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ID Date Authorup Type Category Subject
  679   Wed Jul 24 17:40:22 2013 ranaDailyProgressCrackleCompensating

You should add the flags in the model so that the error and control signals are written to the disk (as _DQ channels). Also make some filters so that the calbration of the signals can be loaded into them. In this way the data written to disk will be calibrated in some units (e.g. meters or Newtons).


Got 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.


  746   Tue Nov 5 21:37:11 2013 ranaComputingGeneralAndroid app for getting GPIB data?


  779   Tue Mar 4 19:43:25 2014 ranaDailyProgressCrackleNewport Suprema vs. Thorlabs Polaris



  803   Fri Jul 11 16:42:24 2014 ranaDailyProgressCrackleEBSD map for maraging steel blade sample


 Seems like a rather qualitative analysis. Is there any way you can make a 2D FFT of this so that we can see what the distribution of grain sizes are? What are typical sorts of grain size analysis people do in order to get quantitative comparisons?

  826   Mon Aug 11 15:55:46 2014 ranaThings to BuyCrackleFast PZT mirror for high BW locking

 In order to bypass the mechanical resonance problems that people have been having with the blades (i.e. they're not good for high BW locking), today we discussed using a stiff PZT mirror in one of the Michelson arms.

In principle, we would be concerned that we get crackle from this PZT element, but the LLO people have done some crackle measurements on the OMC PZTs so that we should have a good upper limit on that component and its good enough ??

Stiff, high BW, PZT actuated mirror mounts have been used for laser locking:

  1. http://holofringe.com/PiezoMirrors.html
  2. http://www.repairfaq.org/sam/lasersam.htm
  3. Nergis's thesis
  4. JILA idea

High Voltage Piezo drivers:

  1. http://www.falco-systems.com/products.html (~1500$)
  2. http://www.thorlabs.us/thorproduct.cfm?partnumber=MDT694B (~1000$)
  897   Fri Jan 23 13:06:33 2015 ranaNoise HuntingCrackleNew low noise PZT locking

When using such large resistors for the active filtering, its best to use a FET input opamp instead of the OP27. Otherwise it kind of spoils the stability of the reference. Zach has a comparison of noise for various FET input opamps for this purpose.

  1522   Mon May 2 15:26:41 2016 ranaSummaryCracklemeeting notes

* one leg got an air leak - ask Steve V to repair or send back to Newport for exchange

* Xiaoyue will check weights for new carbon steel blades

* may start new blade run in 10 days

* RSI paper to be resubmitted this week

  1678   Thu Mar 30 23:53:41 2017 ranaSummaryCrackleNew computation of crackling noise upper limits from the Crackle2 data

I think it would be useful to add this final step where you compute the aLIGO noise estimates, into the DCC document.

I also used to use 0.001 for the vertical to horizontal coupling, but recently someone was telling me that the factor is a bit larger; I think Brett or Dennis would know.

  1721   Tue May 16 17:25:17 2017 ranaNoise HuntingCrackleSome studies on actuation excess noise

If the resistors in the dewhitening filter and the coil driver are either wire-wound or (for SMD) metal film or thin film or MELF, its highly doubtful that you could see excess resistor noise.

IF, however, you used carbon or thick-film SMD resistors (Digi-key default), then it is likely wherever the current density is high.

  1746   Thu Aug 3 19:03:00 2017 ranaNoise HuntingCracklewhitening

Whitened specgram please to help see small differences. Also your noisy / quiet spectra look like they are contaminated at the low frequencies by the leakage from low frequencies due to the FFT window being too short. Perhaps retry with a 8 second FFT window to see if the effect is different.

  1763   Fri Oct 20 14:01:35 2017 ranaMiscGeneralSR560s removed

There were a couple of SR560 in the lab which I notice have been unplugged for months. Since this slowly degrades the batteries and causes us to spend money/time to replace them, I have moved these to the EE shop and put them on charge.

please plug these in whenever they are not in use

Attachment 1: 20171020_131805.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
  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.
  1818   Wed Aug 28 16:15:51 2019 ranaDailyProgress Changed bin size to 0.1Hz and got it

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

  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 ...
  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.




  1844   Tue Jan 28 08:46:13 2020 ranaDailyProgressElectronicsDistortion of noisemon

it might be the low input impedance of the board which the coil driver cannot drive..

I suggest you use probes to see where in the noisemon circuit the distortion is starting

  1848   Wed Mar 11 12:46:20 2020 ranaComputingNoise BudgetNoisemon at L1

you have to overlay the estimated displacemnt noise with the existing L1 noise bud or else we cant tell what the importance of the result is

  1850   Mon Apr 20 22:56:30 2020 ranaDailyProgressNoise BudgetNoisemon:DAC noise analysis from L1 and H1

for some reason the DAC noise estimate is too high, it can't really be so large compared to the real DARM curve (see the noise budget curves from LLO - there are other noise sources besides DAC noise)

some possibilities:

  1. maybe the DAC noise calibration into meters is wrong? I can't tell from the code where this came from. It would be good to put a comment in there.
  2. perhaps most of this noise is actually angular noise. The ASC control signals are adjusted by tuning the digital coefficients (before MASTER_OUT) so that the angle to length coupling is minimized. I think something like this has to be done to remove the angular noise from the DAC noise estimate.
  3. internal saturation of the DAC noise monitor?

I hve modified the code to plot nicer and also to remove some divide by zero problems. There is also still some warnings about other divide by zero - those should probably be fixed by examining how better to handle it when the coherence goes to zero.

Attachment 1: DACnoise-comparison.pdf
Attachment 2: dacNB.zip
  1895   Tue Jan 26 11:33:32 2021 ranaDailyProgressOpticsIncluded lens made by cavity input mirror and distrotion due to crystal


Error in previous calculations:

  • We did not take into account the effect of cavity input mirror on the coupled light. It would act as a thick concave lens for the coupled light into the cavity.
  • We did not take into account the divergence due to refraction at the crystal surface.

Goals and restrictions:

  • Use the fewest lenses as possible after having used a fixed lens at 67" point before the faraday isolator.
  • Choose a lens from a list of focal lengths available in west bridge labs.
  • Find the best overlap with the target beam of 18 um at the cavity waist with the most sensitivity with respect to lens positions.
  • The lens should not be closer than 1.5 inches from each other.
  • The beam widths should not exceed 4mm in diameter anywhere to ensure small areas of lenses are used.
  • Take into account the concave lens due to the input mirror.
  • Take into account the refraction due to crystal surface.

Analysis & Results

  • CavityLens.m is run to try all possible lens combinations for 1-lens or 2-lens solutions using ../20201222_BeamProfileNeatEOM/SeedBeam.mat as the seed beam.
  • The cavity input mirror is modeled as two refracting surfaces separated by 6.5mm. The first surface is flat while the second has ROC of -25 mm.
  • The crystal is modeled as two refracting flat surfaces separated by 20 mm.
  • The target beam waist is kept at the center of the crystal with 35.578 um diameter.
  • Then save all possible solutions with more than 90% overlap and where lenses are atleast 1.5" away from each other in AllPossibleSolutionsAbove90.mat using findPossibleSolutions.m.
  • findBestSolutions.m increases the overlap threshold to 0.995, allows maximum beam radius of 2mm anywhere and plots the best solutions in order of positional sensitivity of the lens. These are stored in BestSolutions.mat.

Analysis & Data


  1896   Tue Jan 26 11:34:51 2021 ranaDailyProgressOpticsIncluded lens made by cavity input mirror and distrotion due to crystal

would be good if you could find a solution that is not very sensitive to precise lens placement


  1901   Fri Feb 5 14:15:22 2021 ranaDailyProgressOpticsOPO cavity lock

For the splitting, I recommend not to use a splitter.

Instead, you can use a -10 or -20 dBm bi-directional coupler. You send the -10 dBm signal to the EOM amp, and you can fill up the needed power for the LO mixer. Also the "bi" nature of the coupler means that you can check for reflected power to diagnose if you are having impedance mis-match. Since you don't have an isolation amplifier in your setup, its important to make sure that reflections from one leg don't go back into the oscillator and disturb the other leg. Or maybe your oscillator box has an isolation amplifier between the oscillator and the splitter?

  1921   Tue Aug 17 11:09:29 2021 ranaDailyProgress1418 nm AUX ECDL1419 nm ECDL AOM diffraction at 95 MHz

Should measure the S-matrix using a bi-directional coupler.

  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.


  1862   Wed Nov 18 09:14:11 2020 shrutiMiscEquipmentLoanbeam profiler

I placed the two beam profilers with the two laptops and chargers right inside the Crackle lab, as requested by Paco.

  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.

  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
  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.

  209   Wed May 25 20:04:28 2011 taraThings to BuyCracklepurchases

I ordered opto mechanical mounts for turning the beam vertically. See the details in psl log.

I also orderedspring lock washers and wave washers. There will be used when we clamp the guillotine things for putting the load on the tip of the blade.

The pressure from the clamp should not exceed the yield strength of the maraging steel blade. So the spring lock washer should give us some limits of pressure on the blade. There is no specification about how much pressure it would be, so I ordered two kinds of washer for testing.

  211   Thu May 26 19:39:48 2011 taraDailyProgressCrackleAD734 squaring circuit

By mingyuan, tara

We figured out the offset problem in AD734 chips, the box for squaring and multiplying signals is finished.


          The problem from the previous circuit was that the ground from the signal was grounded with the load ground. This time the load ground is separated from the signal ground, Z2 is grounded to load groundThese corrections fix the offset problem and the maximum allowed input ( was 0.6 V.) Now the input can be up to 10V. The output, Z, is (X1-X2)x(Y1-Y2)/10 as described in the datasheet. Now the chip are connected as shown below.




          We are thinking about not using the default denominator (/10) for a multiplying chip (we certainly need it for squaring chips, otherwise the output will rail), because after the signals (from PD and driving voltage) are squared, their dc levels are ~3 V. When the two are multiplied together, the voltage output drops to 3x3/10 = 0.9 V. So if we can have denominator = 1, the signal will be larger. However, we have to understand how the noise in the chip works first. See Mingyuan's entry about input referred noise of the chip ,it is roughly 3 mV/rtHz. If the SNR remains constant regardless of the denominator, we might not need to worry about it.

Attachment 1: ad734_crackle.pdf
ad734_crackle.pdf ad734_crackle.pdf
  213   Fri May 27 20:32:18 2011 taraDailyProgressCrackleData readout

By Mingyuan Tara

We measured the FFT of the demodulated signal from chopping technique. We did not see much. The background noise is still too high.

      With everything ready, we used chopping technique to measure crackling noise. We measure the PSD from the demodulated signal between a) the mirrors being driven at 2Hz, and b) background noise, when the system was at rest, no driving force applied to the mirrors. We did this to check if we can see any signal due to crackling noise/ rubbing noise/ pzt noise or any noise originated from the driving mechanism or not. The result is not quite clear, we see a few peaks from the driven system around 40 Hz, but we have yet to confirm and identify them.


        The setup is shown in the diagram below. For each bandpass through SR560, we added the gain to the signal as much as possible without railing the signal. Note that in this setup we did not bandpass the signal from PD after we square it , as shown in previous entries. Because Mingyuan did not understand why would we need to and I could not answer him properly, so I agreed to let him have it his way.



          When we measured the data from the driven system (red curve in the plot), the setup is as shown in the diagram. However, for background measurement (blue curve in the plot), we want to keep the DC supply provided by the function generator to the pzt so that the sensitivity of the signal remain the same. Hence, we used a second function generator to send in similar driving voltage to the squaring box, while the first function generator was set to the dc output voltage to supply the pzts, no sinusoidal output.   (We made a mistake by just unplugging the Vdrive to the pzt and to the squaring box, and the noise level dropped so much.) 



     The red and blue curve shows the psd of the demodulated signal when the blades were driven, and the static case respectively. The peak at 4 Hz that presents in both cases are from the square of the driving signal at 2Hz.

     There are a few  peaks around 36 - 40 Hz when the blades were driven. We could not see this in the SR785 monitor because the monitor was so faint. I just saw this after I plotted the data.  The peaks might come from some resonances in the setup. We expect crackling noise to be more broad band. We will confirm and identify the source of the peak to make sure that we can see some signal from the driving (it can be rubbing between metal, pzt noise, crackle.)

We will repeat the same measurement, and try changing driving frequency/ amplitude, to see if the signal changes or not.

  216   Tue May 31 19:33:00 2011 taraDailyProgressCrackledata readout

By mingyuan, tara

We built a simple voltage summing circuit for adding DC level to the pzt. This circuit allows us to fine tune the inteferometer's differential arm length, so that we can operate at the fringe's maximum slope. Then we checked the peaks we observed from last time. It turned out to be harmonics from the common mode from driving.


The circuit schematic is shown below. The result Vout = Vin1 + Vin2. 



The adding circuit is used as shown in the schematic (highlighted in yellow.)


 *Later, we can use this summing circuit in a feedback control loop for locking the interferometer.

Then we used this circuit in the setup and repeat the measurement to check the peaks we observed last time. With the same setup, we observed the peaks again, but they probably are harmonics from 4Hz from common mode motion which was not perfectly cancelled.




     We repeated the measurement again with 0.7 Hz driving, and the peaks disappeared. The signal between driving and not driving the arms are very similar. The shape of the PSD changes slightly because of the lower amplitude of the driving signal, as we low pass the signal at 0.1 Hz.


We do need a seismic isolation and vacuum chamber. Right now, sound from people speaking in the lab can disturb the measurement.


 a few things we have to consider soon, before we use the maraging steel blades pulled down by a mass block in the experiment.

1) how should we push the blades?  capacitor plate? magnetic coil?

2) When can we move and get a better table, so that we can decide on seismic isolation stage.

3) We have to start looking for vacuum bell jar for the experiment.

4) lock the interferometer?

5) will we get an npro laser for the experiment?

  632   Fri Apr 26 16:04:56 2013 taraNoise HuntingNoise Budgetfrequency noise requirement for laser used in crackle experiment

I made an estimate for frequency noise requirement for a laser that can be used in crackle experiment. With some assumptions, I came up with df = 3x102 [Hz/rtHz ] for the requirement.

 The two beams from both arms are recombined at the output port of a Michelson interferometer. If it is operated at dark port, the output signal will be linear with the differential length between the two arms.

some assumptions in the calculation:

  • Operating at darkport
  • The laser has frequency = f0 + df  (carrier + noise)
  • mismatch between the two arms is ~ 1mm
  • aim for SNR = 1, no integration time.
  • crackle signal is ~10-15 m/rtHz, this is actually the shot noise limit of the current setup.


This will be a requirement for the planned ecdl.

Is a HeNe laser good enough? I'm not sure about HeNe frequency noise level, and I haven't found it in literature that much. I checked here,see fig 5, HeNe f noise is not so bad compared to NPRO noise (10^4 /f Hz/rtHz).This feels a bit counter intuitive. But if it is real, it should be ok for the measurement around 100 Hz and above.

  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.




  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

  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.

  193   Thu May 5 21:39:07 2011 tara,ryanThings to BuyBladesblade holding block

We made a drawing for a structure hat will hold the maraging blade. The details aren't complete yet. The holes for the clamping will be  identified,  but the sketch shows the rough idea.

     We want to clamp the blade to a structure. The drawing for the clamp will be provided by Ryan (he found it in the dcc.) The structure is consisted of the base and the pillar. Although a monolithic structure is better, it might be to expensive to carve out a big piece of Al block, so Koji suggested that we do it like this. The base will be mounted on the table, and the pillar will be mounted on the base by 4 screws. The height of the pillar is not decided yet. It depends on how big the Al mass block we need to pull down the blade by its weight, and how the mirror for reflecting the beam up will be mounted, but it should be around 6 - 8 inches.

    The mass block will be used for mounting the end mirror of the interferometer + a translational stage. This way we can steer the beam with 2 mirrors and adjust the arm length. We will determine the weight, so we can estimate the size of the mass block, assuming we will use Al.


Attachment 1: base.PDF
Attachment 2: pillar.PDF
  196   Mon May 9 22:25:26 2011 tara,ryan, mingyuanThings to BuyBladesblade holding block

 We made a sketch for the weight clamp that will carry the mass block on the end of the blades. This will be done in Solidwork tomorrow.


   We plan  to load a block of mass under the tip of the blade by using a pair of knife edge pieces so that the rubbing between the mass block and the blade is minimized.

 The edge of the blade cannot be too large, or it will be noisy when the blade is driven. On the other hands, if the blade angle is too small (sharper blade), the stress on the blade due to the weight will be too large and cause plastic deformation on the blade, which we don't want. We plan to make it flat ~ 1mm wide, with 120degree open angle.

 The yield tensile strength of maraging steel is ~ 1 -2 GPa. With the contact area at the knife edge we can calculate the maximum clamping force.

The width of the edge is ~ 5cm

The thickness of the edge ~ 1mm.

so the maximum force should not exceed ~ 1 GPa x 0.05 m x 0.001 m ~10^4 newton.

We will use spring washers to make sure that we do not tighten the clamps together with too much force and cause plastic deformation on the blade.



Attachment 1: IMG_1554.JPG
  197   Tue May 10 16:59:36 2011 tara,ryan, mingyuanThings to BuyBladesblade holding block

We finalized the drawing for blade clamping system. The drawings are posted here and in Crackle ATF Wiki. We will submit the drawings to the machine shop tomorrow.

         For each blade, the clamping system will consist of: 1)Steel base, 2)Steel pillar, 3) Steel top clamp, 4) Al knife edge top piece,5)Al knife edge bottom piece,and 6) Al end piece.

1) Steel base x1:   The steel base is 3"x3"x0.5" . It has 4 counter sunk holes that allow us to mount the steel pillar on it. It has 3" rails on both sides, so we can mount it on the table. Extra clamps can be used to hold the base on the table.

2) Steel pillar x1:   It is 5.5" height with 2"x2" square cross section.  There are 4 tapped 1/4-20 holes , 1" in depth, on the bottom for mounting it on the base. There are 2 tapped 3/8 , 1" in depth, on top for clamping two clamps along with the blade.

3) Steel top clamping piece x1, This will clamp the blade on the pillar.

4) Aluminum knife edge, top piece x1,

5) Aluminum knife edge, bottom piece x1: (4&5) The two knife edge pieces will be used for loading the mass block on the maraging blade tip. The explanation is written in this entry.

6) Aluminum end piece that holds the mirror mount on the blade tip x1: We want to have a steerable mirror for the IFO. So we need a mirror mount. The block will hold the mount and the blade tip together through screws. This piece is uploaded in the above entry.



 The assembly (without the blade and the mirror mount) is shown below.


Attachment 1: base.PDF
Attachment 2: pillar.PDF
Attachment 3: edge_bottom.PDF
Attachment 4: top_edge.PDF
  200   Wed May 11 22:42:28 2011 tara,ryan, mingyuanThings to BuyBladesblade holding block

We submitted the drawing to the machine shop today. The works should be done before May 23rd.


   The base/ pillar/ blade clamp will be made from stainless steel. The knife edge pieces and mirror mount at the blade tip will be made from aluminum.


  73   Tue Nov 6 23:45:38 2007 tobinConfigurationComputerstektronix scripts!
I cooked up a little script to fetch the data from the networked Tektronix scope. Example usage:

linux2:scripts>tektronix/tek-dump scope0 ch1 foo.csv

"scope0" is the hostname of the scope, "ch1" is the channel you want to dump, and "foo.csv" is the file you want to dump it to. The script is written in Python since Python's libhttp gave me less trouble than Perl's HTTP::Lite.
  341   Sat Sep 3 12:58:24 2011 valeraSummaryCrackleComments on Michelson ifo noise for crackle experiment

The laser noise measurement could have been compromised by clipping or scattering since we added the weight to the stack between the time when the Michelson noise was taken and the laser noise was measured. After that Dan found that the  stack was touching the chamber. So I suggest that the laser noise measurement should be repeated right after the low noise Michelson spectrum is achieved.


Here are some comments:

- The noise from Michelson ifo, that Dan posted yesterday, appeared to be just above the SR785 noise. But now Dan knows how to do the whitening to beat this noise down. The Michelson spectrum was not corrected for the loop gain. The voltage noise from Michelson was ~30nV/rtHz refered to the PD output at 100 Hz.  Today we measured the Thorlab PD100A dark noise to be around 15 nV/rtHz at 100 Hz (not bad for a cheap PD with ~10 V full range). We also tried to measure the laser intensity noise and found that we would expect it to be several times higher than the Michelson in-lock spectrum we got yesterday(?). The laser noise measurement was done by blocking one of the arms with a black glass dump. So the laser noise needs more investigation.

  6   Sat Oct 20 11:54:13 2007 waldmanOtherOMCOMC and OMC-SUS work
[Rich, Chub, Pinkesh, Chris, Sam]

Friday the 18th was a busy day in OMC land. Both DCPDs were mounted to the glass breadboard and the OMC-SUS structure was rebuilt to the point that an aluminum dummy mass is hanging, unbalanced. The OSEMs have not be put on the table cloth yet, but everything is hanging free. As for the DCPDs, if you recall one beam is 3mm off center from the DCPD tombstone. Fortunately, one DCPD is nearly 3mm offcenter from the case in the right direction, so the errors nearly cancel. The DCPD is too high, so the beam isn't quite centered, but they're close. We'll get photos of the beam positions in someday. Also, the DC gain between the two PDs is, at first glance, different by 15%. DCPD1, the one seen in transmission has 315 mV of signal while DCPD2 has 280 mV. Not sure why, could be because of beam alignment or tolerances in the Preamp or the angle incident on the diode or the QE of the diodes. The glass cans have *not* been removed.
  14   Thu Oct 25 17:52:45 2007 waldmanOtherOMCOMCs with QPDs
[Rich, Chub, Pinkesh, Sam]

Yesterday we got the QPD, OTAS, and PZT cabling harness integrated with the OMC. We found a few things out, not all of them good. The QPDs went on no problem and could be fairly well aligned by hand. We "aligned" them by looking at all four channels of the QPD on the scope and seeing that there is signal. Since the beam is omega = 0.5 mm, this is a reasonable adjustment. We then connected the OTAS connector to the OTAS and found that the heater on the OTAS was bonded on about 30 degrees rotated from its intended position. This rotated the connector into the beam and caused a visible amount of scattering. This wasn't really a disaster until I removed the connector from the heater and broke the heater off of the aluminum parts of the OTAS. Two steps backwards, one step forward. After the OMC, OMC-SUS integration test we will re-bond the heater to the aluminum using VacSeal. In the meantime, the OMC has been moved to Bridge 056 for integration with the OMC-SUS. More on that as we make progress.
  16   Thu Oct 25 23:35:36 2007 waldmanOtherOMCHang the OMC!
[Pinkesh, Sam]

We tried, convicted and hung the OMC today. The OMC was found guilty of being overweight, and unsymmetrically balanced. The unsymmetry was kind of expected and was corrected with a hefty stack of counterweights positioned over the counterweighting holes. The stacks will be measured at some future date and correctly sized objects machined. The overweightness showed up when the level hanging breadboard was about 5 mm low. This showed up in the board height above the table as well as the OSEM flag positions within their holes. The problem was remedied with a liposuction of the intermediate mass. We removed both small vertical cylinder weights that Chris added, and then we removed the heavy steel transverse weight that can be used to adjust the tip around the long axis (I forgot what its called).

The top of the breadboard ended up about 154 mm off the table. The breadboard is 39 mm thick, and the optics are centered (30 - 12.7) = 17.3 mm below the surface for a as hanging beams height of 154 -39 - 17.3 = 97.7 mm or about an 0.150 inches lower than we were aiming for. Can I get a refund?

We screwed up in multiple ways:
  • The slotted disks that capture the wires do not have the alignment bore used to center the wire in the hole
  • We didn't correctly route the far field QPD cable so it runs funny
  • We didn't have a tool which could be used to get two of the DCPD preamp box mounting screws (which are M3's chub!)
  • We don't have the cable clamps to tie off the electrical cables to the intermediate mass
  • We don't have any of the cabling from the OMC-SUS top to the rack so we can't test anything
  • We haven't uploaded pretty pictures for all to see

We left the OMC partially suspended by the OMC-SUS and partly resting on the installation lab jacks which are currently acting as EQ stops. After we fix the cabling we will more permanently hang it. PS, It looks like the REFL beam extraction will be tricky so we need to get on that....
Attachment 1: IMG_1483.jpg
Attachment 2: IMG_1481.jpg
  19   Fri Oct 26 17:34:43 2007 waldmanOtherOMCOMC + earthquake stops

[Chub, chris, Pinkesh, Sam]

Last night we hugn the OMC for the first time and came up with a bunch of pictures and some problems. Today we address some of the problems and, of course, make new problems. We replaced the flat slotted disks with the fitted slotted disks that are made to fit into the counterbore of the breadboard. This changed the balance slightly and required a more symmetric distribution of mass. It probably did not change the total mass very much. We did find that the amount of cable hanging down strongly affected the breadboard balance and may also have contributed to the changing balance.

We also attached earthquake stops and ran into a few problems:

  • The bottom plate of the EQ stops is too thick so that it bumps into the tombstones
  • The vertical member on the "waist" EQ stops is too close to the breadboard, possibly interfering with the REFL beam
  • The "waist" EQ stops are made from a thin plate that doesn't have enough thickness to mount helicoils in
  • Helicoil weren't loaded in the correct bottom EQ stops
  • The DCPD cable loops over the end EQ stop looking nasty but not actually making contact

However, with a little bit of jimmying, the EQ stops are arrayed at all points within a few mm of the breadboard. Meanwhile, Chub has cabled up all the satellite modules and DCPD modules and Pinkesh is working on getting data into the digital system so we can start playing games. Tonight, I intend to mount a laser in Rana's lab and fiber couple a beam into the 056 room so we can start testing the suspended OMC.
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