can begin fitting to that data and hopefully creating a digital filter to cancel out PZT resonances. 

-------------------------------------------------------------

We calculated the DFD calibration (V/Hz) using:

Vrf = 0.158 mV (-6 dBm), Km = 1 (K_phi = Km*Vrf), cable length = 45m,  Tau = cable length/(0.67*3*10^8 m/s) ~ 220 ns. 

We've taken some preliminary data and can see the resonances around 200-300 kHz.

---------------------------------------------------------

Next steps are taking more data around the resonances specifically, calibrating the data using the DFD calibration we calculated, and adjusting parameters in our model so we can model the TF.

 

Attachment 1: AUX_PZT_Actuator_nofit.pdf
AUX_PZT_Actuator_nofit.pdf
  17103   Wed Aug 24 16:37:52 2022 CiciUpdateGeneralMore DFD/AUX PZT resonance measurements

Some more measurements of the PZT resonances (now zoomed in!) I'm adjusting parameters on our model to try and fit to it by hand a bit, definitely still needs improvements but not bad for a 2-pole 2-zero fit for now. I don't have a way to get coherence data from the moku yet but I've got a variety of measurements and will hopefully use the standard deviation to try and find a good error prediction...

 

Attachment 1: AUX_PZT_Actuator_narrow_fit.pdf
AUX_PZT_Actuator_narrow_fit.pdf
  17106   Thu Aug 25 16:39:31 2022 CiciUpdateGeneralI have learned the absolute basics of github

I have now added code/data to my github repository. (it's the little victories)

  17107   Fri Aug 26 12:46:07 2022 CiciUpdateGeneralProgress on fitting PZT resonances

Here is an update of how fitting the resonances is going - I've been modifying parameters by hand and seeing the effect on the fit. Still a work in progress. Magnitude is fitting pretty well, phase is very confusing. Attempted vectfit again but I can't constrain the number of poles and zeros with the code I have and I still get a nonsensical output with 20 poles and 20 zeros. Here is a plot with my fit so far, and a zip file with my moku data of the resonances and the code I'm using to plot.

Attachment 1: PZT_fit.zip
Attachment 2: AUX_PZT_Actuator_narrow_fit_1.pdf
AUX_PZT_Actuator_narrow_fit_1.pdf
  17112   Mon Aug 29 18:25:12 2022 CiciUpdateGeneralTaking finer measurements of the actuator transfer function

Took finer measurements of the x-arm aux laser actuator tranfer function (10 kHz - 1 MHz, 1024 pts/decade) using the Moku.

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I took finer measurements using the moku by splitting the measurement into 4 sections (10 - 32 (~10^4.5) kHz, 32 - 100 kHz, 100 - 320 kHz, 320 - 1000 kHz) and then grouping them together. I took 25 measurements of each ( + a bonus in case my counting was off), plotted them in the attached notebook, and calculated/plotted the standard deviation of the magnitude (normalized for DC offset). Could not upload to the ELOG as .pdf, but the pdf's are in the .zip file.

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Next steps are to do the same stdev calculation for phase, which shouldn't take long, and to use the vectfit of this better data to create a PZT inversion filter.

Attachment 1: PZT_TF_fine.png
PZT_TF_fine.png
Attachment 2: PZT_TF_fine_mag_stdev.png
PZT_TF_fine_mag_stdev.png
Attachment 3: ATF_fine.zip
  16993   Tue Jul 12 18:35:31 2022 Cici HannaSummaryGeneralFinding Zeros/Poles With Vectfit

Am still working on using vectfit to find my zeros/poles of a transfer function - now have a more specific project in mind, which is to have a Red Pitaya use the zero/pole data of the transfer function to find the UGF, so we can check what the UGF is at any given time and plot it as a function of time to see if it drifts (hopefully it doesn't). Wrestled with vectfit more on matlab, found out I was converting from dB's incorrectly (should be 10^(dB/20)....) Intend to read a bit of a book by Bendat and Piersol to learn a bit more about how I should be weighting my vectfit. May also check out an algorithm called AAA for fitting instead.

  17006   Fri Jul 15 16:20:16 2022 Cici HannaUpdateGeneralFinding UGF

I have temporarily abandoned vectfit and aaa since I've been pretty unsuccessful with them and I don't need poles/zeroes to find the unity gain frequency. Instead I'm just fitting the transfer function linearly (on a log-log scale). I've found the UGF at about 5.5 kHz right now, using old data - next step is to get the Red Pitaya working so I can take data with that. Also need to move this code from matlab to python. Uncertainty's propagated using the 95% confidence bounds given by the fit, using curvefit - so just from the standard error, and all points are weighted equally. Ideally would like to propagate uncertainty accounting for the coherence data too, but haven't figured out how to do that correctly yet.

 

[UPDATE 7/22/2022: added raw data files]

Attachment 1: UGF_4042.png
UGF_4042.png
Attachment 2: UGF_5650.png
UGF_5650.png
Attachment 3: TFSR785_29-06-2022_114042.txt
# SR785 Measurement - Timestamp: Jun 29 2022 - 11:40:42
# Parameter File: TFSR785template.yml
#---------- Measurement Setup ------------
# Start frequency (Hz) = 100000.000000
# Stop frequency (Hz) = 100.000000
# Number of frequency points = 30
# Excitation amplitude (mV) = 10.000000
# Settling cycles = 5
# Integration cycles = 100
#---------- Measurement Parameters ----------
... 52 more lines ...
Attachment 4: TFSR785_29-06-2022_115650.txt
# SR785 Measurement - Timestamp: Jun 29 2022 - 11:56:50
# Parameter File: TFSR785template.yml
#---------- Measurement Setup ------------
# Start frequency (Hz) = 100000.000000
# Stop frequency (Hz) = 2000.000000
# Number of frequency points = 300
# Excitation amplitude (mV) = 5.000000
# Settling cycles = 5
# Integration cycles = 200
#---------- Measurement Parameters ----------
... 322 more lines ...
  1692   Tue Jun 23 23:14:36 2009 ClaraConfigurationPEMAccelerometers relocated

Both accelerometers have been moved in an attempt to optimize their positions. The MC1 accelerometer was moved from one green bar to the other (I don't know what to call them) at the base of the MC1 and MC3 chambers. That area is pretty tight, as there is an optical table right there, and I did my best to be careful, but if you suspect something has been knocked loose, you might check in that area. The MC2 accelerometer was moved from the horizontal bar down to the metal table on which the MC2 chamber rests.

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