40m QIL Cryo_Lab CTN SUS_Lab TCS_Lab OMC_Lab CRIME_Lab FEA ENG_Labs OptContFac Mariner WBEEShop
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ID Date Author Typeup Category Subject
  17143   Mon Sep 19 17:02:57 2022 PacoSummaryGeneralPower Outage 220916 -- restored all

Restore lab

[Paco, Tega, JC, Yehonathan]

We followed the instructions here. There were no major issues, apart from the fb1 ntp server sync taking long time after rebooting once.


ETMY damping

[Yehonathan, Paco]

We noticed that ETMY had to much RMS motion when the OpLevs were off. We played with it a bit and noticed two things: Cheby4 filter was on for SUS_POS and the limiter on ULCOIL was on at 0 limit. We turned both off.

We did some damping test and observed that the PIT and YAW motion were overdamped. We tune the gain of the filters in the following way:

SUSSIDE_GAIN 1250->50

SUSPOS_GAIN 200->150

SUSYAW_GAIN 60->30

These action seem to make things better.

  17145   Tue Sep 20 07:03:04 2022 PacoSummaryGeneralPower Outage 220916 -- restored all

[JC, Tega, Paco ]

I would like to mention that during the Vacuum startup, after the AUX pump was turned on, Tega and I were walking away while the pressure decreases. While we were, valves opened on their own. Nobody was near the VAC Desktop during this. I asked Koji if this may be an automatic startup, but he said the valves shouldn't open unless they are explicitely told to do so. Has anyone encountered this before?

Quote:

Restore lab

[Paco, Tega, JC, Yehonathan]

We followed the instructions here. There were no major issues, apart from the fb1 ntp server sync taking long time after rebooting once.


ETMY damping

[Yehonathan, Paco]

We noticed that ETMY had to much RMS motion when the OpLevs were off. We played with it a bit and noticed two things: Cheby4 filter was on for SUS_POS and the limiter on ULCOIL was on at 0 limit. We turned both off.

We did some damping test and observed that the PIT and YAW motion were overdamped. We tune the gain of the filters in the following way:

SUSSIDE_GAIN 1250->50

SUSPOS_GAIN 200->150

SUSYAW_GAIN 60->30

These action seem to make things better.

 

  17147   Tue Sep 20 18:18:07 2022 AnchalSummarySUSETMX, ETMY damping loop gain tuning

[Paco, Anchal]

We performed local damping loop tuning for ETMs today to ensure all damping loops' OLTF has a Q of 3-5. To do so, we applied a step on C1:SUS-ETMX/Y_POS/PIT/YAW_OFFSET, and looked for oscillations in the error point of damping loops (C1:SUS-EMTX/Y_SUSPOS/PIT/YAW_IN1) and increased or decreased gains until we saw 3-5 oscillations before the error signal stabilizes to a new value. For side loop, we applied offset at C1:SUS-ETMX/Y_SDCOIL_OFFSET and looked at C1:SUS-ETMX/Y_SUSSIDE_IN1. Following are the changes in damping gains:

C1:SUS-ETMX_SUSPOS_GAIN : 61.939   ->   61.939
C1:SUS-ETMX_SUSPIT_GAIN :   4.129     ->   4.129
C1:SUS-ETMX_SUSYAW_GAIN : 2.065     ->   7.0
C1:SUS-ETMX_SUSSIDE_GAIN : 37.953  ->   50

C1:SUS-ETMY_SUSPOS_GAIN : 150.0     ->   41.0
C1:SUS-ETMY_SUSPIT_GAIN :   30.0       ->   6.0
C1:SUS-ETMY_SUSYAW_GAIN : 30.0       ->   6.0
C1:SUS-ETMY_SUSSIDE_GAIN : 50.0      ->   300.0

 

  17176   Thu Oct 6 18:50:57 2022 AnchalSummaryBHDBH55 meas diff angle estimation and LO phase lock attempts

[Yuta, Paco, Anchal]

BH55 meas diff

We estimated meas diff angle for BH55 today by following this elog post. We used moku:lab Moku01 to send a 55 MHz tone to PD input port of BH55 demodulation board. Then we looked at I_ERR and Q_ERR signals. We balanced the gain on I channel to 1.16 to get the two signals to same peak to peak heights. Then we changed the mead diff angle to 91.97 to make the "bounding box" zero. Our understanding is that we just want the ellipse to be along x-axis.

We also aligned beam input to BH55 bit better. We used the single bounce beam from aligned ITMY as the reference.


LO phase lock with single RF demodulation

We attempted to lock LO phase with just using BH55 demodulated output.

Configuration:

  • ITMX, ETMs were significantly misaligned.
  • At BH port, overlapping beams are single bounce back from ITMY and LO beam.

We expected that we would be able to lock to 90 degree LO phase just like DC locking. But now we understand that we can't beat the light with it's own phase modulated sidebands.

The confusion happened because it would work with Michelson at the dark port output of michelson, amplitude modulation is generated at 55 MHz. We tried to do the same thing as was done for DC locking with single bounce  and then michelson, but we should have seen this beforehand. Lesson: Always write down expectation before attempting the lock.

 

  17201   Thu Oct 20 14:13:42 2022 yutaSummaryPSLPMC and IMC sideband frequencies measured

I measured the sideband frequencies for PMC and IMC lock (to use it for Mariner PMC and IMC design).

PMC: 35.498912(2) MHz
IMC: 29.485038(2) MHz

Details:
 - Mini-Circuits UFC-6000 was used. The spec sheet says the frequency accuracy in 1-40 MHz is +/- 2 Hz.
 - "29.5 MHz OUT" port of 40m Frequency Generation Unit (LIGO-T1000461) was connected to UFC-6000 to measure IMC sideband frequency.
 - "LO TO SERVO" port of Crystal Frequency Ref (LIGO-D980353) was connected to UFC-6000 to measure PMC sideband frequency.
 - It seems like IMC sideband frequency changed from 29.485 MHz to 29.491 MHz back in 2011 (40m/4621). We are back to 29.485 MHz. I'm not sure what happened after this.

Attachment 1: IMC.JPG
IMC.JPG
Attachment 2: PMC.JPG
PMC.JPG
  17203   Fri Oct 21 10:37:36 2022 AnchalSummaryBHDBH55 phase locking efforts

After the amplifier was modified with a capacitor, we continued trying to approach locking LO phase to in quadrature with AS beam. Following is a short summary of the efforts:

  • To establish some ground, we tested locking MICH using BH55_Q instead of AS55_Q. After amplification, BH55_Q is almost the same level in signal as AS55_Q and a robust lock was possible.
  • Then we locked the LO phase using BH55_Q (single RF sideband locking), which locks the homodyne phase angle to 90 degrees. We were able to successfully do this by turning on extra boost at FM2 and FM3 along with FM4 and FM5 that were used to catch lock.
  • We also tried locking in a single ITMY bounce configuration. This is a Mach-Zehnder interferometer with PR2 acting as the first beam splitter and BHDBS as the recombination beamsplitter. Note that we failed earlier at this attempt due to the busted demodulation board. This lock worked as well with single RF demodulation using BH55_Q.
  • The UGF achieved in the above configurations was ~15 Hz.
  • In between and after the above steps, we tried using audio dither + RF sideband, and double demodulation to lock the LO phase but it did not work:
    • We could see a good Audio dither signal at 142.7 Hz on the BH55_Q signal. SNR above 20 was seen.
    • However, on demodulating this signal and transferring all signal to C1:HPC-BH55_Q_DEMOD_I_OUT, we were unable to lock the LO phase.
    • Using xyplot tool, we tried to see the relationship between C1:HPC-BHDC_DIFF_OUT and C1:HPC-BH55_Q_DEMOD_I_OUT. The two signals, according to our theory, should be 90 degrees out of phase and should form an ellipse on XY plot. But what we saw was basically no correlation between the two.
    • Later, I tried one more thing. The comb60 filter on BH55 is not required when using audio dither with it, so I switched it off.
      • I turned off comb60 filters on both BH55_I and BH55_Q filter modules.
      • I set the audio dither to 120 Hz this time to utilize the entire 120 Hz region between 60 Hz and 180 Hz power line peaks.
      • I changed the demodulation low pass filter to 60 Hz Butterworth filter. I tried using 2nd order to lose less phase due to this filter.
      • These steps did not fetch me any different results than before, but I did not get a good time to investigate this further as we moved into CDS upgrade activities.
  17204   Fri Oct 21 16:15:10 2022 yutaSummaryBHDLO phase locking with BH55 audio dither trials

[Paco, Yuta]

We are still struggling with locking LO phase in MICH or ITM single bounce with BH55 with audio dither.
Without audio dither, BH55 can be used to lock.

What works:
 - LO phase locking with ITMX single bounce, using BH55_Q
  - BH55_Q configuration: 45 dB whitening gain, with whitening filter on.
  - C1:LSC-BH55_PHASE_R=147.621 deg gives most signal in BH55_Q.
  - LO phase can be locked using BH55_Q, C1:HPC-LO_PHASE_GAIN=-0.5 (bright fringe for A, dark for B), feeding back to LO1 gives UGF of ~80Hz (funny structure in ~20 Hz region; see Attachment #1)

 - LO phase locking with ITMX single bounce, using BHDC_DIFF
  - BHDC B/A = 1.57 (gain balanced with C1:HPC-IN_MTRX)
  - LO phase can be locked using BHDC_DIFF, C1:HPC-LO_PHASE_GAIN=-0.4 (mid-fringe lock), feeding back to LO1 gives UGF of ~50 Hz (see Attachment #2).

 - LO phase locking with MICH locked with AS55_Q, using BH55_Q
  - AS55_Q configuration: 24 dB whitening gain, with whitening filter off
  - C1:LSC-AS55_PHASE_R=-150 deg gives most signal in AS55_Q
  - MICH can be locked using AS55_Q, C1:LSC-MICH_GAIN=-10, C1:LSC-MICH_OFFSET=30 (slightly off from AS dark fringe), feeding back to 0.5*BS gives UGF of ~100Hz (see Attachment #3)
  - LO phase can be locked using BH55_Q, C1:HPC-LO_PHASE_GAIN=-0.8 (bright fringe for A, dark for B), feeding back to LO1 gives UGF of ~45Hz (see Attachment #4)

 - LO phase locking with MICH locked with AS55_Q, using BHDC_DIFF
  - LO phase can be locked using BHDC_DIFF, C1:HPC-LO_PHASE_GAIN=1 (mid-fringe lock), feeding back to LO1. Not a very stable lock.

What does not work:
 - LO phase locking using BH55_Q demodulated at LO1 (or AS1) dither frequency, neither in ITMX sigle bounce or MICH locked with/without offset using AS55_Q
  - C1:HPC-AS1_POS_OSC_FREQ=142.7 Hz, C1:HPC-AS1_POS_OSC_CLKGAIN=3000, C1:HPC-BH55_Q_AS1_DEMOD_PHASE=-15 deg, BLP30 is used.
  - Attachment #5 shows error signals when LO phase is locked with BH55_Q. BHDC_DIFF and BH55_Q_AS1_DEMOD_I having some coherence is a good indication, but we cannot lock LO phase with BH55_Q_AS1_DEMOD_I yet.
  - Also, injection at 13.14 Hz with an amplitude of 300 for AS1 can be seen in both BH55_Q and BH55_Q_AS1_DEMOD_I (26 Hz peak for BHDC_DIFF, as it is quadratic, as expected), which means that BH55_Q_AS1_DEMOD_I is seeing something.

Next:
 - Check actuation TFs for LO1, LO2, AS1 too see if there are any funny structures at ~ 20 Hz.
 - LO phase locking might require at least ~50 Hz of UGF. Use higher audio dither frequency so that we can increase the control bandwidth.
 - Check analog filtering situation for BHDC_A and BHDC_B signals (they go minus when fringes are moving fast)

Attachment 1: Screenshot_2022-10-21_15-33-18_LO_OLTF_LO1_BH55_Q.png
Screenshot_2022-10-21_15-33-18_LO_OLTF_LO1_BH55_Q.png
Attachment 2: Screenshot_2022-10-21_15-42-50_LO_OLTF_LO1_BHDCDIFF.png
Screenshot_2022-10-21_15-42-50_LO_OLTF_LO1_BHDCDIFF.png
Attachment 3: Screenshot_2022-10-21_15-44-53_MICH_OLTF.png
Screenshot_2022-10-21_15-44-53_MICH_OLTF.png
Attachment 4: Screenshot_2022-10-21_15-50-43_LO_OLTF_LO1_BH55_Q_MICH.png
Screenshot_2022-10-21_15-50-43_LO_OLTF_LO1_BH55_Q_MICH.png
Attachment 5: Screenshot_2022-10-21_16-11-16.png
Screenshot_2022-10-21_16-11-16.png
  17205   Sat Oct 22 21:36:28 2022 ranaSummaryBHDBH55 phase locking efforts

give us an animated GIF of this cool new tool! - I'm curious what happens if you look at 2 DoF of the same suspension. Also would be cool to apply a bandpass filter before plotting XY, so that you could look for correlations at higher frequencies, not just seismic noise

Quote:
 

Using xyplot tool, we tried to see the relationship between C1:HPC-BHDC_DIFF_OUT and C1:HPC-BH55_Q_DEMOD_I_OUT. The two signals, according to our theory, should be 90 degrees out of phase and should form an ellipse on XY plot. But what we saw was basically no correlation between the two.

 
  17206   Mon Oct 24 18:01:00 2022 PacoSummaryBHDBHD actuation measurements

[Yuta, Paco]

Today we calibrated the actuation on BHD suspended optics: LO1, LO2, AS1, AS4.
Actuation transfer functions for these optics look good.


ITMY actuation

For a reference we locked LO-ITMY single bounce using the LSC MICH loop. The error point was BH55_Q, the whitening filter gain was 45 dB, IQ demod rotation angle = 151.061 deg, the servo gain was -10, and the actuation point was ITMY. The measured UGF for this loop was ~ 150 Hz when FM2, 3, 4, 5 and 8 were all enabled. Note FM8 is an elliptic low pass (600 Hz cutoff).


LO1, LO2, AS1, AS4 actuation

We then lock the LO phase by feeding back BH55_Q_ERR to the actuation points under test with exactly the same filters but a servo gain of 0.6 but otherwise we are using the same servo filters FM2, 3, 4, 5 and 8 for this controls. The measured UGFs were all near ~ 70 Hz.

Here we had to be careful not to excite mechanical (?) resonances similar to the previously observed "violin" modes in LO1. In particular, we first noticed unsupressed 816 Hz noise in AS1 was being reinjected by the loop sometimes tripping the local damping loops, so we added bandstop filters at the AS1_LSC output filter bank. The resulting loop was then allowed to increase the gain and turn on FM2 and FM3 (boosts). This was also the case in AS4, where 268 Hz and second + third harmonics appeared to be excited by our feedback control. Finally, AS4 also displayed some mechanical excitation at 96.7 Hz, which seemed too low to be a "violin" mode, and its "Q" factor was not as high. We added a bandstop for this as well.

Attachment #1 shows LO_PHASE OLTFs when actuating in the different optics. By taking the actuation ratios (Attachment #2) with respect to our ITMY actuation reference and which had previously been calibrated to be 4.74e-9 / f^2 m / cts, we now have estimated our BHD suspension actuation calibrations to be:

  • LO1 = 3.14e-8 / f^2 m / cts
  • LO2 = 2.52e-8 / f^2 m / cts
  • AS1 = 3.14e-8 / f^2 m / cts
  • AS4 = 2.38e-8 / f^2 m / cts

This magnitudes are consistent with the expected coil driver ranges (about a factor of 10 difference).

Attachment 1: OLTF_LOPhaseLocking_ITMYSingleBounce.png
OLTF_LOPhaseLocking_ITMYSingleBounce.png
Attachment 2: ActuationRatio_ITMY_AS1_AS4_LO1_LO2.png
ActuationRatio_ITMY_AS1_AS4_LO1_LO2.png
  17207   Tue Oct 25 05:26:24 2022 ranaSummaryIOOMC SUS tuning

in looking closer at the IMC WFS performance I notice 2 issues:

  1. the watchdog thresholds are set to 200 mV, but this only made sense back when the OSEM calibration was 2 V/mm. Because of the increased analog gain(?) the RMS value of the watchdog sensors is now ~35 mV for MC1, so it will trip its watchdog and unlock the IMC with a 10x smaller seismic impulse than before. I recommend changing the watchdog thresholds appropriately changing the OSEM sensor signals to something so that its the same for all SUS.
  2. For the MC SUS, the F2P or F2A decoupling filters are not on. SO the POS damping loop is injecting a lot of pitch noise into the mirrors. We could perhaps lower the ~1 Hz angular motion by commissioning those filters for the MC optics. Does anyone know why we have several filters in those filter banks? I think we could contain it all in 1, although its fine to make a few different ones with different Q's for testing the performance.
  17211   Tue Oct 25 14:29:56 2022 PacoSummarySEIEarthquake tripped SUS

[Yuta, Paco, JC]

This eq  potentially tripped ETMY, PR2, PR3, AS1, AS4, SR2, LO1, LO2 suspensions during today's WB meeting. We restored them into normal local damping.


We aligned the arm cavities just to verify things were ok and then moved on to BHD comissioning. No problems spotted so far.

  17212   Tue Oct 25 17:27:11 2022 PacoSummaryBHDLO phase control with RF + audio sidebands

[Yuta, Paco]

Today we locked LO phase with BH55 + Audio dithering


Configuration

We worked with MICH locked using AS55_Q with an offset = 50. Our BH55_Q_ERR is the same as in the previous elog (in this thread). We enabled audio dithering of AS1 to produce 280.54 Hz sidebands (exc gain = 15000). We used ELP80 (elliptic, 4th order lowpass with the second resonant notch at 280.54 Hz) at the BH55_Q_AS1_DEMOD_I output. This allowed us to generate an error signal to feedback into AS1 POS. Attachment #1 shows a screen capture of this configuration.


Lock

We close a loop with the above configuration to lock the LO phase using only filters FM5, FM8 and then optionally boost with FM2. The compromise we had to make because of our phase margin was to achieve UGF ~ 20 Hz (in contrast with ~ 70 Hz used in single bounce). Attachment #2 shows the measured OLTFs for LO_PHASE control using this scheme; the red was the final measured loop, while the blue was our initial reference before increasing the servo gain.

 

Attachment 1: Screenshot_2022-10-25_17-36-45_LOPHASELOCKED.png
Screenshot_2022-10-25_17-36-45_LOPHASELOCKED.png
Attachment 2: Screenshot_2022-10-25_17-33-33_LOPHASELOCKING_MICHBHD_ELP80_280HzDither.png
Screenshot_2022-10-25_17-33-33_LOPHASELOCKING_MICHBHD_ELP80_280HzDither.png
  17216   Wed Oct 26 16:04:12 2022 PacoSummaryBHDLO phase control with RF + audio sidebands

[Yuta, Paco]

Today we again locked the LO phase with BH55 + Audio dithering under a zero-offset MICH


Configuration

We worked with MICH locked using AS55_Q with an offset = 0. Our BH55_Q_ERR is the same as in the previous elog (in this thread).We reduced the MICH offset from 50 to 0 slowly and kept an eye on the BH55 error signals. We realized that at zero offset, most of the error signal was in BH55_I_ERR (why?) so we rotated it back to BH55_Q_ERR (146 deg --> 56 deg). We then looked at the audio demod angle, and optimized it to allocated the error signal in the I quadrature (-15 deg --> 40 deg).


Lock

We close a loop with the above configuration to lock the LO phase using only filters FM5, FM8 and then optionally boost with FM2. The measured UGF ~ 20 Hz similar to the configuration with an offset present; and it seems there is some residual noise at ~ 20 Hz (observed in the residual error signal time trace with ndscope).


Next tasks:

  • Noise budget residual error in this configuration
  • Investigate negative count offset in DCPDs
  • Investigate why does the rotation angle change from single bounce to MICH?
  17221   Wed Nov 2 16:34:56 2022 PacoSummaryCalibrationSingle arm calibration run

[Anchal, Paco]

We added a notch filter on ETMY (the actuation point of the YARM control loop) to inject our calibration line at 575.170 Hz. The excitation is injected using the DARM Oscillator, with an exc. gain of ~ 500 (this gets us a decent > 10 SNR line in the ALS Y beat). With the arm cavity locked to the PSL (~150 Hz control bandwidth), and the aux laser locked to the cavity (~10 kHz control bandwidth) the goal of this run is to calibrate our actuator strength and more importantly to budget its uncertainty. For this we have looked at the ALS beat stability using Allan statistics; we noticed the ALS beatnote frequency fluctuations start to become dominated by 1/f (or divergent noise due to systematic drifts in the YARM loop) after 10 seconds (see Attachment #1) (we have managed to see 30 seconds stability with the HEPAs off and without locking to IMC).

Our prediction is that our demodulated calibration lines will display the least residual rms noise when averaging down to around this time. This is the only reason one would use allan statistics; to quantify the separation between statistical and systematic effects in a frequency measurement. To be continued...


gpstimes:

  • 1351464997 to 1351467139
  • 1351467259 to 1351468221
  • 1351468318 to ...
Attachment 1: frac_adev_demod_ybeat.pdf
frac_adev_demod_ybeat.pdf
  17224   Thu Nov 3 16:00:58 2022 alexSummaryGeneralSensoray updates

I am currently working on getting the driver reinstalled on Donatella for the sensoray. An issue keeps arising that will not allow me to run "make" successfully in the unzipped driver folder. Will continue to remedy this.

This is why there is no light showing up on the device while plugged in. The computer does see the device, but does not show its model due to the inability for it to communicate without the driver.

 

-Alex

  17228   Thu Nov 3 20:07:01 2022 AnchalSummaryBHDAS1 coil balancing required

[Anchal, Koji]

The LO phase lock that was achieved lasts for a short time because as soon as a considerable POS offset is required on AS1, the POS to PIT coupling causes the AS-LO overlap to go away. To fix this, we need to balance the coil outputs of AS1 atleast and add the f2a filters too. To follow similar method as used for IMC optics, we need a sensor for true PIT and YAW motion of AS1. Today, we looked into the possiblity of installing a QPD at BHD output path to use it for AS1, AS4, LO1, LO2, SR2, PR2 and PR3 coil strength tuning. We found a QPD which is mentioned in this elog. We found QPD interface boards setup for old MCT and MC Refl QPDs (dating before 2008). We also found the old IP-POS QPD cable between 1Y2 and BS Oplev table. We took out this cable from BS oplev end upto ITMY opleve table, put on a new DB25 connector on the ribbon cable, and connected it to the QPD on ITMY table. There is still following work to be done:

  • Move back the BHD port camera a few inches and the lends with it.
  • Put a beamsplitter in the beam going to this camera and align it to fall on the new QPD.
  • Connect the the other end of cable to QPD interface board on 1Y2.
  • Take the lemo outputs or IDC outputs from the QPD interface board to spare ADC inputs (maybe on LSC I/O chassis or SUS2 I/O chassis).
  • Make changes in RTS model to read this QPD input.
  • Enjoy balancing the coils on the 7 new suspensions.
  17236   Mon Nov 7 17:10:41 2022 AnchalSummaryBHDQPD installation seems like lost cause

The new QPD installation is turning out to be much more hard than it originally seemed. After finsing the cable, QPD and interface board, when I tried to use the cable, it seems like it is not powered or connected to the interface board at all. I tried both QPD ports on the QPD interface board (D990692) both none worked. I measured the output pins of IDC style connector on the interface board and they seem to have the correct voltages at the correct pins. But when I connect this to our cable and go to the other side of the cable which is a DB25, use a breakout board and see for the voltages, I see nothing. The even pins which are supposed to be connected to each other and to GND are also not connected to each other. I pulled out teh DB25 end of the cable and brought it close to the IDC end to do a direct conitnuity test and this test failed too.

I even foudn another IDC end of a spare QPD cable hanging near 1Y2, but could not find the other end of this cable either.

So moving forward, we have following options:

  • Assume the cable is bad and try to find another cable.
    • It is very hard to find these cables in the lab. Koji and I have already done one sweep.
  • Source 26 pin 2 row IDC female connector and make a ribbon cable ourselves.
    • We probably will need to buy this connector for this to work.
    • Downs has apparantely thrown away all IDC connectors.
  • Use clean room QPD that does not use this interface.
    • The QPD used in clean room tests for suspension hanging used a different board.
    • This board is just lying on the floor, mounted on one slot of a big 6U chassis.
  • Use AS WFS
    • If used in current position, it would not be useful for BHD port or tuning LO1, LO2, and AS4.
    • If taken to ITMY oplev table, we will need to source LO and opther connections right at the PD head as that is design for these PDs.
  • Use GigE camera
    • We can replace the analog camera with a GigE camera on the BHD output.
    • We will need to revide GigE camera code and medm screens for this, and run an ethernet cable to ITMY oplev table.
  • Someone verify that the cable is indeed not working as I am seeing above. If I am wrong, I would be a happier person.
  17247   Tue Nov 8 21:39:12 2022 alexSummaryGeneralSensoray & SDI Video Encoder selection

I have been looking at various replacements for the sensoray, and have found that the majority of new usb video encoders don't have drivers anymore and now just work through being embedded with video-capturing software. This means that the hardware must be used with a compatible video player such as VLC or OBS. VLC can natively be run with terminal commands, and because OBS is open source, there are packages that can be downloaded to use terminal commands to control the software as well. I am not sure to what extent the usb video encoder can then be controlled with these commands, but this seems to be the easiest method so far. I will finish picking which new unit we should purchase tomorrow, and order it through JC. 

  17253   Thu Nov 10 17:40:31 2022 PacoSummaryCalibrationCalibration Plan

Plan to calibrate single arm actuation strength

  1. Lock single arm cavity (e.g. YARM)
  2. Lock YAUX laser to arm cavity (actuation point is ETMY)
  3. With the notch on the YARM loop filter (actually on ETMY),
  4. Turn on cal line (e.g. DARM osc) to move ITMY; here the frequency is chosen to be away from 600 Hz (line harmonic) and from violin modes for ITMY (642 Hz). The lower value of 575.17 Hz was chosen to avoid demodulating noise peaks at 455 Hz and 700 Hz.
  5. Get raw YALS beatnote (we chose the demod angle of -35 deg to minimize Q).

The analysis is as follows:

  1. Get demodulated IQ timeseries for the duration of the locks before lowpass filter (C1:CAL-SENSMAT_DARM_BEATYF_I_DEMOD_I_IN1); we are also storing the raw beatnote if we want to do software demodulation.
  2. Look at the allan deviation of I and Q to establish the timescale over which our measurement is dominated by statistical uncertainty -- after this time, the uncertainty is expected to be due to systematic error / drift. In this case as shown by Attachment #1 the time is around 60.6 seconds.
  3. At this frequency and with 500 gain the ITMY coils should be actuating 7.32 pm of amplitude displacement.
  4. The minimum allan deviation does indeed predict the statistical uncertainty limited rms if we look at the power spectra of the demodulated cal line over different time periods (Attachment #2), notice I lowpassed the raw timeseries.
  5. I think the next step is to get the nominal calibration value and repeat the measurment for more than a single cal line.
  6. Roughly from the deviation plot, our fractional beatnote deviation is a proxy for the calibration uncertainty. 1.15e-16 of beatnote stability should translate to a fractional displacement stability of ~4.57e-15 at 60 seconds; giving an ultimate statistical calibration uncertainty of 0.06% at this particular frequency when averaging for this long. It might be interesting to see a calibration frequency dependent allan deviation plot.
Attachment 1: allan_dev_beatY_demodI.pdf
allan_dev_beatY_demodI.pdf
Attachment 2: asd_and_rms_beatY_demodI.pdf
asd_and_rms_beatY_demodI.pdf
  17257   Fri Nov 11 14:15:45 2022 PacoSummaryCalibrationSingle arm cal with 5 lines

I turned all the LSC oscillators on and used the digital demod for BEATYF (fine y als beat) to grab the data. For this I added notches onto SCY ETMY LSC filter banks FM6-10 to account for these lines at 30.92, 211.10, 313.31, 315.17 Hz (basically just reusing the osc models) and adjusted the sensing matrix to actuate on ITMY.

I aligned and locked YARM, and then I aligned and locked the YAUX. The lock seems pretty robust with an avg green transmission GTRY ~ 0.185 counts for TEM00.


Trying to see other lines appear on the BEATYF demod channels, but so far no luck. I scaled down the exc gain from 500 counts (snr ~ 20 at 575 Hz) and verified the notches are working. Since I am unsure of the issue here and WFS tests are happening at 4 today, I decided to take some beat data under different conditions -->

HEPA OFF and PSL Shutter Open

gpstime start = 1352244763 gpstime end = 1352245405

HEPA OFF and

PSL Shutter Closed

gpstime start = 1352245574

gpstime end = 1352246216

HEPA ON and

PSL Shutter Closed

gpstime start = 1352246240 gpstime end = 1352246882
  17266   Tue Nov 15 11:04:01 2022 PacoSummaryCalibrationSingle arm cal with 5 lines

YALS Hardware inspection

The ALS Cal for ITMY actuation was off by ~ 1000, so I decided I don't trust / understand what this beatnote is seeing. Then, I went in the lab to inspect things;

  1. ALS DFD and DEMOD: The demod box was off no perhaps on purpose, more likely by accident... the switch was off in the rear of the 1U box in the LSC rack... Also, the DB9 cable labeled ALS was disconnected. Fixed both these bugs and verified it worked all the way into cds.
  2. YARM Green injection: Did some re-alignment, and noted the mode was hopping a bit too much (once every couple of seconds) so I rotated the half waveplate before the green PZT steering mirrors by  ~ 8 deg and used the latter to get a GTRY transmission of > 0.320 (counts), about 75% more than last time. Finally I made sure the mode is robustly locked for several minutes.

Beatnote calibration

The factor above may be explained by the bogus signals coming into the beat fine phase channels on the ALS model. After locking the YARM with POY11, and locking the YAUX to the YARM cavity, I turned on the LSC oscillators -- all five of them see Attachment #1 for the screenshot -- and looked for the lines in the C1:ALS-BEATY_FINE_PHASE_OUT channel. Here, again the sensing output matrix was set up to actuate on ITMY, while the ETMY (control point of YARM loop) had all the output notches on. Once all lines were visible in the YAUX beatnote, I had to reduce the LSC filter gain from 0.012 to 0.011 to prevent loop oscillations... Then I recorded the gpstimes below with different conditions.

  • HEPA ON (JC Inside lab)
    • gpstime = 1352575798 to 1352576046
  • HEPA OFF (JC Inside lab)
    • gpstime = 1352576125 to 1352576216
  • HEPA OFF (JC in the control room)
    • gpstime = 1352576641 to 1352577591

Analysis

Basically, only the DARM line was recorded (DQ channs) so I modified the c1cal to store the SIG_OUT and DEMOD_I_IN1 channels for both BEATX and BEATY cal signals. This means I need to repeat this measurement. In the meantime I am also going to try and rerun calibrate the BEAT HZ transfer function.

Attachment 1: als_cal_osc_2022_11_15.png
als_cal_osc_2022_11_15.png
  17270   Tue Nov 15 19:00:56 2022 yutaSummaryBHDMICH locked with balanced homodyne readout at some LO phase

[Paco, Yuta]

MICH was locked with BHD DCPD A-B signal with LO phase controlled.
Locking procedure and configuration was as follows (see Attachment #1).

1. Lock MICH with AS55_Q, with C1:LSC-MICH_GAIN=-3, FM4, FM5, FM8, FM10 (boost filters are turned off to have more phase margin).

2. Lock LO PHASE with BH55_Q, with C1:HPC-LO_PHASE_GAIN=6, FM5, FM8, feeding back to AS1.
  - C1:LSC-BH55_PHASE_R=136.136 deg was tuned to minimize I when AS-LO is fringing with MICH locked with an offset of 50 (we first thought 136.136 deg - 90 deg is better from 40m/17216, but today, 136.136 deg seems to work better; Reason needs to be investigated).
  - We are supposed to use C1:HPC-BH55_Q_AS1_DEMOD_I_OUT to control the LO phase to give maximum MICH signal on BHD_DIFF (40m/17170), but somehow BH55_Q without audio dither was OK to get MICH signal. Line injection at 211.1 Hz on BS was seen in BHDC_DIFF (and AS55_Q), even if we use BH55_Q to lock LO PHASE (see Attachment #2; MICH_B is BHDC_DIFF and MICH_A is AS55_Q) or BH55_Q_AS1_DEMOD_I to lock LO PHASE (with both signs). Reason needs to be investigated.
  - Audio dither was done using AS1 with excitation of 15000 counts at 281.79 Hz. C1:HPC-BH55_Q_AS1_DEMOD_PHASE=60 deg was tuned to minimize Q with injection of line at 13 Hz using LO1.

3. Handed over MICH lock from AS55_Q to 0.66 * C1:LSC-DCPD_A - 1 * C1:LSC-DCPD_B. This was done by using C1:LSC-MICH_A and MICH_B gains. C1:LSC-MICH_A_GAIN=1 was handed over to C1:LSC-MICH_B_GAIN=-1.
  - 0.66 * A - B was tuned so that BHDC_DIFF will be zero (as it supposed to be with MICH offset of zero).
  - AS55_Q and BHDC_DIFF had roughly the same optical gain at 211.1 Hz (actually, BHDC_DIFF had higher optical gain; see Attachment #2), so we used MICH_A_GAIN=1 and C1:LSC-MICH_B_GAIN=-1
  - After handing over of BHDC_DIFF, OLTF was measured. UGF was ~70 Hz (Attachment #3).

Next:
  - Investigate how to get optimal LO phase. With BH55_Q or BH55_Q + audio dithering? How to optimize demod phases?
  - How do we balance DCPD A and B? What is the effect of BHD BS being 44:56 not 50:50?
  - Measure amount of MICH signal in BHDC_DIFF with different LO phases.
  - Improve SNR in BH55.
  - It will be much simpler if we send BHDC_SUM and BHDC_DIFF to c1lsc from c1hpc, instead of sending un-unwhitened BHDC_A and B.

Attachment 1: Screenshot_2022-11-15_18-34-25_MICHBHDLocked.png
Screenshot_2022-11-15_18-34-25_MICHBHDLocked.png
Attachment 2: Screenshot_2022-11-15_19-02-02_MICHLine.png
Screenshot_2022-11-15_19-02-02_MICHLine.png
Attachment 3: Screenshot_2022-11-15_18-38-20_BHDMICHOLTF.png
Screenshot_2022-11-15_18-38-20_BHDMICHOLTF.png
  17274   Wed Nov 16 18:41:17 2022 yutaSummaryBHDOptical gain calibrations for BHD MICH

Optical gains of AS55 and BH55 are calibrated for BHD MICH.

LO-ITM single bounce:
 With LO-ITM signle bounce fringe, optical gain of BH55_Q is measured using a method similar to MICH calibration in AS55 (40m/16929).
 Demodulation phase for BH55 is tuned to minimize I when LO-ITM is freeswinging (using getPhaseAngle.py).
 (Notebook: /opt/rtcds/caltech/c1/Git/40m/scripts/CAL/BHD/BHDOpticalGainCalibration.ipynb)
 Results are the following:

 LO-ITMY fringe: 7.84e9 counts/m (demod phase 147.1 +/- 0.3 deg) See Attachment #1
 LO-ITMX fringe: 8.44e9 counts/m (demod phase 149.6 +/- 0.4 deg) See Attachment #1

 Difference in the optimal demodulation phase 2.5 +/- 0.5 deg agrees with half of Schnupp asymmetry, as expected (40m/17007).
 Difference in the optical gain for LO-ITMY and LO-ITMX is probably from statistical fluctuation.


BHD MICH:
 Sensing matrix was measured by injecting a line at BS (300 counts @ 211.1 Hz), LO1 (5000 counts @ 287.1 Hz) and AS1 (5000 counts @ 281.79 Hz), when MICH is locked with AS55_Q and LO PHASE is locked with BH55_Q (both with no offset).
 Using the sensing matrix, demodulation phase was tuned to minimize I phase for MICH signal in AS55 and LO1 signal in BH55.
 After the demodulation phase tuning. sensing matrix was measured to be the following.
 See, also Attachment #3 for injected peaks. I phase signal is successfully suppressed by at least an order of magnitude.
 (Notebook: /opt/rtcds/caltech/c1/Git/40m/scripts/CAL/SensingMatrix/MeasureSensMatBHD.ipynb)

Sensing Matrix with the following demodulation phases (counts/counts)
{'AS55': -160.15695076011946, 'BH55': 154.13916838400047}
      Sensors           MICH @211.1 Hz          LO1 @287.1 Hz            AS1 @281.79 Hz           
C1:LSC-AS55_I_ERR_DQ    1.22e-05 (120.53 deg)   7.24e-07 (85.64 deg)     1.26e-06 (40.42 deg)    
C1:LSC-AS55_Q_ERR_DQ    2.95e-03 (-101.62 deg)  1.24e-06 (-80.43 deg)    1.69e-06 (152.31 deg)    
C1:LSC-BH55_I_ERR_DQ    1.28e-03 (80.95 deg)    3.44e-06 (109.31 deg)    2.22e-06 (154.40 deg)    
C1:LSC-BH55_Q_ERR_DQ    7.44e-03 (77.38 deg)    2.56e-04 (-59.85 deg)    2.42e-04 (6.40 deg)    
C1:HPC-BHDC_DIFF_OUT    2.21e-03 (82.45 deg)    4.37e-05 (121.87 deg)    3.61e-05 (-169.09 deg)

 Using BS actuation efficiency of 26.08e-9 /f^2 m/counts (40m/16929), optical gain for AS55_Q and BHDC_DIFF for MICH is

2.95e-03 / (26.08e-9/(211.1**2)) = 5.04e9 counts/m (AS55_Q for MICH)
2.21e-03 / (26.08e-9/(211.1**2)) = 3.78e9 counts/m (BHDC_DIFF for MICH)

 For AS55_Q, this is a factor of 4~5 higher than the previous measurement from free swing (40m/16929). Why?
 Free swing measurement was done again, and this gave 1.24e9 counts/m, which is consistent with the previous measurement (see Attachment #3).

 Using LO1 and AS1 actuation efficiencies of 3.14e-8 /f^2 m/counts (40m/17206), optical gains for BH55_Q for LO1 and AS1 are

2.56e-04 / (3.14e-8/(287.1**2)) = 6.72e8 counts/m (BH55_Q for LO1)
2.42e-04 / (3.14e-8/(281.79**2)) = 6.12e8 counts/m (BH55_Q for AS1)

Next:
 - Compare them with expected values
 - Measure them with different locking points (different LO phases, MICH offsets)
 - Investigate why MICH optical gain in AS55 is 4~5 times higher than free swing measurement (use different modulation frequency?)

Summary of actuation calibration so far (counts from C1:LSC-xx_EXC or C1:SUS-xx_LSC_EXC):
BS   : 26.08e-9 /f^2 m/counts (see 40m/16929)
ITMX :  5.29e-9 /f^2 m/counts (see
40m/16929)
ITMY :  4.74e-9 /f^2 m/counts (see
40m/16929)
ETMX : 10.91e-9 /f^2 m/counts (see 40m/16977 and 40m/17014)
ETMY : 10.91e-9 /f^2 m/counts (see 40m/16977)

MC2 : -14.17e-9 /f^2 m/counts in arm length (see 40m/16978)
MC2 :   5.06e-9 /f^2 m/counts in IMC length (see 40m/16978)
LO1 : 3.14e-8 / f^2 m/counts
(see 40m/17206)
LO2 : 2.52e-8 / f^2 m/counts (see 40m/17206)
AS1 : 3.14e-8 / f^2 m/counts (see 40m/17206)
AS4 : 2.38e-8 / f^2 m/counts (see 40m/17206)

Attachment 1: Screenshot_2022-11-16_18-57-12.png
Screenshot_2022-11-16_18-57-12.png
Attachment 2: Screenshot_2022-11-16_18-49-53_BHDMICHCalLines.png
Screenshot_2022-11-16_18-49-53_BHDMICHCalLines.png
Attachment 3: LSC-AS55_Q_ERR_DQ_1352689642.png
LSC-AS55_Q_ERR_DQ_1352689642.png
  17276   Thu Nov 17 09:06:35 2022 JCSummaryGeneralLight Replace

Electrical Shop came in today to replace the lightbulbs around 40m. I supervised the entire visit, inside and outside the lab area. I was sure to use the ladders which were already inside the lab area. Although, while I was crawling under the MC beam tube, I came up too quickly and bumped it. This may have caused MC to become misaligned. Anyways, Yehonathan and I are realigning now.

 

  17279   Thu Nov 17 14:12:58 2022 yutaSummaryBHDOptical gain calibrations for BHD MICH with lower UGF

[Paco, Yuta]

We found that MICH UGF was unexpectedly high, ~200 Hz, in the measurement yesterday, which makes the closed loop gain to be more than one at MICH line injection at 211.1 Hz.
We did optical gain calibrations for AS55, BH55 and BHDC_DIFF in BHD MICH again with UGF at around 10 Hz.
This solved the inconsistent result with free swing calibration.

What we did:
 Did the same measurement for BHD MICH as written in 40m/17274, but with MICH UGF of ~10 Hz and LO PHASE UGF of ~15 Hz (see OLTFs in Attachment #1, and filter configurations in Attachment #2).
 Updated sensing matrix is as follows

Sensing Matrix with the following demodulation phases (counts/counts)
{'AS55': -163.52789698340882, 'BH55': 152.7860744565449}
      Sensors        	MICH @211.1 Hz       	LO1 @287.1 Hz       	AS1 @281.79 Hz       	
C1:LSC-AS55_I_ERR_DQ	1.85e-05 (-118.82 deg)	3.31e-07 (-32.19 deg)	7.86e-07 (112.27 deg)	
C1:LSC-AS55_Q_ERR_DQ	7.32e-04 (59.57 deg)	1.19e-06 (158.17 deg)	9.07e-07 (-92.25 deg)	
C1:LSC-BH55_I_ERR_DQ	5.02e-04 (-123.21 deg)	1.79e-05 (-26.73 deg)	1.76e-05 (-120.23 deg)	
C1:LSC-BH55_Q_ERR_DQ	1.75e-03 (59.57 deg)	2.71e-04 (-22.64 deg)	2.56e-04 (-114.37 deg)	
C1:HPC-BHDC_DIFF_OUT	1.00e-03 (-115.93 deg)	3.09e-05 (-14.99 deg)	2.84e-05 (-110.23 deg)	

 Using BS actuation efficiency of 26.08e-9 /f^2 m/counts (40m/16929), optical gain for AS55_Q and BHDC_DIFF for MICH is

7.32e-03 / (26.08e-9/(211.1**2)) = 1.25e9 counts/m (AS55_Q for MICH) This is consistent with freeswing measurement (1.24e9 m/counts) 40m/17274
1.00e-03 / (26.08e-9/(211.1**2)) = 1.71e9 counts/m (BHDC_DIFF for MICH)

 Using LO1 and AS1 actuation efficiencies of 3.14e-8 /f^2 m/counts (40m/17206), optical gains for BH55_Q for LO1 and AS1 are

2.71e-04 / (3.14e-8/(287.1**2)) = 7.12e8 counts/m (BH55_Q for LO1)
2.56e-04 / (3.14e-8/(281.79**2)) = 6.47e8 counts/m (BH55_Q for AS1)

  (Notebook: /opt/rtcds/caltech/c1/Git/40m/scripts/CAL/SensingMatrix/MeasureSensMatBHD.ipynb)

Next:
 - Compare them with expected values
 - Measure them with different locking points (different LO phases, MICH offsets; LO phase can be calibrated using optical gain calibration of BH55_Q)

Attachment 1: Screenshot_2022-11-17_14-39-17_MICHLOPHASEOLTF.png
Screenshot_2022-11-17_14-39-17_MICHLOPHASEOLTF.png
Attachment 2: Screenshot_2022-11-17_14-41-40_LowUGFConfiguration.png
Screenshot_2022-11-17_14-41-40_LowUGFConfiguration.png
  17282   Thu Nov 17 20:02:10 2022 yutaSummaryBHDMICH optical gain measurements with different LO phases

MICH optical gain was measured with different LO phases over ~90 degrees.
Zero crossing of BH55_Q_ERR seems to be roughly 55 degrees away from optimal LO phase.

What we did:
 - Locked MICH with AS55_Q with no offset, with UGF at ~10 Hz (same as configuration in 40m/17279).
 - Injected BS calibration line at amptilude of 300 counts at 211.1 Hz.
 - Locked LO Phase with BH55_Q with different offsets added at C1:HPC-LO_PHASE_OFFSET.
 - Measured sensing matrix at that frequency. Counts are calibrated into meters using actuator efficiencies as described in 40m/17279.
 - LO phase was obtained using a DC value of BH55_Q. This was calibrated into degrees from the following:

Amplitude of LO-AS fringe in BH55_Q was calculated to be

A = BH55optgain*lamb/(4*pi) = 60 counts

where BH55optgain is 7.12e8 counts/m, which is optical gain of BH55_Q for LO1 measured in 40m/17279.
(Actually, BH55_Q goes upto ~ +/-200 counts in time series data, but maybe 60 is the nominal fringe amplitude, considering alignment fluctuations and fluctuation in AS darkness? Note that, no offset in BH55_Q is assumed in this calculation, but AM etc can create an offset.) 
LO phase can be obtained by

LOphase = arcsin(BH55_Q/A)

where BH55_Q a DC value (10 sec average) of BH55_Q.

Result:
 Attachment #1 is uncalibrated plot C1:HPC-LO_PHASE_OFFSET of around +/- 50 was the maximum we could add, and more offset gave unstable lock.
 Attachment #2 is calibrated plot. AS55_Q does not depend on LO phase, as expected. BH55_Q and BHDC_DIFF depend on LO phase as expected. BH55_I and AS55_I stay at low level, as expected (this means that our RF demodulation phase is OK).
 Dotted gray line is an eyeball fit of expected curve (40m/17170) to fool your eyes.
 This tells you that we are roughly 55 deg away from LO phase which gives maximum MICH signal for BHDC_DIFF.
 Error bar in x-axis is from standard deviation of BH55_Q fluctuations. Error in y axis is probably ~20% at maximum.
 Notebook: /opt/rtcds/caltech/c1/Git/40m/scripts/CAL/SensingMatrix/MeasureSensMatBHD.ipynb

Next:
 - Repeat the measurement with
   - MICH locked with higher UGF, with notch at 211.1 Hz, for more robust AS dark fringe
   - DCPD A and B balanced at 211.1 Hz (null MICH signal for BHDC_SUM to balance?)
   - Measure optical gain also for BHDC_SUM and BH55_Q demodulated at audio dither
   - Lock LO phase at different sign so that we can sweep LO phase over ~180 deg
   - Sign-sensitive optical gain measurement (demodulation with BS motion necessary)
 - Compare with expected values from simulations
 - Why do we have 55 degrees offset? Expected offset is 90 degrees...
   - Check if there is any RAM in 55 MHz in the input beam by measuring AM with ITM single bounce

Attachment 1: UncalibratedMICHOpticalGainVSLOphase20221117.png
UncalibratedMICHOpticalGainVSLOphase20221117.png
Attachment 2: CalibratedMICHOpticalGainVSLOphase20221117.png
CalibratedMICHOpticalGainVSLOphase20221117.png
  17284   Fri Nov 18 13:05:00 2022 yutaSummaryBHDGains adjusted for bandstop filters for BHD optics

[Paco, Yuta]

We realized that bandstop filters ("violin" filters) we implemented in 40m/17206 had pass band gain of -1dB.
gain(1,"dB") was added to all the filters (see Attachment #1 for gain adjusted violin filters for AS1).
We also realized that audio dither frequency we chose to generate BH55+audio dither error signal and to measure sensing matrix at ~280 Hz was too close to violin filters.
These will affect calibrations by upto ~60%.
For example, actuation gains should be actually

  • LO1 = 3.14e-8 / f^2 m / cts * 3dB = 4.44e-8 / f^2 m / cts (3 violin filters)
  • LO2 = 2.52e-8 / f^2 m / cts * 0dB = 2.52e-8 / f^2 m / cts (no violin filters)
  • AS1 = 3.14e-8 / f^2 m / cts * 3dB = 4.44e-8 / f^2 m / cts (3 violin filters)
  • AS4 = 2.38e-8 / f^2 m / cts * 4dB = 3.36e-8 / f^2 m / cts (3 violin filters+ bandstop at 96.7 Hz)


Next:
 - Redo actuator calibrations for LO1, LO2, AS1, AS4
 - Redo sensing matrix measurements with different audio dither frequencies for LO1 and AS1

Attachment 1: Screenshot_2022-11-18_13-16-31_AS1ViolinFilters.png
Screenshot_2022-11-18_13-16-31_AS1ViolinFilters.png
  17285   Fri Nov 18 16:58:39 2022 yutaSummaryBHDActuator calibrations for MICH BHD

As there is some confusion in actuator calibration, we have done the measurement again from scratch.
Results are the following.
New values for LO1, LO2, AS1, AS4 are obtained from free swinging ITMY-LO, so it should be more robust.

BS   : 26.54e-9 /f^2 m/counts
ITMX :  4.93e-9 /f^2 m/counts
ITMY :  4.90e-9 /f^2 m/counts
LO1  : 26.34e-9 /f^2 m/counts
LO2  :  9.81e-9 /f^2 m/counts
AS1  : 23.35e-9 /f^2 m/counts
AS4  : 24.07e-9 /f^2 m/counts

BS, ITMX, and ITMY actuator calibration:
 Followed the procedure in 40m/16929.
 Calibrated AS55_Q using X-Y plot to be 9.72e8 counts/m (Attachment #1), locked MICH with UGF of 10 Hz, and measured the transfer function from C1:LSC-BS,ITMX,ITMY_EXC to C1:LSC-AS55_Q_ERR.
 The result is Attachment #2. They are consistent with 40m/16929.

LO1, LO2, AS1, and AS4 actuator calibration:
 Followed similar steps with ITMY-LO fringe.
 Calibrated BH55_Q using X-Y plot to be 7.40e9 counts/m (Attachment #3), locked ITMY-LO with UGF of ~15 Hz (Attachment #4), and measured the transfer function from C1:SUS-LO1,LO2,AS1,AS4_LSC_EXC to C1:LSC-BH55_Q_ERR.
 The result is Attachment #5. They are inconsistent with 40m/17284, but this one should be more robust (see discussions below).


LO1, LO2, AS1, and AS4 actuator calibration by taking the ratio between ITMY:
 We have also followed the steps in 40m/17206 to calibrate BHD actuators.
 This method does not depend on BH55_Q optical gain calibration, but depends on ITMY calibration.
 Measured OLTFs for ITMY-LO fringe locking is Attachment #6, and actuator ratio with respect to ITMY is Attachment #7. In this measurement, Bandstop filter at 96.7 Hz for AS4 was turned off, and gain was lowered by a factor of 2 to avoid AS4 oscillating.
 This gives

LO1  : 116.81e-9 /f^2 m/counts
LO2  :  51.69e-9 /f^2 m/counts
AS1  : 101.48e-9 /f^2 m/counts
AS4  : 117.84e-9 /f^2 m/counts

 These are not consistent with 40m/17284, and larger by a factor of ~2-3.
 These are also not consistent with the values from free swinging measurement, and are larger by a factor of ~4-5.
 I guess there are some gains missing when comparing ITMY loop in c1lsc and other loops in c1hpc.

Attachment 1: AS55QMICH20221118.png
AS55QMICH20221118.png
Attachment 2: ActBSITMXITMY20221118.png
ActBSITMXITMY20221118.png
Attachment 3: BH55QITMYLO20221118.png
BH55QITMYLO20221118.png
Attachment 4: Screenshot_2022-11-18_14-41-57_LO-ITMY_LowUGF.png
Screenshot_2022-11-18_14-41-57_LO-ITMY_LowUGF.png
Attachment 5: ActLOAS20221118.png
ActLOAS20221118.png
Attachment 6: ITMY-LO-OLTF20221118.png
ITMY-LO-OLTF20221118.png
Attachment 7: ITMY-LO-OLTFRatio20221118.png
ITMY-LO-OLTFRatio20221118.png
  17287   Fri Nov 18 22:46:02 2022 yutaSummaryBHDMICH optical gain measurements with different LO phases, with signs

MICH optical gain with a sign was measured with different LO phases over ~180 degrees, with updated calibration and higher MICH UGF.
Zero crossing of BH55_Q_ERR seems to be 68 degrees away from optimal LO phase.

Calibrated sensing matrix:
 - Locked MICH with AS55_Q at dark fringe, with UGF of ~200 Hz. Notch at 311.1 Hz was turned on.
 - Locked LO PHASE with BH55_Q, with UGF of ~10 Hz (C1:HPC-LO_PHASE_GAIN=-2, using LO1).
 - Measured the sensing matrix as written in 40m/17279, but with different dither frequencies to avoid violin mode frequencies and to match with already-installed notch filters.
 - Sensing matrix was calibrated into meters using actuator gains measured in 40m/17285
 - Sign was added by comparing the phase with C1:SUS-xx_LSC_OUT. If they are 90-270 deg apart, minus sign was added to the sensing matrix.
 - Resuts are as follows. At least important green ones are consistent with previous measurements (40m/17279).

Calibrated sensing matrix with the following demodulation phases (counts/m)
{'AS55': -164.1726747789845, 'BH55': 169.57651332419115}
      Sensors            MICH @311.1 Hz           LO1 @147.1 Hz           AS1 @141.79 Hz           
C1:LSC-AS55_I_ERR_DQ    2.72e+06 (84.89 deg)    6.41e+05 (14.60 deg)    -1.98e+05 (206.79 deg)    
C1:LSC-AS55_Q_ERR_DQ    -1.20e+09 (-228.85 deg)    -1.43e+06 (-106.51 deg)    1.41e+06 (29.21 deg)    
C1:LSC-BH55_I_ERR_DQ    -2.45e+09 (-230.64 deg)    -6.57e+07 (167.84 deg)    7.28e+07 (-16.56 deg)    
C1:LSC-BH55_Q_ERR_DQ    7.81e+09 (-48.64 deg)    -7.34e+08 (159.70 deg)    8.06e+08 (-10.08 deg)    
C1:HPC-BHDC_DIFF_OUT    -9.91e+08 (-224.55 deg)    -1.13e+08 (164.14 deg)    1.26e+08 (-3.95 deg)    
C1:HPC-BHDC_SUM_OUT    -6.84e+06 (-104.69 deg)    1.50e+07 (-8.71 deg)    -1.79e+07 (173.80 deg)    
LO phase from C1:LSC-BH55_Q_ERR_avg 4.98e-03 +/- 1.65e+01 deg

Estimating LO phase:
 - Using 7.34e+08 counts/m, which is an optical gain of BH55_Q for LO1, LO phase can be estimated as follows.

A = BH55optgain*lamb/(4*pi) = 62 counts
LOphase = arcsin(BH55_Q/A)

 - When C1:HPC-LO_PHASE_GAIN is plus, LOphase was calculated with the following to take into account of the sign flip in the controls.

LOphase = 180 - arcsin(BH55_Q/A)

Balancing A-B:
 - BHDC_A and BHDC_B were balanced to give null MICH signal in BHDC_SUM at 311.1 Hz. This gave BHDC_DIFF = 0.919*A - B.
 - It seems like this balancing gain changes over time by ~30%.

Result:
 - Attachment #1 is uncalibrated MICH optical gain in different LO phases, and Attachment #2 is the calbirated one. Basically the same with 40m/17282, but with updated calibration and sign considerations.
 - In addition to the previous measurements, we can see that BHD_SUM is not dependent on LO phase (small dependence probably from not perfect A and B balancing).
 - 0 deg of LO phase means that it is a zero crossing of BH55_Q with a slope that LO PHASE loop can be closed with a minus C1:HPC-LO_PHASE_GAIN, feeding back to LO1.
 - Dotted and dashed gray lines are from scipy.optimize.curve_fit using the following fitting function (not an eyeball fit this time!).

def fitfunc(x, a,b,c):
    return a*np.sin(np.deg2rad(x-b))+c

 - Fitting results show that we are -22 deg away from our intuition that BH55_Q crosses zero when BHDC_DIFF give no MICH signal (68 degrees away from optimal LO phase).
 - Fitting results also show that BH55_Q sensitivity to MICH crosses zero when BHD_DIFF sensitivity to MICH maximizes. This suggests that BH55+MICH dither can be used to lock LO phase to optimal LO phase.

Notebook: /opt/rtcds/caltech/c1/Git/40m/scripts/CAL/SensingMatrix/MeasureSensMatBHD.ipynb

Next:
 - Compare with expected values from simulations
 - Why do we have -22 deg?
   - Check if there is any RAM in 55 MHz in the input beam by measuring AM with ITM single bounce (quick measurement shows it is small)
   - Unbalanced BHD BS?
   - Contribution from 55 MHz sidebands from LO beating with 55 MHz sidebands from AS?
       - Lock LO phase using audio dither only (demodulate BHDC_DIFF?).

Attachment 1: UncalibratedMICHOpticalGainVSLOphase20221118.png
UncalibratedMICHOpticalGainVSLOphase20221118.png
Attachment 2: CalibratedMICHOpticalGainVSLOphase20221118.png
CalibratedMICHOpticalGainVSLOphase20221118.png
  17291   Mon Nov 21 11:52:50 2022 RadhikaSummaryCalibrationSingle arm cal with 5 lines

[Paco, Radhika]

We set out to realign the YARM AUX laser input into the arm cavity.

- We noticed that the GTRY beam was way off the center of the screen, so we went to the vertex table to align the camera.

- The beam spot at GTRY PD was large/divergent, so we shifted the PD closer to the penultimate mirror. We also doubled the PD gain. Transmission went from ~0.3 to ~0.7 (with gain doubled).

- We returned to the YARM end table to finalize alignment with the green PZT steering mirrors. GTRY was maximized to ~0.77.

  17294   Mon Nov 21 17:44:00 2022 yutaSummaryBHDMICH BHD displacement sensitivity with AS55_Q and BHD_DIFF

[Paco, Yuta]

MICH displacement sensitivity was compared under AS55_Q locking and BHD_DIFF locking.
Sensitivity with BHD was better by more than an order of magnitude due to smaller sensing noise.
During the measurement, LO phase fluctuation was ~13 deg RMS.

Locking configurations:
 - MICH was first locked with AS55_Q, no offset, and then handed over to BHD_DIFF after LO phase locked. FM2, FM3, FM4, FM5, FM6, FM8, FM10 on, C1:LSC-MICH_GAIN=-3 gave UGF of around 80 Hz.
 - LO PHASE was locked with BH55_Q, no offset. FM5, FM8 on, C1:HPC-LO_PHASE_GAIN=-2 feeding back to LO1 gave UGF of around 40 Hz.
 - Attachment #1 shows the OLTFs.

Sensitivity estimate:
 - Sensitivity was estimated using measured actuator gains and optical gains. Following numbers are used.

C1:LSC-AS55_Q_ERR to MICH 1.08e-9 counts/m (measured at 311.1 Hz today)
C1:HPC-BHDC_DIFF to MICH 1.91e-9 counts/m (measured at 311.1 Hz today)
BS   : 26.54e-9 /f^2 m/counts (40m/17285)
LO1  : 26.34e-9 /f^2 m/counts (40m/17285)

 These numbers were also reflected to C1:CAL-MICH_CINV and C1:CAL-MICH_A.
 C1:CAL-MICH_A_GAIN = 0.5 was used to take into account of LSC output matrix of MICH to BS being C1:LSC-OUTPUT_MTRX_8_2=0.5.

 - Attachment #2 shows the displacement spectrum of MICH (top) and LO PHASE (bottom). Brown MICH curve is when locked with AS55_Q and black MICH curve is when locked with BHD_DIFF. RMS of original and in-loop LO PHASE was estimated to be

 Original LO phase noise: 393 nm RMS (266 deg RMS)
 In-loop LO phase noise: 19.4 nm RMS (13 deg RMS)

Next:
 - Improve LO phase loops to reduce LO phase noise
 - Estimate LO phase noise contribution to MICH sensitivity

Attachment 1: Screenshot_2022-11-21_17-33-20_OLTF.png
Screenshot_2022-11-21_17-33-20_OLTF.png
Attachment 2: Screenshot_2022-11-21_17-45-25_MICHBHDDisplacement.png
Screenshot_2022-11-21_17-45-25_MICHBHDDisplacement.png
  17298   Tue Nov 22 10:29:31 2022 AnchalSummarySUSITMY Coil Strengths Balanced

I followed this procedure to balance the coil strengths on ITMY. The position sensor was created by closing PSL shutter so that IR laser is free running, and locking the green laser to YARM, this makes C1:ALS-BEATY_FINE_PHASE_OUT a position sensor for ITMY. The oplev channels C1:SUS-ITMY_OL_PIT_IN1 and C1:SUS-ITMY_OL_YAW_IN1 were used for PIT and YAW sensors. Everything else followed the procedure. The coil gains were changed as follow:

C1:SUS-ITMY_ULCOIL_GAIN :   1.036 -> 1.061
C1:SUS-ITMY_URCOIL_GAIN : -1.028 -> -0.989
C1:SUS-ITMY_LRCOIL_GAIN :   0.930 -> 0.943
C1:SUS-ITMY_LLCOIL_GAIN : -1.005  -> -1.007

I used this notebook and this diaggui to do this balancing.

  17303   Wed Nov 23 14:59:11 2022 PacoSummaryBHDBHD_DIFF sensitivity to BS dither with MICH Offset

[Yuta, Paco, Anchal]

We measured

(a) BHDC_DIFF sensitivity to BS dither for a set of MICH offsets.


Configurations

  • MICH locked with AS55_Q
    • The MICH offset was varied below
  • LO_PHASE locked with BH55_Q
    • Balanced DCPD_A and DCPD_B by applying a digital gain of 1.00 to DCPD_A
    • Changed the BH55 demod angle to 140.07 deg to minimize BH55_I
  • BS dither at 311.1 Hz
    • Use newly added HPC_BS Lockins to readback the demodulated signals

Results & Discussion

The analysis was done with the '/cvs/cds/rtcds/caltech/c1/Git/40m/scripts/CAL/BHD/BHD_DIFFSensitivity.ipynb' notebook.

Attachment #1 shows the main result showing the sensitivity of various demodulated error signals at 311.1 Hz for a set of 21 MICH offsets. We noted that if we didn't randomize the MICH offset scan, we observed a nonzero "zero crossing" for the offset.
Note that, although LO_PHASE loop was always on to control the LO phase to have zero crossing of BH55_Q, actual LO phase is not constant over the measurement, as MICH offset changes BH55_Q zero crossing.
When MICH offset is zero, LO_PHASE loop will control the LO phase to 0 deg (90 deg away from optimal phase), and BHDC_DIFF will not be sensitive to MICH, but when MICH offset is added, BHDC_DIFF start to have MICH sensitivity (measurement is as expected).
For BHDC_SUM, MICH sensitivity is linear to MICH offset, as it should be the same as ASDC, and does not depend on LO phase (measurement is as expected).
For BH55_Q, MICH sensitivity is maximized at zero MICH offset, but reduces with MICH offset, probably because LO phase is also being changed.


Attachment 1: BHDIFF_rand_SensvsMICHOffset.pdf
BHDIFF_rand_SensvsMICHOffset.pdf
  17309   Wed Nov 23 20:58:23 2022 yutaSummaryBHDBHD_DIFF sensitivity to BS dither with MICH Offset with different BH55 demodulation phases

[Anchal, Paco, Yuta]

Attachment #1 is the same plot as 40m/17303 but with MICH sensitivity for ASDC and AS55 also included (in this measurement, BH55 demodulation phase was set to 140.07 deg to minimize I fringe).
Y-axis is now calibrated in to counts/m using BS actuation efficiency 26.54e-9 /f^2 m/counts (40m/17285) at 311.1 Hz.
2nd X-axis is calibrated into MICH offset using the measured AS55_Q value and it's MICH sensitivity, 8.81e8 counts/m (this is somehow ~10% less than our usual value 40m/17294).
ASDC have similar dependence with BHDC_SUM on MICH offset, as expected.
AS55_Q have little dependence with MICH offset on MICH offset, as expected.

This plot tells you that even a small MICH offset at nm level can create MICH sensitivity for BHDC_DIFF, even if we control LO phase to have BH55_Q to be zero, as MICH offset shifts zero crossing of BH55_Q for LO phase.

Notebook: /opt/rtcds/caltech/c1/Git/40m/scripts/CAL/BHD/BH_DIFFSens_pydemod.ipynb

Attachment #2 is the same plot, but BH55 demodulation phase was tuned to 227.569 deg to have no MICH signal in BH55_Q (a.k.a measurement (c)).
In this case, LO phase will be always controlled at 0 deg (90 deg away from optimal), even if we change the MICH offset, as BH55_Q will not be sensitive to MICH.
In this plot, BHD_DIFF have little sensitivity to MICH, irrelevant of MICH offset, as expected.
MICH sensitivity for BH55_I is also constant, which indicate that LO phase is constant over this measurement, as expected.

Notebook: /opt/rtcds/caltech/c1/Git/40m/scripts/CAL/BHD/BH_DIFFSens_pydemod.ipynb

Attachment #3 is the same plot, but BH55 demodulation phase was tuned to 70 deg.
This demodulation phase was tuned within 5 deg to maximize MICH signal in BHD_DIFF with large MICH offset (20).
In this case, LO phase will be always controlled at 90 deg (optimal), even if we change the MICH offset, as BH55_Q will not be sensitve to LO carrier x AS sideband component of the LO phase signal.
In this plot, BHD_DIFF have high sensitivity to MICH, irrelevant of MICH offset (at around zero MICH offset it is hard to see because LO_PHASE lock cannot hold lock, as there will be little LO phase signal in BH55_Q, and measurement error is high for BHD_DIFF and BH55 signals).
MICH sensitivity for BH55_I and BH55_Q is roughly constant, which indicate that LO phase is constant over this measurement, as expected.

These plots indicate that BH55 demodulated at MICH dither frequency can be used to control LO phase robustly at 90 deg, under unknown or zero MICH offset.


Notebook: /opt/rtcds/caltech/c1/Git/40m/scripts/CAL/BHD/BH_DIFFSens_pydemod.ipynb

LO phase delay:
 From these measurements of demodulation phases, I guess we can say that phase delay for 55 MHz in LO path with respect to MICH path (length difference in PR2->LO->BHDBS and PR2->ITMs->AS->BHDBS) is

2*(227.569-70(5)-90)-90 = 45(10) deg

 This means that the length difference is (omegam=5*2*pi*11.066195 MHz)

c * np.deg2rad(45(10)+360) / omegam = 6.1(2) m   (360 deg is added to make it close to the design)

  Is this consistent with our design? (According to Yehonathan, it is 12.02 m - 5.23 m = 6.79 m)

  Attachment #4 illustrates signals in BH55.

Next:
 - Lock LO PHASE with BH55 demodulated at MICH dither frequency (RF+audio double demodulation), and repeat the same measurement
 - Finer measurement at small MICH offsets (~1nm) to see how much MICH offset we have
 - Repeat the same measurement with BH55_Q demodulation phase tuned everytime we change the MICH offset to maximize LO phase sensitivity in BH55_Q (a.k.a measurement (b)).
 - What is the best way to tune BH55 demodulation phase?

Attachment 1: BHDIFF_rand_SensvsMICHOffset_pydemod.pdf
BHDIFF_rand_SensvsMICHOffset_pydemod.pdf
Attachment 2: BHDIFF_rand_SensvsMICHOffset_pydemod_NoMICHinBH55Q.pdf
BHDIFF_rand_SensvsMICHOffset_pydemod_NoMICHinBH55Q.pdf
Attachment 3: BHDIFF_rand_SensvsMICHOffset_pydemod_BH55at70deg.pdf
BHDIFF_rand_SensvsMICHOffset_pydemod_BH55at70deg.pdf
Attachment 4: MICHBHD_BH55.pdf
MICHBHD_BH55.pdf
  17317   Mon Nov 28 16:53:22 2022 AnchalSummaryBHDF2A filters on LO1 LO2 AS1 and AS4

[Paco, Anchal]

I changed the script in /opt/rtcds/caltech/c1/Git/40m/scripts/SUS/outMatFilters/createF2Afilters.py to read the measured POS resonant frequencies stored in /opt/rtcds/caltech/c1/Git/40m/scripts/SUS/InMatCalc/resFreqs.yml instead of using the estimate sqrt(g/len). I then added Q = 3 F2A filters into FM1 output filter of LO1, LO2, AS1 and AS4 suspensions in anticipation of BHD locking scheme work.

  17319   Mon Nov 28 18:21:50 2022 PacoSummaryBHDBH44 prep

I checked the LSC rack to evaluate what we might need to generate 44 MHz rf in the hypothetical case we go from BH55 to BH44 (a.k.a. double RF demod scheme). There is an 11 MHz LO port labeled +16 dBm (measured 9 Vpp ~ 23 dBm actually) on the left hand side. Furthermore, there is an unused 55 MHz port labeled "Spare 55 LO". I checked this output to be 1.67 Vpp ~ +8.4 dBm. Anyways the 55 MHz doesn't look very nice; after checking it on the spectrum analyzer it seems like lower frequency peaks are polluting it so it may be worth checking the BH55 LO (labeled REFL 55) signal to see if it's better. Anyways we seem to have the two minimum LOs needed to synthesize 44 MHz in case we move forward with BH44.


[Paco, Yuta]

We confirmed the noisy 55 MHz is shared between AS55, BH55 and any other 55 MHz LOs. Looking more closely at the spectrum we saw the most prominent peaks at 11.06 MHz and 29.5 MHz (IMC and PMC nominal PM freqs). This 55 MHz LO is coming all the way from the RF distribution box near the IOO rack. According to this diagram, this 55 MHz LO should have gone through a bandpass filter; interestingly, checking the RF generation box spare 55 MHz the output is *cleaner* and displays ~ 17 dBm level... ??? Will continue investigating when we actually need this RF.

  17328   Wed Nov 30 20:01:08 2022 ranaSummaryCalibrationSingle arm cal with 5 lines

I don't think you need to record the excitations. They are just sine waves. The amplitude you can read off from the OSC screen. You just have to have the BEAT channel recorded and you can demod it to get the calibration. If the BEAT channel is calibrated in Hz, and you know the 40m arm length, then you're all done.

Quote:
 

Analysis

Basically, only the DARM line was recorded (DQ channs) so I modified the c1cal to store the SIG_OUT and DEMOD_I_IN1 channels for both BEATX and BEATY cal signals. This means I need to repeat this measurement. In the meantime I am also going to try and rerun calibrate the BEAT HZ transfer function.

 

  17329   Thu Dec 1 20:43:25 2022 AnchalSummaryCalibrationSingle arm cal with 5 lines

[Anchal, Paco]

We are doing this attempt again in following configuration:

  • PSL shutter is closed. (So IR laser is free running)
  • Beanote frequency between Y arm and Main laser is about 45 MHz.
  • Green laser on Y end is locked. Transmission is above 1.1 (C1:ALS-TRY_OUT)
  • All calibration oscillators are turned on and set to actuate ITMY. See screenshot attached.
  • The calibration model was changed to demodulate the C1:ALS-BEATY_FINE_PHASE_OUT channel insteald. We'll have DQ channels before mixing with oscillator, after mixing, and also after applying a 4th order 30 Hz butterworth filter.

Start time:

PST: 2022-12-01 20:44:23.982114 PST
UTC: 2022-12-02 04:44:23.982114 UTC
GPS: 1353991481.982114
 

Stop time:

PST: 2022-12-02 14:32:29.547603 PST
UTC: 2022-12-02 22:32:29.547603 UTC
GPS: 1354055567.547603

Attachment 1: SingleArmCalibration.png
SingleArmCalibration.png
  60   Sun Nov 4 23:22:50 2007 waldmanUpdateOMCOMC PZT and driver response functions
I wrote a big long elog and then my browser hung up, so you get a less detailed entry. I used Pinkesh's calibration of the PZT (0.9 V/nm) to calibrate the PDH error signal, then took the following data on the PZT and PZT driver response functions.:

  • FIgure 1: PZT dither path. Most of the features in this plot are understood: There is a 2kHz high pass filter in the PZT drive which is otherwise flat. The resonance features above 5 kHz are believed to be the tombstones. I don't understand the extra motion from 1-2 kHz.
  • Figure 2: PZT dither path zoom in. Since I want to dither the PZT to get an error signal, it helps to know where to dither. The ADC Anti-aliasing filter is a 3rd order butterworth at 10 kHz, so I looked for nice flat places below 10 KHz and settled on 8 kHz as relatively harmless.
  • Figure 3: PZT LSC path. This path has got a 1^2:10^2 de-whitening stage in the hardware which hasn't been digitally compensated for. You can see its effect between 10 and 40 Hz. The LSC path also has a 160 Hz low path which is visible causing a 1/f between 200 and 500 Hz. I have no idea what the 1 kHz resonant feature is, though I am inclined to point to the PDH loop since that is pretty close to the UGF and there is much gain peaking at that frequency.
Attachment 1: 071103DitherShape.png
071103DitherShape.png
Attachment 2: 071103DitherZoom.png
071103DitherZoom.png
Attachment 3: 071103LSCShape.png
071103LSCShape.png
Attachment 4: 071103DitherShape.pdf
071103DitherShape.pdf
Attachment 5: 071103DitherZoom.pdf
071103DitherZoom.pdf
Attachment 6: 071103LSCShape.pdf
071103LSCShape.pdf
Attachment 7: 071103LoopShape.pdf
071103LoopShape.pdf
  61   Sun Nov 4 23:55:24 2007 ranaUpdateIOOFriday's In-Vac work
On Friday morning when closing up we noticed that we could not get the MC to flash any modes.
We tracked this down to a misalignment of MC3. Rob went in and noticed that the stops were
still touching. Even after backing those off the beam from MC3 was hitting the east edge of
the MC tube within 12" of MC3.

This implied a misalignment of MC of ~5 mrad which is quite
large. At the end our best guess is that either I didn't put the indicator blocks in the
right place or that the MC3 tower was not slid all the way back into place. Since there
is such a strong stickiness between the table and the base of the tower its easy to
imagine the tower was misplaced.

So we looked at the beam on MC2 and twisted the MC3 tower. This got the beam back onto the
MC2 cage and required ~1/3 if the MC3 bias range to get the beam onto the center. We used
a good technique of finding that accurately: put an IR card in front of MC2 and then look
in from the south viewport of the MC2 chamber to eyeball the spot relative to the OSEMs.

Hitting MC2 in the middle instantly got us multiple round trips of the beam so we decided
to close up. First thing Monday we will put on the MC1/MC3 access connector and then
pump down.


Its possible that the MC length has changed by ~1-2 mm. So we should remeasure the length
and see if we need to reset frequencies and rephase stuff.
  62   Mon Nov 5 07:29:35 2007 ranaUpdateIOOFriday's In-Vac work
Liyuan recently did some of his pencil beam scatterometer measurements measuring not the
BRDF but instead the total integrated power radiated from each surface point
of some of the spare small optics (e.g. MMT, MC1, etc.).

The results are here on the iLIGO Wiki.

So some of our loss might just be part of the coating.
  63   Mon Nov 5 14:44:39 2007 waldmanUpdateOMCPZT response functions and De-whitening
The PZT has two control paths: a DC coupled path with gain of 20, range of 0 to 300 V, and a pair of 1:10 whitening filters, and an AC path capacitively coupled to the PZT via a 0.1 uF cap through a 2nd order, 2 kHz high pass filter. There are two monitors for the PZT, a DC monitor which sniffs the DC directly with a gain of 0.02 and one which sniffs the dither input with a gain of 10.

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

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

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

I measured the high frequency response of the loop DC monitor / DC drive to be flat.
Attachment 1: 07110_DithertoVmonAC_sweep2-0.png
07110_DithertoVmonAC_sweep2-0.png
Attachment 2: 071105_LSCtoVmonDC_sweep4-0.png
071105_LSCtoVmonDC_sweep4-0.png
Attachment 3: 07110_DithertoVmonAC_sweep2.pdf
07110_DithertoVmonAC_sweep2.pdf 07110_DithertoVmonAC_sweep2.pdf
Attachment 4: 071105_LSCtoVmonDC_sweep4.pdf
071105_LSCtoVmonDC_sweep4.pdf 071105_LSCtoVmonDC_sweep4.pdf
  68   Tue Nov 6 14:51:03 2007 tobin, robUpdateIOOMode cleaner length
Using the Ward-Fricke variant* of the Sigg-Frolov method, we found the length of the mode cleaner to be 27.0934020183 meters, a difference of -2.7mm from Andrey, Keita, and Rana's measurement on August 30th.

The updated RF frequencies are:
3  fsr =  33 195 439 Hz
12 fsr = 132 781 756 Hz
15 fsr = 165 977 195 Hz
18 fsr = 199 172 634 Hz
* We did the usual scheme of connecting a 20mVpp, 2 kHz sinusoid into MC AO. Instead of scanning the RF frequency by turning the dial on the 166 MHz signal generator ("marconi"), we connected a DAC channel into its external modulation port (set to 5000 Hz/volt FM deviation). We then scanned the RF frequency from the control room, minimizing the height of the 2 kHz line in LSC-PD11. In principle one could write a little dither servo to lock onto the 15fsr, but in practice simply cursoring the slider bar around while watching a dtt display worked just fine.
  69   Tue Nov 6 15:36:03 2007 robUpdateLSCXARM locked
Easily, after resetting the PSL Uniblitz shutters. There's no entry from David or Andrey about the recovery from last week's power outage, in which they could have indicated where the procedure was lacking/obscure. Tsk, tsk.
  76   Wed Nov 7 09:38:01 2007 steveUpdateVACrga scan
pd65-m-d2 at cc1 6e-6 torr
Attachment 1: pd65d2.jpg
pd65d2.jpg
  81   Wed Nov 7 16:07:03 2007 steveUpdatePSLPSL & IOO trend
1.5 days of happy psl-ioo with litle bumps in C1:PSL-126MOPA_HTEMP
Attachment 1: psl1.5dtrend.jpg
psl1.5dtrend.jpg
  82   Thu Nov 8 00:55:44 2007 pkpUpdateOMCSuspension tests
[Sam , Pinkesh]

We tried to measure the transfer functions of the 6 degrees of freedom in the OMS SUS. To our chagrin, we found that it was very hard to get the OSEMs to center and get a mean value of around 6000 counts. Somehow the left and top OSEMs were coupled and we tried to see if any of the OSEMs/suspension parts were touching each other. But there is still a significant coupling between the various OSEMs. In theory, the only OSEMS that are supposed to couple are [SIDE] , [LEFT, RIGHT] , [TOP1, TOP2 , TOP3] , since the motion along these 3 sets is orthogonal to the other sets. Thus an excitation along any one OSEM in a set should only couple with another OSEM in the same same set and not with the others. The graphs below were obtained by driving all the OSEMS one by one at 7 Hz and at 500 counts ( I still have to figure out how much that is in units of length). These graphs show that there is some sort of contact somewhere. I cant locate any physical contact at this point, although TOP2 is suspicious and we moved it a bit, but it seems to be hanging free now. This can also be caused by the stiff wire with the peek on it. This wire is very stiff and it can transmit motion from one degree of freedom to another quite easily. I also have a graph showing the transfer function of the longitudnal degree of freedom. I decided to do this first because it was simple and I had to only deal with SIDE, which seems to be decoupled from the other DOFs. This graph is similar to one Norna has for the longitudnal DOF transfer function, with the addition of a peak around 1.8 Hz. This I reckon could very be due to the wire, although it is hard to claim for certain. I am going to stop the measurement at this time and start a fresh high resolution spectrum and leave it running over night.

There is an extra peak in the high res spectrum that is disturbing.
Attachment 1: shakeleft.pdf
shakeleft.pdf
Attachment 2: shakeright.pdf
shakeright.pdf
Attachment 3: shakeside.pdf
shakeside.pdf
Attachment 4: shaketop1.pdf
shaketop1.pdf
Attachment 5: shaketop2.pdf
shaketop2.pdf
Attachment 6: shaketop3.pdf
shaketop3.pdf
Attachment 7: LongTransfer.pdf
LongTransfer.pdf LongTransfer.pdf LongTransfer.pdf
Attachment 8: Shakeleft7Nov2007_2.pdf
Shakeleft7Nov2007_2.pdf
Attachment 9: Shakeleft7Nov2007_2.png
Shakeleft7Nov2007_2.png
  83   Thu Nov 8 11:40:21 2007 steveUpdatePEMparticle counts are up
I turned up the psl HEPA filter to 100%
This 4 days plot shows why
Attachment 1: pslhepaon.jpg
pslhepaon.jpg
  87   Fri Nov 9 00:23:12 2007 pkpUpdateOMCX and Z resonances
I got a couple of resonance plots going for now. I am still having trouble getting the Y measurement going for some reason. I will investigate that tommorow. But for tonight and tommorow morning, here is some food for thought. I have attached the X and Z transfer functions below. I compared them to Norna's plots - so just writing out what I was thinking -

Keep in mind that these arent high res scans and have been inconviniently stopped at 0.5 Hz Frown.

Z case --

I see two small resonances and two large ones - the large ones are at 5.5 Hz and 0.55 Hz and the small ones at 9 Hz and 2 Hz respectively. In Norna's resonances, these features arent present. Secondly, the two large peaks in Norna's measurement are at 4.5 Hz and just above 1 Hz. Which was kind of expected, since we shortened the wires a bit, so one of the resonances moved up and I suppose that the other one moved down for the same reason.

X case --

Only one broad peak at about 3 Hz is seen here, whereas in Norna's measurement, there were two large peaks and one dip at 0.75 Hz and 2.5 Hz. I suspect that the lower peak has shifted lower than what I scanned to here and a high res scan going upto 0.2 Hz is taking place overnight. So we will have to wait and watch.

Pitch Roll and Yaw can wait for the morning.
Attachment 1: Xtransferfunc.pdf
Xtransferfunc.pdf Xtransferfunc.pdf Xtransferfunc.pdf
Attachment 2: Ztransferfunc.pdf
Ztransferfunc.pdf Ztransferfunc.pdf Ztransferfunc.pdf
  88   Fri Nov 9 09:37:55 2007 steveUpdatePSLhead temp hiccup
Just an other PSL-126MOPA_HTEMP hiccup.
The water chiller is at 20.00C
Attachment 1: headtempup.jpg
headtempup.jpg
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