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ID Date Author Type Categoryup Subject
  11472   Thu Jul 30 19:12:52 2015 IgnacioUpdateIOOYAW and PIT WFS Wiener filtering

Rana pointed out that another way to mitigate seismic motion at in the mode cleaner would be to look at the YAW and PITCH output  channels of the WFS sensors that control the angular alignment of the mode cleaner. 

I downloaded 45 mins of data from the following two channels:



And did some quick offline Wiener filtering with no preweighting, the results are shown in the PSD's below,


I'm quite surprised at the Wiener subtraction obtained for the YAW signal, it required no preweighting and there is about an order of magnitude improvement in our region of interest, 1-3 Hz. The PIT channel didn't do so bad either.


Attachment 1: YAW.png
Attachment 2: PIT.png
  11488   Mon Aug 10 22:18:19 2015 IgnacioUpdateIOOReady to do some online mode cleaner subtraction

I'm attaching a SISO IIR Wiener filter here for reference purposes that will go online either tonight or tomorrow evening. This is a first test to convince myself that I can get this to work, MISO IIR filters are close to being ready and will soon be employed. 

This Wiener filter uses the STS-X channel as a witness and MCL as target. The bode plot for the filter is shown below,

The performance of the FIR and IIR Wiener filters and the ammount of subtraction achive for MCL is shown below,


Output from quack to be loaded with foton: filter.zip

K bye.

Attachment 1: stsx.png
Attachment 2: performance.png
Attachment 3: filter.zip
  11492   Tue Aug 11 11:30:19 2015 IgnacioUpdateIOOSISO (T240-X) FF of MCL

Last night we finally got some online subtraction going. The filter used is described in the post this eLOG is @eLOG 11488

The results were as follow:

The filter worked as expected when subtracting noise out of MCL,

There is about a factor of 6 subtraction at the ~3Hz resonant peak. The static IIR filter predicted a factor of 6-7 subtraction of this peak as well.

The 1.2 Hz resenonant feature improved by a factor of 3. This should improve quite drastically when I implement the y-channel of the T240 seismo.

There is some high frequency noise being injected, not very noticeable, but present. 

We then took a look at the power in the MC when the filter was on,

The power being transmitted in the cavity was not as stable as with the feedforward on. We believe that the filter is not at fault for this as Eric mentioned to me that the MC2 actuator lacked some sort of compensation that I need to understand a bit better.

YARM was then locked when the filter was on and we took a look at how it was doing. There was stationary sound arising from the locking of the YARM, leading us to believe that the filter might have injected some noise in the signal. IT DID.

The filter injected nasty high frequency noise at YARM from 11 Hz and on. This is to be expected since the filter did not roll off to zero at high frequencies. Implementing a 1/f rolloff should mitigate some of the injected noise.

 Also, as one can see above, subtraction by around a factor of 2 or so, was induced by the mode cleaner feedforward subtraction.

Attachment 1: MCL.png
Attachment 2: MCTRANS.png
Attachment 3: YARM.png
  11495   Tue Aug 11 18:43:42 2015 JessicaUpdateIOOMCL Online Subtraction

Today I finished fitting the transfer function to a vectfit model for seismometers T240_X and T240_Y, and then used these to filter noise online from the mode cleaner. 

The Bode plot for T240_X is in figure 1, and T240_Y is in figure 2. I made sure to weight the edges of the fit so that no DC coupling or excessive injection of high frequency noise occurs at the edges of the fit.

I used C1:IOO-MC_L_DQ as the first channel I filtered, with C1:IOO-MC_L_DQ(RMS) for RMS data. I took reference data first, without my filter on. I then turned the filter on and took data from the same channel again. The filtered data, plotted in red, subtracted from the reference and did not inject noise anywhere in the mode cleaner. 

I also looked at C1:LSC-YARM_OUT_DQ and C1:LSC-YARM_OUT_DQ(RMS) for its RMS to see if noise was being injected into the Y-Arm when my filter was implemented. I took reference data here also, shown in blue, and compared it to data taken with the filter on. My filter, in pink, subtracted from the Y-Arm and injected no noise in the region up to 10 Hz, and only minimal noise at frequencies ~80 Hz. Frequencies this high are noisy and difficult to filter anyways, so the noise injection was minimal in the Y-Arm. 

Attachment 1: SeisX_bode.png
Attachment 2: SeisY_bode.png
Attachment 3: MCL_first.png
Attachment 4: Yarm_first.png
  11496   Wed Aug 12 01:32:18 2015 IgnacioUpdateIOOImproved SISO (T240-X) FF of MCL

In my previous elog:11492, I stated that in order to improve the subtraction and reduce the injection of high frequency noise we want the filter's magnitude to have a 1/f rolloff.

I implemented this scheme on the filter SISO filter previously analyzed. The results are shown below.

The filters bode plot:

The nice 1/f rollof is the main change here. Everything else remained pretty much the same.

The predicted FIR and IIR subtractions:

Everything looks right but that hump at 8 Hz. I used 8 pairs of poles/zeros to get this subtraction.

The online MCL subtraction:

This looks better than I expected. One has to keep in mind that I ran this at 1 AM. I wonder how well this filter will do during the noisier hours of the day. The RMS at high frequencies doesn't look great, there will definitely be noise being injected into the YARM signal at high frequencies.

Measuring the YARM signal:

There is still noise being injected on YARM but it is definitely much better than the previous filter. I'm thinking about doing some IIR subtraction on the arms now to see if I can get rid of the noise that is being injected that way, but before I embark on that quest I will rething my prefiltering.

The plot below shows the ratio of the unfiltered versus filtered ASDs for the FIR and IIR subtraction predictions as well as for the measured online IIR subtraction. Positive dB means better subtraction.

Attachment 1: filter.png
Attachment 2: stsx.png
Attachment 3: mclonline.png
Attachment 4: yarmonline.png
Attachment 5: sub.png
  11499   Wed Aug 12 16:39:46 2015 IgnacioUpdateIOOMISO WIener (T240-X and T240-Y) FF of MCL

Last night I performed some MISO FF on MCL using the T240-X and T240-Y as witnesses. Here are the results:





Training data + Predicted FIR and IIR subtraction:

Online subtraction results:


Subtraction performace:

Attachment 1: stsx.png
Attachment 2: stsy.png
Attachment 3: performance.png
Attachment 4: sub.png
Attachment 5: mcliir.png
Attachment 6: yarmiir.png
  11500   Wed Aug 12 16:48:26 2015 IgnacioUpdateIOOBetter? Nope. MISO WIener (T240-X and T240-Y) FF of MCL

Last night, I also worked on a "better" (an improvement, I thought) of the MISO Wiener filter (T240-X and T240-Y witnesses) IIR filter. The FF results are shown below:





Training data + Predicted FIR and IIR subtraction:

Online subtraction results:


Subtraction performace:

 Although the predicted FIR and IIR results are "better" than the previous MISO filter, the subtraction performance for this filter is marginally better if not worse (both peak at 15 dB, in slightly different regions). 

Attachment 1: stsx.png
Attachment 2: stsy.png
Attachment 3: performance.png
Attachment 4: mcliir.png
Attachment 5: yarmiir.png
Attachment 6: sub.png
  11501   Wed Aug 12 22:33:36 2015 IgnacioUpdateIOORe-measured MC2 -> MCL TF

Since I will need to do transfer function measurements in order to implement FF for the arms and the MC2's yaw and pitch channels, I decided to practice this by replicating the transfer function measurement Eric did for MC2 to MCL. I followed his procedure and the data that I aquired for the TF looked as shown below,

About five minutes of data were taken (0.05 Hz resolution, 25 averages) by injecting noise from 1 to 100 Hz. The TF coherence looked as below,

Attachment 1: bode_TF.png
Attachment 2: Coherence.png
  11502   Thu Aug 13 12:06:39 2015 Jessica SummaryIOOBetter predicted subtraction did not work as well Online

Yesterday I adjusted the preweighting of my IIR fit to the transfer function of MC2, and also managed to reduce the number of poles and zeros from 8 to 6, giving a smoother rolloff. The bode plots are pictured here:

The predicted IIR subtraction was very close to the predicted FIR subtraction, so I thought these coefficients would lead to a better online filter.

However, the actual subtraction of the MCL was not as good and noise was injected into the Y arm.

The final comparison of the subtraction factors between the online and offline data showed that the preweighting, while it improved the offline subtraction, needs more work to improve the online subtraction also.

Attachment 1: newBodeX.png
Attachment 2: newBodeY.png
Attachment 3: pred_Sub.png
Attachment 4: MCLSub.png
Attachment 5: YarmSub.png
Attachment 6: comparison.png
  11516   Wed Aug 19 01:45:10 2015 IgnacioUpdateIOODoubly Improved SISO (T240-X) FF of MCL

Today I tried and doubly-improved SISO FF filter on MCL. This filter has a stronger rolloff than the previous SISO filters I have tried. The rolloff most definelty helped towards reducing the ammount of noise being injected into YARM. Below is the usual stuff:



T240-X (SISO)



Training data + Predicted FIR and IIR subtraction:


Online subtraction results:


Subtraction performace:

  11519   Thu Aug 20 11:09:10 2015 ranaUpdateIOOsome points about seismic FF
  • When plotting the subtraction performance, we mainly care about the 0.5 - 10 Hz band, so we care about the RMS in this band. Don't integrate over the whole band.
  • When calculating the Wiener filter, you must use the pre-weighting so as to not let the Wiener residual be dominated by the out of band signals. We don't want the filter to try to do anything outside of the 0.5 - 10 Hz band.
  • Somehow, we want to assign a penalty for the filter to have high frequency gain. We do NOT want to slap on an ad-hoc low pass filter. The point of the Wiener filtering is to make the optimum.
  • What is the reason for the poor filter performance from 0.5 - 2 Hz ? If we use the frequency domain (Dmass) subtraction technique, we can do better, so there's some inefficiency in this process.
  • we're getting too much of the 3 Hz stack mode coupling into MCL. I think this means that our damping filters should be using RG around the suspension eigenmodes rather than just simple velocity damping. We had this years ago, but it caused some weird interaction with the angular loops...to be puzzled out.
  11522   Fri Aug 21 08:38:37 2015 SteveUpdateIOOPMC locked

PMC needed to be locked manually.cheeky

Attachment 1: PMClocked.png
  11529   Tue Aug 25 16:09:54 2015 ericqUpdateIOOIMC Tweak

A little more information about the IMC loop tweak...

I increased the overall IMC loop gain by 4dB, and decreased the FAST gain (which determines the PZT/EOM crossover) by 3dB. This changed the AO transfer function from the blue trace to the green trace in the first plot. This changed the CARM loop open loop TF shape from the unfortunate blue shape to the more pleasing green shape in the second plot. The red trace is the addition of one super boost. 


Oddly, these transfer functions look a bit different than what I measured in March (ELOG 11167), which itself differed from the shaping done December of 2014 (ELOG 10841). 

I haven't yet attempted any 1F handoff of the PRMI since relocking, but back when Jenne and I did so in April, the lock was definitely less stable. My suspicion is that we may need more CARM supression; we never computed the loop gain requirement that ensures that the residual CARM fluctuations witnessed by, say, REFL55 are small enough to use as a reliable PRMI sensor.

I should be able to come up with this with data from last night. 

Attachment 1: imcTweak.pdf
Attachment 2: CARM_TF.pdf
  11532   Thu Aug 27 01:41:41 2015 IgnacioUpdateIOOTriply Improved SISO (T240-X) FF of MCL

Earlier today I constructed yet another SISO filter for MCL. The one thing that stands out about this filter is its strong roll off wink. This prevents high frequency noise injection into YARM. The caviat, filter performance suffered broken heart quite a bit, but there is subtraction going on.

I have realized that Vectfit lacks the ability of constraining the fits it produces, (AC coupling, rolloff, etc) even with very nitpicky weighting. So the way I used vectfit to produce this filter will be explained in a future eLOG, I think it might be promising. 

Anyways, the usual plots are shown below. 



T240-X (SISO)



Training data + Predicted FIR and IIR subtraction:


Online subtraction results:(High freq. stuff shown for noise injection evaluation of the filter)


Subtraction performace:


  11535   Fri Aug 28 00:59:55 2015 IgnacioUpdateIOOFinal SISO FF Wiener Filter for MCL

This is my final SISO Wiener filter for MCL that uses the T240-X seismo as its witness.

The main difference between this filter and the one on elog:11532 is the actual 1/f rolloff this filter pocesses. My last filter had a pair of complex zeroes at 2kHz, that gave the filter some unusual behavior at high frequencies, thanks Vectfit. This filter has 10 poles and 8 zeroes, something Vectfit doesn't allow for and needs to be done manually.

The nice thing about this filter is the fact that Eric and I turned this filter on during his 40 min PRFPMI lock last night, Spectra for this is coming soon.

This filter lives on the static Wiener path on the OAF machine, MCL to MC2, filter bank 7.

Anyways, the usual plots are shown below. 



T240-X (SISO)


Training data + Predicted FIR and IIR subtraction:


Online subtraction results:(High freq. stuff shown for noise injection evaluation of the filter)



Subtraction performace:

  11538   Fri Aug 28 19:05:53 2015 ranaUpdateIOOIMC Tweak

Well, green looks better than blue, but it makes the PCDRIVE go high, which means its starting to saturate the EOM drive. So we can't just maximize the phase margin in the PZT/EOM crossover. We have to take into account the EOM drive spectrum and its RMS.

Also, your gain bump seems suspicious. See my TF measurements of the crossover in December. Maybe you were saturating the EOM in your TF ?

Lets find out what's happening with FSS servos over in Bridge and then modify ours to be less unstable.

  11539   Fri Aug 28 20:15:49 2015 ranaUpdateIOOMC2 -> MCL Actuator TF

I made a measurement of the MC2 actuator transfer function by injecting noise from 1-100Hz into LSC_MC2_EXC for about 15 minutes, then estimating the TF from MC2_OUT to IOO_MC_L with CSD/PSD. The inverse of this TF will be applied to their Wiener target data to give us the direct subtration filter we want.

I think what happened here is you forgot to undo the MC_F whitening filter which is the Generic Pentek Interface board next to the MC servo board. I suggest you guys measure this on Monday so you can correctly estimate the MC length noise. And then perhaps undo the whitening in the anti-whitening filter of this filter bank so that the signal which is recorded is in units of kHz.

This should allow your online subtraction filter to be more correct: roughly speaking, the phase shift below a pole or zero is going to be 45*(f/fp) deg. Since we expect there to be 2 zeros at 15 Hz, it would be 9 deg phase shift at 1.5 Hz and limit the subtraction to ~80%.

  11541   Sat Aug 29 04:53:24 2015 IgnacioUpdateIOOMCL Wiener Feedforward Final Results

After fighting relentlessly with the mode cleaner, I believe I have achieved final results

I have mostly been focusing on Wiener filtering MCL with a SISO Wiener filter for a reason, simplicity. This simplicity allowed me to understand the dificulties of getting a filter to work on the online system properly and to develope a systematic way of making this online Wiener filters. The next logical step after achieving my final SISO Wiener filter using the T240-X seismometer as witness for MCL (see elog:11535) and learning how to produce good conditioned Wiener filters was to give MISO Wiener filtering of MCL a try. 

I tried performing some MISO filtering on MCL using the T240-X and T240-Y as witnesses but the procedure that I used to develope the Wiener filters did not work as well here. I made the decision to ditch it and use some of the training data I saved when the SISO (T240-X) filter was runing overnight to develope another SISO Wiener filter for MCL but this time using T240-Y as witness. I will compare how much more we gain when doing MISO Wiener filtering compared to just a bunch of SISO filtering in series, maybe a lot, or little.

I left both filters running overnight in order to get trainining data for arm and WFS yaw and pitch subtractions.

The SISO filters for MCL are shown below:

The theoretical FIR and IIR subtractions using the above filters:


Running the filters on the online system gave the following subtractions for MCL and YARM:


Comparing the subtractions using only the T240-X filter versus the T240-X and T240-Y:



  11542   Sun Aug 30 00:03:13 2015 ranaUpdateIOOMCL Wiener Feedforward Final Results

Somehow it seems like the ELOG makes all of the thumbnails way too big by default. Did we get some sneaky upgrade recently?

I would only plot your results below 50 Hz. We don't care about the RMS at high frequencies and it can make the RMS misleading.

We definitely need to include one vertical Wilconox at each MC chamber so that it can subtract all of that junk at 10-20 Hz.

  11543   Sun Aug 30 10:57:29 2015 IgnacioUpdateIOOMCL Wiener Feedforward Final Results

Big thumbnails? Could it have been this? elog:11498.

Anyways, I fixed the plots and plotted an RMS that can actaully be read in my original eLOG. I'll see what can be done with the MC1 and MC2 Wilcoxon (z-channel) for online subtractions. 

  11544   Sun Aug 30 12:20:08 2015 ericqUpdateIOOMCL Wiener Feedforward Final Results

Big thumbnails? Could it have been this? elog:11498.

Ignacio is correct; I forgot to shrink the value back down after testing the PDF thumbnails. Default thumbnail size is now back to 600px. 

  11545   Sun Aug 30 13:31:48 2015 ranaUpdateIOOMCL Wiener Feedforward Final Results

I'm not totally sure, but by eyeball, this seems like the best online MCL reduction we've ever had. Nice work.

The 3 Hz performance is the same as usual, but we've never had such good 1 Hz reduction in the online subtraction.

I would like to see a plot of the X & Y arm control signals with only the MCL filter ON/OFF. This would tell us how much of the arm signals were truly frequency noise.

  11546   Sun Aug 30 13:55:09 2015 IgnacioUpdateIOOSummary pages MCF

The summary pages show the effect of the MCL FF on MCF (left Aug 26, right Aug 30):


I'm not too sure what you meant by plotting the X & Y arm control signals with only the MCL filter ON/OFF. Do you mean plotting the control signals with ONLY the T-240Y MCL FF filter on/off? The one that reduced noise at 1Hz?



  11547   Sun Aug 30 23:47:02 2015 IgnacioUpdateIOOMISO Wiener Filtering of MCL

I decided to give MISO Wiener filtering a try again. This time around I managed to get working filters. The overall performance of these MISO filters is much better than the SISO I constructed on elog:11541 .

The procedure I used to develope the SISO filters did not work well for the construction of these MISO filters. I found a way, even more systematic than what I had before to work around Vectfit's annoyances and get the filters in working condition. I'll explain it in another eLOG post.

Anyways, here are the MISO filters for MCL using the T240-X and T240-Y as witnesses:

 Now the theoretical offline prediction:



The online subtractions for MCL, YARM and XARM. I show the SISO subtraction for reference.

 And the subtraction performance:

  11548   Mon Aug 31 07:49:11 2015 ericqUpdateIOOMC2 -> MCL Actuator TF

I think what happened here is you forgot to undo the MC_F whitening filter which is the Generic Pentek Interface board next to the MC servo board. I suggest you guys measure this on Monday so you can correctly estimate the MC length noise. And then perhaps undo the whitening in the anti-whitening filter of this filter bank so that the signal which is recorded is in units of kHz.

This should allow your online subtraction filter to be more correct: roughly speaking, the phase shift below a pole or zero is going to be 45*(f/fp) deg. Since we expect there to be 2 zeros at 15 Hz, it would be 9 deg phase shift at 1.5 Hz and limit the subtraction to ~80%.

While it is true that the whitening filter was incorrectly handled, I don't think this should change the subtraction performance since the MC_L data used for the Wiener filter training was also taken without undoing the whitening filter.

  11549   Mon Aug 31 09:36:05 2015 IgnacioUpdateIOOMISO Wiener Filtering of MCL

MISO Wiener filters for MCL kept the mode cleaner locked for a good 8+ hours.

  11550   Mon Aug 31 14:15:23 2015 IgnacioUpdateIOOMeasured the MC_F whitening poles/zeroes

I measured the 15 Hz zero and the 150 Hz pole for the whitening filter channels of the Generic Pentek board in the IOO rack. The table below gives these zero/pole pairs for each of the 8 channels of the board.

channel zero [Hz] pole [Hz] Chan
1 15.02 151.05 C1:ASC-POP_QPD_YAW
2 15.09 150.29 C1:ASC-POP_QPD_PIT
3 14.98 150.69 C1:ASC-POP_QPD_SUM
4 14.91 147.65 C1:ALS-TRX
5 15.03 151.19 C1:ALS-TRY
6 15.01 150.51 ---
7 14.95 150.50 C1:IOO-MC_L
8 15.03 150.93 C1:IOO-MC_F

Here is a plot of one of the measured transfer functions,

and the measured data is attached here: Data.zip

EQ: I've added the current channels going through this board. 

More importantly, I found that the jumpers on channel one (QPD X) were set to no whitening, in contrast to all other channels. Thus, the POP QPD YAW signals we've been using for who knows how long have been distorted by dewhitening. This has now been fixed. 

Hence, the current state of this board is that the first whitening stage is disabled for all channels and the second stage is engaged, with the above parameters. 

Attachment 1: Data.zip
  11553   Tue Sep 1 10:26:24 2015 IgnacioUpdateIOOMore MCL Subtractions (Post FF)

Using the training data that was collected during the MISO MCL FF. I decided to look at more MCL subtractions but this time using the accelerometers as Rana suggested.

I first plotted the coherence between MCL and all six accelerometers and the T240-Z seismometer.

For 1 - 5 Hz, based on coherence, I decided to do SISO Wiener filtering with ACC2X and MISO Wiener filtering with ACC2X and ACC1Y. The offline subtractions were as follows (RMS plotted from 0.1 to 10 Hz):

The subtractions above look very much like what you would get offline when using the T240(X,Y) seismometeres during MISO Wiener filtering. But this data was taken with the MISO filters on. This sort of shows the performance deterioration when one does the online subtractions. This is not surprising since the online subtraction performance for the MISO filters, was not too great at 3 Hz. I showed this in some other ELOG but I show it again here for reference:

Anyways, foor 10 - 20 Hz, again based on coherence, I decided to do SISO Wiener filtering with ACC2Z and MISO Wiener filtering with ACC2Z and ACC1Z (RMS plotted from 10 to 20 Hz):

I will try out these subtractions online by today. I'm still debating wether the MISO subtractions shown here are worth the Vectfit shananigans. The SISO subtractions look good enough.

Attachment 4: mclxycoh.png
  11555   Tue Sep 1 11:56:56 2015 ericqUpdateIOOIMC loop shapes

I took some transfer functions of the IMC loop and crossover, being careful that the PC drive never exceeding 1V during the measurements. 

I then did some algebra to try and back out the individual loop paths, without having to make assumptions/approximations about the loop gain being high enough. This only really works in the region where both the open loop and crossover measurements have coherence. 

It seems to me that the PZT path has pretty low phase margin on its own, but maybe this is ok, since its never really meant to run solo. The EOM path shape is harder to understand.


The data I took, and code that made the above plot is attached. This afternoon, I'll post an update comparing the measured OLG and crossover to earlier measurements. 

Attachment 1: IMCshapes_Aug31_2015.pdf
Attachment 2: IMC_Aug31_2015.zip
  11558   Wed Sep 2 01:31:22 2015 ericqUpdateIOOIMC loop shapes

The promised historical comparisons follow. The crossover looks mostly the same as before. There is a new feature in the OLG at 50-60kHz; what could've changed about the EOM path in that time?


Attachment 1: imc_olg_trend.pdf
Attachment 2: imc_xover_trend.pdf
  11561   Thu Sep 3 00:14:09 2015 ranaConfigurationIOOIMC fast gain change for lock acq

The IMC often was making that scratchy noise when first catching lock and sometimes breaking. Thinking of the crappy crossover sit that EQ showed in his latest plots, I decided that it didn't make sense to acquire lock with an unstable PZT/EOM crossover, so I have changed mcdown to acquire with +13 dB Fast Gain and its much fast now and no longer makes that sound.

I also changed the caput command from 'caput -l' to 'caput -c -l' to see if the async 'wait for callback' feature will insure that the commands get sent. I witnessed the mcdown not actually writing all of its commands once or twice tonight. With the MC Boost left on its never going to lock.

mcdown has been committed to SVN. Please, if you have recently edit mcup and Autolock, commit them to the SVN or else I will delete them and do an svn up.

  11563   Thu Sep 3 00:45:25 2015 IgnacioUpdateIOORemeasured MC2 to MCL TF + Improved subtraction performance

Today, I remeasured the transfer function for MC2 to MCL in order to improve the subtraction performance for MCL and to quantify just how precisely it needs to be.

Here is the fit, and the measured coherence. Data is also attached here: TF.zip


OMG, I forgot to post the data and any residuals. LOL!

The transfer function was fitted using vectfit with a weighting based on coherence being greater than 0.95.

I then used the following filters to do FF on MCL online:

Here are the results:

Performance has definelty increased when compared to previous filters. The reason why I think we still have poor performance at 3 Hz, is 1) When I remeasured the transfer function, Eric and I were expecting to see a difference on its shape due to the whitening filters that were loaded a couple days ago. 2) Assuming the transfer function is correct, there is poor coherence at 3 Hz 3) The predicted IIR subtraction is worst at this frequency.

Attachment 1: TF.zip
  11576   Fri Sep 4 10:25:19 2015 SteveConfigurationIOOAOM stage is ready

New stage can hold the correct polarization.

DRAWING CORRECTION:  Post block height was lowered to be 1.88" from 2.0"

Attachment 1: stage_AOM-EOM.jpg
Attachment 2: A-EOMholder.pdf
A-EOMholder.pdf A-EOMholder.pdf A-EOMholder.pdf A-EOMholder.pdf
  11581   Mon Sep 7 18:25:16 2015 ranaConfigurationIOOAOM stage is ready

The new stage missed the right height by ~2 mm. sad

Even if I completely bottom out the (New Focus 9071) 4-axis stage, its not short enough. So I removed the AOM from the beam and re-aligned into the PMC.

Steve, please get the aluminum piece remachined to go down by 2.5 mm so we can have some height adjustment room.


New stage can cheeky hold the correct polarization.

Also, the turning mirror mount just after the EOM and before the AOM is a U-100 and we want it to be a Suprema for stability - let's not forget to swap that after Steve gets the mount fixed.

  11583   Tue Sep 8 20:30:44 2015 ranaUpdateIOOMC WFS relief re-commissioned

I converted our MC WFS relief from CSH to BASH today. I also added 'wait' commands and 'echo' commands so that all DoFs run in parallel nicely. It can be accessed from the MC WFS screen.

I increased the overall MC WFS gain input slider from 0.02 to 0.1 (its in the mcwfson script). The MC Trans loops now have a time constant of ~30 seconds. The relief script relieves ~90% of the MC WFS control signals in the 2 minutes that its allowed to run.

On the next upgrade, we should make it python and have it kill the relief process if the MC loses lock before relief is applied via the alignment sliders.

Attachment 1: WFSrelief.png
  11584   Wed Sep 9 11:00:49 2015 IgnacioUpdateIOOLast Wiener MCL subtractions

On Thursday night (sorry for the late elog) I decided to give the MCL FF one more try. 

I first remeasured the actuator transfer function because previous measurements had poor coherence ~0.5 - 0.7  at 3 Hz. I did a sine swept to measure the TF. 

Raw transfer function:

The data is attached here: TF.zip

Then I made Wiener filters by fitting the transfer function data with coherence > 0.95 (on the left). Fitting all the data (on the right). Here are the filters:


The offline subtractions (high coh fit on left, all data fit on right). Notice the better IIR performance when all the TF data was fitted.


The online results: (these were aquired by taking five DTT measurements with 15 averages each and then taking the mean of these measurements)


And the subtraction performance:


Attachment 3: TF.zip
  11590   Thu Sep 10 09:37:34 2015 IgnacioSummaryIOOFilters left on MCL static module

The following MCL filters were left loaded in the T240-X and T240-Y FF filter modules (filters go in pairs, both on):

FM7: SISO filters for MCL elog:11541

FM8: MISO v1 elog:11547

FM9: MISO v1.1 Small improvement over MISO v1

FM10 MISO v2 elog:11563

FM5 MISO v3.1 elog:11584 (best one)

FM6 MISO 3.1.1 elog:11584 (second best one)


  11592   Sun Sep 13 13:26:00 2015 ranaUpdateIOOLast Wiener MCL subtractions

When making the Wiener filter OFF/ON comparisons, we want to use the median PSD estimates, not the mean (which is what pwelch gives you).

cf. Sujan's note and Evan's follow-up

The median will be less sensitive to the transients / gltiches and will show more improvement I think.

  11595   Mon Sep 14 21:42:00 2015 ranaUpdateIOOMC Wiener + Summary

I turned on the MCF FF in the OAF today (we need to fix the labeling of the 'ON' buttons on the RHS of the screen). The performance is still good; before / after attached.

Not only is the 1 Hz performance in the MC still good, but the X & Y arm noise reduction is ~1 order of magnitude. Good to know that the filters aren't changing much with time.

Can we just leave this on all the time now? Seems to be OK and there's no visible increase in the arm noise with this on.

Also did some updates to the summary pages and added a CDS FEC tab for CPU times.

Please take a look at the summary pages and bring a list of demands to the Wednesday meeting.

Attachment 1: mcf.pdf
  11634   Tue Sep 22 16:42:39 2015 ericqUpdateIOOHousekeeping

I've moved the OAF MC2 signal path to go directly from c1oaf to c1mcs, so that the LSC being ON/OFF doesn't interfere with the MC length seismic feedforward. Since the FB is currently down, I can't do a full test, but looking at monitor points in StripTool indicates it's working as intended. 

I also cleaned up some LSC medm stuff; exposing the existing SRCL UGF servo, and removing a misleading arrow. This reminds me that I need to get calibration lockins back up and running...

  11682   Fri Oct 9 16:43:50 2015 ericqUpdateIOOWeird IMC behavior

A few minutes ago, Gautam and I were poking around the IOO rack, looking at where he should power his frequency divider box, and what ADC innputs to use. 

Looking at the mode cleaner signals, it looks like we may have jostled something in a good way. Weird. 

  11713   Mon Oct 26 18:10:38 2015 IgnacioUpdateIOOLast Wiener MCL subtractions

As per Eric's request, here is the code and TF measurement that was used to calculate the MC2 FF filter that is loaded in FM5. This filter module has the filter with the best subtraction performance that was achieved for MCL.


Attachment 1: code_TF.zip
  11720   Wed Oct 28 14:07:44 2015 KojiUpdateIOOMC WFS Offsets update

MC WFS offsets were updated to have a better operating point.

  11759   Thu Nov 12 16:00:55 2015 ericqUpdateIOOPSL Laser turned back on

We found the PSL laser switched off. Looking at the wall StripTool, it looks like this happened about 4 hours ago. Gautam was working at and around the PSL table, and I suspect he accidently ran into the Big Red Button. 

We turned the laser back on.

  11773   Tue Nov 17 15:49:23 2015 KojiConfigurationIOOMC Autolocker modified

/opt/rtcds/caltech/c1/scripts/MC/AutoLockMC.csh  was modified last night.

1. Autolocker sometimes forget to turn off the MC2Tickle. I added the following lines to make sure to turn it off.

    echo autolockMCmain: MC locked, nothing for me to do >> ${lfnam}
    echo just in case turn off MC2 tickle >> ${lfnam}

2. During the lock acquisition, Autolocker frequently stuck on a weak mode. So the following lines were added
so that the Autolocker toggles the servo switch while waiting for the lock.

    echo autolockMCmain: Mon=$mclockstatus, Waiting for MC to lock .. >> ${lfnam}
    # Turn off MC Servo Input button
    ezcawrite C1:IOO-MC_SW1 1
    date >> ${lfnam}
    sleep 0.5;
    # Turn on MC Servo Input button
    ezcawrite C1:IOO-MC_SW1 0
    sleep 0.5;

  11794   Sat Nov 21 00:45:30 2015 KojiUpdateIOOIMC fix

Based on the observation of the PMC error signal, I started measuring the IMC OLTF. Immediately, it was found that the overall IMC loop gain was too low.
The UGF was ~40kHz, which was really marginal. It had been >100kHz when I have adjusted it about a year ago. (Next entry for the detail)

The first obvious thing was that the SMA cables around the IMC servo have visible degradation (Attatched photos).
I jiggled the signal cable from the demodulator Q_out to the MC servo. The openloop gain seemed fluctuating (increased) based on the cabling.
I decided to repair these cables by adding solder on the shield.

Even after the repair, the open loop TF didn't show any improvement. I checked the LO level and found that it was -16.7dBm.

I traced the problem down to the frequency generator unit (T1000461). The front panel of the unit indicates the output power for the 29.5MHz output is 13dBm,
while measurement showed it was 6~8dBm (fluctuating). The T1000461 document describes that there is only a wenzel oscillator inside. Does this mean the oscillatorwas degraded??? We need to open the box.

I was not sure what was the LO level. I naively assumed the input is 0dBm. Reducing the attenuation of the dial on the AM Stabilizer unit from 12dB attn to 0dB.
This made the LO level -3.3dBm.

Later at home, I thought this nominal LO level of 0dBm could have been wrong.

The demodulator circuit (D990511) has the amplifier ERA-5 (G=~20dB) at the input. Between the input and the ERA-5 there is a pattern for an attenuator.
Assuming we have no attenuator, the ERA-5 has to spit out 20dBm. That is too much for this chip. I need to pull out the box to see how much is the nominal LO for this box using an active probe.

This decrease/increase of the LO level affects the WFS demod too. According to D980233-B, the input stage has the comparator chip AD96687, which can handle differential voltage of 5.5V.
Therefore the effect is minimal.

Attachment 1: PDRFsignal_cable.JPG
Attachment 2: Qsignal_cable1.JPG
Attachment 3: Qsignal_cable2.JPG
Attachment 4: Qsignal_cable3.JPG
  11795   Sat Nov 21 00:46:33 2015 KojiUpdateIOOIMC OLTF

Here is the comparison before and after the fix.

Before the work, the UGF was ~40kHz. The phase margin was ~5deg. This caused huge bump of the frequency noise.

After the LO power increase, I had to reduce the MC loop gain (VCO Gain) from 18dB to 6dB. This resulted 4dB (x2.5) increase of the OLTF. This means that my fix increased the optical gain by 16dB (x6.3). The resulting UGF and phase mergin were measured to be 117kHz and 31deg, respectively.


Now I was curious to see if the PMC err shows reasonable improvement when the IMC is locked. Attachment 2 shows the latest comparison of the PMC err with and without the IMC locked. The PMC error has been taken up to 500kHz. The errors were divided by 17.5kHz LPF and 150kHz LPF to compensate the sensing response. The PMC cavity pole was ignored in this calculation. T990025 saids the PMC finesse is 4400 and the cavity pole is 174kHz. If this is true, this also needs to be applied.


1. Now we can see improvement of the PMC error in the region between 10kHz to 70kHz.

2. The sharp peak at 8kHz is due to the marginally stable PMC servo. We should implement another notch there. T990025 suggests that the body resonance of the PMC spacer is somewhere around there. We might be able to damp it by placing a lossy material on it.

3. Similarly, the features at 12kHz and 28kHz is coming from the PMC. They are seen in the OLTF of the PMC loop.

4. The large peak at 36kHz does not change with the IMC state. This does mean that it is coming from the laser itself, or anything high-Q of the PMC. This signal is seen in the IMC error too.

5. 72kHz, 108kHz, 144kHz: Harmonics of 36kHz?

6. Broad feature from 40kHz to 200kHz. The IMC loop is adding the noise. This is the frequency range of the PC drive. Is something in the PC drive noisy???

7. The feature at 130kHz. Unknown. Seems not related to IMC. The laser noise or the PMC noise.

Remaining IMC issues:

Done (Nov 23, 2015) - 29.5MHz oscillator output degraded. Possibly unstable and noisy. Do we have any replacement? Can we take a Marconi back from one of the labs?

Done (Nov 23, 2015) - Too high LO?

- Large 36kHz peak in the IMC

- IMC loop shape optimization

- IMC locking issue. The lock streatch is not long.

- IMC PC drive issue. Could be related to the above issue.

Maybe not relevant - PC drive noise?

Attachment 1: IMC_OLTF.pdf
Attachment 2: PMC_noise_comparison.pdf
  11796   Sun Nov 22 07:09:01 2015 ranaUpdateIOOIMC fix

On the demod board there is a 10 dB attenuator (AT1), which lowers the level to -10 dBm before the ERA-5. Then it should be 10 dBm before going to the rest of the parts. But I guess the ERA-5 chips which come later on in the circuit could be decaying like the ones in the PMC LO board.


Later at home, I thought this nominal LO level of 0dBm could have been wrong.

  11797   Sun Nov 22 12:07:09 2015 KojiUpdateIOOIMC fix


Done (Nov 23, 2015) - Check if the attenuator is still there in the input chain

Done (Nov 23, 2015) - Check if the actual LO levels at the 17dBm mixers are reasonable.

- Check if the actual LO levels for the LSC demods are OK too

  11798   Sun Nov 22 12:12:17 2015 KojiUpdateIOOIMC OLTF

Well. I thought a bit more and now I think it is likely that this is just the servo bump as you can see in the closed-loop TF.


6. Broad feature from 40kHz to 200kHz. The IMC loop is adding the noise. This is the frequency range of the PC drive. Is something in the PC drive noisy???

ELOG V3.1.3-