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ID Date Author Type Categoryup Subject
  164   Fri Dec 31 15:23:50 2010 ranaMiscCreakNew Creak doc

I have updated the Creak doc (T0900167) in the DCC.

To get started, I think I can just disassemble the long range, polarization using Michelson project from the SURF project.

For the first version with blades, I'm going to just use some shim stock from McMaster: I'll try aluminum and carbon steel since they should creak.

  165   Tue Jan 4 23:29:22 2011 ranaMiscCreakStarted Creak-MICH

Zach, Rana

We grabbed the old quasi-EUCLID HeNe setup from the 40m's SP table and brought some of the parts over to the SUS lab (where Alastair's fibers and the Cryo people are).

We have a single blade spring set up in the Y arm of the michelson. We have aligned it for maximum contrast by eye. We also made sure to keep the REFL beam from going back into the laser.

We experimented with a couple of glues to see what worked. In the end we have attached a junky, mostly-reflective, silvered mirror using super glue to the tip of the blade.

Tomorrow morning Zach is going to use the cast-off PZT stacks that we got from Vass and see if they can be used (word is that they're (AE0203D04F - Piezoelectric Actuator, Max Displacement 4.6 µm, 3.5 x 4.5 x 5 mm).The spec sheet says that it takes a maximum of 150 V to give a 4 micron displacement (enough for us). They also say that the PZT will fail quickly if reverse biased at all or put in a high humidity environment.

For our first trick, we're going to just drive one arm of the interferometer and measure the signal with the old analog lockin amp. Next, we are thinking to use the purple box as the DAQ to do more sophisticated things.

  166   Thu Jan 6 01:03:24 2011 ZachDailyProgressCreakPZT installed/tested

  I rigged up a way to use the small ThorLabs PZTs we took from the 40m yesterday. After an hour or so of going back and forth from the ATF to the SUS lab with random optical hardware to find something suitable, I finally found a solution using one of the fancy translation stages we have for the eventual gyro modematching. Here's a shot of the whole assembly:

That was just to find a way to mount to the magnetic base we are using; I still needed a way to actually hold the PZT and connect it to the mirror on the shim "blade". We knew we wanted to have something give-y like rubber between the PZT and the blade itself to suppress high-frequency noise in the actuator, so I found a piece of rubber grommet to do the trick. The grommet had a hole in it, of course, so I wrapped it in a piece of shrinkwrap so that I could glue it along the flatter surface to the PZT. On the other end, I needed something firm attached to the PZT with which to hold it (gripping the PZT itself might damage it and in any case would reduce the range of motion). I chose to use a polyester film capacitor---with the leads trimmed---and glued it to the other side. Here is a closeup:
This thing is supposed to put out 4.5 um with 150 V applied, so I figured I could get a decent signal using a drive on the order of 5-10 V (since we are using 633-nm light, this is on the order of a fringe). I installed a PDA100A at the AS port of the interferometer and realigned the beams from both arms to overlap. The manufacturer warns never to reverse the polarity of the PZT leads, so I applied a ~6 Vpp drive with an offset of +5V. I could clearly see an output coherent with the drive on the scope over a wide range of frequencies. I decided to plug it into the Agilent and look at the spectrum. Here is an example of one with a 3-Hz drive signal. There is a lot of upconversion because the mirror is swinging through a couple of fringes. I was able to change the overtone structure by adjusting the drive amplitude and offset (so that it stayed roughly linear).
For the heck of it, I thought I might try and measure a transfer function from the PZT to the PD signal. It can be seen below. Even with maximum integration, the ambient noise is very high at the moment, and turning up the drive doesn't help since the thing quickly loses linearity, but to the naked eye the TF looks roughly like what one would expect from a driven pendulum with a resonance somewhere around 100-200 Hz. Rana and I noticed that the simple system with the shim clamped to the base and the mirror glued to its top had a fairly high Q, but the thing is now damped by the rubber contact, so the resonance is not very evident in the TF.
From these very simple trials, I would guess that these PZTs will work quite nicely once we can close the loop and operate at the dark fringe. I have unfastened the second unit from the mirror on which we found them, and I will try and put a new wire on the ground lead tomorrow so that we can test it.
  167   Thu Jan 6 21:58:12 2011 ZachDailyProgressCreakSecond mirror/PZT installed, rough CMRR measured

 After yesterday's success with the PZT we scavenged from the Drever cabinets, I decided to repair the second one and make a duplicate mirror assembly. It isn't quite as pretty as the last one since I had to solder it (so I won't show a closeup), but all in all it came out pretty well. I used the other shim that matched the one we used for the first mirror, and glued the fully-silvered mirror that bore the PZTs to the top of it. (I later found out that Rana put the new shim stock on my desk, but we will use the stuff that's in place now until we get some kinks worked out. In any case, we have yet to use any nice 5101 mirrors.) I also installed a beam dump to block the second ghost beam from hitting the PD. Here is a shot of the second mirror assembly and another of the full setup:

2011-01-06_18.52.51.jpg 2011-01-06_18.52.33.jpg

I brought some SR560s in to set up the control loop, but it was difficult to bias the PZTs enough (so that the polarity never reversed) and still have enough range on the SR560 output; we need a voltage amp to really get going with these guys. In the meantime, I thought it would be somewhat useful to characterize the relative strengths of the PZTs by driving them both and maximizing the CMRR. I drove them at 2 Hz with the Tektronix FG, using an offset of +5Vand I determined that the best amplitude ratio was about 3:5. Below is the voltage spectrum of the PD output while driving one and both mirrors, respectively, showing a CMRR of about 36. I am certain that we can do better, but it is difficult to tweak it in view of the excess noise at the moment with the loop open.




  168   Fri Jan 7 20:14:39 2011 ZachDailyProgressCreakREFL installed

This morning I installed the polarizing optics for the REFL isolation. I thought I would need another QWP to linearize the output beam of the HeNe, but the JDSU supposedly has a 500:1 linear polarization ratio out of the box, so all I had to do was turn the head to the right orientation. Below is a raytrace of the setup. 


I hooked up the PDs to the scope to see if things were working correctly, and though the DC levels are off (i.e. the contrast is not great due to the rather hodgepodge setup), the AC response looks correct. Here is a screenshot. Here, both of the mirrors were being driven common-mode at 2-Hz with the 3:5 ratio I figured out yesterday. You can still see some 2-Hz harmonics here (particularly ~8 Hz), but the majority of the signal is just the ambient noise.


EDIT: I just realized that, interestingly enough, the dominant low-frequency signal here is probably not exactly 8 Hz, but slightly above; if you look at the previous entry, when both mirrors are driven at 2 Hz, the strongest peak is at a bit above 8 Hz, where there is no peak in the single-mirror case (though there is one at 8 Hz existing as a 2-Hz overtone there). I am not sure what this is from.


  186   Thu Apr 14 15:07:39 2011 Ming Yuan, taraLab InfrastructureCreakRack from Drever lab

Today we brought a rack from Drever lab to 050 W Bridge. This rack will be used for crackle experiment.


   We start setting up the experiment, and we need a rack for electronics equipment, so with Steve's help we got one from Drever lab. We cleaned the rack before brought it in the lab, so there should be no dust.


Next, we will find a lock-in amplifer, maybe a function generator to drive the system.



We plan to work on the experiment on

Tuesdays  afternoon

Thursdays afternoon

Fridays afternoon.



  187   Fri Apr 15 18:42:40 2011 tara, MingyuanDailyProgressCreakStart crackling (again)

Ming Yuan, tara

We setup the basic Michelson interferometer with one arm which can driven by a PZT and another one whose position is adjustable. 

The laser we got didn't work at the beginning. We found that the power supplier was not functional. Tara borrowed another power supplier for the laser.

The basic Michelson interferometer was setup. One of the mirror attached on copper plate was replaced by a regular mirror with position adjustable. One of the PZT is needed to be fixed.

We observed Dark Fringe by adjusting position of the regular mirror.

We got the signal from a basic Michelson setup with one of the arm being driven by a PZT.

 This is the signal from the oscilloscope.

First, we check the signal when there is no voltage applied to the PZT, the signal is plotted in green.

Then, we drove only one of the mirror by PZT. The voltage is 6Vpkpk, with 7V offset. 

 The signal is plotted in blue when the mirror was driven. We can see strong signal on the scope.




  188   Tue Apr 19 19:41:51 2011 taraDailyProgressCreakStart crackling (again)

 mingyuan, tara

            We setup the Michelson interferometer with two identical x and y arms. We drove both mirrors at 2 Hz and observed signal at 10 Hz using a lockin amplifier. We saw no significant difference whether the mirror were dirven or not.

           (The pzt for the second mirror is fixed. The wire is soldered back to its electrode.)

             We setup the Michelson interferometer, now with similar setups on two arms. The end mirrors on both arms are attached on metal shims. The shims touch the PZTs which are driven by 2Hz, 6Vpkpk sinusoidal signal with 7 V offset.

             We use a voltage divider(we planned to make one, but we found a nice one in EE lab lying on the floor, so we borrowed it) to adjust the voltage on one of the PZTs to make sure that both mirrors are driven by the same distance. We adjusted the divider to minimize the signal at 2Hz.


              fig 1: With a voltage divider, we can adjust the voltage on the PZT so that both mirrors are pushed by the same distance and the 2Hz common mode is minimized. On the plot, Y axis shows the signal output from the lock in amplifier at 2Hz. The higher value means the stronger signal at 2Hz. X axis is time scale. The setup was 5mV sensitivity range, filter in 300 ms, phase -152.3 degree.

 The signal output from the lock in amp has not been calibrated to length yet. We just want to see the qualitative result.


                 Once we made sure that we minimized the common mode, we tried to measure the possible up converted noise at 10Hz. (We used the internal oscillator in the lockin amplifier for reference signal at 10 Hz.)

               First, we did not drive the mirror, so that we could see the signal at 10 Hz due to background. Then, we drove the mirror at 2 Hz, and observed any possible up-converted noise at 10Hz

              There is nothing conclusive yet. The 2Hz signal that drives the PZTs are plotted here for comparison. From a quick glance, there is no obvious correlation between the noise and the driving signal.


fig2:  Signal from the lock in amp at 10Hz. Setup: sensitivity at 500 uV, in filter 300 ms.


Why are we doing this:

We want to measure any possible up-converted noise when the material under stress is driven at low frequency. For example, the system is driven at 2Hz, there might be broadband noise occurs due to the motion. If there is, we can try driving the system with different amplitude to see if the noise changes or not.

  189   Tue Apr 26 17:06:37 2011 Mingyuan, TaraDailyProgressCreakstart crackling



We are trying to chopping the signal today.

   The low noise amplifier can be used as bandpass filters for 10-100 HZ.

   We are trying to figure out the signal squaring. The mixers in the lab only work for high frequency (> 500 KHZ).

   Frank recommends us to use AD734 4-Quadrant multiplier. 

   We checked the electronics lab in Downs and 40 m and couldn't find it. We plan to order some AD734.


  190   Thu Apr 28 21:55:25 2011 taraDailyProgressCreakstart crackling


 I ordered 5 of AD734 and thinking about how to make a circuit for squaring the signal.


    The "chopping" signal readout technique requires that we square the signals.  Basically we need to (as rana suggested):

(1) square the signal from PD, (after 10-100Hz bandpass) to convert it to power, and band pass it again.

(2) square the driving signal (might be varied from 0.1- 1Hz.) This is illustrated in the diagram as doubling the frequency ("2 x freq" box.)  The driving signal for PZT is offset. So the signal is  V drive = A + B xsin (2pi fdrive t) with A > B. This ensures that the voltage on one end of the PZT is always higher than another end. We might need to high pass this signal first, to get a signal with only 2 fdrive frequency after we square it.      

(3) multiply signal from (1) and (2) to demodulate the signal.


Basically, 3 multipliers are needed.

The first one is for (1), so the input frequency is ~ 10 -100Hz, and the output is 20-200 Hz.

The second multiplier is for (2), the signal is ~ 0.1 - 1 Hz, but this one might have large DC term after we square it.

The third one is for (3), this one has to multiply 2 low f signals together which is quite similar to (2), so the design can be the same.


I'll consult Frank and/or Koji again before finalize the multiplier circuit.



  191   Fri Apr 29 18:39:37 2011 taraDailyProgressCreakstart crackling

In the mean time, we might try this mixer to multiply the signal. I'll order one.

  192   Fri Apr 29 21:23:15 2011 taraDailyProgressCreakstart crackling

koji, mingyuan, tara: We designed the circuit for multiplying/ squaring signals with AD734. 

    The details for each signal are discussed here. 

    The "general multiplying circuit" box in the diagram shows how each AD734 will be powered/ fed input signal.

     For the signal from the PD, we need to bandpass(10-100Hz) it first. We plan to use a SR560. To split the signal to x and y input, we will use a T connector. Then square the signal and band pass it again at 0.1 - 100Hz bandwidth.

     For the signal from the function generator which drives the PZT. We will high pass it, by either SR560 or a high pass circuit. We might need a buffer here if the output impedance of the function generator is not high. Split the signal with a T again, and square it.

    After both signals are squared, we multiply them together. Send one to X1 input, another signal goes to Y1 input. Then we FFT the output signal from W.


Attachment 1: ad734_crackle.pdf
ad734_crackle.pdf ad734_crackle.pdf
  194   Mon May 9 11:25:05 2011 Mingyuan, taraDailyProgressCreakShim/mirrors replaced

  We switched the current metal shim with the thicker Aluminium shim. Now both mirrors are also the same. We tested and showed that the shim is not too hard to be pushed by pzt.

First, the thicker Al shims have bigger bending stiffness and more difficult to bend under the surrounding perturbation. Therefore, the signal we got has less noise from the surrounding perturbation.

By using the PZT we have, we can still drive the shim well. With the driving, we observed intensity oscillates from ~50 mV to ~200 mV. 

We also observed a low frequency (~80 mHz) oscillation of the signal. I didn't find the source of this oscillation. The sensitivity of response to driving is lower while the intensity is near the minimum and Maximum and higher while intensity is at the middle.



  195   Mon May 9 12:06:10 2011 tara, mingyuanDailyProgressCreakQ measurement for test blades

We measured the weight needed for pulling the blades down, and measured Q, f0 of the blades. For Rom blade, the weight is 1.279 kg, f0 = 2.27 Hz, Q = 300. For Rem blade, the weight is 2.005kg, f0 = 2.35Hz, Q = 475.  The test blades are named Romulus(Rom) and Remus(Rem).

     Why do we do this:

    The maraging blades are designed to be flat when they are in used, so we need to know how much weight do we need to pull them down to their operating level. The weight will determine the size of the load mass we want in the drawing as well. We plan to mount mirror mount on the load mass, so we can align the mirror for the interferometer's end mirror.  Plus, resonance frequencies and Qs of the blades and seismic noise will be used to estimated the noise budget of the setup.

    The weight was applied to the blade until the blade horizontally leveled. Then the total weight was recorded.  After that, we used shadow sensing technique to determine their resonance frequencies and Q factors.

The results are summarized here:

Blade     load mass       f0               Q

Rom         1.279 kg       2.27 Hz     300

Rem         2.005           2.35 Hz      475


fig1: determining the weight. The blade mounted on the table appears flat with the right weight.



fig2: Q measurement from Rom


fig3: Q measurement from Rem

  198   Tue May 10 18:29:44 2011 Mingyuan, TaraDailyProgressCreakSolid work drawing

We measured the tip tilt angle of the blade while the main part of blades was bent flat.  REM: ~9 degree; ROM: ~ 7 degree. This angle should be able to cancel by mirror holder.

One block of Al was designed to mount mirror holder with the blades. The SolidWork drawing is attached below.

Two screws (2-56, A2, 3/16) will be used to mount the block onto blades through the two holes in the head of blades.

One screw (8-32) will be used to mount the mirror holder onto the block. The mirror hold is light, the block should be able to hold it firmly.

The other drawings will be uploaded by Tara

Attachment 1: Mirrormount.PDF
Attachment 2: clamp_of_the_blade.pdf
  199   Wed May 11 22:17:35 2011 taraDailyProgressCreakstart crackling

 I tested the mixer, the demodulated signal from input at 10 - 100 Hz might be too small and too distorted to get reliable data.


  As we want to square/demodulate  signal in 10 - 100 Hz BW. a low frequency mixer might be a good tool. I asked Alastair to buy this mixer for me, and it arrived today.

  The lowest acceptable frequency in the design is 500 Hz, but I don't know how well it works at 10 - 100 Hz so I tested it.


   ==Setup and result==

   I used  SR785 to generate sine wave, then split it with a T and connected the output to LO and RF of the mixer. 

   I tested that the mixer works fine at the designed frequency.  The plot below shows the result from  1kHz signal input.


Next, I changed the frequency to 10 Hz, 50Hz, and 100Hz.

  The demodulated signal is then observed in frequency domain (left column of the plot) and in time domain ( right column of the plot)

I think the peaks at driving frequencies (10Hz, 50Hz, 100Hz and their harmonics) appear because of the offset of the sine input signal.



The results for low frequency  seem to be too distorted. We will test the AD734 chips tomorrow. I got the package this afternoon.

  201   Thu May 12 23:18:27 2011 ryan, taraDailyProgressCreakstart crackling

 We tested AD734 on the diagnostic bread board, the result is good.

     We want to square/multiply signals between 10 to 100 Hz, so we use AD734 chip to do the work. The circuit is connected as described here

We try to square the signal. the test signals are sine waves at 10 Hz, 50Hz. The output are nice sine waves, but the gain is high (72dB). The chip rails as the input exceeds 0.5 Vpkpk. We will have to check the signal from the PD in the setup to see if it is higher than 0.5 Vpkpk or not. If so we can change the gain of the chip. Otherwise we can go ahead and use it.


The spectrum of the output, for 10Hz input, there's a peak at 20Hz output. For 50Hz input, there's a peak at 100Hz. The response is flat between this bandwidth.


  202   Fri May 13 00:06:32 2011 MingyuanDailyProgressCreak 


The low frequency oscillation we mentioned in the previous Log could originate from the creep of the rubber between PZT and the Shim. Because the initial stress caused the creep of the rubber, the Shim relaxed slowly and changed the optical path and caused the low frequency oscillation. This mechanism can explain the phase change between the driving and the signal. Rana recommended to use a spring to replace the rubber. To calculate the spring constant of the spring: Spring constant of the Shim, ks = 3EI/L^3; Amplitude of displacement of PZT ~ A; Amplitude of displacement of the Shim ~ B; the spring constant of the spring ~ k;

k = ks*B/(A-B)

From current dimension, ks ~ 10000 N/m. If we don't want to drive PZT too hard, assume A = 2B; k = ks = 10000 N/m.

  204   Fri May 13 12:24:47 2011 tara, ryanDailyProgressCreakAD734 multiplier info

Some useful things to remember for the AD734:

The transfer function when wired as a multiplying circuit is: W = ((X1-X2)*(Y1-Y2) / 10V) + Z2
For this to be true the Z1 pin should be wired to the output W, to provide feedback, which isn't shown explicitly on Tara's general multiplying circuit diagram. Also for testing the chip inputs were wired as differential, not with one leg grounded as shown on the GMC diagram.

The 10 V comes from the default division voltage when the denominator control inputs (U0, U1, U2) are grounded. If you want some added offset to the output you can send it to the Z2 pin.

The input impedance is listed as 50k for all X, Y, and Z pins.

We measured the noise with 0V X/Y inputs, it was around 1 mV/rtHz at 10 Hz, as you can see in Tara's earlier post, slightly improving at higher frequency.
The input noise is listed as 1 uV/rtHz from 100 Hz to 1 MHz. The amplifier gain is listed as 72 dB which is ~ 4000x, and we were at the default denominator of 10V so this corresponds to a noise of 1e-3 * 10 / 4000 = 2.5 uV/rtHz at the input, seems reasonable compared to spec sheet. The signal to be squared in the creak setup (the output of the Michelson) will have to be bandpassed first, probably by an SR560, so gain can be applied there to get in over the multiplier noise floor.

As Tara noted the output does rail for signal amplitudes well below the listed maximum input, so we need a better understanding of how to control the gain.

  206   Thu May 19 21:31:28 2011 Mingyuan, TaraDailyProgressCreakstart crackling


We used a big box to cover the optical loop. The interferometer is more stable now.

We build other two AD734 chip circuits for signal square and multiplier.

We already tested that we could square the driving signal and PD signal.

The square of the PD signal has a big offset from the AD 734 circuit. We need figure out how to take the offset out.

  210   Thu May 26 18:58:56 2011 Mingyuan, TaraDailyProgressCreakNoise from AD734






We figure out the offset issue of the chip AD 734. We measured the noise of chip AD 734 with 50 ohm input terminated.

The noise is shown below for two chips we are using and noise from spectrum analyzer is attached for reference.

The noise of AD 734 is about 1 uV/root(Hz) at around 50 Hz. The sensitivity of of the chip should be:

dV*dV/10 = 1 uV/root(Hz)  =>  dV ~ 3 mV/root(Hz)

We are not sure about that we understand the noise propagation through the chip correctly.  

Attachment 1: Noise_of_AD734_100_HZ.jpg
Attachment 2: Noise_of_AD734_800_HZ.jpg
  215   Tue May 31 17:49:47 2011 Mingyuan, TaraDailyProgressCreakdata readout



To have the ability of controlling the phase, we need adjust DC voltage of one of the PZTs independently.
We use the function generator to generate AC driving with a DC offset for one of the PZTs and use a OP270
chip to add the driving signal with another DC voltage for another PZT. By changing this DC voltage, we can
control the phase of interference signal. We adjust the voltage to put the PD intensity in the middle to have
the best sensitivity.
We did the same measurement as last time to check the peaks we observed. By use the same condition, we do see
a few extra peaks while the plates are being drovn at 2 Hz. We also changed the driving frequency to 0.7 Hz and
did the same measurement. The results looks different.
  Tara will upload the data later.

  571   Wed Sep 12 17:15:21 2012 RanaDailyProgressCryo SUSSilicon Suspension talk from Alan Cumming


Useful data on Silicon strength tests...

  765   Tue Dec 10 17:58:38 2013 nicolasMiscCryo SUSSilicon Fiber cavity sensitivity to misalignments

If we build silicon fiber cavities without alignment control, how well do we need to have the two fibers aligned in order to have the cavity mode remain on the fibers?

I've made a short script that goes through the numbers, here is an example output:

>> beamshift
L = 10cm, R1 = 35cm, R2 = 35cm.
g1g2 = 0.5102
Beam size w1 = 223.0642 microns, w2 = 223.0642 microns.
For 10mrad misalignment, the beam shift is: 
0.14583cm or 6.5377 beam widths

So if our mirror pad is ~0.5cm radius, a shift of 0.15cm still keeps the beam spot many spot sizes from the edge.

This is just a first guess. We now need to come up with reasonable limits on the mirror radius and what our expected dead reckoned misalignment will be.

Code is in 40mSVN/SiCryoSus/Calculations/pointingSensitivity/

  865   Tue Dec 2 15:15:56 2014 ZachDailyProgressCryo SUSThings we talked about on the phone 11/21/14

Here is a recap of a phone conversation between Rana, Nic and me, which I am remembering from my mindbrain:

  • I described the stalemate at which we had arrived:
    • We have used COMSOL to estimate ideal clamping losses assuming perfect contacts. Using these models, we have found ways to make the ideal clamping loss for a simple structure---steel clamping to a thick (~500 um) piece of Si, while a thinner portion (~50-100 um) of the Si juts out to become the resonator---nearly as low as the intrinsic loss of bulk Si. Clearly, this would be good enough to investigate any surface effects, but the clamp interface will never truly be ideal.
    • We began thinking about ways to further reduce the clamping loss by adding isolation/cancellation schemes. For example, we studied the butterfly resonators that have been able to achieve very low loss for particularly well isolated modes.
    • We then considered how we might construct something like this while also building a twin cavity setup. Initially, we thought of using a single Si wafer with two resonators, each of which would be situated as an end mirror in its own cavity. This concept emerged in two differing contexts: 1) Compactness and clamping desing (i.e., it seemed convenient to clamp a single wafer by the middle on each end of the cavities, and have each wafer serve both cavities) and 2) isolation/cancellation schemes, mostly since there is some superficial similarity between the butterfly-type resonator and a wafer with more than one cantilever on it.
    • We then wasted away trying to think of how we could model such a system while taking into account all the relevant figures of merit (clamping loss, resonator-to-resonator coupling, etc.)
  • Rana then elucidated his theory that there are three things we have to consider here. From simplest to most complex:
    1. With a simple cantilever geometry, how do we design a clamp that least disturbs the measurement of thermal noise in the resonator? We think we have this one solved, using the varying thickness approach, but it relies on a good idea of the imperfections in the surface contacts. Likely, we will want an added layer of isolation/cancellation in addition to a good clamp, due to these imperfections.
    2. How can we isolate the resonator from the clamp so that extra clamp noise from non-idealities is suppressed? If we only care about a particular mode or set of modes, we can do something akin to the butterfly resonators, as these isolate particular modes very well from the motion of the clamp. However, we are also interested in broad off-resonance behavior. I believe this rules out something as simple as the balanced-oscillator approach of the butterfly resonators, and instead requires something closer to the cascaded passive isolation stages of our suspension systems.
    3. How do we integrate all this into two parallel cavities to make our beat-based measurement? If we work through (1) and (2) to make something that is good enough to allow us to measure surface effects with high accuracy, we may find that we have something that's not particularly suitable for integrating into a twin cavity setup. That said, we already have our cryostat, so we have to figure out how to put something useful into that space.
  • With all that in mind, our plan was to do the following:
    • Immediately, we should buy some wafers that have the desired thickness ratios cut into them. It is important that the resonator sections are thinned symmetrically from both faces of the wafer (i.e., not etched down from one side so that one cantilever face is coplanar with one original wafer face). We can have these be several cantilevers distributed around one circular waver, or perhaps better is having a wafer cut to make several standalone cantilevers with a thick clamping section at one end. Ideally, several of these would be punched out of the original wafer structure as in the original ideal.
    • The above resonators will be tested with ringdowns in the smaller cryostat. Using different clamp ideas, we will see how close we get to the ideal clamp loss given by COMSOL. This will give us some idea of how much extra cleverness we will need to put in the real versions.
    • At the same time, we will begin building the optical setup with macroscopic mirrors.
    • The goal is that both the resonator prototyping and the optical setup are completed in parallel, and then the final clamp/resonator is installed in the main cryostat for immediate science.

Here is a screenshot of the axisymmetric COMSOL model used to get the ideal clamping losses from a thick/thin structure. Clearly, the strain energy in the ideal case is localized at the center, far from the steel/Si interface. This has been confirmed with a full 3D model of a more traditional cantilever.


  868   Wed Dec 3 20:45:50 2014 ZachDailyProgressCryo SUSCryostat unpacked

[Nic, Zach]

Today, we unpacked the IR Labs cryostat that will be the centerpiece of the Cryo SUS experiment. 

Everything was more or less in order, except that the baseplate does not have any outward extensions with which to mount the cryostat to the table. Also, the holes for the screws holding the baseplate to the barrel are not countersunk. So, as of right now, the entire cryostat sits on these screws' caps, which is not ideal. We need to either a.) get a new baseplate made up with some wings on it and countersinking for the screws, or b.) work out another way to hold and mount the cryostat (for example, we might want some soft isolating material there anyway, though it will come at the expense of alignment drift).

I followed the instructions and removed the strange anodized heat shield bottom plate that comes with it during shipping, replacing it with the usual one and then resealing the chamber. As directed, I also pumped out the air again---the charcoal getter is not supposed to be exposed to atmosphere for long periods of time.

  728   Tue Sep 10 11:15:31 2013 nicolasComputingDAQX1KRK model restarted

I restarted the DAQ and the KRK model today at about 11AM local time to increase the acquire rate of the accelerometer channels.

The autolocker script died when it couldn't access the epics channels, I restarted it.

  729   Thu Sep 12 00:29:23 2013 ranaComputingDAQX1KRK model restarted


I restarted the DAQ and the KRK model today at about 11AM local time to increase the acquire rate of the accelerometer channels.

The autolocker script died when it couldn't access the epics channels, I restarted it.


  1820   Fri Aug 30 14:45:42 2019 ranaComputingDAQDownload data with pyNDS

I'm attaching a script to download data from the LIGO sites with python.

I recommend using it in your anaconda3 ENV:

conda install -c conda-forge nds2-client python-nds2-client

and then before running the script you have to initialize your Kerberos token:

kinit miley.cyrus@LIGO.ORG

then you run the script:

python getData.py --ifo=L1 --fs=1024

as usual, run with the -O or -OO flags to silence the debug messages.

Attachment 1: ChanList_darm.txt
Attachment 2: getData.py
#!/usr/bin/env python
# this function gets some data (from the 40m) and saves it as
# a .mat file for the matlabs
# Ex. python -O getData.py

import scipy.io as sio
import scipy.signal as sig
from astropy.time import Time
import nds2
... 101 more lines ...
  1910   Wed May 19 09:25:34 2021 PacoNoise HuntingDOPO316 Hz noise


- Have been investigating 316 Hz noise in the control signal for the DOPO lock. Here is a list of some things that have been ruled out, mostly electrical:

  - EOM power supply --> noise still present in DOPO transmission
  - RFPD DC out --> no funky ground loops with scope (also looking at demod signal in different channel), noise still visible in transmission
  - RFPD power supply --> noise still visible in transmission...
  - Pump laser intensity (upstream pickoff) --> not a great test because pickoff optics are also on the optical table..
  - 2 x SR560s --> No effect after bypassing
  - Marconi --> same result as with anything in the loop after RFPD demod

- Things left to rule out:
  - Fume hood exhaust fan ** highly suspected, my phone's own cheap-o microphone power spectrum shows peaks at 316.5 Hz (!) when near the exhaust fan
  - NPRO temp controller fan --> phone audio spectrum shows line noise (60 Hz) mostly, and also 188 Hz... need to test further independently of the fume hood...

In ruling out the 6-axis translation mount on the DOPO cavity, I removed the PPKTP crystal + oven temporarily but still saw the noise. Since the resonator was no longer stable without the crystal, I needed to bring the mirrors closer and realign the output coupler from scratch. 

Restored DOPO cavity with crystal, alignment. MM efficiency ~ 35%... still optimizable.

  1913   Thu Jun 10 09:59:52 2021 PacoLab InfrastructureDOPODisassembly for new optical table

Today the DOPO v0 got disassembled to make way for the optical table swap. Most components have been stored in the white cabinet's bottom panel.

Attachment 1: IMG_20210610_092713.jpg
  1919   Tue Aug 10 11:00:43 2021 PacoDailyProgressDOPODOPO v2

[paco, nina]

We started rebuilding the DOPO in the lab even though the new optical table hasn't arrived. For this reason, we are using a 1 ft x 3 ft x 0.5 in anodized aluminum breadboard which we can then attach handles to move the setup. This also makes the prototype's footprint smaller. The first thing we did as usual was settle on a beam height. The beam height used before was ~ 3in (~ 75mm), and since the EOM, Faraday Isolator, and RFPD are nominally at that height from the breadboard, the only thing we had to fix was the pump laser head. The bare height is 55 mm, so we stacked two 9 mm thorlabs bases together, bolted them down to the breadboard and then mounted the NPRO laser head on the top. Finally, using a level we secured it to the breadboard using the three points and long 1/4-20 screws while being careful as we didn't want to flex the head too much.

Next up is aligning the laser to the EOM and Faraday Isolator. For this, we will use the beam profiles measured late last year. Another task ahead is to implement the new mount for the cavity.

  1929   Thu Jun 23 16:34:46 2022 PacoLab InfrastructureDOPORelocated DOPO setup

Following Koji's request, I took some time to clear the area surrounding the crackle chamber so it can be migrated to the former TCS lab.

I moved the DOPO setup which was sitting on a breadboard for easy transportation (Attachment #1) and placed into the other table in the lab. Attachments #2-3 shows the cleared area. Several instruments from the DOPO experiment still remain around the other side of the crackle chamber, if they need to be relocated I can move them as well.

Attachment 1: PXL_20220623_222426584.jpg
Attachment 2: PXL_20220623_223623414.jpg
Attachment 3: PXL_20220623_224259785.jpg
  1773   Sun Nov 25 19:25:37 2018 ranaHowToElectronicsNoise monitor PCB assembly completed

you can just use some BNC clip doodles (mini grabbers, etc). Go directly from the test equip (scopes, analyzers) to the pins on the board. Or if you are able to mount the D-sub connectors, you can use a breakout board. Can borrow from the 40m if you don't have them in WB.

  1777   Mon Dec 17 11:20:32 2018 ranaDailyProgressElectronicsSR785 netgpibdata
  1. add photo of stuffed board
  2. add time series of output with input terminated
  3. check for internal saturations
  4. use the software from Craig to download and plot the SR785 data
  1780   Fri Jan 4 22:18:53 2019 DuoDailyProgressElectronicsUpdates

Photo attached in attachment 1.

The times series output is shown in attachment 2 (Attached picture since I cannot get data from the oscilliscope, which requires floppy disk data transfer). There is an 87mV/rtHz oscillation at about 1.4MHz (op amp oscillation?).

I tested the noise with SR785, both time and frequency domains, in attachment 4 and 5. In time domain, I only see the 60Hz noise, not the 1.4MHz one (maybe because SR785 does not reach that high frequency). In frequency domain, noise in the passband is generally less than 10uVrms/rtHz. With a gain of 125, 10uV/rtHz corresponds to roughly 100nV/rtHz.

Attachment 3 is the transfer function, which is as we wanted, with a gain 2.5 less since this version does not have the last stage.

Internal saturation: what input do we use to test it?

Note: the noise FFT measurement has a lot of time dependence. It fluctuates a lot. Also sometimes (just a few hours before this measurement), I cannot reproduce the noise measurement mysteriously - it gives me much higher noise.

  1. add photo of stuffed board
  2. add time series of output with input terminated
  3. check for internal saturations
  4. use the software from Craig to download and plot the SR785 data
Attachment 1: time_series.jpg
Attachment 2: board.jpg
Attachment 3: TransferFunction.zip
Attachment 4: NoiseFrequency.zip
Attachment 5: NoiseTimeSeries.zip
Attachment 6: TransferFunction.pdf
Attachment 7: NoiseTimeSeries.pdf
Attachment 8: NoiseFrequency.pdf
  1786   Fri Feb 15 18:38:00 2019 ranaNoise HuntingElectronicsNoiseMon nonlinearity?

Before making a wide deployment, we should also test the latest noisemon circuit for downconversion.

  1. Measure the noise output with no DAC signal
  2. Measure the noise output with 0.1x the reference DAC signal (low noise ETM drive)
  3. Drive a line at high frequency in addition to the reference signal
  4. adjust the ampltiudes of the high frequency drive and the reference signal independently and look at how the 20-100 Hz noise changes.
  1791   Fri Jul 12 13:45:39 2019 DuoNoise HuntingElectronicsNoisemon board test plan

1. Transfer functions of 1-4 channels, compare with simulations.

2. Noise of 1-4 channels, compare with simulations.

3. If feasible, nonlinearity.

4. Functionality of fast current, slow current and  voltage monitor channels.

All test results will reply to this post.

  1796   Thu Jul 18 11:50:43 2019 DuoNoise HuntingElectronicsNoisemon board test plan

Noisemon + Coil driver TF and noise data. This is raw data measured from the lab. TF data is in counts dB. It needs to be converted to volts dB (+6.02dB). The noise is in ADC counts: 2^16 counts is 40V.


1. Transfer functions of 1-4 channels, compare with simulations.

2. Noise of 1-4 channels, compare with simulations.

3. If feasible, nonlinearity.

4. Functionality of fast current, slow current and  voltage monitor channels.

All test results will reply to this post.


Attachment 1: noise
           0 0.0060799727 0.0036104703 0.0035354728 0.0043438259
           1  0.011494039 0.0093825972 0.0096197175  0.012887708
           2  0.011482876 0.0092526972  0.007686412  0.010214086
           3  0.007793535  0.010190732 0.0093236016 0.0063966918
           4  0.008946578  0.010989403  0.010403648 0.0065775975
           5 0.0091153961 0.0096783806 0.0093079647 0.0084264427
           6 0.0066599683 0.0073985206 0.0084112696 0.0085661933
           7 0.0089498917 0.0082680834 0.0077745947  0.009830121
           8  0.010017198 0.0076360367  0.008065613  0.010290137
           9 0.0086757941 0.0073405644 0.0076935664 0.0088897012
... 991 more lines ...
Attachment 2: tf
           0    17.698841    18.056847    18.090052    17.871181
           1 -0.0032254728   0.89752418    0.1702327  -0.15558846
           2   -23.998034   -20.766872   -26.681761   -29.600937
           3    -18.63299   -15.572646   -21.355885   -24.697672
           4   -27.239981   -20.098402   -30.695086   -28.402729
           5   -17.836342   -22.218195   -15.790459   -14.902033
           6   -6.2559071   -7.0367184   -5.5133157   -5.1673536
           7    2.6998141    2.9237394    2.8741286    2.8509607
           8    6.9691806    6.9828043    7.2662587    7.3255196
           9    12.865563    12.936651    13.216954    13.254182
... 9991 more lines ...
  1797   Thu Jul 18 16:44:30 2019 DuoNoise HuntingElectronicsNoisemon board test plan

Analyzed Noisemon + Coil driver TF. The coil driver is in LP_OFF and ACQ_OFF status. The TFMeasured.txt file in the zip is in counts (ADC over DAC) so we need to add 20log10(2) to convert it to volts.


Noisemon + Coil driver TF and noise data. This is raw data measured from the lab. TF data is in counts dB. It needs to be converted to volts dB (+6.02dB). The noise is in ADC counts: 2^16 counts is 40V.


1. Transfer functions of 1-4 channels, compare with simulations.

2. Noise of 1-4 channels, compare with simulations.

3. If feasible, nonlinearity.

4. Functionality of fast current, slow current and  voltage monitor channels.

All test results will reply to this post.



Attachment 1: tf.pdf
Attachment 2: tf.zip
  1798   Fri Jul 19 23:55:19 2019 DuoNoise HuntingElectronicsNoisemon board test plan

Noise compared with LISO.

In the region we care about noise (20 - 100 Hz), we can see it matches well with LISO calculations.

But why not at all frequencies ??

Attachment 1: noise.pdf
Attachment 2: noise.zip
  1799   Tue Jul 23 16:31:19 2019 DuoNoise HuntingElectronicsNoisemon board test plan

I forgot to add the ADC noise. Now that I put the ADC noise there, the noise matches beautifully.


Noise compared with LISO.

In the region we care about noise (20 - 100 Hz), we can see it matches well with LISO calculations.

But why not at all frequencies ??


Attachment 1: noise.zip
Attachment 2: noise.pdf
  1800   Tue Jul 23 18:44:34 2019 DuoNoise HuntingElectronicsNoisemon board test plan

Noisemon transfer function with phase, in dB counts.


1. Transfer functions of 1-4 channels, compare with simulations.

2. Noise of 1-4 channels, compare with simulations.

3. If feasible, nonlinearity.

4. Functionality of fast current, slow current and  voltage monitor channels.

All test results will reply to this post.


Attachment 1: tf
           1    9.7050228     123.2298    10.239232    123.21356   -10.019529   -118.16026   -10.616507   -118.89268
           2   -34.514286     31.98028    -24.85087    15.130191   -47.043491    52.538929   -48.512966    55.107563
           3   -36.056171   -4.5462341   -36.446568   -56.627953   -31.206287    61.423027   -32.429966    45.018265
           4   -21.379314    33.787785   -19.129549    22.378428   -25.811764    58.529861   -23.563175     49.62664
           5     -11.7675    27.131598   -10.383668    28.965872   -11.698998    37.911072   -11.602596     37.31863
           6   -2.9505889    27.217129   -2.9378238    27.117661   -5.3381448    27.359547   -5.3463163    25.167641
           7    1.4774156    15.846872    1.6330251    17.754173  -0.70415765    18.485508  -0.56274724    16.864006
           8    6.3308201    11.971453    6.3700743    13.936064    8.5621395    16.351494    8.6424751    15.114208
           9    12.133464   -6.1598492    12.190346   -4.7948561    13.710788   -6.6996503    13.754128   -7.9086943
          10    17.565397   -19.773212    17.708769   -17.956547    17.125546   -19.085073     17.13752   -20.339249
... 990 more lines ...
  1801   Wed Jul 24 00:12:18 2019 DuoNoise HuntingElectronicsNoisemon board test plan

Transfer function. The simulation and the test results differs by a phase of 180 degree (attachment 3). I added 180 degree got attachment 1.


Noisemon transfer function with phase, in dB counts.


1. Transfer functions of 1-4 channels, compare with simulations.

2. Noise of 1-4 channels, compare with simulations.

3. If feasible, nonlinearity.

4. Functionality of fast current, slow current and  voltage monitor channels.

All test results will reply to this post.



Attachment 1: TransferFunction.pdf
Attachment 2: tf.zip
Attachment 3: TransferFunction1.pdf
  1802   Mon Jul 29 13:59:02 2019 DuoNoise HuntingElectronicsNoisemon board test plan

Voltage monitor test data. Theory: 20 * log(1/2 * 1/3) = -15.6dB. ~1dB less attenuation from calculation.


Transfer function. The simulation and the test results differs by a phase of 180 degree (attachment 3). I added 180 degree got attachment 1.


Noisemon transfer function with phase, in dB counts.


1. Transfer functions of 1-4 channels, compare with simulations.

2. Noise of 1-4 channels, compare with simulations.

3. If feasible, nonlinearity.

4. Functionality of fast current, slow current and  voltage monitor channels.

All test results will reply to this post.




Attachment 1: Desktop
           0   -14.423977          180
           1   -14.401674   -179.99416
           2   -14.393744    179.94778
           3   -14.352913    179.65042
           4   -14.313849    179.05284
           5   -14.353559    179.54588
           6   -14.366872    179.65906
           7   -14.366401    179.50722
           8   -14.384005    179.51443
           9   -14.367351    179.73422
... 9991 more lines ...
Attachment 2: Screenshot_from_2019-07-29_13-59-25.png
  1803   Sat Aug 3 23:19:55 2019 DuoSummaryElectronicsOp amp oscillation caused by capacitive loading and its fix

When we connect the voltage monitor channel of the noisemon board to a long cable (100ft), the op amp (LT1792) oscillates. Usually putting a 50 ohm resistor at the end will fix it. In this post, I studied how the oscillation happens and why putting a 50 ohm resistor will fix it.

We know 1) op amp has a dominant pole, giving a phase shift of 90 degrees 2) op amp oscillates when the loop gain is unity and the phase shift is 180 degrees. 3) Op amp has some non-zero output resistance.

Based on 3), we can see that when the output is capacitively loaded, there will be another pole in the transfer function due to the RC configuration. Since both R and C are small, it will be at high frequency (as op amp oscillations usually are). Thus, beyond the dominant pole, the phase will keep shifting to 180 degree based on 1). When this happens before the loop gain drops to unity, there will be oscillation based on 2).

Fix: insert a resistor at the output. This fixes the problem since it adds a zero with frequency a bit higher than the parasitic pole. This zero pulls the phase up so that when the loop gain reaches unity, the phase is around 90, at least far from 180, preventing oscillation from happening. The transfer function of this is simulated in LISO. From the plot, we can see the effect of the output resistance pulling the phase up to zero (90 in the case of an opamp because of the dominant pole).

Attachment 1: osci.fil
uinput vin 1
gnuterm pdf
r rout 50 vin vout
r rproc 50 vout rproc_1
c cload 1n rproc_1 GND
uoutput vout:db:deg
freq log 1 1G 1000 ### from data file
Attachment 2: osci.pdf
  1819   Fri Aug 30 13:15:07 2019 DuoSummaryElectronicsITMX DAC noise

The PUM noisemon board has been installed in Livingston ITMX test mass. After the installation, we fetched the coil driver drive signal, noisemon output signal and the coherence between them. 

This is how we calculate the DAC noise spectrum. The unit is V/rtHz.


The data fetching configurations are:

- Start time: 1250467218. Locked for more than 20hrs from there, if you check here: https://ldas-jobs.ligo-la.caltech.edu/~detchar/summary/day/20190822/

- Bin size: 0.1Hz

- Window: Hanning

- Average: 1000

Attachment 1 and 2: plot of the DAC noises in volts compared to the G1401399 model.

Attachment 3 and 4: plot of the DAC noises projected to the displacement of the test mass and incohrerently summed from all the four test masses.

All the data are attached as xml files. They are directly saved from DTT and can be opened in DTT.

To reproduce the plots, run the python code in the zip file. The code runs without any parameters. 

Attachment 1: plot.pdf
Attachment 2: Desktop.zip
Attachment 3: projected.pdf
Attachment 4: Archive.zip
  1821   Sat Aug 31 19:21:13 2019 ranaSummaryElectronicsITMX DAC noise

I don't agree about this. Doesn;t this ignore the noise of the noisemon circuit (analog readout noise + ADC noise) ? I think you must have a model for than noise in order to infer the DAC noise. Or maybe my pringle suggestion has better SNR?


This is how we calculate the DAC noise spectrum. The unit is V/rtHz.




  1822   Wed Sep 11 17:24:43 2019 DuoSummaryElectronicsITMX DAC noise

I did a quick estimation of the subtraction result. I subtracted the ADC noise and the noisemon noise. 

NoSubtraction=\sqrt{1-coherence}\times drive

Now I subtract it:


The ADC noise and Noisemon noise are converted to DAC volts (divided by the transfer function of the noisemon and coil driver).

Form the results from 10-200Hz, it seems that the calculated noise is DAC noise.

Attachment 2 is the result: subtracted noises vs. model compared to aLIGO noise.

Attachment 1 shows how the subtraction is done: we subtract noisemon noise from the total noise. (Noisemon noise contains ADC noise) Noisemon noise and ADC noise is neglegible at that frequency.

It seems at low frequency what we see there might still be DAC noise, if not other unknown sources.


I don't agree about this. Doesn;t this ignore the noise of the noisemon circuit (analog readout noise + ADC noise) ? I think you must have a model for than noise in order to infer the DAC noise. Or maybe my pringle suggestion has better SNR?


This is how we calculate the DAC noise spectrum. The unit is V/rtHz.





Attachment 1: plot.pdf
Attachment 2: beforeSub.pdf
  1837   Thu Dec 5 20:42:55 2019 DuoDailyProgressElectronicsNoisemon board modifications

Fully board successful with modification. The saturation issue has been fixed on all the four channels.

Attachment 1: NoDrive.pdf
Attachment 2: 10HzSine.pdf
Attachment 3: TF.pdf
ELOG V3.1.3-