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  SUS Lab eLog, Page 32 of 37  Not logged in ELOG logo
ID Date Author Type Category Subjectup
  121   Thu Feb 28 13:46:16 2008 David YMMiscOMCTip Tilts - Susp. Wire shipped
As per Adam Mullavey's request, I have shipped the remainder of the (cleaned) suspension wire for the tip tilt assemblies to LLO for the out of vacuum tip tilts. Unclean the wire as necessary, as Bob says the bake job is trivial for it.
  108   Wed Dec 19 15:29:14 2007 DmassLaserGeneralTip Tilts Being Baked
The Tip Tilt mirrors are now being baked with Bob. They should be ready in time.

The traveler has DCC #E070354-00-X.

As per Bob's know-how, they are cooking at:
80 C for magnets
200 C for steel;
120 C for the Al, Cu, Bronze, and teflon

  931   Tue Feb 24 12:47:00 2015 GabrieleMiscCrackleTo do list

Here is a list of things we need to do in the next weeks. Red things are important/urgent in my opinion, green things are easy and could be done quickly.

Lab in general

  • in the right corner of the benches, we have some cable trays. We are missing the parts to attach it to the wall. We have to order them 
  • then we should install them on the entire wall opposite to the fume hood (and maybe some small extensions perpendicular to the wall, going to the center of the optical tables, so we can arrange cables to go to the ceiling)
  • we still have to ask the carpenter shop to secure the glass window cabinet to the wall. Let’s do it together with the tray installation. The number to call should be 4717. It's a good idea to do this before the safety inspection, if possible
  • we should bring back all the wire spools we borrowed


  • as Eric suggested, we should move the BS in a more centered position, to make the two arms more equal than now. This should help the alignment. The present BS position is kind of random
  • then we have to realign the Michelson
  • test the new PZT, the circuit should work with this PZT as well. However, I expect a lower resonance, since the mirror si much larger. And the gain might be wrong (change the feedback resistor of the first OP27 to tune it)
  • One of the accelerometers cables is broken. It’s the one sitting on top of the PZT driver on crackle1. 


  • solder components on the cable breakout PCBs and cable the breadboard accordingly (attach the PCB to the breadboard back, connect all cables and secure them to the breadboard). We have to check if the current sent to LED and PDs is enough (maybe we’ll have to connect some of the supplies in parallel, in that case we should check for spurious currents flowing between boards). Test everything again with the new cabling. 
  • Find where the boxes for the electronic are. They disappeared from our lab some weeks ago… If we don’t have them anymore, we’ll have to order some
  • Continue the iterations for the vacuum chamber. We also have to figure out which flanges we have and what we need to order to have the chamber fully operation when it arrives
  • Look at the pump we have in the corner of the lab (close to the fume hood) and see if we can use it (and if the flange is compatible with what we’re getting in the chamber)
  • Figure out what legs we need for the optical table and order them. When we get them we'll have to move crackle1 to the other table and crackle2 to the small table.
  • Continue the alignment of the optical setup, possibly after balancing the two masses so to get them horizontal (figure out the most accurate way to determine if they are horizontal: one way would be to remove M3 and M4, adjust an external mirror to fold the beam as well as possible in vertical and align it back overlapping with the main beam)
  460   Mon Apr 16 16:16:39 2012 Giordon StarkDailyProgressCoating QToday's progress and scans centered at 21.4kHz

At 11:53am - I turned off the turbo pump (it was at 833 Hz) and let it spin down significantly before sealing the chamber. It basically spun down to 0 Hz at 1:34pm (roughly 1.5 hours). I sealed the chamber and then turned off the backing pump. The interesting thing is that the pressure seems to be holding steady at the moment - I recorded it as 2 mTorr at 3pm, and it is currently at 2 mTorr at 4:15pm (at this point, it should around 5 mTorr by now - so somehow, the leaks are probably smaller than before!) I've also replaced the back periscope (closest to the PDs and spectrum analyzer) with a much heavier one.

Given that we're not seeing any signs at all of a mode around this area - I'm running two more good-quality scans; one with the HV on and one with the HV off. Just to convince myself that we can't find it, I'll compare the two scans over this region just to make sure there's no pattern or significant differences.

  • 1kV bias
  • 0.5Vpk sine wave
  • 20.9kHz - 21.9kHz (1kHz span, centered at 21.4kHz)
  • 1600 points/swp
  • 60s average time
  • 3s settle time

Scan with the HV Off and HV On separately:




Nothing super interesting - you do notice some differences, but it seems like these are random (vary by roughly a factor of sqrt(2) - which I assume is probably something like shot noise?). Given the raw data (nohv, hv) - these are computed as follows

  • Difference (first picture [left] below): 20*log10(hv) - 20*log10(nohv)
  • Quotient (second picture [right] below): log10(hv)/log10(nohv)


There are some strong peaks - but nothing really catches my eye much. I'm going to conclude that we are not seeing the mode predicted at 21.4kHz - so we should look into other ways of detecting these modes.

I have also attached the data files (21400NOH == HV Off, 21400HV == HV On) which are column-separated to be imported into matlab or whatever.


Attachment 6: 21400NOH.BOD
 2.090000e+004  1.057931e-004 -1.472176e+002
 2.090061e+004  1.174876e-004  1.490364e+002
 2.090122e+004  1.093557e-004  1.571628e+002
 2.090183e+004  9.780642e-005 -3.710816e+001
 2.090244e+004  7.870543e-005  8.740469e+001
 2.090305e+004  1.691184e-004 -1.066715e+002
 2.090366e+004  7.794011e-005  5.483238e+001
 2.090427e+004  2.161033e-004  1.260183e+002
 2.090488e+004  1.052892e-004 -1.695003e+002
 2.090550e+004  2.729488e-004  3.217617e+001
... 1592 more lines ...
Attachment 7: 21400HV.BOD
 2.090000e+004  1.793278e-004 -3.384179e+001
 2.090061e+004  4.848418e-005 -1.172184e+002
 2.090122e+004  1.120120e-004 -1.346500e+002
 2.090183e+004  1.394507e-004 -1.002642e+002
 2.090244e+004  2.615188e-004 -1.324371e+002
 2.090305e+004  2.105800e-004 -6.654303e+001
 2.090366e+004  5.161508e-005  4.662129e+001
 2.090427e+004  6.781989e-005 -3.900427e+001
 2.090488e+004  1.155157e-004 -8.198375e+001
 2.090550e+004  4.713273e-005 -7.803843e+001
... 1592 more lines ...
  1881   Mon Dec 21 16:35:14 2020 AnchalDailyProgressOpticsTook beam profile of laser right off the head
  • This is a repetition of SUS/1864.
  • Used Data Ray Beam'R2-DD.
  • Took 50 averages and recorded beam "diameters" at 10 different points after the laser head.
  • Configuration file is BeamProfileConfiguration2um.ojf.
  • Used fitBeamWidth function of ala mode to fit X and Y beams separately and then their geometric mean.
  • We'll use the geometric mean as the seed profile for future calculations.


Attachment 1: LaserHeadBeamProfileAvg.pdf
Attachment 2: LaserHeadBeamProfileX.pdf
Attachment 3: LaserHeadBeamProfileY.pdf
  1882   Tue Dec 22 15:54:03 2020 AnchalDailyProgressOpticsTook beam profile of near EOM area
  • After installing a 400mm focal length plano-convex lens at 24" from the laser head at (20, 12), we found that higher-order modes are present in the beam.
  • We installed an iris at 34" from laser head at (17, 5)
  • Configuration file is BeamProfileConfiguration2um.ojf.
  • Used fitBeamWidth function of ala mode to fit X and Y beams separately and then their geometric mean.
  • We'll use the geometric mean as the seed profile for future calculations.
  • Found a beam waist of 306 um at 58" from the laser head.
  • Installing the EOM between 49" and 52" from the laser head where the beam waist is between 1 mm and 740 um.



Attachment 1: BeamProfileNearEOMAvg.pdf
  1877   Wed Dec 16 22:13:43 2020 anchalMiscEquipmentLoanTook delay line box, compressed nitrogen cylinder and lens
  • Took a delay line box DB64 from QIL from the WOPO table. The box was marked Crackle on it.
  • Took the compressed nitrogen cylinder for optics cleaning which was stored in Adaptive Optics lab.
  • Took some lens from the cabinet in Adaptive optics lab.
  • Took some other optics parts like pedestals, posts, lens mount etc.

QIL elog entry: QIL/2524

  1878   Wed Dec 16 22:38:55 2020 KojiMiscEquipmentLoanTook delay line box, compressed nitrogen cylinder and lens

Photos, please, because we don't allow a free-rolling cylinder in a lab.

  1631   Thu Dec 22 02:05:36 2016 XiaoyueDailyProgressCrackleTouching again

After pumping and aligning, I cannot lock the Mich. The fringes are fast. The OSEM readings do not respond instantaneously to table leveling by pumping or leaking the table legs. I suspect a touching issue again. I opened the chamber today and found suspension OSEM C knocked off its centering place. This probably happened when I was closing the chamber. Block #2 magnets X, Y barely touch down. It's a good time to solve this issue too. I shifted the frame #2 downward by ~ 1 mm. I will continue inspection tomorrow.

  951   Thu Apr 2 18:04:05 2015 GabrieleDailyProgressCrackleToward bread board sensing and damping

Today I finished making all the cables needed for the OSEMs that will sense the breadboard motion.

I started to assemble back the horizontal arms in the support structure. However, I discovered that the cable breakout board in the back was conflicting with the horizontal support beam. So I moved the board down as much as possible and secured again all cables. The breadboard is likely not level anymore after this change. Incidentaly, I discovered that although we leveled the breadboard and the intermediate mass, the optical table is not level...

  799   Thu Jun 26 08:48:54 2014 GabrieleDailyProgressCrackleToward stainless steel blades

 Gabriele, Xiaoyue

In the last couple of days we disassembled the crackle 1 setup and started the work to install a pair of stainless steel blades. Since the yield stress of stainless steel is much lower than the one of margin, the old weights were too big. Even removing them completely and using only the mirror assembly structure, we had too much weight. We had a couple of new pieces machined out of aluminum instead of steel and now we have a reasonable weight to pre-stress the blade. We should be around 80% of the yield stress, to be confirmed by a more careful computation.

We also took the opportunity for a rationalization of the cabling. Some of the cables used in the setup were too long and were dangerously hanging close to the beam path. We are tweaking the length of all cables and clamping them down to the optical bench. The old cables were also quite thick and stiff, almost surely causing some seismic shortcut. We are in the middle of the process of building new cables, using thinner wires which should give us a much softer connection.

In the next days we'll continue making the new connections, we'll clean all the mirrors, realign the setup and tune the control system to lock the Michelson interferometer.

  374   Tue Nov 15 15:56:23 2011 MingyuanDailyProgressCrackleTransfer Function of isolation stack

The analysis of the transfer function of isolation stack is attached

Attachment 1: transfer_function_of_isolation_stack.pdf
transfer_function_of_isolation_stack.pdf transfer_function_of_isolation_stack.pdf
  455   Fri Apr 13 20:39:13 2012 Giordon StarkDailyProgressCoating QTransfer Functions, Scans, and Vacuum Depressurization Rate!

[Giordon, Rana, Eric, Zach]

The vacuum chamber was sealed off today at 11:25am (Pressure ~<= 1mTorr) with the HV at 1kV bias - observing that there were no arcs on the ESD. From this point on, detailed observation of the pressure and time were recorded to make the vacuum depressurization plot seen below - it's basically a constant rate of roughly 1 mTorr every 30 minutes (this means that, if we run overnight - we can reasonably expect the chamber to reach 20 mTorr if it is pumped down to 1 mTorr initially).


Below are the transfer functions: all were sampled using a 20 second integration time with a 3 second settling time, with 1000 points. The title of each plot should be mostly descriptive of what the data is.


These seem pretty boring - there might be some peaks (and the SNR is pretty low) or there aren't any peaks and we are either scanning the wrong regions, in the right region but need better resolution, or we can't excite our modes strongly enough.


This last one was to try and find the mode that Rana pointed out at 46.880 kHz (see a previous eLog entry for a picture of the radial and azimuthal stresses from COMSOL). Again, it doesn't seem very interesting.



I'll be in tomorrow and I want to try and higher resolution scan around 24.7 kHz  - it's a gut feeling. I'll keep the chamber at 1 mTorr, run something for a good 5-8 hours, and pump it back down again. The HV bias would be at 1 kV with a 0.5V pk-pk sinusoidal drive.

  1004   Thu Jun 18 13:53:28 2015 SaikanthDailyProgressCrackleTransfer function measurements - with shorter legs

After a number of iterations of recentering and alignment, we finally have a stable setup with no magnets touching the OSEM - blocks or suspension. I ran a measurement the other day, for coil A excitation. Results in the attachments. Some key points:

  1. I have used the same configuration for excitation as described here.
  2. Notice that there are now 2 resonance peaks in SENS_A/COIL_A: which is what one would expect for a double pendulum-like suspension.
  3. The coherence for other sensors is still low. This is not suprising because there is less coupling between orthogonal directions, as one would expect, but it is can pose some problems while fitting poles and zeros.
  4. I haven't used any coherence cut-off in these plots.

I've attached .fig files too, along with .pdf.

Attachment 1: translations_A-exc_new.pdf
Attachment 2: rotations_A-exc_new.pdf
Attachment 3: translations_A-exc.fig
Attachment 4: rotations_A-exc.fig
  1062   Wed Jul 15 16:12:30 2015 GabrieleNoise HuntingCrackleTried to confirm frequency noise hypothesis, found something else

I tried to meaure the noise spectrum and coupling of frequency noise with different positions of the translation stage, or in other words different macroscopic asymmetries in the Michelson.

In brief, I can see a clear trend in the frequency coupling trend, but the change in the noise level is inconclusive.

In particular, the low frequency noise (between 20 and 100 Hz) depends a lot on the alignment. Different positions of the translation stage result in different contrast of the IFO (after finding the optimal alignment). It appears that when the contrast is slighlty worse (90% instead of 95% or 98%), the noise at low frequency gets significantly larger, see attached figure.

So I think the next steps are

  • equalize the Michelson arms by moving some of the folding mirrors within possibly 1-2 mm. Iterate with measurements of frequency noise coupling if needed
  • during this process, ensure that the beams are hitting the center of the end mirrors, as well as possible
  • install the black glass baffles, which are ready, to reduce contamination by scattered

I also had the impression, unconfirmed at 100%, that the glitchiness depends on the alignment state. This might eb due to scattered light.

Attachment 1: frequency_noise_tf.png
Attachment 2: effect_of_contrast.png
  163   Tue Dec 21 06:58:09 2010 ranaThings to BuySeismometryTrillium Noise Plot

Nanometrics has a couple of seismometers which are cheaper than the T240 which may be of interest to us: better than the Guralp CMG-40T, but cheaper and easier to use than the STS-2.


  1192   Fri Aug 28 01:19:09 2015 XiaoyueDailyProgressCrackleTry locking again

I stopped pumping at 9:05 pm, with pressure 130 mTorr. We completely lost fringes. I checked that all magnets were free. Then I realigned but noticed the maximum peak to peak value was lower than before, so I adjuted laser power gain from -3 to 0. After re-alignment the visibility is ~ 99%.

Then I tried to lock Michelson. Lock is good, switching to compensation is good, actuation is not large, but when engaging the boost both noise and excitation is becoming larger. There’s no way to switch to whitening beccause high frequency noise peaks were killing the performance.  Look into spectrum, I saw ring-ups @237.5Hz (1st biggest), 267.5Hz (2nd biggest) and 493 Hz (3rd biggest). So I added notch(237.5, 20, 40), notch(493, 10, 30), and
modified notch(267, 10, 30) to notch(267.5, 10, 30), but it didn't help. I saw glitches in the Mich signals when boost is on, and all damping off.

11:50 pm I blocked the splitted side beam (for the purpose of testing 3mm PD), just wanted to avoid any spurious beam. I tried last lock tonight (pressure 366 mTorr) but the glitches are still there.

12:00 am I turn off the laser.


  1194   Fri Aug 28 11:27:01 2015 GabrieleDailyProgressCrackleTry locking again

Some investigations:

  • Suspension is not touching: I checked that the spectrum of all the suspension shadow sensors are good, see attached plot
  • I saw the same "glitches": they are there even when the boost is off, just more difficult to see them in the time series
  • There is no clear loop instability: the glitches are not oscillations, but rather some intermittent noise below ~100 Hz (they look so much like scattered light shelves)
  • It's not a coild driver problem: I tried to lock using Z1 only or using Z2 only, and the glitches are still there
  • It's not a problem related to one of the two photodiode readouts: I locked using only AP and then only SP (adding an offset) and the glitches are still there
  • I can't see the glitches / low frequency noise in the sum of the two photodiodes, so I guess it's not a laser problem (not conclusive yet)
  • I tried to move the input beam checking the photodiode power, and it seems to me that the AP signal is quite sensitive to the input beam pointing. I have the impression that the range I can move the input beam before starting to lose power on the diode is quite small. Is there any clipping?
  • Rebooting the cymac didn't help
  • There is no suspicious HF content in the photodiode signals: I looked at them right out of the electronic box with a scope, and they look like what we're seeing in the digital world
  • I checked if there is any correlation of those glitches with motion as recorded by any of the shadow sensor. Nothing. So it's not scattered light as we saw in the past, and probably unlikely to be clipping, since we should see some correlation with motions.



Then I tried to lock Michelson. Lock is good, switching to compensation is good, actuation is not large, but when engaging the boost both noise and excitation is becoming larger. There’s no way to switch to whitening beccause high frequency noise peaks were killing the performance.  Look into spectrum, I saw ring-ups @237.5Hz (1st biggest), 267.5Hz (2nd biggest) and 493 Hz (3rd biggest). So I added notch(237.5, 20, 40), notch(493, 10, 30), and
modified notch(267, 10, 30) to notch(267.5, 10, 30), but it didn't help. I saw glitches in the Mich signals when boost is on, and all damping off.



Attachment 1: susp_not_touching.png
  1380   Fri Feb 12 16:55:58 2016 GabrieleDailyProgressCrackleTrying again to balance roll

I mounted a series of posts to be able to precisely fix the board in a vertical position. I'm using a plumb-line to estimate the veritical position of the board. Here the procedure I tried, without success

  1. use the posts and clamps to fix the board in a perfectly vertical position
  2. check that the blocks, when free, are not touching and centered on the OSEMs
  3. clamp the blocks as close as possible to the optimal position
  4. release the board and balance it with small weights until it's vertical
  5. release the blocks
  6. since the board moves with the blocks, try again to fine tune the balancing.

Step 6 always fails, since at least one of the blocks ends up touching, and the board is never stable in a vertical position with the blocks free. 

  1582   Tue Jul 19 20:35:00 2016 XiaoyueDailyProgressCrackleTrying to diagnose for the plateau noise

[Seiji, Xiaoyue] Today we focus on trying to diagnose for the source of the plateau noise. We first suspected saturation. Although we didn't see any saturation in the oscillosope we further reduced the power to 1/2, 1/4 of the original non-saturated power by adjusting laser current, re-lock the Michelson with ~2X, ~4X filter gain to keep the ~66 Hz UGF. We didn't see any change in the plateau structure, the sensitivity kept getting worse. One thing we noticed is, the digital AP/SP outputs are badly saturated at the maximum of the fringes -- we were under-estimating the optical gain by factor of ~ 2. We also tried reducing the input beam power by rotating the wave plate before BS. With 1/4 power the sensitivity is again worse than original configuration, but better than 1/4 power achieved by adjusting laser power. In all cases, plateau structure doesn't change. We also checked that the plateau structure is there in non-calibrated error signal and in close-loop transfer function. I would like to take a further look into the calibration tomorrow.

  1289   Fri Oct 2 18:15:33 2015 GabrieleDailyProgressCrackleTrying to keep suspension damping on

I'm leaving the Michelson locked, with all suspension damping loops on with a gain of 0.01 (nominal is 1). Even with this low gain the loops are injecting some noise.

I'm leaving them like this for a while, to see if it improves the scattered light problem.  

  1290   Fri Oct 2 20:30:23 2015 GabrieleDailyProgressCrackleTrying to keep suspension damping on

No significant difference...


I'm leaving the Michelson locked, with all suspension damping loops on with a gain of 0.01 (nominal is 1). Even with this low gain the loops are injecting some noise.

I'm leaving them like this for a while, to see if it improves the scattered light problem.  


  1739   Thu Jul 20 23:56:39 2017 XiaoyueDailyProgressCrackleTrying to recover free configuration

I recovered the michelson alignment without much effort, but the 'touching' issue remains. The block OSEM spectrum in air (Elog 1733) shows some sharp resonance peaks but the block motions are in general noisier than the former reference free configuration with maraging steel blades (Elog 1670). Also, the Z-motion below 0.2 Hz is similar as the X- and Y-'s. 

I inspected the setup carefully but found nowhere touching.. The only suspected part is Y2 magnet that could touch up, so I recentered the magnet position by moving it downward. Nothing changed. I suspected that a bad table leveling cause problem, because when we open the chamber the center of mass changed quite a lot. However, after leveling the table, nothing changed. I am confused what could cause the spectral difference. Is it really a touching problem? If so, what is touched??...

  1787   Tue Feb 19 18:11:43 2019 DuoDailyProgress Tuesday report

Some clean up work on the noisemon is done.

1. Added compensate capacitor.

2. Added mounting holes.

3. Added DCC number. https://dcc.ligo.org/LIGO-D1900052

4. Renumbered the components.

5. Added 0 ohm resistor between power ground and signal ground.

6. Added more test points for the voltage monitor and current monitor.

7. Increased schematics font size.

Next I will create the Bill Of Materials. I need to assemble the manufacturer information and put meaningful and consistent descriptions for the components.

Attachment 1: noisemon.pdf
noisemon.pdf noisemon.pdf noisemon.pdf
  1871   Thu Dec 3 12:20:19 2020 AnchalSummaryElectronicsTuned and characterized EOM Driver for 37 MHz phase modulation

Measurement details:

  • Connected New Focus 4004 broadband IR phase modulator to the output of the SN06 EOM driver.
  • Splitted R output of AG4395A. One end went to the input of SN06 EOM driver.
  • The other end goes to input R of Ag4395A.
  • The RFMon of the driver is fed to input A of AG4395A.
  • Used a tuning stick for the coilcraft inductor to tune the resonance peak to 36 MHz.
  • Took measurements with the configuration files in this directory.


Attachment 1: EOMDriver_TF_Inp_to_RFMon_CloseUp_03-12-2020_121040.pdf
Attachment 2: EOMDriver_TF_Inp_to_RFMon_Wide_03-12-2020_120819.pdf
  531   Fri May 25 14:44:47 2012 ZachMiscCoating QTurbopump borrowed for gyro

I borrowed the Hi-Cube turbo to pump down the gyro chamber. I turned off the large turbo and sealed the tank, and it seemed to still be below 1 uTorr after ~15 mins, so the leak rate is reasonable.

I will replace it before the end of the day.

  797   Wed Jun 18 16:46:13 2014 GabrieleDailyProgressCrackleTweaking the locking loop

Carell, Horng Sheng, Xiaoyue, Gabriele

The autolocker was not working reliably. We measured the open loop transfer function and found that the unity gain frequency was too low (95 Hz instead of 120 Hz). We increased the gain in the servo loop, and now the autolocker works at every attempt.


Attachment 1: open_loop_tf_june18th.pdf
  1839   Mon Dec 9 22:06:19 2019 DuoDailyProgress Two boards tested

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

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

1. Diaggui gives "unable to start excitation".

Solution: restart diaggui

2. Drive signal does not go in

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

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

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

  1281   Thu Oct 1 17:29:35 2015 FedericoDailyProgressCrackleTwo channels amplifier for coil current measurement

[Federico. Gabriele]


We have settled-up a relatively low noise, two channels, 10x instrumentation amplifier able to sense the current sent to the interferometer coils with an intrinsic noise lower than the one produced by the DAC driving the coils.

With this circuit it will be possible to analyze and correlate the real driving signals. We’ll be able to directly measure the actuation noise (DAC or coil driver) and more important, to track if this noise changes with the low frequency signal. The latter possibility is particularly dangerous, since it would mimic the crackling noise signal we are trying to detect.

Input referred noise is about 15nV/sqrt(Hz) from 10Hz and above.

A caveat is that inputs are floating, with no reference to ground or to the power supply.

This circuit can be used only if its ground is the same of the circuit where it is connected (e.g. the power supply is derived from the circuit to be measured, or at least they have a common ground path).

Input filtering is useful only to prevent that High-Frequency unwanted signals reach the differential IC inputs (a typical example is packeting from a cell phone).

  249   Thu Jul 21 23:09:02 2011 Larisa ThorneDailyProgressCrackleUPDATE: experiment setup

 [Seiji, Larisa]

Seiji and I went down to the labroom to start working on the setup. What we put together obviously isn't the final version (see super sketchy pictures below), but it was enough to begin measuring the transfer function of a "one-armed Michelson configuration with the magnetic actuator driving the blade spring." We did not record any of the data gathered, as it was only a test/preliminary run. A final version will be run tomorrow afternoon, and I will publish the results thereof.


So for now, content yourselves with pictures of the experiment thus far.

Attachment 1: IMG_2014.JPG
Attachment 2: IMG_2016.JPG
Attachment 3: IMG_2017.jpg
Attachment 4: IMG_2019.JPG
Attachment 5: IMG_2015.JPG
Attachment 6: IMG_2020.JPG
  1875   Fri Dec 11 17:53:07 2020 PacoDailyProgressElectronicsUPDH box alternative power supply

Today, after struggling to find a 4-pin circular power supply cable for the UPDH box (still interested btw) punched a hole for connec power connector in the back panel and found an appropriate cable. See attached photo. Intended for +- 15 VDC.

Attachment 1: connec_pdhsupply.jpg
  1902   Wed Feb 17 11:56:48 2021 PacoLab InfrastructureElectronicsUPDH box zero model and SR560 "lock"

UPDHv3 box (serial 17142) is bogus. While retrieving values of some of the components to plug into working zero model, saw the VGA stage is bypassed by a previously unnoticed hack. Verified this by taking TF and not seeing any changes with respect to the gain knob (shown below are zero's model TFs suggesting a tunable UGF from ~ 10 Hz to 1 kHz), so this box is not good for a standalone servo.

As suggested a few meetings ago, made a quick and dirty lock using a single SR560 and took measurement of something* CLTF (SR560 gain = 10) below. New goal is to find a decent replacement, for which decided to use RedPitaya's python API "pyRPL". Just using the GUI out of the box can also lock the cavity relatively quickly but neither method results in longer than 1 minute lock... so took one step back to polish the pdh error signal.

* Something = Use SR785 TF measurement with source on Ch1, and to B input in SR560. The SR560 in (A-B) mode, and demodulated signal connected to A. The loop was closed with the SR560 output driving the PZT, and Ch2 of SR785. Wouldn't call this CLTF...

Attachment 1: updhv3_VGA_gain.pdf
Attachment 2: SR560_OLTFSR785_17-02-2021_164500.pdf
  1570   Thu Jul 7 17:25:44 2016 DanielleDailyProgressCrackleUncertainty analysis for microphone calibration

To improve the accuracy of the data obtained, a ruler was added for scale in the plane of the ball bouncing. A white ruler was used but interfered with the motion-tracking analysis and was later replaced with a silver ruler. With the improved scale, the acceleration due to gravity is measured between -9.880 m/s^2 and -9.676 m/s^2. This falls between a 0.1% error and an 8% error on the measured acceleration due to gravity in Los Angeles: -9.796 m/s^2.



Additionally, the MATLAB code was further developed by adding plots of acceleration over time and plots of the residuals from the parabolic fits for the initial drop and first bounce. The plot of the residuals seems randomly distributed for the first drop meanwhile there is a clear pattern in the residuals for the first bounce. However, both have low standard errors. The standard error on the parabolic fit for the first bounce in one video is 6.3847 x 10^-04. Time permitting, I can run a chi-squares goodness of fit test on the models to see if the parabola is an acceptable model. Additionally, an important next step is to factor in expected losses due to friction and see how this influences the model.


Rough initial calculations estimate the energy lost in the first bounce to be about one third of the initial potential energy. More specifically, the ball was dropped with an initial potential energy of about 6.12 x 10^-3 Joules and lost about 2.87  x 10^-3 Joules in the first bounce where loss is calculated from the change in kinetic energy. I will repeat these calculations more rigorously as a next step.

The newest, and incresingly long, MATLAB script is attached.

Attachment 4: motion5.m
% I am using the base of this code courtesy of
% Vibhutesh Kumar Singh for digital iVision Lab
% I added comments to any of my own code added to
% the original.

close all;
clear all;

% Set empty matrices for storing motion data
... 247 more lines ...
  1592   Wed Jul 27 16:59:58 2016 DanielleDailyProgressCrackleUncertainty in motion-tracking code for microphone calibration

One source of uncertainty in the microphone calibration experiment is the ability of the MATLAB script to motion track the ball accurately. A small experiment was set up in order to test the precision of the code based on the fact that no change in position should be measured in a stationary ball. Because the code will not motion track an object that is stationary for the entire video, each trial consisted of a ball rolling until it stops, and only the stop is analyzed.

The uncertainty in position is calculated by finding the RMS of the data from the average position, which approximates the actual position. For the trial shown above, the RMS is 4.358 x 10^-5 m. Three trials have been analyzed so far, all with RMS values on the order of 10^-5 m. I will take more trials and average them to get an estimate for this source of uncertainty. 

  1375   Tue Feb 9 20:44:30 2016 XiaoyueDailyProgressCrackleUni-thickness low-resonance highCS blade design

I tested two ~0.82 mm thickness blades A5 R0~140 mm and A6 R0~130 mm. The result is as predicted by the former elog. For blades with small pre-curvature difference the deformation curves almost overlap each other. Note the current flat-position value is obtained by clamping the blades on table and measure the distance from the tip holes to table.

Comparing the loading curves taken from A2, A5 we see that we can achieve a set of loading states from ~93% to ~52% by pre-curving the 0.82 mm blades with progressively increasing initial deflection (equivalent to the flat-position extension distance) from ~33 mm to ~41 mm using the work-hardening trick described by Elog 1364: the yielding point of the blade is continuously re-defined by the maximum plastic load, and the flat-position load value can be found as the intersection of the final unloading curve with the vertical line marking the flat-position deflection. We can achieve the same flat-position load for differently pre-curved blades.

Now I am running out of all testing blades. I am going to order more 0.82mm thickness AISI1074 spring steel strips and machine ~ ((4 test blades + 2 sample blades) / load state) * (4 load states)  = 24 blades for highCS sample blades production.

  1795   Wed Jul 17 13:35:02 2019 DuoDailyProgress Unknown issue

I connected the DAC to ADC direclty (picture 1) and send a sine signal into the DAC. However, I did not get the sine signal back from the ADC. I sent the signal in X1:CRY-DITHER_W_MOD_EXC, channel 9 of DAC and expect the signal from X1:CRY-E_REFLDC_IN1, channel 16 of ADC. However, picture 2 shows what I get: a constant signal around 4400 counts.

Attachment 1: image1.jpeg
Attachment 2: Screenshot_from_2019-07-17_13-34-29.png
  1013   Wed Jun 24 23:08:08 2015 SaikanthSummaryCrackleUnsuccessful attempts to automate parallel TF measurements

Over the last week, I have been trying to find out ways to make parallel measurements of transfer functions (TF's) for different coil excitations. The way I've been doing it so far, it takes about 6-8hrs per measurement, and 6 such measurements - which is a week's time! Things would be much more efficient if I could take all measurements in, say, a night.

Fortunately, that's possible with our system - simply because it is a linear system. Why is it a linear system? Because Newton's laws - which govern the behaviour of our system - are linear!


As long as the system is not excited by the same frequency through different coils, because of linearity, the measurements should be as good as they were taken independently. The difficult part, however, is to find out how to do it.

I have been suggested a couple of methods to make parallel DTT measurements.

  1. Commands on a control room workstation - which is not possible (or easy?), because ours is not a control room.
  2. Use Python-MATLAB to run DTT measurements. People at LLO, LHO etc. have done this before, and I've tried working on their codes. However, there seem to be issues with the Python-MATLAB interface. We couldn't get Python XML parsing working the way it should be. Until we happen to find a solution for this, it wouldn't be possible to automate parallel DTT measurements.

As a result, I've had to come down to the manual mode of operation. Some details mentioned here.

  575   Fri Sep 28 17:05:39 2012 ericqDailyProgressCrackleUpdate

 Broke a few fibers recently, today I glued in our last one. 

Replacing the acrylic flange with a metal one, and getting a new L-shaped O-ring for the lid let us get down to 46 mTorr, by far our current best. 

However, we don't yet know how this affects our noise levels, since we cannot lock. My current suspicion is unwanted vibration modes in the blade+mass systems. When I engage the servo, I see oscillations at the scale of the fringe-to-fringe voltage at ~5Hz, in between the moments when it's swinging between fringes. This, along with the "cleft" at around the same frequency in the blade transfer function measurements made via shadow sensor, suggests non-vertical shenanigans that we can't actuate on / control. 

The steps I want to take to hopefully mitigate this will be:

  • Adjusting the masses so that they are hanging as horizontally as possible during equilibrium (which is far from the case for one of the pair). 
  • Adjusting the steering mirrors below the masses to ensure the laser beam is reflected vertically. (Dmass also suggested using a "corner cube" for this kind of thing, looks like these are three mirrors which are arranged to reflect a beam back to the source, insensitive to incoming angle to a certain degree)
  • If I can find out specifically what the motion causing problems is, might it be possible to mechanically prohibit it? I've poked at the masses in various ways, but have yet to find a mode which looks like the right frequency, but my eyes are probably not the best tool for this...

Also, in the recent past, we have talked about redesigning the experiment slightly; namely mounting both blades on one single post. This would save room in our cramped little chamber and make it easier to align, as well as potentially reducing coupling of the masses (though not 100% sure about this).

Other things that are forthcoming:

  • Finishing up the resistor bridge stuff (Need to compare to values in Frank's thesis, test other materials)
  • Our noise budget needs a fair amount of work, part of which is working out the details of the Michelson's common mode rejection.


  595   Wed Oct 24 16:27:24 2012 ericqDailyProgressCrackleUpdate

Modifications to the servo circuit made locking a bit quieter/stabler. 

I am currently taking data with a common mode, 1V .125Hz drive to attempt to set upper limits on blade tip motion, in the same manner as the resistor crackle work. I should have something analyzed by the end of tomorrow. 

Here's the state of the servo: 

Oct24TF.pdf circuit.png

Just realized I forgot axis labels, oops. X is Freq in Hz, y for top is Mag (db), y for bottom is Phase (deg), as usual. There is a factor 3 gain after the portion of the circuit pictured. 

This resulted in the following spectrum in the PD signal, for the same fringe-to-fringe voltage.


  596   Thu Oct 25 11:04:49 2012 ericqDailyProgressCrackleUpdate


I am currently taking data with a common mode, 1V .125Hz drive to attempt to set upper limits on blade tip motion, in the same manner as the resistor crackle work. I should have something analyzed by the end of tomorrow. 

Turns out I was only recording one channel, and the drive at that. Taking properly recorded data now...

  638   Thu Jun 6 19:22:33 2013 ericqDailyProgressCrackleUpdate

 Added the old Dan Chen / Mingyuan / Valera performance to the noise budget plot. Through contact with Dan, I corrected their loop gain correction. They were touching the laser intensity noise / shot noise of that arrangement occasionally above ~80Hz or so (see ELOG 344), whereas I don't for some reason (the current shot/intensity noise is quite lower from increased power, and isolated laser/fiber). They also were using passive damping (rubber blocks at the clamping points and magnets for eddy current damping), in contrast to the current shadow sensor damping. 


In other news, I've finished the fiber feedthrough for one of the small flanges, and made a little NIM interface box to get BNCs/Picomotor/Power into a 25pin Dsub connector to feedthrough into the chamber. I just need to finish the in vacuum wiring and then I can pump down. 

  577   Thu Oct 4 11:34:03 2012 HaixingSummarySUSUpdate on Maglev

Here I give an update on the current status of the maglev project.


The setup:

The solidworks schematics (false-colored) for the setup is shown by the figure below, from top to bottom:


  1. Top fixed plate (in gray): It is used to mount the coil bobbins and also three linear DC motors (not shown in this schematics) for pushing the floating plate to the working position.
  2. Six coil bobbin (white cylinder): Three of coils (in red-orange) are for counteracting the DC mismatch of the magnets; the other are for controlling the vertical motion of the floating plate. On the bottom of each coil bobbin, there is a magnet which attracts the magnet mounted on the floating plate [mentioned later]. In the hollow center of the bobbin, there is the hall-effect sensor which has a large linear dynamical range and is for acquiring first-stage locking of the floating plate before switching to the short-range optical-lever sensing.
  3. Floating plate (in green): This is the central part of the setup and there are six magnets mounted on the plate (push-fit). We want to levitate it and lock it around the local extrema of the magnetic force between the magnets on the bobbin and on the floating plate, which ideally would have a very low rigidity and achieve a low resonant frequency levitation (for seismic isolation).
  4. Corner reflector (in gold): There are three corner reflectors, and together with the laser form the optical lever to sense the six degrees of freedom of the floating plate. The sensing of different DOFs are coupled to each other, and we need to diagonalize the sensing matrix. This is also where the long-range hall-effect sensing comes into play and it allows us to first lock the floating plate, and we can then diagnose the coupling for the optical-lever sensing.
  5. Small-coil bobbins (small white cylinder): These are for the first-stage sensing and controlling the horizontal motion of the floating plate before switching to the optical-lever sensing. In each of them, there is also a hall-effect sensor.
  6. Collimator  (on the gray mirror mount): This is to fix the optical fiber for the 635nm laser light, which is part of the optical-lever sensing mentioned earlier.
  7. Mirror (on the green mirror mount): In the next-stage experiment, this will be one of the mirror for the Fabry-Perot cavity. On the side of the mirror, we have mounted two small magnets, which are for sensing and controlling the angular degree of freedom of the floating plate.
  8. Middle fixed plate (in between the poles): This plate is to mount the two small-coil bobbins (for sensing and controling the angular DOF). In addition, there are three linear DC motors (not shown in this schematics) mounted on this plate, together with the three DC motors mounted on the top fixed plate, we can place the floating place to be near the working position and also prevent the floating plate stuck to the magnets (very strong) on the coil bobbins.
  9. Quadrant photo-diode (QPD) box (in blue on the bottom fixed plate): In each of box, there is a QPD which is to sense the reflected laser light from the corner reflector on the floating plate. We are using Hamamatsu 4-element photodiode S4349 . Together with the corner reflectors, they form the short-range optical-lever sensing.

Current status:


  1. Mechanical parts: There are two parts not yet ready: the small bobbins and auxiliary components attached on the linear DC motors, due to later modifications to the earlier design; all the other parts are in place. The coil bobbins are now winded with coils.
  2. Optical parts: Apart from the mirror mounts, the main components Laser diode: LPS-635-FC - 635 nm, 2.5 mW, A Pin Code, SM Fiber-Pigtailed Laser Diode, FC/PC; Diode mount: TCLDM9 - TE-Cooled Mount For 5.6 & 9 mm Lasers;  Driver: LDC201CU - Benchtop LD Current Controller, ±100 mA; Coupler (for splitting): FCQ632-FC - 1x4 SM Coupler, 632 nm, 25:25:25:25 Split, FC/PC; Collimator: F280SMA-B - 633 nm, f = 18.24 mm, NA = 0.15 SMA Fiber Collimation Pkg; Collimator adapter: AD11NT - Ø1" (Ø25.4 mm) Unthreaded Adapter for Ø11 mm Collimators are now ready.
  3. Analogy Electronic parts: The pcb boards for the hall-effect sensors and QPD box have been fabricated, and now need to be stuffed. The coil drivers are not yet ready.
  4. Digital parts: The binary input-output box has not yet powered up. The pcb board for the chassis power just arrived, and needs to be stuffed. Rana and I worked out the schematics for AA/AI but not yet the pcb layout.

Plan (Assembly stage):


  1. Mechanical parts: The small bobbins and auxiliary components for the linear DC motors need to be fabricated. The lead time is around three to four weeks. During this period, I will mostly work on the the electronics and also try to get the digital part ready (for this I need helps from Rana and Jamie). In addition, I will design a closure for covering the setup to reduce some noise from the air and acoustics.
  2. Optical parts: I plan to work on them once I finish the electronics. The tasks are: (i) designing the optical layout; (ii) test and diagnose different components, especially the laser diode.
  3. Electronics: I will mostly focus on this part in the near term: (i) stuffing the pcb board for the hall-effect sensors and QPD box; (ii) modifying the old coil driver circuits to accommodate this new setup with more input and outputs; (iii) powering up the Binary input-output box and test it for prototyping; (iv) working together with Rana and Jamie on the AA/AI.
  4. Digital part: This would heavily rely on the help of Jamie and Rana.


Plan (Testing stage):


  1. Acquiring lock of the floating plate by using the hall effect sensors. This is relatively easy compared with the optical-lever sensing and control, as different degrees of freedom are not coupled strongly.
  2. Characterizing the cross coupling among different degrees of freedom in the optical-lever sensing scheme.
  3. Measuring the resonant frequency of the levitation, and testing the tunability of this resonant frequency by locking the plate at different locations to see how low we can achieve.



  768   Fri Dec 20 18:09:56 2013 ericqDailyProgressCrackleUpdate on current Activities
We've now run the experiment for two weekends. In each, there isn't much sign of 2F or 4F power. However, the 1F I quadrature portion of each run has some suggestive shapes for part of the measurement time. If we include the static loading force of the mass as part of the force in our model for crackle modulating the spring constant of the blades, we do indeed get a 1F I signal. However, the two data runs seem to show opposite signs (i.e. phases) for the extra power. I'm looking further into this.

Right now, we have the experiment running for a longer period in an undriven state, for a few reasons.

First, we want to revisit the coherence of accelerometers on the optical table with the error signal. (A quick observation was made today, now that the blades are parallel, the lateral seismic motion along the line of the blades couples in much more strongly than the orthogonal motion, presumably since the twisting motion of the blades is stiffer than a swinging motion).

Second, Gabriele has been writing some analysis code that takes a slightly different approach, namely looking at periodic variations of individual error signal PSD bins. (We call it a "double fft") This is mathematically equivalent, but has the advantage of looking at all frequencies at once, rather than just the power in one bandpassed bandwidth. (The advantage of the bandpass method is the freedom to select a very specific bandwidth, whereas in the double fft, you are limited by the fact that you need to balance the resolutions of each fft). We will use the undriven data as a source of "background noise", to then inject simulated crackle and make sure that both analyses agree and get the right result.

We also recently spoke with Prof. Greer about our desire for a micromechanical model that may help give noise level predictions. She assigned some reading, and we have started attempting to learn the lingo of dislocations in solids.
  1564   Tue Jun 21 21:25:53 2016 XiaoyueSummaryCrackleUpdate on micromechanical investigations

I gave a presentation on the recent progress on micromechanical investigations for crackling noise: 

I applied AC load perturbation (DMA) to quasi-static compressive loading on single crystalline Cu nano-pillars with diameters of 500 nm and demodulate for dynamic moduli at frequencies from 0.1 to 10 Hz under the progressively higher static loads. By tracking the collective aspects of the oscillatory stress-strain time series, we observe an evolving dissipative component of the dislocation network response that signifies a smooth transition from perfect elasticity to avalanche yielding. 

We postulate that the rate-dependent dissipation is due to microplasticity associated to dislocation avalanche combined with slow viscoplastic relaxations, based on which we perform mesoscopic simulations and obtain response in well agreement with experiment. By analyzing the noise-free simulation results, we can predict for the statistics of microplasticity events before avalanche yielding.

The slides are uploaded to LIGO document G1601391-v1.

  1783   Sun Jan 20 16:00:37 2019 DuoDailyProgress Update on the noisemon board

Two more oscillations problems are resolved, and there is no more oscillations. In the time series (the inputs are terminated), we see only the 60Hz noise.

- Some big bypass capacitors are used to regulate the power.

- A small capacitor is attached to the negative feedback loop in the second HP filter.

New board/components arrived. I will assemble and test them immediately.

Attachment 1: TF_20-01-2019_155018_Spectrum.pdf
Attachment 2: TF_20-01-2019_155018.txt
# SR785 Measurement - Timestamp: Jan 20 2019 - 15:50:18
#---------- Measurement Setup ------------
# Start frequency (Hz) = 5.000000
# Stop frequency (Hz) = 1000.000000
# Number of frequency points = 200
# Excitation amplitude (mV) = 10.000000
# Settling cycles = 1
# Integration cycles = 10
#---------- Measurement Parameters ----------
# Measurement Group:  "Swept Sine" "Swept Sine"
... 220 more lines ...
Attachment 3: noisespectrum_20-01-2019_150429_Spectrum.pdf
Attachment 4: noisespectrum_20-01-2019_150429.txt
# SR785 Measurement - Timestamp: Jan 20 2019 - 15:04:29
#---------- Measurement Setup ------------
# Start Frequency (Hz): 0.000000
# Frequency Span (Hz): 1600.000000
# Frequency Resolution: 400
# Number of Averages: 100
# Averaging Mode: RMS
# Window function: BMH
#---------- Measurement Parameters ----------
# Measurement Group:  "FFT" "FFT"
... 420 more lines ...
Attachment 5: TimeSeries.jpg
  1784   Fri Feb 1 12:35:13 2019 not DuoDailyProgress Update on the noisemon board

Duo's noisemon has been in the EE shop/cryo lab for testing.  It is a drop-in replacement for the existing monitor board, including both noisemon and Vmon/Imon/RMSmon circuits for all four channels.

Duo is still working on a log entry summarizing the performance of the new board vs simulation.  This entry shows some measurements of the performance of the new board vs the old board.


  1. Transfer functions of the new noisemon board, in coil driver state 1.
  2. Noise spectra of the new noisemon board, in coil driver state 1, with and without DAC noise input.
  3. Transfer function of an old noisemon board, in coil driver state 1.
  4. Noise spectra of an old noisemon board, in coil driver state 1, with (REF traces) and without (live traces) DAC noise input.
Attachment 1: new_noisemon_tf.png
Attachment 2: new_noisemon_spectra.png
Attachment 3: old_noisemon_tf.png
Attachment 4: old_noisemon_spectra.png
  637   Tue Jun 4 17:33:00 2013 ericqDailyProgressCrackleUpdated Budget

Updated the noise budget with current performance. Increased the gain on the PDs to get the dark noise under the shot noise. Measured each arm's intensity noise, added in quadrature. Measured servo noise by terminating both PD inputs on the NIM box. Estimated vertical seismic noise by some old seismometer data, estimates of the stack frequencies and known blade TFs. (Haven't accounted for horizontal seismic motion at all; blades are oriented differently, have swinging modes, etc.)


  383   Wed Jan 25 17:05:55 2012 ericqDailyProgressCrackleUpdated Circuit Schematic

 Here's the latest schematic for the control circuit. There are some unspecified component values, mostly because I haven't decided on the frequency cutoff and gain of the shadow sensor signal. Also, I hope to have corrected some problems Koji pointed out with the way the signals are added before being sent to the actuators. 

Attachment 1: circuit.pdf
  384   Wed Jan 25 20:15:38 2012 KojiDailyProgressCrackleUpdated Circuit Schematic

It is much nicer now. At least this looks mathematically correct. Here are a few comments.

I rather like to have symmetric design for the actuators while adding an inverter (G=-1 amp) in one of the servo paths.
In this way the summing gains are always correct no matter how you connect/disconnect the paths for the lock-in and damping.

It'd be nicer to have the gain knobs for the damping paths so that you can play with the damping gains.
Also Having a switch between each damping path and the summing point ensures the perfect decoupling of the noisy damping paths.

In general, it is always preferable if the signal in the diagram flows from left to right.

  784   Tue Apr 15 18:23:13 2014 GabrieleSummaryCrackleUpdated Crackle2 design

 Here is a less-temporarily final version of the optical and mechanical layout for the crackle2 experiment.

The eAssembly file is attached, so you can review it and give feedback if you have any.


Attachment 1: FullAssemblyNew_14_04_14.easm
Attachment 2: Rendering1.JPG
Attachment 3: Rendering2.JPG
Attachment 4: Rendering3.JPG
Attachment 5: Rendering4.JPG
ELOG V3.1.3-