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  17012   Mon Jul 18 16:39:07 2022 PacoSummaryLSCFPMI locking procedure using REFL55 and AS55

[Yuta, Paco]

In summary, we locked FPMI using REFL55_I, REFL55_Q, and AS55_Q. The key to success was to mix POX11_I and POY11_I in the right way to emulate CARM/DARM, and to find out the correct demodulation phase for AS55.


Procedure

  1. Close PSL shutter and zero offsets in AS55, REFL55, POX11, POY11, and ASDC
    • For ASDC run python3 resetOffsets.py -c C1:LSC-ASDC_IN1, otherwise use the zer offsets on I and Q inputs from the RFPD medm screen.
  2. Lock XARM/YARM using POX/POY to tune demodulation phase.
    • Today, the demode phase in POX11 changed to 104.801, and POY11 to -11.256 deg.
  3. XARM and YARM are used in the following configuration
    • INMAT
      • 0.5 * POX11_I - 0.5 * POY --> XARM
      • 0.5 * POX + 0.5*POY --> YARM
      • REFL55_Q --> MICH (** this should be turned on after POX11/POY11)
    • LSC Filter gains
      • XARM = 0.012
      • YARM = 0.012
      • MICH = +40 (note the sign flip from last time)
    • OUTMAT
      • XARM --> 0.5 * ETMX - 0.5 * ETMY
      • YARM --> MC2
      • MICH --> BS
    • UGFs (sanity check)
      • XARM (DARM) ~ 100 Hz
      • YARM (CARM) ~ 200 Hz
      • MICH (MICH) ~ 40 Hz
  4. Run MICHOpticalGainCalibration.ipynb to see if ASDC vs REFL55_Q looks nice (ellipse in the XY plot), and find any residual offset in REFL55_Q.
    • If the plot doesn't look nice in this regard, the IFO needs to be aligned.
  5. Sensing matrix for CARM/DARM and MICH.
    • With the DARM, CARM and MICH lines on, verify the demod error signals look ok both in mag and phase.
    • For example, we found that CARM error signals were correctly represented by either 0.5 * POX11_I + 0.5 * POY11_I or 0.5 * REFL55_I.
    • Similarly, we found that DARM error signal was correctly represented by either 0.5 * POX11_I - 0.5 * POY11_I or 2.5 * AS55_Q.
    • To find this, we minimized CARM content in AS55_Q, as well as CARM content in REFL55_Q.
  6. We acquired the lock by re-configuring the error point as below:
    • INMAT
      • 0.5*REFL55_I --> YARM (CARM)
      • 2.5 * AS55_Q --> XARM (DARM)
    • During the hand-off trials, we repeatedly ran the sensing matrix and UGF measurements while stopping at various intermediate mixed error points to check how the error signal calibrations changed if at all.
      • Attachment #1 shows the DARM OLTF using POX/POY (blue), only with CARM handoff (green), and after DARM handoff (red)
      • Attachment #2 shows the CARM OLTF using POX/POY (blue), only with CARM handoff (green), and after DARM handoff (red)
      • Attachment #3 shows the MICH OLTF using POX/POY (blue), only with CARM handoff (green), and after DARM handoff (red)
    • The sensing matrix after handoff is below:
Sensing Matrix with the following demodulation phases
{'AS55': 192.8, 'REFL55': 95.63177865911078, 'POX11': 104.80089727128349, 'POY11': -11.256509422276006}
Sensors          	           DARM     	           CARM     	            MICH     	
C1:LSC-AS55_I_ERR_DQ	5.09e-02 (89.6761 deg)	2.03e-01 (-114.513 deg)	1.28e-04 (-28.9254 deg)	
C1:LSC-AS55_Q_ERR_DQ	4.78e-02 (88.7876 deg)	3.61e-03 (-68.7198 deg)	8.34e-05 (-39.193 deg)	
C1:LSC-REFL55_I_ERR_DQ	5.18e-02 (-92.2555 deg)	1.20e+00 (65.2507 deg)	1.15e-04 (-102.027 deg)	
C1:LSC-REFL55_Q_ERR_DQ	1.81e-04 (59.0854 deg)	1.09e-02 (-114.716 deg)	1.77e-05 (-23.6485 deg)	
C1:LSC-POX11_I_ERR_DQ	8.51e-02 (91.2844 deg)	4.77e-01 (67.1709 deg)	7.97e-05 (-72.5252 deg)	
C1:LSC-POX11_Q_ERR_DQ	2.63e-04 (114.584 deg)	1.32e-03 (-113.505 deg)	2.10e-06 (118.146 deg)	
C1:LSC-POY11_I_ERR_DQ	1.58e-01 (-88.9295 deg)	6.16e-01 (67.6098 deg)	8.71e-05 (172.73 deg)	
C1:LSC-POY11_Q_ERR_DQ	2.89e-04 (-89.1114 deg)	1.09e-03 (70.2784 deg)	3.77e-07 (110.206 deg)	

Lock gpstimes:

  1. [1342220242, 1342220260]
  2. [1342220420, 1342220890]
  3. [1342221426, 1342221574]
  4. [1342222753, 1342223230]

Sensitivity estimate (NANB)

Using diaggui, we look at the AS55_Q error point and the DARM control point (C1:LSC-XARM_OUT). We roughly calibrate the error point using the sensing matrix element and actuation gain at the DARM oscillator freq 4.78e-2 / (10.91e-9 / 307.880^2). The control point is calibrated with a 0.95 Hz SUS pole. Attachment #4 shows the sensitivity estimate.

Attachment 1: DARM_07_18_2022_FMPI.pdf
DARM_07_18_2022_FMPI.pdf DARM_07_18_2022_FMPI.pdf DARM_07_18_2022_FMPI.pdf
Attachment 2: CARM_07_18_2022_FPMI.pdf
CARM_07_18_2022_FPMI.pdf CARM_07_18_2022_FPMI.pdf CARM_07_18_2022_FPMI.pdf
Attachment 3: MICH_07_18_2022_FPMI.pdf
MICH_07_18_2022_FPMI.pdf MICH_07_18_2022_FPMI.pdf MICH_07_18_2022_FPMI.pdf
Attachment 4: fpmi_darm_nb_2022_07.pdf
fpmi_darm_nb_2022_07.pdf
  17016   Mon Jul 18 21:41:42 2022 AnchalSummaryLSCFPMI locking procedure using REFL55 and AS55

Now that you have found a working configuration, I suggest we update CARM and DARM filter banks so that they are used in locking those degrees of freedom instead of repurposing XARM/YARM banks. It would be bit easier to understand and leaves room for future changes for one configuration while keeping single arm lock configurations untouched.

  17021   Wed Jul 20 11:58:45 2022 PacoSummaryGeneralJenne laser kaput?

[Paco, Yehonathan, JC]

We were trying to setup the Jenne laser to characterize the response of three 1811s that Yehonathan is using for his WOPA experiment (in QIL). We hooked up a ~ 5 VDC power supply to the bias tee and looked to see if there was any DC response in the REF PD. We used a DB9 breakout board and a DB9 cable, and saw some current being drawn. The DC current was a bit too high (500 mA), so we turned the DC voltage off, and realized the VDC power was reversed, probably along the DB9 cable which we didn't check before. As we flipped the power supply leads and turned power back on, we could no longer see any current even though the voltage was now right (or was it???). We would like to debug this laser, and continue using it if it still works (!), but there is negligible documentation either here or in the wiki, so if there are any known places to look at it would be helpful to know them.

  17022   Wed Jul 20 14:12:07 2022 PacoSummaryGeneralJenne laser kaput!

[Koji, Yehonathan, Paco]

Koji pointed out that this laser was always driven with a current driver (which was not nearby), and after finding it on one of the rolling carts, we hooked up the system but found that the laser driver displayed open circuit near the usual 20mA operating point. We therefore have to conclude that this laser is no more. We will look for a reasonable replacement.

Quote:

[Paco, Yehonathan, JC]

We were trying to setup the Jenne laser to characterize the response of three 1811s that Yehonathan is using for his WOPA experiment (in QIL). We hooked up a ~ 5 VDC power supply to the bias tee and looked to see if there was any DC response in the REF PD. We used a DB9 breakout board and a DB9 cable, and saw some current being drawn. The DC current was a bit too high (500 mA), so we turned the DC voltage off, and realized the VDC power was reversed, probably along the DB9 cable which we didn't check before. As we flipped the power supply leads and turned power back on, we could no longer see any current even though the voltage was now right (or was it???). We would like to debug this laser, and continue using it if it still works (!), but there is negligible documentation either here or in the wiki, so if there are any known places to look at it would be helpful to know them.

 

  17023   Wed Jul 20 15:58:52 2022 KojiSummaryGeneralJenne laser kaput!

For troubleshooting, the proper laser driver (found beneath the AG network analyzer) was connected.
The current ~1mA was provided and the driver detected the "open circuit", which means the laser diode was busted.

https://dcc.ligo.org/LIGO-T060240

The laser diode in the parts list is: "GTRAN GaAs Strained QW Laser Diode, Part # LD-1060".

  17030   Mon Jul 25 09:05:50 2022 PacoSummaryGeneralTesting 950nm laser found in trash pile

[Paco, Yehonathan]

==== Late elog from Friday ====

Koji provided us with a QFLD-950-3S (QPHOTONICS) salvaged from Aidan's junk pile (LD is alive according to him). We tested the Jenne laser setup with this just to decide if we should order another one, and it worked.

The laser driver anode and cathode pins (8/9, 4/5 respectively) on the rear DB9 port from the  ILX Lightwave LDX-3412 driver were connected to the corresponding anode and cathode pins in the laser package (5, and 9; note the numbers are reversed between driver and laser). Then, interlock pins 1 and 2 in the driver were shorted to enable operation. This is all illustrated in Attachments #1-2.

After setting a limit of 27.6 mA current in the driver, we slowly increased the actual current to ~ 19 mA until we could see light on a beam card. We can go ahead and get a 1060 nm replacement.

Attachment 1: PXL_20220722_234600124.jpg
PXL_20220722_234600124.jpg
Attachment 2: PXL_20220722_234551918.jpg
PXL_20220722_234551918.jpg
  17035   Mon Jul 25 18:22:30 2022 DeekshaSummaryWikiMeasured the PZT TF Successfully

Measured the PZT beatnote using the setup mentioned in elog post 17031. Attached is the data taken from 10kHz to 1MHz, decadewise data was also taken that I'm not including in this post. A_R refers to the transfer function taken of channel A wrt the voltage reference (the swept sine we are inputting which has an IF of 30kHz). A and B correspond to the I and Q components of the signal taken from the DFD, respectively. I am currently working on plotting the data, and will shortly update this post with plots. Next steps - 

- quantify the uncertainty in the signal (I think)

- vectfit the data to find poles and zeroes

(and possibly find a better way to print/obtain data)

Edit: first pass of data plotted

Attachment 1: A_R_MAG.txt
"4395A REV1.12"
"DATE: Sep 17 2017"



"CHANNEL: 1"
"MEASURE TYPE: A/R"
"FORMAT TYPE: LOG MAG"
"NUMBER of POINTS: 801"
"SWEEP TIME:  385.3 ms"
... 811 more lines ...
Attachment 2: A_R_PHASE.txt




"CHANNEL: 2"
"MEASURE TYPE: A/R"
"FORMAT TYPE: PHASE (DEG)"
"NUMBER of POINTS: 801"
"SWEEP TIME:  385.3 ms"
... 808 more lines ...
Attachment 3: B_R_MAG.txt
"4395A REV1.12"
"DATE: Sep 17 2017"



"CHANNEL: 1"
"MEASURE TYPE: B/R"
"FORMAT TYPE: LOG MAG"
"NUMBER of POINTS: 801"
"SWEEP TIME:  385.3 ms"
... 809 more lines ...
Attachment 4: B_R_PHASE.txt




"CHANNEL: 2"
"MEASURE TYPE: B/R"
"FORMAT TYPE: PHASE (DEG)"
"NUMBER of POINTS: 801"
"SWEEP TIME:  385.3 ms"
... 807 more lines ...
Attachment 5: freq_resp_I.png
freq_resp_I.png
Attachment 6: freq_resp_Q.png
freq_resp_Q.png
  17051   Mon Aug 1 17:19:39 2022 CiciSummaryGeneralRPitaya Data on Jupyter Notebook

Have successfully plotted data from the Red Pitaya on Jupyter Notebook! Have lost years of my life fighting with PyQt. Thanks to Deeksha for heavy contribution. Next task is to get actually good data (seeing mostly noise right now and haven't figured out how to change my input settings) and then to go to set up the RPi in the lab.

  17064   Fri Aug 5 17:03:31 2022 YehonathanSummaryGeneralTesting 950nm laser found in trash pile

I set out to test the actuation bandwidth of the 950nm laser. I hooked the laser to the output of the bias tee of PD testing setup. I connected the fiber coming out of the laser to the fiber port of 1611 REF PD.

The current source was connected to the DB9 input of the PD testing setup. I turned on the current source and set the current to 20mA. I measured with a fluke ~ 2V at the REF PD DC port.

I connected the AC port of the bias tee to the RF source of the network analyzer and the AC port of the REF PD to the B port of the network analyzer. Attachment 2 shows the setup.

I took a swept sine measurement (attachment) from 100kHz to 500MHz.

It seems like the bandwidth is ~ 1MHz which is weird considering the spec sheet says that the pulse rise time is 0.5ns. To make sure we are not limited by the bandwidth of the cables I looped the source and the input of the network analyzer using the cables used for the previous measurement and observed that the bandwidth is a few 100s of MHz.

Attachment 1: 20220805_164434.jpg
20220805_164434.jpg
Attachment 2: LaserActuation_TF_Measurement.drawio.pdf
LaserActuation_TF_Measurement.drawio.pdf
  17069   Tue Aug 9 19:54:31 2022 yutaSummaryLSCFPMI locking tonight

[Tega, Anchal, Yuta]

We resored FPMI locking settings. Below is the summary of locking configurations tonight.
To ease the lock acquisition, the step to feedback POX11_I to ETMX and POY11_I to MC2 before POX and POY mixing was necessary tonight.

CARM (YARM):
 - 0.5 * POX11_I + 0.5 * POY11_I handed to 0.5 * REFL55_I
 - YARM filter module, FM4,5 for acquisition, FM1,2,3,6,8 triggered, C1:LSC-YARM_GAIN = 0.012
 - Actuation on -0.77 * MC2
 - UGF ~ 250 Hz

DARM (XARM):
 - 0.5 * POX11_I - 0.5 * POY11_I handed to 4.6 * AS55_Q (it was 2.5 in 40m/17012)
 - XARM filter module, FM5 for acquisition (no FM4), FM1,2,3,6,8 triggered, C1:LSC-XARM_GAIN = 0.015
 - Actuation on 0.5 * ETMX - 0.5 * ETMY
 - UGF ~ 120 Hz

MICH:
 - 1 * REFL55_Q (turned on after XARM and YARM acquisition)
 - MICH filter module, FM4,5,8 for acquisition, FM2,3 triggered, C1:LSC-MICH_GAIN = +40
 - Actuation on 0.5 * BS
 - UGF ~ 100 Hz

Measured sensing matrix:
Sensing Matrix with the following demodulation phases
{'AS55': 200.41785156862835, 'REFL55': 93.7514468401475, 'POX11': 105.08325063571438, 'POY11': -11.343909976281823}
Sensors              DARM                    CARM                   MICH
C1:LSC-AS55_I_ERR_DQ 5.27e-02 (-154.105 deg) 2.83e-01 (132.395 deg) 1.17e-04 (-40.1051 deg)
C1:LSC-AS55_Q_ERR_DQ 3.99e-02 (-151.048 deg) 1.42e-02 (125.504 deg) 1.41e-04 (-2.42846 deg)
C1:LSC-REFL55_I_ERR_DQ 5.59e-02 (77.6871 deg) 1.15e+00 (-44.589 deg) 3.55e-04 (69.2585 deg)
C1:LSC-REFL55_Q_ERR_DQ 1.84e-03 (16.3186 deg) 3.35e-03 (125.67 deg) 4.59e-05 (4.18718 deg)
C1:LSC-POX11_I_ERR_DQ 1.54e-01 (-157.852 deg) 6.07e-01 (-42.1078 deg) 5.55e-05 (73.3963 deg)
C1:LSC-POX11_Q_ERR_DQ 6.83e-05 (-148.591 deg) 6.37e-04 (121.983 deg) 1.35e-06 (43.7201 deg)
C1:LSC-POY11_I_ERR_DQ 1.85e-01 (36.1624 deg) 5.73e-01 (-43.1776 deg) 2.12e-04 (82.16 deg)
C1:LSC-POY11_Q_ERR_DQ 2.16e-05 (130.937 deg) 6.38e-05 (-173.194 deg) 1.40e-06 (47.5416 deg)

FPMI locked periods:
  - 1344129143 - 1344129520
  - 1344131106 - 1344131305
  - 1344133503 - 1344134020

Next:
- Restore CM servo for CARM

  17073   Wed Aug 10 20:30:54 2022 TegaSummarySUSCharacterisation of suspension damping

[Yuta, Tega]

We diagnosed the suspension damping of the IMC/BHD/recycling optics by kicking the various degree of freedom (dof) and then tuning the gain so that we get a residual Q of approx. 5 in the cases where this can be achieved.

MC1: Good
MC2: SIDE-YAW coupling, but OK
MC3: Too much coupling between dofs, NEEDS ATTENTION
LO1: Good
LO2: Good
AS1: POS-PIT coupling, close to oscillation, cnt2um off, NEEDS ATTENTION
AS4: PIT-YAW coupling, cannot increase YAW gain because of coupling, No cnt2um, No Cheby, NEEDS ATTENTION
PR2: No cnt2um, No Cheby
PR3: POS-PIT coupling, cannot increase POS/PIT/YAW gain because of coupling, No cnt2um, No Cheby, NEEDS ATTENTION
SR2: No cnt2um

Attachment 1: BHD_SUSPIT_KICK.png
BHD_SUSPIT_KICK.png
Attachment 2: BHD_SUSPOS_KICK.png
BHD_SUSPOS_KICK.png
Attachment 3: BHD_SUSSIDE_KICK.png
BHD_SUSSIDE_KICK.png
Attachment 4: BHD_SUSYAW_KICK.png
BHD_SUSYAW_KICK.png
Attachment 5: IMC_SUSPIT_KICK.png
IMC_SUSPIT_KICK.png
Attachment 6: IMC_SUSPOS_KICK.png
IMC_SUSPOS_KICK.png
Attachment 7: IMC_SUSSIDE_KICK.png
IMC_SUSSIDE_KICK.png
Attachment 8: IMC_SUSYAW_KICK.png
IMC_SUSYAW_KICK.png
Attachment 9: PRSR_SUSPIT_KICK.png
PRSR_SUSPIT_KICK.png
Attachment 10: PRSR_SUSPOS_KICK.png
PRSR_SUSPOS_KICK.png
Attachment 11: PRSR_SUSSIDE_KICK.png
PRSR_SUSSIDE_KICK.png
Attachment 12: PRSR_SUSYAW_KICK.png
PRSR_SUSYAW_KICK.png
  17089   Thu Aug 18 14:49:35 2022 YehonathanSummaryLSCFPMI Sensitivity

{Yuta, Yehonathan}

We wrote a notebook found on Git/40m/measurements/LSC/FPMI/NoiseBudget/FPMISensitivity.ipynb for calculating the MICH, DARM (currently XARM), CARM (currently YARM) sensitivities in the FPMI lock which can be run daily.

The IN and OUT channels of each DOFs are measured at a certain GPS time and calibrated using the optical gains and actuation calibration measured in the previous post.

Attachment shows the results.

It seems like the UGFs for MICH and DARM (currently XARM) match the ones that were estimated previously (100Hz for MICH, 120Hz for DARM) except for CARM for which the UGF was estimated to be 250Hz and here seems to be > 1kHz.

Indeed one can also see that the picks in the CARM plot don't match that well. Calculation shows that at 250Hz OUT channel is 6 times more than the IN channel. Calibrations for CARM should be checked.

MICH sensitivity using REFL55 at high frequencies is not much better than what was measured with AS55.

DARM sensitivity at 10Hz is a factor of a few better than the single arm lock sensitivity.

Now it is time to do the budgeting.

Attachment 1: Sensitivity_Plot_1344133503.pdf
Sensitivity_Plot_1344133503.pdf
  17091   Thu Aug 18 18:10:49 2022 KojiSummaryLSCFPMI Sensitivity

The overlapping plot of the calibrated error and control signals gives you an approximately good estimation of the freerun fluctuation, particularly when the open-loop gain G is much larger or much smaller than the unity.
However, when the G is close to the unity, they are both affected by "servo bump" and both signals do not represent the freerun fluctuation around that frequency.

To avoid this, the open-loop gain needs to be measured every time when the noise budget is calculated. In the beginning, it is necessary to measure the open-loop gain over a large frequency range so that you can refine your model. Once you gain sufficient confidence about the shape of the open-loop gain, you can just use measurement at a frequency and just adjust the gain variation (most of the cases it comes from the optical gain).

I am saying this because I once had a significant issue of (project-wide) incorrect sensitivity estimation by omitting this process.

  17123   Wed Aug 31 12:57:07 2022 ranaSummaryALScontrol of ALS beat freq from command line -easy

The PZT sweeps that we've been making to characterize the ALS-X laser should probably be discarded - the DFD was not setup correctly for this during the past few months.

Since the DFD only had a peak-peak range of ~5 MHz, whenever the beat frequency drifts out of the linear range (~2-3 MHz), the data would have an arbitrary gain. Since the drift was actually more like 50 MHz, it meant that the different parts of a single sweep could have some arbitrary gain and sign !!! This is not a good way to measure things.

I used an ezcaservo to keep the beat frequency fixed. The attacehed screenshot shows the command line. We read back the unwrapped beat frequency from the phase tracker, and feedback on the PSL's NPRO temperature. During this the lasers were not locked to any cavities (shutters closed, but servos not disabled).

For the purposes of this measurement, I reduced the CAL factor in the phase tracker screen so that the reported FINE_PHASE_OUT is actually in kHz, rather than Hz on this plot. So the green plot is moving by 10's of MHz. When the servo is engaged, you can see the SLOWDC doing some action. We think the calibration of that channel is ~1 GHz/V, so 0.1 SLOWDC Volts should be ~100 MHz. I think there's a factor of 2 missing here, but its close.

As you can see in the top plot, even with the frequency stabilized by this slow feedback (-1000 to -600 seconds), the I & Q outputs are going through multiple cycles, and so they are unusable for even a non serious measurement.

The only way forward is to use less of a delay in the DFD: I think Anchal has been busily installing this shorter cable (hopefully, its ~3-5 m long so that the linear range is more. I think a 10 m cable is too long.), and the sweeps taken later today should be more useful.

Attachment 1: Untitled.png
Untitled.png
  17127   Fri Sep 2 13:30:25 2022 Ian MacMillanSummaryComputersQuantization Noise Calculation Summary

P. P. Vaidyanathan wrote a chapter in the book "Handbook of Digital Signal Processing: Engineering Applications" called "Low-Noise and Low-Sensitivity Digital Filters" (Chapter 5 pg. 359).  I took a quick look at it and wanted to give some thoughts in case they are useful. The experts in the field would be Leland B. JacksonP. P. VaidyanathanBernard Widrow, and István Kollár.  Widrow and Kollar  wrote the book "Quantization Noise Roundoff Error in Digital Computation, Signal Processing, Control, and Communications" (a copy of which is at the 40m). it is good that P. P. Vaidyanathan is at Caltech.

Vaidyanathan's chapter is serves as a good introduction to the topic of quantization noise. He starts off with the basic theory similar to my own document on the topic. From there, there are two main relevant topics to our goals.

The first interesting thing is using Error-Spectrum Shaping (pg. 387). I have never investigated this idea but the general gist is as poles and zeros move closer to the unit circle the SNR deteriorates so this is a way of implementing error feedback that should alleviate this problem. See Fig. 5.20 for a full realization of a second-order section with error feedback.

The second starts on page 402 and is an overview of state space filters and gives an example of a state space realization (Fig. 5.26). I also tested this exact realization a while ago and found that it was better than the direct form II filter but not as good as the current low-noise implementation that LIGO uses. This realization is very close to the current realization except uses one less addition block.

Overall I think it is a useful chapter. I like the idea of using some sort of error correction and I'm sure his other work will talk more about this stuff. It would be useful to look into.

One thought that I had recently is that if the quantization noise is uncorrelated between the two different realizations then connecting them in parallel then averaging their results (as shown in Attachment 1) may actually yield lower quantization noise. It would require double the computation power for filtering but it may work. For example, using the current LIGO realization and the realization given in this book it might yield a lower quantization noise. This would only work with two similarly low noise realizations. Since it would be randomly sampling two uniform distributions and we would be going from one sample to two samples the variance would be cut in half, and the ASD would show a 1/√2 reduction if using realizations with the same level of quantization noise. This is only beneficial if the realization with the higher quantization noise only has less than about 1.7 times the one with the lower noise. I included a simple simulation to show this in the zip file in attachment 2 for my own reference.

Another thought that I had is that the transpose of this low-noise state-space filter (Fig. 5.26) or even of LIGO's current filter realization would yield even lower quantization noise because both of their transposes require one less calculation.

Attachment 1: averagefiltering.pdf
averagefiltering.pdf
Attachment 2: AveragingFilter.py.zip
  17131   Fri Sep 2 15:40:25 2022 AnchalSummaryALSDFD cable measurements

[Anchal, Yehonathan]

I laid down another temporary cable from Xend to 1Y2 (LSC rack) for also measuring the Q output of the DFD box. Then to get a quick measurement of these long cable delays, we used Moku:GO in oscillator mode, sent 100 ns pulses at a 100 kHz rate from one end, and measured the difference between reflected pulses to get an estimate of time delay. The other end of long cables was shorted and left open for 2 sets of measurements.

I-Mon Cable delay: (955+/- 6) ns / 2 = 477 +/- 3 ns

Q-Mon Cable delay: (535 +/- 6) ns / 2 = 267 +/- 3 ns

Note: We were underestimating the delay in I-Mon cable by about a factor of 2.

I also took the opportunity to take a delay time measurement of DFD delayline. Since both ends of cable were present locally, it made more sense to simply take a transfer function to get a clean delay measurement. This measurement resulted with value of 197.7 +/- 0.1 ns. See attached plot. Data and analysis here.

Attachment 1: ICableOpenEnd_2022-09-02_3_08_34_PM.png
ICableOpenEnd_2022-09-02_3_08_34_PM.png
Attachment 2: ICableShortedEnd_2022-09-02_3_04_43_PM.png
ICableShortedEnd_2022-09-02_3_04_43_PM.png
Attachment 3: QCableOpenEnd_2022-09-02_3_09_49_PM.png
QCableOpenEnd_2022-09-02_3_09_49_PM.png
Attachment 4: QCableShortedEnd_2022-09-02_3_00_55_PM.png
QCableShortedEnd_2022-09-02_3_00_55_PM.png
Attachment 5: DFD_Delay_Measurement.pdf
DFD_Delay_Measurement.pdf
  17132   Tue Sep 6 09:57:26 2022 JCSummaryGeneralLab cleaning

DB9 Cables have been assorted and placed behind the Y-Arm. Long BNC Cables and Ethernet Cables have been stored under the Y-Arm. 

Quote:

We held the lab cleaning for the first time since the campus reopening (Attachment 1).
Now we can use some of the desks for the people to live! Thanks for the cooperation.

We relocated a lot of items into the lab.

  • The entrance area was cleaned up. We believe that there is no 40m lab stuff left.
    • BHD BS optics was moved to the south optics cabinet. (Attachment 2)
    • DSUB feedthrough flanges were moved to the vacuum area (Attachment 3)
  • Some instruments were moved into the lab.
    • The Zurich instrument box
    • KEPCO HV supplies
    • Matsusada HV supplies
  • We moved the large pile of SUPERMICROs in the lab. They are around MC2 while the PPE boxes there were moved behind the tube around MC2 area. (Attachment 4)
  • We have moved PPE boxes behind the beam tube on XARM behind the SUPERMICRO computer boxes. (Attachment 7)
  • ISC/WFS left over components were moved to the pile of the BHD electronics.
    • Front panels (Attachment 5)
    • Components in the boxes (Attachment 6)

We still want to make some more cleaning:

- Electronics workbenches
- Stray setup (cart/wagon in the lab)
- Some leftover on the desks
- Instruments scattered all over the lab
- Ewaste removal

 

Attachment 1: 982146B2-02E5-4C19-B137-E7CC598C262F.jpeg
982146B2-02E5-4C19-B137-E7CC598C262F.jpeg
Attachment 2: 0FBB61AC-E882-458D-A891-7B11F35588FF.jpeg
0FBB61AC-E882-458D-A891-7B11F35588FF.jpeg
  17140   Thu Sep 15 11:13:32 2022 AnchalSummaryASSYARM and XARM ASS restored

With limited proof of working for a few times (but robustly), I'm happy to report that ASS on YARM and XARM is working now.


What is wrong?

The issue is that PR3 is not placed in correct position in the chamber. It is offset enough that to send a beam through center of ITMY to ETMY, it has to reflect off the edge of PR3 leading to some clipping. Hence our usual ASS takes us to this point and results in loss of transmission due to clipping.

Solution: We can not solve this issue without moving PR3 inside the chamber. But meanwhile, we can find new spot positions on ITMY and ETMY, off the center in YAW direction only, which would allow us to mode match properly without clipping. This would mean that there will be YAW suspension noise to Length coupling in this cavity, but thankfully, YAW degree of freedom stays relatively calm in comparison to PIT or POS for our suspensions. Similarly, we need to allow for an offset in ETMX beam spot position in YAW. We do not control beam spot position on ITMX due to lack of enough actuators to control all 8 DOFs involved in mode matching input beam with a cavity. So instead I found the right offset for ITMX transmission error signal in YAW that works well.

I found these offsets (found empirically) to be:

  • C1:ASS-YARM_ETM_YAW_L_DEMOD_I_OFFSET: 22.6
  • C1:ASS-YARM_ITM_YAW_L_DEMOD_I_OFFSET: 4.2
  • C1:ASS-XARM_ETM_YAW_L_DEMOD_I_OFFSET: -7.6
  • C1:ASS-XARM_ITM_YAW_T_DEMOD_I_OFFSET: 1

These offsets have been saved in the burt snap file used for running ASS.


Using ASS

I'll reiterate here procedure to run ASS.

  • Get YARM locked to TEM00 mode and atleast 0.4 transmission on C1:LSC-TRY_OUT
  • Open sitemap->ASC->c1ass
  • Click ! Scripts YARM -> Striptool to open a striptool monitor for ASS error signals.
  • Click on ! Scripts YARM -> Dither ON to switch on the dither.
  • Wait for all error signals to have settled around zero (this should also maximize the transmission channel (currently maximizing to 1.1).
  • Click on ! Scripts YARM -> Freeze Offsets
  • Click on ! Scripts YARM -> Offload Offsets
  • Click on ! Scripts YARM -> Dither OFF.
  • Then proceed to XARM. Get it locked to TEM00 mode and atleast 0.4 transmission on C1:LSC-TRX_OUT
  • Open sitemap->ASC->c1ass
  • Click ! Scripts XARM -> Striptool to open a striptool monitor for ASS error signals.
  • Click on ! Scripts XARM -> Dither ON to switch on the dither.
  • Wait for all error signals except C1:ASS-XARM_ITM_PIT_L_DEMOD_I_OUT16 and C1:ASS-XARM_ITM_YAW_L_DEMOD_I_OUT16 to have settled around zero (this should also maximize the transmission channel (currently maximizing to 1.1).
  • Click on ! Scripts XARM -> Freeze Offsets
  • Click on ! Scripts XARM -> Offload Offsets
  • Click on ! Scripts XARM -> Dither OFF.
  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

 

  13   Thu Oct 25 00:01:21 2007 ranaSoftware InstallationCDSGEO DV => LIGO DV
Martin Hewitson of GEO600 fame has modified the cool GEO DV
to work with the LIGO NDS system with some NDS advice from Rolf (who's over in Germany this week).

I've moved it onto the 40m CDS system and installed it on the AdhikariLab computer named 'django'. It worked immediately.

I modified the main .m file to include the 40m's NDS server. When you run it you have to include the path to the NDS
client written by Ben Johnson.

The attached is a screenshot of it working on a Mac; it looks as cool on Linux.

Its installed in /cvs/cds/caltech/apps/ligoDV/. In matlab you navigate to that directory and then
type addpath('/cvs/cds/caltech/apps/linux/UNIX_NDS_Client_beta2/') to add the NDS client.
On the Solaris machines, type type addpath('/cvs/cds/caltech/apps/solaris9/UNIX_NDS_Client_beta2/') instead.

Then type ligoDV to start it up. Then click away and have fun.

In the example I've selected
C1:PEM-BS_ACC_EAST_Z
and plotted its specgram.

Big grin
Attachment 1: Picture_1.png
Picture_1.png
  25   Mon Oct 29 11:07:22 2007 waldmanSoftware InstallationOMCSoftware install on OMS
[Alex, Sam]

We spent a little time this morning working on OMS and getting things restarted. A few changes were made. 1) We put openmotif on OMS so that the burtrb doesn't throw that crappy libXm any more. 2) We upgraded OMS to a 32 kHz sampling rate from 2 kHz. All the filters will have to be changed. We also added a PDH filter path to maybe feedback PDH signals cuz that will be cool. Maybe someday I will write up the very cool channel adding procedure.
  28   Mon Oct 29 23:25:42 2007 tobinSoftware InstallationCDSframes mounted
I mounted the frames directory on mafalda and linux3. It's intentionally not listed in the /etc/fstab so that an fb crash won't prevent the controls machines from booting. The command to mount the frames directory is:

mount fb40m:/frames/frames /frames
  2   Thu Oct 18 14:52:35 2007 ranaRoutineASCtest
test

X-(:P;(:))
  3   Thu Oct 18 15:03:14 2007 ajwRoutineGeneralthis is only a test

  7   Mon Oct 22 12:02:59 2007 ajwRoutineGeneralSTACIS as microseismic shaker
In case we ever want to use our Stacis systems as shakers, check this:
link
  15   Thu Oct 25 22:02:58 2007 robRoutinePSLHEPAs maxed
In light of the SoCal fires, I turned the PSL HEPAs up to 100%.
  17   Fri Oct 26 09:10:17 2007 steveRoutinePEMPEM &PSL trend
The fires are out, lab particle counts are up.
Psl HEPAs are at 100% and mobel HEPAs are just turned on
20 days plot and 5 hrs plot below
Attachment 1: counts&psl.jpg
counts&psl.jpg
Attachment 2: 5dcounts.jpg
5dcounts.jpg
  18   Fri Oct 26 16:19:29 2007 Tobin FrickeRoutineIOOMC resonances
We would like to measure the absorption of the mode cleaner optics. The plan is to repeat <a href="http://ilog.ligo-wa.caltech.edu:7285/mLIGO/Cleaning_the_Mode_Cleaner">Valera's experiment</a> in which we track the MC's thermal resonances to infer their power absorption. Last night Rana and I hooked up a lock-in amplifier to heterodyne the MC servo signal by 28 kHz and piped the output into an ADC using the MC_AO channel. We did not find any resonances.

Valera recommends we drive the POS of the three MC optics with bandlimited noise to excite the resonances.
  23   Mon Oct 29 09:16:31 2007 steveRoutineVACthe rga is back
We had no filament current since last power glitch of Oct. 8, 2007
First I thought that the filament was lost, but it was only bad contact.
The rga head pins were oxidized. Rga was turned back on last Friday.
It's temp is 55.3C normal
Attachment 1: rgaisback.jpg
rgaisback.jpg
  24   Mon Oct 29 09:46:50 2007 steveRoutineVACvac & pem trend
Pumpdown 64 pumped by maglev for 125 days
pd64-m-d125

Rob, can you tell me, when did the fire start on this plot?
Attachment 1: pd64md125.jpg
pd64md125.jpg
  31   Tue Oct 30 16:55:40 2007 tobinRoutine Drag-wiping perfected
Steve, Tobin

Steve procured an assortment of syringes from the bio storeroom and we practiced drag-wiping the SOS in the flow bench. Using a 50 microliter Hamilton syringe to deliver 16 microliters of methanol seems perfect for drag-wiping the small optics. Drag-wiping in the downward direction seems to work very well, since we can squirt the optic directly in the center, and the (half) piece of kodak lens tissue fits easily between the bottom two earthquake stops.
  38   Wed Oct 31 10:31:23 2007 Andrey RodionovRoutineVACVenting is in progress

We (Steve, David, Andrey) started venting the vacuum system at 9.50AM Wednesday morning.
  39   Wed Oct 31 15:02:59 2007 tobinRoutineIOOMode Cleaner Mode Tracking
I processed the heterodyned mode cleaner data yesterday, tracking the three 28 kHz modes corresponding to MC1, MC2, and MC3. Unfortuntately the effect of our MC power chopping is totally swamped by ambient temperature changes. Attached are two plots, one with the tracked mode frequencies, and the other containing dataviewer trends with the MC transmitted power and the room temperature. Additionally, the matlab scripts are attached in a zip file.
Attachment 1: mode-track.pdf
mode-track.pdf
Attachment 2: trends.pdf
trends.pdf
Attachment 3: mcmodetrack.zip
  41   Wed Oct 31 19:26:08 2007 Andrey RodionovRoutineGeneralPhotographs of "Mode-Cleaner Entrance"

Here are the pictures of "inside the chamber".
Attachment 1: MC-Pictures-1.pdf
MC-Pictures-1.pdf MC-Pictures-1.pdf MC-Pictures-1.pdf MC-Pictures-1.pdf
Attachment 2: MC-Pictures-2.pdf
MC-Pictures-2.pdf MC-Pictures-2.pdf MC-Pictures-2.pdf MC-Pictures-2.pdf
Attachment 3: MC-Pictures-3.pdf
MC-Pictures-3.pdf MC-Pictures-3.pdf MC-Pictures-3.pdf MC-Pictures-3.pdf
Attachment 4: MC-Pictures-4.pdf
MC-Pictures-4.pdf MC-Pictures-4.pdf MC-Pictures-4.pdf MC-Pictures-4.pdf
Attachment 5: MC-Pictures-5.pdf
MC-Pictures-5.pdf MC-Pictures-5.pdf MC-Pictures-5.pdf MC-Pictures-5.pdf
Attachment 6: MC-Pictures-6.pdf
MC-Pictures-6.pdf MC-Pictures-6.pdf MC-Pictures-6.pdf MC-Pictures-6.pdf
Attachment 7: MC-Pictures-7.pdf
MC-Pictures-7.pdf MC-Pictures-7.pdf MC-Pictures-7.pdf MC-Pictures-7.pdf
Attachment 8: MC-Pictures-8.pdf
MC-Pictures-8.pdf MC-Pictures-8.pdf MC-Pictures-8.pdf MC-Pictures-8.pdf
Attachment 9: MC-Pictures-9.pdf
MC-Pictures-9.pdf MC-Pictures-9.pdf
  44   Thu Nov 1 09:17:27 2007 steveRoutineVACvent 64
Yesterday before vent I could not lock MC, therfore I could not measure the
transmitted power at MC2
The vent went well. We had lots of help.

We could not find the Nikon D40
PLEASE BORROW THINGS when taking them away
and bring them back promtly.

The laser was turned off for better visibility.

I see clean room frorks laying around here and there.
Please put them away so we do not carry excess particles into the chamber.
Attachment 1: vent64.jpg
vent64.jpg
  32   Tue Oct 30 19:32:13 2007 tobinProblem FixedComputersconlogger restarted
I noticed that the conlogger wasn't running. It looks like it hasn't been running since October 11th. I modified the restart_conlogger script to insist that it run on op340m instead of op440m, and then ran it on op340m.
  34   Wed Oct 31 08:33:54 2007 ranaProblem FixedSUSVent measurements
There was a power outage during the day yesterday; whoever was around should post something here about the
exact times. Andrey and David and Tobin got the computers back up - there were some hiccups which you can
read about in David's forthcoming elog entry.

We restarted a few of the locking scripts on op340m: FSSSlowServo, MCautolocker. Along with the updates
to the cold restart procedures we have to put an entry in there for op340m and a list of what scripts
to restart.

David tuned up the FSS Slow PID parameters a little; he and Andrey will log some entry about the proper
PID recipe very soon. We tested the new settings and the step response looks good.

We got the MC locking with no fuss. The 5.6 EQ in San Francisco tripped all of the watchdogs and I upped
the trip levels to keep them OK. We should hound Rob relentlessly to put the watchdog rampdown.pl into
the crontab for op340m.
  36   Wed Oct 31 08:38:35 2007 ranaProblem FixedIOOMC autolocker
The MC was having some trouble staying locked yesterday. I tracked this down to some steps in the last
half of the mcup script; not sure exactly which ones.

It was doing something that made the FAST of the PSL go to a rail too fast for the SLOW to fix.
So, I broke the script in half so that the autolocker only runs the first part. We'll need to
fix this before any CM locking can occur.

We also need someone to take a look at the FSS Autolocker; its ill.
  5   Fri Oct 19 16:11:38 2007 pkpOtherOMCOMC PZT response
Sam and I locked the laser to the OMC cavity and looked at the error signal as a function of the voltage applied to the OMC PZT.
Here are two plots showing the response as a function of frequency from 1 kHz to 100 kHz and another high-res response in the region of 4.5 kHz to 10 kHz.
Attachment 1: fullspec.jpg
fullspec.jpg
Attachment 2: 4.5to10.jpg
4.5to10.jpg
Attachment 3: 4.5to10.pdf
4.5to10.pdf
Attachment 4: fullres.pdf
fullres.pdf
  6   Sat Oct 20 11:54:13 2007 waldmanOtherOMCOMC and OMC-SUS work
[Rich, Chub, Pinkesh, Chris, Sam]

Friday the 18th was a busy day in OMC land. Both DCPDs were mounted to the glass breadboard and the OMC-SUS structure was rebuilt to the point that an aluminum dummy mass is hanging, unbalanced. The OSEMs have not be put on the table cloth yet, but everything is hanging free. As for the DCPDs, if you recall one beam is 3mm off center from the DCPD tombstone. Fortunately, one DCPD is nearly 3mm offcenter from the case in the right direction, so the errors nearly cancel. The DCPD is too high, so the beam isn't quite centered, but they're close. We'll get photos of the beam positions in someday. Also, the DC gain between the two PDs is, at first glance, different by 15%. DCPD1, the one seen in transmission has 315 mV of signal while DCPD2 has 280 mV. Not sure why, could be because of beam alignment or tolerances in the Preamp or the angle incident on the diode or the QE of the diodes. The glass cans have *not* been removed.
  8   Mon Oct 22 19:27:14 2007 pkpOtherOMCPZT calibration/ transfer function.
We measured the PZT transfer function by comparing the PZT response of the circuit with the cavity in the loop, with that of the circuit without the cavity in the loop. Basically measure the transfer function of the whole loop with the laser/PZT and Op-amps in it. Then take another measurement of the transfer function of everything else besides the PZT and from both these functions, we can calculate the PZT response.

The calibration was done by using the error signal response to a triangular wave of volts applied to the PZT. A measurement of the slope of the error signal , which has three zero-crossings as the cavity sweeps through the sidebands, gives us the Volts/Hz response. In order to derive a frequency calibration of the x axis, we assume that the first zero crossing corresponds to the first side band (-29.5 MHz) and the third one corresponds with the other sideband (+29.5 MHz). And then by using the fact that we know the response of the cavity to a constant frequency shift, we can use the Volts/Hz measurement to calculate the Volts/nm calibration. The slope that was calculated was 3.2e-6 V/Hz and using the fact that the cavity is 1 m in length and the frequency is 1064 nm, we get a calibration of 0.9022 V/nm.

Attachment 1: calib.pdf
calib.pdf
Attachment 2: calibpzt2.pdf
calibpzt2.pdf
Attachment 3: all2.pdf
all2.pdf
Attachment 4: noPZT2.pdf
noPZT2.pdf
  9   Tue Oct 23 09:01:00 2007 ranaOtherOMCPZT calibration/ transfer function.
Are you sure that the error signal sweep is not saturated on the top ends? This is usually the downfall
of this calibration method.
  10   Tue Oct 23 11:08:20 2007 steveOtherGeneralbrush fires
There are big brush fires around LA
40 days plot show no effect in the 40m lab
Attachment 1: brushfires.jpg
brushfires.jpg
  11   Wed Oct 24 01:43:32 2007 Andrey RodionovOtherGeneralPDF-file -> Will report about first results for XARM during Wednesday meeting

Here is the pdf-file with some graphs showing first results for XARM optimization.

We will discuss alltogether during our Wednesday meeting which starts at 2.40PM. Probably it would be necessary to project this pdf-file to the big screen,
so someone should bring laptop and probably connect it to the projector. I do not have a laptop.

See you on that meeting.
Attachment 1: Andrey_October_24.pdf
Andrey_October_24.pdf Andrey_October_24.pdf Andrey_October_24.pdf Andrey_October_24.pdf Andrey_October_24.pdf Andrey_October_24.pdf Andrey_October_24.pdf Andrey_October_24.pdf
  12   Wed Oct 24 08:58:09 2007 steveOtherPSLlaser headtemp is up
C1:PSL-126MOPA_HTEMP is 19.3C

Half of the chiller's air intake was covered by loose paper
Attachment 1: htempup.jpg
htempup.jpg
  14   Thu Oct 25 17:52:45 2007 waldmanOtherOMCOMCs with QPDs
[Rich, Chub, Pinkesh, Sam]

Yesterday we got the QPD, OTAS, and PZT cabling harness integrated with the OMC. We found a few things out, not all of them good. The QPDs went on no problem and could be fairly well aligned by hand. We "aligned" them by looking at all four channels of the QPD on the scope and seeing that there is signal. Since the beam is omega = 0.5 mm, this is a reasonable adjustment. We then connected the OTAS connector to the OTAS and found that the heater on the OTAS was bonded on about 30 degrees rotated from its intended position. This rotated the connector into the beam and caused a visible amount of scattering. This wasn't really a disaster until I removed the connector from the heater and broke the heater off of the aluminum parts of the OTAS. Two steps backwards, one step forward. After the OMC, OMC-SUS integration test we will re-bond the heater to the aluminum using VacSeal. In the meantime, the OMC has been moved to Bridge 056 for integration with the OMC-SUS. More on that as we make progress.
  16   Thu Oct 25 23:35:36 2007 waldmanOtherOMCHang the OMC!
[Pinkesh, Sam]

We tried, convicted and hung the OMC today. The OMC was found guilty of being overweight, and unsymmetrically balanced. The unsymmetry was kind of expected and was corrected with a hefty stack of counterweights positioned over the counterweighting holes. The stacks will be measured at some future date and correctly sized objects machined. The overweightness showed up when the level hanging breadboard was about 5 mm low. This showed up in the board height above the table as well as the OSEM flag positions within their holes. The problem was remedied with a liposuction of the intermediate mass. We removed both small vertical cylinder weights that Chris added, and then we removed the heavy steel transverse weight that can be used to adjust the tip around the long axis (I forgot what its called).

The top of the breadboard ended up about 154 mm off the table. The breadboard is 39 mm thick, and the optics are centered (30 - 12.7) = 17.3 mm below the surface for a as hanging beams height of 154 -39 - 17.3 = 97.7 mm or about an 0.150 inches lower than we were aiming for. Can I get a refund?

We screwed up in multiple ways:
  • The slotted disks that capture the wires do not have the alignment bore used to center the wire in the hole
  • We didn't correctly route the far field QPD cable so it runs funny
  • We didn't have a tool which could be used to get two of the DCPD preamp box mounting screws (which are M3's chub!)
  • We don't have the cable clamps to tie off the electrical cables to the intermediate mass
  • We don't have any of the cabling from the OMC-SUS top to the rack so we can't test anything
  • We haven't uploaded pretty pictures for all to see

We left the OMC partially suspended by the OMC-SUS and partly resting on the installation lab jacks which are currently acting as EQ stops. After we fix the cabling we will more permanently hang it. PS, It looks like the REFL beam extraction will be tricky so we need to get on that....
Attachment 1: IMG_1483.jpg
IMG_1483.jpg
Attachment 2: IMG_1481.jpg
IMG_1481.jpg
  19   Fri Oct 26 17:34:43 2007 waldmanOtherOMCOMC + earthquake stops

[Chub, chris, Pinkesh, Sam]

Last night we hugn the OMC for the first time and came up with a bunch of pictures and some problems. Today we address some of the problems and, of course, make new problems. We replaced the flat slotted disks with the fitted slotted disks that are made to fit into the counterbore of the breadboard. This changed the balance slightly and required a more symmetric distribution of mass. It probably did not change the total mass very much. We did find that the amount of cable hanging down strongly affected the breadboard balance and may also have contributed to the changing balance.

We also attached earthquake stops and ran into a few problems:

  • The bottom plate of the EQ stops is too thick so that it bumps into the tombstones
  • The vertical member on the "waist" EQ stops is too close to the breadboard, possibly interfering with the REFL beam
  • The "waist" EQ stops are made from a thin plate that doesn't have enough thickness to mount helicoils in
  • Helicoil weren't loaded in the correct bottom EQ stops
  • The DCPD cable loops over the end EQ stop looking nasty but not actually making contact

However, with a little bit of jimmying, the EQ stops are arrayed at all points within a few mm of the breadboard. Meanwhile, Chub has cabled up all the satellite modules and DCPD modules and Pinkesh is working on getting data into the digital system so we can start playing games. Tonight, I intend to mount a laser in Rana's lab and fiber couple a beam into the 056 room so we can start testing the suspended OMC.
ELOG V3.1.3-