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ID Date Author Type Categorydown Subject
  4639   Thu May 5 14:40:14 2011 KojiUpdateLSCMI locking : calibration of BS and ITMs actuators

I've got confused

1) Are these the DC responses of the coils? If that is true, we need to specify the resonant frequency of each suspension to get the AC response.

2) Are these the AC responses well above the resonant freqs? In that case, The responses should be x.xxx / f^2 [m/counts]


The open loop transfer functions of the Michelson locking have been measured.

The purpose of this excise is to calibrate the coil-magnet actuators on BS and ITMs.

The estimated actuation coefficients are :

 BS = 3.69e-08 [m/counts]
 ITMX = 8.89e-09 [m/counts]
 ITMY = 9.22e-09 [m/counts]

  4640   Thu May 5 14:50:30 2011 JenneUpdateLSCchans file for LSC


Foton doesn't correctly display the LSC filter bank file : C1LSC.txt.

Foton tells a lie that they all are empty.


The file itself looks fine to me i.e. I can find correct filters in text format.

Looks like someone (maybe Joe and Jenne ?) updated the file. I am not sure if this is the reason or not.

allegra:chans>ls -al | grep LSC
-rw-r--r--  1 controls controls   20659 May  5 11:46 C1LSC.txt



 See my updated elog 4636 for what Joe and I did this morning, and what a possible problem is (making the LSC model into a sub-model).

  4643   Thu May 5 15:28:23 2011 kiwamuUpdateLSCRe: MI locking : calibration of BS and ITMs actuators

They are the DC responses.

I put the resonant frequencies that Leo reported in the wiki to obtain the DC response.

The resonant frequencies I used are :

  f_BS = 0.957 Hz

  f_ITMX = 0.966 Hz

  f_ITMY = 0.988 Hz

Also I assumed that all the Q-values are 5 due to the damping.


I've got confused

1) Are these the DC responses of the coils? If that is true, we need to specify the resonant frequency of each suspension to get the AC response.

2) Are these the AC responses well above the resonant freqs? In that case, The responses should be x.xxx / f^2 [m/counts]


 BS = 3.69e-08 [m/counts]
 ITMX = 8.89e-09 [m/counts]
 ITMY = 9.22e-09 [m/counts]


  4645   Thu May 5 16:11:22 2011 JamieUpdateLSCchans file for LSC


Foton doesn't correctly display the LSC filter bank file : C1LSC.txt.

 This was because of a bug in the RCG for foton filter module naming when top names is being used.  Rebuilding the LSC front-end model with top_names (which was needed to get around another bug in the RCG) broke the filter file.  I manually fixed the file, so it should work now.

  4656   Sat May 7 02:52:53 2011 kiwamuUpdateLSCTRY photo diode installed

[Suresh / Kiwamu]

 We installed the TRY photo diode (Thorlabs one) and the ETMYT CCD camera in place on the ETMY table.

Now we can see a signal on the TRY digital channel.

It will be quite useful for the Y arm locking, for instance we can do a triggered locking and the maximization of the intracavity power.

Someone has to install the EMTY trans QPD at some point.

  4664   Mon May 9 12:33:40 2011 kiwamuUpdateLSCC1:LSC-TRIG_MTRX : wrong matrix size

I found that C1:LSC-TRIG_MTRX has a wrong matrix size. It needs to be fixed.

It is designed to have a 11x8 matrix in the simlink model file, but it's been compiled as a 6x8 matrix.

I recompiled c1lsc but it didn't fix the issue. Here below is the matrix statement in the C file :c1lsc.c. Indeed it is 6x8 matrix ....

// MuxMatrix:  LSC_TRIG_MTRX
  lsc_trig_mtrx[ii] =
          pLocalEpics->lsc.LSC_TRIG_MTRX[ii][0] * lsc_imux_trigger[0] +
          pLocalEpics->lsc.LSC_TRIG_MTRX[ii][1] * lsc_imux_trigger[1] +
          pLocalEpics->lsc.LSC_TRIG_MTRX[ii][2] * lsc_imux_trigger[2] +
          pLocalEpics->lsc.LSC_TRIG_MTRX[ii][3] * lsc_imux_trigger[3] +
          pLocalEpics->lsc.LSC_TRIG_MTRX[ii][4] * lsc_imux_trigger[4] +
          pLocalEpics->lsc.LSC_TRIG_MTRX[ii][5] * lsc_imux_trigger[5];

  4665   Mon May 9 13:14:48 2011 josephbUpdateLSCC1:LSC-TRIG_MTRX : wrong matrix size

[Joe, Kiwamu]

There is a feature/bug of the RCG code that you can only have 1 receiving tag for every sending tag.  There were 5 tags which were being received by two tags each, for two different matrices.  Only the first tag was receiving, the second was apparently ignored.

This has been fixed temporarily by putting in direct lines in place of these 5 tags.


I found that C1:LSC-TRIG_MTRX has a wrong matrix size. It needs to be fixed.

It is designed to have a 11x8 matrix in the simlink model file, but it's been compiled as a 6x8 matrix.


  4671   Mon May 9 18:54:29 2011 kiwamuUpdateLSCtriggerd locking logic : screen prepared

I made a new medm screen for the triggering logics. Have fun.

I put a button on C1LSC.adl to invoke this screen.


Quote from #4656

It will be quite useful for the Y arm locking, for instance we can do a triggered locking and the maximization of the intracavity power.


  4689   Wed May 11 13:54:32 2011 steveUpdateLSCLSC power supplies

Aux- rack _1Y2 is just behind 1Y3  It contains Kepco Analoge DC power supplies for +- 5, 15 and 24V

Placing these power supplies away from the LSC rack was an effort to minimize pick up from them.


  4694   Wed May 11 22:52:55 2011 kiwamuUpdateLSCstatus update and plan

Rana forced me to write this entry for summary because he didn't come to the 40m meeting today.

Status update :

    Interferometer Input Beam alignment with the PZTs.

     60 % done. The rest of the 40 % is to make the procedures automated.

     The beam spots on ITMY and ETMY are centered within ~1 mm accuracy.

     PRM, BS, ITMX, & ITMY actuator calibrations and PRC/MICH error calibrations

    Ongoing: First we will do it by hand, then some scripts will be made for the calibraion and resultant noise budget.

     F2A Suspension filter calculations.

      ETMY and ITMY are done. Need volunteer for ETMX, ITMX, BS, PRM, & SRM !!

      Bounce-Roll notch filters

      Leo is working on it. 25% complete...

     DC signal from RFPDs

      The RFPDs have a local SMA DC output as well as a DC output from their PD Interface cards in the LSC rack. We have hooked up some of the PD Interface DC outputs to the LSC ADCs but not tested??

Next steps:

  Installation of a temporary (Thorlabs) DCPD on either POY to see the intra-cavity power in the PRC. It would be ridiculous to put detectors on POX or POP since they're still clipped.

  D-phase and amplitude imbalance adjustment of the demod baords.

          make a script which uses pynds.

  Alignment of the full interferomter, starting from the X arm

  Loss measurements for the arms

  Schnupp asymmetry measurement


  4710   Fri May 13 01:42:35 2011 kiwamuUpdateLSCready for Schnupp asymmetry measurement

[Valera / Kiwamu]

 We are able to lock each arm smoothly.  It is ready for the Schnupp asymmetry measurement.

( to be done )

 - Manual D-phase adjustment of the AS55 channel.

 - A script to adjust the D-phase.

 - Trigger logic for the boost filters.

 - Modification of some old alignment scripts to adopt them to the new LSC channels

  4717   Sat May 14 14:50:21 2011 KojiUpdateLSC1Y2 5V Blown Fuse found -> Fixed

Incidentally, a blown fuse on 5V line at 1Y2 rack was found during the intallation of Sorensens.
The fuse (5A 125V) has been replaced and fixed.

When I plugged the fuse in, I heard some sound like relays were switched. Are there any relays in the LSC rack?

It was a 9th fuse from the top as seen in the picture.

  4721   Sun May 15 19:10:12 2011 kiwamuUpdateLSCCalibration of actuators : BS, ITMX and ITMY

The AC response of the actuators on BS, ITMX and ITMY were re-measured by another technique.

Last time I estimated them by measuring the open-loop transfer functions, but this time the responses were measured in a more direct way.

The measured AC responses (60 Hz - 200 Hz) are :

      BS   = 1.643e-98 / f2  [m/counts] (corrected based on the plot below - Manasa)

     ITMX = 3.568e-9 / f2 [m/counts]

     ITMY = 3.542e-9 / f2 [m/counts]

Next : measurement of the PRM actuator response

(The technique) 

 This time a technique that Rana told me a week ago was used.

This technique allows us to directly measure the response of an actuator at high frequency without any loop corrections.

First of all, MICH has to be locked to keep MICH within the linear range of the error signal. So now MICH is a linear sensor to the mirror motions.

In the MICH control a steep low pass filter should be inserted in order to avoid unwanted effects from the control loop at the high frequencies.

For example I put a low pass filter composed of an elliptical filter whose cut-off frequency is at 50 Hz such that the control loop doesn't push the mirrors above the cut-off frequency.

Hence the error signal of MICH above 50 Hz directly corresponds to the motion of the mirrors including BS, ITMX and ITMY.

Taking a transfer function from an actuator to the MICH error signal directly gives the actuator response.

In my measurements MICH was locked by feeding the signal back to BS. The plot below is the expected open-loop transfer function for the MICH control.


You can see that the open loop TF suddenly drops above 50 Hz. The UGF was at about 20 Hz, confirmed by looking at the loop oscillation on DTT.



 In the technique the error signal has to be calibrated to [m]. This time AS55_Q was used and calibrated based on a peak-to-peak measurement.

The peak to peak value in the MICH error signal was 8 counts, which corresponds to the sensor efficiency of 4.72e+07 [counts/m].

Then I took transfer functions from each suspension (i.e. C1:SUS-XXX_LSC_EXC) to the error signal at AS55_Q over a frequency range from 60 Hz to 200Hz.

For the transfer function measurements I ran the swept sine on DTT to get the data. Note that the PD whitening filters were on.

The plot below is the results of the measurements together with the fitting lines.


In the fitting I excluded the data pints at 60 Hz, because their coherence was low due to the power line noise.

  4729   Tue May 17 01:05:56 2011 kiwamuUpdateLSCAsymmetry measurement prep : recentering works

I re-centered beams on several PDs and a camera including :



The most important one was AS55.

When I was locking each arm I found that the error signal from AS55 was very coupled to the angular motion of the arms.

I checked the beam on the AS55 RFPD and found the beam on the edge of the photo diode. This is possibly because Valera and I had been touching the input beam alignment.

At that time the DC signal from AS55 without aligning PRM and SRM was about 5 mV.

Adjusting the beam position by a steering mirror brought the DC signal up to 20 mV.

Then the lock of each arm became more stable.

  4735   Tue May 17 22:50:00 2011 JamieConfigurationLSCNew digital lockin added to LSC model/screen

I added a lockin to the LSC model, and added it's corresponding control to the LSC screen.  Here's is what I added to the LSC model:


On the left are the froms from the normalized RF PD outputs. Those go into a matrix, whose single row goes into the lockin signal input. The clock output from the lockin goes into the LSC output matrix (last row).

Here is what I added to the LSC master screen:


I also modified the lockin overview screen:


I think this new screen looks a lot cleaner.  Maybe we could start using this one as a template for lockin screens.

  4743   Wed May 18 22:11:31 2011 ranaConfigurationLSCNew digital lockin added to LSC model/screen


 This is OK....but, the input matrix should come from the same place as the regular input matrix: i.e. it should be just another row like CARM, DARM, etc. rather than have its own screen.

Also, I think a nice mod to all the matrices would be if the ORANGE triangle was only visible when there's a signal flowing through it.

  4749   Thu May 19 16:46:20 2011 kiwamuUpdateLSCc1lsc model : input channels rearanged

According to Suresh's LSC rack design I rearranged the input channels of the c1lsc model such that the analog signals and the ADC channels are nicely matched.

Also I updated the c1lsc model in the svn with a help from Joe. The picture below is a screen shot of the input channels in the model file after I edited it.


  4753   Fri May 20 03:01:17 2011 kiwamuUpdateLSClocking status

(PRMI locking)

Since REFL11 has gone I tried locking the PRMI with combination of REFL55 and AS55.

Without any pain the lock of PRMI was achieved successfully. AS55 was used to sense MICH and REFL55 was used for PRC.



Additionally I was modifying several scripts which are invoked from C1IFO_CONFIGURE.adl. Some details about the scripts will be uploaded on the wiki later.

An important thing is that now we are able to use the "restore" commands for the Y arm, X arm, Michelson and PRM locking.

The scripts will automatically acquire the lock of each DOF.  The image below is just a screen shot of the medm screen where you can call the scripts.



( Still to do)

   * PRM actuator response measurement

   * PRC noise budget

   * MICH-PRC actuator decoupling

  4757   Sat May 21 06:19:46 2011 kiwamuUpdateLSCDRMI trial : no luck

I will try with POY55 that Koji prepared today.

  4759   Mon May 23 00:36:51 2011 kiwamuUpdateLSCDRMI trial : sucess

Eventually the DRMI was locked.

I was struggling to find a good signal port for SRC over the weekend and finally found AS55_I worked somehow. I used :

   REFL11_I --> PRC

   AS55_Q   --> MICH

   AS55_I    --> SRC

A configuration script was prepared such that someone can try this configuration by clicking a button on the C1IFO_CONFIGURE.adl screen.

I don't think this signal extraction scheme is the best, but now we can find better signal ports by shaking each DOF and looking at each signal port.

More details will be reported in the morning.


I will try with POY55 that Koji prepared today.


  4760   Mon May 23 12:27:26 2011 kiwamuUpdateLSCDRMI trial : details

(PRMI locking with slightly misaligned SRM)

 First I tried locking PRC and MICH with a little bit misaligned SRM. This condition allowed me to search for a good signal port for SRC.

In this locking, REFL11_I was used to lock PRC and AS55_Q was used for MICH. This is the same scheme as the current PRMI locking.

Since the alignment of SRM was close to the good alignment, I expected to see fringes from SRC in some signal ports (i.e. REFL55, POY55 and so on).

Sometimes a fringe of SRC disturbed AS55_Q and broke the MICH locking, so I had to carefully misalign SRM so that the SRC fringes are small enough to maintain the lock of MICH.


(Looking for a good signal port for SRC)

 After I locked the PRMI with slightly misaligned SRM, I started looking for a good signal port for SRC.

At the beginning I tried finding a good SRC port by shaking SRM at 100 Hz and looked at the power spectra of all the available LSC signals.

I was expecting to see a 100 Hz peak in the spectra, but this technique didn't work well because SRC wasn't within the linear range and hence didn't produce linear signals.

So I didn't see any strong signals at 100 Hz and finally gave up this technique.

Then I started looking for a PDH-like signal in time series and immediately found AS55_I showed large PDH-like signals.

So I started using the AS55_I for the SRC locking and eventually succeeded.


(Two tips for the DRMI locking)

During the locking of DRMI, I found two tips that made the locking quite smooth.

 - Triggered locking

   Since every LSC signal ports showed large signals from PRC somehow, feeding back the signals made the suspensions crazy.

   So I used triggered locking for the PRC and MICH locking to avoid unwanted kicks on BS and PRM.

   If  the DC of REFL goes above a certain level, the control of  PRC starts. Also if the DC of AS goes below a certain level the control of MICH starts.

  These triggers make the lock smoother.

 - Do not use resonant gain filters

  This is really a stupid tip. When I was trying to lock MICH, the lock became quite difficult for some reasons.

  It looked there was an oscillation at 3 Hz every time the MICH control started. It turned out that a 3 Hz resonant gain filter had been making it difficult.

  All the resonant gain filters should be off when a lock acquisition is taken place.

Quote from #4759

Eventually the DRMI was locked.

More details will be reported in the morning.


  4761   Mon May 23 14:28:23 2011 kiwamuConfigurationLSCPOY55 installed

Last Saturday the POY55 RFPD (see this entry) was installed on the ITMY optical bench for the trial of the DRMI locking.

Since the amount of the light coming into the diode is tiny, the DC monitor showed ~ 3 mV even when the PRC was locked to the carrier.

In order to amplify the tiny RF signal from the photo diode a ZHL amplifier was installed next to the RFPD. The RF amp is sitting on delrin posts for insulation from the table.


  4762   Mon May 23 18:10:41 2011 kiwamuUpdateLSCf2p filters on PRM : not good

During the DRMI trial I noticed that the f2p filters on PRM is not quite effective (i.e. pushing PRM in POS direction makes misalignments).

I checked the f2p filters in an easy way. I pushed POS at 0.01 Hz with an amplitude of 1000 counts and looked at the oplev error signals with / without the f2p filters.

The picture below is a time series of the POS excitation, the oplev's PITCH and YAW error signals.

You can see there still is a big coupling from POS to YAW after the f2p filters were enabled. (Its supposed to be like this)

I will redo the f2p measurement on PRM.


  4763   Mon May 23 18:16:42 2011 KojiConfigurationLSCPOY55 installed

The DC Transimpedance of POP55 was increased from 50 Ohm to 10010 Ohm. There is the offset of 46mV. This should be cancelled in the CDS.


Last Saturday the POY55 RFPD (see this entry) was installed on the ITMY optical bench for the trial of the DRMI locking.

Since the amount of the light coming into the diode is tiny, the DC monitor showed ~ 3 mV even when the PRC was locked to the carrier.

In order to amplify the tiny RF signal from the photo diode a ZHL amplifier was installed next to the RFPD. The RF amp is sitting on delrin posts for insulation from the table.


  4766   Wed May 25 20:12:55 2011 JamieConfigurationLSCNew digital lockin added to LSC model/screen


This is OK....but, the input matrix should come from the same place as the regular input matrix: i.e. it should be just another row like CARM, DARM, etc. rather than have its own screen.

 You're absolutely right.  That was a brain-fart oversight.  I fixed the model so that the input from the lockin comes from another output row in the RFPD input matrix.  I then fixed the C1LSC medm screen accordingly:


This is obviously much simpler and more straight-forward.

A future improvement would be to modify the DCPD input matrix to be able to route those signals to the lockin as well.  This is actually currently possible since the DCPD input matrix is just a subset of the full input matrix, but it's not available via medm yet.

  4767   Thu May 26 17:10:21 2011 JamieConfigurationLSCNew digital lockin added to LSC model/screen


A future improvement would be to modify the DCPD input matrix to be able to route those signals to the lockin as well.  This is actually currently possible since the DCPD input matrix is just a subset of the full input matrix, but it's not available via medm yet.

 I went ahead and added the lockin output to the DCPD input matrix.


  4768   Fri May 27 17:52:53 2011 steveUpdateLSCLSC rack cables strain relieved & labeled

LSC rack 1Y2 cables are strain relieved and labeled. Spare and/or obsolete cables are laid out on the top of the beam tube and on the outside of the rack.

The POY 110 MHZ demodboard has a very touchy position in the VME crate. Watch out for it! It has to be fixed.

  4788   Mon Jun 6 17:22:09 2011 valeraConfigurationLSCClipping in the X arm 1064 um trans path

I changed optics in the ETMX transmon path to remove clipping (which made a false QPD signal).

During the weekend I found that there was an offset in X arm c1ass pitch servo, which derives the signal by demodulating the arm cavity power, coming from the beam clipping in the transmon path.

The clipping was on the pair of the 1" mirrors that steer the beam after the 2" lens (see attached picture). The beam is about 5-6 mm in diameter at this distance from the lens and was not well centered.

I moved the steering mirrors downstream by about 8" where the beam is about 2-3 mm (the attached picture shows the mirrors in the new location). The Y arm layout is different from X arm and I didn't find any obvious clipping in transmon path.

The max X arm buildup went up from 1.3 to 1.5. I changed the TRX gain from -0.003 to -0.002 to obtain the normalized X arm power of 1 in this state. The MC refl DC is 1.6 out of 4.9 V and the Y arm buildup is ~0.9 so the TRX(Y) gains will have to be adjusted once the MC visibility is maximized.

  4797   Wed Jun 8 23:17:25 2011 kiwamuUpdateLSCDRMI output matrix diagonalization

Approximately two weeks ago I diagonalized the LSC output matrix for the DRMI locking.

Since actuation on the position of BS changes not only MICH but also PRC and SRC, we needed to diagonalize the output matrix.


- What I did :

 (1) The DRMI was locked. At this point PRC, MICH and SRC was controlled by PRM, BS and SRC actuators respectively.

 (2) I injected excitation signal on C1:LSC-MICH_EXC by awg. The excitation was at about 200 Hz, which is above the UGF of all the LSC loops.

    At this point the excitation only shakes the position of BS.

 (3) I looked at spectra of REFL11_I, AS55_Q, AS55_I, that were used to sense PRC, MICH and SRC respectively.

   At the beginning I was able to see the peak due to the excitation in those spectra. This means BS shakes the other DOFs (i.e. PRC and SRC) as well as MICH.

 (4) To minimize the coupling from MICH to PRC (or SRC), I tuned a number on an element of the output matrix, which transfers the signal from MICH to PRM (or SRM).

   This business was done by looking at the peak on REFL11_I (or AS55_I) and minimizing it. Since this technique was too naive the tuning was done only in second decimal place.


  4805   Fri Jun 10 14:50:37 2011 KojiUpdateLSCNew LSC code installed

[Koji Jamie]

The new c1lsc code has been installed. The LSC screens have also been updated (except for ASS screen).

The major changes are:

1. Naming of the RFPD channels. Now the PD signals were named like:

REFL11_I_IN1, REFL11_I_IN2, REFL11_I_OUT ....

instead of REFL11I_blah

2. NREFL11, etc has been removed. We now have the official error signals
named like


We can't use the name "REFL11_I" for the error signal as this name is
occupied by the name of the filter module.

  4808   Mon Jun 13 12:34:21 2011 Jamie, KojiUpdateLSCUpdated LSC model installed

After a couple of hickups, I was able to compile and install Koji's rework of the LSC model.

The main changes are that the model now use an RF_PD library part, and the channel names were tweaked to be more in line with what we expect.

I found a couple of small bugs in the model that were preventing it from compiling.  Those were fixed and it compiled with no further problems.

There was also some rearrangement of signal inputs to the PD_DOF matrix.  The matrix screen was updated to reflect the proper inputs.  However, this also meant that the burt restore scripts for the IFO configurations were setting the wrong elements in the matrix.  I fixed the settings for X and Y arm locking, and updated the burt snapshots using the burt/c1ifoconfigure/C1save{X,Y}arm scripts.  NOTE: burt settings will need to be updated for the MICH, PRM, DRM, and FULL IFO configurations as well.

During the build/install process, Joe and I also found a bug in the feCodeGen that was causing the filter screens to be created with the wrong names.  Joe sent out a patch that will hopefully be merged soon.  Building the model with Joe's patch fixed the screen names, so the screens are currently named correctly.

  4818   Tue Jun 14 18:12:34 2011 Jamie, KiwamuUpdateLSCLSC seems to be fully recovered

We are now locking the arms reliably, with reasonable transmitted power.  We zeroed the LSC offsets with script, since they were apparently not being reset with either the overall burt restore or the arm restore scripts.

We have lost a bit of power through the mode cleaner.  However, we have opted not to tweak it up just yet, so that we don't have to realign to the arms.

  4821   Wed Jun 15 01:30:38 2011 JamieSummaryLSCSchnupp asymmetry measurement

Measurement of Schnupp asymmetry

This was done by measuring the relative phase between the sidebands reflected from the two arms while the arm cavities are locked.

The Schnupp asymmetry is measured to be:   Lsa = 3.64 ± 0.32 cm



As a phase reference we use the zero crossing of the response function for the out-of-phase control signal for the single arm cavity lock [0]. The difference in the RD rotation phase of the response zero crossings indicates the phase difference in the sideband signals reflected from the arms. Assuming the asymmetry is less than half the RF modulation wavelength [1], the asymmetry is given by the following formula:

       \Delta \phi   c   1 
L_sa = ----------- ----- -
           360     f_RSB 2

We use a LSC digital lock-in to measure the response of the arm cavity at a single-frequency drive of it's end mirror.

[0] The locations of the zero crossings in the out-of-phase components of the response can be determined to higher precision than the maxima of the in-phase components.

[1] fRSB = 55 MHz,     c/fRSB/2 = 2.725 m


  1. Lock/tune the Y arm only.
    • We use AS55_I to lock the arms.
  2. Engage the LSC lock-in.
  3. Tune the lock-in parameters:
  4. lock-in freq: 103.1313 Hz
    I/Q filters:  0.1 Hz low-pass
    phase:        0 degrees
  5. Set as input to the lock-in the out-of-phase quadrature from the control RFPD.  In this case AS55_Q->LOCKIN.
  6. Drive the arm cavity end mirror by setting the LOCKIN->Y_arm element in the control matrix.
  7. Note the "RD Rotation" phase between the demodulated signals from the control PD (AS55)
  8. For some reasonable distribution of phases around the nominal "RD Rotation" value, measure the amplitude of the lock-in I output.
    • Assuming the Q output is nearly zero, it can be neglected.  In this case the Q amplitude was more than a factor of 10 less than the I amplitude.
    • Here we take 5 measurements, each separated by one over the measurement bandwidth (as determined by the lock-in low pass filter), in this case 10 seconds.  The figure above plots the mean of these measurements, and the error bars indicate the standard deviation.

The data and python data-taking and plotting scripts are attached.

Error Analysis:

To to determine the parameters of the response (which we know to be linear) we use a weighted linear least-squares fit to the data:

y = b X


X0j = 1
X1j = xj              # the measurement points
y = yi                 # the response
b = (b0, b1)     # line parameters

The weighting is given by the inverse of the measurement covariance matrix. Since we assume the measurements are independent, the matrix is diagonal and Wii = 1/\sigmai2 The
estimated parameter values are given by:

\beta  =  ( XT W X )-1 XT W y  =  ( X'T X' )-1 X'T y'

where X' = w X, y' = w y and wii = \sqrt{Wii}.

The X' and y' are calculated from the data and passed into the lstsq routine. The output is \beta.

The error on the parameters is described by the covariance matrix M\beta:

M\beta = ( XT W X)-1 = ( X'T X')-1

with correlation coefficients \rhoij = M\betaij / \sigmai / \sigmaj.

The x-axis crossing is then given by:

X(Y=0) = - \beta1 / \beta0


Valera's LLO measurement

  4834   Fri Jun 17 23:20:05 2011 KojiUpdateLSCSome updates of the LSC screen

Some updates of the LSC screen

- Signal amplitude monitor for the PD signals (--> glows red for more than 1000)

- Kissel Buttons for the main matrices

- Trigger display at the output of the DOF filters

- Signal amplitude monitor for the SUS LSC output (--> glows red for more than 10000)


ADC Over flow monitor is showing some unknown numbers (as ADCs are handled by IOPs).
I asked Joe for the investigation (and consideration for the policies)

  4845   Mon Jun 20 18:36:49 2011 SureshUpdateLSCREFL55 PD update

[Suresh, Koji]

   I used a matlab code written by Koji to analyse the transimpedance and current noise data  of REFL55.  The details are in the attached pdf file.

Resonance is at 55.28 MHz:

Q of 4.5, Transimpedance of 615 Ohms

shot noise intercept current = 1.59 mA

current noise =21 pA/rtHz


Notch at 110.78 MHz:

Q of 54.8 Transimpedance of 14.68 Ohms.











[Rana, Koji]

REFL55 was modified. The noise level confirmed. The PD is now ready to be installed.


Kevin's measurement report told us that something was wrong with REFL55 PD. The transimpedance looked OK, but the noise level was terrible (equivalent to the shotnoise of 14mA DC current).

Rana and I looked at the circuit, and cleaned up the circuit, by removing unnecessary 11MHz notch, 1k shunt resister, and so on.

I made a quick characterization of the PD.

First page:

The transimpedance ws measured as a function of the frequency. The resonance was tuned at 55MHz. The notch was tuned at 110MHz in order to reject the second harmonics. The transimpedance was ~540V/A at 55MHz. (For the calibration, I believed the DC transimpedance of 50V/A and 10000V/A for the DC paths of this PD and #1611, respectively, as well as the RF impedance (700V/A0 of #1611.

Second page:

Output noise levels were measured with various amount of photocurrent using white light from a light bulb. The measurement was perforemed well above the noise level of the measurement instruments.

Third page:

The measured output noise levels were converted into the equivalent current noise on the PD. The dark noise level agrees with the shot noise level of 1.5mA (i.e. 22pA/rtHz). In deed, the noise level went up x~1.5 when the photocurrent is ~1.4mA.


  4850   Tue Jun 21 20:35:50 2011 kiwamuUpdateLSCa script to measure sensing matrix

Last night I was making a script which will measure the sensing matrix using the realtime LOCKIN module.

The script is a kind of expansion of Jamie's one, which measure the asymmetry, to more generic purpose.

It will shake a suspended optic of interest and measure the response of each sensor by observing the demodulated I and Q signals from the LOCKIN module.

I will continue working on this.


  (current status)

 - made a function that drives the LOCKIN oscillator and get the data from the I and Q outputs.

 - checked the function with the MICH configuration.

   ITMX, ITMY and BS were shaken at 100 Hz and at different time.

   Then the response of AS55_Q showed agreement with what I got before for the actuator calibration (see this entry).

   It means the function is working fine.

  4851   Tue Jun 21 23:29:41 2011 kiwamuUpdateLSCsensing matrix measurement

I am now measuring the sensing matrix in the DRMI configuration.

A goal of tonight is to measure the sensing matrix as a test of the script.


The result will be updated later.

  4857   Wed Jun 22 17:42:03 2011 kiwamuUpdateLSCsensing matrix measurement

The sensing matrix was measured in the DRMI configuration for the first time.

The measurement was done by an automatic script and the realtime LOCKIN module built in the c1lsc model.

The resultant matrix is still too primitive, so I will do some further analysis.


(Measurement of sensing matrix)

 The quantities we want to measure are the transfer functions (TFs) from displacement (or change in optical phase) of each DOF to sensors in unit of [counts/m].

So essentially the measurement I did is the same as the usual TF measurement. The difference is that this measurement only takes TFs at a certain frequency, in this case 283 Hz.

 The measurement goes in the following order :

  (1) Lock DRMI

  (2) Shake an optic of interest longitudinally with an amplitude of 1000 counts at 283.103 Hz, where no prominent noise structures are present in any spectra of the sensor signals.

  (3) Put a notch filter at the same frequency of 283.103 Hz in each DOF (MICH, PRC and SRC) to avoid unwanted suppression due to the control loops.

       (This technique is essentially the same as this one, but this time the control loops are shut off only at a specific frequency )

       The notch filter I put has a depth of 60 dB and Q of 20. The filter eats the phase of ~10 deg at 200 Hz, which still allow servos to run with a high UGF up to 200Hz.

  (4) Take the output signal from a signal port of interest (i.e. REFL11_I, etc.,) and then put it into the realtime LOCKIN module.

  (5) Measure the resultant I and Q signals coming out from the LOCKIN module.

  (6) Repeat the procedure from (2) through (5) for each optic and sensor.



 Again, the resultant sensing matrix is still primitive, for example the optic-basis should be converted into the DOF basis.

The values listed in the matrix below is the absolute values obtained by operation of sqrt( I^2 + Q^2) plus the polarity according to the output from I and Q of LOCKIN.

Therefore they still contain the actuator response, which is not desired. i will calibrate them into [counts/m] later by using the calibration factor of the actuator responses.

All the raw data showed the relative phase between I and Q either ~ 127 deg or ~ -53 deg.

In my definition, the one has 127 deg is plus polarity and the one has -53 deg is minus polarity.

Technically speaking the polarity depends on the polarity of the actuator and also the direction of the actuator against the DOFs.

Without any excitation the absolute values fluctuated at about 10-4 - 10-5, so the excitation amplitude was big enough to observe the sensing matrix.

Though, I still need to estimate the statistical errors to make sure the SNR is reasonably big.



  Fig.1 Measured sensing matrix from optic to sensors.


(Things to be done)

  - convert the optic-basis (i.e. BS, ITMs, PRM and SRM) to the DOF-basis (i.e. MICH, PRC and SRC) so that the matrix is understandable from point of view of the interferometer control.

  - estimate the optimum demodulation phase for each DOF at each sensor port.

  - add some statistical flavors (e.g. error estimations and so on.)

  - edit the script such that it will keep watching the ADC overflows and the coherence to make sure the measurement goes well.

  - add some more signal ports (e.g. REFL55, POY55 and etc.)

  - compare with an Optickle model

Quote from #4851

The result will be updated later.


  4863   Thu Jun 23 05:22:51 2011 kiwamuUpdateLSCPRMI locking : not stable enough

I was trying to measure the sensing matrix in the PRMI configuration, but basically gave up.

It is mainly because the lock of PRMI wasn't so stable and it didn't stay locked for more than a minute.

It looked like an angular motion fluctuated a lot around 1- 3 Hz. The beam spot on the AS camera moved a lot during the lock.

I have to figure out who is the bad suspension and why.

  4864   Thu Jun 23 09:46:16 2011 ranaUpdateLSCPRMI locking : not stable enough

All the suspensions are bad until you fix them. But, ... there is a script which can be used to diagnose them today:

Python SUStest

  4884   Sat Jun 25 06:09:38 2011 kiwamuUpdateLSCFriday locking

I was able to measure the sensing matrix in the PRMI configuration.

The results will be posted later.

  4899   Tue Jun 28 15:20:08 2011 kiwamuUpdateLSCsensing matrix measurement in PRMI configuration

Here is the result of the measurement of the sensing matrix in the PRMI configuration.

If we believe the resultant matrix, it is somewhat different from what we expected from a finesse simulation (summary of simulated sensing matrix).



As a part of the DRMI test plan, we wanted to check the sensing matrices and consequently diagonalize the LSC input matrix.

The matrix of the DRMI configuration has been measured (#4857), but it was a bit too complicated as a start point.

So first in order to make sure we are doing a right measurement, we moved onto a simpler configuration, that is PRMI.



The technique I used was the same as before (#4857) except for the fact that SRM wasn't included this time.

   - PRC was locked to the carrier resonant point. The UGF of MICH and PRC were ~ 110 Hz and 200 Hz respectively.

   - Longitudinally shook BS, ITMs and PRM at 283.103 Hz with an amplitude of 1000 counts using the LOCKIN oscillator in C1LSC.

   - Took the I and Q phase signals from the LOCKIN outputs.

The table below is the raw data obtained from this measurement :



(Conversion of matrix)

 With the matrix shown above, we should be able to obtain the sensing matrix which gives the relation between displacements in each DOF to each signal port.

The measured matrix connects two vectors, that is,

       (signal port vector) = [Measured raw matrix] (SUS actuation vector),   -- eq.(1)


       (signal port vector) = (AS55_I, AS55_Q, REFL11_I, REFL11_Q)T   in unit of [counts],

    (SUS actuation vector) = (BS, ITMX, ITMY, PRM)T   in units of [counts].

Now we break the SUS actuation vector into two components,

       (SUS actuation vector [counts])  = (actuator response matrix [m/counts])-1 * (MICH, PRM [m] )^T   -- eq.(2)


       (actuator response matrix) =  2.05x10-13 * ( [1   ,  0.217, -0.216,   0  ],

                                                 [ 0.5,  0.109 -0.108, 0.862]  )  in unit of [m/counts]

These values are coming from the actuator calibration measurement.

In the bracket all the values are normalized such that BS has a response of 1 for MICH actuation.

Combining eq.(1) and (2) gives,

     (signal port vector) = (measured raw matrix) * (actuator response matrix)-1 * (MICH, PRM)T

And now we define the sensing matrix by

     (sensing matrix) = (measured raw matrix) * (actuator response matrix)-1

The sensing matrix must be 4x2 matrix.

For convenience I then converted the I and Q signals of each port into the absolute value and phase.

       ABS = sqrt((AAA_I)2 +(AAA_Q)2 ),

       PHASE = atan (AAA_Q / AAA_I),

where AAA is either AS55 or REFL11.


(Resultant matrix)

The table below is the resultant sensing matrix.

ABS represents the strength of the signals in unit of [cnts/m], and PHASE represents the demodulation phases in [deg].


There are several things which I noticed :

   - The demodulation phase of MICH=>AS55 and PRC=>REFL11 are close to 0 or 180 deg as we expected.

      This is a good sign that the measurement is not something crazy.

   - AS55 contains a big contribution from PRC with a separation angle of 152 deg in the demodulation phase.

     In AS55 the signal levels of MICH and PRC were the same order of magnitude but PRC is bigger by a factor of ~4.

     However the finesse simulation (see wiki page) shows a different separation angle of 57 deg and MICH is bigger by factor of ~6.

  - REFL11 is dominated by PRC. The PRC signal is bigger than MICH by a factor of ~100, which agrees with the finesse simulation.

    However the separation angle between PRC and MICH are different. The measurement said only 19 deg, but the simulation said ~ 90 deg.

  - Woops, I forgot to calibrate the outputs from the LOCKIN module.

    The whole values must be off by a certain factor due to the lack of the calibration , but fortunately it doesn't change the demodulation phases.

Quote from #4884

I was able to measure the sensing matrix in the PRMI configuration.

The results will be posted later.


  4905   Wed Jun 29 00:35:36 2011 KojiUpdateLSCnew LSC overview screen 80% done

New LSC screen is 80% completed.

It is now accessible from the LSC menu of "sitemap".

Most of the part in the screen is clickable such that it launches another screen depending on the location of the click.


The bottom part of the screen still need some work.

RFPD screen is temporary

LSC control screen is also temporary

DAC overflow indicators are still broken.

Channel assignment of the whitening filters are arbitrary so far.


  4910   Wed Jun 29 12:20:53 2011 kiwamuUpdateLSCsensing matrix measurement in PRMI configuration

Of course I made a mistake in my calculation of the sensing matrix. I will figure out which point I mistook.

The MICH signal must have the demodulation phase of around 90 deg in AS55

because we had adjusted the demodulation phase such that the MICH signal mostly appears on AS55_Q.


Here is the result of the measurement of the sensing matrix in the PRMI configuration.


  4912   Wed Jun 29 14:43:12 2011 KojiUpdateLSCLSC model updated

LSC model has been updated and running,

- Now the power and signal recycling cavity lengths are named "PRCL" and "SRCL" in stead of three letter names without "L".

- Names for the trigger monitor were fixed. They are now "C1:LSC-DARM_TRIG_MON", etc., instead of "...NORM"

- Channel order of the DC signals for PDDC_MTRX and TRIG_MTRX were changed.

It was "TRX, TRY, REFL, AS, POP, POX, POY" but now "AS, REFL, POP, POX, POY, TRX, TRY".

We should change the locking script to accomodate these changes.

  4915   Thu Jun 30 00:58:19 2011 KojiSummaryLSCLSC whitening filter test

[Jenne, Koji]

We have tested the LSC whitening filters. In summary, they show the transfer functions mostly as expected (15Hz zerox2, 150Hz pole x2).
Only CH26 (related to the slow channel "C1:LSC-PD9_I2_WhiteGain. VAL NMS", which has PD10I label in MEDM) showed different
phase response. Could it be an anti aliasing filter bypassed???

The 32 transfer functions obtained will be fit and summarized by the ZPK parameters.


The CDS system was used in order to get the transfer functions
- For this purpose, three filter modules ("LSC-XXX_I", "LSC-XXX_Q", "LSC-XXX_DC") were added to c1lsc
in order to allow us to access to the unused ADC channels. Those filter modules have terminated outputs.
The model was built and installed. FB was restarted in order to accomodate the new channels.

- Borrow a channel from ETMY UL coil output mon. Drag the cable from the ETMY rack to the LSC analog rack.
- Use 7 BNC Ts to split the signal in to 8 SMA cables.
- Put those 8 signals into each whitening filter module.

- The excitation signal was injected to C1:SUS-ETMY_ULCOIL_EXC by AWGGUI.
- The transfer functions were measured by DTT.
- The excitation signal was filtered by the filter zpk([150;150],[15;15],1,"n")
   so that the whitened output get flat so as to ensure the S/N of the measurement.

- For the switching, we have connected the CONTEC Binary Output Test board to the BIO adapter module
   in stead of the flat cable from the BIO card. This allow us to switch the individual channels manually.

- The whitening filters of 7 channels were turned on, while the last one is left turned off.
- We believe that the transfer functions are flat and equivalent if the filters are turned off.
- Use the "off" channel as the reference and measure the transfer functions of the other channels.
- This removes the effect of the anti imaging filter at ETMY.

- Once the measurement of the 7 channels are done, switch the role of the channels and take the transfer function for the remaining one channel.


- We found the following channel assignment

  • The ADC channels and the PDs. This was known and just a confirmation. 
  • The ADC channels and the WF filter on MEDM (and name of the slow channel)

- We found that the binary IO cable at the back of the whitening filter module for ADC CH00-CH07 were not connected properly.
This was because the pins of the backplane connector were bent. We fixed the pins and the connector has been properly inserted.

- CH26 (related to the slow channel "C1:LSC-PD9_I2_WhiteGain. VAL NMS", which has PD10I label in MEDM) showed different
phase response from the others although the amplitude response is identical.

Summary of the channel assignment (THEY ARE OBSOLETE - SEPT 20, 2011)

ADC                    Whitening Filter
CH  PD                 name in medm   related slow channel name for gain
00  POY11I             PD1I           C1:LSC-ASPD1_I_WhiteGain. VAL NMS
01  POY11Q             PD1Q          
02  POX11I             PD2I           C1:LSC-SPD1_I_WhiteGain. VAL NMS
03  POX11Q             PD2Q           C1:LSC-SPD1_Q_WhiteGain. VAL NMS
04  REFL11I            PD3I           C1:LSC-POB1_I_WhiteGain. VAL NMS
05  REFL11Q            PD3Q           C1:LSC-POB1_Q_WhiteGain. VAL NMS
06  AS11I              PD4I           C1:LSC-ASPD2_I_WhiteGain. VAL NMS
07  AS11Q              PD4Q           C1:LSC-ASPD2_Q_WhiteGain. VAL NMS
08  AS55I              AS55_I         C1:LSC-ASPD1DC_WhiteGain. VAL NMS
09  AS55Q              AS55_Q         C1:LSC-SPD1DC_WhiteGain. VAL NMS
10  REFL55I            PD3_DC         C1:LSC-POB1DC_WhiteGain. VAL NMS
11  REFL55Q            PD4_DC         C1:LSC-PD4DC_WhiteGain. VAL NMS
12  POP55I             PD5_DC         C1:LSC-PD5DC_WhiteGain. VAL NMS
13  POP55Q             PD7_DC         C1:LSC-PD7DC_WhiteGain. VAL NMS
14  REFL165I           PD9_DC         C1:LSC-PD9DC_WhiteGain. VAL NMS
15  REFL165Q           PD11_DC        C1:LSC-PD11DC_WhiteGain. VAL NMS
16  NC (named XXX_I)   PD5I           C1:LSC-SPD2_I_WhiteGain. VAL NMS
17  NC (named XXX_Q)   PD5Q           C1:LSC-SPD2_Q_WhiteGain. VAL NMS
18  AS165I             PD6I           C1:LSC-SPD3_I_WhiteGain. VAL NMS
19  AS165Q             PD6Q           C1:LSC-SPD3_Q_WhiteGain. VAL NMS
20  REFL33I            PD7I           C1:LSC-POB2_I_WhiteGain. VAL NMS
21  REFL33Q            PD7Q
           C1:LSC-POB2_Q_WhiteGain. VAL NMS
22  POP22I             PD8I
           C1:LSC-ASPD3_I_WhiteGain. VAL NMS
23  POP22Q             PD8Q
           C1:LSC-ASPD3_Q_WhiteGain. VAL NMS
24  POP110I            PD9I
           C1:LSC-PD9_I1_WhiteGain. VAL NMS
25  POP110Q            PD9Q
           C1:LSC-PD9_Q1_WhiteGain. VAL NMS
26  NC (named XXX_DC)  PD10I
          C1:LSC-PD9_I2_WhiteGain. VAL NMS
27  POPDC              PD10Q
          C1:LSC-PD9_Q2_WhiteGain. VAL NMS
28  POYDC              PD11I
          C1:LSC-PD11_I_WhiteGain. VAL NMS
29  POXDC              PD11Q
          C1:LSC-PD11_Q_WhiteGain. VAL NMS
30  REFLDC             PD12I
          C1:LSC-PD12_I_WhiteGain. VAL NMS
31  ASDC               ASDC
           C1:LSC-PD12_Q_WhiteGain. VAL NMS

  4949   Wed Jul 6 23:03:57 2011 kiwamuUpdateLSCmodified locking scripts

[Jenne / Kiwamu]

 Last night we modified the locking scripts, that were called from C1IFO_CONFIGURE.adl, to adapt them to the new "PRCL" and "SRCL" convention.

So far they work fine and quitted dumping some error messages about inexistence of these channel names.

  P.S. The locking scripts have been summarized on the 40m wiki

Quote from #4912

- Now the power and signal recycling cavity lengths are named "PRCL" and "SRCL" in stead of three letter names without "L".

We should change the locking script to accomodate these changes.

  4951   Thu Jul 7 02:23:59 2011 JenneSummaryLSCLSC Whitening Filters have been fit

I have fit all of the LSC whitening filters using vectfit4.m

All the data is in my folder ..../users/jenne/LSC_WhiteningTest_29June2011/

The zpk info is saved with each plot of the fit.  The pdfs are kind of huge to stitch together (or rather my computer doesn't want to do it), so I'll just post a representative one for now.


During the daytime either tomorrow or Friday I'll adjust the actual dewhitening filters to match the measured zpk values.

  4955   Thu Jul 7 15:34:44 2011 JenneSummaryLSCLSC Whitening Filters have been fit


During the daytime either tomorrow or Friday I'll adjust the actual dewhitening filters to match the measured zpk values.

 I made a handy-dandy table showing the zpk values for each whitening filter in the wiki: New whitening filter page

Next on the whitening filter to-do list: actually put these values into the dewhitening filters in foton.

  4962   Tue Jul 12 11:52:54 2011 Jamie, SureshUpdateLSCLSC model updates

The LSC model has been updated:

Binary outputs to control whitening filter switching

We now take the filter state bit from the first filter bank in all RF PD I/Q filter banks (AS55_I, REFL11_Q, etc) as the controls for the binary analog whitening switching on the RF PD I/Q inputs. The RF_PD part was also modified to output this control bit. The bits from the individual PDs are then combined into the various words that are written to the Contec BO part.

Channel mapping updated/fixed to reflect wiring specification

Yesterday Suresh posted an updated LSC wiring diagram, with correct channel assignments for the RF PD I/Q and DC inputs.  Upon inspection of the physical hardware we found that some of LSC the wiring was incorrect, with I/Q channels swapped, and some of the PDs in the wrong channels.  We went through and fixed the physical wiring to reflect the diagram.  This almost certainly will affect the EPICS settings for some of the input channels, such as offsets and RD rotations.  We should therefore go through all of the RF inputs and make sure everything is kosher.

I also fixed all of the wiring in the LSC model to also reflect the diagram.

Once this was all done, I rebuilt and restarted the LSC model, and confirmed that the anti-whitening filter banks in the PD input filter modules were indeed switching the correct bits.  I'll next put together a script to confirm that the LSC PD whitening is switching as it should.


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