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  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

  819   Mon Aug 4 18:00:17 2014 xiaoyueDailyProgressCracklemicro cantilever

I made a micro-cantiliver out of SS340, single grain. Relocating the EBSD grain map in SEM is tricky, I used a self-defined coords system. However I will put the sample back for a EBSD analysis after making full use of this area:

re-locate.jpg

The cantilever is of size 860 nm * 6 um which mimics the real blade in ratio width : length = 1:7.

cantilever.png

I also made a micro-pillar (1 : 2.5 um) in order to compare the nano-pillar compressions to the nano-cantilever bending to see how the signature is different when the strain gradients are present.

1.03um_004.tif

Tests will be conducted soon. 

  829   Wed Aug 13 13:08:25 2014 xiaoyueDailyProgressCracklemicromechanical analysis of yielding

I compressed a pillar (D = 1.1 um, H = 2.5 um, made out of SS304 single grain) using G200 nanoindenter.

SS304_P1.jpg

Using inflection point I got F_yield  = 0.3 mN, and knowing the pillar diameter to be 1 um we can estimate yield stress ~ 0.3 mN / pi (0.55 um)^2 = 316 MPa

However a more conventional definition for yielding point is the “0.2% offset” where people draw a line with slope of elasticity from 0.2% strain, and find the first cross over to be the yielding ~ 0.4 mN/ pi(0.55um)^2 = 421 MPa

pillar_comress.png 

I would also love to compare the pillar compression data with the indentation data.

Indentation_Plot.png

In order to extrapolate yield stress information I need to convert the load vs. depth data to stress vs. strain ones. It involves a better knowledge of the indenter tip, as so far I got contradicting result from projected area function calibration and the tip radius claimed in the spec sheet (max projected area exceeds the claimed tip area). Also I need to learn more about how to find the actual “contact height” which excludes the non-plastic indentation from the machine loading depth.

  481   Thu Apr 26 17:17:23 2012 ranaDailyProgressCoating Qmodes found by tapping

Alastair and I popped the top on the can today and used a 3/16 balldriver to tap the optic and find the eigenfrequencies.

We achieved the ring up by lightly tapping the optic in a few different places; different taps give different modes.

Here are the list of frequencies (in kHz):

 2.696

 3.456

 4.68

 6.128

10.632

37.072

41.568

43.984

We used a few different spans, so I can't really say what the uncertainty in the frequency is.

The main finding here is that the frequencies are very different from the Blevins formulae as well as the COMSOL FEM. Perhaps we can use the measured frequencies to fix the FEM.

One feature of the disc geometry which I noticed for the first time: the edges are beveled. So this is not a right circular cylinder as we have assumed for the mode. I am also suspicious of the thickness measurements that Giordon made; the thickness of the disc should be measured at several points across the disc and the places indicated on a diagram.

Lid replaced and roughing pump restarted at ~5 PM. Hopefully we can measure in a few hours.

  584   Fri Oct 12 16:19:46 2012 janoschDailyProgressCrackleneed some changes

I disassembled the entire setup and put it back together again. I removed the rubber damping from the mirror attachments at the blades. If undamped attachment points are a problem, then we need another solution. The rubber was breaking into pieces and I am sure that it did not have a good effect on previous spectra. The mirrors attached to the blades were misaligned and covered by biochemicals. I cleaned the mirrors and aligned them again.

After realigning the rest of the interferometer, I was running some measurements of shadow sensors and photodiode signals. Locking the interferometer is still a problem, but it is not clear to me what the problem is. I think that the entire electronics part requires a bit more attention. The locking servo is still able to bring the photodiode signal into a low-variance state, but it is not clear if the interferometer is truely locked. In this "quasi locked" state and measured under vacuum (about 140mTorr), the photodiode spectra are without the usual features, but have a pretty smooth spectrum (see below). Even though this looks like something non-seismic / non-acoustic, there is still clearly response in time series to seismic disturbances (I have no idea where these end up in the spectra...).

So some more details about the locking problem. At the moment, a photodiode time series looks like this:

Lock_Flip.png

For a while (e.g. 1min) the variance is a bit higher, then there is a kick, and then the variance stays low all the time. Before and after the kick, the signal still shows seismic disturbances if I knock at the table. So somehow the locking servo drives the system into some strange state. The spectra before and after the kick don't show any of the typical seismic or acoustic features (left: before, right: after):

Photodiode_BeforeFlip.pngPhotodiode_AfterFlip.png

So it looks like we not able to lock the interferometer. Changing the offset of the locking servo, the DC component of the photodiode signal does not change. I am not sure what part of the system I should start to look at, but my guess is that there is a problem with the electronics and not so much with the mechanics. Anyway, maybe one of the friendly elog readers has an idea.

  1223   Mon Sep 14 19:57:33 2015 XiaoyueDailyProgressCracklenew PD ready to work in vacuum

I tested the PD output with the new wire-up but we still see the noise. We decided to make a few changes:

1. Seprate the grounds for each signal, so we have the 9-pin connector only for the whitened/ unwhitened signals, with the flat cable ordering in signal-ground-signal-... pairs. The PD power supplies now have its own flat cable clamping through the stages, and will join the suspension OSEMs cable at the first 25-pin connector.

2. Make the cabling as short as possible, so I decided to replace the flat cable outside vacuum with shielded and twisted cable with BNC connectors.

2. Short the PCB ground to the frame.

After making all these changes, we still see the same noise in oscilloscope. Federico suggested it could be a floating ground problem, so we short the optical table (frame) to the earth (wall power ground), which is the same ground shared with the oscilloscope. This largely reduced the noise. We checked also by plugging the oscilloscope to the power strip and short the table this time to the power strip ground. Noise is reduced again. So we are pretty sure this noise we see is fake due to floating ground, and will not been seen in ADC since it's differential.

Outputing the whitened PD signal to ADC channel, we no longer see the noise in time series: with / without PD signals, the AC readings look identical. Checking also in spectrum:

In the above spectrum, red is ADC reading with no input; blue is the one with whitened PD signal, laser OFF; green is the one with whitened PD signal, laser ON. Note the spectrum is taken in a "floating ground" condition -- that is the table is not shorted to the earth, neither the PCB board is shorted to the frame.

 

  1228   Wed Sep 16 02:31:35 2015 XiaoyueDailyProgressCracklenew PD ready to work in vacuum

[Federico, Gabriele, Xiaoyue] Gabriele and Federico pointed out that it's strange that in the spectra all three cases (no input, PD without light and PD with light) are sitting at a level of 1e-6. It's like we are only seeing ADC noise. We want to check if the DC output signal agrees with the level laser power on the PD: I measured directly at PD2 the laser power to be initially 0.11 mW. I cranked up the laser power so we have 1.47 mW on PD2. The DC output measured using oscilloscope is -1.10V which agrees with the power (mW) to output (V) calibration done before.

However I noticed that the whitened output responds very slowly to the laser power change, and both PD1, PD2 channels behave like the signals are low-passed! We checked the unwhitened signals and they are good as expected. So we took everything out of chamber for a thourough check: While checking the power supplies, we first found we have connection problem with the 3-pin connectors. We have to solder to make sure the cables have good conducting contact with the socket. Note this hasn't happend to the 2-pin connectors before. Then we connected a 12 kohm resistor to mimic the anode current input, and found the whitening stages (LT1128 chips) are indeed behaving like a low-pass filter. So we shortened the capacitor C43 to check if the op amp is working properly. With the oscillating Vout1 input, there's no output at all, so we are pretty sure the components are broken. We replaced the two LT1128's (U13, U14) and everything is back to normal. 

Quote:

I tested the PD output with the new wire-up but we still see the noise. We decided to make a few changes:

1. Seprate the grounds for each signal, so we have the 9-pin connector only for the whitened/ unwhitened signals, with the flat cable ordering in signal-ground-signal-... pairs. The PD power supplies now have its own flat cable clamping through the stages, and will join the suspension OSEMs cable at the first 25-pin connector.

2. Make the cabling as short as possible, so I decided to replace the flat cable outside vacuum with shielded and twisted cable with BNC connectors.

2. Short the PCB ground to the frame.

After making all these changes, we still see the same noise in oscilloscope. Federico suggested it could be a floating ground problem, so we short the optical table (frame) to the earth (wall power ground), which is the same ground shared with the oscilloscope. This largely reduced the noise. We checked also by plugging the oscilloscope to the power strip and short the table this time to the power strip ground. Noise is reduced again. So we are pretty sure this noise we see is fake due to floating ground, and will not been seen in ADC since it's differential.

Outputing the whitened PD signal to ADC channel, we no longer see the noise in time series: with / without PD signals, the AC readings look identical. Checking also in spectrum:

In the above spectrum, red is ADC reading with no input; blue is the one with whitened PD signal, laser OFF; green is the one with whitened PD signal, laser ON. Note the spectrum is taken in a "floating ground" condition -- that is the table is not shorted to the earth, neither the PCB board is shorted to the frame.

 

 

  230   Mon Jun 27 14:02:46 2011 Larisa Thorne and Vanessa AconDailyProgressCracklenew mass/mirror systems for ETMs

 [Vanessa]: To try to combat the problem of the end of the spring (the part between the mass clamp and the mirror clamp) oscillating at its own independent frequency (even when the mass is not moving), we are designing a setup that places the mirror on the bottom of the mass.  Attached are some of our ideas for the design parameters involved and the proposed design.

Other design problems include the dimensions of the attached mass/mirror set-up, because the larger the moment of inertia, the more apparent the undesired (horizontal) modes of oscillation.  So even if the height of the set-up is altered so the masses lie above the 45 degree mirror, this problem still must be dealt with.

ETA: I have attached a very slightly altered version of the design Larisa put up, for my own clarification.

After this we need to design/construct the mechanism to move the spring, which will be a controlled magnetic field (consisting of a small solenoid with an AC power source suspended above the spring) with a magnet (attached to the top of the spring) inside.

[Larisa]: As mentioned in my last post, it was found that attaching mirrors to the bottoms of the ETMs was the most viable option. Attached below is the final diagram of the concept design....

This model has a few advantages:

  • One can easily adjust the mass load on the blade spring by adding extra masses between the "blade bend compensating mass" and "mass end cap"
  • As mentioned before, having the mirror at the bottom of the mass eliminates the need to have the mass be exactly what is needed to have the blade bend exactly parallel to the optics table surface
  • Screw-spring mechanism will allow the mirror to be tilted , again eliminating the need for perfect blade parallelism to optics table

 

 

After taking a few measurements on the current setup, it was found that the necessary dimensions of the ETM mass (HA, redundancy!) would be severely limited by the height of the base block holding up the blade and the 45 degree tilted mirror that guides the laser beam to the ETM.

 

The Romulus blade spring will probably only need about 1350g mass to make the blade sufficiently straight, but the Remus blade will need much more mass (see Vanessa's post for exact numbers)

One idea I had was perhaps to pick a material that would be heavier than the masses used...after some calculations, I found the density of one of the masses on the Remus blade (1801g) to be ~11.340g/cm3 , which corresponds most closely to lead (~11.389g/cm3). It would seem that this is one of the most cost efficient materials (compared to, say, gold) to make the room-temperature solid masses out of (lead density was the highest among those listed on this solid materials table: see here)

The other possibility is that we vertically displace the base that the blade springs are clamped to. This way we will not have to worry about the dimensions of the masses, and can just have bigger lead masses made. 

  231   Wed Jun 29 10:50:21 2011 Larisa Thorne and Vanessa AconDailyProgressCracklenew mass/mirror systems for ETMs...version2.0

[Tara, Larisa]

As calculations for mass and dimensions began for the previous design, I found it to be unnecessarily complex and set about trying to design something simpler that would fulfill our needs just as well. A few attempts later, together with Tara, we came up with a much better design---->see first attachment:

  • it utilizes parts we already have in the lab (i.e., the mirror mount, larger aluminum(?) base)
  • one can easily adjust the blade-bending mass
  • there are minimal calculations involved, mostly because there are a lot less screws/holes to account for
  • because we have the additional larger aluminum(?) base, we are not as constrained height dimension-wise ---->see second attachment

[Vanessa]

I've added a mock-up of the new design, with dimensions, and labeled the parts we do not already have in dark red.  The particular mass values I gave are for the blade spring Remus.

Note that it is not necessary to construct a new (rectangular prism) lead mass for the spring Remus, but doing so will allow a reduction of the lead mass's height (right now, the lead mass is about 5.4 cm tall).

I think aluminum or some other light metal will work best for the side plate, so we do not create too much asymmetry in the system.  The mass end cap (also metal) can be of a  heavier metal, such as steel.

Also, since the mirror frame is L-shaped, we could put in two side screws to attach the frame to the metal plate above, creating more stability for the attached mirror.

  315   Tue Aug 16 13:25:31 2011 Yi and HaixingMiscSUSnew sensor design for maglev

As we mentioned in the earlier that OSEM constrained the position of working point
of the flag in our design, due to a slight drift of the equilibrium point in the horizontal
direction [as indicated by the figure below]:

 

In order to solve this issue, we have the following design for the sensing. This allows a flexible tuning of the
LED and PD in the horizontal direction and get the right position for sensing the flag motion.

The above scheme is not difficult to fabricate. We do not need to go to the mechanical shop and we can make them by
ourselves. Right now, we got the required components (LED, PD, Polycarbonate tube, and screws, and we need to find
something for the movable plate
).

If you have any better ideas, please let us know by commenting on this log.

  317   Tue Aug 16 23:45:38 2011 Yi and HaixingDailyProgressSUSnew sensors for maglev

We tried to make our new sensors as what we designed [as shown by the figure below]:

[The reason for this new design was posted on Elog 315]

We glued the LED and PD on aluminum plates and soldered wires on them [shown by the figure below]. As it turns out,
if we simple make the gap [for holding the plate] slightly smaller than the aluminum plate, we do not need extra screws to fix
the plate, which makes the scheme a lot simpler.

sensors.png

  260   Tue Jul 26 14:13:27 2011 haixingHowToSUSnumber of magnets need to achieve 1% imbalance

In Elog 256, we showed that the 1" magnets have a mean of 106 Gauss with a variance of 12.8 Gauss.
The question would be if we want to have an imbalance of 1% how many magnets we need to buy.Here
Here we will make an estimate by assuming that the distribution of strength is Gaussian---a reasonable assumption
given what we have measured. The distribution would simply be

with and . Through numerical integration, one can find out the probability content for the
magnet strength falling into [105, 107] (within the 1% error around the mean)  is 0.062. Therefore, if we want
to have 4 matched magnets that have 1% error around the mean, the number of magnets we need to order is
approximately 4/0.062 = 64. Since we have already got 12, extra 50 would be enough (the quantity that we order
today), unless we are not lucky.

Steve: I asked  K&J  Magnetics to select matched pairs of 4, but they declined.

  259   Tue Jul 26 13:48:11 2011 haixingSummarySUSorder list for maglev

Today, Steve helped me to order more magnets and other mechanical parts for the maglev.
The detailed items go as follows:
1.  1" diameter and 1/32" thickness magnets (Grade N42). Quantity: 50.  The Supplier: K & J magnetics
     [The reasoning for the quantity is due to its large variance in the magnet strength, as shown in the ELOG 256]
2.  1/2" diameter and 1/8" thickness magnets (Grade N42). Quantity: 20.  The Supplier: K & J magnetics
3.  1 pack of Brass fully threaded 1/2" rods [They are used as flags in the position sensing]
4.  4 packs of 5 precision stainless spring (0.18" outer diameter and 0.018 wire)  The size of the spring is choosen
     in such a way that it can fit into a 8-32 screw. [This is for the cross coupling measurement. With spring, we can
     first create a stable setup and measure the cross coupling by driving the levitated plate with coil (see the schematics below) ]
   
5.  4 packs of 5 precision stainless spring (0.18" outer diameter and 0.026 wire). This is another size for the same
     purpose of cross coupling.

In addition, I used techmart to order another BNC terminal block [with 18 analog inputs and 2 analog outputs. The
type is 2090A, and the link is given by http://sine.ni.com/nips/cds/view/p/lang/en/nid/203462] for the national instruments
DAC card. We had already got one in the basement lab. This new ordered one gives us additional two analog outputs.
In total, we will get four analog outputs which would be enough for the first-step digital control before Cymac
will be available in one month.



 

  151   Sat Jun 26 13:59:57 2010 Vladimir DergachevMiscSUSovernight tiltmeter plots
And here are the plots from overnight run:

https://ldas-jobs.ligo.caltech.edu/~volodya/tiltmeter/tw_driver3/preamp1b/

Notes:

* I picked a nice drift segment out of the whole run which showed some
junks in the beginning and a few near the end, possibly caused by external
effects.

* The drift with oscillations is still there. It is likely they are
mechanical:

https://ldas-jobs.ligo.caltech.edu/~volodya/tiltmeter/tw_driver3/preamp1b/coarse_tilt_vs_time.png

* The best spectrum comes from lvdt2. It is likely that LVDT1 receives
extra noise from clamping zeners in the fine channel of its preamplifier.

https://ldas-jobs.ligo.caltech.edu/~volodya/tiltmeter/tw_driver3/preamp1b/lvdt2_combined_spectrum_zoomed.png

* The full spectrum reaches the limit of the coarse channel only at
high frequencies:

https://ldas-jobs.ligo.caltech.edu/~volodya/tiltmeter/tw_driver3/preamp1b/lvdt2_combined_spectrum.png

The fine channel of LVDT2 dips a little bit lower, which is easier to
see on linear X scale:

https://ldas-jobs.ligo.caltech.edu/~volodya/tiltmeter/tw_driver3/preamp1b/lvdt2_combined_spectrum_linear.png

The electronics operates around 6.6 kHz and the conversion to DC is
done digitally. Thus we should see flat noise floor from it, except for
the effect of voltage references which are used both in ADCs and in the
triangle driver and any other noise source that affects the amplitude
(such as a current setting resistor in the triangle driver).

Riccardo - I think it would help to isolate the effects of mechanics
noise from driving electronics if we had a test fixture for LVDTs.
Something like a U bracket for the excitation part of the LVDT and a
screw-on cover for the pickup coil. It would be nice to have a choice
between a plain cover, a cover with a slot and a PEEK cover.

This essentially follows the suggestion Eric made at the last meeting,
except I would avoid usage of all-analog readout as I am not confident I
can debug it easily. We can still do it as a confirmation once we know
what the baseline curves are from our current system.
  173   Sun Jan 23 09:03:43 2011 JanComputingSeismometryphase offset NN<->xi

I just want to catch up on my conclusion that a single seismometer cannot be used to do the filtering of horizontal NN at the surface. The reason is that there is 90° phase delay of NN compared to ground displacement at the test mass. The first reaction to this shoulb be, "Why the hack phase delay? Wouldn't gravity perturbations become important before the seismic field reaches the TM?". The answer is surprising, but it is "No". The way NN builds up from plane waves does not show anything like phase advance. Then you may say that whatever is true for plane waves must be true for any other field since you can always expand your field into plane waves. This however is not true for reasons I am going to explain in a later post. All right, but to say that seismic dispalcement is 90° ahead of NN really depends on which directoin of NN you look at. The interferometer arm has a direcion e_x. Now the plane seismic wave is propagating along e_k. Now depending on e_k, you may get an additional "-" sign between seismic dispalcement and NN in the direction of e_x. This is the real show killer. If there was a universal 90° between seismic displacement and NN, then we could use a single seismometer to subtract NN. We would just take its data from 90° into the past. But now the problem is that we would need to look either 90° into the past or future depending on propagation direction of the seismic wave. And here two plots of a single-wave simulation. The first plots with -pi/2<angle(e_x,e_k)<pi/2, the second with pi/2<angle(e_x,e_k)<3*pi/2:

TimeSeries_fwd.jpgTimeSeries_bwd.jpg

 

  713   Thu Aug 15 23:19:36 2013 haixingNoise HuntingSUSpower spectrum and coherence of three hall effect sensors

The hall effect sensor is quite noisy, and I am trying to find where the noise comes from. The first I tried today is to measure the power spectrum and coherence among three hall effect sensors (in the vertical direction). Here is the result:

10.png(the unit for the power spectrum density is in digital volt per root hertz.)

I do not quite understand why there is almost no coherence (apart from the 60Hz power line), even though the power spectra are almost identical among these sensors.

Can someone shed some light where the issue is? Is the noise non-stationary or what?

--------Another measurement with fewer average---------------------

54.png

It seems that when the number of average is small, the coherence is large, an indication of non-stationary?

  740   Tue Oct 15 18:05:32 2013 nicolasLab InfrastructureSi Cantileverprobably a leak in my pump line

This is the pressure trend when I close off the valve between the pump line and the cryostat. I am not totally sure how to interpret this, but the fact that the pressure didn't go much lower (like the 10^-6 region) when the pump is only pumping the line makes me think that there may be a leak in my line. Something to investigate.

lineleak.png

  288   Tue Aug 9 18:11:24 2011 Larisa ThorneDailyProgressCrackleproblem solving: locking

Having assembled the full Michelson, attempts are being made to lock it. 

Attached are two pictures: the first is the Michelson without servo/feedback loop on. The second is the resulting waveform of the settings that got closest to a lock. Still playing with it....suspect that perhaps the solenoid of the magnetic actuator isn't able to handle as much power as needed. Might need to replace it with one that has more turns?

  532   Fri May 25 20:15:39 2012 ZachMiscCoating Qpump replaced

I put the pump back on the CQ tank. The pressure had only risen to 4 uTorr over a day of being sealed off, so I spooled up the Hi-Cube, opened the valve and then reengaged the large turbo.

  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.

  272   Tue Aug 2 19:49:23 2011 Larisa ThorneDailyProgressCracklequality (Q) factor, Remus cantilever blade springs

I have completed curve-fitting to get what I consider to be a reasonable estimate of the quality (Q) factor for the 'Remus' cantilever blade spring.

 

Sample MATLAB code is included below for the first data set of the 'Remus' blade.

I created two new functions, 'dampedsine.m' and 'chinew.m' to make the code 'findQ.m' work. Parameters in 'chinew.m' had to be changed for each new set of data. For each set of data there were 2 independent sets per cantilever blade spring so that we can compare them; see if they are similar...this is hopefully the indicator that the code is working as it should, not that the same errors per produced twice. In addition to having two separate data sets for each cantilever blade spring, I am including two plots: one with the whole range of data, one zoomed version so the level of accuracy can be understood visually.

 

If the formula for the curve fitting is  function=A+B*e^(-t/tau)*cos(w*t+phi)

If the formula for the quality (Q) factor is Q=pi*(w/(2*pi))*tau

And in the MATLAB code, the matrix 'xout' contains the respective values of the variables

then....

 

REM2:---------------------------

>> xout

xout =

    0.8934

    0.1779

  436.3865

   13.0989

    0.3746

 

>> QREM2

QREM2 =

   2.8581e+03

 

REM3:---------------------------

>> xout

xout =

    0.8884

    0.4516

  424.6310

   13.0978

    2.4434

 

>> QREM3

QREM3 =

   2.7809e+03

 

The only problem occurs when we consider the 'Romulus' cantilever blade spring. This is evident not only in the graph (we can see that the green line that represents the curve fitted line is oscillating but not damping), but also in the solution for the variables of the curve fitting and the calculated Q value, which is 3 orders of magnitude higher than those for the 'Remus' cantilever blade spring.

 ROM2:---------------------------

>> xout

xout =

   1.0e+05 *

    0.0000

    0.0000

    1.5785

    0.0001

   -0.0000

 

>> QROM2

QROM2 =

   1.0404e+06

  278   Fri Aug 5 14:11:08 2011 Larisa ThorneDailyProgressCracklequality (Q) factor, Romulus cantilever blade springs

Here are the last of the calculations for the quality (Q) factor of the cantilever blade springs: Romulus. I was having difficulties last time simply because I wasn't playing with the initial x conditions enough...

 

As before, I have collected two sets of data for the cantilever blade spring (called Q3, Q4 in the plot names). For each set, I have two plots: the first is a view of the full data curve with the curve fitting curve, and a second one that is just zoomed in to show how close the two are, visually. As you can see from the zoomed in view, the second set of oscillation data for the Romulus blade had many imperfections, which could explains why the difference in calculated Q's for the Romulus data set was larger than the difference in Q for the Remus cantilever blade.

 

I used the a version of the same code as for the Remus cantilever blade calculations, so I will not be redundant and post them here again.

 

 

 

ROM2, second go:---------------------------

>> xout

xout =

    0.8754

    0.7198

  408.3907

   13.1822

    5.2313

 

>> QROM2

QROM2 =

   2.6917e+03

 

ROM3:---------------------------

>> xout

xout =

    0.8813

    0.5866

  352.7866

   13.1829

   -0.0238

 

>> QROM3

QROM3 =

   2.3254e+03

  1872   Wed Dec 9 17:47:12 2020 PacoMiscElectronicsquick test of 14.75 MHz RFPD

On Monday, tested a 1998 (Rev. 0) RFPD originally found in Crackle (serial #010). Looks like it was first resonant at 24.493 MHz, but was later tuned for 14.75 MHz. I used the AG4395A network analyzer in CTN following the procedure in the previous ELOG post, splitting R output into the test input of the RFPD. Driving at up to -10dBm, couldn't see any resonant feature in the TF below 150 MHz. Tuning the inductor L1 made no difference. The regulator (U3 and U4 near bottom right in picture below) outputs were nominal.

I borrowed a flat response (DC to 125 MHz) PD from CTN lab (New Focus 1811) along with its power supply for short term use.

Below are some photos of the aformentioned RFPD. I added some kapton to keep dust off the PD.

  456   Sun Apr 15 22:22:56 2012 ranaMiscCoating Qre-aligned beam, restarted Turbo

There was some issue with the pumps apparently. Giordon will detail this in the elog very soon.

This evening, around 7:30, I restarted the turbo. The coarse gauge was bottomed out at 1 mTorr.

I turned on the laser and the HV. Then re-aligned the laser and the input and output optics and rebalanced the detectors.

Several of the mounts were loose: single screw, joints not tight, pointless use of a flipper mirror. All very sloppy - should be fixed Monday morning.

I have restarted a sweep from 20 - 22 kHz with 1 kV DC and 0.5 kVpk sine.

 

Wondering why we don't see any signal. Is the stress induced polarization modulation too small? Seems unlikely since we're almost shot noise limited in the readout. Perhaps the ESD force pattern is too weak or perhaps the ESD is broken (open rather than short) ?


Discussing with Calum and Alastair during Friday donuts, we thought we could possibly use the laser vibrometer.

Triggered by that, I wondered if we could just make a Michelson with the disk making the reflection for one arm.

Then this evening, I noticed that the reflection from the disk already has a fringing pattern in it; my guess is that this is from the two surfaces. Maybe this fringe signal already has the mode vibration in it?

  457   Mon Apr 16 11:08:19 2012 Giordon StarkMiscCoating Qre-aligned beam, restarted Turbo

The issue with the pumps was basically my fault. I misinterpreted what was meant by turning on the pump and had forgotten to turn on the backing pump first before the UHV pump. Alastair went ahead and fixed this and reset the error as well (thanks!)

I'll be making a few mechanical adjustments to the set-up today and making it less sloppy. The sweep that Rana did from 20-22 kHz doesn't reveal any modes:

20KRANA.png

As a reminder - we predict a mode around 21kHz and allowed for up to 5% error in frequency (5% of 21kHz is roughly 1kHz).

Quote:

There was some issue with the pumps apparently. Giordon will detail this in the elog very soon.

This evening, around 7:30, I restarted the turbo. The coarse gauge was bottomed out at 1 mTorr.

I turned on the laser and the HV. Then re-aligned the laser and the input and output optics and rebalanced the detectors.

Several of the mounts were loose: single screw, joints not tight, pointless use of a flipper mirror. All very sloppy - should be fixed Monday morning.

I have restarted a sweep from 20 - 22 kHz with 1 kV DC and 0.5 kVpk sine. 

Edit: currently have a sweep going 1kHz span centered at 21.4kHz.

  458   Mon Apr 16 13:32:18 2012 ZachMiscCoating Qre-aligned beam, restarted Turbo

Do you mean short rather than open?

We were considering the interferometric readout from the start, but the feeling was that we would just get killed by the CoM motion (pendulum, torsion, tilt, etc.). That was supposed to be one advantage of a transmission measurement.

I agree that the fringe we see is probably from the parallel disk surfaces. I'm having a hard time seeing how we could use this to our advantage, though. Judging by your COMSOL stuff, I wouldn't think there is a first-order displacement of the disk surfaces relative to each other for these modes. Also, if there was, we would have to be very careful about the yawing of the disk, and we'd also be sort of at the whim of the system in terms of whether the fringe is dark or bright or whatever without any stress.

Quote:

Wondering why we don't see any signal. Is the stress induced polarization modulation too small? Seems unlikely since we're almost shot noise limited in the readout. Perhaps the ESD force pattern is too weak or perhaps the ESD is broken (open rather than short) ?

Discussing with Calum and Alastair during Friday donuts, we thought we could possibly use the laser vibrometer.

Triggered by that, I wondered if we could just make a Michelson with the disk making the reflection for one arm.

Then this evening, I noticed that the reflection from the disk already has a fringing pattern in it; my guess is that this is from the two surfaces. Maybe this fringe signal already has the mode vibration in it?

 

  461   Mon Apr 16 18:37:02 2012 ranaMiscCoating Qre-aligned beam, restarted Turbo

Quote:

Do you mean short rather than open?

NO.

We were considering the interferometric readout from the start, but the feeling was that we would just get killed by the CoM motion (pendulum, torsion, tilt, etc.). That was supposed to be one advantage of a transmission measurement.

I don't see that it matters for the internal reflection.

I agree that the fringe we see is probably from the parallel disk surfaces. I'm having a hard time seeing how we could use this to our advantage, though. Judging by your COMSOL stuff, I wouldn't think there is a first-order displacement of the disk surfaces relative to each other for these modes. Also, if there was, we would have to be very careful about the yawing of the disk, and we'd also be sort of at the whim of the system in terms of whether the fringe is dark or bright or whatever without any stress.

 

We're at the whim, but mostly there seems to be a fringe. Since the disk surfaces are not parallel, there is a first order term (although small). Might as well try it since the other method gives squat so far. 

 

  463   Wed Apr 18 19:33:36 2012 ranaMiscCoating Qre-aligned beam, restarted Turbo

 There is, indeed, a giant resistor inside of that cast aluminum box which converts the output of the HV driver into a SHV connector.

Its a thick film, Ohmite, MOX-1125-23E. Which Google tells me may be somewhere from 1-1000000 kOhm. Need a Ohm-meter to measure it, but there's not one in the lab.

However, it could be that this is why we can't ring up any modes.

Pictures are in our Picasa account.

 

Our HV driver is a Matsusas AMT-5B20 (http://www.matsusada.com/high-voltage/ams/AMS.pdf). According to the data sheet (attached) it has these specs:

Vdc = -5000 to + 5000 V

Imax = 20 mA

Slew = 360 V/uS

-3 dB BW = 20 kHz (full scale) or 40 kHz (10% scale)

 

So its not bad; we should still be able to ring up the modes up to 100 kHz, although we just drive a little harder.

(Also, remember to electrically isolate the PDs from the table)

  464   Wed Apr 18 20:27:42 2012 Giordon StarkMiscCoating Qre-aligned beam, restarted Turbo

Quote:

 There is, indeed, a giant resistor inside of that cast aluminum box which converts the output of the HV driver into a SHV connector.

Its a thick film, Ohmite, MOX-1125-23E. Which Google tells me may be somewhere from 1-1000000 kOhm. Need a Ohm-meter to measure it, but there's not one in the lab.

However, I will be betting $5 that this is why we can't ring up any modes. Need to figure out a more clever way to current limit so that it doesn't completely filter out our drive.

How is the resistor involved in the SHV connector affecting the actual signal being driven? Aren't SHV connectors good for up to like 2 Amps of current? I'm assuming you're talking about the resistance here because the change in impedance at the connection between the output of the HV driver and the SHV connector is modulating our signal somewhat significantly (0 < T < 1).

Pictures are in our Picasa account.

Where's the Picasa account (or how do I find it?)

Our HV driver is a Matsusas AMT-5B20 (http://www.matsusada.com/high-voltage/ams/AMS.pdf). According to the data sheet (attached) it has these specs:

Vdc = -5000 to + 5000 V

Imax = 20 mA

Slew = 360 V/uS

-3 dB BW = 20 kHz (full scale) or 40 kHz (10% scale)

 

So its not bad; we should still be able to ring up the modes up to 100 kHz, although we just drive a little harder.

Wasn't the limit on our spectrum analyzer below 100kHz?

 

 

  466   Thu Apr 19 18:58:51 2012 ranaMiscCoating Qre-aligned beam, restarted Turbo

I measured the resistance of the resistor: ~10 MOhms.

The cable capacitance (measured from the driver side of the SHV cable) is 200 pF. This must include the cable capacitance + the ESD capacitance. I leave it to Giordon to calculate these to see if the measurement makes sense.

 

Then I took a transfer function from the input (Vcon-in) to the output SHV connector. To make sure it was safe, I first used a DVM to measure the SHV connector and dialed the front panel knob to minimize this voltage. Then I set the spectrum analyzer to have a source output of 2 mVpk and connected it to the HV driver input.

The transfer function shows a rolloff above ~1 kHz. However, I don't think its steep enough to be a big issue for us. I have saved this data on the box as data registers D3 & D4 for Giordon to download and plot.

Finally, I have started a wide sweep with everything back on. It looks like there are some resonances around 4 kHz. Need to do some careful pickup hunting to see if these are real or electronics. Hopefully Giordon will come into the lab and download this data to check. So far it has been repeatable twice so I think its not a fluke of the noise.

  469   Fri Apr 20 15:34:21 2012 Giordon StarkMiscCoating Qre-aligned beam, restarted Turbo

[Rana, Giordon]

Plots from Rana's sweeps (transfer function of the input (Vcon-in) to the output SHV connector; wide sweep showing resonances).

Quote:

Then I took a transfer function from the input (Vcon-in) to the output SHV connector. To make sure it was safe, I first used a DVM to measure the SHV connector and dialed the front panel knob to minimize this voltage. Then I set the spectrum analyzer to have a source output of 2 mVpk and connected it to the HV driver input.

D3D4.png

The transfer function shows a rolloff above ~1 kHz. However, I don't think its steep enough to be a big issue for us.

Finally, I have started a wide sweep with everything back on. It looks like there are some resonances around 4 kHz. Need to do some careful pickup hunting to see if these are real or electronics. So far it has been repeatable twice so I think its not a fluke of the noise.

CURR.png

 

  489   Tue May 1 12:00:51 2012 ranaMiscCoating Qre-running

 re-aligned optics for new position, balanced PDs, turned on HV, started a new sweep for 3.5 kHz

  490   Tue May 1 14:05:05 2012 ranaMiscCoating Qre-running

nothing visible, restarted sweep around 6 kHz and started up the Turbo at 13:58.

I also noticed that whoever is setting up the 'Remote' data taking is changing the input configuration of the channels of the SR785 into something non-sensical. Check your settings.

  491   Tue May 1 15:57:30 2012 ericqMiscCoating Qre-running

Quote:

nothing visible, restarted sweep around 6 kHz and started up the Turbo at 13:58.

I also noticed that whoever is setting up the 'Remote' data taking is changing the input configuration of the channels of the SR785 into something non-sensical. Check your settings.

 Nothing visible in the 6.07-6.17kHz range either. I'm starting one around the 10.6kHz range

  492   Tue May 1 17:16:26 2012 ZachMiscCoating Qre-running

To: Eric, Rana, Giordon

Why are we doing 100-Hz sweeps again? I thought we decided to focus on narrower sweeps about the frequencies that Rana & Alastair measured with the "screwdriver method". 800 pts over 100 Hz near 6 kHz is not enough resolution to see the modes we want.

Quote:

Quote:

nothing visible, restarted sweep around 6 kHz and started up the Turbo at 13:58.

I also noticed that whoever is setting up the 'Remote' data taking is changing the input configuration of the channels of the SR785 into something non-sensical. Check your settings.

 Nothing visible in the 6.07-6.17kHz range either. I'm starting one around the 10.6kHz range

 

  493   Tue May 1 17:34:15 2012 Giordon StarkMiscCoating Qre-running

I asked Eric about this - and I'm not sure I was convinced. The explanation was something like "even if we don't see the total width of the peak, we'll still see some sharp peak somewhere". I even explained that the line width (gamma) of the peaks are around 0.03 and 300-800 points over 100Hz only gives a resolution of 0.3ish (we're still an order of magnitude off).

Quote:

To: Eric, Rana, Giordon

Why are we doing 100-Hz sweeps again? I thought we decided to focus on narrower sweeps about the frequencies that Rana & Alastair measured with the "screwdriver method". 800 pts over 100 Hz near 6 kHz is not enough resolution to see the modes we want.

Quote:

Quote:

nothing visible, restarted sweep around 6 kHz and started up the Turbo at 13:58.

I also noticed that whoever is setting up the 'Remote' data taking is changing the input configuration of the channels of the SR785 into something non-sensical. Check your settings.

 Nothing visible in the 6.07-6.17kHz range either. I'm starting one around the 10.6kHz range

 

 

  494   Tue May 1 17:37:38 2012 ranaMiscCoating Qre-running

Appears to be fixed now - issue was the channel 1 input was set to be a differential "A-B" later on in the remote script - I removed that line and fixed it.

Quote:

I also noticed that whoever is setting up the 'Remote' data taking is changing the input configuration of the channels of the SR785 into something non-sensical. Check your settings.

 

  496   Tue May 1 17:44:58 2012 ZachMiscCoating Qre-running

If you were just measuring the power in some wide band (e.g., measuring a PSD with a bandwidth that is wider than the resonance), then I think what you're saying is true. That is, you'd see some frequency bin with a higher signal than its neighbors', and you could then choose to make a finer sweep around it.

Since you are measuring a transfer function, that is not true. You are trying to excite a narrow resonance with too coarse a sweep. Since the excitation signal is only being stepped in frequency by the same intervals as your resolution, the best you can hope for is that by some chance it happens to choose a point near the resonance for that one drive cycle. The odds of this are quite small.

Use finer resolution and look for the peaks Rana saw.

Quote:

I asked Eric about this - and I'm not sure I was convinced. The explanation was something like "even if we don't see the total width of the peak, we'll still see some sharp peak somewhere". I even explained that the line width (gamma) of the peaks are around 0.03 and 300-800 points over 100Hz only gives a resolution of 0.3ish (we're still an order of magnitude off).

 

 

 

  1899   Tue Feb 2 17:39:52 2021 PacoDailyProgressOpticsre: Figuring out how much astigmatism is hurting us

Motivated in part by the conclusions below, improved estimated mode matching efficiency from a poor 13% at the beginning of day to 48% (estimated using the reflection signal levels from the rfpd). What helped was walking the beam with the last two mirrors, and then scanning the cavity output coupler around to center the resonant mode which at this point seems optimal. This process was tedious, but effective apparently.

The distance between the two mirrors is ~ 45 mm which slightly undershoots the planned 47.5 mm which could limit the achievable 100% in simulation-land, but I'm moving on for now, hoping the lock will bump it up enough for the OPO threshold to be within our pump power range.

Quote:
  • Astigmatism should not be hurting us significantly.
  • The mode matching in principle can be improved in the experiment
  266   Wed Jul 27 17:38:09 2011 Vanessa AconMiscCracklere:blade noise plots

Quote:

Here is a Bode plot of the SR 780 (signal analyzer) data from last week.

 

I have attached the corresponding MATLAB code in the hopes that someone can tell me how to use the built in MATLAB 'bodeplot' function. As of now, the attached plots are not in correct Bode-format. That is, the magnitude plot should be in log-log, not log-linear form (I had to do it like this because MATLAB doesn't like putting negative numbers in logarithmic scale...)

 Hey Larisa, could you post the original data from the SR780, if you haven't already?  Thanks.

Also, can you just take the absolute value of the y-data, so you only take the real values and can plot on a log-log scale?

  268   Wed Jul 27 17:48:07 2011 Larisa ThorneMiscCracklere:blade noise plots

Quote:

Quote:

Here is a Bode plot of the SR 780 (signal analyzer) data from last week.

 

I have attached the corresponding MATLAB code in the hopes that someone can tell me how to use the built in MATLAB 'bodeplot' function. As of now, the attached plots are not in correct Bode-format. That is, the magnitude plot should be in log-log, not log-linear form (I had to do it like this because MATLAB doesn't like putting negative numbers in logarithmic scale...)

 Hey Larisa, could you post the original data from the SR780, if you haven't already?  Thanks.

Also, can you just take the absolute value of the y-data, so you only take the real values and can plot on a log-log scale?

SCRN0030.TXT: 7-22-2011, magnitude data (40 data points)

SCRN0031.TXT: 7-22-2011, phase data (40 data points)

 

SCRN0032.TXT: 7-25-2011, magnitude data (100 data points)

SCRN0033.TXT: 7-25-2011, phase data (100 data points)

 

SCRN0034.TXT: 7-25-2011, magnitude data (100 data points)

SCRN0035.TXT: 7-25-2011, phase data (100 data points)

 

I have just posted the plots, both magnitude and phase in log-linear form. We do not want to take the absolute value of the y-axis to solve the log-log problem as you suggest because this would make the plot confusing and unusable to the reader.

  180   Fri Jan 28 11:22:34 2011 JanComputingSeismometryrealistic noise model -> many problems

So far, the test mass noise was white noise such that SNR = NN/noise was about 10. Now the simulation generates more realistic TM noise with the following spectrum:

NoiseModel_TM.jpg

The time series look like:

Data_WA4f2_SW4f1.jpg

So the TM displacement is completely dominated by the low-frequency noise (which I cut off below 3Hz to avoid divergent noise). None of the TM noise is correlated with NN. Now this should be true for aLIGO since it is suspension-thermal and radiation-pressure noise limited at lowest frequencies, but who knows. If it was really limited by seismic noise, then we would also deal with the problem that NN and TM noise are correlated.

Anyway, changing to this more realistic TM noise means that nothing works anymore. The linear estimator tries to subtract the dominant low-frequency noise instead of NN. You cannot solve this problem simply by high-pass filtering the data. The NN subtraction problem becomes genuinely frequency-dependent. So what I will start to do now is to program a frequency-dependent linear estimator. I am really curious how well this is going to work. I also need to change my figures of merit. A simple plot of standard-deviation subtraction residuals will always look bad. This is because you cannot subtract any of the NN at lowest frequencies (since TM noise is so strong there). So I need to plot spectra of subtraction noise and make sure that the residuals lie below or at least close to the TM noise spectrum.

  280   Fri Aug 5 20:36:37 2011 Vanessa Acon and Larisa ThorneDailyProgressCrackleregarding presentations

ETA: Dang it, I was trying to resubmit this as a new entry so it wouldn't overwrite your old entry, sorry....

I reorganized the presentation outline a bit  - tell me what you think.

I'm still not sure where to stick the noise budget, since most of that discussion is math, not very good for a 25 minute talk, but it's seems important...  Maybe it should come before the chopping simulation discussion, because it makes sense that "since the crackling signal will probably be below all of this noise (point to noise budget) we need to use this chopping technique..."

 

Here is a presentation (the LIGO one at LLO in ~10 days) outline of what I hashed out with Vanessa this morning.

We will be presenting together as one report rather than two separate, consecutive reports. According to Ken Libbrecht, each individual presentation was to be 15 minutes, with 5 minutes for questions. We were thinking a single 25 minute composite talk, with the 5 minute question round afterwards. We tentatively assigned the person who would be talking about each topic...

Let red=Vanessa, blue=Larisa. Keep in mind, this is tentative and we haven't assigned everything yet!

 

Intro:

  • What is crackling noise? -- analogies, hysteresis, nonlinear energy upconversions, pictures
  • Why should be care about it? -- blade springs and LIGO

Experiment (this makes up the body of our talk):

  • What do we expect the signal to look like? How will we measure it? -- Basic Michelson explanation (using PZT setup as a simple initial model) and Chopping Simulation (crackling coefficients)
  • Characterizing the blade springs -- Measuring Q and resonant frequency (rough estimate and final measurements)
  • Initial Setup (Problems) -- Mirror-mass attachment design
  • Magnetic actuator design - math (optional), design/build -- compare to PZT use, why we switched
    • Transfer function measurement, feedback loop
  • Noise Budget -- electronics, shot, thermal, intensity, seismic noise

Where Are We Now? (And What's Next?)

  • Final Setup pictures
  • Summary of "Results"
    • Crackling predictions (crackling coefficients), noise budget
    • Spring characteristics -- Q, Transfer function
    • Ready for data collection!
  • Designing an experimental setup with even lower noise -- seismic isolation stack and vacuum chamber, ... a better laser
  • (optional) Adding to Noise Budget -- frequency noise, vacuum noise, (how noise will decrease with addition of chopping?)

 

  281   Fri Aug 5 21:17:58 2011 Larisa ThorneDailyProgressCrackleregarding presentations

Hit the "reply" button instead of the "edit" button next time... that way we can see earlier drafts of this.

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

 

Let red=Vanessa, blue=Larisa. Keep in mind, this is tentative and we haven't assigned everything yet!

 

Intro:

  • What is crackling noise? -- analogies, hysteresis, nonlinear energy upconversions, pictures
  • Why should we care about it? -- blade springs and LIGO

Experiment (this makes up the body of our talk):

  • Intro to PZT-Michelson version
  • Noise Budget using PZT setup info to make rough estimates. Maybe we could show just these by themselves, not all other things
  • Initial Setup (Problems) -- Mirror-mass attachment design
  • Measuring Q and resonant frequency (rough estimate and final measurements)
  • Magnetic actuator design - math (optional: just flick a screen of equations at them?), design/build -- compare to PZT use, why we switched
  • Transfer function measurement, feedback loop
  • Chopping Simulation (crackling coefficients, how noise will decrease with addition of chopping?) -- I put this here because the chopping circuit come physically after the PD in our Michelson, and it hasn't come up at any other time

Current status and Summary:

  • Final setup pictures
  • Final Noise Budget -- electronics, shot, thermal, intensity, seismic noise, frequency noise, vacuum noise
  • Crackling predictions (crackling coefficients) ----is this based on measurements we might do in the future ~2 weeks?
  • Designing an experimental setup with even lower noise -- seismic isolation stack and vacuum chamber, solid state laser

 

 

Comments: I moved some stuff around. Also changed some stuff because it seemed redundant (see changes to summary sub-bullets) or unnecessary (why would we talk about the seismic stack or the vacuum tank separately? What is there to say about it, other than, at most, one sentence?) Additionally, I just wanted to use this outline to list topics, you were going on ahead and sorting them. Slow down.

Hmm, I see too much red.

  • Quote:

    ETA: Dang it, I was trying to resubmit this as a new entry so it wouldn't overwrite your old entry, sorry....

    I reorganized the presentation outline a bit  - tell me what you think.

    I'm still not sure where to stick the noise budget, since most of that discussion is math, not very good for a 25 minute talk, but it's seems important...  Maybe it should come before the chopping simulation discussion, because it makes sense that "since the crackling signal will probably be below all of this noise (point to noise budget) we need to use this chopping technique..."

     

    Here is a presentation (the LIGO one at LLO in ~10 days) outline of what I hashed out with Vanessa this morning.

    We will be presenting together as one report rather than two separate, consecutive reports. According to Ken Libbrecht, each individual presentation was to be 15 minutes, with 5 minutes for questions. We were thinking a single 25 minute composite talk, with the 5 minute question round afterwards. We tentatively assigned the person who would be talking about each topic...

    Let red=Vanessa, blue=Larisa. Keep in mind, this is tentative and we haven't assigned everything yet!

     

    Intro:

    • What is crackling noise? -- analogies, hysteresis, nonlinear energy upconversions, pictures
    • Why should be care about it? -- blade springs and LIGO

    Experiment (this makes up the body of our talk):

    • What do we expect the signal to look like? How will we measure it? -- Basic Michelson explanation (using PZT setup as a simple initial model) and Chopping Simulation (crackling coefficients)
    • Characterizing the blade springs -- Measuring Q and resonant frequency (rough estimate and final measurements)
    • Initial Setup (Problems) -- Mirror-mass attachment design
    • Magnetic actuator design - math (optional), design/build -- compare to PZT use, why we switched
      • Transfer function measurement, feedback loop
    • Noise Budget -- electronics, shot, thermal, intensity, seismic noise

    Where Are We Now? (And What's Next?)

    • Final Setup pictures
    • Summary of "Results"
      • Crackling predictions (crackling coefficients), noise budget
      • Spring characteristics -- Q, Transfer function
      • Ready for data collection!
    • Designing an experimental setup with even lower noise -- seismic isolation stack and vacuum chamber, ... a better laser
    • (optional) Adding to Noise Budget -- frequency noise, vacuum noise, (how noise will decrease with addition of chopping?)

     

 

  282   Mon Aug 8 10:54:59 2011 Vanessa AconDailyProgressCrackleregarding presentations

 

Intro:

  • What is crackling noise? -- nonlinear energy upconversion, Barkhausen Noise (not just hysteresis), earthquakes, pictures
  • Why should we care about it? -- blade springs and LIGO

Experiment (this makes up the body of our talk):

  • How will we measure it? Intro to Michelson: PZT version as simple analogy
    • (the PZT noise budget is essentially useless, we should probably just drop it unless we have excess time)
  • Switching to Springs
    • Characterizing the springs: Measuring Q and resonant frequency (rough estimate (optional) and final measurements)
  • Initial Setup with springs (Problems) 
    • Mirror-mass attachment design
    • Magnetic actuator design - math (optional: just flick a screen of equations at them?), design/build -- compare to PZT use, why we switched
      • Transfer function measurement, feedback loop (since the transfer function we are measuring is of the motion of the spring over the motion of the magnetic actuator)
  • How will we measure it (part II)?
    • Noise Budget -- electronics, shot, thermal, intensity, seismic noise -- (I don't have frequency noise or vacuum noise yet, those are under future things to do.  And Noise Budget should come before Chopping because the whole point of Chopping is to extract a signal below the noise floor.)
    • Chopping Simulation (how do we expect the signal to look, how will we extract it from beneath the noise floor, crackling coefficients, [how noise will decrease with addition of chopping? - I don't know the answer to this, actually])

Current status and Summary and Future Work:

  • Final setup pictures - on seismic stacks, with mirror attachment and magnetic actuator, and vacuum chamber
  • Crackling predictions (crackling coefficients) -- These crackling predictions are a necessary part to design the chopping technique, since they tell us what signal to demodulate by; they should not be in the summary.
  • Designing an experimental setup with even lower noise -- seismic isolation stack and vacuum chamber, solid state laser

 

I moved the noise budget back into the main body, since it should come before chopping.  Also it seems like poor presentation conduct not to have at least a very very brief summary of the main points - I assume we'll summarize a bit while we show them final setup pictures.  We have to sort the topics eventually anyway, I'm not sure why you would un-sort them...  It's easier to design the powerpoint this way, and it's important to know the logical connections between each topic and the motivation behind speaking about them.

Since two of my items are optional, there's actually more blue than red...  If you want, you can also discuss the mirror-attachment design, since you did that nice model?  However if you do that you'll basically be talking for the entire first half of the presentation.

The reason I split up the seismic isolation and the vacuum chamber was because I figured (1) we need to split up the summary/future work anyway and (2) I did a (very tentative) look at how the seismic isolation stack would decrease the noise on the noise budget and how we would measure that more accurately in the future, so I figured I should talk about that when it comes up.

Quote:

Hit the "reply" button instead of the "edit" button next time... that way we can see earlier drafts of this.

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

 

Let red=Vanessa, blue=Larisa. Keep in mind, this is tentative and we haven't assigned everything yet!

 

Intro:

  • What is crackling noise? -- analogies, hysteresis, nonlinear energy upconversions, pictures
  • Why should we care about it? -- blade springs and LIGO

Experiment (this makes up the body of our talk):

  • Intro to PZT-Michelson version
  • Noise Budget using PZT setup info to make rough estimates. Maybe we could show just these by themselves, not all other things
  • Initial Setup (Problems) -- Mirror-mass attachment design
  • Measuring Q and resonant frequency (rough estimate and final measurements)
  • Magnetic actuator design - math (optional: just flick a screen of equations at them?), design/build -- compare to PZT use, why we switched
  • Transfer function measurement, feedback loop
  • Chopping Simulation (crackling coefficients, how noise will decrease with addition of chopping?) -- I put this here because the chopping circuit come physically after the PD in our Michelson, and it hasn't come up at any other time

Current status and Summary:

  • Final setup pictures
  • Final Noise Budget -- electronics, shot, thermal, intensity, seismic noise, frequency noise, vacuum noise
  • Crackling predictions (crackling coefficients) ----is this based on measurements we might do in the future ~2 weeks?
  • Designing an experimental setup with even lower noise -- seismic isolation stack and vacuum chamber, solid state laser

 

 

Comments: I moved some stuff around. Also changed some stuff because it seemed redundant (see changes to summary sub-bullets) or unnecessary (why would we talk about the seismic stack or the vacuum tank separately? What is there to say about it, other than, at most, one sentence?) Additionally, I just wanted to use this outline to list topics, you were going on ahead and sorting them. Slow down.

Hmm, I see too much red.

  • Quote:

    ETA: Dang it, I was trying to resubmit this as a new entry so it wouldn't overwrite your old entry, sorry....

    I reorganized the presentation outline a bit  - tell me what you think.

    I'm still not sure where to stick the noise budget, since most of that discussion is math, not very good for a 25 minute talk, but it's seems important...  Maybe it should come before the chopping simulation discussion, because it makes sense that "since the crackling signal will probably be below all of this noise (point to noise budget) we need to use this chopping technique..."

     

    Here is a presentation (the LIGO one at LLO in ~10 days) outline of what I hashed out with Vanessa this morning.

    We will be presenting together as one report rather than two separate, consecutive reports. According to Ken Libbrecht, each individual presentation was to be 15 minutes, with 5 minutes for questions. We were thinking a single 25 minute composite talk, with the 5 minute question round afterwards. We tentatively assigned the person who would be talking about each topic...

    Let red=Vanessa, blue=Larisa. Keep in mind, this is tentative and we haven't assigned everything yet!

     

    Intro:

    • What is crackling noise? -- analogies, hysteresis, nonlinear energy upconversions, pictures
    • Why should be care about it? -- blade springs and LIGO

    Experiment (this makes up the body of our talk):

    • What do we expect the signal to look like? How will we measure it? -- Basic Michelson explanation (using PZT setup as a simple initial model) and Chopping Simulation (crackling coefficients)
    • Characterizing the blade springs -- Measuring Q and resonant frequency (rough estimate and final measurements)
    • Initial Setup (Problems) -- Mirror-mass attachment design
    • Magnetic actuator design - math (optional), design/build -- compare to PZT use, why we switched
      • Transfer function measurement, feedback loop
    • Noise Budget -- electronics, shot, thermal, intensity, seismic noise

    Where Are We Now? (And What's Next?)

    • Final Setup pictures
    • Summary of "Results"
      • Crackling predictions (crackling coefficients), noise budget
      • Spring characteristics -- Q, Transfer function
      • Ready for data collection!
    • Designing an experimental setup with even lower noise -- seismic isolation stack and vacuum chamber, ... a better laser
    • (optional) Adding to Noise Budget -- frequency noise, vacuum noise, (how noise will decrease with addition of chopping?)

     

 

 

 

  283   Mon Aug 8 13:35:14 2011 Larisa ThorneDailyProgressCrackleregarding presentations

Your rough estimate of the Q measurement could be a good thing to talk about; I think it's good to show an initial estimate before going into the final measurement...it lends more credence to the final measurement if the numbers are quite close.

What we do with the mirror-mass design doesn't matter much. EIther of us could do it; but yes, showing the 3D model would be good. I just wish there were some way of making maybe a short video clip so we (the viewer) could go and see the object from all sides.

The final noise budget and chopping at the end of the body of the talk will be all yours, and I imagine that will take up a good chunk of time itself. If that's the order we will be doing it in, maybe I should do some of the bit that comes after it (in the conclusion). Maybe not necessarily for the pictures of the final setup...we could just flick through those and show them... but I could do the cackling coefficient stuff, then when we move on to improvements, you could do the seismic isolation and I'd do the vacuum tank:

Current status and Summary and Future Work:

  • Final setup pictures - on seismic stacks, with mirror attachment and magnetic actuator, and vacuum chamber --just show them without much talking
  • Crackling predictions (crackling coefficients) -- These crackling predictions are a necessary part to design the chopping technique, since they tell us what signal to demodulate by; they should not be in the summary.
  • Designing an experimental setup with even lower noise -seismic isolation stack and vacuum chamber, solid state laser

 

I saw that you've started working on the Powerpoint this morning. I am working on the transfer function bit (I will have to consult with Seiji a bit before this is completely done), and will send you the material to incorporate. What else should I be doing? Everything that is currently blue?

  247   Tue Jul 19 19:53:31 2011 Larisa ThorneDailyProgressCracklerepeat Q experiment

This is a repeat experiment of what was done here.

The difference this time was that instead of letting the HeNe laser path bounce off the bottom side of the hanging mass, I adjusted the path so that it would hit the corner of the clamp holding the hanging mass to the blade itself. The advantage to this is that there motion there is mostly "spring" motion, not "pendulum" motion with multiple modes that we do not want included. The disadvantage is that the motion will be much less (smaller), but this is negligible in light of the advantages. Also, the clamp is affixed slightly closer to the free end of each blade during the experiment.

 

I will attach the data, graphs and pictures of the setup at a later time. 

Once I have published these, I will continue to work on 'curve fitting' these to solve for the Q values of both blades. This involves guessing a similar curve function and comparing it to the data points, as well as the use of the 'fminsearch' function in MATLAB. More on this when I figure it out...all I have currently is a bunch of error messages...

  271   Mon Aug 1 19:30:42 2011 Larisa ThorneDailyProgressCracklereport copy

 I know it's not LaTeX-y, but I figure it would be a good idea to leave a copy of what got sent in.

  772   Wed Feb 12 11:13:01 2014 xiaoyueDailyProgressCrackleseismic noise coupling characterization

In order to study the current setup better to improve the design of the 2nd version experiment, I did some seismic coupling analysis. The plan is to shake the optical table with a white noise (5V, pre-amplified with a bandwidth 10-1k Hz, input 0.5A, 2V) mini-shaker (B&K type 4810), while the motion of the table is monitored by a 3-axis accelerometer. A full description of the seismic noise picture should include analysis of the coupling from table motion to Mich signal, bench (damped by rubbers) inside the chamber to Mich signal, and we also want to characterize different coupling from bench to different optical elements.

The first and easiest thing I tried is to characterize the transfer function between table vibration and Mich signal. The table was shaken in x, y, and z directions separately, with hopefully three linearly independent measurements of a_x, a_y, and a_z measured for each 1hr shaking. In this way we built matrix [a_xx, a_xy, a_xz; a_yx, a_yy, a_yz; a_zx, a_zy, a_zz] where the additional index indicates the shaking direction. With [e_x, e_y, e_z] for each shaking measured by servo, simply solve [a_xx, a_xy, a_xz; a_yx, a_yy, a_yz; a_zx, a_zy, a_zz][T_x, T_y, T_z] = [e_x, e_y, e_z] will give us the transfer function along x, y and z. 

coh8_140128_fit.png

The picture is plotted with coherence between a_ii (where i is the driving direction) and mich signal is larger than 0.8. the result seems to agree with our expectation that the seismic noise transfer function follows the power law trend. 

However, the coherence is very bad. I tried increasing the noise power by limiting bandwidth to 10 - 300 Hz and inputing 0.8A 3.0V to the shaker). From the result of the z-drive result, the coherence in low frequency range is improved a lot, so I am going to finish the three-axial analysis. While the last trial of data is fit by 1/f^2, the later trial is better fit by 1/f^3, but this kind of fit is tricky. There are many resonances and it is difficult to judge which fit is the best. 

driveZ_fit.png

 

I tried superimposing the two and they are similar where both of them have good coherence.

superimpose.png

I also did analysis (keep data with coherence > 0.8) for the coupling from directly the bench motion to optical elements. I mounted another mini-accelerometer on the newport mirror mount and clamp it to the table like what we did inside the chamber.

coh8_140207.png

x has a generally higher level because the accelerometer is mounted along x-direction on the mirror mount. It seems that the transfer function is much smaller than one, which probably indicates a difference in calibration between the two signals. I will at some point mount the accelerometer one next to the other and measure the relative calibration, which should be simply a flat transfer function. 

Another problem here is that I got very bad coherence at low frequency. I have no good explanation why there seems to be a high-pass cutoff around 30 Hz, but we definitely need to push the measurement down to 10 Hz. 

  594   Wed Oct 24 16:13:34 2012 haixingDailyProgressSUSsignal conditioning circuit design and pcb layout

During last few days, I designed the signal conditioning circuit for the hall effect sensors maglev. It mainly contains two parts:

1. The constant gain part.

2. The dewhitening part. It contains two types of high pass filters: one has a zero at 0.5 Hz and pole at 5 Hz, the other one has zero at 5Hz and pole at 50Hz. Due to the uncertainty in the shape of the signal (the floating plate motion), I put them in series (add one additional place holder) and also add jumpers to bypass the intermediate stage if necessary for possible modifications.

The schematics is shown in the attached pdf file: [signal_conditioning_hall_effect_sensor_2channels.pdf].

The Altium file for the schematics and pcb layout is also attached [signal_conditioning_hall_effect_sensor.zip], which uses the multiple channel design idea.

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