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ID Date Authordown Type Category Subject
  14228   Thu Oct 4 00:44:50 2018 yukiConfigurationASCAI board improvement

[ Yuki, Gautam ]

I made a cable which connects DAC port (40 pins) and AI board (25 pins). I will check if it works.

Tomorrow I will change setup for improvement of AUX Y-end green locking. Any optics for IR will not be moved in my design, so this work doesn't affect Y-arm locking with main beam. 
While doing this work, I will do:

  • check if the cable works
  • make another cable which connects AI board (10 pins) and PZT driver (10 pins).
  • check if eurocate in Y-rack (IY4?) applies +/-5V, +/-15V and +/-24V. It will be done using an expansion card.
  • improve alignment servo for X-end.
  • setup alignment servo for Y-end.
  • about optical loss measurement.  
  14230   Thu Oct 4 22:15:30 2018 yukiConfigurationASCY-end table upgrade

Before changing setup at Y-end table, I measured the status value of the former setup as follows. These values will be compared to those of upgraded setup.

  • beam power going into doubling crystal (red12): 20.9 mW with filter, 1064nm
  • beam power going out from doubling crystal (red12): 26.7 mW with filter, 532nm
  • beam power going into faraday isolator (green5): 0.58 mW without filter, 532nm
  • beam power going out from faraday isolator (green5): 0.54 mW without filter, 532nm
  • beam power going to ETMY: 0.37 mW without filter, 532nm
  • beam power of transmitted green light of Y-arm, which was measured by C1:ALS-TRY_OUT: 0.5 (see attachment #1)

(These numbers are shown in the attachment #2.)

The setup I designed is here. It can bring 100% mode-matching and good separation of degrees of TEM01, however I found a probrem. The picture of setup is attached #3. You can see the reflection angle at Y7 and Y8 is not appropriate. I will consider the schematic again.

Attachment 1: AUXYGreenLock20180921.jpg
AUXYGreenLock20180921.jpg
Attachment 2: Pic_FormerSetup.jpeg
Pic_FormerSetup.jpeg
Attachment 3: Pic_CurrentSetup1004.jpg
Pic_CurrentSetup1004.jpg
  14232   Fri Oct 5 17:32:38 2018 yukiConfigurationASCY-end table upgrade

I measured it with the wrong setting of a powermeter. The correct ones are here:

  • beam power going into doubling crystal (red12): 240 mW, 1064nm
  • beam power transmitted dichroic mirror (Y5): 0.70 mW, 532nm
  • beam power going into faraday isolator (green5): 0.58 mW, 532nm
  • beam power going out from faraday isolator (green5): 0.54 mW, 532nm
  • beam power going to ETMY: 0.37 mW, 532nm
  • beam power of transmitted green light of Y-arm, which was measured by C1:ALS-TRY_OUT: 0.5 (see attachment #1)

The calculated conversion efficiency of SHG crystal is 1.2%W.

  14234   Fri Oct 5 22:49:22 2018 yukiConfigurationASCY-end table upgrade

I designed a new layout. It has good mode-matching efficiency, reasonable sensitivity to component positions, good Gouy phase separation. I'm setting optics in the Y-end table. The layout will be optimized again after finishing (rough) installation.  (The picture will be posted later)

  14236   Sun Oct 7 22:30:42 2018 yukiConfigurationLSCYarm Green locking was recovered

I finished installation of optics in the Y-end and recovered green locking. Current ALS-TRY_OUTPUT is about 0.25, which is lower than before. So I still continue the alignment of the beam. The simulation code was attached. (Sorry. The optic shown as QWP2 is NOT QWP. It's HWP.)

Attachment 1: Pic_NewLayout1007.jpg
Pic_NewLayout1007.jpg
Attachment 2: YendGreenModeMatching.zip
  14237   Mon Oct 8 00:46:35 2018 yukiConfigurationASCY-end table upgrade
Quote:

I measured it with the wrong setting of a powermeter. The correct ones are here:

  • beam power going into doubling crystal (red12): 240 mW, 1064nm
  • beam power transmitted dichroic mirror (Y5): 0.70 mW, 532nm
  • beam power going into faraday isolator (green5): 0.58 mW, 532nm
  • beam power going out from faraday isolator (green5): 0.54 mW, 532nm
  • beam power going to ETMY: 0.37 mW, 532nm
  • beam power of transmitted green light of Y-arm, which was measured by C1:ALS-TRY_OUT: 0.5 (see attachment #1)

After installation I measured these power again.

  • beam power going into doubling crystal: 241 mW, 1064nm
  • beam power transmitted dichroic mirror: 0.70 mW, 532nm
  • beam power going into faraday isolator: 0.56 mW, 532nm
  • beam power going out from faraday isolator: 0.53 mW, 532nm
  • beam power going to ETMY: 0.36 mW, 532nm

There is a little power loss. That may be because of adding one lens in the beam path. I think it is allowable margin.

  14240   Tue Oct 9 23:03:43 2018 yukiConfigurationLSCYarm Green locking was recovered

[ Yuki, Gautam, Steve ]

To align the green beam in Y-end these hardware were installed:

  • PZT mirrors in Y-end table
  • PZT driver in 1Y4 rack
  • Anti-Imaging board in 1Y4 rack
  • cables (DAC - AIboard - PZTdriver - PZT)
  • high voltage supplier 

I made sure that DAC CH9~16 and cable to AI-board worked correctly. 

When we applied +100V to PZT driver and connected DAC, AI-board and PZT drive, the output voltage of the driver was not correct. I'll check it tomorrow.

Attachment 1: Pic_1Y4.jpg
Pic_1Y4.jpg
Attachment 2: Pic_PZTcable.jpg
Pic_PZTcable.jpg
  14241   Wed Oct 10 12:38:27 2018 yukiConfigurationLSCAll hardware was installed

I connected DAC - AIboard - PZTdriver - PZT mirrors and made sure the PZT mirrors were moving when changing the signal from DAC. Tomorrow I will prepare alignment servo with green beam for Y-arm.

  14243   Thu Oct 11 13:40:51 2018 yukiUpdateComputer Scripts / Programsloss measurements
Quote:

This is the procedure I follow when I take these measurements for the XARM (symmetric under XARM <-> YARM):

  1. Dither-align the interferometer with both arms locked. Freeze outputs when done.
  2. Misalign ETMY + ITMY.
  3. ITMY needs to be misaligned further. Moving the slider by at least +0.2 is plentiful to not have the other beam interfere with the measurement.
  4. Start the script, which does the following:
    1. Resume dithering of the XARM
    2. Check XARM dither error signal rms with CDS. If they're calm enough, proceed.
    3. Freeze dithering
    4. Start a new set of averages on the scope, wait T_WAIT (5 seconds)
    5. Read data (= ASDC power and MC2 trans) from scope and save
    6. Misalign ETMX and wait 5s
    7. Read data from scope and save
    8. Repeat desired amount of times
  5. Close the PSL shutter and measure the PD dark levels

Information for the armloss measurement:

  • Script which gets the data:  /users/johannes/40m/armloss/scripts/armloss_scope/armloss_dcrefl_asdcpd_scope.py
  • Script which calculates the loss: /users/johannes/40m/armloss/scripts/misc/armloss_AS_calc.py
  • Before doing the procedure Johannes wrote you have to prepare as follows:
    • put a PD in anti-symmetric beam path to get ASDC signal.
    • put a PD in MC2 box to get tranmitted light of IMC. It is used to normalize the beam power.
    • connect those 2 PDs to oscilloscope and insert an internet cable to it.
  • Usage: python2 armloss_dcrefl_asdcpd_scope.py [IP address of Scope] [ScopeCH for AS] [ScopeCH for MC] [Num of iteration] [ArmMode]

Note: The scripts uses httplib2 module. You have to install it if you don't have.

The locked arms are needed to calculate armloss but the alignment of PMC is deadly bad now. So at first I will make it aligned. (Gautam aligned it and PMC is locked now.) 

gautam: The PMC alignment was fine, the problem was that the c1psl slow machine had become unresponsive, which prevented the PMC length servo from functioning correctly. I rebooted the machine and undid the alignment changes Yuki had made on the PSL table.

  14245   Fri Oct 12 12:29:34 2018 yukiUpdateComputer Scripts / Programsloss measurements

With Gautam's help, Y-arm was locked. Then I ran the script "armloss_dcrefl_asdcpd_scope.py" which gets the signals from oscilloscope. It ran and got data, but I found some problems.

  1. It seemed that a process which makes arm cavity mislaigned in the script didn't work.
  2. The script "armloss_dcrefl_asdcpd_scope.py" gets the signal and the another script "armloss_AS_calc.py" calculates the arm loss. But output file the former makes doesn't match with the type the latter requires. A script converts format is needed.

Anyway, I got the data needed so I will calculate the loss after converting the format.

  14248   Fri Oct 12 20:20:29 2018 yukiUpdateComputer Scripts / Programsloss measurements

I ran the script for measuring arm-loss and calculated rough Y-arm round trip loss temporally. The result was 89.6ppm. (The error should be considered later.)

The measurement was done as follows:

  1. install hardware
    1. Put a PD (PDA520) in anti-symmetric beam path to get ASDC signal.
    2. Use a PD (PDA255) in MC2 box to get tranmitted light of IMC. It is used to normalize the beam power.
    3. Connect those 2 PDs to oscilloscope (IP: 192.168.113.25) and insert an internet cable to it.
  2. measure DARK noise
    1. Block beam going into PDs with dampers and turn off the room light.
    2. Run the script "armloss_dcrefl_acdcpd_scope.py" using "DARK" mode.
  3. measure the ASDC power when Y-arm locked and misaligned
    1. Remove dampers and turn off the room light.
    2. Dither-align the interferometer with both arms locked. Freeze outputs when done. (Click C1ASS.adl>!MoreScripts>ON and click C1ASS.adl>!MoreScripts>FreezeOutputs.)
    3. Misalign ETMX + ITMX. (Just click "Misalign" button.)
    4. Further misalign ITMX with the slider. (see previous study: ITMX needs to be misaligned further. Moving the slider by at least +0.2 is plentiful to not have the other beam interfere with the measurement.)
    5. Start the script "armloss_dcrefl_acdcpd_scope.py" using "ETMY" mode, which does the following:
      1. Resume dithering of the YARM.
      2. Check YARM dither error signal rms with CDS. If they're calm enough, proceed. (In the previous study the rms threshold was 0.7. Now "ETM_YAW_L_DEMOD_I" signal was 15 (noisy), then the threshold was set 17.)
      3. Freeze dithering.
      4. Start a new set of averages on the scope, wait T_WAIT (5 seconds).
      5. Read data (= ASDC power and MC2 trans) from scope and save.
      6. Misalign ETMY and wait 5s. (I added a code which switchs LSC mode ON and OFF.)
      7. Read data from scope and save.
      8. Repeat desired amount of times.
  4. calculate the arm loss
    1. Start the script "armloss_AS_calc.py", whose content is follows:
      • requires given parameters: Mode-Matching effeciency, modulation depth, transmissivity. I used the same value as Johannes did last year, which are (huga)
      • reads datafile of beam power at ASDC and MC2 trans, which file is created by "armloss_dcrefl_acdcpd_scope.py".
      • calculates arm loss from the equation (see 12528 and 12854).

Result:

YARM
('AS_DARK =', '0.0019517200000000003') #dark noise at ASDC 
('MC_DARK =', '0.02792') #dark noise at MC2 trans
('AS_LOCKED =', '2.04293') #beam power at ASDC when the cavity was locked 
('MC_LOCKED =', '2.6951620000000003')
('AS_MISALIGNED =', '2.0445439999999997') #beam power at ASDC when the cavity was misaligned
('MC_MISALIGNED =', '2.665312')

\hat{P} = \frac{P_{AS}-P_{AS}^{DARK}}{P_{MC}-P_{MC}^{DARK}} #normalized beam power 

\hat{P}^{LOCKED}=0.765,\ \hat{P}^{MISALIGNED}=0.775,\ \mathcal{L}=89.6\ \mathrm{ppm}

Comments:

  • "ETM_YAW_L_DEMOD_I_OUTPUT" was little noisy even when the arm was locked.
  • The reflected beam power when locked was higher than when misaligned. It seemed strange for me at first. Johannes suggested that it was caused by over-coupling cavity. It is possible when r_{ETMY}>>r1_{ITMY}.
  • My first (wrong) measurement said the arm loss was negative(!). That was caused by lack of enough misalignment of another arm mirrors. If you don't misalign ITMX enough then the beam or scattered light from X-arm would bring bad. The calculated negative loss would be appeared only when \frac{\hat{P}^{LOCKED}}{\hat{P}^{MISALIGNED}} > 1 + T_{ITM}
  • Error should be considered.
  • Parameters given this time should be measured again. 
  14251   Sat Oct 13 20:11:10 2018 yukiUpdateComputer Scripts / Programsloss measurements
Quote:

the script "armloss_AS_calc.py",

  • "ETM_YAW_L_DEMOD_I_OUTPUT" was little noisy even when the arm was locked.
  • The reflected beam power when locked was higher than when misaligned. It seemed strange for me at first. Johannes suggested that it was caused by over-coupling cavity. It is possible when r_{ETMY}>>r1_{ITMY}.

Some changes were made in the script for getting the signals of beam power:

  • The script sees "C1:ASS-X(Y)ARM_ETM_PIT/YAW_L_DEMOD_I_OUTPUT" and stops running until the signals become small, however some offset could be on the signal. So I changed it into waiting until (DEMOD - OFFSET) becomes small. (Yesterday I wrote ETM_YAW_L_DEMOD_I_OUTPUT was about 15 and was little noisy. I was wrong. That was just a offset value.)
  • I added a code which stops running the script when the power of transmitted IR beam is low. You can set this threshold. The nominal value of "C1:LSC-TRX(Y)_OUT16" is 1.2 (1.0), so the threshold is set 0.8 now.  

In the yesterday measurement the beam power of ASDC is higher when locked than when misaligned and I wrote it maybe caused by over-coupled cavity. Then I did a calculation as following to explain this:

  • assume power transmissivity of ITM and ETM are 1.4e-2 and 1.4e-5.
  • assume loss-less mirror, you can calculate amplitude reflectivity of ITM and ETM.
  • consider a cavity which consists two mirrors and is loss-less, then \frac{E_{r}}{E_{in}} = \frac{-r_1+r_2e^{i\phi}}{1-r_1r_2e^{i\phi}} holds. r1 and r2 are amplitude reflectivity of ITM and ETM, and E is electric filed.
  • Then you can calculate the power of reflected beam when resonated and when anti-resonated. The fraction of these value is \frac{P_{RESONANT}}{P_{ANTI-RESO}} = 0.996, which is smaller than 1.
  • I found this calculation was wrong! Above calculatation only holds when cavity is aligned, not when misaligned. 99.04% of incident beam power reflects when locked, and (100-1.4)% reflects when misaligned. The proportion is P(locked)/P(misaligned)=1.004, higher than 1.

 

  14254   Mon Oct 15 10:32:13 2018 yukiUpdateComputer Scripts / Programsloss measurements

I used these values for measuring armloss:

  • Transmissivitity of ITM = 1.384e-2 * (1 +/- 1e-2) 
  • Transmissivitity of ETM = 13.7e-6 * (1 +/- 5e-2)
  • Mode-Matching efficiency of XARM = 0.912 * (1 +/- 2e-2)
  • Mode-Matching efficiency of YARM = 0.867 * (1 +/- 2e-2)
  • modulation depth m1 (11MHz) = 0.179 * (1 +/- 2e-2)
  • modulation depth m2 = 0.226 * (1 +/- 2e-2),

then the uncertainties reported by the individual measurements are on the order of 6 ppm (~6.2 for the XARM, ~6.3 for the YARM). This accounts for fluctuations of the data read from the scope and uncertainties in mode-matching and modulation depths in the EOM. I made histograms for the 20 datapoints taken for each arm: the standard deviation of the spread is over 6ppm. We end up with something like:

XARM: 123 +/- 50 ppm
YARM: 152+/- 50 ppm

This result has about 40% of uncertaintities in XARM and 33% in YARM (so big... no).

In the previous measurement, the fluctuation of each power was 0.1% and the fluctuation of P(Locked)/P(misaligned) was also 0.1%. Then the uncertainty was small. On the other hand in my measurement, the fluctuation of power is about 2% and the fluctuation of P(Locked)/P(misaligned) is 2%. That's why the uncertainty became big.

We want to measure tiny value of loss (~100ppm). So the fluctuation of P(Locked)/P(misaligned) must be smaller than 1.6%.

(Edit on 10/23)
I think the error is dominated by systematic error in scope. The data of beam power had only 3 degits. If P(Locked) and P(misaligned) have 2% error, then
\frac{P_L}{P_M}\frac{1}{1+T_{\mathrm{ITM}}} = 0.99(3).
You have to check the configuration of scope.

Attachment 1: XARM_20181015_1500.pdf
XARM_20181015_1500.pdf
Attachment 2: YARM_20181015_1500.pdf
YARM_20181015_1500.pdf
  14255   Mon Oct 15 12:52:54 2018 yukiUpdateComputer Scripts / Programsadditional comments
Quote:

but there's one weirdness: It get's the channel offset wrong. However this doesn't matter in our measurement because we're subtracting the dark level, which sees the same (wrong) offset.

When you do this measurement with oscilloscope, take care two things:

  1. set y-range of scope as to every signal fits in display: otherwise the data sent from scope would be saturated.
  2. set y-position of scope to the center and don't change it; otherwise some offset would be on the data.
  14257   Mon Oct 15 20:11:56 2018 yukiConfigurationASCY end table upgrade plan

Final Procedure Report for Green Locking in YARM:

Purpose

The current setup of AUX Y-arm Green locking has to be improved because:

  • current efficiency of mode matching is about 50%
  • current setup doesn't separate the degrees of freedom of TEM01 with PZT mirrors (the difference of gouy phase between PZT mirrors should be around 90 deg) 
  • we want to remotely control PZT mirrors for alignment

What to do

  • Design the new setup and order optices needed (finished!)
      - As the new setup I designed, adding a new lens and slightly changing the position of optics are only needed. The new lens was arrived here.
  • Check electronics (PZT, PZT driver, high voltage, cable, anti-imaging board) (finished!)
      
    - All electronics were made sure performing well.
      - The left thing to do is making a cable. (Today's tasks)
  • Calibrate PZT mirror [mrad/V] (finished!)
      
    - The result was posted here --> elog:40m/14224.
  • Measure the status value of the current setup (power of transmitted light ...etc) (finished!)
  • Install them in the Y-end table and align the beam (Almost finished!) (GTRY signal is 0.3 which means Mode-Matching efficiency is about 30%. It should be improved.)
  • Measure the status value of the new setup (finished!)
  • Prepare the code of making alignment automaticaly
    • see sitemap.adl>ASC>c1asy. I prepared medm. If you move PZT SLIDERS then you can see the green beam also moves.
    • Preparing filters is needed. You can copy them from C1ASX.
    • Note that now you cannot use C1ASX servo because filters are not applied.
  14258   Tue Oct 16 00:44:29 2018 yukiUpdateComputer Scripts / Programsloss measurements

The scripts for measuring armloss are in the directory "/opt/rtcds/caltech/c1/scripts/lossmap_scripts/armloss_scope".

  • armloss_derefl_asdcpd_scope.py: gets data and makes ascii file.
  • armloss_AS_calc.py: calculates armloss from selected a set of files.
  • armloss_calc_histogram.py: calculates armloss from selected files and makes histogram.
  14260   Wed Oct 17 20:46:24 2018 yukiConfigurationASCY end table upgrade plan

To do for Green Locking in YARM:

The auto-alignment servo should be completed. This servo requires many parameters to be optimized: demodulation frequency, demodulation phase, servo gain (for each M1/2 PIT/YAW), and matrix elements which can remove PIT-YAW coupling. 

  14280   Wed Nov 7 05:16:16 2018 yukiUpdateComputer Scripts / Programsarm loss measuremenents

Please check your data file and compare with those Johannes made last year. I think the power in your data file may have only three-disits and flactuate about 2%, which brings huge error. (see elog: 40m/14254)

Quote:

On running the script again, I'm getting negative values for the loss. 

  12825   Mon Feb 13 17:19:41 2017 yinziConfiguration configuring ethernet for raspberry pi

Gautam and I were able to get the Raspberry Pi up and running today, including being able to ssh into it from the control room.

Below are some details about the setup/procedure that might be helpful to anyone trying to establish Ethernet connection for a new RPi, or a new operating system/SD card.

Here is the physical setup:

 

The changes that need to be made for a new Raspbian OS in order to communicate with it over ssh are as follows, with links to tutorials on how to do them:

1. Edit dhcpcd.conf file: https://www.modmypi.com/blog/how-to-give-your-raspberry-pi-a-static-ip-address-update

2. Edit interfaces file: https://www.mathworks.com/help/supportpkg/raspberrypi/ug/getting-the-raspberry_pi-ip-address.html

3. Enable ssh server: http://www.instructables.com/id/Use-ssh-to-talk-with-your-Raspberry-Pi/

 

The specific addresses for the RPi we set up today are:

IP Address: 192.168.113.107

Gateway/Routers/Domain Name Servers: 192.168.113.2

Netmask: 255.255.255.0

GV: I looked through /etc/var/bind/martian.hosts on chiara and decided to recycle the IP address for Domenica.martian as no RPis are plugged in right now... I'm also removing some of the attachments that seem to have been uploaded multiple times.

  14825   Fri Aug 2 17:07:33 2019 yehonathan, gautamUpdateLoss Measurement 

We run a loss measurement on the Y arm with 50 repetitions.

  14816   Mon Jul 29 19:08:55 2019 yehonathanUpdateLoss MeasurementReviving loss measurement by reflection

1. X arm is totally misaligned in order to measure the Y arm loss using the reflection method. Each measurement round consists of measuring the reflected power when the Y arm is aligned and when it is misaligned.

2. The measurement script used is /scripts/lossmap_scripts/armLoss/measureArmLoss.py. It generates a log file in the /logs folder specifying the alignment and misalignment times.

3. The data extraction script dlData.py processes the raw data in the log file and creates a hdf5 file in the /Data folder conataining the data of the measurement it self.

4. dlData.py labels the the aligned and misaligned datas incorrectly when the number of measurement is odd. I use only even number of measurements then.

5. In order to clip the chaotic transition between the aligned and misaligned states I use tDur attribute smaller than the actual sleep time used in the measurement script itself.

6. plotData.py (written by Gautam) and AnalyzeLossData.ipynb (written by me) can be used to calculate the loss and to plot some analyses (see https://nodus.ligo.caltech.edu:8081/40m/14568). They give roughly the same answer. The descripancy can be explained by the different modulation and ITM transmissions used.

7. I take a measurement of 8 repeatitions. I plot the measured reflected power alternating between the aligned and misaligned states. 

I find that the reflected power is repeatable to within 1%.

This is consistent with the transmission data plotted here which is also repeatable to within 1%.

8. I take an overnight measurement of 100 repeatitions.

  14827   Mon Aug 5 14:47:36 2019 yehonathanUpdateLoss Measurement 

Summary:

I analyze the 100 reps loss measurement of the Y arm using the AnalyzeLossData.ipynb notebook.

The mean of the measured loss is ~ 100ppm and the variation between the repititions is ~ 27%.

 

In Detail

In the real measurement the misaligned and locked states are repeatedly switched between each other. I plot the misaligned and locked PD readings seperately over time.

There seems to be a drift that is correlated between the two readings. This is probably a drift in the power after the MC2. To verify, I plot the ratio between those readings and find no apparent drift:

The variation in the ratio is less than 1%. The loss figure, computed to be 1 minus this ratio times a big number, give a much worse variation. I plot the histogram of the loss figure at each repitition (excluding extremely bad measurements):

The mean is ~ 100ppm. And the variation is ~ 27%.

  Draft   Mon Aug 5 16:28:41 2019 yehonathanUpdateLoss Measurementwhat is going on with the loss measurements ?

We hypothesize that the systematic error in the loss measurement can come from the fact that the requirement on the alignment of the cavity mirrors is not stringent enough.

We repeat the loss measurement with 50 measurements. This time we change the thresholds for the error signals of the dither-align in the measureArmLoss.py file from 0.5 to 0.3.

We repeat the analysis done before:

We plot the reflected power of the two states on top of each other:

This  time it appears there was no drift. The histogram of the loss measurement:

The mean is 104ppm and the variation is 27%.

What I notice this time is that the PD readings in the aligned and misaligned states are anti-correlated. This is also true in the previous run (where there was drift) when looking in the short time scales. I plot several time series to demonstrate:

I wonder what can cause this behaviour.

  14830   Mon Aug 5 17:36:04 2019 yehonathanUpdateLoss Measurement 

We check for unexpected drifts in the PD reading (clipping and such). We put a pickoff mirror where the PD used to be and place the PD at the edge of the table such that the beam is focused on it (see attachment).

The arms are completley misaligned. We note the time of start of measurement to be 1249086917.

Attachment 1: 20190805_171511.jpg
20190805_171511.jpg
  14831   Tue Aug 6 14:12:02 2019 yehonathanUpdateComputersmaking rossa great again

cdsutils is not working on rossa.

Import cdsutils produces this error:

In [2]: import cdsutils
---------------------------------------------------------------------------
OSError                                   Traceback (most recent call last)
<ipython-input-2-949babce8459> in <module>()
----> 1 import cdsutils

/ligo/apps/linux-x86_64/cdsutils-480/lib/python2.7/site-packages/cdsutils/__init__.py in <module>()
     53 
     54 try:
---> 55     import awg
     56 except ImportError:
     57     pass

/ligo/apps/linux-x86_64/cdsutils-480/lib/python2.7/site-packages/cdsutils/awg.py in <module>()
     30 """
     31 
---> 32 import sys, numpy, awgbase
     33 from time import sleep
     34 from threading import Thread, Event, Lock

/ligo/apps/linux-x86_64/cdsutils-480/lib/python2.7/site-packages/cdsutils/awgbase.py in <module>()
     17 libawg = CDLL('libawg.so')
     18 libtestpoint = CDLL('libtestpoint.so')
---> 19 libSIStr = CDLL('libSIStr.so')
     20 
     21 ####

/ligo/apps/anaconda/lib/python2.7/ctypes/__init__.pyc in __init__(self, name, mode, handle, use_errno, use_last_error)
    364 
    365         if handle is None:
--> 366             self._handle = _dlopen(self._name, mode)
    367         else:
    368             self._handle = handle

OSError: libSIStr.so: cannot open shared object file: No such file or directory

  14834   Tue Aug 6 16:44:50 2019 yehonathanUpdateLoss Measurement 

I grab 2 hours of the PD measurements using dlData_simple.ipynb in the misaligned state.

I get pretty much a normally distributed reading without drifts (Attachements 1 and 2).

The error in the reading is ~ 0.5%.

 

I am pretty sure this amount of noise is enough to explain the big noise in the Loss figure measurement.

 

The reason is that the loss formula is #(1-P_Locked/P_Misaligned+T1)-T2) where T1 and T2 are the transmissions of the ITM and ETM.

The average of the ratio P_Locked/P_Misaligned is ~ 1.01 for a loss figure of ~ 100ppm.

The standard deviation of the ratio is ~ 1% which is also the standard deviation of the expression in the brackets.

The average of this experssion however is ~ 0.01.

The reduction of the mean amplifies the error in the loss measurments by a factor of a few 10s!

Attachment 1: figure_1.png
figure_1.png
Attachment 2: figure_1-1.png
figure_1-1.png
  15116   Fri Jan 10 19:48:46 2020 yehonathanUpdatePSLAssembly underway for c1psl upgrade

{Yehonathan, Jon}

I finished pre-wiring the PSL chassis. I mounted the Acromags on the DIN rails and labeled them. I checked that they are powered up with the right voltage +24V and that the LEDs behave as expected.

Attachment 1: 20200110_194429.jpg
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Attachment 2: 20200110_194516_HDR.jpg
20200110_194516_HDR.jpg
  15118   Mon Jan 13 16:05:18 2020 yehonathanUpdatePSLAssembly underway for c1psl upgrade

{Yehonathan, Jon}

I configured the Acromag channels according to the Slow Controls Wiki page.

We started testing the channels. Almost at the beginning we notice that the BIO channels are inverted. High voltage when 0. 0 Voltage when 1. We checked several things:

1. We checked the configuration of the BIOs in the windows machine but nothing pointed to the problem.

2. We isolated one of the BIOs from the DIN rail but the behavior persisted.

3. We checked that the voltages that go into the Acromags are correct.

The next step is to power up an isolated Acromag directly from the power supply. This will tell us if the problem is in the chassis or the EPICs DB.

  15120   Tue Jan 14 17:16:43 2020 yehonathanUpdatePSLAssembly underway for c1psl upgrade

{Yehonathan, Jon}

I isolated a BIO Acromag completely from the chassis and powered it up. The inverted behavior persisted.

Turns out this is normal behavior for the XT1111 model.

For digital outputs, one should XT1121. XT1111 should be used for digital inputs.

Slow machines Wiki page was updated along with other pieces of information.

I replaced the XT1111 Acromags with XT1121 and did some rewiring since the XT1121 cannot get the excitation voltage from the DIN rail.

I added an XT1111 Acromag for the single digital input we have in this system.

  15262   Tue Mar 10 14:30:16 2020 yehonathanUpdateSUS 

ETMX was grossly misaligned.

I re-aligned it and the X arm now locks.

7:00PM with Koji

Both the alignment of the X and Y arms was recovered.

~>z avg 10 C1:LSC-TRX_OUT C1:LSC-TRY_OUT
C1:LSC-TRX_OUT 0.9914034307003021
C1:LSC-TRY_OUT 0.9690877735614777

We are running ass for the X arm to recover the X arm alignment.

Meanwhile, i want to block the Y arm trans PD (Thorlabs). To do it, the PD<->QPD thresholds were changed from 5.0/3.0 to 0.5/0.3.

Attachment 1: Screenshot_from_2020-03-10_19-02-31.png
Screenshot_from_2020-03-10_19-02-31.png
  15263   Tue Mar 10 19:58:16 2020 yehonathanUpdateSUS 

I returned the triggering threshold to normal values (5/3).

Meanwhile, i want to block the Y arm trans PD (Thorlabs). To do it, the PD<->QPD thresholds were changed from 5.0/3.0 to 0.5/0.3.

  15614   Tue Oct 6 07:37:20 2020 yehonathanUpdateWikiNew TIS measurements of 40m Optics

LiYuan has kindly done some Total Integrating Sphere (TIS) measurements on ITMU01 and ITMU02. A summary of the measurement is attached. I uploaded the measurements and some analysis script to nodus at /home/export/home/40m_TIS. I created a Wiki page for the measurements and linked to it from the core optics page.

These TIS measurements look very similar to the TIS of the LIGO optics. Further analysis shows that the scatter loss is 10+/-1.7 ppm for ITMU01 and 8.6+/-0.4 ppm for ITMU02.

In this calculation, a gaussian beam the same size bouncing off the 40m ITMs is assumed to scatter from the mirrors. The error is calculated by moving the beam around randomly with STD of 1mm.

In LiYuan's setup, TIS is measured for scattering angles between 1 and 75 degrees. If we go further and assume that the scatter is Lambertian we can extrapolate that the total loss is 10.9+/-1.9 ppm for ITMU01 and 9.2+/-0.5 ppm for ITMU02.

These measurements complete the loss budget nicely since with the 6ppm loss predicted from the phase maps, the total loss in the arm cavities would be 6+10+10=26ppm which is very close to the 28ppm loss that was measured after the arm cavity optics were cleaned.

Attachment 1: ITMU_sn01-02_tis_1.pdf
ITMU_sn01-02_tis_1.pdf ITMU_sn01-02_tis_1.pdf
  15788   Tue Feb 2 17:09:17 2021 yehonathanUpdateBHDSOS assembly

I set up a working area on the table next to the south flow bench (see attachment). I also brought in a rolling table for some extra space.

I covered all the working surfaces with a foil from the big roll between 1x3 and 1x4.

I took the SOSs, SOS parts and the OSEMS from the MC2 table to the working area.

I cleaned some LN Allen keys with isopropanol and put them on the working table, please don't take them.

Attachment 1: 20210202_165501.jpg
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Attachment 2: 20210202_162452.jpg
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  15816   Thu Feb 18 15:15:12 2021 yehonathanUpdateSUSOSEM testing for SOSs

I am setting up a testing rig for the OSEMs we recently obtained. I found the schematic for the OSEM assembly from which the pin assignment can be read.

I connected the OSEM's pin plate to a female DB15 on a breakout board. I find the pin assignment (attachment 1, sorry for the image quality) to be:

1 PD Cathode
2 LED Anode
3 Coil end
4 PD Anode
5 LED Cathode
6 Coil Start

There are several things that need to be done for each OSEM.

1. Measuring inductance of the coils. I checked that the measurement wires don't add any measurable inductance.

2. Check that the PDs and LEDs are alive (e.g. check forward voltage drop with fluke)

3. Energize the LED and PD.

4. Check PD DC level. For this, I might need the satellite box amplifier.

5. Check LED spot position on the PD.

6. Re-engrave OSEM S/N if needed.

OSEM # Coil Inductance (mH) Coil resistance (ohm) PD forward voltage (V) LED forward voltage (V)
280 2.87 14.1 0.63 1.1
         
         

I still need to figure a sensible scheme for points 3-5.

 

 

Attachment 1: OSEM_Pin_Plate.png
OSEM_Pin_Plate.png
  15837   Wed Feb 24 10:09:16 2021 yehonathanUpdateSUSOSEM testing for SOSs

Yes, my phone camera mirrored the image. Sorry for the confusion.

I see you already uploaded the correct pin assignment.

Quote:

I can't obtain a consistent view between the existing drawings/photographs and your pin assignment. Please review the pin assignment again to check if yours is correct.

Looking from the back side and the wires are going down, the left bottom pin is "Coil Start" and the upper right adjacent pin is "Coil End". (See attachment)
So in your picture 1 should be the coil start and 4 should be the coil end, but they are not according to your table.

 

  16062   Wed Apr 21 11:09:57 2021 yehonathanUpdatePSLLaser amplifier

I went to the TCS lab to take a look at the chillers lying around. I spotted two chillers:

1. Thermoflex1400 (attachment 1,2). Spec sheet.

2. Polyscience Recirculator 6000 series (attachment 3,4). Manual.

The Thermoflex has various communication ports. The Recirculator doesn't have any communication ports, but it is connected to a flow meter with what seems to be an electronic readout (attachment 5). Manual.

Both chillers have similar capacity ~ 4 gallons/minute. Thermoflex has 2 times more reservoir capacity than the Recirculator.

None of them seem to be Bechkoff-ready.

I guess we can have interlock code handling mixed signals Beckhoff+Non beckhoffs?

Attachment 1: 20210420_171606.jpg
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Attachment 2: 20210420_171621.jpg
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Attachment 3: 20210420_171611.jpg
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Attachment 4: 20210420_171629.jpg
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Attachment 5: 20210420_171702.jpg
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  16253   Wed Jul 21 18:08:35 2021 yehonathanUpdateLoss MeasurementLoss measurement

{Gautam, Yehonathan, Anchal, Paco}

We prepared for the loss measurement using DC reflection method. We did the following changes:

1. REFL55_Q was disconnected and replaced with MC_T cable coming from the PD on the MC2 table. The cable has a red tag on it. Consequently we lost the AS beam. We realigned the optics and regained arm locks. The spot on the AS QPD had to be corrected.

2. We tried using AS55 as the PD for the DC measurement but we got ratios of ~ 0.97 which implies losses of more than 100 ppm. We decided to go with the traditional PD520 used for these measurements in the past.

3. We placed the PD520 used for loss measurements in front of the AS55 PD and optimized its position.

4. AS110 cable was disconnected from the PD and connected to PD520 to be used as the loss measurement cable.

5. In 1Y2 rack, AS110 PD cable was disconnected, REFL55_I was disconnected and AS110 cable was connected to REFL55_I channel.

So for the test, the MC transmission was measured at REFL55_Q and the AS DC was measured at REFL55_I.

We used the scripts/lossmap_scripts/armLoss/measArmLoss.py script. Note that this script assumes that you begin with the arm locked.

We are leaving the IFO in the configuration described above overnight and we plan to measure the XARM loss early AM. After which we shall restore the affected electrical and optical paths.


We ran the /scripts/lossmap_scripts/armLoss/measureArmLoss.py script in pianosa with 25 repetitions and a 30 s "duty cycle" (wait time) for the Y arm. Preliminary results give an estimated individual arm loss of ~ 30 ppm (on both X/Y arms) but we will provide a better estimate with this measurement. 

  16371   Fri Oct 1 14:25:27 2021 yehonathanSummarySUSPRM and BS Angular Actuation transfer function magnitude measurements

{Paco, Yehonathan, Hang}

We measured the sensing PRMI sensing matrix. Attachment 1 shows the results, the magnitude of the response is not calibrated. The orthogonality between PRCL and MICH is still bad (see previous measurement for reference).

Hang suggested that since MICH actuation with BS and PRM is not trivial (0.5*BS - 0.34*PRM) and since PRCL is so sensitive to PRM movement there might be a leakage to PRCL when we are actuating on MICH. So there may be a room to tune the PRM coefficient in the MICH output matrix.

Attachment 2 shows the sensing matrix after we changed the MICH->PRM coefficient in the OSC output matrix to -0.1.

It seems like it made things a little bit better but not much and also there is a huge uncertainty in the MICH sensing.

Attachment 1: MICH_PRM_-0.34.png
MICH_PRM_-0.34.png
Attachment 2: MICH_PRM_-0.1.png
MICH_PRM_-0.1.png
  16779   Thu Apr 14 11:52:57 2022 yehonathanSummaryBHDPart IIa of BHR upgrade - POY11 debugging

{JC, Paco, Yehonathan, Ian}

POY lens was moved to infront of the POY steering mirror to make the POU beam focused on the POY11 RFPD. We measured the DC output with an oscilloscope and optimized it with the steering mirrors. We get ~ 16.5mV.

The new lens position blocked the BS OpLev ingoing beam, so we repositioned the OpLev mirrors to make the beam path not hit the lens.

We went to the control room to observe the PDH signal. We observed a series of PDF osscillation and then the signal died infront of our eyes! There is just noise.

We go and check the +/-15V powering the RFPD and we find that the V- is ~ 14V which is good but the V+ was ~ 2.7V which is not.

We went to the PD interface and measure the POY11 output oltages using a breakout board and got the same result.

The PD interface was taken out for inspection. All the OP27 on channel 3 were replaced with new ICs (without need turns out)...


The PD interface card turned out to be OK. What happened is that one of the Kepcos in the RF rack died because its fan crumbled as seen in Attachment #2 (could this be the source of burning smell?). In response, the rack was drawing from the other Kepco (connected in parallel) way too much current  (4A) and the current limiter dropped its voltage from 15V to 2.7V.

The Kepco pair was removed and replaced with a single Sorensen. The POY PDH signal was restored (see attachment).

Attachment 1: Screenshot_2022-04-14_15-53-39.png
Screenshot_2022-04-14_15-53-39.png
Attachment 2: PXL_20220414_220616875.jpg
PXL_20220414_220616875.jpg
  16799   Thu Apr 21 18:18:42 2022 yehonathanUpdateBHDPOX Alignment

{Yehonathan, Paco}

BS, ITMX and ETMX were aligned to get flashing in the X arm.

I aligned the POX beam on the ITMX table using a mixture of the old POP and POX optics. The beam was stirred to the POX11 RFPD. We measure the DC power using a scope but we see nothing. We went and saw that the POX11 cable was not connected to RF rack so we connected it along with some other RFPD cables.

We return but there is still no DC. We ndscope C1:LSC-POX11_I_ERR_DQ C1:LSC-POX11_Q_ERR_DQ and maximize the signal (attachment). The readout is very weak though. It should be as strong as POY which we already observed to have good SNR.

We also noticed that the one of the beam dumps for the POX RFPD is not glued and easily falls down.

Attachment 1: POX11_alignment.png
POX11_alignment.png
  17041   Thu Jul 28 13:09:28 2022 yehonathanUpdateBHDMode matching considerations

The LO beam was found to have a power of 60uW, 10% of the power expected. We are pretty sure about the expectation because the AS beam has a power of 300uW, roughly the expected power. Additionally, the visibility of the MICH fringes in the BHDR is 40%.

If the mode-matching is perfect then we expect the visibility to be \text{VIS}=\frac{I_\text{max}-I_\text{min}}{I_\text{max}+I_\text{min}}=\frac{2\sqrt{I_\text{LO}I_\text{AS}}}{I_\text{LO}+I_\text{AS}}=\frac{2\sqrt{300\cdot 60}}{300+600}

which is roughly 74.5%.

If there is some mode-mismatch one can show that the visibility is \text{VIS}=\frac{2\sqrt{M}\sqrt{I_\text{LO}I_\text{AS}}}{I_\text{LO}+I_\text{AS}}, where M=\left|\frac{\int \left(E_\text{LO}^\star E_\text{AS} \right)\mathrm{d}x \mathrm{d}y}{\sqrt{I_\text{LO}I_\text{AS}}}\right|^2 is the mode-mismatch.

Using Finesse model I calculated \sqrt(M)=0.93 in the MICH configuration so the expected visibility is around 70%, far away from the observed 40%. To explain the observed visibility the mode mismatch would have to be ~ 30% which is very unlikely.

So it could either be a ghost beam or that the LO beam is clipped so badly that it also degrades its phase front (and therefore the mode-matching). The fact that we see fringes on the LO beam might suggest knife edge clipping on one of the auxiliary optics in the BS chamber.

  17146   Tue Sep 20 15:40:07 2022 yehonathanUpdateBHDTrying doing AC lock

We resume the LO phase locking work. MICH was locked with an offset of 80 cts. LO and AS beams were aligned to maximize the BHD readout visibility on ndscope.

We lock the LO phase on a fringe (DC locking) actuating on LO1.

Attachment 1 shows BHD readout (DCPD_A_ERR = DCPD_A - DCPD_B) spectrum with and without fringe locking while LO2 line at 318 Hz is on. It can be seen that without the fringe locking the dithering line is buried in the A-B noise floor. This is probably due to multiple fringing upconversion. We figured that trying to directly dither-lock the LO phase might be too tricky since we cannot resolve the dither line when the LO phase is unlocked.

We try to handoff the lock from the fringe lock to the AC lock in the following way: Since the AC error signal reads the derivative of the BHD readout it is the least sensitive to the LO phase when the LO phase is locked on a dark fringe, therefore we offset the LO to realize an AC error signal. LO phase offset is set to ~ 40 cts (peak-to-peak counts when LO phase is uncontrolled is ~ 400 cts).

We look at the "demodulated" signal of LO1 from which the fringe locking error signal is derived (0 Hz frequency modulation 0  amplitude) and the demodulated signal of LO2 where a ~ 700 Hz line is applied. We dither the LO phase at ~ 50Hz to create a clear signal in order to compare the two error signals. Although the 50 Hz signal was clearly seen on the fringe lock error signal it was completely unresolved in the LO2 demodulated signal no matter how hard we drove the 700Hz line and no matter what demodulation phase we chose. Interestingly, changing the demodulation phase shifted the noisy LO2 demodulated signal by some constant. Will post a picture later.

Could there be some problem with the modulation-demodulation model? We should check again but I'm almost certain we saw the 700Hz line with an SNR of ~ 100 in diaggui, even with the small LO offset changes in the 700Hz signal phase should have been clearly seen in the demodulated signal. Maybe we should also check that we see the 50Hz side-bands around the 700Hz line on diaggui to be sure.

Attachment 1: Screenshot_2022-09-20_15-38-44.png
Screenshot_2022-09-20_15-38-44.png
  14193   Wed Sep 5 10:59:23 2018 wgautamUpdateCDSCDS status update

Rolf came by today morning. For now, we've restarted the FE machine and the expansion chassis (note that the correct order in which to do this is: turn off computer--->turn off expansion chassis--->turn on expansion chassis--->turn on computer). The debugging measures Rolf suggested are (i) to replace the old generation ADC card in the expansion chassis which has a red indicator light always on and (ii) to replace the PCIe fiber (2010 make) running from the c1lsc front-end machine in 1X6 to the expansion chassis in 1Y3, as the manufacturer has suggested that pre-2012 versions of the fiber are prone to failure. We will do these opportunistically and see if there is any improvement in the situation.

Another tip from Rolf: if the c1lsc FE is responsive but the models have crashed, then doing sudo reboot by ssh-ing into c1lsc should suffice* (i.e. it shouldn't take down the models on the other vertex FEs, although if the FE is unresponsive and you hard reboot it, this may still be a problem). I'll modify I've modified the c1lsc reboot script accordingly.

* Seems like this can still lead to the other vertex FEs crashing, so I'm leaving the reboot script as is (so all vertex machines are softly rebooted when c1lsc models crash).

Quote:

c1lsc crashed again. I've contacted Rolf/JHanks for help since I'm out of ideas on what can be done to fix this problem.

  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.
  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
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Attachment 2: IMG_1481.jpg
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  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.
  20   Fri Oct 26 21:48:40 2007 waldmanConfigurationOMCFiber to 056
I set up a 700 mW NPRO in Rana's lab and launched it onto a 50m fiber. I got a few mW onto the fiber, enough to see with a card before disabling the laser. The fiber now runs along the hallway and terminates in rm 056. Its taped down everywhere someone might trip on it, but don't go out of your way to trip on it or pull on it because you are curious. Tomorrow I will co-run a BNC cable and attenuate the NPRO output so it can only send a few mW and so be laser safe. Then we can try to develop a procedure to align the beam to a suspended OMC and lock our suspended cavity goodness.

Notes to self: items needed from the 40m
  • ND10 and ND20 neutral density filter
  • EOM and mount set for 4 inch beam height
  • Post for fiber launch to get to 4 inch
  • Mode matching lens at 4in
  • 3x steering mirror at 4in
  • RF photodiode at 4in
  • Post for camera to 4in
  • Light sheild for camera
  • Long BNC cable
Some of these exist at 056 already
  21   Sat Oct 27 19:00:44 2007 waldmanConfigurationOMCHanging, locked OMC with REFL extracted.
I got the OMC locked to the fiber output today. It was much more difficult than I expected and I spent about 30 minutes or so flailing before stopping to think. The basic problem is that the initial alignment is a search in 4-dimensional space and there is naturally only one signal, the reflected DC level, to guide the alignment. I tried to eyeball the alignment using the IR card and "centering" the beams on mirrors, but I couldn't get close enough to get any light through. I also tried to put a camera on the high reflector transmission, but with 1.5 mW incident on the cavity, there is only 1.5 microwatts leaking through in the best case scenario, and much, much less during alignment.

I resolved the problem by placing a high reflector on a 3.5 inch tall fixed mount and picking off the OMC transmitted beam before it reaches the DC diodes. I took the pickoff beam to a camera. The alignment still sucked because even though the beam cleanly transmitted the output coupler, it wasn't anywhere close to getting through the OTAS. To resolve this problem, I visually looked through the back of M2 at M1 and used the IR card to align the beam to the centers of each mirror. That was close enough to get me fringes and align the camera. With the camera aligned, the rest was very easy.

I restored the PDH setup we know and love from the construction days and locked the laser to the OMC with no difficulty. The laser is in Rana's lab so I send the +/- 10V control signal from the SR560 down a cable to 058E where it goes into the Battery+resistor box, the Throlabs HV amplifier, and finally the FAST channel of the NPRO. BTW, a simple experiment sows that about 35 +/- 3 V are required to get an FSR out of the NPRO, hence the Thorlabs HV. The EOM, mixer, splitter, etc is on the edge of the table.

With this specific OMC alignment, ie. the particular sitting on EQ stops, it looks like all of the ghost beams have a good chance of coming clear. I can fit a 2 inch optic in a fixed mount in between the end of the breadboard and the leg of the support structure. A picture might or might not be included someday. One of the ghost beams craters directly into the EQ stop vertical member. The other ghost barely misses M2 on its way down the length of the board. In its current configuration, the many REFL beam misses the leg by about 1.5 inches.
  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.
ELOG V3.1.3-