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ID Date Author Typeup Category Subject
  17383   Wed Jan 4 08:52:11 2023 JCUpdateOPLEV TablesETMX laser has died

Koji mentioned to me that this laser has a degraded output. I removed this replacement laser and put in a new laser from the Y Arm Cabinets, Attachment #1. I placed the degraded laser back to its visitor setup and tested with the power supply, this is shown in Attachment #2. Along with this, I also labeled this laser as degraded.

  17388   Mon Jan 9 19:41:01 2023 AnchalUpdateSUSNull stream (butterfly/pringle) row added and DQed

I updated the suspension model (/cvs/cds/rtcds/userapps/trunk/sus/c1/models/lib/sus_single_control_new.dml) to add a 5th row in the input matrix so that we can put in the calculated NULL stream vector (also have been called as Butterfly mode or Pringle mode in the past). The output of this row would go through a filter module and then is sent to the testpoint named 'C1:SUS-OPT_SENSOR_NULL' where OPT is the optic acronym. This channel is acquired in frames at 256 Hz and would be available as C1:SUS-OPT_SENSOR_NULL_DQ. After the update in the model, I built, installed and restarted models c1sus, c1mcs, c1scx, c1scy, c1su2, and c1su3. Then I restarted daqd, and everything came up nicely. After but restore, I added the null stream vector for the optics it was already known from a free swing test. ITMX, ITMY, ETMX, PRM, and SRM null stream vectors needs to be calculated from the other 4 rows. It is set to zero right now. Medm screen for the input matrix was also updated to allow seeing this row.


  17389   Tue Jan 10 15:07:33 2023 JCUpdateGeneralClean Large Optical Table

I have been working on cleaning the large optical table next to the PSL table. I have placed the known optics along in the optical cabinets Section Y5. Post and pillars have been placed in a cabinet along X-Arm. (I will work on gathering optics and optical hardware into a single area in the future, having them separated is only temporary.) I found some optics that were chipped and/or unlabeled. These have been placed in a box. 

There were cables coming into this table from the wire rack above, I plan on removing this. If there are any issues with me doing this, please message me. 

My main purpose for cleaning this is to potentially have an open area to place OMC for the next vent. We can also move the PD Testing table here. 

  17391   Tue Jan 10 20:24:29 2023 AnchalUpdateASCWFS demodulation board 111B - Working as expected

I've completed the modifications on two WFS demod boards. This required replacing all 8 mixer ICs on each board. I also tuned each channel to get less than 2 mV offset on all of them.

I was able to complete testing the board SNo. 111B today. The results are attached. The test was done by feeding the board 22 MHz LO generated by frequency doubling. A signal at 11 MHz was generated using Moku:Lab at 1mVpp and then further attenuated by 10 dB to make a fair comparison with the previous testing of the IMC WFS board at 29.5 MHz. This board has the same response as the IMC WFS board at 29.5 MHz. I tested all four channels in the second plot.

I'll complete the testing of the second board SNo 112 B and then move on to setting up the optical path for AS WFS.

  17393   Wed Jan 11 17:05:55 2023 AnchalUpdateASCWFS demodulation board 112B - Working as expected

The other modified board 112B has been fixed and tested now. See the results attached. The issue was in some malfunctioning OP284 which have been replaced by AD8672.

  17394   Thu Jan 12 10:06:10 2023 PacoUpdateALSDFD discriminant calibration

[Paco, Anchal] Log from yesterday work around 1Y2 rack; note that while this work was ongoing, TT2 position drifted slowly and misaligned the IFO input over the course of less than an hour. I suspect the DB9 breakout board and temporarily present components noted below may have introduced a floating ground in 1Y2, making the TT coil drivers misbehave. To support this claim, we noted that after removing the breakout board the drift disappeared!

We calibrated the DFD discriminant as a function of RF input level. The configuration was as follows:

  1. Break out IQ demod board RF output (in the rear chassis on 1Y2), looking at Ch1 board outputs (for BEATX). The two differential outputs were broken into two BNCs (pairs 1,6 and 2,7 for Q and I respectively), and fed into the Moku:Lab. A Marconi 2023A was used as a VCO, with FM ext mode enabled and a FreqDVN (modulation slope) of 200 kHZ / Vrms (1 Vrms = 1.41 Vp = 0.705 Vpp). The FM ext input on the Marconi was sourced by the OUT1 of Moku:Lab, and the IQ demod outputs were connected to IN1 and IN2 on Moku:Lab.
  2. After measuring the TF using a swept sine, I verified that the frequency response was flat up to 150 kHz (Marconi cuts FM ext at 275 kHz), so I switched to the oscilloscope instrument and setup OUTPUT to a 211.1 Hz sine wave, 1.41 Vpp to dither the 40 MHz by +- 100 kHz.
  3. Using the arbitrary math function in Moku:Lab Scope, I computed the DFD output magnitude = sqrt(I**2 + Q**2), and measured its mean over 3 seconds.

The results are summarized in Attachment #1.

  17396   Thu Jan 12 15:31:27 2023 RadhikaUpdateALSXARM green laser lock debugging

[Radhika, Anchal, Paco]

AUX PDH Loop Stability

Today I tried aligning the XEND green beam into the arm cavity. Using M1 and M2 steering mirrors, I reached a max transmission ~1.2 of TEM00. In this configuration there was a "donut" mode also flashing, with transmission exceeding that of TEM00. Scanning all 4 degrees of freedom, I couldn't get TEM00 transmission to exceed 1.2, or significantly suppress the other modes. Not great mode matching. (PD gain: 20 dB; servo gain: 10.0.) 

In an earlier conversation Paco had recommended I preamplify the green REFL signal with an SR560 before feeding it to the RF mixer. (For yarm this is done with an SR560 gain of 1000.) I did so and raised the gain on the SR560 until it overloaded (PD: 0 dB; SR560: 100). This didn't immediately improve the lock quality, but because alignment still needed work I wasn't surprised. 

Anchal suggested the laser mode might be distorted by some lenses further upstream. We noticed some vertical spreading/distortion of the green beam by the first lens after SHG. I adjusted the pitch of an IR steering mirror until it disappeared. We then used the irises by the entrance to the arm cavity to coarsely align the input beam with M1 and M2. This time, fine alignment brought green transmission to just under 4. After slightly adjusting the half-wave plate, green transmission peaked at 4. (This is the highest I've seen it - previous max was 3.) The final combination of PD gain, SR560 gain, and servo gain that maximized transmission and duration of lock was (PD: 10 dB; SR560: 20; servo: 4.0). At its longest, lock on TEM00 was maintained for ~10 seconds.


In parallel with above, I was trying to take an OLTF of the loop whenever it was temporarily locked. I set up the measurement configuration like in the previous ELOG (injection at error point). Like last time, the loop would not lock when summing the PDH error signal with the excitation. I confirmed this was true even when I turned off the Moku excitation output. Checking the summed signal output, the Moku was adding an offset to the error signal. Buffering the excitation with an SR560 solved this issue.

The locked mode was switching pretty rapidly during the time I tried to measure the OLTF, and I ended up moving onto trying to improve lock. I might return today to try to take a measurement - I'll post it here.

  17397   Thu Jan 12 18:51:17 2023 PacoUpdateALSDFD and Phase tracker AM coupling

[Anchal, Paco]

We measured DFD AM coupling; it seems to be minimum at higher RF input and low modulation depths as expected.

To do this, we set up Moku:Lab for AM ext with a spare DAC channel (C1:BAC-SPARE_CH14_OUT) which we send a swept sine excitation using diaggui. We vary the carrier level, and the modulation depth (every time we changed the level, we run the phaseUGF.py script to allow the phase tracker to adjust its loop gain properly). Attachment #1 shows the results, showing the finite bandwidth effect of the phase tracker as well as the mean magnitudes of the AM coupling below 100 Hz. This measurement and the script live in


What this means for ALS calibration:

It seems the residual AM coupling for a typical RF input level from our ALS beatnote corresponds to the couplings of ~ 2 Hz/V. This means that if the RF input level is fluctuating by 100mV, our residual beat frequency fluctuations only move by 200 mHz. This is not the case when the arms are locked... there the beat level stability is closer to 1 mV (so 2 mHz coupling to the phase tracker). Under previous SNR conditions, our lines are typically at a few 100 Hz of amplitude, with a noise floor comparable to a few 100 mHz (SNR ~ 100s), so AM coupling seems not to be statistically limiting for 0.1% calibration.


  • To further reject this residual coupling, it may be worth balancing the demodulated IQ amplitudes, by using the digital gains "C1:ALS-BEATX_FINE_Q_GAIN, C1:ALS-BEATX_FINE_I_GAIN".
  • For now, this effect (and its frequency dependence above 300 Hz) can probably be neglected for ALS calibration purposes.
  17406   Thu Jan 19 20:35:54 2023 AnchalUpdateASCInstalled 2 flipper mirrors for handingl MC reflection beam to camera

Today I installed two flipper mirrors M3 and M4 (see attached photo) to create alternate route for MC reflection camera beam. Both these mirrors are Y1-1037-45S. In nominal operation where IMC is using the WFS, we will keep M3 upright and M4 flipped down. When using WFS for AS, M3 will be flipper down and M4 will be upright to save the camera from the high intensity MC reflection beam.

Note that everytime M3 is flipper and put back upright, the alignment into WFS would need to be tuned as the flipper apparatus does not come back to same alignment everytime. I centered the beams on the WFS heads today and zeroed RF offsets usingC1IOO_WFS_MASTER>!Actions>Correct WFS RF Offsets script. After this, the IMC WFS loops are working as expected atleast for last 15 minutes that I have monitored them. Hopefully, this will remain consistent.

Upcoming work:

  • Change the steering mirror that steers the beam to black hole to be a flipper mirror too as AS beam strength (measured when MICH was locked to bright port) is 0.3 mW and IMC WFS heads combined power is 0.5 mW in nominal operation, so we can not afford to dump any AS beam light.
  • Put flipper mirror M1 and fixed mirror M2 mentioned in 40m/17320 for steering AS beam to IMC WFS heads.
  17407   Fri Jan 20 20:13:20 2023 AnchalUpdateASCInstalled 2 flipper mirrors for handingl MC reflection beam to camera

After discussions with Yuta, I figured that a better optical layout is possible which does not interfere with the existing IMC WFS path at all. So I reset the IMC WFS path today (and zeroed RF offsets again) and changed the MC reflection camera and MC reflection beam dump (black hole) position to create space for a flipper mirror that will pop up in the IMC WFS path and steer in the AS beam. New proposed path is shown in the photo in cyan. Red is MC reflection beam, yellow is IFO reflection beam and orange is teh AS beam that we will pick up using flipper mirror M1. Note that I found an intense 6.4 mW ghost beam coming out of the interferometer in between IFO refl and MC refl beams. This beam is shown in pink which I have dumped now. This beam was earlier not dumped. We will need to investigate more on the source of this beam and correct it in the next vent.

  17408   Sat Jan 21 15:32:40 2023 AnchalUpdateASCAS WFS path nominally set

I've completed the beam redirection path for AS beam to WFS heads in a nominal way. By that I mean that all mirrors (M1, M2, M3, and M4) are now in their final positions and we will need to install one or two lenses to collimate the beam to match the mode that the WFS path is expecting as it has it's on the focusing lens before the photodiodes. For this last part, I think the fasted way would be to profile the beam and calculate the correct lens and position rather than trial and error as the beam intensity is very low for estimating the beam size by eye.

IMC WFS state: Flip M1 and M2 down.

AS WFS state: Flip M1 and M2 up.

  17409   Sat Jan 21 18:01:06 2023 AnchalUpdateALSDFD and Phase tracker AM coupling

I took transfer function measurement of DFD AM coupling using noise excitation.

Noise excitation setup

Noise is injected using C1:BAC-SPARE_CH14_EXC using awggui which is filtered by a foton filter to simulate the real beatnote RF amplitude noise measured by taking quadrature sum of C1:ALS-BEATY_FINE_I_OUT and C1:ALS-BEATY_FINE_Q_OUT. See attachment 1.

The DAC output is connected to MP1 at CH1. MP1 is set to run in waveform generation mode with following settings:


  • Carrier frequency: 45 MHz
  • Carrier Level: 500 mVpp
  • No offset or phase offset
  • Amplitude modulation ON
    • Modulation slope: 100%/V
    • Source Input: Ch1

The AWGUI is set to excite C1:BAC-SPARE_CH14_EXC using settings mentioned in attachment 2.

With this setup, the RF amplitude noise is simulated with MP1 and DAC excitation.

Transfer function measurement

With AWGGUI running as mentioned above, I simply used diaggui in spectrum mode for channels C1:BAC-SPARE_CH14_EXC and C1:ALS-BEATY_FINE_PHASE_OUT_HZ. The second channel is already calibrated into Hz, and the first channel is in counts. To convert it into voltage of amplitude fluctuation, I first converted DAC excitation to voltage by assuming 16 bit DAC with +/- 10 V range, this gives conversion constant of 10/2**15 V/cts. Then since MP1 is doing 100%/V AM modulation, for 500 mVpp RF level, this means 0.25 V/V AM modulation. Multiplying these two together gives, 7.6294e-5 V/cts. I put this number in teh diaggui calibration for C1:ALS-BEATY_FINE_PHASE_OUT_HZ.

This created the transfer function measurement attached in attachment 3.

The measurement resulted in roughly 2kHz/V AM to frequency coupling in DFD + phase tracker setup. The previous measurement with coherent sinusoidal excitation was exactly a factor of 1000 less than this, so I believe I might have made some error in calibrating or there could be an error in the previous elog. Please check my calculations. But a solid thing to note is the coherence measured below 1Hz. I'll do more sophisticated analysis on weekdays.

I also think that coherence was low because of low excitation. We should redo this test with more noise power to get good coherence in all frequency band to have good idea of what would happen to ebatnote RF amplitude noise at all frequencies.

Mon Jan 23 11:47:23 2023 Adding Attachment 4:

I realised that with the noise excitation setup set to mimic real beatnote amplitude noise with very low frequency noise as it is seeded with Moku:Pro, the measured frequency noise by the DFD+Phase Tracker setup at C1:ALS-BEATY_FINE_PHASE_OUT_HZ is an indicator of how much RF amplitude noise of beatnote contribute to the frequency noise measured by DFD+Phase tracker. Attachment 4 is the spectrum measured during this measurement.

  17411   Mon Jan 23 16:31:23 2023 ranaUpdateALSDFD and Phase tracker AM coupling

Both the TF measurement and the noise measurements are useful, but the nosie measurement is much more meaningful. Since we expect the main coupling to be incoherent, what we really want is a noise budget style measurement:

  1. Measure the FM noise spectrum with only a single sine wave into the Moku.
  2. Same as #1, but with the AM noise added as you already did.
  3. Estimate the noise budget contribution by doing PSD subtraction, and then scale that by the excitation magntiude. This will be the contribution of beat amplitude noise to the measured calibration.

I took transfer function measurement of DFD AM coupling using noise excitation.

  17412   Mon Jan 23 20:50:58 2023 AnchalUpdateASCAS WFS path beam profiled

I measured the expected beam profile by WFS photodiodes by measuring the beam when mode cleaner was unlocked from the point where beam is picked for WFS. See attachment 1 for beam details. z=0 is the point in the path where AS beam will merge.

For measuring the beam profile of AS beam, I had to focus it using a lens. I picked up a 360.6 mm ROC lens and placed it at z=-67 inch point. Then I profiled the beam at some comfortable section of the path and fitted it. with reverse z-axis. Using this method, I can place the lens back and obtain the original beam back. Attachment 2 shows this fitting process and identification of the original beam profiles. I plotted the AS beam profiles again in attachment 3 and saved them for seeding mode matching effort later. Note that we don't want to be super accurate here, so I did not do any error analysis, just wanted to finish this fast. Also pardon me for the bad quality plots, I did not want to learn Matlab plotting to make it beautiful.

Note: There is significant astigmatism in both IMC reflection beam and AS beam. This could be due to beam going through far off-center on lens. Something to keep in mind, again this measurement is not ideal in terms of precision but this large an astigmatism could not be due to measurement error.


  • Identify correct len(s) and their positions
  • Align the AS beam to WFS heads
  • Test the full signal chain.
  17416   Tue Jan 24 21:04:59 2023 AnchalUpdateASCAS WFS path beam profiled

I completed the mode matching calculation today and found good solution with 360.6 mm ROC PLCX lens at -1.2 m from z=0 point. I placed the lens there today and aligned all mirrors to get centered beam on both WFS PDs when the flipper mirrors are flipper up. This alignment would probably require tweaking everying we flip the mirrors as the flipper mirrors do not come back to same position usually.

I mounted the modified WFS boards 111B and 112B next to the whitening filter boards of existing WFS. Now to switch over, onewould need to transfer the 8 RF lemo cables and the 2 IDE ribbon cables.

I'm working on rtcds model to read AS WFS data and handle it separately. I'll keep a WPICS binaruy switch to switch between IMC WFS or AS WFS. I need to figure out some build issues on this work still.


  17418   Wed Jan 25 10:02:47 2023 yehonathanUpdate Earthquake, MC3 watchdog tripped

We came this morning and noticed the FSS_FAST channel was moving very rapidly. Short inspection showed that MC3 watchdog got tripped. After reenabling the watchdog the issue was fixed and the MC is stable again.

There is a spike in the seismometers 8 hours ago and it was probably due to the 4.2 magnitude earthquake that happened in Malibu beach around that time.

  17420   Wed Jan 25 12:49:14 2023 RadhikaUpdateALSXARM green laser lock debugging

I returned the half-wave plates on the XEND table back to their original angles, and restored the loop configuration with the PDH servo box. I returned the PD gain to 40 dB (original setting), and set the servo gain knob to 6. This was the region of highest loop stability, with the lock holding for a few seconds (as before). The control signal on the scope did not look intuitive - the peaks of the control signal corresponded with zero crossings of the error signal. 

Paco encouraged me to retake transfer function measurements of the PDH servo box. The main takeaway is the PDH servo (boost on) has the expected frequency response at a gain setting of 3 or under, up to 100 mVpp of input. Attachment 1 shows the frequency response at a servo gain of 2, for varying input amplitudes. 

The rest of the bode plots correspond to servo gain of 4, 6, 8, and 10 (boost on). The saturation LED would turn on above a gain value of ~3.25, so these results can't be analyzed or interpreted. But it does seem like a steep, low-frequency jump is a signature of the saturated servo. This jump doesn't appear with 10 mVpp input, at least at or above 1 Hz. 

  17422   Wed Jan 25 16:58:19 2023 AlexUpdateCamerasRecording CCD cameras

Thus far, the software needed for the Magewell video encoder has been successfully installed on Donatella. OBS studio has also been installed and works correctly. OBS will be the video recording software that can be interfaced via command line once the SDI video encoder starts working. (https://github.com/muesli/obs-cli)

So far, the camera can not be connected to the Magewell encoder. The encoder continues to have a pulsing error light that indicates "no signal" or "signal not locked". I have begun testing on a secondary camera, directly connected to the Magewell encoder with similar errors. This may be able to be resolved once more information about the camera and its specifications/resolution is uncovered. At this time I have not found any details on the LCL-902K by Watec that was given to me by Koji. I will begin looking into the model used in the 40 meter next.

  17424   Thu Jan 26 00:18:54 2023 KojiUpdateCamerasRecording CCD cameras

Connect any video signal supported by the adapter. Use Windows / Mac or any other OS. If it keeps complaining, contact Magwell support.

  17425   Thu Jan 26 15:56:30 2023 AnchalUpdateASC1X1 -5V sorenson tripped

[Yuta, Anchal]


I mounted the modified WFS boards 111B and 112B next to the whitening filter boards of existing WFS.

The mounting of two additional WFS demodulation boards drew too much current on -5V rail which tripped the sorenson on 1X1. This was undetected until today. Because of this, the existing WFS boards were not working either. After investicgation to beam paths and PD to board signal chain, we found out this issue. We raised the current limit on -5V supply and it came back to 5V. This brought back functioning of the exisitng WFS boards as well. We increased the current limit slightly on +5V supply too as these boards take a lot of current on +/5 V rails. But we should do this more properly by knowing what current limit the supply is set to. We'll do this part in near future after reading the manuals/wiki.
IMC WFS loops are now working.

ELOG V3.1.3-