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ID Date Authorup Type Category Subject
  4685   Wed May 11 10:49:16 2011 valeraConfigurationElectronicsMC3 LL PD has no signal

Yesterday we found that MC3 OSEM LL PD did not have a sensible signal - the readback was close to zero and it was making MC move around. I disabled the PD LL so that the damping is done with just three face plus side PDs. There still no signal from MC3 LL PD today. It needs debugging.

  4696   Wed May 11 23:02:52 2011 valeraUpdateASSDither angular stabilizitaion system update

This is what was done in past two days:

- The ETMY and ITMY pitch and yaw dofs are modulated at 40, 44, 42, 46 Hz respectively (oscillator A=30). The c1ass lockin numbers are 12, 14, 27, 29.

- The NAS55I signal is demodulated at the above frequencies. The demodulated I/Q signal phase is set to shift all signal into I-phase. The lockin inputs are bandpassed around respective frequency f with butter("Bandpass",2,f-0.5,f+0.5). The demod signals are then additionally low passed with butter ("Lowpass",4,0.5) so the servo ugf has to be below 0.5 Hz. The servo filter is p:z 0.0001:0.1.

- The ETMY demodulated signal is fed back to ITMY and visa versa.

- With the above 2x2 servo running we moved the input beam PZTs by hand to follow the cavity.

- At the end we offloaded the servo control signals to the SUS biases again by hand.

- The beam spot centering was estimated by unbalancing the ETMY/ITMY pitch/yaw coil combinations intentionally by 5%, which produces 1.3 mm shift of the node, and comparing the response to the residual signals.

- The dof set up currently is: ETMY pitch lockin 12 -> dof2, ITMY pitch lockin 14 -> dof4, ETMY yaw lockin 27 -> dof7, ITMY yaw lockin 29 -> dof9

- The next step is to demodulate the TRY(X) and servo the input beam PZTs

  4709   Fri May 13 00:39:53 2011 valeraUpdateASSc1ass update

Here the status of the dither alignment or c1ass:

- Both pitch and yaw centering on ETMY/ITMY were closed simultatenously with ugf of ~1/30 Hz.

- I made a medm screen with beam positions as measured by the dither system.The snapshot is attached. There are visual perimeter alarms (red box around the display) to warn about arm power being low or the dither lines not being on. The screen has a pull down menu with 4 scripts:

. assUp - sets up the gains, phases and matricies for the dither system (both the spot centering and the input beam alignment)

. assOn - turns on the dithers and servo - just the Y-arm centering part at the moment

. assOff - turns off the servo and dither lines

. assDitherOn - turns on the dither lines but does not turn on the servo

- All scripts are in scripts/ASS and the medm screen is in medm/c1ass/master/

 

Still to do:

- Commission the input beam and X-arm servos

- Make scripts for X-arm

Attachment 1: c1assqpds.jpg
c1assqpds.jpg
  4769   Mon May 30 23:14:27 2011 valeraUpdateASCY arm initial alignment

I closed all 8 dither loops for the Y arm initial alignment: 2x2 centering servo (this worked before) and 2x2 input beam servo for both pitch and yaw.

So far it looks pretty good - the error points go to zero and the arm power goes up to 1.

The offloading to the alignment biases and the PZTs is not yet automated.

Today the PMC, MC, and Y arm were very cooperative and a pleasure to work with.

  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.

Attachment 1: XarmTransMon.pdf
XarmTransMon.pdf
  4795   Wed Jun 8 16:41:48 2011 valeraUpdateASSX and Y arm dither alignment status

 The current status of the dither alignment system:

- Both Xarm and Yarm alignment are working. The scripts are: scripts/autoDither/alignX(Y). Each script sets up the respective arm, turns on the dither lines and servos for 66 sec, offloads the control signals to TM alignment biases and PZT sliders in case of  Yarm, and to TM and BS alignment biases in case of Xarm, and finally turns off and clears the servo filters and turns off the dither lines.

- Jammie witnessed the final tests of both scripts - both X and Y arm power went up from 0.6-0.7 to close to 1 and the AS beam became symmetric. Also Jammie wanted me to leave the ETMY oplev in its current non-nominal but more stable state i.e. the oplev signals go to the ADC from the D010033 card not the D020432 one. The scripts can now run from the CONFIGURE medm screen.

- Both arms use signals derived from modulating ITM and ETM in pitch and yaw dofs and demodulating the arm power (TRX or TRY) and the cavity length signal (AS55I). The Yarm actuation has 8 dofs - pitch and yaw of the ITM, ETM, and two input beam PZTs so all the sensed dofs are controlled. The Xarm actuation has only 6 dofs - pitch and yaw of the ITM, ETM, and BS. The Xarm servo is set up to servo the beam position on the ETMX and the relative alignment of the cavity and the input beam. The ITMX spot position is unconstrained and provides the null test. The residual displacement on the ITMX is 0.2-0.3 mm in yaw and 0.9-1.0 mm in pitch. The I phases of the beam centering lockins, which are also the error points of corresponding DOF filters, are calibrated in mm by unbalancing the TM coils by known amount. The attached snap shot of the medm screen now has both X and Y arm calibrated beam spot positions and uncalibrated input beam indicators. The input beam angle and position signals can/should be calibrated by tapping the signals digitally and applying the proper matrix transformation - this will require the model change.

- Currently there is no lock loss catching in the model. We should add a trigger on arm power (or an equivalent mechanism) to turn off the inputs to prevent the spurious inputs.

Attachment 1: BeamPositionIndicators.png
BeamPositionIndicators.png
  3897   Thu Nov 11 15:27:43 2010 valera, steveConfiguration ISS AOM installed

 We installed the ISS AOM in the PSL. The AOM was placed right after the EOM. The beam diameter is ~600 um at the AOM. The AOM aperture is 3 mm.

We monitored the beam size by scanning the leakage beam through the turning mirror after the AOM. The beam diameter changed from 525 um to 515 um at a fixed point. We decided that the AOM thermal lensing is not large enough to require a  new scan of the mode going into the PMC and we can proceed with PMC mode matching using the scan that was taken without the AOM (to be posted).

  5010   Thu Jul 21 09:04:59 2011 valera, steveUpdateSUSoplev gains were not optimized

 

Hi Steve,

 
I did change the ETMY optical lever configuration: http://131.215.115.52:8080/40m/4795
And I left it in that state per Jamie's request.
 
I was going to work on the servo tuning but found that the whitening was not working at that time.
What I was going to do is to measure the open loop gain to make sure the servo is stable, then 
measure the noise and minimize the rms motion by tuning the gain and the filter transfer function.
 
I plan to come to the 40m lab on August 22 for two weeks.
 
Valera.
  12169   Fri Jun 10 18:16:59 2016 varunUpdatePSLRealignment of pre mode cleaner

The mode cleaner was misaligned probably due to the earthquake (the drop in the MC transmitted value slightly after utc 7:38:52 as seen in the second plot). The plots show PMC transmitted and MC sum signals from 10th june 07:10:08 UTC over a duration of 17 hrs. The PMC was realigned at about 4-4:15 pm today by rana. This can be seen in the first plot.

Attachment 1: pmctrans_mcsum_signals.png
pmctrans_mcsum_signals.png
  12173   Mon Jun 13 20:01:30 2016 varunUpdateCDSDAFI GUI update

Summary: I am implementing digital audio filtering on various interferometer signals in order to listen to the processed audio which will help in characterizing and noise reduction in the interferometer. following is a summary of the gui i have made towards a general purpose DAF module linked to the LSC. 

Details:  attachment 1 shows the top level overview of the daf module.

The "INPUTS" button shown redirects to the medm screen shown in attachment 2, which is a collection of inputs going into the module.

Each of the buttons shown in "C1DAFI_INPUTS.png" is further linked to various i/o boxes like adc1, adc2, lsc signal and exitation. An example is shown in attachment 3. This is the specific I/O box for the LSC signal.

The field labelled "INPUT_MTRX" is linked to a matrix which routes these 4 inputs to various DSP blocks. Similarly, the "OUTPUT_MTRX" tab is useful for choosing which output goes to the speaker. 

Time and computational load monitoring is done in the "GDS_TP" tab which links to the medm screen shown in attachment 4.

Currently the AGC is successfully implemented as one of the DSP block. The details of the AGC implementation were given in a previous elog: https://nodus.ligo.caltech.edu:8081/40m/12159

I need to make a few changes to the code for Frequency Shifting and Whitening before uploading them on the FE. I will put the details soon.

Some more things that I think need to be added: 

1) "Enable" buttons for each of the DSP blocks.

2) Labels for each of the matrix elements.

3) Further headers and other description for each of the tabs 

Attachment 1: C1DAF_OVERVIEW.png
C1DAF_OVERVIEW.png
Attachment 2: C1DAF_INPUTS.png
C1DAF_INPUTS.png
Attachment 3: C1DAF_LSC.png
C1DAF_LSC.png
Attachment 4: MONITOR.png
MONITOR.png
  12180   Tue Jun 14 20:10:19 2016 varunUpdateCDSDAFI GUI update

I have added Enable buttons for each of the DSP blocks, and labels for the matrix elements. The input matrix takes inputs from each of the 4 channels: ADC1, ADC2, LSC and EXC, and routes them to the audio processing blocks (attachment 2). The output matrix (attachment 3) takes the outputs of the various DSP blocks and routes them to the output and then to the speakers. 

Attachment 1: C1DAF_OVERVIEW.png
C1DAF_OVERVIEW.png
Attachment 2: input_matrix.png
input_matrix.png
Attachment 3: output_matrix.png
output_matrix.png
  12185   Wed Jun 15 22:12:55 2016 varunUpdateCDSDAFI update: stereo output

I wish to have stereo audio output for the DAF module. Hence, there needs to be a second output from the DAF. I added this second output to the model. Following are the details:

FiBox: It consists of two analog inputs which are digitized and multiplexed and transmitted optically. (only 1 fiber is needed due to multiplexing). Attachment 1 shows the fibox with its 2 analog inputs (one of which, is connected), and 1 fiber output. The output of the DAF goes to the FiBox. Until today, the Fibox recieved only 1 analog input. This analog signal comes from the DAC-8 (count starting from 0), which is located at "CH 1 OUT" SMA output in the "MONITORS" bin on the racks (attachment 2).

I have added another output channel to the DAF model both in software and in hardware. The DAF now also uses DAC-9 analog output which goes to the second analog input of the FiBox. The DAC-9 output is located at "CH 2 OUT" SMA output in the "MONITORS" bin on the racks (attachment 4).

After making the changes, the Fibox is shown in attacment 3.

Testing: The LSC input on passing through the DAF block is given through two different DAC outputs, to the same Fibox channel (one after the other), and the output is heard. More concrete testing will be done tomorrow. It will be as follows:

1) Currently, I need to search for a suitable cable that would connect the second channel of the output fibox to the audio mixer. After doing this, end to end testing of both channels will be done.

2) I could not access the AWG, probably because the DAQ was offline today afternoon. Using a signal from the AWG will give a more concrete testing of the stereo output.

3) After this, I will separate the two channels of the stereo completely (currectly they are seperated only at the DAF output stage)

4) I also will edit the medm gui appropriately.

 

Quote:

I have added Enable buttons for each of the DSP blocks, and labels for the matrix elements. The input matrix takes inputs from each of the 4 channels: ADC1, ADC2, LSC and EXC, and routes them to the audio processing blocks (attachment 2). The output matrix (attachment 3) takes the outputs of the various DSP blocks and routes them to the output and then to the speakers. 

 

Attachment 1: IMG_20160615_145535907.jpg
IMG_20160615_145535907.jpg
Attachment 2: IMG_20160615_145413005_HDR.jpg
IMG_20160615_145413005_HDR.jpg
Attachment 3: IMG_20160616_101229499.jpg
IMG_20160616_101229499.jpg
Attachment 4: IMG_20160616_101157096.jpg
IMG_20160616_101157096.jpg
  12207   Tue Jun 21 11:26:42 2016 varunFrogsCDSmedm command not working

"medm: command not found" error when run through command line both in pianosa and rossa in both editing and execution modes. It however gets executed and edited through the sitemap button. Don't know the source of the problem. Gautam did check the .bashrc file. aliases for SITEMAP and m40m are intact in the .bashrc file.

  12211   Wed Jun 22 10:15:45 2016 varunUpdateCDSDAFI update: stereo output

I have updated the DAFI with the following changes:

1) Separated both the channels of stereo output completely, as well as in the GUI.

2) Added text monitors for the inputs and outputs.

The stereo output is now ready except for a cable going from the second channel of the output fibox to the audio mixer.

Attached is the main DAF_OVERVIEW screen and its link button from the LSC screen labelled "DAFI"

Quote:

I wish to have stereo audio output for the DAF module. Hence, there needs to be a second output from the DAF. I added this second output to the model. Following are the details:

FiBox: It consists of two analog inputs which are digitized and multiplexed and transmitted optically. (only 1 fiber is needed due to multiplexing). Attachment 1 shows the fibox with its 2 analog inputs (one of which, is connected), and 1 fiber output. The output of the DAF goes to the FiBox. Until today, the Fibox recieved only 1 analog input. This analog signal comes from the DAC-8 (count starting from 0), which is located at "CH 1 OUT" SMA output in the "MONITORS" bin on the racks (attachment 2).

I have added another output channel to the DAF model both in software and in hardware. The DAF now also uses DAC-9 analog output which goes to the second analog input of the FiBox. The DAC-9 output is located at "CH 2 OUT" SMA output in the "MONITORS" bin on the racks (attachment 4).

After making the changes, the Fibox is shown in attacment 3.

Testing: The LSC input on passing through the DAF block is given through two different DAC outputs, to the same Fibox channel (one after the other), and the output is heard. More concrete testing will be done tomorrow. It will be as follows:

1) Currently, I need to search for a suitable cable that would connect the second channel of the output fibox to the audio mixer. After doing this, end to end testing of both channels will be done.

2) I could not access the AWG, probably because the DAQ was offline today afternoon. Using a signal from the AWG will give a more concrete testing of the stereo output.

3) After this, I will separate the two channels of the stereo completely (currectly they are seperated only at the DAF output stage)

4) I also will edit the medm gui appropriately.

 

Quote:

I have added Enable buttons for each of the DSP blocks, and labels for the matrix elements. The input matrix takes inputs from each of the 4 channels: ADC1, ADC2, LSC and EXC, and routes them to the audio processing blocks (attachment 2). The output matrix (attachment 3) takes the outputs of the various DSP blocks and routes them to the output and then to the speakers. 

 

 

Attachment 1: C1DAF_OVERVIEW.png
C1DAF_OVERVIEW.png
Attachment 2: DAF_link_from_LSC.png
DAF_link_from_LSC.png
  12215   Mon Jun 27 15:12:09 2016 varunUpdateCDSDAFI update: stereo output

Using an RC to BNC connector from the inner drawer, I have added a second output cable going from the output Fibox in the control room to the audio mixer.

Quote:

I have updated the DAFI with the following changes:

1) Separated both the channels of stereo output completely, as well as in the GUI.

2) Added text monitors for the inputs and outputs.

The stereo output is now ready except for a cable going from the second channel of the output fibox to the audio mixer.

Attached is the main DAF_OVERVIEW screen and its link button from the LSC screen labelled "DAFI"

Quote:

I wish to have stereo audio output for the DAF module. Hence, there needs to be a second output from the DAF. I added this second output to the model. Following are the details:

FiBox: It consists of two analog inputs which are digitized and multiplexed and transmitted optically. (only 1 fiber is needed due to multiplexing). Attachment 1 shows the fibox with its 2 analog inputs (one of which, is connected), and 1 fiber output. The output of the DAF goes to the FiBox. Until today, the Fibox recieved only 1 analog input. This analog signal comes from the DAC-8 (count starting from 0), which is located at "CH 1 OUT" SMA output in the "MONITORS" bin on the racks (attachment 2).

I have added another output channel to the DAF model both in software and in hardware. The DAF now also uses DAC-9 analog output which goes to the second analog input of the FiBox. The DAC-9 output is located at "CH 2 OUT" SMA output in the "MONITORS" bin on the racks (attachment 4).

After making the changes, the Fibox is shown in attacment 3.

Testing: The LSC input on passing through the DAF block is given through two different DAC outputs, to the same Fibox channel (one after the other), and the output is heard. More concrete testing will be done tomorrow. It will be as follows:

1) Currently, I need to search for a suitable cable that would connect the second channel of the output fibox to the audio mixer. After doing this, end to end testing of both channels will be done.

2) I could not access the AWG, probably because the DAQ was offline today afternoon. Using a signal from the AWG will give a more concrete testing of the stereo output.

3) After this, I will separate the two channels of the stereo completely (currectly they are seperated only at the DAF output stage)

4) I also will edit the medm gui appropriately.

 

Quote:

I have added Enable buttons for each of the DSP blocks, and labels for the matrix elements. The input matrix takes inputs from each of the 4 channels: ADC1, ADC2, LSC and EXC, and routes them to the audio processing blocks (attachment 2). The output matrix (attachment 3) takes the outputs of the various DSP blocks and routes them to the output and then to the speakers. 

 

 

 

Attachment 1: IMG_20160627_151753247.jpg
IMG_20160627_151753247.jpg
  12242   Tue Jul 5 14:12:56 2016 varunUpdateElectronicsAntialiasing Filter Update

I am trying to design an antialiasing filter, which also has two switchable whitening stages. I have designed a first version of a PCB for this.

The board takes differential input through PCB mountable BNCs. It consists of an instrumentaiton amplifier made using quad opamp ADA4004, followed by two whitening blocks, also made using ADA4004, which can be bypassed if needed, depending upon a control input. The mux used for this purpose is Maxim MAX4158EUA. These two whitening blocks are followed by 2 the LPF stages. A third LPF stage could be added if needed. These use AD829 opamps. After the LPFs are two amplifiers for giving a differential output through two output BNCs. The schematic is shown in attachment 1: "AA.pdf". The top layers of the layout are shown in attachment 2 (AAtop.pdf), the bottom layers in attachment 3 (AAbottom.pdf), and the entire layout in attachment 4 (AAbrd.pdf). 

The board has 6 layers (in the order from top to bottom):

1) Top signal layer; 

2) Internal plane 1 (GND),

3) Internal plane 2 (+15V),

4) Internal plane 3 (-15V),

5) Internal plane 4 (GND),

6) Bottom signal layer. 

Power: +15, -15 and GND is given through a 4 pin header connector. 

The dimensions of the board are 1550 mil \times 6115 mil (38.1mm\times155.3mm) and the overall dimensions including the protruding BNC edges are 1550 mil \times 7675 mil (38.1mm\times194.9mm)

I would like to have inputs on the layout telling me if any component/trace needs to be changed/better placed, any other things about the board need to be changed, etc.

 

P.S.: I have also added a zipped folder "AA.zip" containing the schematic and board files, as well as the above pdfs.

Attachment 1: AA.pdf
AA.pdf
Attachment 2: AAtop.pdf
AAtop.pdf
Attachment 3: AAbottom.pdf
AAbottom.pdf
Attachment 4: AAbrd.pdf
AAbrd.pdf
Attachment 5: AA.zip
  12266   Thu Jul 7 12:44:52 2016 varunUpdateCDSDAFI update

Attached is a diagram, showing the entire (planned) signal flow of the DAF model. Some thoughts on the implementation after discussion with eric:

1) Since the LSC control signals and ASC signals are running on the c1lsc FE at the same rate as DAFI (16kHz), it would be wise to start from these.

   Current implementation: has a matrix at the end of the LSC PD signals, which selects one of the PD signals and outputs it to the DAFI via IPC communication.

    Proposed Changes: Add another matrix at the end of the LSC PD signals, to give to the second stereo output. Similarly, add two matrices each at the end of the LSC control signals and     the ASC signals. Each matrix must select one of the signals and output it to the DAF via IPC.

2) The PEM running on the c1sus FE system will have to be brought to DAFI in a similar fashon. However, since c1sus runs at 2kHz, there is a possibility of imaging while the signal is    transfered to the DAFI. This could be taken care of by an anti imaging filter, or inserting zeros between two samples coming at to the 16 kHz system from the 2kHz system and then low-passing it to remove the aliased parts. (similar to upsampling)

3) For the SUS control signals, input can be given from a matrix prepared for each optic seperately.

Attachment 1: DAFI.pdf
DAFI.pdf
  12282   Fri Jul 8 22:26:03 2016 varunUpdateCDSDAFI Update: Changes in LSC model

I have added the control signals DARM_CTRL, MICH_CTRL, PRCL_CTRL, SRCL_CTRL, CARM_CTRL, XARM_CTRL, YARM_CTRL, MC_CTRL to the DAFI model from the LSC model via IPC commn.

The changes done to the LSC model include addition of an extra block going to DAFI (attachment 2, red rectangle in attachment 1), and addition of an extra overall output from the LSC, called DAFI_OUT2, which goes to DAFI through IPC link C1:LSC-DAF_2 (attach. 3). Now two distinct inputs can be given to the DAFI, whose intended purpose is to act as two distinct audio signals in the stereo output, but can also be used for arbitrary math. 

I am going to add the following PEM channels as DAF inputs subsequently, in a similar 2 input fashon.

SEIS_GUR1_X_OUT
SEIS_GUR1_Y_OUT
SEIS_GUR1_Z_OUT
SEIS_GUR2_X_OUT
SEIS_GUR2_Y_OUT
SEIS_GUR2_Z_OUT
SEIS_STS_1_X_OUT
SEIS_STS_1_Y_OUT
SEIS_STS_1_Z_OUT
ACC_MC1_X_OUT 
ACC_MC1_Y_OUT
ACC_MC1_Z_OUT
ACC_MC2_X_OUT
ACC_MC2_Y_OUT
ACC_MC2_Z_OUT

 

 

Attachment 1: lsc.png
lsc.png
Attachment 2: lsctodaf.png
lsctodaf.png
Attachment 3: lsctodaf1.png
lsctodaf1.png
  12287   Sun Jul 10 20:08:44 2016 varunUpdateCDSDAFI Update: Changes in LSC and PEM models

I have added the PEM signals mentioned in the previous elog as DAF inputs through PCIE IPC, and compiled and restarted the c1pem and c1daf models. 

Attached are the pictures of the simulink diagram of the addition in the PEM and the DAF. 

Since the signals are moving from a 2kHz clock rate machine to a 16kHz clock rate machine, some imaging effects are possible, which I have to look into.

Attachment 1: pemtodaf.png
pemtodaf.png
Attachment 2: pemindaf.png
pemindaf.png
  12303   Thu Jul 14 23:38:59 2016 varunUpdateCDSc1lsc FE unresponsive

Today, at around 10:30, c1lsc machine froze and stopped responding to ping and ssh after I compiled and restarted c1daf. I think it is due to a large array in one of my codes. The daqd.log file shows the following:


..................................................................
CA.Client.Exception...............................................
    Warning: "Virtual circuit unresponsive"
    Context: "c1lsc.martian.113.168.192.in-addr.arpa:5064"
    Source File: ../tcpiiu.cpp line 945
    Current Time: Thu Jul 14 2016 22:27:42.102649102
..................................................................

I think the c1lsc FE may need a hard reboot.

  12304   Fri Jul 15 12:21:28 2016 varunUpdateCDSc1lsc FE unresponsive

c1lsc is up and running, Eric did a manual reboot today.

Quote:

Today, at around 10:30, c1lsc machine froze and stopped responding to ping and ssh after I compiled and restarted c1daf. I think it is due to a large array in one of my codes. The daqd.log file shows the following:


..................................................................
CA.Client.Exception...............................................
    Warning: "Virtual circuit unresponsive"
    Context: "c1lsc.martian.113.168.192.in-addr.arpa:5064"
    Source File: ../tcpiiu.cpp line 945
    Current Time: Thu Jul 14 2016 22:27:42.102649102
..................................................................

I think the c1lsc FE may need a hard reboot.

 

  12307   Sat Jul 16 00:30:42 2016 varunUpdateCDSDAFI update: Frequency warping | c1lsc unresponsive

Summary: I am trying to implement frequency warping/pitch shifting on the real time FE. Here is a description long overdue:

Description: The overall idea is as follows:

The DFT of a frame x_i[n]  is given by X_i[k] = \sum_{n=0}^{m-1}x_i[n]e^{-j2\pi \frac{kn}{m}}. A matrix W containing all W_{kn} = e^{-j2\pi \frac{kn}{m}} for k, n = 1, 2, ..., m can be calculated and predefined in the code. The input arrival rate is 16384 Hz, i.e. once in every 60 $\mu$s time window. Hence, the fourier coefficients can be updated cumulatively in each cycle using the current value of the input, previous value of the fourier coefficient and the components of the W matrix. This will distribute the computational load of the FFT into all the time windows. Similar operations can be carried out for the inverse STFT.

I have written and run a pseudo-real time code on my CPU. The following is the essence:
 Let the frame-length be M, and the intended scale factor of the frequency warping be 'r'. The frame overlap is 50%. At each clock cycle, the following tasks are performed:  (1 to 3 are routine tasks performed at every clock cycle, 4 is a special task performed only when a frame is filled.)
 1) Take input and apply hanning window to it.
 2) Cumulate X_i[k] for every k using the value of x_i[n] (the input) at that particular instant. Also start to cumulate X_{i+1}[k], which will be later transfered to X_i[k].
 3) Because of 4), we now have 'r+1' filled frames corresponding to output fft. Now take the ifft using two consecutive frames corresponding to only two time series points. The computations required for this task are the same as the computations required for calculation of the fourier coefficients iteratively, since the entire time series ifft is not computed.
 4) Do these special tasks after each frame gets filled:
      At this point, the ffts of the current frame and a previous frame is ready. Let us call them X1 and X2.
      Calculate phase difference between the two.
      Calculate all the interpolated |Y_i| in between these two frames depending upon the scale factor.
      Assign phase of X1 to first Y frame and assign increasing phase to all the other Y frames.
      and also do all the usual non-special tasks.

This code takes about 9-10 microseconds for a cycle with special tasks, and 5-6 microseconds for a cycle with routine tasks on my laptop (brought down from 100 microseconds peak time in the earlier offline implementation due to elemination of explicit dft and reduction in fft size), for a frame size of 32 samples. However, when fed into the c1lsc FE, it crashes, as it has done once again today evening, in the same fashon as yesterday. There could be 2 possible reasons:

1) Size of the array containing the W_{kn} matrix elements is too large for the FE memory,

2) the computations are taking up more than 60 microseconds.

Since there are already a few codes with similar array sizes, I am more inclined to think that 2) is more likely.

Another problem that I am anticipating is that for a 32 point dft and a sampling rate of 16kHz, the frequency resolution achieved is about 500 Hz, which is not sufficient if we need to represent seismic signals. The only way I can think of, for representing such signals with a small number of fft points, is to reduce the effective sampling rate, i.e. do DSP on inputs at a much lower rate than 16kHz (say 1kHz, which will give a resolution of ~30 Hz, or 2kHz giving a resolution of ~60Hz). Another advantage of this method is that it frees up more clock cycles for computation, thus the computational load can be further distributed.  The problem in this implementation is that it will increase the delays.

  12309   Mon Jul 18 18:44:52 2016 varunUpdateCDSc1lsc FE recovered

c1lsc FE is up and running.

Details:

2) The machine was manually rebooted.

3) c1daf was recompiled and installed, with the problematic piece of code removed.

4) NTP timing was adjusted.

5) Frame Builder was restarted.

6) All models on c1lsc machine were restarted.

Attachment 1 shows the CDS status after the recovery. I wont be trying to run frequency warping immediately, I will first finish implementing the other harmless modules first.

Attachment 1: CDS_status160718.png
CDS_status160718.png
  12319   Thu Jul 21 12:03:35 2016 varunUpdateCDSDAFI update: Humming noise in DAFI output

 

Summary: There was always a constant humming noise in the output of speakers of both the audio channels. Tried to resolve the problem. Details are given below:

Details: The source of the noise was the typical 60 Hz (and harmonics), ~13 mV peak to peak output, in at least three channels of the DAC. (two coming from the DAF module, and one not related to the DAF.) Attachment 1 shows the noise in both the DAF channels. As compared to that, the signal coming through the AGC weak, about 6 mV RMS, about the same order as noise. In order to resolve this, the gain of the AGC was increased, so that the RMS output voltage of the Fibox (FBAO, the one at the output) was about 1.23 V RMS. It is approximately equal to +4 dBu, which is the typical expected output of the Fibox, according to the datasheet.

Attachment 1: New_Doc_13.pdf
New_Doc_13.pdf New_Doc_13.pdf
  12320   Thu Jul 21 14:27:24 2016 varunUpdateCDSDAFI Update: Arbitrary Math block

Summary: I have added an arbitrary math block to the DAFI model, which takes two inputs, say X and Y, and can perform various unary and binary operations on them:

Details:

  • Unary Operations:
  1. Delay - There exists a text-based input to specify the amount of delay to be given to a particular signal.
  2. sin()
  3. cos()
  • Binary Operations:
  1. Weighted addition and multiplication: The output is calculated according to the relation: A*X + B*Y + C*X*Y. A, B, C are constant inputs, which can be given through text-based inputs in the GUI.
  2. MAX{X,Y}
  3. MIN{X,Y}

Attachment 1 shows the existing DAFI gui, updated with cascading of various DSP blocks, upto three levels, button-based ENABLE and DISABLE controls for all blocks except arb. math (the control on arb. math. is achieved by clicking on the block.) On clicking the arb. math block one is taken to the dedicated arb. math screen, which has enable buttons for all the processes listed above. A screenshot of this screen is in attachment 2. There is one control input, which controls all the unary operations on X and the binary operations on X and Y, and another control input which controls the unary operations on Y. switching on a particular arb. math process gives a particular control input, which choses the appropriate section of the code. At a time, only one process from the top grey block (corresponding to unary operations on X and binary operations on X and Y) and one process from the bottom grey block (corresponding to unary operations on Y) can be selected. Thus, the outputs which go from the arb. math block to the intermediate matrices (MATRIX1L or MATRIX2L) are:

a) Either an output of unary operation on X or a binary operation on X and Y, the specific one depending upon the control input,

    and

b) Output of a unary operation on Y, again the specific one depending upon the control input

Thus there is apparent asymmetricity in the action of the arb. math block on the two inputs. However, this is done in order to reduce to total number of outputs and control signals, and this can be easily taken care of by interchanging the inputs before the block. 

While compiling this code, the c1lsc machine had crashed once, it was found that this was due to a stray "printf()" command in the c code. This glich in the code now stands rectified  There is a possibility that the previous incidents of the code crashing could also be due to the existence of a printf() command. 

Preliminary Testing: I have done a preliminary testing of the arb math block, i.e. verified that on enabling the sin and cos processes, the output is less that 1, on swithching on the process of weighted avarage and multiplication, the output looks like it is right, for a few simple values of A, B, C, like 0, 1, etc. The delay block however is giving zero output for delay of more than 6 samples.

 

 

 

 

Attachment 1: dafioverview.png
dafioverview.png
Attachment 2: arbmath.png
arbmath.png
  12321   Thu Jul 21 15:03:13 2016 varunUpdateCDSDAFI Update

1) I have added the status summary of the DAFI block to the main FE status overview screen in the c1lsc cloumn. (attachment 1)

2) I have edited all the kissel matrix buttons appropriately, and given them appropriate lables. (attachment 2)

Attachment 1: festatus.png
festatus.png
Attachment 2: matrices.png
matrices.png
  12324   Thu Jul 21 22:02:35 2016 varunUpdateCDSDAFI update: Frequency warping

The code for frequency warping contained a "printf()" command, which had caused the system to crash in one another instance (refer elog 12320) . Hence, I tried running the code tody by removing this line. Unfortunately, this did not work. the model still crashed. Attached is the screenshot of the FE status.

Attachment 1: 07212016.png
07212016.png
  6   Sat Oct 20 11:54:13 2007 waldmanOtherOMCOMC and OMC-SUS work
[Rich, Chub, Pinkesh, Chris, Sam]

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

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

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

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

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

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

[Chub, chris, Pinkesh, Sam]

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

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

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

However, with a little bit of jimmying, the EQ stops are arrayed at all points within a few mm of the breadboard. Meanwhile, Chub has cabled up all the satellite modules and DCPD modules and Pinkesh is working on getting data into the digital system so we can start playing games. Tonight, I intend to mount a laser in Rana's lab and fiber couple a beam into the 056 room so we can start testing the suspended OMC.
  20   Fri Oct 26 21:48:40 2007 waldmanConfigurationOMCFiber to 056
I set up a 700 mW NPRO in Rana's lab and launched it onto a 50m fiber. I got a few mW onto the fiber, enough to see with a card before disabling the laser. The fiber now runs along the hallway and terminates in rm 056. Its taped down everywhere someone might trip on it, but don't go out of your way to trip on it or pull on it because you are curious. Tomorrow I will co-run a BNC cable and attenuate the NPRO output so it can only send a few mW and so be laser safe. Then we can try to develop a procedure to align the beam to a suspended OMC and lock our suspended cavity goodness.

Notes to self: items needed from the 40m
  • ND10 and ND20 neutral density filter
  • EOM and mount set for 4 inch beam height
  • Post for fiber launch to get to 4 inch
  • Mode matching lens at 4in
  • 3x steering mirror at 4in
  • RF photodiode at 4in
  • Post for camera to 4in
  • Light sheild for camera
  • Long BNC cable
Some of these exist at 056 already
  21   Sat Oct 27 19:00:44 2007 waldmanConfigurationOMCHanging, locked OMC with REFL extracted.
I got the OMC locked to the fiber output today. It was much more difficult than I expected and I spent about 30 minutes or so flailing before stopping to think. The basic problem is that the initial alignment is a search in 4-dimensional space and there is naturally only one signal, the reflected DC level, to guide the alignment. I tried to eyeball the alignment using the IR card and "centering" the beams on mirrors, but I couldn't get close enough to get any light through. I also tried to put a camera on the high reflector transmission, but with 1.5 mW incident on the cavity, there is only 1.5 microwatts leaking through in the best case scenario, and much, much less during alignment.

I resolved the problem by placing a high reflector on a 3.5 inch tall fixed mount and picking off the OMC transmitted beam before it reaches the DC diodes. I took the pickoff beam to a camera. The alignment still sucked because even though the beam cleanly transmitted the output coupler, it wasn't anywhere close to getting through the OTAS. To resolve this problem, I visually looked through the back of M2 at M1 and used the IR card to align the beam to the centers of each mirror. That was close enough to get me fringes and align the camera. With the camera aligned, the rest was very easy.

I restored the PDH setup we know and love from the construction days and locked the laser to the OMC with no difficulty. The laser is in Rana's lab so I send the +/- 10V control signal from the SR560 down a cable to 058E where it goes into the Battery+resistor box, the Throlabs HV amplifier, and finally the FAST channel of the NPRO. BTW, a simple experiment sows that about 35 +/- 3 V are required to get an FSR out of the NPRO, hence the Thorlabs HV. The EOM, mixer, splitter, etc is on the edge of the table.

With this specific OMC alignment, ie. the particular sitting on EQ stops, it looks like all of the ghost beams have a good chance of coming clear. I can fit a 2 inch optic in a fixed mount in between the end of the breadboard and the leg of the support structure. A picture might or might not be included someday. One of the ghost beams craters directly into the EQ stop vertical member. The other ghost barely misses M2 on its way down the length of the board. In its current configuration, the many REFL beam misses the leg by about 1.5 inches.
  25   Mon Oct 29 11:07:22 2007 waldmanSoftware InstallationOMCSoftware install on OMS
[Alex, Sam]

We spent a little time this morning working on OMS and getting things restarted. A few changes were made. 1) We put openmotif on OMS so that the burtrb doesn't throw that crappy libXm any more. 2) We upgraded OMS to a 32 kHz sampling rate from 2 kHz. All the filters will have to be changed. We also added a PDH filter path to maybe feedback PDH signals cuz that will be cool. Maybe someday I will write up the very cool channel adding procedure.
  26   Mon Oct 29 12:20:15 2007 waldmanConfigurationOMCChanged OMS filters
I changed the OMS configuration so that some of the OMC-SUS LED channels go to a breakout box so that we can input the PDH error signal. After lunch, we will try to lock the cavity with a PDH error signal and digital filters. Then its on to dither locked stuff. Note that this LED business will have to be changed back some day. For now, it should be extremely visible because there are dangling cables and a hack job interface lying around.
  27   Mon Oct 29 23:10:05 2007 waldmanConfigurationOMCLost in DAQspace
[Pinkesh, Sam]

In setting up a Digital based control of the hanging OMC, we naively connect the Anti-Imaging filter output to an Anti-Aliasing input. This led to no end of hell. For one thing, we found the 10 kHz 3rd order butterworth at 10 kHz, where it should be based on the install hardware. One wonders in passing whether we want a 10 kHz butter instead of a 15 kHz something else, but I leave that for a later discussion. Much more bothersome is a linear phase shift between output and input that looks like ~180 microseconds. It screams "What the hell am I!?" and none of us could scream back at it with an answer. I believe this will require the Wilson House Ghost Busters to fully remedy on the morrow.
Attachment 1: SS.pdf
SS.pdf
Attachment 2: SS.gif
SS.gif
  37   Wed Oct 31 09:45:28 2007 waldmanOtherOMCResolution to DAQland saga
[Jay, Sam]

We did a rough accounting for the linear delay this morning and it comes out more or less correct. The 10 kHz 3rd order butterworth AA/AI filter gives ~90 degrees of phase at 6 kHz, or 42 microseconds. Taken together, the two AA and AI filters are worth 80 microseconds. The 1.5 sample digital delay is worth 1.5/32768 = 45 microseconds. The remaining 160 - 125 = 35 microseconds is most likely taken up by the 64 kHz to 32 kHz decimation routine, assuming this isn't accounted for already in the 1.5 sample digital delay.

It remains to be seen whether this phase delay is good enough to lock the laser to the OMC cavity
  42   Wed Oct 31 23:55:17 2007 waldmanOtherOMCQPD tests
The 4 QPDs for the OMC have been installed in the 056 at the test setup. All 4 QPDs work and have medm screens located under C2TPT. The breadboard mounted QPDs are not very well centered so their signal is somewhat crappy. But all 4 QPDs definitely see plenty of light. I include light and dark spectra below. QPDs 1-2 are table-mounted and QPD 2 is labeled with a bit of blue tape. QDPs 3-4 are mounted on the OMC. QPD3 is the near field detector and QPD4 is the far field. In other words, QPD3 is closest to the input coupler and QPD4 is farthest.

Included below are some spectra of the QPDs with and without light. For QPDs 1 & 2, the light source is just room lights, while 3&4 have the laser in the nominal OMC configuration with a few mWs as source. The noise at 100 Hz is about 100 microvolts / rtHz. If I recall correctly, the QPDs have 5 kOhm transimpedance (right Rich?) so this is 20 nanoamps / rtHz of current noise at the QPD.
Attachment 1: QPD_SignalSpectrum.pdf
QPD_SignalSpectrum.pdf
Attachment 2: QPD_SignalSpectrum.gif
QPD_SignalSpectrum.gif
  43   Thu Nov 1 01:28:04 2007 waldmanOtherOMCFirst digital lock of OMC
[Pinkesh, Sam]

We locked a fiber based NPRO to the suspended OMC tonight using the TPT digital control system. To control the laser frequency, we took the PZT AI output and ran it on a BNC cable down the hallway to the Thorlabs HV box. The Thorlabs is a singled ended unit so we connected the AI positive terminal only and grounded the BNC to the AI shield. We could get a -6 to 1.5 V throw in this method which fed into the 10 k resisotr + 9 V battery at the input of the HV box. The HV out ran to the NPRO PZT fast input.

We derived our error signal from a PDA255 in reflection with a 29.5 MHz PDH lock. The signal feeds into one of the unused Tip/Tilt AA channels and is passed to the PZT LSC drive through the TPT_PDH1 filter bank. In the PZT_LSC filter we put a single pole at 1 Hz which, together with the phase we mentioned the other night (180 degrees at 3 kHz) should allow a 1 kHz-ish loop. In practice, as shown below, we got a 650 Hz UGF with 45 degrees of phase margin and about 6 dB of gain margin.

The Lower figure shows the error point spectrum with 3 settings. REF0 in blue shows lots of gain peaking at 1.5 kHz-ish, just where its expected - the gain was -40. The REF1 has gain of -20 and shows no gain peaking. The current trace in red shows some gain peaking cuz the alignment is better but it also has included a 1^2:20^2 boost which totally crushes the low frequency noise. We should do a better loop sweep after getting the alignment right so we can see how much boost it will really take.

Just for fun, we are leaving it locked overnight and recording the PZT_LSC data for posterity.
Attachment 1: 071101_PZT_firstLoopSweep.pdf
071101_PZT_firstLoopSweep.pdf
Attachment 2: 071101_PZT_firstLoopSweep.gif
071101_PZT_firstLoopSweep.gif
Attachment 3: 071101_OMC_FirstLock_spectra.pdf
071101_OMC_FirstLock_spectra.pdf
Attachment 4: 071101_OMC_FirstLock_spectra.gif
071101_OMC_FirstLock_spectra.gif
  58   Fri Nov 2 12:18:47 2007 waldmanSummaryOMCLocked OMC with DCPD
[Rich, Sam]

We locked the OMC and look at the signal on the DCPD. Plots included.
Attachment 1: 071102_OMC_LockedDCPD.gif
071102_OMC_LockedDCPD.gif
Attachment 2: 071102_OMC_LockedDCPD.pdf
071102_OMC_LockedDCPD.pdf
  59   Sat Nov 3 16:20:43 2007 waldmanSummaryOMCA good day's work

I followed up yesterday's test of the PZT with a whole mess of characterizations of the PZT control and finished the day by locking the OMC with a PZT dither lock and a 600 Hz loop. I haven't analyzed any of the data yet, so its not calibrated in physical units and etc. etc. etc. Since a lot of the sweeps below are of a "drive the PZT, look at the PDH signal" nature, a proper analysis will require taking out the loop and calibrating the signals, which alas, I haven't done. Nonetheless, I include all the plots because they are pretty. The files included below are:

  • DitherLock_sweep: Sweep of the IN2/IN1 for the dither lock error point showing 600 Hz UGF
  • HiResPZTDither_sweep: Sweep of the PZT dither input compared to the PDH error signal. I restarted the front end before the sweep was finished accounting for the blip.
  • HiResPZTDither_sweep2: Finish of the PZT dither sweep


More will be posted later.
Attachment 1: 071103_DitherLock_sweep.png
071103_DitherLock_sweep.png
Attachment 2: 071103_DitherLock_sweep.pdf
071103_DitherLock_sweep.pdf
Attachment 3: 071103_HiResPZTDither_sweep.png
071103_HiResPZTDither_sweep.png
Attachment 4: 071103_HiResPZTDither_sweep.pdf
071103_HiResPZTDither_sweep.pdf
Attachment 5: 071103_HiResPZTDither_sweep2.png
071103_HiResPZTDither_sweep2.png
Attachment 6: 071103_HiResPZTDither_sweep2.pdf
071103_HiResPZTDither_sweep2.pdf
  60   Sun Nov 4 23:22:50 2007 waldmanUpdateOMCOMC PZT and driver response functions
I wrote a big long elog and then my browser hung up, so you get a less detailed entry. I used Pinkesh's calibration of the PZT (0.9 V/nm) to calibrate the PDH error signal, then took the following data on the PZT and PZT driver response functions.:

  • FIgure 1: PZT dither path. Most of the features in this plot are understood: There is a 2kHz high pass filter in the PZT drive which is otherwise flat. The resonance features above 5 kHz are believed to be the tombstones. I don't understand the extra motion from 1-2 kHz.
  • Figure 2: PZT dither path zoom in. Since I want to dither the PZT to get an error signal, it helps to know where to dither. The ADC Anti-aliasing filter is a 3rd order butterworth at 10 kHz, so I looked for nice flat places below 10 KHz and settled on 8 kHz as relatively harmless.
  • Figure 3: PZT LSC path. This path has got a 1^2:10^2 de-whitening stage in the hardware which hasn't been digitally compensated for. You can see its effect between 10 and 40 Hz. The LSC path also has a 160 Hz low path which is visible causing a 1/f between 200 and 500 Hz. I have no idea what the 1 kHz resonant feature is, though I am inclined to point to the PDH loop since that is pretty close to the UGF and there is much gain peaking at that frequency.
Attachment 1: 071103DitherShape.png
071103DitherShape.png
Attachment 2: 071103DitherZoom.png
071103DitherZoom.png
Attachment 3: 071103LSCShape.png
071103LSCShape.png
Attachment 4: 071103DitherShape.pdf
071103DitherShape.pdf
Attachment 5: 071103DitherZoom.pdf
071103DitherZoom.pdf
Attachment 6: 071103LSCShape.pdf
071103LSCShape.pdf
Attachment 7: 071103LoopShape.pdf
071103LoopShape.pdf
  63   Mon Nov 5 14:44:39 2007 waldmanUpdateOMCPZT response functions and De-whitening
The PZT has two control paths: a DC coupled path with gain of 20, range of 0 to 300 V, and a pair of 1:10 whitening filters, and an AC path capacitively coupled to the PZT via a 0.1 uF cap through a 2nd order, 2 kHz high pass filter. There are two monitors for the PZT, a DC monitor which sniffs the DC directly with a gain of 0.02 and one which sniffs the dither input with a gain of 10.

There are two plots included below. The first measures the transfer function of the AC monitor / AC drive. It shows the expected 2 kHz 2d order filter and an AC gain of 100 dB, which seems a bit high but may be because of a filter I am forgetting. The high frequency rolloff is the AA and AI filters kicking in which are 3rd order butters at 10 kHz.

The second plot is the DC path. The two traces show the transfer function of DC monitor / DC drive with and with an Anti-dewhitening filter engaged in the DC drive. I fit the antidewhite using a least squares routine in matlab constrained to match 2 poles, 2 zeros, and a delay to the measured complex filter response. The resulting filter is (1.21, 0.72) : (12.61, 8.67) and the delay was f_pi = 912 Hz. The delay is a bit lower than expected for the f_pi = 3 kHz delay of the AA, AI, decimate combination, but not totally unreasonable. Without the delay, the filter is (1.3, 0.7) : (8.2, 13.2) - basically the same - so I use the results of the fit with delay. As you can see, the response of the combined digital AntiDW, analog DW path is flat to +/- 0.3 dB and +/- 3 degrees of phase.

Note the -44 dB of DC mon / DC drive is because the DC mon is calibrated in PZT Volts so the TF is PZT Volts / DAC cts. To calculate this value: there are (20 DAC V / 65536 DAC cts)* ( 20 PZT V / 1 DAC V) = -44.2 dB. Perfect!

I measured the high frequency response of the loop DC monitor / DC drive to be flat.
Attachment 1: 07110_DithertoVmonAC_sweep2-0.png
07110_DithertoVmonAC_sweep2-0.png
Attachment 2: 071105_LSCtoVmonDC_sweep4-0.png
071105_LSCtoVmonDC_sweep4-0.png
Attachment 3: 07110_DithertoVmonAC_sweep2.pdf
07110_DithertoVmonAC_sweep2.pdf 07110_DithertoVmonAC_sweep2.pdf
Attachment 4: 071105_LSCtoVmonDC_sweep4.pdf
071105_LSCtoVmonDC_sweep4.pdf 071105_LSCtoVmonDC_sweep4.pdf
  79   Wed Nov 7 14:01:31 2007 waldmanOmnistructureOMCFrequency and Intensity noise
One of the biggest problems I had using the PZT to lock was excessive noise. I did a little noise hunting and found that the problem was the cable running from the rack to the laser fast input. As a reminder, the laser has a 4 MHz / volt fast input. We require about 300 MHz to go one FSR, so there is a Thorlabs HV box between at the NPRO fast input which takes 0-10 V -> 0-150 V. The 150 V HV range is worth about 600 MHz of NPRO frequency.

OLD SETUP: Single side of DAC differential (10 Vpp) -> 9V in series with 10 kOhm -> 10 kOhm input impedance of Thorlabs HV -> NPRO

We used the single side of the DAC differential because we didn't have a differential receiver. This turned out to be a bad idea because the cable picks up every 60 Hz harmonic known to man kind.

NEW SETUP: Digital conditioning -> DAC differential (digitally limited to 0 - 1 V) -> SR560 in A-B mode gain 10 (0 - 10 V output)-> Thorlabs HV -> NPRO.

This has almost no 60 Hz noise and works much, much better. Moral of the story, ALWAYS USE DIFFERENTIAL SIGNALS DIFFERENTIALLY !

Note that I may be saturating the SR560 with 10 V output, Its spec'd for 10 Vpp output with 1 VDC max input. I don't know whether or not it can push 10 V out....
  86   Fri Nov 9 00:01:24 2007 waldmanOmnistructureOMCOMC mechanical resonances (Tap tap tappy tap)
[Pinkesh, Aidan, Sam]

We did a tap-tap-tappy-tap test of the OMC to try to find its resonances. We looked at some combination of the PDH error signal and the DCPD signal in a couple of different noise configurations. The data included below shows tapping of the major tombstone objects as well the breadboard. I don't see any strong evidence of resonances below the very sharp resonance at 1300 Hz (which I interpret as the diving board mode of the breadboard). If I get free, I 'll post some plots of the different breadboard resonances you can excite by tapping in different places.

(The "normalized" tapping response is abs(tap - reference)./reference.)
Attachment 1: Fig1.png
Fig1.png
Attachment 2: Fig2.png
Fig2.png
Attachment 3: Fig4.png
Fig4.png
Attachment 4: Fig2.pdf
Fig2.pdf
Attachment 5: Fig1.pdf
Fig1.pdf
Attachment 6: Fig4.pdf
Fig4.pdf
Attachment 7: ResonanceData.zip
  179   Fri Dec 7 11:33:24 2007 waldmanOmnistructureOMCPZT wiring
The 2 pin LEMO connector has got an unmarked pin and a pin marked by a white half-circle.
The unmarked pin is connected to the side of the PZT attached to the mirror.
The marked pin is connected to the side of the PZT attached to the tombstone.
  206   Thu Dec 20 19:05:34 2007 waldmanHowToOMCHOWTO build front ends
For instance, to build the TPT front end code.

  • Save your file /cvs/cds/advLigo/src/epics/simLink/tpt.mdl
  • go to /cvs/cds/advLIGO on the TPT machine
  • do make clean-tpt tpt install-tpt
  • do rm /cvs/cds/caltech/chans/daq/C2TPT.ini (this step is needed because the DAQ install code isn't quite right at the time of this writing.
  • do make install-daq-tpt
  • run starttpt to restart the tpt computer.

Enjoy.
  207   Thu Dec 20 19:10:03 2007 waldmanUpdateOMCStressful reattachment of heater
Photos may follow eventually, but for now here's the rundown. I scraped the heater clean of the thermal epoxy using a clean razor blade. Then I stuffed a small piece of lint free cloth in the OTAS bore and wrapped the OMC in tin foil. With a vacuum sucking directly from the face of the OTAS, I gently scraped the glue off the OTAS aluminum. I wiped both the OTAS and the heater down with an isoproponal soaked lint-free cloth. I put a thin sheen of VacSeal on the face of the heater, wiping off the excess from the edges with a cloth. Then I clamped the heater to the OTAS using 2" c-clamps from the tombstone back to the heater front, making sure the alignment of the OTAS was correct (connector on the absolute bottom, concentric with the OTAS outer diameter). I added a second clamp, then beaded the outside of the joint with a little bit extra VacSeal, just for kicks. I'll leave it covered at least overnight, and maybe for a day or two.

sam
  14193   Wed Sep 5 10:59:23 2018 wgautamUpdateCDSCDS status update

Rolf came by today morning. For now, we've restarted the FE machine and the expansion chassis (note that the correct order in which to do this is: turn off computer--->turn off expansion chassis--->turn on expansion chassis--->turn on computer). The debugging measures Rolf suggested are (i) to replace the old generation ADC card in the expansion chassis which has a red indicator light always on and (ii) to replace the PCIe fiber (2010 make) running from the c1lsc front-end machine in 1X6 to the expansion chassis in 1Y3, as the manufacturer has suggested that pre-2012 versions of the fiber are prone to failure. We will do these opportunistically and see if there is any improvement in the situation.

Another tip from Rolf: if the c1lsc FE is responsive but the models have crashed, then doing sudo reboot by ssh-ing into c1lsc should suffice* (i.e. it shouldn't take down the models on the other vertex FEs, although if the FE is unresponsive and you hard reboot it, this may still be a problem). I'll modify I've modified the c1lsc reboot script accordingly.

* Seems like this can still lead to the other vertex FEs crashing, so I'm leaving the reboot script as is (so all vertex machines are softly rebooted when c1lsc models crash).

Quote:

c1lsc crashed again. I've contacted Rolf/JHanks for help since I'm out of ideas on what can be done to fix this problem.

  14816   Mon Jul 29 19:08:55 2019 yehonathanUpdateLoss MeasurementReviving loss measurement by reflection

1. X arm is totally misaligned in order to measure the Y arm loss using the reflection method. Each measurement round consists of measuring the reflected power when the Y arm is aligned and when it is misaligned.

2. The measurement script used is /scripts/lossmap_scripts/armLoss/measureArmLoss.py. It generates a log file in the /logs folder specifying the alignment and misalignment times.

3. The data extraction script dlData.py processes the raw data in the log file and creates a hdf5 file in the /Data folder conataining the data of the measurement it self.

4. dlData.py labels the the aligned and misaligned datas incorrectly when the number of measurement is odd. I use only even number of measurements then.

5. In order to clip the chaotic transition between the aligned and misaligned states I use tDur attribute smaller than the actual sleep time used in the measurement script itself.

6. plotData.py (written by Gautam) and AnalyzeLossData.ipynb (written by me) can be used to calculate the loss and to plot some analyses (see https://nodus.ligo.caltech.edu:8081/40m/14568). They give roughly the same answer. The descripancy can be explained by the different modulation and ITM transmissions used.

7. I take a measurement of 8 repeatitions. I plot the measured reflected power alternating between the aligned and misaligned states. 

I find that the reflected power is repeatable to within 1%.

This is consistent with the transmission data plotted here which is also repeatable to within 1%.

8. I take an overnight measurement of 100 repeatitions.

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