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ID Date Authorup Type Category Subject
  3915   Sun Nov 14 11:56:59 2010 valeraUpdateCDSTest of ADC noise

 

We missed a factor of 2 in the ADC calibration: the differential 16 bit ADC with +/-10 V input has 20 V per 32768 counts (1 bit is for the sign). I confirmed this calibration by directly measuring ADC counts per V.

So the ADC input voltage noise with +/-10V range around 100 Hz is 6.5e-3 cts/rtHz x 20V/32768cts =  4.0 uV/rtHz. Bummer. 

The ADC quantization noise limit is 1/sqrt(12 fs/2)=1.6e-3 cts/rtHz. Where the ADC internal sampling frequency is fs=64 kHz. If this would be the limiting digitization noise source then the equivalent ADC input voltage noise would be 1 uV/rtHz with +/-10 V range.

  3933   Tue Nov 16 15:32:18 2010 valeraUpdateElectronicsOSEM noise at the output of the satellite box

 I measured the SRM OSEM (no magnets at the moment) noise out of the satellite box with a SRS785 spectrum analyzer. I inserted a break out board into the cable going from the satellite box to the whitening board. The transimpedances of the SRM OSEMs are still 29.2 kOhm. The DC voltages out of the SRM satellite box are about 1.7 V. The signal was AC coupled using SR560 with two poles at 0.03 Hz and a gain of 10.

The noise is consistent with the one measured by the ADC except for the 3 Hz peak which does not show up in the ADC spectrum from Sunday. The peak appears in several channels I looked at. The instrument noise floor was measured by terminating the SR560 with 50 Ohm.

I recommend to change all OSEM transimpedance gains from 29 to 161 kV/A. Beyond this gain one will rail the AA filter module when the magnet is fully out of the OSEM.

The OSEM noise at 1 Hz is about factor of 10 above the shot noise. The damping loops impress this noise on the optics around the pendulum resonance frequency. Also the total contribution to the MC cavity length is sqrt(12) time the single sensor as there are 12 OSEMs contributing to MC length. The ADC noise is currently close but never the less not limiting the OSEM noise below 100 Hz. It can be further reduced by getting an extra factor of 2-3 in whitening gain above ~0.3 Hz. The rms of the ADC input of the modified PRM SD (R64 = 161 kOhm) channel is 10-20 cts during the day with damping loop off and whitening on.

The transimpedance amplifier LT1125CS is also not supposed to be limiting the noise. At 1 Hz the 1/f part of the noise: In<1pA/rtHz and Vn<20nV/rtHz.

Attachment 1: osemnoise.pdf
osemnoise.pdf
  4335   Tue Feb 22 00:18:47 2011 valeraConfiguration c1ioo and c1ass work and related fb crashes/restarts

I have been editing and reloading the c1ioo model last two days. I have restarted the frame builder several times. After one of the restarts on Sunday evening the fb started having problems which initially showed up as dtt reporting synchronization error. This morning Kiwamu and I tried to restart the fb again and it stopped working all together. We called Joe and he fixed the fb problem by fixing the time stamps (Joe will add details to describe the fix when he sees this elog).

The following changes were made to c1ioo model:

- The angular dither lockins were added for each optics to do the beam spot centering on MC mirrors. The MCL signal is demodulated digitally at 3 pitch and 3 yaw frequencies. (The MCL signal was reconnected to the first input of the ADC interface board).

- The outputs of the lockins go through the sensing matrix, DOF filters, and control matrix to the MC1,2,3 SUS-MC1(2,3)_ASCPIT(YAW) filter inputs where they sum with dither signals (CLOCK output of the oscillators).

- The MCL_TEST_FILT was removed

The arm cavity dither alignment (c1ass) status:

- The demodulated signals were minimized by moving the ETMX/ITMX optic biases and simultaneously keeping the arm buildup (TRX) high by using the BS and PZT2. The minimization of the TRX demodulated signals has not been successful for some reason.

- The next step is to close the servo loops REFL11I demodulated signals -> TMs and TRX demodulated signals -> combination of BS and PZTs.

The MC dither alignment (c1ioo) status:

- The demodulated signals were obtained and sensing matrix (MCs -> lockin outputs) was measured for pitch dof.

- The inversion of the matrix is in progress.

- The additional c1ass and c1ioo medm screens and up and down scripts are being made.

  4339   Tue Feb 22 23:11:42 2011 valeraUpdate new medm screens: C1ASS.adl and C1MCASS.adl
Attachment 1: C1MCASS.jpeg
C1MCASS.jpeg
Attachment 2: C1ASS.jpeg
C1ASS.jpeg
  4345   Wed Feb 23 16:34:42 2011 valeraConfiguration pmc lens staged

I put the PMC last mode matching lens (one between the steering mirrors) on a translation stage to facilitate the PMC mode matching.

Currently 4% of incident power is reflected by the PMC. But the reflected beam does not look "very professional" on the camera to Rana - meaning there is too much TEM20 (bulls eye) mode in the reflected beam.

I locked the  PMC  on bulls eye mode and measured  the ratio of the TEM20/TEM00 in transmission to be 1.3%. Thus the PMC mode matching is ~99% and the incident beam HOM content is ~3%.

While working on the PMC I found that the source of PMC "blinking" is not the frequency control signal from MC to the laser (the MC servo was turned off) but possibly some oscillation which could be affected even by a small change of the pump current 2.10 A to 2.08 A. I showed this behaviour to Kiwamu and we decided to leave the the current at 2.08 A for now where things look stable and investigate later.

Attachment 1: PMCrefl.JPG
PMCrefl.JPG
Attachment 2: P1070438.JPG
P1070438.JPG
Attachment 3: P1070439.JPG
P1070439.JPG
  4355   Fri Feb 25 01:48:54 2011 valeraUpdateASCmc auto alignment status

 I made several scripts to handle the mcass configuration and sensing measurements:

- The scripts and data are in the scripts/ASS directory

- The mcassUp script restores the settings for the digital lockins: oscillator gains, phases, and filters. The MC mirrors are modulated in pitch at 10, 11, 12 Hz and in yaw at 10.5, 11.5, and 12.5 Hz. The attached plot shows the comb of modulation frequencies in the MCL spectrum.

- The mcassOn and mcassOff scripts turn on and off the dither lines by ramping up and down the SUS-MC1_ASCPIT etc gains

- The senseMCdecenter script measures the response of the MCL demodulated signals to the decentering of the beam on the optics by imbalancing the coil gains by 10% which corresponds to the shift of the optic rotation point relative to the beam by 2.65 mm (75mm diameter optic) and allows calibration of the demodulated signals in mm of decentering. The order of the steps was MC1,2,3 pitch and MC1,2,3 yaw. The output of the script can be redirected to the file and analyzed in matlab. The attached plot shows the results. The plot was made using the sensemcass.m script in the same directory.

- The senseMCmirror script measures the response of the MCL demodulated signals to the mirror offsets (SUS-MC1_ASCPIT etc filter banks). The result is shown below (the sensemcass.m script makes this plot as well). There is some coupling between pitch and yaw drives so the MC coils can use some balancing - currently all gains are unity.

- The senseMCdofs scripts measures the response to the DOF excitation but I have not got to it yet.

- The next step is to invert the sensing matrix and try to center the beams on the mirrors by feeding back to optics. Note that the MC1/MC3 pitch differential and yaw common dofs are expected to have much smaller response than the other two dofs due to geometry of this tree mirror cavity. We should try to build this into the inversion.

Attachment 1: mcditherlines.pdf
mcditherlines.pdf
Attachment 2: mcdecenter.pdf
mcdecenter.pdf
Attachment 3: mcmirror.pdf
mcmirror.pdf
  4625   Wed May 4 13:51:51 2011 valeraConfiguration Intermittent MC3 UL PD signal

The attached plot shows the 30 day trend of the MC3 UL PD signal. The signal dropped to zero at some point but now it is close to the level it was a few weeks ago. There still could be a problem with the cable.

The rest of the MC1,2,3 PD signals looked ok.

Attachment 1: mc3ulpdmon.pdf
mc3ulpdmon.pdf
  4629   Wed May 4 15:56:09 2011 valeraSummaryGeneralPSL and MC trends

The attached plot shows 2 day trends of the PMC and MC reflected and transmitted power, the PSL POS/ANG QPD signals, and the temperature measured by the dust counter.

The power step in the middle of the plot corresponds to Koji/Jenne PMC realignment yesterday.

It looks like everything is following the day/night temperature changes.

Attachment 1: pslmcdrift.pdf
pslmcdrift.pdf
  4653   Fri May 6 15:42:55 2011 valeraMetaphysicsIOOInput mode cleaner length and 11 MHz modulation frequency

 After Kiwamu set the REFL11 phases in the PRMI configuration (maximized PRM->REFL11I reesponse) I tried to measure the MC length and the 11 MHz frequency missmatch by modulating the 11 MHz frequency and measuring the PM to AM conversion after the MC using the REFL11Q signal. The modulation appears in the REFL11Q with a good snr but the amplitude does not seem to go through a clear minimum as the 11 MHz goes through the MC resonance.

We could not relock the PRMI during the day so I resorted to a weaker method - measuring the amplitude of the 11 MHz sideband in the MC reflection (RF PD mon output on the demod board) with a RF spectrum analyzer. The minimum frequency on the IFR is 11.065650 MHz while the nominal setting was 11.065000 MHz. The sensitivity of this method is about 50 Hz.

  4659   Sat May 7 18:08:54 2011 valeraUpdateIOOMC beam spot centering script

I tried to run the scripts/senseMCdecentering to check the centering of the MC beam spots on the mirrors. The script (csh) produces a lot of error messages on the control room machines. They are machine dependent combination of "epicsThreadOnce0sd epicsMutexLock failed", "Segmentation fault", "FATAL: exception not rethrown". Most of ezcawrite commands fail but not all(?). After running the mcassUp script couple of times all the dither lines came on. The MCL responses to dither lines look qualitatively similar to what it was in February (plot attached). The overall MCL spectrum looks ~100 times lower, presumably due to the analog gain reallocation.

Before that I realigned the beam into the PMC, recentered the PSL QPDs, and the beam into the MC to bring the MC RFPD_DC from ~3 to ~1.5 VDC then tweaked MC2 to bring the MC RFPD_DC from ~1.5 to ~1 VDC.

The mcass dither lines are off now and the loops are disabled.

Attachment 1: mcditherlines2.pdf
mcditherlines2.pdf
  4660   Sun May 8 16:32:52 2011 valeraUpdateIOOMC beam spot centering

 Kiwamu told me that the CDS matrix notation has changed and the 40m front end code has changed since February. I changed the senseMCdecentering script to reflect that. The other problems were: the "-" sign in ezcastep on ubuntu is not recognized - I used the known workaround of using "+-" instead; the echo command in csh script on ubuntu does not make a new line - but the echo " " does. The script ran on ubuntu with one error message "FATAL: exception not rethrown" but it finished nevertheless. The data appeared ok.  On centos machine the script produced "Segmentation fault'. The matlab script sensemcass.m now calculates the position on the MC mirrors in mm. The attached table shows the MC spot positions in mm:

    feb 26 2011      may 08 2011
MC1 pit   1.6   1.9
MC2 pit   6.4   9.0
MC3 pit   1.4   2.0
MC1 yaw   -1.5   -1.7
MC2 yaw   1.0   0.2
MC3 yaw   -1.3   -1.9

I had to rephase the lockin digital phases by tens of degrees. I don't know why this should happen at ~10 Hz.

 

  4663   Mon May 9 09:37:51 2011 valeraUpdatePSLPSL and MC trends

The attached plot shows 7 day trends of the MC and PMC power levels, PSL QPDs, and temperature. The MC stayed locked for ~40 hours over the weekend. The temperature swings were somewhat smaller over the past couple of days but one should remember to turn the PSL HEPA down after working on the table. Steve turned the HEPA flow from 100% down to 20% on Thursday and posted the reminder signs on the PSL enclosure.

Attachment 1: pslmcdrift2.pdf
pslmcdrift2.pdf
  4674   Tue May 10 00:44:52 2011 valeraUpdateIOOMC2 centering

Kiwamu, Koji, Valera

We centered the beam on MC2 in pitch by moving the MC1,2,3 in the following combination [-9,+3,-7]. This actuation vector mostly moves the spot on MC2 vertically. The attached plot shows the dither before and after the centering. We monitored the demodulated signals and saw the reduction of the MC2 pit response from -1.0 to -0.22 which corresponds to the beam spot position change from 9 to 2 mm. Thus all the spots on MC mirrors are within 2 mm of the center. We estimate based on the distance between the MC1-MC3 of 20 cm, the distance from the center between MC1 and MC3 to the end of the Faraday isolator of 80 cm, and the aperture of the FI of 12 mm, the maximum angle out of MC of 3/200 rad. Which implies the maximum differential spot motion of 3 mm not to be limited by the FI aperture.

Attachment 1: mc2centering.pdf
mc2centering.pdf
  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.
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  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
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