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ID Date Author Type Category Subjectdown
  16054   Tue Apr 20 10:52:49 2021 Anchal, PacoUpdateSUSAC gain coil output balancing for IMC

[Paco, Anchal]

  • We adopted the following procedure to balance the coil output gains using a high-frequency (> 10 Hz) excitation on "C1:SUS-MCX_ASCPIT_EXC", "C1:SUS-MCX_ASCYAW_EXC", and "C1:SUS-MCX_LSC_EXC", where X is one of {1, 2, 3} for the three IMC optics, and the cavity sensors (MC_F, and MC_TRANS);
    1. We load the new input matrix found on March-23rd.
    2. Using awggui, we launch a single 23.17 Hz sine with 500 - 1000 counts amplitude on the aforementioned channels.
      • We are still unable to launch multiple excitations simultaneously through either API (python-awg or dtt-awggui) devilno
    3. Using our built-in hominid neural networks, we look at the "C1:IOO-MC_F", "C1:IOO-MC_TRANS_PIT_IN", and "C1:IOO-MC_TRANS_YAW_IN" exponentially averaging power spectra, on and about the excitation frequency, and identify the amount of cross-coupling going into angular or longitudinal motion depending on the excited degree of freedom.
    4. We step the "C1:SUS-MCX_URCOIL_GAIN", "C1:SUS-MCX_ULCOIL_GAIN", "C1:SUS-MCX_LRCOIL_GAIN", "C1:SUS-MCX_LLCOIL_GAIN" coil output gains by hand in the presence of an excitation (e.g. "LSC") along a given degree of freedom (e.g. along "PIT") to try and minimize the coupling.
    5. We iterate step (4) until we find an optimum gain set, and move on to another optic.


  • For MC2 the optimal gains changed from: [1.0, -1.0, 1.0, -1.0] → [1.05, -1.05, 0.995, -1.03] **
    • Here we were able to first decouple PIT and YAW from a POS excitation almost entirely (see Attachment #1), but weren't as successful in decoupling YAW and POS from PIT, or PIT and POS from YAW excitations (Attachment #2).
  • For MC1 the optimal gains changed from: [1.0, 1.0, 1.0, 1.0] → [0.282, 0.035, 0.302, 2.46] **
    • Here we mostly succeeded in decoupling POS from YAW and PIT excitations (see Attachments #3 - 4).
  • For MC3 the optimal gains changed from: [1.0, -1.0, 1.0, -1.0] → [0.126, -0.123, 0.298, -0.306] **
    • Here the LSC_EXC didn't show up on MC_F (??), and the PIT/YAW excitations decouple by virtue of seemingly low gains, so maybe the optimum is an artifact of the lower coil gains...
    • Plots are to follow up for this one.

** The notation here is [UL, UR, LR, LL]

Attachment 1: POS2PYuncoupled.pdf
POS2PYuncoupled.pdf POS2PYuncoupled.pdf
Attachment 2: PIT2PYuncoupled.pdf
PIT2PYuncoupled.pdf PIT2PYuncoupled.pdf
Attachment 3: MC1YAWexc.pdf
Attachment 4: MC1PITexc.pdf
  960   Wed Sep 17 19:13:47 2008 AlbertoUpdateGeneralABSL: status
I installed the setup for measuring TEM01/10 on the X end table.
I'm leaving. I shut the laser, flipped down the flipper mirror, disconnected the pzt drive signal from the laser.
For Jenne. The power cable for the Guralps' board is now connected to the PDH box on my instruments cart but you can take it.
  979   Mon Sep 22 20:00:35 2008 AlbertoUpdateGeneralABSL: running measurement
I'm leaving the X arm locked on the TEm01 mode while a measurement is running. Just please wait for 40 minute if you need the interferometer tonight.
  956   Wed Sep 17 13:58:36 2008 AlbertoUpdateGeneralABSL: results from the X arm
Today I repeated the measurement of the FSR on the X arm cavity. The noise in the transmitted power that made the measures fluctuate was much reduced after last night Rob worked on the interferometer. The X arm cavity length is now: (38.4580+/-0.0003)m. I'm attaching a summary of the data I've taken.

I'm now preparing the setup to measure the transverse mode spacing.
Attachment 1: Sept17_XarmFSRmeasurement_report.ps
  946   Sun Sep 14 18:30:32 2008 AlbertoUpdateGeneralABSL: measured X arm
Today I measured the X arm FSR.
Hi moved the fast PD (Thor Labs PDA255) from the Y end table to the X end table. I had to use a beam splitter to pick out the transmitted beam from the cavity beam and send it to the PD. I did not want to interpose the BS before the TRANS X PD, so I had to move the ETMXT camera to an other place in the table to gain some room. Now the beam that used to go directly to the camera is 50% split and goes also to the PD. I had to put a lens to focus the beam on the PD. The transmitted beam is currently not aligned to the ETMXT camera, I need to fix the alignment of the BS before.
I'm now doing a rough scan of a frequency range 5 times as large as the FSR. I'll post the results soon.
  947   Sun Sep 14 19:29:07 2008 AlbertoUpdateGeneralABSL: measured X arm

Today I measured the X arm FSR.
Hi moved the fast PD (Thor Labs PDA255) from the Y end table to the X end table. I had to use a beam splitter to pick out the transmitted beam from the cavity beam and send it to the PD. I did not want to interpose the BS before the TRANS X PD, so I had to move the ETMXT camera to an other place in the table to gain some room. Now the beam that used to go directly to the camera is 50% split and goes also to the PD. I had to put a lens to focus the beam on the PD. The transmitted beam is currently not aligned to the ETMXT camera, I need to fix the alignment of the BS before.
I'm now doing a rough scan of a frequency range 5 times as large as the FSR. I'll post the results soon.

I'm leaving a long measurement running. I should be back later on. If I won't, whoever wanted to use the interferometer has just to shut the NPRO laser in the AP table.
  987   Wed Sep 24 17:57:04 2008 AlbertoUpdateGeneralABSL: FSS Slow Actuator Control
Rana, Alberto

Today when I started working with the PLL that I use to control the secondary laser on the ABSL experiment, I found that the beat between the two lasers was at a much higher temperature of NPRO than usual (about one Celsius Degrees higher, 49.79 instead of 48.7). It turned out that the main beam frequency had changed, and so had its frequency, because of a too much high value of the slow actuator gain on the FSS. We looked at the trend for the gain and noticed it had changed from 0.3 to 3 at about noon today. We brought it back to the old value and also optimized the single gains in the FSS slow servo to obtain a faster and stabler response to step changes in the laser temperature.

It is very important for the ABSL experiment that the frequency and the NPRO temperature of the main laser do not change.

** update:
you asked for:   diff 2008/09/25,0:00 2008/09/25,8:50:19 utc 'FSS[-_]SLOW'
LIGO controls: differences, 2008 09/25 00:00:00 utc vs. 2008 09/25 08:50:19 utc
__Epics_Channel_Name______   __Description__________   __value1____     __value2____
C1:PSL-FSS_SLOWKD                                      0.000000         0.001000
C1:PSL-FSS_SLOWKI                                     -0.001000        -0.001700
C1:PSL-FSS_SLOWKP                                     -0.000300        -0.001000

It seemed later that it was not being cool with the derivative gain up at -0.001, so I set it to zero. We really need some documentation on this
loop (e.g. pseudo code and a PID tuning procedure). Note that the PID record as documented in the EPICS Reference Manual
has been deprecated and so we run a perl script that Tobin wrote.
  8303   Mon Mar 18 12:02:12 2013 AnnalisaConfigurationABSLABSL setup for g-factor measurement of PRC
The ABSL technique has been already used in the past to measure the absolute length of the interferometer's optical cavities by means of an auxiliary laser source, as described in LIGO-P1200048-v3 and in Alberto Stochino thesis work.
Using the same technique it is possible to measure the g-factor of the power recycling cavity by measuring the cavity Transverse Mode Spacing.
Plan for experimental setup
The auxiliary laser is set on the POY table and is injected through the ITMY window in way to follow the same path of the POY beam. It hits the AR wedge of ITMY and is reflected back to the BS and the PRM.
Since the main beam is P-polarized, all the optics in the central IFO are P-polarization dependent, so it is useful to P-polarize the auxiliary beam before it enters the IFO.  
I made a mode matching calculation with a la mode script, in order to mode match the auxiliary beam waist to the waist of the main laser.
However, before ordering and installing steering optics and mode maching lenses, I'm waiting to know whether someone has an NPRO laser to install on the END table in place of the broken one, otherwise the one I'm using could be taken.
In this case a possibility could be to take the auxiliary beam from the end table with an optical fiber, but it means to use the auxiliary laser alternately to lock the arm or make a measurement of TMS. If so, a new calculation for the mode matching needs to be done.
Anyway, I hope that another laser will be found!
In order to phase lock the auxiliary beam with the main beam, the latter will be taken from the PSL table after the PMC through a single mode fiber, which will be brought up to the POY table. This solution results to be more reliable then taking the POY beam to phase lock the two laser, because POY is related to the locking. 
The signal with the beat note between the two lasers can be detected by the transmission from PR2 (POP). 
  4940   Tue Jul 5 17:38:46 2011 kiwamuUpdateABSLABSL laser frequency-locked

In this past weekend the ABSL laser was successfully frequency-locked to the PSL laser with a frequency offset of about 100 MHz.

In the current setup a mixer-based frequency discriminator is used for detection of the beat-note frequency.


Setup for frequency locking

 The diagram below shows the setup for the frequency locking.


  According to a brief check of the loop oscillation it implies that the UGF is around 40 kHz.
Of course I will measure the open-loop over a wide frequency range at some point.
The lock was quite robust and it was able to stay locked for more than an hour as far as I observed.
(Beat-note detection and its amplification)
 The fast RFPD, which is standing on the PSL table to detect the beat-note (see the picture on #4939), showed the signal level of -16 dBm.
Then the signal goes through the RF amplifier stage to have an appropriate power level at the mixer in the frequency detection stage.
Before the signal goes into the amp. stage I put a power splitter so that I can see a signal on a spectrum analyzer.
(Frequency detection)
 In the mixer-based frequency discriminator, the length difference between two coax. cable was chosen to be 1 m.
This length difference gives us a zero cross point (operation point) of ~100 MHz and linear range of ~ +/-100MHz, which can sufficiently cover the FSR of PRC: 22MHz.
(Control filter)
 After the signal goes through the freq. discriminator, a low noise amplifier, ITHACO 1201 was installed as a control filter.
The reason I chose ITHACO 1201 was that it has a larger output range than that of SR560.
ITHACO 1201 can go to +/- 15V, which means the ABSL laser should be able to track the frequency by about +/- 65 MHz without a thermal actuation.
Right now a single pole was put at 1 Hz for an easy lock.
The output from 1201 goes directly to the laser PZT, whose input is on the front panel of the laser controller.


Temperature setpoints

 During the work I found three temperature points, where we can observe the beat-note signal within a bandwidth of 1 GHz.
 Here is a summary of the temperature set points :
    PSL temperature = 31.71 deg
    ABSL temperature = 44.19 deg (not good),
                                       47.25 deg (chosen to be nominal set point),
                                       50. 23 deg
 The first one (44.19 deg) wasn't good because changing the temperature of the ABSL laser also changes the amplitude of the beat-note significantly.
In a worst case the signal completely disappeared when the ABSL laser was at a certain temperature close to 44.19 deg.
The other two temperature points seemed good. I eventually chose the second one (47.25 deg) for the nominal set point.
Note that the current readout has been 1.81 A on the laser controller.
  5117   Thu Aug 4 09:42:19 2011 KojiUpdateABSLABSL Laser shutter closed

The shutter of the ABSL laser is closed for the vent work.

  5064   Sat Jul 30 00:33:33 2011 KojiUpdatePSLABSL Laser crystal temp left largely excited & left unattended for more than 3hours

I found that the ref cav trans CCD view was blinking with 30-50 fringe amplitudes. This meant the laser freq was swinging ~50GHz.

I checked the ABSL laser and the SG out of a lock-in amplifier was connected to the slow input.

This was shaking the laser temp from 29degC to 46degC. This was the cause of the fringe swinging.
This big excitation changing the output power too as the temp was changed across it mode-hop region.

I have disconnected the excitation from the laser no matter how useful experiments were took place as there was no e-log entry about this.

I need the explanations

1. Why our precious laser is exposed to such a large swing of temperature?

2. Why the excitation is left like that without any attendance?

3. Why there was no elogging about this activity?

  5065   Sat Jul 30 02:47:43 2011 ranaUpdatePSLABSL Laser crystal temp left largely excited & left unattended for more than 3hours

 Hmm. Should have only been +/- 1 GHz. Some setting got changed apparently...

This is a part of the RefCav temperature measurement setup. You'll get an elog from Jenny very soon.

  4996   Wed Jul 20 06:52:01 2011 SureshUpdateLSCABSL - PSL beat lock

The ABSL locking setup to the PSL is down. 

According the plan, I started to use the IR beam dumped after the doubling crystal for the IR beat lock (Sonali's project).  The beat lock was disturbed when I shifted some clamps to make way for a few mirrors.  So I set about fixing the beat lock.  I reobtained the lock but noticed that the net beam power reaching the Newfocus 1611 detector was around 15mW.  10mW from the ABSL and 5mW from PSL.

This is much too high as the maximum allowed on 1611 is 2mW. 

I therefore started to adjust the power levels by using  Y1-1064-45S mirrors at non-45 deg angles.  However Rana pointed out that this would lead to amplitude noise due to the mirror vibrations.  I then switched to using beam splitters as pick offs.   This is better than using neutral density filters since the back scatter is lower this way.

David wanted some of the ABSL beam for his SURF student.  So I changed the mirror after beam expanding telescope on the ABSL route to provide this power.  We also installed a pair of half wave plates and a PBS to allow us smooth power level control on this beam.

The beat lock setup is now down and needs to be completed for PRCL and SRCL measurements.



  8581   Wed May 15 17:38:49 2013 JamieSummaryCDSAA/AI requirements


What this means:

  • We definitely have enough DACs for the ALS PZTs.  The free channels are also in the right places: at the end stations and in the c1ioo FE, which is close to the PSL and hosts the c1als controller.
  • We appear to have enough ADCs for the QPD in c1ioo.
  • We don't have any available DAC outputs in c1lsc for the Fibox.  If we can move the Fibox to the IOO racks (1X1, 1X2) then we could send LSC channels to c1ioo and use c1ioo's extra DAC channels.

Of course we'll have to investigate the AA/AI situation as well.  I'll try to asses that in a follow up post.

It looks like we have spare channels in the AA chassis for the existing c1ioo ADC inputs to accommodate the POP QPD. 

We need AI interfaces for the ALS PZTs.  What we ideally need is 3x D000186, which are the eurocard AI boards that have the flat IDC input connects that can come straight from the DAC break-out interfaces.  I'm not finding any in the spares in the spare electronics shelves, though.   If we can't find any we'll have to make our own AI interfaces.

  15709   Fri Dec 4 19:23:40 2020 KojiUpdateElectronicsAA/AI board testing ongoing

I have the setup built for the AA/AI board testing around the PD testing area. Please let me leave it like that for a week or so.

12/4 TF Tested 5 PCBs
12/6 TF Tested 19 PCBs (12min/PCB) - found 1 failure (S2001479 CH1) -> Fixed 12/11
12/8 TF Tested 16 PCBs (12min/PCB)
       PSD Tested 4 PCBs (11min/PCB)
12/11 TF Tested 10 PCBs + 1 fixed channel (All channels checked)
       PSD Tested 10 PCBs (11min/PCB)
12/14 PSD Tested 4 PCBs (6.5min/PCB) fixed noise issue of 2 ch, TF issue of 1 ch
12/15 PSD Tested 32 PCBs (6.5min/PCB) fixed noise issue of 1ch
Temp dependence measurement
Crosstalk measurement


  422   Wed Apr 16 21:11:12 2008 ranaSummaryDAQAA/AI Filters for the DAQ & FE systems
I used Foton to make up some new filters which will be used all over the project in order to downsample/upsample.

There will be 2 flavors:

  • The first one will be a downsampling filter for use in the DAQ system.
    Whenever you specify a sampling rate in the .ini files below the natural rate of the ADC,
    the data will be downsampled using this filter (called ULYAW_0 in the plot). This one was
    designed for flat bandpass and a 'good' bandstop but no care given to the phase shift.

  • The second one will be used in the FE systems to downsample the ADC signal which is often
    sampled at 64 kHz down to something manageable like 2k or 16k. This one was tweaked for
    getting less phase lag in the 'control' band (usually 3x or so below Nyquist).

Here is the associated filter file:
# DESIGN   ULYAW 0 zpk([0.512+i*1024;0.512-i*1024;2.048+i*2048;2.048-i*2048], \
#                      [515.838+i*403.653;515.838-i*403.653;318.182+i*623.506;318.182-i*623.506;59.2857+i*827.88; \
#                      59.2857-i*827.88],0.988553,"n")
# DESIGN   ULYAW 1 zpk([0.512513+i*1024;0.512513-i*1024;1.53754+i*2048;1.53754-i*2048], \
#                      [200+i*346.41;200-i*346.41;45+i*718.592;45-i*718.592],1,"n")
# DESIGN   ULYAW 2 zpk([0.768769+i*1024;0.768769-i*1024;1.53754+i*2048;1.53754-i*2048], \
#                      [194.913-i*331.349;194.913+i*331.349;53.1611+i*682.119;53.1611-i*682.119],1,"n")
###                                                                          ###
ULYAW    0 21 3      0      0 DAQAA         0.00091455950698073    -1.62010355523604     0.67259370084279    -1.84740554170818     0.99961738977942
                                                                   -1.72089534598832     0.78482029284220    -1.41321371411946     0.99858678588255
                                                                   -1.85800352005967     0.95626992044093     2.00000000000000     1.00000000000000
ULYAW    1 21 2      0      0 FEAA            0.018236566955641    -1.83622978049494     0.85804776530302    -1.84740518752455     0.99961700649533
                                                                   -1.89200532023258     0.96649324616546    -1.41346289594856     0.99893883979950
ULYAW    2 21 2      0      0 ELP             0.015203943102927    -1.84117829296043     0.86136943504058    -1.84722827171918     0.99942556512240
                                                                   -1.89339022414279     0.96048849609619    -1.41346289594856     0.99893883979950
Attachment 1: DAQ_filters_080416.pdf
  3911   Fri Nov 12 20:40:51 2010 josephb, yuta, valeraConfigurationElectronicsAA voltage range

We changed the range of the two SUS AA boards in the corner from +/-2 V to +/-10 V by changing the supply voltage from +/-5 V to +/-15 V. The change was made by switching the AA power feed wires on  the cross connect. The max supply according to the spec of DRV134/INA134 is +/-18 V.

We checked the new range by applying the voltage to the input of AA and measuring the output going to the ADCs. The local damping MC1,2,3 appears to work.

  5022   Sun Jul 24 20:36:03 2011 haixingSummaryElectronicsAA filter tolerance analysis

Koji and Haixing,

We did a tolerance analysis to specify the conner frequency for passive low-pass filtering in the AA filter of Cymac. The
link to the wiki page for the AA filter goes as follows (one can have a look at the simple schematics):

Basically, we want to add the following passive low-pass filter (boxed) before connecting to the instrumentation amplifier:


Suppose (i) we have 10% error in the capacitor value and (ii) we want to have common-mode rejection
error to be smaller than 0.1% at low frequencies (up to the sampling frequency 64kHz), what would be
conner frequency, or equivalently the values for the capacitor and resistor, for the low-pass filter?

Given the transfer function for this low-pass filter:
transfer_function.png     f0.png
and the error propagation equation for its magnitude:
we found that the conner frequency needs to be around 640kHz in order to have
DT.pngwith Dc.png

  5023   Sun Jul 24 20:47:21 2011 ranaSummaryElectronicsAA filter tolerance analysis

This is sort of OK, except the capacitor connects across the (+) terminals of the two input opamps, and does not connect to ground.

Also, we don't care about the CMRR at 64 kHz. We care about it at up to 10 kHz, but not above. The sample frequency of the ADC is 64 kHz, but all of the models run at 16 kHz or less, so the Nyquist frequency is 8 kHz.

And doesn't the value depend on the resistors?

  5024   Sun Jul 24 22:19:19 2011 haixingSummaryElectronicsAA filter tolerance analysis


>> This sort of OK, except the capacitor connects across the (+) terminals of the two input opamps, and does not connect to ground:



>> Also, we don't care about the CMRR at 64 kHz. We care about it at up to 10 kHz, but not above.

In this case, the conner frequency for the low-pass filter would be around 100kHz in order to satisfy the requirement.

>>And doesn't the value depend on the resistors?

Yes, it does. The error in the resistor (typically 0.1%)  is much smaller than that of the capacitor (10%). Since the resistor error propagates in the same as the capacitor,
we can ignore it.

Note that we only specify the conner frequency (=1/RC) instead of R and C specifically from the tolerance analysis, we still need to choose appropriate
values for R and C with the conner frequency fixed to be around 100kHz, for which we need to consider the output impedance of port 1 and port 2.



  5038   Tue Jul 26 21:11:40 2011 haixingSummaryElectronicsAA filter tolerance analysis

Given this new setup, we realized that the previous tolerance analysis is incorrect. Because the uncertainty in the capacitance value
does not affect the common mode rejection, as two paths share the same capacitor. Now only the imbalance of two resistors is relevant.
The error propagation formula goes as follows:

We require that the common-mode rejection error at low frequency up to 8kHz, namely
with , one can easily find out that the corner frequency needs to be around 24kHz.


  4748   Thu May 19 12:09:41 2011 josephbUpdateCDSAA filter box pulled from 1X5, optic suspensions currently off

[Steve, Joe]

Steve pulled the top AA filter box from 1X5 which handled some of the suspensions channels.  We turned off all the watchdogs before pulling it out, as well as recorded which cables were connected to which inputs.

The case  is undergoing a structural modification to have the ADC adapter card which previously was loosely connected via cables, securely attached to the case.

Steve still wants to do some cabling in the rack while the box is out, and will return it this afternoon once he has finished that.

  4750   Thu May 19 17:53:03 2011 steveUpdateCDSAA filter box modified at 1X5


[Steve, Joe]

Steve pulled the top AA filter box from 1X5 which handled some of the suspensions channels.  We turned off all the watchdogs before pulling it out, as well as recorded which cables were connected to which inputs.

The case  is undergoing a structural modification to have the ADC adapter card which previously was loosely connected via cables, securely attached to the case.

Steve still wants to do some cabling in the rack while the box is out, and will return it this afternoon once he has finished that.

 Job is done. Sus damping are back on. Cabling-strain reliefing are  not finished yet at 1X5 and 1X4

Attachment 1: P1070727.JPG
  15744   Tue Dec 22 22:11:37 2020 gautamUpdateCDSAA filt repaired and reinstalled

Koji fixed the problematic channel - the issue was a bad solder joint on the input resistors to the THS4131. The board was re-installed. I also made a custom 2x4-pin LEMO-->DB9 cable, so we are now recording the PMC and FSS ERR/CTRL channel diagnostics again (spectra tomorrow). Note that Ch32 is recording some sort of DuoTone signal and so is not usable. This is due to a misconfiguration - ADC0 CH31 is the one which is supposed to be reserved for this timing signal, and not ADC1 as we currently have. When we swap the c1ioo hosts, we should fix this issue.

I also did most of the work to make the MEDM screens for the revised ASC topology, tried to mirror the site screens where possible. The overview screen remains to be done. I also loaded the anti-whitening filters (z:p 150:15) at the demodulated WFS input signal entry points. We don't have remote whitening switching capability at this time, so I'll test the switching manually at some point.


The main issue is that in the AA chassis I built, Ch14 (with the first channel as Ch1) has the output saturated to 28V (differential). I'm not sure what kind of overvoltage protection the ADC has - we frequently have the inputs exceed the spec'd +/-20 V (e.g. when the whitening filters are engaged and the cavity is fringing), but pending further investigation, I am removing the SCSI connection from the rear of the AA chassis.

  5168   Wed Aug 10 12:28:22 2011 Ishwita , ManuelUpdatePEMAA board gain

We used a function generator, an oscilloscope and the Data Viewer to check the gain of the new AA board (used for the seismometers). Putting a sine wave of 0.3V (using a function generator) to the AA board, we could see about 500 counts in the Data Viewer. The calibration of the ADC is 214 counts/volt, so the AA board gives to the ADC an output of 0.03V. This proves that the AA board has a gain of 0.1. Guralp1 and STS1 (Bacardi), both have a gain of 10 now, that balance the AAboard gain of 0.1. If we consider the gain of AA board in our calibrated power spectrum plot of seismic signals from Guralp1 and STS1 (Bacardi), we get the following plot:


  4959   Mon Jul 11 10:10:31 2011 IshwitaConfiguration AA board

The AA board shown in attachment 1 will be used in the seismometer hardware setup. A cartoon of this setup is shown in attachment 2.

BNC connectors are required for the seismometer breakout boxes. So the four-pin LEMO connectors present in the AA board were removed and panel mount BNC connectors were soldered to it. Red and blue colored wires were used to connect the BNC connectors to the board. Red wire connects the center of the BNC connector to a point on the board and that connection leads to the third leg (+IN) of the IC U### and the blue wire connects the shield of the BNC connector to the second leg (-IN) of the IC U###.

All the connections (including BNC to the AA board and in the AA board to all the filters) were tested using a multimeter by the beeping method and it was found that channel 10 (marked as C10) had a wrong connection from the point where the red wire (+ve) was connected to the third leg (+IN) of IC U91  and channel 32 (marked as C32) had opposite connections meaning the blue wire is connected to the third leg (+IN) of IC U311 and red wire is connected to the second leg (-IN) of IC U311.

Attachment 1: P7080305.JPG
Attachment 2: seismometers.png
  4979   Sat Jul 16 18:54:05 2011 Ishwita, ManuelConfigurationElectronicsAA board

We fixed the anti-aliasing board in its aluminum black box,  the box couldn't be covered entirely because of the outgoing wires of the BNC connectors, so we drilled additional holes on the top cover to slide it backwards by 1cm and then screw it.

We had to fix the AA board box in rack 1X7, but there wasn't enough space, so we tried to move the blue chassis (ligo electro-optical fanout chassis 1X7) up with the help of a jack. We removed the blue chassis' screws but we couldn't move it up because of a piece of metal screwed above the blue chassis, then we weren't able to screw the two bottom screws again anymore because it had slided a bit down. Thus, the blue chassis (LIGO ELECTRO-OPTICAL FANOUT CHASSIS 1X7) is still not fixed properly and is sitting on the jack.

To accommodate the AA board (along with the panel-mounted BNC connectors) in rack 1X7 we removed the sliding tray (which was above the CPU) and fixed it there. Now the sliding tray is under the drill press.


Attachment 1: DSC_3236.JPG
Attachment 2: pic1.png
Attachment 3: DSC_3237.JPG
  7543   Sun Oct 14 20:51:20 2012 DenUpdatePEMAA board



 But every ~40 min ETMX motion is much higher then ground motion at low frequencies (<5 Hz). I wonder if this a reaction of a table to outside disturbances or accelerometer issue. 

 This could come from AA board, its range is +/- 2.5 V, RMS of the ETMX table motion is a few times higher then ground motion, so ETMX accelerometer signal was corrupted.


As this small AA range has already caused problems before, I decided to increase it. I've looked through the board scheme and found that all its differential line receives and output amplifiers have absolute maximum range of 40V. We used KEPKO power supply for this board with a voltage range up to 6 V. So I've replaced it with a BK PRECISION power supply and set it to +/- 15 V. Now AA board range is 7.5 V.


I'll leave accelerometers near ETMX table. It's interesting to measure table motion in the morning when trucks drive by.

  7546   Mon Oct 15 10:14:22 2012 DenUpdatePEMAA board



 I'll leave accelerometers near ETMX table. It's interesting to measure table motion in the morning when trucks drive by.

 That low frequency effect was due to AA board, now it is gone.

  8555   Thu May 9 00:05:12 2013 rana, Koji, JenneSummaryLSCAA and AI change

We would like to increase the UGF of the PRC loop so as to allow more suppression of the PRC signal and less pollution of the MICH signal (remember that the PRC/MICH optical gain ratio is huge).

We were already losing phase because of delay in the LSC - SUS digital link. In addition to that, a major source of delay is the analog anti-aliasing (on the LSC error signals before they enter the ADC) and the analog anti-imaging (between the SUS DAC and the coil driver).

 IN addition to these, the other major sources of phase lag in the system are the FM5 filter in the LSC-PRC filter bank, the digital upsampling and downsampling filters, and the DAC sample and hold.

In the near term, we want to modify these analog filters to be more appropriate for our 64 kHz ADC/DAC sample rate. Otherwise, we are getting the double phase lag whammy.


Staring at the schematics for the AA (D000076-01) and the AI (D000186-A), we determined a plan of action.

For the AA, we want to remove the multi-pin AA chip filter from Frequency Devices, Inc. and replace it with a passive LC low pass. Hopefully, these chips are socketed. Rana will design an appropriate LC combo and elog; we should make the change on a Wednesday afternoon so that we have enough soldering help.

For the AI, the filter is a dual bi-quad using discrete components and LT1125 opamps. Not so clear what to do with these. The resistors are all the noisy thick film kind and maybe should be replaced. Koji will find some online design tool for these or do it in LISO. Changing the TF is easy; we can just scale the capacitors. But we also want to make sure that the noise of the AI does not destroy the noise reduction action of the dewhitening board which precedes it.

Jenne should figure out how low the noise needs to be at the input to the coil driver.


P.S. the matlab code which defines these filters

>> [z,p,k] = ellip(4,4,60,2*pi*7570,'s');
>> misc.ai = zpk(z,p,k*10^(4/20)) * zpk([],-2*pi*13e3,2*pi*13e3);
>> % Fudged Anti-Imaging Filter
>> [z,p,k] = ellip(8,0.001,80,2*pi*7570,'s');
>> misc.aa = zpk(z,p,k*10^(0.001/20)) * zpk([],-2*pi*32768,2*pi*32768);

Attachment 1: AAAI.pdf
  3806   Thu Oct 28 04:23:38 2010 ranaUpdateIOOA2L prep

To get the angle to length signal before the c1ioo processor gets going, we need a length signal. We can use either the error signal or the control signal.

I recommend using the control signal since its not puny. The 4-pin LEMO inputs to the OSEM ADC that Suresh has wired are differential so we can, in principle, use either the BNC output of the SERVO plug or the 2-pin LEMO output.

The analog whitening on the OSEM Whitening board should be engaged via the SUS MEDM screen so that we get a good SNR at the A2L dither frequencies.

If the ADC saturates, then we should use a pomona box RC low pass to cut everything off above 100 Hz.

Also, a comment about Yuta's elog: we estimated that the seismic motion was ~1e-7 - 1e-6 meters. The MC linewidth ought to be ~lambda/(2*Finesse) ~ 1e-9.

So, the MC servo as it was was not giving us enough gain (1/f above 50 Hz; UGF ~5-10 kHz) to get the error signal to stay in the linear PDH region. Kevin's filter gave us ~10x more gain at the seismic frequencies (1-3 Hz) of concern.

  13996   Thu Jun 21 14:23:22 2018 Udit KhandelwalSummaryGeneralA summary of the Tip-TIlt Mirror Holder design changes

Here’s a quick summary of the Tip-Tilt Design updates (all files are in the dropbox in [TipTiltSus>TT_New]) that I have been working on with Koji and Steve's help.

1. Plate on top to hold mirror in place:

The plate is 0.5 mm thick. I did a rough FEA with 10 N force on the point of pressure on it, and it bent easily.

2. Weighted screw rod at the bottom for tilting the mirror-holder:

I did a very simplified free body analysis to calculate the required length of the rod to achieve a +/- 15 mRad tilt, and got around 1.5 inches.

3. Set-screws on both side of wire clamp to adjust its horizontal position:

  • Front view (showing set screws on either side of the clamp to push it into the desired position, and the clamp in the middle with screws on top and bottom to fix its position):

  • Exploded view showing protrusion in clamp that sits in the mirror holder inset:


  • Exploded view showing inset in the mirror holder to slide protrusion in:




1. Used the same screw size in most places to reduce complexity.

2. The mirror holder I have worked on is a little different from the actual piece I have on my table. Which one do you prefer (Koji)?

  13997   Thu Jun 21 14:57:59 2018 KojiSummaryGeneralA summary of the Tip-TIlt Mirror Holder design changes

> 2. Weighted screw rod at the bottom for tilting the mirror-holder:

Too long. The design of the holder should be check with the entire assembly.
We should be able to make it compact if we heavier weights.
How are these weights fixed on the shaft?
Also can we have options for smaller weights for the case we don't need such a range?
Note the mass of the weights.

> 3. Set-screws on both side of wire clamp to adjust its horizontal position:

How much is the range of the clamp motion limited by the slot for the side screws and the slot for the protrusion? Are they matched?
Can you show us the design of the slot made on the mirror holder?


Where is the center of mass (CoM) for the entire mirror holder assy and how much is the height gap between the CoM and the wire release points. Can you do this with 3/8" and 1/2" fused silica mirrors?

  1409   Thu Mar 19 02:45:36 2009 YoichiConfigurationIOOA loose wire found for MC1
I found a loose connection of a wire in the cross-connect between an ADC and the MC1 coil driver's UL bias input.
I tightened it.
To see if this fixes the MC1 drift problem, I will do another round of MC1 drift measurement.
You can lock the MC if you need to use the IFO but please note it in the elog.

  1410   Thu Mar 19 10:45:43 2009 YoichiConfigurationIOOA loose wire found for MC1
I attached a 6-hour trend of the MC mirror OSEM signals with the MC unlocked.
The drift of the MC1 is within 20 counts (0.6um in terms of each OSEM).
This is comparable to the other MC mirrors.
Attachment 1: AfterWireFix-1.pdf
  15073   Wed Dec 4 19:54:27 2019 gautamUpdateLSCA look to the past

Trawling through some past elogs, I saw that the ALS noise increase as a function of CARM offset reduction is not really a new thing (see e.g. this elog). In the past, when we were able to lock, when the CARM offset is reduced to zero, the arms would "buzz" through resonance. It just wasn't clear to me how much the buzzing was - in all the plots we presented, we were not looking at the fast 16k output, so it looked like the arm powers had stabilized. But today, looking at the frame data at 16k from back in 2016, it is clear to me that the arm transmission was in fact swinging all the way from 0 to some maximum. Once the IR signal (=REFL11) blending is turned on, we were able to stabilize the arm power somewhat. What this means is that we are in a comparable state as to when we were able to lock in the past (since I'm able to sit at 0 CARM offset with the PRMI locked almost indefinitely).

So, I think what I'll try for the next 3 days is to get this blending going, I think I couldn't enable the CM_slow path because when I was experimenting with the high bandwidth Y arm cavity locking, I had increased the whitening gain of this channel, but REFL11 has much more optical gain (=larger signal) than POY11, and so I'll start from 0dB whitening gain and see if I can turn the magic integrator on. Long term, we should try and compensate the optomechanical plant that changes as our CARM offset gets reduced, as this would further reduce the lock acquisition time and simplify the procedure (no need to fiddle with the integrator, offsets etc). A relevant thread from the past.

Attachment 1: DRFPMI_2016March.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
Attachment 2: 071103_DitherLock_sweep.pdf
Attachment 3: 071103_HiResPZTDither_sweep.png
Attachment 4: 071103_HiResPZTDither_sweep.pdf
Attachment 5: 071103_HiResPZTDither_sweep2.png
Attachment 6: 071103_HiResPZTDither_sweep2.pdf
  4376   Fri Mar 4 03:31:35 2011 kiwamuUpdateGreen LockingA first noise budget

I made a noise budget for the ALS noise measurement that I did a week ago (see #4352).

I am going to post some details about this plot later because I am now too sleepy.


  15562   Mon Sep 7 23:49:14 2020 gautamUpdateBHDA first look at RF44 scheme


Over the last couple of days, I've been working towards getting the infrastructure ready to test out the scheme of sensing (and eventually, controlling) the homodyne phase using the so-called RF44 scheme. More details will be populated, just quick notes for now before I forget.

  • LO beam with RF sidebands needed to be re-coupled into collimator, it wasn't seated tightly and just touching the fiber completely destroyed the alignment.
  • HWP installed before said collimator - IMC wants s-polarized light whereas the IFO field is p-polarized.
  • After my work, the numbers were: ~1.47mW input to collimator, ~1.07mW out of collimator on AS table, ~1mW making it to the BHD board. All seem like reasonable numbers to me.
  • 44 MHz signal synthesis - for now, I use a Marconi (10 MHz synced to Rb clock), I think we could also use a mixer+SLP50 to mix 11 and 55 MHz signals (which are easily available at the LSC rack) to generate this. I looked at Wenzel quadruplers, the specs don't suggest a quadrupler will do much better.
  • CDS model was modified to accept the phase-tracker output as an error signal for the homodyne phase control servo. Compile and install went smooth but I opted against a model restart tonight, I'll do it tmrw.
  • Some trials were done with the Michelson locked to a dark fringe (as was done for the case of the DC LO field beating with the 55 MHz sideband). While the overall spectrum lines up fairly well with earlier trials, the signal looks somewhat more "discontinuous" in its traversal of I/Q space, and it never quite goes to 0. Some offset? What does this mean for locking? More investigations needed....
  15563   Tue Sep 8 01:31:43 2020 KojiUpdateBHDA first look at RF44 scheme

- Loose fiber coupler: Sorry about that. I could not detect something was loose there, although some of the locks were not tightened.

- S incident instead of P: Sorry about that too. I completely missed that the IMC takes S-pol.

  6414   Wed Mar 14 13:16:50 2012 kiwamuUpdateLSCA correction on Noise estimatino in the REFL33Q

A correction on the previous elog about the REFL33Q noise:

 Rana pointed out that the whitening filter's input referred noise should not be such high (I have estimated it to be at 54 nV/sqrtHz).
In fact the measurement was done in a condition where no laser is on the photo diode by closing the mechanical shutter at the PSL table.
Therefore the noise I called "whitening filter input referred noise" includes the voltage noise from the RFPD and it could have such a noise level.
So the noise curve drawn in the plot should be called "whitening filter + RFPD electronics noise".

Quote from #6407

A feasibility study of the REFL33Q as a MICH sensor was coarsely performed from the point view of the noise performance.

  • Whitening filter input referred noise
    • I assumed that it is flat with a level of 54 nV/sqrtHz based on a rough measurement by looking at the spectrum of the LSC input signals.
    • The contribution was estimated by applying some gain corrections from the conversion efficiency of the demod board, transimpedance gain, responsivity and the optical gain.
    • This noise is currently the limiting factor over a frequency range from DC to 1 kHz.


  1286   Mon Feb 9 17:09:51 2009 YoichiUpdateComputersA bunch of updates for the network GPIB stuff.
During the work on ISS, we noticed that netgpibdata.py is very unreliable for SR785.
The problem was caused by flakiness of the "DUMP" command of SR785, which dumps the data from the analyzer to the client.
So I decided to use other GPIB commands to download data from SR785. The new method is a bit slower but much more reliable.

I also rewrote netgpibdata.py and related modules using a new class "netGPIB".
This class is provided by netgpib.py module in the netgpibdata directory. If you use this class for your python program, all technical details and dirty tricks are hidden in the class methods. So you can concentrate on your job.
Since python can also be used interactively, you can use this class for a quick communication with an GPIB instrument.

Here is an example.
>ipython #start interactive python
>>import netgpib #Import the module
>>g=netgpib.netGPIB('teofila',10) #Create a netGPIB object. 'teofila' is the hostname of
#the GPIB-Ethernet converter. 10 is the GPIB address.
>>g.command('ACTD0') #Send a GPIB command "ACTD0". This is an SR785 command meaning "Change active display to 0".
>>ans=g.query('DFMT?') #If you expect a response from the instrument, use query command.
#For SR785, "DFMT?" will return the current display format (0 for single, 1 for dual).
>>g.close() #Close the connection when you are done.

Sometimes, SR785 gets stuck to a weird state and netgpibdata.py may not work properly. I wrote resetSR785.py command to reset it remotely.
Wait for 30sec after you issue this command before doing anything.

I wrote two utility commands to perform measurements with SR785 automatically.
TFSR785.py commands SR785 to perform a transfer function measurement.
SPSR785.py will execute spectrum measurements.
You can control various parameters (bandwidth, resolution, window, etc) with command-line options.
Run those commands with '-h' for help.
It is recommended to use those commands even when you are in front of the analyzer, because they save various measurement parameters (input coupling, units, average number, etc) into a parameter file along with the measured data. Those parameters are useful but recording them for each measurement by hand is a pain.
  15820   Thu Feb 18 20:24:48 2021 KojiSummaryElectronicsA bunch of electronics received

Todd provided us a bunch of electronics. I went to Downs to pick them up this afternoon and checked the contents in the box. Basically, the boxes are pretty comprehensive to produce the following chassis

  • 8 HAM-A coil driver chassis
  • 7 16bit Anti-Aliasing chassis
  • 4 18bit Anti-Imaging chassis
  • 5 16bit Anti-Imaging chassis

Some panels are missing (we cannibalized them for the WFS electronics). Otherwise, it seems that we will be able to assemble these chassis listed.
They have placed inside the lab as seen in the attached photo.

HAM-A COIL DRIVER (Req Qty 28+8)

- 8 Chassis
- 8 Front Panels
- 8 Rear Panels
- 8 HAM-A Driver PCBs
- 8 D1000217 DC Power board
- 8 D1000217 DC Power board

16bit AA (Req Qty 7)
- 6 7 Front Panels (1 missing -> [Ed 2/22/2021] Asked Chub to order -> Received on 3/5/2021)
- 7 Rear Panels
- 28 AA/AI board S2001472-486, 499-511
- 7 D070100 ADC AA I/F
- 7 D1000217 DC Power board

18bit AI (Req Qty 4)
- 4 Front Panels
- 4 Rear Panels
- 8 AA/AI board S2001463-67, 90-92
- 4 D1000551 18bit DAC AI I/F
- 4 D1000217 DC Power board
- bunch of excess components

16bit AI (Req Qty 5)
- 4 5 Front Panels (D1101522) (1 missing -> [Ed 2/22/2021] Asked Chub to order -> Received on 3/5/2021)
- 3 5 Rear Panels (D0902784) (2 missing -> [Ed 2/22/2021] Asked Chub to order -> Received on 3/5/2021)
- 10 AA/AI board S2001468-71, 93-98
- 5 D1000217 DC Power board
- 5 D070101 DAC AI I/F

Internal Wiring Kit

[Ed 2/22/2021]
Asked Chub to order:
- Qty 12 1U Hamilton Chassis
- Qty 5 x Front/Rear Panels/Internal PCBs for D1002593 BIO I/F (The parts and connectors to be ordered separately)

  -> Front/Rear Panels received (3/5/2021)
  -> PCBs (unpopulated) received (3/5/2021)
  -> Components ordered by KA (3/7/2021)

Attachment 1: IMG_0416.jpeg
  15828   Sat Feb 20 10:01:48 2021 gautamSummaryElectronicsA bunch of electronics received

Will we also be receiving the additional 34 Satellite Amplifier PCBs?

  15830   Sat Feb 20 16:46:17 2021 KojiSummaryElectronicsA bunch of electronics received

We received currently available sets. We are supposed to receive more coil drivers and sat amps, etc. But they are not ready yet.


  15866   Fri Mar 5 00:53:09 2021 KojiSummaryElectronicsA bunch of electronics received

Received additional front/rear panels. Updated the original entry and Wiki [Link]


  15868   Fri Mar 5 15:03:28 2021 gautamSummaryElectronicsA bunch of electronics received

The PCBs for the D1002593 BIO I/F (5pcs ea of D1001050 and D1001266) were received (from JLCPCB) today. idk what the status of the parts (digikey?) is.


Received additional front/rear panels. Updated the original entry and Wiki [Link]

  15870   Fri Mar 5 15:32:53 2021 KojiSummaryElectronicsA bunch of electronics received

The parts will be ordered by Koji The components for the additional BIO I/F have been ordered.

  15981   Wed Mar 31 03:56:37 2021 KojiSummaryElectronicsA bunch of electronics received

We have received 9x 18bit DAC adapter boards (D1000654)

Attachment 1: P_20210331_013257.jpg
Attachment 2: P_20210331_014020.jpg
  10038   Fri Jun 13 19:09:44 2014 KojiUpdateIOOA blown fuse found on the euro card crate at 1X2 (IOO) rack.

[Rana Zach Koji]

We tracked down the MC locking issue to be associated with the power supply problem.
Replacing a fuse which had incomplete connection with the new one, the MC started locking.

We still have the MC autolocker not running correctly. This is solely a software problem.

We went down to the IOO electronics rack to investigate the electronics there. After spending
some time to poking around the test points of the MC servo board, we noticed that the -24V
power indicator on the MC demodulator module was not lit. In fact, Steve mentioned on Wednesday
that the -24V Sorensen supply had lower current than nominal. This actually was a good catch
but should have been written in the ELOG!!!

We traced the power supply wires for the crate and found one of the three -24V supply has no
voltage on it. Inspection of the corresponding fuse revealed that it had a peculiar failure mode.
The blown LED was not lit. The connection was not reliable and the -24V power supply was flickering.

We then replaced the fuse.This simply solved all of the issues on the MC servo board. The electronics
should be throughly inspected if it still has the nominal performance or not, as the boards were exposed
to the single supply more than a week. But we decided to try locking ability first of all.

Yes, we now can lock the MC as usual.

Now the newly revealed issue is MC autolocker. It was running on op340m but op340m does not want to run it now.
It should be closely investigated.

Also turning on WFS unlocks the MC. Currently the WFS outputs are turned off.
We need usual align MC / check spot position / adjust WFS QPD spots combo.

ELOG V3.1.3-