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ID Date Author Type Categoryup Subject
  17366   Tue Dec 20 09:20:18 2022 PacoSummaryLSCFPMI locked and cal

[Anchal, Yuta, Paco]

Late elog (from yesterday) -- We locked FPMI, YAUX, and turned on calibration lines from gpstimes = 1355539386 to 1355539594 (lost lock because IMC unlocked angry)

We followed the steps in this elog and handed off from an electronic FPMI (POX, POY) to the RF one (REFL55 and AS55). We will continue this work today and try to finish a restore FPMI script to make it more robust.

  17367   Tue Dec 20 18:27:14 2022 AnchalSummaryLSCFPMI locked, DARM calibration data taken, FPMI BHD locked!

[Anchal, Paco, Yuta]

FPMI locked with BHD readout!!!

Paco and I figured the repeatable recipe for locking FPMI today. The settings are saved as snapshot file. In short, we first lock fake FPMI using POX+POY and POX-POY and then locking MICH to REFL55_Q. We make sure there are no offsets in AS55Q or REFL55Q. Then we handoff CARM and DARM loops to 0.496*REFL55_I and 2.617*AS55_Q by changing gains on A and B paths simultaneously with tramp time of 5s. WE have pushed new measurements of CARM, DARM and MICH loop OLTFs to measurement repo.

We turned on 5 oscillators all sending calibration lines to ITMY at different frequencies to calibrate DARM readout. WE took this data for about 90 minutes and then decided to try locking FPMI with BHDC DIFF.

A simple handoff to 0.68*BHDC_DIFF at error point for DARM loop worked. The OLTF for DARM loop remained the same.

I need to run now, so more detailed elog will come later.

On another news, this was last day of Tega, a warm farewell to him.

Attachment 1: PXL_20221221_013126861.MP.jpg
  17369   Wed Dec 21 12:18:44 2022 PacoSummaryLSCFPMI locked, but FPMI BHD not locked

[Yuta, Paco]

We tried restoring the FPMI BHD readout from yesterday but failed. Below is a summary of what we did.


  1. Align arms, MICH and LO (using ITMY single bounce).
  2. Lock both CARM and DARM with POX/POY to restore the "electronic" FPMI.
  3. Lock MICH with REFL55_Q.
  4. Handoff DARM to AS55_Q and CARM to REFL55_I.
  5. Lock LO_PHASE using BH55_Q
  6. Balance BHD_DCPD to remove offset in BHD_DIFF
  7. Measure the C1:LSC-BHDC_DIFF_OUT / C1:LSC-AS55_Q_ERR ratio to get the DARM content in BHD DIFF.
  8. Attempt DARM control handoff from AS55_Q to BHDC_DIFF  --- this step didn't work today despite our several attempts.

We found LO fringe alignment to be really important, as sometimes we would try to calibrate the DARM content of BHD DIFF and found almost no coherence between AS55_Q and BHD_DIFF, but after realigning the coherence was increased and the lock was better. Another difference with respect to yesterday was the sign flip implied by the measured ratio from step 7.

Calibrated FPMI noise spectra

In anticipation to restoring FPMI BHD, we took a calibrated FPMI noise spectra (error and control point). The saved diaggui template that produces Attachment #1 is on /cvs/cds/rtcds/caltech/c1/Git/40m/measurements/LSC/FPMI/FPMI_calibrated_noise.xml Our calibration was based on sensing matrix measuring the DARM content on AS55_Q which was 1 / (2.617 * 3.64e11 counts/m) =  1.0497e-12 m/count, and the (balanced) ETM plant = 10.91e-9 / f^2 m/counts.

Next steps

Sadly we couldn't take a FPMI BHD calibrated noise spectra, but things to look into next time are

  • Take TFs for FPMI CARM, DARM and MICH loops. We skipped this today, perhaps wrongfully so.
  • Measure the FPMI sensing matrix to check demod phases and optical gains (related to the above).
Attachment 1: FPMI_calibrated_noise_20221221.pdf
  17392   Wed Jan 11 16:56:57 2023 yutaSummaryLSCFPMI BHD recovered, LO phase noise not limiting the sensitivity

[Paco, Yuta]

We recovered FPMI BHD, and sensitivity was estimated. High frequency sensitivity is improved by an order of magnitude compared with AS55 FPMI.
We also estimated the contribution from LO phase noise, and found that LO phase noise is not limiting the sensitivity.

Locking sequence:

1. Lock electronic FPMI

 - 0.5 * POX11_I - 0.5 * POY11_I
 - DARM filter module, FM4,5 for acquisition, FM1,2,3,6,8 triggered, C1:LSC-DARM_GAIN = 0.015 (gain lowered from BHD FPMI in December (was 0.02) to have more gain margin)
 - Actuation on 0.5 * ETMX - 0.5 * ETMY
 - UGF ~ 150 Hz

 - 0.5 * POX11_I + 0.5 * POY11_I
 - CARM filter module, FM4,5 for acquisition, FM1,2,3,6,8 triggered, C1:LSC-CARM_GAIN = 0.012
 - Actuation on -0.734 * MC2

2. Lock MICH

 - 1.1 * REFL55_Q
 - MICH filter module, FM4,5,8 for acquisition, FM2,3,6 triggered, C1:LSC-MICH_GAIN = +10
 - Actuation on 0.5 * BS
 - UGF ~35 Hz (Attachment #1)

3. Hand over to real DARM/CARM

 - 2.617 * AS55_Q

 - 0.496 * REFL55_I
 - UGF ~200 Hz (Attachment #2)

4. Lock LO_PHASE

 - 1 * BH55_Q (demod phase: -110 deg; this was chosen by hand to maximize fringe in BH55_Q when FPMI is locked. This seemed to make more robust LO_PHASE lock, compared with December)
 - Acuation on 1 * LO1
 - UGF ~110 Hz (Attachment #3)

5. Hand over to BHD_DIFF

 - -1.91 * BHD_DIFF (ratio between AS55_Q to BHD_DIFF was measured with a DARM line at 575.125 Hz, which was measured to be -0.455; BHD_DIFF was zeroed by balancing A and B before the measurement)
 - UGF ~150Hz (Attachment #4)

Measured sensing matrix:


Sensing matrix with the following demodulation phases (counts/counts)
{'AS55': -168.5, 'REFL55': 92.32, 'BH55': -110.0}
Sensors       DARM @307.88 Hz           CARM @309.21 Hz            MICH @311.1 Hz        LO1 @315.17 Hz           
AS55_I       (-0.35+/-1.44)e-02        (+3.23+/-1.09)e-02        (-0.18+/-9.84)e-03    (+0.02+/-1.33)e-03    
AS55_Q       (-0.45+/-3.48)e-02        (-0.19+/-1.23)e-02        (+0.05+/-1.43)e-03    (-0.02+/-2.03)e-04    
REFL55_I     (+0.05+/-1.31)e-01        (+4.51+/-0.07)e-01        (-0.03+/-3.44)e-02    (+0.11+/-1.01)e-03    
REFL55_Q     (-0.39+/-4.74)e-04        (-1.36+/-0.50)e-03        (+0.16+/-2.80)e-04    (+0.10+/-4.92)e-05    
BH55_I       (-1.90+/-5.00)e-03        (+0.80+/-8.82)e-03        (-0.50+/-2.29)e-03    (-4.61+/-9.52)e-04    
BH55_Q       (-0.31+/-4.86)e-02        (-3.13+/-3.04)e-02        (-0.06+/-1.07)e-02    (-1.42+/-2.11)e-03    
BHDC_DIFF    (-5.56+/-0.21)e-02        (+0.10+/-1.64)e-02        (+0.10+/-1.40)e-03    (+0.77+/-2.27)e-04    
BHDC_SUM     (+1.75+/-3.90)e-03        (-1.22+/-3.22)e-03        (-0.35+/-1.52)e-03    (-0.36+/-6.42)e-04


Sensing matrix with the following demodulation phases (counts/m)
{'AS55': -168.5, 'REFL55': 92.32, 'BH55': -110.0}
Sensors       DARM @307.88 Hz           CARM @309.21 Hz           MICH @311.1 Hz        LO1 @315.17 Hz           
AS55_I       (-0.30+/-1.25)e+11        (+2.18+/-0.73)e+11       (-0.07+/-3.59)e+10    (+0.08+/-5.02)e+09    
(-0.39+/-3.03)e+11        (-1.27+/-8.32)e+10       (+0.20+/-5.23)e+09    (-0.06+/-7.66)e+08    
REFL55_I     (+0.04+/-1.14)e+12        (+3.05+/-0.05)e+12       (-0.01+/-1.26)e+11    (+0.42+/-3.82)e+09    
REFL55_Q     (-0.34+/-4.12)e+09        (-9.20+/-3.37)e+09       (+0.06+/-1.02)e+09    (+0.04+/-1.86)e+08    
BH55_I       (-1.65+/-4.34)e+10        (+0.54+/-5.95)e+10       (-1.83+/-8.36)e+09    (-1.74+/-3.59)e+09    
BH55_Q       (-0.27+/-4.23)e+11        (-2.11+/-2.05)e+11       (-0.21+/-3.91)e+10    (-5.36+/-7.98)e+09    
BHDC_DIFF    (-4.83+/-0.18)e+11        (+0.07+/-1.11)e+11       (+0.35+/-5.09)e+09    (+2.90+/-8.56)e+08    
BHDC_SUM     (+1.52+/-3.39)e+10        (-0.82+/-2.17)e+10       (-1.29+/-5.56)e+09    (-0.14+/-2.42)e+09

NOTE that some of sensing matrix element (e.g. DARM to AS55_Q) is wrong, because of ill defined sign in C1:CAL-SENSMAT_XXXX_XXXX_AMPMON channels.

Locked GPS times:
 - 1357511737 to 1357513050
 - 1357513448 to 1357518188 (intentionally unlocked)

Sensitivity estimate:
 - See Attachment #5 and #6 (high frequency zoomed), dashed traces with darker colors are of AS55_Q FPMI from 40m/17369.
 - DARM_IN1 was calibrated using DARM content in BHD_DIFF, with 1 / (1.91 * 4.83e11 counts/m) = 1.086e-12 m/counts (which should be similar to DARM_IN1 calibration for AS55_Q, because we are balancing the error signals going to DARM_IN1, and it is as expected; see 40m/17369).
 - DARM_OUT calibration is the same as 40m/17369; ETM plant = 10.91e-9 / f^2 m/counts.
 - LO phase noise was estimated using BH55_Q, with the collowing calibration factor (BH55_Q calibrated into LO1 motion, into BHD_DIFF, and then into DARM).

1/5.36e9*2.9e8/4.83e11 = 1.15e-13 m/counts

 - Seismic noise was estimated using C1:IOO-MC_F_DQ, with the same calibration factor found in 40m/16975.
 - Dark noise was estimated using DARM_IN1 when the PSL shutter is closed.

 - Sensitivity below ~10 Hz is probably limited by seismic noise
 - Noise above 1 kHz might be limited by dark noise of BHD_DIFF, but not below 1 kHz. For AS55_Q FPMI, sensitivity above ~300 Hz was limited by dark noise.
 - LO phase noise is not limiting the sensitivity, from the estimated noise using BH55_Q.
 - Both BH55_Q and BHD_DIFF have funny structure like forest above ~100 Hz. This might be from suspensions in the AS path and LO path to BHD. It could also be that calibration lines for measuring sensing matrix were too much (BHD FPMI sensitivity was measured with calibration lines around ~310 Hz on).

 - Update the c1cal model to put correct signs to C1:CAL-SENSMAT_XXXX_XXXX_AMPMON channels.
 - Measure BHD FPMI sensitivity with calibration lines off.
 - Find better LO phase to improve the sensitivity.
 - Lock LO phase with RF+audio and RF44 and compare the sensitivity.
 - Move on to PRFPMI BHD.

Attachment 1: Screenshot_2023-01-11_16-17-16_MICH.png
Attachment 2: Screenshot_2023-01-11_16-12-40_CARM.png
Attachment 3: Screenshot_2023-01-11_16-21-40_LOPHASE.png
Attachment 4: Screenshot_2023-01-11_16-10-54_DARM.png
Attachment 5: FPMI_calibrated_noise_20230111.pdf
Attachment 6: FPMI_calibrated_noise_20230111_HF.pdf
  17395   Thu Jan 12 12:00:09 2023 PacoSummaryLSCFPMI BHD sensitivity curve with higher resolution upto 6.9 kHz

Here's the same sensitivity plot from yesterday (40m/17392), but with higher frequency resolution, upto 6.9 kHz, using GPS times from yesterday.
Now curves from FPMI with AS55_Q are also from yesterday, just before switching to BHD, so it will be more direct comparison

Attachment 1: FPMI_calibrated_noise_20230112.pdf
Attachment 2: FPMI_calibrated_noise_20230112_HF.pdf
  17399   Fri Jan 13 14:20:34 2023 yutaSummaryLSCCalibration friendly FPMI BHD

[Paco, Yuta]

Gains in DARM are corrected to make it more calibration friendly.

DARM error signals
 - 0.19 * POX11_I - 0.19 * POY11_I
 - 1 * AS55_Q
 - -0.455 * BHD_DIFF (needs to be checked if LO phase is different)

DARM gain:
 - C1:LSC-DARM_GAIN = 0.04 (it was 0.015 to have UGF of ~150 Hz)

Online calibration:
 - FM2 for C1:CAL-DARM_CINV was turned on, which is a calibration for AS55_Q in FPMI; 1 / (3.64e11 counts/m) = 2.747e-12 m/counts (see sensing matrix below; consistent with 40m/17369).
 - FM2 for C1:CAL-DARM_A was updated to 10.91e-9 (40m/16977).
 - C1:CAL-DARM_W_OUT will be our calibrated FPMI displacement in meters. This is correct with BHD_DIFF locking, if the BHD_DIFF is balanced with AS55_Q before DARM_IN1.

FPMI sensitivity:
 - Attached plot shows the sensitivity of FPMI with AS55_Q and BHD_DIFF, plotted together with their dark noise.
 - The sensisitivty was measured with calibration lines off and notches off, which removed the forest of lines we saw on Jan 11 (40m/17392).

FPMI sensing matrix:
 - Attached is a screenshot of uncalibrated sensing matrix MEDM screen. Audio demodulation phase for DARM was tuned to have stable sign.
 - The following is calibrated sensing matrix measured today with FPMI locked with AS55_Q. BH55 and BHD_DIFF have large uncertainties because LO_PHASE locking is not stable.

Sensing matrix with the following demodulation phases (counts/m)
{'AS55': -168.5, 'REFL55': 92.32, 'BH55': -110.0}
Sensors       DARM @307.88 Hz           CARM @309.21 Hz           MICH @311.1 Hz           LO1 @315.17 Hz           
AS55_I       (-3.28+/-0.90)e+11 [90]    (-0.05+/-2.53)e+11 [0]    (+0.47+/-2.14)e+10 [0]    (-0.06+/-1.76)e+09 [0]    
AS55_Q       (-3.64+/-0.08)e+11 [90]    (-0.09+/-8.30)e+10 [0]    (-0.28+/-2.24)e+09 [0]    (+0.12+/-1.16)e+08 [0]    
REFL55_I       (+0.07+/-1.24)e+12 [90]    (+3.32+/-0.06)e+12 [0]    (-0.01+/-1.39)e+11 [0]    (+0.00+/-1.12)e+09 [0]    
REFL55_Q       (-0.98+/-2.46)e+09 [90]    (-4.68+/-2.04)e+09 [0]    (+0.08+/-1.00)e+09 [0]    (+1.73+/-5.69)e+07 [0]    
BH55_I       (-6.84+/-2.47)e+11 [90]    (+0.43+/-2.32)e+11 [0]    (-0.33+/-6.21)e+10 [0]    (-2.51+/-8.09)e+09 [0]    
BH55_Q       (+5.68+/-1.57)e+11 [90]    (-0.17+/-2.52)e+11 [0]    (-0.46+/-4.39)e+10 [0]    (+0.73+/-5.01)e+09 [0]    
BHDC_DIFF       (-2.48+/-3.47)e+11 [90]    (-0.09+/-1.99)e+11 [0]    (+1.56+/-4.11)e+10 [0]    (-0.49+/-6.78)e+09 [0]    
BHDC_SUM       (-2.12+/-1.84)e+10 [90]    (+0.35+/-1.44)e+10 [0]    (-1.30+/-4.18)e+09 [0]    (-0.03+/-8.17)e+08 [0]  

Current status:
 - After locking FPMI BHD to get the FPMI sensitivity today, we are struggling to re-lock again. LO_PHASE locking is glitchy today for some reason. To be investigated.

Attachment 1: Screenshot_2023-01-13_14-55-34.png
Attachment 2: FPMI_calibrated_noise_20230113.pdf
  17400   Fri Jan 13 18:54:59 2023 yutaSummaryLSCInvestigations of LO phase locking in FPMI BHD

[Paco, Yuta]

After several hours of unattended IFO, we realigned the IFO and somehow BH55_Q error signal looked better, LO_PHASE locking was more robust, and we could lock FPMI BHD.

Sensing matrix:
 - Attached #1 is the sensing matrix with FPMI BHD locked, with LO_PHASE locked with BH55_Q using AS4, and below is the calibrated one.

Sensing matrix with the following demodulation phases (counts/m)
{'AS55': -168.5, 'REFL55': 92.32, 'BH55': -110.0}
Sensors       DARM @307.88 Hz           CARM @309.21 Hz           MICH @311.1 Hz           LO1 @315.17 Hz           
AS55_I       (+0.43+/-2.22)e+11 [90]    (+5.26+/-1.26)e+11 [0]    (-0.15+/-5.88)e+10 [0]    (+0.05+/-1.94)e+09 [0]    
AS55_Q       (-3.73+/-0.19)e+11 [90]    (-0.09+/-1.06)e+11 [0]    (+0.21+/-6.82)e+09 [0]    (-0.24+/-2.41)e+08 [0]    
REFL55_I       (+0.08+/-1.17)e+12 [90]    (+3.14+/-0.07)e+12 [0]    (-0.01+/-1.31)e+11 [0]    (+0.07+/-1.03)e+09 [0]    
REFL55_Q       (+0.51+/-1.09)e+10 [90]    (+1.80+/-2.35)e+10 [0]    (+0.01+/-1.44)e+09 [0]    (-0.79+/-5.41)e+07 [0]    
BH55_I       (+1.20+/-0.34)e+11 [90]    (+0.26+/-1.07)e+11 [0]    (-0.04+/-1.33)e+10 [0]    (-1.07+/-1.82)e+09 [0]    
BH55_Q       (+1.12+/-1.52)e+11 [90]    (-3.40+/-1.98)e+11 [0]    (-0.01+/-4.16)e+10 [0]    (-5.55+/-1.66)e+09 [0]    
BHDC_DIFF       (+6.95+/-0.25)e+11 [90]    (+0.01+/-1.60)e+11 [0]    (-0.70+/-4.49)e+09 [0]    (+4.24+/-4.14)e+08 [0]    
BHDC_SUM       (+7.06+/-2.64)e+10 [90]    (-0.32+/-3.24)e+10 [0]    (+0.05+/-4.26)e+09 [0]    (+1.30+/-6.33)e+08 [0]    

 - We are not sure why BH55_Q error signal got better. Peak to peak amptidue of BH55_Q when LO_PHASE is not locked is at around 800 (even if LO_PHASE locking cannot be stably locked), but when we couldn't lock LO_PHASE stably, it was noisier. This suggests that BHD alignment is not bad.
 - Attachment #2 shows the spectrum of BHDC_DIFF, BH55_Q (measured at LO_PHASE_IN1) and AS55_Q when FPMI is locked with AS55_Q, and LO_PHASE is locked with BH55_Q. Dashed darker curves are when we could not lock LO_PHASE stably. You can see broad noise in BH55_Q at around 60 Hz and its harmonics when it is noisy, but they are not present when LO_PHASE can be locked stably. Also, AS55_Q stays the same, which suggests that the cause is not in FPMI to AS55, but in BHD path to BH55.

Sensitivity comparison with different LO_PHASE locking actuator:
  - We compared FPMI sensitivity with LO_PHASE locked with LO1 (red) vs with AS4 (orange). Didn't change, as expected (Attachment #3).

 - Investigate what is causing noisy BH55. Is it FPMI alignment, BHD alignment, suspensions in LO/AS paths, or electronics?
 - Try locking LO_PHASE with an offset to BH55_Q to see if BHD_DIFF sensitivity to DARM changes, and to see if we can reduce BHD_DIFF dark noise contribution to FPMI sensitivity
 - Try BH55+audio and BH44 to lock LO_PHASE.

Attachment 1: Screenshot_2023-01-13_18-41-48_SensMat_FPMIBHD.png
Attachment 2: BHD_DARM_Sensors_20230113.pdf
Attachment 3: FPMI_calibrated_noise_20230113_LO1vsAS4.pdf
  17428   Thu Jan 26 23:33:19 2023 KojiUpdateLSCEP30-2 Epoxy bonding for Yuta

@OMC Lab
EP30-2 Epoxy bonding of V beam dumps for LSC PDs.

- Supplied 1"x0.5" glass pieces from the stock in the OMC lab.
- The black glass pieces were cleaned by IPA / Aceton / Aceton+Cotton Qtip scrub / First Contact
- 3 beam dumps are built. They require ~24 hrs to get cured.

=> Handed to Yuta on Jan 27, 2023

Attachment 1: PXL_20230127_053113856.jpg
Attachment 2: PXL_20230127_053145432.jpg
  17135   Thu Sep 8 11:54:37 2022 JCConfigurationLab OrganizationLab Organization

The arms in the 40m laboratory have now been sectioned off. Each arm has been divided up into 15 sections. Along the Y arm, the section are labelled "Section Y1 - Section Y15". For the X arm, they are labelled "Section X1- Section X15". Anything changed or moved will now be updated into the elog with their appropriate section.


Below is an example of Section X6.

Attachment 1: 1A7026BC-82A9-49E9-BA22-1A700DFEC5D2.jpeg
Attachment 2: 2A904809-82F0-40C0-B907-B48C3A0E789E.jpeg
Attachment 3: CB4B8591-B769-454D-9A16-EE9176004099.jpeg
  17136   Thu Sep 8 12:01:02 2022 JCConfigurationLab OrganizationLab Organization

The floor cable cover has been changed out for a new one. This is in Section X11.

Attachment 1: F41AD1DA-29E9-4449-99CB-5F43AE527CA6_1_105_c.jpeg
Attachment 2: FF5F2CE8-85E8-4B6F-8F8A-9045D978F670.jpeg
  17187   Thu Oct 13 14:46:34 2022 JCUpdateLab OrganizationLab Cleanup 10/12/2022

During Wednesday’s lab clean up, we made a ton of progress in organization. Our main focus was to tackle CDS debris from the ongoing upgrade. We proceeded with the following tasks.

  • Loop the OneStop Cables and mark ‘good’ or ‘bad’.
  • Clean materials from the PD testing table.
  • Removed the SuperMicro boxes from the lab
  • Vacuum area organization.
  • Remove old plastic containers from the laboratory.
  • Relocate Koji’s electronics underneath Y-Arm
  • Arrange cabling to the TestStand and create clearance to the Machine Shop/Laboratory exit.

Attachment #2 shows that all the CDS equipment has been relocated behind Section X3 of the X-Arm.

Attachment 1: IMG_6356.JPG
Attachment 2: IMG_6358.JPG
  17188   Thu Oct 13 19:06:42 2022 KojiUpdateLab OrganizationLab Cleanup 10/12/2022

I have moved the following electronics / components to "Section Y10 beneath the tube"

  • IQ Demod Spares D0902745 (Components)
  • Sat Box / HAM-A 40m parts D08276/D110117
  • 16bit DAC AI Rear PCB D070101-v3
  • D1900163 HV COIL DRIVER
  • Ribbon Cables for Chassis (Cardboard box)
  • Chassis DC Breaker Switches (Cardboard box)
  • Triplett HDMI displays (x3) / Good for portable CCD monitors / PC monitors. Battery powered!
  • ISC Whitening BI Config Boards D1001631/D1900166
  • AA/AI Untested D070081
  • WFS Interface / Soft Start D1101865/D1101816
  • Internal Wiring Kit Cable Spools
  • ISC Whitening / Interface D1001530 / D1002054
  • aLIGO WFS Head D1101614
  • Internal Wiring Kit (Large Plastic Box)
  • Front/Rear Panels (Large Plastic Box)
  • HV Coil Driver Test Kit / Spare PA95s (Large Plastic Box)


  17229   Fri Nov 4 15:43:05 2022 JCUpdateLab OrganizationNew Toolbox Organization

The new tool box has came in! I have spent serious time organizing these tools and making it look pretty, so please take care of it! A few things I would like to note.

  • The tool box has a power strip, so this is now where we will be charging the power tools. There is also a selected cabinet for the fully charged batteries, bits, and the power tools themselves. 
  • The cart next to the tool box had to turned 90 degrees in order to fit the tool box in. While moving this, I noticed this cart is piled with random stuff, let’s tackle this on Wednesdays clean up.
  • The tools from this tool box are specifically assigned to the VERTEX area (and the X-End until we get another toolbox.) Please return all the tools in their right tool box and cabinet after usage. 
  • The heavier duty equipment such as pipe wrenches, hammers, and power tools will remained stored here in the bottom cabinets. 

Hope you all like it!

Attachment 1: IMG_6405.JPG
  8331   Fri Mar 22 01:28:56 2013 ManasaUpdateLasersBeam profile of NPRO from ATF

The NPRO from ATF has been installed on the POY table.

I have been making measurements to characterize the beam profile of this laser. I am using an AR coated laser window as a beam sampler at 45deg and the razor blade technique to measure the beam size along z. Details of the procedure along with analysis and results from this will follow.

  231   Thu Jan 10 00:12:01 2008 tobinSummaryLockingDR
[John, Tobin, Rana]

1. We found SUS_BS_SENSOR_UL to have a ratty signal and low DC value. Twiddling the cables at the BS satellite amplifier and vacuum feedthrough brought the signal back (to 0.667V), but it is still spiky, spiking up to a couple times per second. Rana suggested that these spikes might be scattered YAG laser light (as hypothesized in August). The spikes go away when we misalign the PRM or either ITM, and when we unlock the mode cleaner, lending credance to this theory. SUS_BS_SENSOR_UR also spikes, but much less frequently. We turned off C1:SUS-BS_ULSEN_SW2 and continued.

2. After dither alignment the oplev beams were centred and we were able to lock DRM plus either arm reliably (however locking in this state broke ./drstep_bang at the first ``Going DD''). We ran scripts/DRFPMI/bang/nospring/drdown_bang and were subsequently able to lock DRFPMI (i.e., full IFO) a couple times.

3. To do: Debug ./drstep_bang with just the DRM (no arms).
  313   Tue Feb 12 16:39:52 2008 robUpdateLockingreport

Did some locking work on DRFPMI on sunday and (with John) on monday nights. So far progress has not been terribly encouraging.

Problems include the DD_handoffs not working and the CARM->MCL handoff not working so well. To get around the DD signals trouble, I decided for now to just ignore 67% of the DD signals. We should be able to run with PRC & MICH on single demod signals, and SRC on a DD signal. This seems to work well in a DRMI state, and it also works well in a DRMI+2ARMs state.

The CARM->MCL handoff actually works, but it doesn't take kindly to the AO path and it doesn't work very stably. I guess this was always the most fragile part of the whole locking procedure, and it's fragility is really coming to light now. Investigation continues.
  362   Thu Mar 6 00:17:37 2008 robUpdateLockingDD handoff working
Got the DD (double demod) handoff scripts working tonight, with just the DRMI. So, now acquisition with the single demod signals is working well, and handoffs to all double demod signals using the input matrix ramping worked several times with the scripts. Up next will be more work with the DRM+ARMs.
  366   Mon Mar 10 02:05:08 2008 robUpdateLockingDRMI+2ARMs working better

Some encouraging progress on the locking front tonight. After the work on the DRM loops last week and a review of the settings for initial lock acquisition (loop gains, tickle amplitude, filter states, so on), the DRMI+2ARMS locking is working pretty well. That's to say, it takes from 5-15 minutes generally for the IFO to lock in the offset CARM state, with the arm powers at 0.5. It's then possible to raise the arm powers slightly, and handing off control of CARM to MCL works at low power, but engaging the AO path (using PO_DC as an error signal) is not working so well. Taking swept sines indicates that the PO_DC should be a good error signal. The next good thing to try might be just using PO_DC as an error signal for the length path, without using the AO path at all, to see if it's something in the hardware.
  442   Thu Apr 24 14:10:26 2008 robUpdateLockinglocking work
Rob, Johnnie

We made some progress on locking last night (Wed night), namely that we were able to handoff (briefly) the CARM-MCL path the REFL-DC error signal. We tried this because we suspect that the reason the PO-DC is not a good CARM error signal is because at low powers, the dc light level in the recycling cavity is dominated by the +f2 RF sideband. Thus, REFL-DC should work a bit better at low powers, which it did. It wasn't super stable, though, so this will require a bit of work to make the transition reliable & stable. The next things to work on include setting the AO path gain properly and possibly going to higher arm powers before handing off (thus increasing the discriminant).

Another thing we found is that the alignment scripts are not working in an ideal fashion. Running the alignment scripts for the two arms (XARM & YARM) leaves the Michelson badly misaligned, making it impossible to get good DRM alignment. This will have to be fixed.
  531   Thu Jun 12 01:51:23 2008 robUpdateLockingreport
rob, john

We've been working (nights) on getting the IFO locked this week. There's been fairly steady incremental progress each night, and tonight we managed to control CARM(MCL) using PO-DC, with the CARM(AO) path also on PO-DC. In the past, reaching this state has usually meant we're home free, as we could just crank the gain on the common mode servo and merrily reduce the CARM offset. Tonight, however, this state has been very twitchy, and efforts to ramp up the gain have been unsuccessful.

I've attached a diagram which I hope makes clear where we are in the stages of lock acquisition.
Attachment 1: lock_control_sequence.png
  532   Thu Jun 12 15:09:33 2008 alanUpdateLockingreport
Rob: Awesome figure. As you can imagine, I have lots of questions, and hope that you will consider this figure to be the beginning, leading to ever-more detailed versions. But for now, I just want to ask whether you understand *what* is twitchy, and what the twitchiness does to prevent you from taking this further?
  533   Thu Jun 12 15:55:15 2008 robUpdateLockingreport

Rob: Awesome figure. As you can imagine, I have lots of questions, and hope that you will consider this figure to be the beginning, leading to ever-more detailed versions. But for now, I just want to ask whether you understand *what* is twitchy, and what the twitchiness does to prevent you from taking this further?

I definitely don't understand what's twitchy, but I have suspicions. Tonight we'll try to start by revisiting the other loops (the non-CARM loops) and see how they're dealing with the changing power levels. It may be that the DARM loop is going unstable due to gain variations (due to either increasing power or to rotation of demod phase) or it could be the PODD (or SPOB) saturating with increased power in the recycling cavity. I just hope the glitchiness doesn't have a digital origin.
  568   Wed Jun 25 13:56:56 2008 JohnSummaryLockingTuesday night locking
Rob, John

Worked to try and reduce the CARM offset using the dc arm transmissions before changing to SPOB DC. This proved somewhat unsuccessful, the offset couldn't be reduced to more than five (arms storing 5x more power than single arm cavity lock).
  573   Thu Jun 26 12:30:40 2008 JohnSummaryLockingCARM on REFL_DC

Try REFL_DC as the error signal for CARM rather than PO_DC.


The PO signal is dominated by sideband light when the arms are detuned so that any misalignment in the recycling cavity introduces spurious signals. Also, the transfer function from coupled cavity excitation to REFL signal is not so steep and hence REFL should give a little more phase. Finally, the slope of the REFL signal should make it easier to hand over to RF CARM.


The REFL signal showed no clear improvement over PO signals. We've gone back to PO.

During the night we also discovered that the LO for the MC loop is low.
  582   Fri Jun 27 14:36:39 2008 JohnSummaryLocking 
Rob, Yoichi, John

Some progress last night:

Switched back to SPOB_DC for CARM.

Shaped the MC LSC loop to reduce excess noise in the 20-30Hz band. Likely the most significant change.
Could this be due to fan noise from the laptop on the SPOB table?

Brought in the AO path earlier (at low gain).

Reduced offset to 6 and increased MC gain before handing off to SPOB. Ramped up AO and MC gain then switched off the
moving zero.

Looks like PD11 is the most promising candidate for RF CARM although the demod phase needs attention.
Attachment 1: gettingcloser.png
  623   Wed Jul 2 13:56:10 2008 Rob, Yoichi, JohnUpdateLocking24.5 Hz resonance
Work continues on trying to reduce the CARM offset using dc signals from PO_DC. Got up to arm powers of
~35 last night.

We found that progress was stymied by an oscillation around 24 Hz. This oscillation was clearly visible
in the intensity of the light at REFL, PO and TrX.

Initially we suspected that this oscillation was due to an instability in the CARM loop. We attempted to
solve the problem by tuning the crossover frequncy of the AO and MC_L paths and shaping the MC_L loop to
reduce the impact of the 24 Hz noise.

After some quick tests we found that the 24 Hz signal was present even when dc CARM was used. It appears
that the peak is in fact due to a SOS mechanical resonance. We currently suspect a roll mode.

We're going to check that PRC, MICH and DARM have filters to attenuate the 24 Hz line. We'll also look at the
SUS_POS bandstop filters to see where they are centred.

The ISS was behaving strangely again. Constantly saturated at 5dB of gain. Someone needs to look a this.
Attachment 1: locking080702.png
  630   Thu Jul 3 13:12:32 2008 Rob, Yoichi, JohnUpdateLockingMore oscillations
Bounce/ roll filters were added to the short degrees of freedom to reduce the effect of the 24Hz line seen on Tuesday night.

However last night saw the arrival of a new oscillation at ~34Hz. This may be the second harmonic of the MOS roll mode. Reducing the arm offset would cause this oscillation to ring up and break the lock (first plot). This effect was repeatable.

No signal was seen in the oplevs or osems which leads us to rule out alignment problems, at least for now.

Although one can clearly see DARM_ERR increasing as arm power increases adding a resonant gain in the DARM loop had no effect.

We also noticed that x arm transmission was significantly more noisy than the Y (second plot). And showed greater coherence with the increase in DARM noise. Investigations showed that the PD was not the source of the difference.

Turning up the MC gain seems to help a little.

We're now looking at POX as a candidate for RF_CARM (third plot).
Attachment 1: LOL.png
Attachment 2: NoisyX080702.png
Attachment 3: POXforCARM080702.png
  632   Thu Jul 3 16:18:51 2008 robSummaryLockingspecgrams
I used ligoDV to make some spectrograms of DARM_ERR (1), QPDX (2), and QPDY (3). These show the massive instability from 30-40Hz growing in the XARM in the last two minutes of a reasonably high power lock (arm powers up to 30). It's strange that it only shows up in one arm.

CARM is on PO-DC, for both the MCL and the AO path.
DARM is on AS166Q.
Attachment 1: darm_specg.png
Attachment 2: qpdx_specg.png
Attachment 3: qpdy_specg.png
  651   Wed Jul 9 12:42:14 2008 JohnUpdateLockingHand off to RF CARM
Rob, Yoichi, John

Last night we were able to reduce the CARM offset to around 80. This was achieved by increasing the DARM gain and
switching to AS_I when AS_Q went bad. This is probably a temporary solution, we will probably switch to DC readout
for DARM as we bring the arms on resonance.

Having reduced the arm offset enough to get us into the linear region of the RF_CARM signal (POX_I) we worked on
analogue conditioning of this signal to allow us to hand over. Lock was maintained for over 20 minutes as we did
this work.

We were able to partially switch over both the frequency and length paths to this new signal before losing lock.
Attachment 1: LongLock080709.png
  655   Thu Jul 10 14:59:01 2008 robUpdateLockingRF common mode at zero offset
rob, john, yoichi

Last night we succeeded in reducing the CARM offset to zero.

We handed off control of the common mode servo from PO-DC to POX-I.

We pushed the common mode servo bandwidth to ~19kHz. Without the boosts, it had ~80 degs of phase margin. Didn't measure it after engaging the boosts (Boost + 1 superboost). Trying to engage the second superboost stage broke the lock.

The process is fully scripted, and the script worked all the way through several times.

The DARM ugf was ~200Hz. The RSE peak could clearly be seen. No optical spring, as expected (we're locking in anti-spring mode).

Engaging test mass de-whitening filters did not work (broke the lock).

I'm attaching a lock control sequence diagram and a trend of the arm power during a scripted up-sequence. I think the script can be sped up significantly (especially the long ramp period).

Up next:

Calibrated DARM spectrum
Noise hunting (start with dewhites)
DC - Readout
Lock to the springy side.
Attachment 1: lock_control_sequence_worked.png
Attachment 2: trendpowerbuild.png
  661   Fri Jul 11 23:55:25 2008 alanUpdateLockingRF common mode at zero offset

rob, john, yoichi

Last night we succeeded in reducing the CARM offset to zero.

Congratulations! Well done! I look forward to hearing the details and further progress!
  675   Tue Jul 15 12:44:08 2008 JohnSummaryLockingDRFPMI with DC readout
Rob, John

Last night, despite suspect alignment, we were again able to reduce the CARM offset to zero using
the RF signal.We were also able to transfer to dc readout taking calibrated spectra in both states.
DC readout shows a marked improvement over RF above ~1kHz but introduces some noise around 100Hz.
Broadband sensitivity appears to be more than ten times worse than previously. The calibration
being used remains to be confirmed.

Engaging the ETMY dewhitening caused lock to be lost. We'll check this today. The OMC alignment loops
may also need some attention.

We looked at REFL_166 as a candidate for CARM, at present POX still looks better.

The DARM filters were modified to reduce excess noise around 3Hz. Updating filter coefficients does
not cause loss of lock.
  732   Thu Jul 24 03:08:20 2008 robUpdateLocking+f2 DRMI+2ARMS

rob, john, yoichi

Tonight we tried to move the 166MHz (f2) sideband frequency by changing the settings on the Marconi. Reducing the frequency by 4kHz reduced the amplitude of the 166MHz sidebands, but we were still able to lock the DRMI with the +-f2 sidebands by electronically compensating for the gain decrease, and also to lock the DRMI+2ARMs while resonating the -f2 sideband. No luck with the +f2.

Then we larkily tried increasing the frequency by 4kHz, which ~doubled the f2 sideband transmission through the MC. This means our frequencies/MC length have been mismatched for months. Apparently I explained the level of the f2 sidebands by just imagining that I'd (or someone) had set the modulation depth at that level some time in the past.

It's a miracle any locking worked at all in this state. Once this was done and we worked out a few kinks in the script, adjusting some gains to compensate, we managed to get the DRMI+2ARMS to lock a couple of times while resonating the +f2 sideband. It takes a while, but at least it happens. Tomorrow we'll measure the length of the mode cleaner properly and then try again. No need to vent just yet.
  848   Mon Aug 18 17:37:14 2008 robUpdateLockingrecovery progress

I removed the beam block after the PSL periscope and opened the PSL shutter.

There was no MC Refl beam on the camera, so I decided to trust the PSL launch
and aligned the MC to the PSL beam. Here are the old and new values for
the MC angle biases:
 __Epics_Channel_Name______   __OLD_____    ___New___
 C1:SUS-MC1_PIT_COMM          4.490900        3.246900 
 C1:SUS-MC1_YAW_COMM          0.105500	      -0.912500
 C1:SUS-MC2_PIT_COMM          3.809700	      3.658600 
 C1:SUS-MC2_YAW_COMM          -1.837100	      -1.217100
 C1:SUS-MC3_PIT_COMM          -0.614200	      -0.812200
 C1:SUS-MC3_YAW_COMM          -3.696800	      -3.303800

After this, the beam looks a *little low* going into the Faraday Isolator.
Nonetheless, after turning on the IFO input steering PZTs, I was able to
quickly steer the PRM get a beam on the REFL camera and into the REFL OSA.
The PRM optical lever beam is also striking the quad.

I then used the ETMX optical lever as a reference for realigning. After
steering around the input PZTs and ITMX, I saw some flashes in Xarm trans, then got
it locked and ran the alignment script ~5 times. The arm power went
up to 0.9, so I tweaked the MC1 to put the MC refl beam back on MCWFS.
The XARM power then went up to .96. Good enough for now.

Then I started to try and re-align the YARM. Since the oplevs for both ITMY
and the BS are untrustworthy, I first tried to get the beam bouncing off ITMX
and the BS back into the AS OSA, to try and recover some BS alignment. This
didn't work, as the AS OSA may not be a good reference anyways. After
wandering around in the dark for a little while, I decided to try an automated
scan of the alignment space. I used the trianglewave script to scan
the angle biases of BS, ITMY, & ETMY, then looked at the trend of the transmitted
power to find the gps time when there were flashes. I then used
time_machine_conlog to restore the biases to that time. This was close
enough to easily recover the alignment. After several rounds of aligning &
centering oplevs, things look good.

Also locked a PRM. Will work on the DRM tomorrow.

I'm leaving the optics in their "aligned" states over night, so they can
start their "training."

Note: The MC is not staying locked. Needs investigation.

For tomorrow:

lock up the DRM
fix the mode cleaner
re-align mode cleaner to optimize beam through Faraday
re-align all optics again (will be much easier than today)
re-align beam onto all PDs after good alignment of suspended optics is established.
Attachment 1: flatlissa.png
  862   Wed Aug 20 13:23:32 2008 robUpdateLockingDRMI locked

I was able to lock the DRMI this afternoon. All the optical levers have been centered.
  953   Wed Sep 17 12:58:12 2008 robUpdateLockingbad

Locking was pretty unsuccessful last night. All the subparts were locked (ARMs, PRM, DRM) and
aligned, but no DRMI+2ARMs locks. The alignment may have drifted significantly by the time I
got around to working the full shebang, however.

We should get back into the habit of clicking the
yellow "Restore last auto-alignment" button when we finish using the interferometer.
  985   Tue Sep 23 13:25:07 2008 robUpdateLockinga bit better
I've been spending time working on the short DOF loops (PRC,MICH,SRC) in an attempt to make the
initial stage of lock acquisition (the DRMI+2ARMs, no spring) better. This seems to have been
largely successful, as last night there were several locks of the DRMI+2ARMs with pretty short
wait times.

The output matrix for the short DOFs is a bit strange, though. The MICH->PRM element is about
3 times too small, which seems to indicate something broken in hardware. The MICH->SRM element
seems normal, though, which suggests the BS is isn't broken--either the PRM has had a sudden
actuation increase or it's a problem with the sensing.
  998   Fri Sep 26 16:08:39 2008 robUpdateLockingsome progress
There's been good progress in locking the last couple of nights. A lot of time was wasted before I found that
all the SUS{POS,PIT,YAW} damping gains on the SRM were set to 0.1 for some reason, which let it get rung up
just a bit during bang locking. After setting these gains to 0.5 (similar to PRM and BS), the initial lock
acquisition of DRMI+2ARMs (nospring) got much quicker. Then more time was wasted by sticky sliders on the
transmon QPD whitening gain, causing the Schmitt triggered HI/LO gain PD switch not to happen. This meant
that the arm power was not reported properly when the CARM offset was reduced, and so loop gain normalizations
were not working properly. After all this, by the end of the night last night, reduced the CARM offset such
that stored power in the arms was about half of the max. Should be able to get to full power with another
good night, and then back to springy locking.
  1009   Tue Sep 30 13:43:43 2008 robUpdateLockinglast night
Steady progress again in locking again last night. Initial acquisition of DRMI+2ARMs was working well.
Short DOF handoff, CARM->MCL, AO on PO_DC, and power ramping all worked repeatedly, in the cm_step script.
This takes us to the point where the common mode servo is handed off to an RF signal and the CARM offset
is reduced to zero. This last step didn't work, but it should just require some tweaking of the gains
during the handoff.
  1011   Wed Oct 1 00:24:54 2008 ranaUpdateLockinglast night
I had mistakenly left the MC boost off during my FAST investigations. The script is now restored.

The ISS is still saturating with gains higher than -5 dB. We need to request a PeterK / Stefan consult in the morning.

Also found the MZ gain down at -10 dB around midnight - need an alarm on that value.
  1014   Wed Oct 1 02:54:03 2008 robUpdateLockingbad

Tried the spring-y side tonight with a discouraging lack of progress. There were several locks of DRMI+2ARMs with
the +f2 (springy) sideband resonating in the DRM, but they weren't very stable. Moving to just the DRMI and resonating
the +f2, in order to tune up the acquisition and the handoff to the double demod signals, revealed the problem that the
DRM just won't stay locked on the +f2 sideband. It locks quickly, but only for a few seconds. This is different from the
behaviour with the -f2 sideband, which locks quickly and stably. In theory, the two sidebands should behave similarly.
It could be problems with HOMs in the recycling cavities, and so we may try changing the modulation frequency slightly.
  1019   Thu Oct 2 02:45:50 2008 robUpdateLockingmarginally better
Locking the DRMI with the +f2 sideband was marginally better tonight. I was able to get it lock stably enough to take transfer
functions and handoff MICH & PRC to double demod signals. After re-alignment, however, behaviour was similar to last night
(locks quickly but only for a few seconds), so that lends some credence to HOM-as-bad-guy theories.
  1024   Fri Oct 3 15:57:05 2008 robUpdateLockinglast night, again
Last night was basically a repeat of the night before--marginally better locking with the DRMI resonating the +f2
sideband. Several stable locks were achieved, and several control handoffs to DDM signals worked, but never from
lock to lock--that is, a given DD handoff strategy would only work once. This really needs to work smoothly before
more progress can be made.

Also, a 24Hz mode got rung up in one/several of the suspensions--this can also impede the stability of locks.
  1117   Thu Nov 6 10:06:41 2008 steveUpdateLockingarms lock degradation
I have been locking the arms in the mornings lately.
The daily drift of LSC-TRX is ~ 15% and LSC-TRY ~5%
Attachment 1: arms.jpg
  1327   Thu Feb 19 23:50:31 2009 peteUpdateLockingaligned pd's on AP table

Yoichi, Peter

While continuing our efforts to lock, we noticed the procedure failed at a point it had gotten past last night:  turning on the bounce/roll filters in MICH, PRC, and SRC.  We checked the MICH transfer function and noticed that the unity gain point was ~10 Hz, well below the bounce modes.   We tried increasing the gain but found saturation, and Rob suggested that there could be misalignment on the AP table, which Steve worked on today.  We went out and found two of the PDs (ASDD133 and AS166) to be badly misaligned probably due to a bumped optic upstream.  We re-aligned.



  1329   Fri Feb 20 03:52:23 2009 YoichiUpdateLockingLocking Tonight
Yoichi, Peter

Tonight, we had a problem with the DD hand off.
It failed when the RG filters of MICH for the bounce-roll modes are engaged.
The reason for the failure was that the MICH UGF was too low (~10Hz).
As in the Peter's elog entry, we found that the AS PDs are mis-centered.
Even after we fixed the centering, the MICH UGF was still too low. So we increased the MICH feedback gain by a factor of 10.
The reason for the gain decrease is unknown. It seems almost like the BS coils get weaker.
I checked the UGF of the BS OL loops. These are around 4Hz, so fine. We should check the HWP on the AP table tomorrow.

After the DD hand-off goes ok, the switching of DARM signal from DC to RF failed.
I found that the gain and the polarity of the RF signal were wrong.
AS166 is one of the PDs we found mis-centered (and re-centered). But how can you flip the sign of the signal ?

After this, the cm_step script goes until the activation of the moving zero, but fails when the arm power is increased to 0.7.
Also the ontoMCL script succeeds only 50% of the time.
  1334   Tue Feb 24 02:23:40 2009 YoichiUpdateLockingLocking - MC board bad
Rob, Yoichi, Alberto, Kiwamu, Kakeru

We found that the OMC alignment feedback was on for the POS X loop even though the OMC was not locked.
This caused the PZT mirror to be tilted in yaw a lot. This was probably the reason for the mysterious shift in the AS beam last week, because the AS RF beam is picked up after this PZT mirror.
Rob aligned the OMC and we re-centered the AS PDs and the CCD.
This changed the DARM RF gain, so we changed it from 3 to 1. This gain used to be -1. It is still not understood why the polarity was changed.
The MC length was changed ? We should check the sideband transmission.

After this, we reached to the arm power 4. But the IFO loses lock immediately after the moving zero is turned off.
At this stage, the CARM loop bandwidth is supposed to be high enough that the moving zero is no longer necessary.
However, when we measured the MCL loop gain with several different AO path gains, the loop shape did not change at all.
This led us to suspect the AO path may not be connected. The cabling from the common mode board to the MC board seemed ok.
We tested the signal flow in the MC board using a signal generator and an oscilloscope.
Then we found that a signal injected to the IN2 (AO path) does not reach to the TP1A (right after the boost stages), though the signal is visible in the OUT2 (monitor BNC right after the initial amplifier (B-amp) for the AO path). The signal from IN1 (MC REFL) can be observed at TP1A. This means something is broken between the B-amp and the sum-amp in the AO path.
We will check the MC board tomorrow.
  1335   Tue Feb 24 18:42:15 2009 peteUpdateLockingmc board repair
Peter, Yoichi
Last night:

However, when we measured the MCL loop gain with several different AO path gains, the loop shape did not change at all. This led us to suspect the AO path may not be connected. The cabling from the common mode board to the MC board seemed ok. We tested the signal flow in the MC board using a signal generator and an oscilloscope. Then we found that a signal injected to the IN2 (AO path) does not reach to the TP1A (right after the boost stages), though the signal is visible in the OUT2 (monitor BNC right after the initial amplifier (B-amp) for the AO path). The signal from IN1 (MC REFL) can be observed at TP1A. This means something is broken between the B-amp and the sum-amp in the AO path. We will check the MC board tomorrow.

Today we examined the MC board. With the extension board in place everything seemed fine. Without the extension board we could replicate the problem. Jiggling the IN2 jack caused the injected signal observed at TP1A to come and go. These jacks are unfortunately mounted directly on the board. We traced the problem to a resistor in this path (R30) which looked fishy. We soldered on a new 2K resistor with OWC and it fixed the problem.
  1336   Wed Feb 25 03:10:24 2009 YoichiUpdateLockingLocking status
Rob, Yoichi, Kakeru, Kiwamu

Tonight, CARM -> MCL hand off was not stable. The MCF signal monotonically went up to +2V after CARM and MCL gain was turned down to zero.
This was repeatable and it only goes up (not down).
After a while, we found that putting sleep (~5sec) between the zeroing of CARM gain and MCL gain prevents this problem.

Handing off of CARM error signal from TR to PODC was also not robust.
It seems that the suitable gain changes every time.

tdsavg started to exit with errors. We rebooted fb40m.
When tdsavg returns an error, the cm_step script tries to write NaN into SPOB DC offset.
To prevent this, I put the tdsavg in a while loop which runs until tdsavg returns something other than NaN.

I was able to hand off to PODC several times, but could not proceed further because the IFO lost lock soon.
  1341   Thu Feb 26 19:59:23 2009 YoichiUpdateLockingDaytime locking
Osamu, Yoichi

We tried locking today from about 2PM.
It took about 1000sec on average to acquire the initial lock.
After the initial lock is achieved, the hand-off/ramp-up steps were reasonably robust, although the AS beam sometimes fluctuates a lot (not good for mental health).

Like last night, the IFO loses lock at around arm-power=8.
We measured the CARM AO path loop gain at arm-power=4. We used the SR785 connected to the A-excitation channel of the common mode board through my TFSR785.py script.

The first attachment is the transfer function measured right after the arm power was ramped up to 4.
The overall bandwidth of the CM servo is only 400Hz. Note that since this is the loop gain of only the AO path, the low frequency gain is eaten by the MCL path.
The second attachment is the same transfer function measured after the AO path gain was increased by 6dB.
It is evident that the AO path is working.
We increased both the AO path and MCL gain by 18dB. The third attachment is the AO path TF in this state.
We then increased the arm power but lost lock at arm-power=6. We should have checked the DARM loop too.
BTW, these plots are automatically generated when you use TFSR785.py for transfer function measurements.

I added -notickle option to c1_watch_dr_bang, since tickling seems to be not necessary during the daytime (actually the initial lock was easier with no tickling).

As the construction work in the next building is now calmed down, I think it is ok to do locking during the day time, though I still plan to come at night.
The improvement of my brain efficiency during the day time may compensate for the longer wait time for initial lock.
Attachment 1: CM1.png
Attachment 2: CM2.png
Attachment 3: CM3.png
ELOG V3.1.3-