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  40m Log, Page 109 of 339  Not logged in ELOG logo
ID Date Author Type Category Subjectup
  9713   Tue Mar 11 14:49:01 2014 KojiSummaryLSCImportant notice on the XARM servo

The nominal gain of the XARM for the POX11 error signal is 0.03 (instead of previous 0.3)

This is due to my increase of the gain in FM4 by 20dB so that we can turn of FM4 without changing the UGF when it is at 150Hz.

The YARM servo was not yet touched.

  8476   Tue Apr 23 15:02:19 2013 Max HortonUpdateSummary PagesImporting New Code

Duncan Macleod (original author of summary pages) has an updated version that I would like to import and work on.  The code and installation instructions are found below.

I am not sure where we want to host this.  I could put it in a new folder in /users/public_html/  on megatron, for example.  Duncan appears to have just included the summary page code in the pylal repository.  Should I reimport the whole repository?  I'm not sure if this will mess up other things on megatron that use pylal.  I am working on talking to Rana and Jamie to see what is best.

  8496   Fri Apr 26 15:50:48 2013 Max HortonUpdateSummary PagesImporting New Code


I am following the instructions here:


But there as an error when I run the ./00boot command near the beginning.  I have asked Duncan Macleod about this and am waiting to hear back.

For now, I am putting things into /home/controls on allegra.  My understanding is that this is not shared, so I don't have a chance of messing up anyone else's work.  I have been moving slow and being extra cautious about what I do because I don't want to accidentally nuke anything.

  8504   Mon Apr 29 15:35:31 2013 Max HortonUpdateSummary PagesImporting New Code


 I installed the new version of LAL on allegra.  I don't think it has interfered with the existing version, but if anyone has problems, let me know.  The old version on allegra was 6.9.1, but the new code uses  To use it, add . /opt/lscsoft/lal/etc/lal-user-ench.sh to the end of the .bashrc file (this is the simplest way, since it will automatically pull the new version).

I am having a little trouble getting some other unmet dependencies for the summary pages such as the new lalframe, etc.  But I am working on it.

Once I get it working on allegra and know that I can get it without messing up current versions of lal, I will do this again on megatron so I can test and edit the new version of the summary pages.

  8523   Thu May 2 14:14:10 2013 Max HortonUpdateSummary PagesImporting New Code


 LALFrame was successfully installed.  Allegra had unmet dependencies with some of the library tools.  I tried to install LALMetaIO, but there were unmet dependencies with other LSC software.  After updating the LSC software, the problem has persisted.  I will try some more, and ask Duncan if I'm not successful.

Installing these packages is rather time consuming, it would be nice if there was a way to do it all at once.

  8536   Tue May 7 15:09:38 2013 Max HortonUpdateSummary PagesImporting New Code


 I am now working on megatron, installing in /home/controls/lal.  I am having some unmet dependency issues that I have asked Duncan about.

  8572   Tue May 14 16:14:47 2013 Max HortonUpdateSummary PagesImporting New Code

I have figured out all the issues, and successfully installed the new versions of the LAL software.  I am now going to get the summary pages set up using the new code.

  8604   Tue May 21 14:50:52 2013 Max HortonUpdate Importing New Code

There was an issue with running the new summary pages, because laldetchar was not included (the website I used for instructions doesn't mention that it is needed for the summary pages).  I figured out how to include it with help from Duncan.  There appear to be other needed dependencies, though.  I have emailed Duncan to ask how these are imported into the code base.  I am making a list of all the packages / dependencies that I needed that weren't included on the website, so this will be easier if/when it has to be done again.

  8678   Wed Jun 5 14:39:41 2013 Max HortonUpdate Importing New Code

Most dependencies are met.  The next issue is that matplotlib.basemap is not installed, because it is not available for our version of python.  We need to update python on megatron to fix this.

  13891   Fri May 25 13:06:33 2018 Jon RichardsonConfigurationElectronicsImproved Measurements of AUX-PSL PLL

Attached are gain-variation measurements of the final, in situ AUX-to-PSL phase-locked loop (PLL).

Attachment 1: Figure of open-loop transfer function

Attachment 2: Raw network analyzer data

The figure shows the open-loop transfer function measured at several gain settings of the LB1005 PI servo controller. The shaded regions denote the 1-sigma sample variance inferred from 10 sweeps per gain setting. This analysis supercedes previous posts as it reflects the final loop architecture, which was slightly modified (now has a 90 dB low-frequency gain limit) as a workaround to make the LB1005 remotely operable. The measurements are also extended from 100 kHz to 1 MHz to resolve the PZT resonances of the AUX laser.


  • Gain variation confirms response linearity.
  • At least two PZT resonances above the UGF are not far below unity (150 kHz and 500 kHz).
  • Recommend to lower the proportional gain by 3 dB. This will place the UGF at 30 kHz with 55 degrees of phase.
Attachment 1: LB1005_OL_transfer.pdf
Attachment 2: data.tar.gz
  13294   Tue Sep 5 16:37:47 2017 GabrieleSummaryLSCImproved PRMI deep learning reconstruction

This is an update on the results already presented earlier (refer to elog 13274 for more introductory details). I improved significantly the results with the following tricks:

  • I retuned the demodulation phase of AS55, this time ensuring that the (alleged) MICH motion is visible mostly in Q when crossing a carrier resonance. Further fine tunings of phases will be possible once we have a measurement of the length optical matrix

  • I fine tuned the netwrok by training it again using the real data. The ides is the following. I started with the network trained on the simulated data, and froze the parameters of the input recurrent layers. I fed the real signal to the network, computed the reconstructed PRCL/MICH, and fed them to my PRMI model to compute simulated signals. I allowed some of the parameters of the models to vary (expecially demodulation phases). I then trained again the network by trying to match the model predicted signals with the real input signals. I allowed only the parameters of the fully connected layers to vary (mostly for technical reasons, I'm working on re-training also the recurrent layers)

An example of time domain reconstruction is visible below. It already looks better than the old results:

As before, to better evaluate the performance I plotted averaged values of the real signals as a function of the reconstructed MICH and PRCL positions. The results are compared with simulation below. They match quite well (left real data, right simualtion expectation)

One thing to better understand is that MICH seems to be somewhat compressed: most of the output values are between -100 and +100 nm, instead of the expected -lambda/4, lambda/4. The reason is still unclear to me. It might be a bug that I haven't been able to track down yet.

  11496   Wed Aug 12 01:32:18 2015 IgnacioUpdateIOOImproved SISO (T240-X) FF of MCL

In my previous elog:11492, I stated that in order to improve the subtraction and reduce the injection of high frequency noise we want the filter's magnitude to have a 1/f rolloff.

I implemented this scheme on the filter SISO filter previously analyzed. The results are shown below.

The filters bode plot:

The nice 1/f rollof is the main change here. Everything else remained pretty much the same.

The predicted FIR and IIR subtractions:

Everything looks right but that hump at 8 Hz. I used 8 pairs of poles/zeros to get this subtraction.

The online MCL subtraction:

This looks better than I expected. One has to keep in mind that I ran this at 1 AM. I wonder how well this filter will do during the noisier hours of the day. The RMS at high frequencies doesn't look great, there will definitely be noise being injected into the YARM signal at high frequencies.

Measuring the YARM signal:

There is still noise being injected on YARM but it is definitely much better than the previous filter. I'm thinking about doing some IIR subtraction on the arms now to see if I can get rid of the noise that is being injected that way, but before I embark on that quest I will rething my prefiltering.

The plot below shows the ratio of the unfiltered versus filtered ASDs for the FIR and IIR subtraction predictions as well as for the measured online IIR subtraction. Positive dB means better subtraction.

Attachment 1: filter.png
Attachment 2: stsx.png
Attachment 3: mclonline.png
Attachment 4: yarmonline.png
Attachment 5: sub.png
  6850   Thu Jun 21 20:07:18 2012 JamieUpdateGreen LockingImproved beatbox returns

I've reinstalled the beatbox in the 1X2 rack.  This improved version has the X and Y arm channels stuffed, but just one of the DFD channels (fine) each.

I hooked up the beat PD signals for X and Y to the RF inputs, and used the following two delay lines:

  • X: 140' light-colored cable on spool
  • Y: 30m black cable

The following channel --> c1ioo ADC --> c1gcv model connections were made:

  • X I  --> SR560 whitening --> ADC 22 -->  X fine I
  • X Q --> SR560 whitening --> ADC 23 --> X fine Q
  • Y I --> SR560 whitening --> ADC 24 --> Y fine I
  • Y Q --> SR560 whitening --> ADC 25 --> Y fine Q

The connections to the course inputs on the ALS block were grounded.  I then recompiled, reinstalled, and restarted c1gcv.  Functioning fine so far.


  1590   Fri May 15 16:47:44 2009 josephbUpdateCamerasImproved camera code

At Rob's request I've added the following features to the camera code.

The camera server, which can be started on Ottavia by just typing pserv1 (for camera 1) or pserv2 (for camera 2), now has the ability to save individual jpeg snap shots, as well as taking a jpeg image every X seconds, as defined by the user.

The first text box is for the file name (i.e. ./default.jpg will save the file to the local directory and call it default.jpg).  If the camera is running (i.e. you've pressed start), prsessing "Take Snapshot to" will take an image immediately and save it.  If the camera is not running, it will take an image as soon as you do start it.

If you press "Start image capture every X seconds", it will do exactly that.  The file name is the same as for the first button, but it appends a time stamp to the end of the file.

There is also a viedo recording client now.  This is access by typing "pcam1-mov" or "pcam2-mov".  The text box is for setting the file name.  It is currently using the open source Theora encoder and Ogg format (.ogm).  Totem is capable of reading this format (and I also believe vlc).  This can be run on any of the Linux machines.

The viewing client is still accessed by "pcam1" or "pcam2".

I'll try rolling out these updates to the sites on Monday.

The configuration files for camera 1 and camera 2 can be found by typing in camera (which is aliased to cd /cvs/cds/caltech/apps/linux64/python/pcamera) and are called pcam1.ini, pcam2.ini, etc.


  4226   Sat Jan 29 03:13:44 2011 ranaUpdateWienerFilteringImprovement in H1 Wiener FF prediction by using weights and taps

(Jenne, Rana)

Tonight we noticed that there were significant improvements to be had in the predicted DARM Wiener filtering FF performance by using weighting filters and more taps in the FIR filter.

The plots below tell the story:

The first one shows the improvement in the residual (black & blue) by applying a weighting filter. The weight filter tilts the spectrum up at HF and applies and all real pole BP from 10-20 Hz.

The second plot shows the improvement gotten by using 3000 instead of 2000 taps for the Wiener filter. With the larger number of taps we not only get the big improvement at LF, but also some beefy reduction in the higher frequency stack modes and the LOS roll mode.

I'm not sure why we haven't run across this before; the weighting filter was arrived at today by just iterating by hand on the placement of poles and zeros until the trace looked nice.

Jenne is going to run this new filter on the S5-month that we have been using for stationarity testing.

* Some notes:

** this Wiener stuff is faster, by far, on rossa than either megatron or rosalba or my laptop. More than a factor of 3.

*** there is a bug with Macports/Matlab - if you get fftw3 with Macports, it sets itself as the right version to use. This confuses matlab in some cases.

     if you get the error about libfftw3.dylib, whe trying fft in matlab after installing macports, then you can fix it by setting the Matlab lib/ path with the fftw libraries to be ahead of /opt/local/lib in the LD_LIBRARY_PATH in your .cshrc.

Attachment 1: darmweight.png
Attachment 2: darm3000.png
  4231   Mon Jan 31 10:31:30 2011 josephbUpdateWienerFilteringImprovement in H1 Wiener FF prediction by using weights and taps

Rossa is a rather beefy machine. It effectively has 8 Intel i7 Cores (2.67 Ghz each) and 12 Gigs of ram.  Megatron only has 8 Gigs of ram and just 8 Opterons (1 GHz each).  Rosalba has 4 Quad Core2  (2.4 GHz) with only 4 Gigs of ram. 

MC damp dataviewer diaggui AWG c1ioo c1sus c1iscex RFM The Dolphins Sim.Plant Frame builder TDS
  289   Thu Jan 31 16:53:41 2008 josephbConfigurationCamerasImproving camera user interface
There's a new and improved version of Snap program at the moment people are free to play with.

Located in /cvs/cds/caltech/target/Prosilica/40mCode/

The program Snap now has a -h or --help option which describes some basic command line arguments. The height (in pixels), width (in pixels), exposure time (in micro seconds), file name to be saved to (in .tiff format), and packet size can all be set. The format type (i.e. pixel format such as Mono8 or Mono16) doesn't work at the moment.

At the moment, it only runs on mafalda.

Currently in the process of adding a loop option which will take images every X seconds, saving them to a given file name and then appending the time of capture to the file name.

After that need to add the ability to identify and choose the camera you want (as opposed to the first one it finds).

Lastly, I've been finding on occassion that the frame fails to save. However if you try again a few seconds later with the exact same parameters, it generally does save the second time. Not sure whats causing this, whether on the camera or network side of things.

I've attached two images, the first at default exposure time (15,000 microseconds) and the second at 1/5th that time (3,000 microseconds).
The command line used was "./Snap -E 3000 -F 'Camera_exp_3000.tiff' "
Attachment 1: Camera_exp_15000.tiff
Attachment 2: Camera_exp_3000.tiff
  7390   Fri Sep 14 18:18:33 2012 JenneUpdateGeneralIn Vac Pictures


After much fussing, we got a picture of MMT1 with the beam.

Using the iris doesn't seem feasible. Since it has to be significantly separated from the optic, it is hard to judge whether it is centered, especially in yaw.

It took ~30 min to get this picture. Comments on whether this kind of picture is good enough are welcomed, since there are many more to be taken.

 I've been taking more photos.  Obviously, it gets quicker as I go along and get the hang of it.  Also, I've been taking overhead pictures with the Nikon so we can see what kind of parallax there is for each snapshot.

However, I just took MMT2, and the beam is nearly falling off the side of the optic!  It seemed fine last night when Rana and I were working on it.  The MC spots haven't moved significantly (I had measured yesterday, and again a few hours ago).  WTF?

This means that I need to move the knobs of MMT1, and then redo the whole alignment chain all over again.  Lame.


EDIT:  MC spot positions, last night at 12:33am, and this afternoon at 2:12pm:

                        year month day hour minute       MC1pit         MC2pit          MC3pit            MC1yaw         MC2yaw          MC3yaw

./data_spotMeasurements/MCdecenter201209140033.dat      1.749759        9.744013        1.025681        -0.791683       -1.338786       -1.779958      
./data_spotMeasurements/MCdecenter201209141412.dat      1.702974        7.916438        0.986519        -0.888736       -0.170237       -1.771267


Attachment 1: mmt2.jpg
  7391   Fri Sep 14 18:28:25 2012 JenneUpdateGeneralIn Vac Pictures

All the photos so far:











  14614   Thu May 16 22:58:25 2019 gautamUpdateASSIn air ASS test with green?

We were wondering yesterday if we can somehow test the ASS system in air. Though the arm cavity can be locked with the low power IMC transmission, I think the dither would render the POY lock unstable. But I wonder if we can use the green beam for a test. The steering PZTs installed by Yuki can serve the role of TT1/TT2 and we can dither the arm cavity mirrors while the green TEM00 mode is locked to the arm no problem. This would at least give us confidence that the actuation of ETMY/ITMY are okay (in addition to the other suspension tests). Then on the sensing side, after pumping down, the only thing we'd be foiled by is in-vacuum clipping or some major gunk on ETMY - everything else should be de-buggable even after pumping down?

I think most of the CDS infrastructure for this is already in place.

  12353   Fri Jul 29 03:59:55 2016 ericqUpdateSUSIn air OSEM diagonalization check

The question arose whether we can get good enough data to diagonize our OSEM sensing matrices in air. 

I just took a look at the BS spectra over the last six hours (~10PM-4AM), and the SNR looks good. The BS diagonalization itself doesn't seem so great; the POS is hugely coupled into pitch and yaw, and the angular motions are themselves coupled to each other at around 10%. 

NB: use a flat-top window when you really care about peak heights that don't fall exactly on an FFT bin. 

I would've liked to check this for the PRM and SRM too, but one of the PRM sensors continues to be dark, and I just noticed that all of the SRM OSEM signals are dark. ughhhh

Attachment 1: BS_OSEM_diag.pdf
  460   Tue Apr 29 21:30:49 2008 AndreyUpdatePEMIn the process of renaming channels for Weather Station

I startted renaming channels for the weather station, and I will continue this tomorrow, on Wednesday.

I have restarted 'c1pem1' several times and reconfigured "C0DCU1" on the framebuilder MEDM screen.

Framebuilder now does not work.
  7314   Thu Aug 30 00:08:34 2012 jamieUpdateGeneralIn vac plans for tomorrow, 8/30


We need to check spot centering on PRM with camera tomorrow.

Suresh checked that we're not clipped by IP ANG/POS pickoff mirrors, but we haven't done any alignment of IP ANG/POS.

 I think we should NOT do any adjustment of IP ANG/POS now.  We should in fact try to recover them when doing the PRM spot centering


Tomorrow:  Open ITMX door.  Check with Watek that we're hitting center of PRM.  Then look to see if we're hitting center of PR2.  Then, continue through the chain of optics.

The motivation for removing the ITMX door was so that the scatter measurement team could check alignment of the new viewing mirror next to ETMX.  After discussion today we decided that everything can be done at the X end.  They can inject a probe beam into the ETMX chamber, bounce it off of ITMX and align the viewing mirror with the reflection.  So we'll leave ITMX door on for now.

We should, however, inspect the situation ITMY and make sure we have good clearance in the Y arm part of the Michaelson.  Koji previously expressed suspicion that we might have clipping on the southern edge of the POY steering mirror, so we need to check that out.

Koji and I discussed the situation for getting camera face views of BS and PRM.  Koji said the original idea was to see if we could install something at the south-east view port of ITMX chamber.  Steve also suggested utilizing the "ceiling" camera mounted on the top of the IOO chamber.

Vertex tasks:

  • check spot centering in PRM
  • check that REFL is getting cleanly to the AP table
  • check IPPOS and IPANG - we should be adjusting IPPOS or IPANG at this point
  • check spot centering on BS
  • remove ITMY north door
  • check clearance of POY steering mirror
  • ...

in parallel:

  • Steve will inspect the situation for getting a camera view of BS and PRM face, either through IOO or ITMX.

End X tasks:

  • install baffle
  • install "permanent" ITMX viewing mirror, on west side of ETMX - this might require moving ETMX SUS cable bracket south
  • install temporary steering mirror for probe laser on south-east side of ETMX
  • at some point the scatter guys can also do transmission measurements of the ETMX view ports
  • ...
  7315   Thu Aug 30 08:12:39 2012 SteveUpdateGeneralIn vac plans for tomorrow, 8/30


 1,PRM spot can be viewed directly from the window south-east of ITMX chamber.  I can easy set up the mobile- Watek for this reason or you can just use an IR viewer.

   Remember, we have 2 SOS centering targets ready to use , that Rana was suggesting.

2, PR2 spot centering can be viewed directly through window north-west of ITMX.

3, We should put back the BS view pick-up mirror for the vertical camera on the BS chamber and adjust its upper pick-up.

4, The BS centering can be viewed with the mobile-Watek placed inside the BS chamber immediately.

  14069   Fri Jul 13 20:36:33 2018 KojiSummaryGeneralIn vac/In air heater wiring

I went to the Y-end and took more photos of the cable stand. These revealed that in-vac pin #13 is connected to the shield of the cable (P.2). This in-vac pin #13 corresponds to  in-air pin #1. So in the end, we bunch the pins in the following order.

In Air In Vac
Pin #2-7 Pin #12-7
Pin #8-13 Pin #6-1
Pin #14-19 Pin #25-20
Pin #20-25 Pin #19-14


Attachment 1: heater_wiring.pdf
heater_wiring.pdf heater_wiring.pdf heater_wiring.pdf
  846   Mon Aug 18 11:50:29 2008 YoichiUpdateSUSIn vacuum free swinging results
The first attachment is the results of the free swinging spectra measurement performed in vacuum this morning.
They are freely swinging, but the suspensions in the BS chamber got even more extra peaks.
Especially, the SRM spectrum looks like a forest.
If those extra peaks are inter-modulations of the primary suspension modes, the heights of them should be
enhanced (compared to the in-the-air case) by the increased quality factors of the primary modes (due to the less air friction).
This might explain the observed increase in the extra peaks.

While doing the free swinging, we had two big spikes in the OSEM signals of the ETMs and only in ETMs.
Those spikes screwed up the spectra of the ETMs. So the ETM spectra were calculated using the time series
after the spikes.
The second attachment shows one of those spikes. It looks like a computer glitch.
Attachment 1: 2008-8-18.pdf
2008-8-18.pdf 2008-8-18.pdf 2008-8-18.pdf 2008-8-18.pdf 2008-8-18.pdf 2008-8-18.pdf 2008-8-18.pdf 2008-8-18.pdf
Attachment 2: spike.pdf
  9608   Thu Feb 6 16:41:31 2014 ericqUpdateGeneralIn-Vac Alignment

[Manasa, ericq]

Both arms have been aligned via ASS. PRC locked on carrier.

SB locking hasn't happened yet...


  • Aligned MC at low power, measured spots
  • Found ITMX AS, REFL spots on cameras. Couldn't find ITMY spot. Found x-arm flashes with PRM aligned.
  • MC Refl Y1 mirror was replaced with the 90:10 BS; blocked WFS path until MC was aligned
  • PMC power was increased (~1.4W directly before PSL shutter)
  • Touched up MC alignment, reactivated high power autolocker, measured spots.
  • Locked x-arm on IR, ran ASS
  • Found ITMY spot on AS camera, locked y-arm, ran ASS on both arms
  • Checked green beams. Y-arm locks at around .6, X-arm at around .2 (input steering needs adjustment)
  • Centered beams on WFS, reset filter bank offsets, turned on WFS
  • Aligned PRM, locked PRC on carrier.
  • Tried locking PRC on sideband, had troubles. Looks like there is some increased seismic activity; might be the culprit.


  9609   Fri Feb 7 12:43:12 2014 ericqUpdateGeneralIn-Vac Alignment


PRC Locked on Sidebands

Jenne reminded me that if we change a cavity, phases can change... So, first, I locked the PRC on the carrier, and then gave it MICH and PRCL excitations to optimize the AS55 and REFL55 phase rotation angles by looking at the excitation demodulated outputs of the unused quadrature (i.e. we want all of MICH to be in AS55 Q, so I rotated the phase until C1:CAL-SENSMAT_MICH_AS55_I_I_OUTPUT was zero on average).

This resulted in:

  • AS55: 7 -> -5.5
  • REFL55: 73 -> 86.9

I then used the same settings as in ELOG 9554, except I used -1s instead of +1s for the POP110I trigger matrix elements. (I'm not sure why this is different, but I noticed that the PRC would lock on carrier with positive entries here, so I figured we wanted the peaks with opposite sign).

So far, it seems more stable than when we were doing the demodulation phase measurements, it's been locked for >15 minutes without me having to tweak the gains or the alignment from the carrier locked case.

  9610   Fri Feb 7 13:00:52 2014 JenneUpdateGeneralIn-Vac Alignment


I then used the same settings as in ELOG 9554, except I used -1s instead of +1s for the POP110I trigger matrix elements. (I'm not sure why this is different, but I noticed that the PRC would lock on carrier with positive entries here, so I figured we wanted the peaks with opposite sign).

 Nice work!!  As with all the other RF PDs, POP110's phase likely needs tuning.  You want POP110 (and POP22) I-quadratures to be maximally positive when you're locked on sidebands, and maximally negative when locked on carrier.  What you can do to get close is lock PRC on carrier, then rotate the POP phases until you get maximally negative numbers.  Then, when locked on sideband, you can tweak the phases a little, if need be.

  9611   Fri Feb 7 13:30:22 2014 GabrieleUpdateGeneralIn-Vac Alignment



I then used the same settings as in ELOG 9554, except I used -1s instead of +1s for the POP110I trigger matrix elements. (I'm not sure why this is different, but I noticed that the PRC would lock on carrier with positive entries here, so I figured we wanted the peaks with opposite sign).

 Nice work!!  As with all the other RF PDs, POP110's phase likely needs tuning.  You want POP110 (and POP22) I-quadratures to be maximally positive when you're locked on sidebands, and maximally negative when locked on carrier.  What you can do to get close is lock PRC on carrier, then rotate the POP phases until you get maximally negative numbers.  Then, when locked on sideband, you can tweak the phases a little, if need be.

 Very good news! We should have a look at the POP110 sideband peak splitting, to see if we really got the right PRC length... 

  9612   Fri Feb 7 13:30:25 2014 ericqUpdateGeneralIn-Vac Alignment



 Nice work!!  As with all the other RF PDs, POP110's phase likely needs tuning.  You want POP110 (and POP22) I-quadratures to be maximally positive when you're locked on sidebands, and maximally negative when locked on carrier.  What you can do to get close is lock PRC on carrier, then rotate the POP phases until you get maximally negative numbers.  Then, when locked on sideband, you can tweak the phases a little, if need be.

Adjusted the angles as Jenne suggested:

  • POP22: 105 -> 163
  • POP110: 150 -> -83
  15464   Thu Jul 9 17:12:52 2020 gautamUpdateBHDIn-air BHD


We can probably learn something about the interferometer / top level BHD plan with an in-air BHD setup, even if the noise is bad. Here are some thoughts about how we would do it. 

LO delivery:

For this first attempt, we don't really care about the PRC filtering. So possible places to pick off an LO beam are:

LO beam pickoff options
Location Pros Cons
  • Filtered by IMC
  • Medium level of invasiveness  
  • We lose the IP POS diagnostic, which is kind of useful nowadays given the drifty TTs.
  • Only few mW LO power available
PSL table IR beam currently going to green doubling setup
  • Least invasive w.r.t. normal IFO operation
  • Plenty of light (~100 mW) available. But how much can we safely couple into fiber?
  • Beam not filtered by IMC (although it is filtered by the PMC)
  • Since this beam is extracted from inside the PRC, probably enjoys the best filtering.
  • Possibly drifts a lot, so tricky to reliably couple into a fiber?
  • Maximally invasive w.r.t. regular IFO operations.

In all cases, I think the easiest option to actually route whatever beam we choose into a fiber, and then bring it over to whatever cavity we choose to use for an OMC. I'm assuming whatever phase control technique we end up using can cancel the fiber phase noise at relevant frequencies.

LO phase control

  • Stress the fiber? This will require us to purchase some custom hardware, and interface it to the CDS system.
  • PZT mirror? We should have sufficient hardware available to drive a PI style PZT mirror.

There is a question about the range, but I think these are the only two realistic options we can implement on a reasonable time scale.


Again, there are a few options. Here are some pros and cons that come to my mind.

OMC cavity options
Option Pros Cons
Old copper OMC
  • Probably the simplest option in terms of the peripherals.
  • PZT driver recently verified to work
  • We can get the OMMT and DCPDs out as well.
  • Allows us to not compromise on the RF darm optical gain (not sure if locking will be as easy if we cut the power to the AS55 photodiode by 50-75%).
  • Requires a vent.
  • Probably not the most efficient use of the space on the AP table.
  • Filtering performance isn't quantified.
Spare PMC
  • Doesn't require a vent.
  • Compact footprint.
  • Need to build the cavity.
  • Need to check if the drive electronics from the old copper OMC can easily be interfaced with whatever PZT we use on this cavity.
  • Filtering performance kind of unknown?
Custom cavity with spare mirrors
  • Doesn't require a vent.
  • Probably no more difficult than the spare PMC option?
  • We need at least one actuatable mirror, so we'd need some PZT mounted optic + associated drive electronics.

If we can do a vent (we'd just need a single chamber open), I'd go for the option of getting the copper OMC out and using that. Attachment #1 shows the approximate sizes of the various components (OMMT, OMC cavity, DCPDs), while Attachment #2 shows a rough sketch of where things would go on the AP table, with the rectangles approximately to scale.


I'd made a c1omc model sometime ago. Basically, I think we have sufficient ADC/DAC channels in the c1ioo machine for any of the options listed above - but using the copper OMC and associated peripherals would allow the easiest interfacing.

Criticisms/comments/thoughts please.

Attachment 1: OMCchamber.pdf
Attachment 2: AP_Table_20180328.pdf
  15493   Sun Jul 19 15:40:15 2020 gautamUpdateBHDIn-air BHD - CDS and wiring summary

Attachment #1 shows the proposed wiring and CDS topology for the in air BHD setup. The PDF document has hyperlinks you can follow to the DCC entries. Main points:

  1. I think we should run the realtime model on c1lsc. This will negate the need for any IPC between c1ioo and c1lsc machines.
  2. I think we have most of the electronics we need already, though I am still in the process of testing the various boards, especially the HV ones.
  3. We may choose to use the switchable whitening feature for the M2 ISS board
    • This would require some BIO channels
    • There are plenty spare in c1lsc, so it's not going to be a show stopper
    • This is why I've not explicitly included a whitening board for now...
  4. The main job seems to be to make a whole bunch of custom cables. For the most part, I think we have the long (~20m) long D9 cables, so I propose just snipping off the connector at one end, and soldering on the appropriate connectors to the correct conductors.
  5. For the homodyne phase control - the proposal is to use a PI PZT with 3 piezoelectric elements. We would drive the 3 elements with the same voltage, by shorting the conductors together (at least that's how I understood Koji's comment), so we'd only need a single DAC channel for this purpose.
    • Need to confirm that the parallel PZT capacitances (each element is ~300 nF so 3 in parallel would be ~900 nF) still allows sufficient actuation bandwidth.
    • If the relative actuation strength of the 3 elements needs to be individually tuned, we may have to use three DAC channels. The D980323 board will allow the driving of 3 independent channels. I have one of these boards in hand, but need to check if it works, and also implement the changes outlined here.
  6. The alignment control has not yet been accounted for
    • We could consider using the in-vacuum PZTs, these were verified to be working ~2018.
    • If we use only 1 steering PZT mirror, we have sufficient free DAC channels available in c1lsc. But if we need both (to avoid clipping for example), then we need more DAC channels - we can either free up one DAFI channel, or install a DAC in the c1lsc expansion chassis
  7. We may want to expand to have a second OMC at some point. In which case we'd need, at the very least
    • 1 more DAC card
    • A HV driver for the second OMC length (could use the Trek driver if we use D980323 for the homodyne phase control).

Please comment if I've overlooked something.

Attachment 1: wiringDiagram.pdf
  15505   Wed Jul 29 11:57:59 2020 ranaUpdateBHDIn-air BHD - CDS and wiring summary

3. I agree - this whitening will be handy to have for diagnostics.

4. I think in principle, we can ask a company to make the custom cables for us to save us some hand labor. Rich/Chub probably know the right companies to do small numbers of dirty cables.

5. Can't we just a single Noliac PZT in the same way that the OMC does? Or is the lead time too long?

6. Do we need active steering for this in-air test? I'm not even sure how we would get the alignment signal, so maybe that's a good reason to figure this out.

  15479   Tue Jul 14 15:29:25 2020 gautamUpdateBHDIn-air BHD - DCPD amplifier noise

For the first pass, it's probably easiest to use the existing DCPD amplifier. Looking at the gain and noise performance in Attachment #1, seems totally fine, the electronics noise will not be limiting if we have ~10mW of LO power. I assumed a transimpedance resistor of 1 kohm, and all other numbers as on the schematic (though who knows if the schematic is accurate). The noise should be measured to confirm that the box is performing as expected...

Attachment 1: DCPDamp.pdf
  15497   Tue Jul 21 00:30:24 2020 gautamUpdateBHDIn-air BHD - LO RIN

Attachment #1 shows the RIN of the local oscillator beam delivered to the AP table via fiber. I used a PDA520 to make this measurement, while the electronics for the DCPDs are pending. I don't really have an explanation for the difference between the locked IFO trace vs the not locked trace - we don't have an ISS running (but this first test suggests we should) and the beam is picked off before any cavities etc, so this is a reflection of the state of the FSS servo at the times of measurement?

Tried locking CARM using the hybrid REFL (for AO path) and POX 11 (for MCL path) scheme a bunch of times today, but I had no luck. When the CARM offset is zeroed, the PRMI lock is lost almost immediately. Maybe this is indicative of some excess noise in the POX data stream relative to the REFL signal? The one thing I haven't tried is to take the IFO all the way to the locked state, and then transition the MCL actuation from CM_SLOW to POX11_I.

An SR785 is sitting on the North side of the AP table in the walkway - I will clear it tomorrow.

Attachment 1: LO_RIN.pdf
  15483   Wed Jul 15 19:11:40 2020 gautamUpdateBHDIn-air BHD - alignment into OMC

I forgot about the pointing - probably we will need another actuator to control the pointing of the AS beam onto the DCPDs. I found a few old PI PZTs (model number is S-320, which is a retired part), one is labelled broken but the others don't indicate a-priori that they are broken. I'll post a more detailed hardware survey later.

  Draft   Wed Jul 15 19:17:09 2020 gautamUpdateBHDIn-air BHD - alignment into OMC

You can activate all 3axis


  15489   Thu Jul 16 01:12:22 2020 gautamUpdateBHDIn-air BHD - preparing the LO path

Attachment #1 - The 80mW pickoff was getting clipped on a BNC cable, and not making it to the doubling oven. 😢 .

  • Since the PSL doubled beam isn't used for locking these days, I just didn't notice.
  • I blame the ringdown team, this crazy tee arrangement wasn't the case before.
  • I fixed the situation by changing the cabling such that the beam clears the cables comfortably.

Attachment #2 - PSL green shutter removed. Alignment into the doubling oven is extremely tedious, and so I opted to preserve the capability of recovering the green beam by simply removing a single mirror.

Attachment #3 - The beam path for coupling the LO beam into a fiber.

  • Primary goal was to have easy access to some steering mirrors so that I can optimize alignment into the fiber collimator.
  • I opted to use the NW corner of the PSL table - that's where most of our existing fiber hardware is anyways, and there was sufficient space and easy access over there.
  • 3 Y1 mirrors were installed, using the preferred Polaris mounts and 3/4" post + baseplate hardware. They were labelled Y1-1037-45P so that future workers need not be un-necessarily tortured. The third mirror is not visible in this photograph.
  • Once the collimator arrives, I will mode match this beam into the fiber. Plan is to use the fiber originally used for the mode spectroscopy project. It needs to be moved to the NW corner of the PSL table, and the other end needs to be routed to the AP table (it was brought back to the PSL table to facilitate Anjali's fiber MZ experiment). 
  • There is plenty of space in the beam path for mode-matching lens(es) and polarization control optics.

Attachment #4 shows the BHD photodiodes taken from QIL. 

  • Unfortunately, we could not find the readout electronics. 
  • In the worst case, we can just interface these PDs with the existing Satellite box (associated with the copper OMC).
  • It might be that the OMC cavity can simply be placed on this breadboard, making the whole setup nice and portable.
  • We may want to consider having an OFI between the OMC and the IFO AS beam at some point...
Attachment 1: IMG_8626.JPG
Attachment 2: IMG_8627.JPG
Attachment 3: IMG_8628.JPG
Attachment 4: IMG_8629.JPG
  15495   Mon Jul 20 17:55:15 2020 gautamUpdateBHDIn-air BHD - preparing the LO path

The LO pickoff has been coupled into a fiber with ~90% MM (8 mW / 9 mW input). While I wait for the DCPD electronics to be found in the Cryo lab, I want to monitor the stability of the pointing, polarization etc, so I'd like to clear some space on the AP table that was occupied for the mode spectroscopy project. If there are no objections before 2pm tomorrow July 21 2020, I will commence this work.

  16530   Tue Dec 21 16:52:39 2021 AnchalSummaryElectronicsIn-air Sat Amp to Vacuum Flange cables laid for 7 new SOS

[Anchal, Yehonathan, Chub]

We today laid down 14 70 ft long DB25 cables from 1Y1 (6), 1Y0 (8) to ITMY Chamber (4), BS Chamber (6) and ITMX Chamber (4). The cables have been connected to respective satellite amplifier on the racks and the other ends are connected to the vacuum flange feedthru on ITMX for LO1 and PR2, while the others have been kept near the planned flange postions. LO1 is now ready to be connected to CDS by connecting the in-vacuum cable inside ITMX chamber to the OSEMs.

  7877   Mon Jan 7 00:08:16 2013 JenneHowToAlignmentIn-vac plan

List of things to do, in order:

* Remove BS heavy door.  Steve, please remove the BS door as soon as you have enough people to do so.  I will be a little late, since I have a dentist appointment, but please don't wait for me.  Jamie and Manasa can help you.  Put on a light door.

* Remove MC light doors, make aluminum foil tube (not light access connector, yet).

* Open laser shutter, lock PMC. (Required slight tweaking of input steering.) Confirm power level into vacuum <100mW.

* Lock MC and check spot positions of MC (quickly.  this shouldn't take all day, hopefully).

-------------------------------  End of work for Monday.  See following elog ------------------------------------------------


* Move TT1 to be as close as possible to the location indicated on the diagram, then align it. 

         * Make sure beam out of Faraday is hitting the center of the optic.

         * Make sure beam reflected off of TT1 hits center of PZT2.  Only use actuators for the final alignment, then confirm that they aren't close to the edge of their ranges.

         * Lock down TT1 with dog clamps.

* Put light access connector on MC.

* Swap PZT2 out with TT2.  Should be at correct spot, according to diagram, and beam should be hitting center of optic.  Alignment only to the ~few degree point here.

* Re-level BS table.

* Fix oplevs that need fixing.  (Manasa should have the plan on one of the diagrams).

* Put target on PRM cage.

* Align TT2 so that beam goes through PRM target.

* Open ITMX heavy door. (Probably Tuesday morning).

* Place freestanding target in front of PR2.  Ensure TT2 is aligned to go through PRM target, and hit center of PR2.  Again, save actuators for fine-tuning.

At this point, I think we should (temporarily) install one of the G&H mirrors as a flat mirror facing the PRM, and see if we can lock that cavity using REFL.  We will want to have already created a model for this case, to compare our observations to.  Or we could align the full PRMI, and try to lock that in air.



  16891   Mon Jun 6 09:37:16 2022 JCUpdateSUSInMatCalc

[Paco, JC]

Paco and I attempted to calculate the input matrices from May 24, 2022, but the OSEM data was all saturated and not very useful. Therefore, we decided to manually investigate the appropriate coil offsets for all BHD SUS. Before, the default offset kick was 30000 counts, but we found that LO1, AS1, AS4, and PR2 cannot take more than 5000 counts. As for LO2, SR2, and PR3 cannot take more than 2000 counts before saturating. Note that all these kick test were taken by kicking OSEM UL on all BHD Optics.


We started the freeSwing.py script on tmux freeSwing session for tomorrow at 1:00 am for only the 5000 count offset SUS.


  5924   Thu Nov 17 11:51:14 2011 JenneUpdateEnvironmentIncandescent vs. fluorescent lights?

I'm just on an elog roll this morning...

Again while poking around inside the IFO room, I noticed that they have replaced all of our incandescent lights with CFLs.  Do we care?  The point of having the incandescent lights on a separate switch from the big fluorescent lights was so that we could have only 60Hz lines, not wide-band noise if we want the lights on while locking. 

I'm not sure that we actually care, because more often we just turn off all the lights while trying to do serious locking, but if we do care, then someone needs to ask the custodial staff (or someone else?) to undo the change.

  5695   Wed Oct 19 12:06:26 2011 MirkoUpdateCDSIncluded the MC servo channel in CDS

[Jamie, Mirko]

Included the 'Servo' output from the D040180 in c1ioo, which I hoped would be a better measure of the MC length fluctuations. It goes into ADC6, labeled CH7 on the physical board.
Servo-output => C1:IOO-MC_SERVO. (Already present is Out1-output => C1:IOO-MC_F).
At low freq. the servo signal is about 4.5dB bigger. Both are recorded at 256Hz now which is the reason for the downward slope at about 100Hz.



  3322   Thu Jul 29 17:11:16 2010 GopalUpdateCOMSOL TipsIncluding Gravity in COMSOL

[Gopal, Jan]

For the past couple of days, Jan and I have been discussing a major issue in COMSOL involving modeling both oscillatory and non-oscillatory forces simultaneously while using FDA. It turns out that he and I had run into the same problem at different times and with different projects. After discussing with an expert, Jan had decided in the past that this simple task was impossible via direct means.

The issue could still be resolved if there was a way for us to work on the Weak Form of the differential equations describing the system:

  • Usually, one must define weight as a body load in the negative-z direction. However, this problematically instantiates a new force in COMSOL, which is automatically driven over the range of frequencies during FDA.
  • Instead, we could define gravity as an anti-restoring force, since we assume that the base of the stack is fixed.
  • In other words, Fg = (ρ*g/L)*x + (ρ*g/L)*y for a point mass which is constrained on the bottom (for small angles).
  • Working in Weak Form then, we'd never have to define an explicit gravity load-- this could just be an extra couple of terms in the differential equation which are related entirely to the x- and y-vectors (well-defined for each mesh point). This would fool COMSOL into never tacking on the oscillatory term during FDA. 

According to current documentation however, Weak Form analysis is not yet possible in COMSOL 4.0. Jan suggested moving my work over to ANSYS or waiting for the 4.0 upgrade, but there's probably not enough time left in my SURF for either of these options. I suggested attempting a backwards-compatibility test to COMSOL 3.5; Jan and I will be exploring this option some time next week. 

  10634   Thu Oct 23 02:08:40 2014 JenneUpdateLSCIncreased DARM gain

I changed the carm_cm_up.sh script so that it requires fewer human interventions.  Rather than stopping and asking for things like "Press enter to confirm PRMI is locked", it checks for itself.  The sequence that we have in the up script works very reliably, so we don't need to babysit the first several steps anymore. 

Another innovation tonight that Q helped put in was servoing the CARM offset to get a certain arm power.  A failing of the script had been that depending on what the arm power was during transition over to sqrtInvTrans, the arm power was always different even if the digital offset value was the same.  So, now the script will servo (slowly!!) the offset such that the arm power goes to a preset value.

The biggest real IFO progress tonight was that I was able to actually measure the CARM and DARM loops (thanks ChrisW!), and so I discovered that even though we are using (TRX-TRY)/(TRX+TRY) for our IR DARM error signal, we needed to increase the digital gain for DARM as the CARM offset was reduced.  For ALS lock and DC trans diff up to arm powers of 3, we use the same ol' gain of 6.  However, between 3 - 6, we need a gain of 7.  Then, when we go to arm powers above 6 we need a gain of 7.5.  I was also measuring the CARM loop at each of these arm powers (4, 6, 7, 8, 9), but the gain of 4 that we use for sqrtInvTrans was still fine. 

So, the carm_cm_up script will do everything that it used to without any help (unless it fails to find IR resonance for ALS, or can't lock the PRMI, in which case it will ask for help), and then once it gets to these servo lines to slowly increase the arm power and increase the DARM gain, it will ask you to confirm before each step is taken.  The script should get you all the way to arm powers of 9, which is pretty much exactly 100pm according to Q's Mist plot that is posted.

The CARM and DARM loops (around the UGFs) don't seem to be appreciably changing shape as I increase the arm powers up to 9 (as long as I increase the DARM loop gain appropriately).  So, we may be able to go a little bit farther, but since we're at about 100pm, it might be time to look at whether we think REFL11 or REFLDC is going to be more promising in terms of loop stability for the rest of the way to resonance.

Here are some plots from this evening. 

First, the time I was able to get to and hold at arm powers of 9.  I have a striptool to show the long time trends, and then zooms of the lockloss.  I do not see any particular oscillations or anything that strikes me as the cause for the lockloss.  If anyone sees something, that would be helpful.




This next lockloss was interesting because the DARM started oscillating as soon as the normalization matrix elements were turned on for DARM on DC transmissions.  The script should be measuring values and putting in matrix elements that don't change the gain when they are turned on, but perhaps something didn't work as expected.  Anyhow, the arm powers were only 1ish at the time of lockloss.  There was some kind of glitch in the DARM_OUT (see 2nd plot below, and zoom in 3rd plot), but it doesn't seem to have caused the lockloss.




  10637   Fri Oct 24 02:14:05 2014 JenneUpdateLSCIncreased DARM gain even more

[Jenne, Diego]

We spent the afternoon working on the new scan for IR resonance script.  It is getting much closer, although we need to work on a plan for the fine scanning at the end - so far, the result from the wavelet thing mis-estimates the true peak phase, and so if we jump to where it recommends, we are only at about half of the arm resonance.  So, in progress, but moving forward.

Tonight we repeated the process of reducing the CARM offset and measuring the DARM loop gain as we went.  I'm not sure if I just had the wrong numbers yesterday, or if the gains are changing day-by-day.  The gains that it wanted at given arm buildups were constant throughout this evening, but they are about a factor of 2 higher than yesterday.  If they really do change, we may need to implement a UGF servo for DARM.  New gains are in the carm_cm_up script.

We also actually saved our DARM loop measurements as a function of CARM offset (as indicated by arm buildups).  The loop stays the same through arm powers of 4.  However, once we get to arm powers of 6, the magnitude around 100 Hz starts to flatten out, and we get some weird features in the phase.  It's almost like the phase bubble has a peak growing out of it.  I saw these yesterday, and they just keep getting more pronounced as we go up to arm powers of 7, 8 and 9 (where we lost lock during the measurement).  The very last point in the power=9 trace was just before/during the lockloss, so I don't know if we trust it, or if it is real and telling us something important.  But, I think that it's time to see about getting both CARM and DARM onto a different set of error signals now that we're at about 100pm.


  2000   Thu Sep 24 21:04:15 2009 JenneUpdateMOPAIncreasing the power from the MOPA

[Jenne, Rana, Koji]

Since the MOPA has been having a bad few weeks (and got even more significantly worse in the last day or so), we opened up the MOPA box to increase the power.  This involved some adjusting of the NPRO, and some adjusting of the alignment between the NPRO and the Amplifier.  Afterward, the power out of the MOPA box was increased.  Hooray! 

Steps taken:

0.  Before we touched anything, the AMPMON was 2.26, PMC_Trans was 2.23, PSL-126MOPA_126MON was 152 (and when the photodiode was blocked, it's dark reading was 23).

1.  We took off the side panel of the MOPA box nearest the NPRO, to gain access to the potentiometers that control the NPRO settings.  We selectively changed some of the pots while watching PSL-126MOPA_126MON on Striptool.

2.  We adjusted the pot labeled "DTEMP" first. (You have to use a dental mirror to see the labels on the PCB, but they're there). We went 3.25 turns clockwise, and got the 126MON to 158. 

3. To give us some elbow room, we changed the PSL-126MOPA_126CURADJ from +10.000 to 0.000 so that we have some space to move around on the slider.  This changed 126MON to 142. The 126MOPA_CURMON was at 2.308.

4.  We tried adjusting the "USR_CUR" pot, which is labeled "POWER" on the back panel of the NPRO (you reach this pot through a hole in the back of the NPRO, not through the side which we took off, like all the other pots today).  This pot did nothing at all, so we left it in its original position.  This may have been disabled since we use the slider.

5.  We adjusted the CUR_SET pot, and got the 126MON up to 185.  This changed the 126MOPA_CURMON to 2. 772 and the AMPMON to 2.45

We decided that that was enough fiddling with the NPRO, and moved on to adjusting the alignment into the Amplifier.

6.  We teed off of the AMPMON photodiode so that we could see the DC values on a DMM.  When we used a T to connect both the DMM and the regular DAQ cable, the DMM read a value a factor of 2 smaller than when the DMM was connected directly to the PD.  This shouldn't happen.....it's something on the to-fix-someday list.

7.  Rana adjusted the 2 steering mirrors immediately in front of the amplifier, inside the MOPA box.  This changed the DMM reading from its original 0.204 to 0.210, and the AMPMON reading from 2.45 to 2.55. While this did help increase the power, the mirrors weren't really moved very much.

8.  We then noticed that the beam wasn't really well aligned onto the AMPMON PD.  When Rana leaned on the MOPA box, the PD's reading changed.  So we moved the PD a little bit to maximize its readings.  After this, the AMPMON read 2.68, and the DMM read 0.220.

9.  Then Rana adjusted the 2 waveplates in the path from the NPRO to the Amplifier.  The first waveplate in the path didn't really change anything.  Adjusting the 2nd waveplate gave us an AMPMON of 2.72, and a DMM reading of 0.222.

10.  We closed up the MOPA box, and locked the PMC.  Unfortunately, the PMC_Trans was only 1.78, down from the 2.26 when we began our activities.  Not so great, considering that in the end, the MOPA power went up from 2.26 to 2.72.

11.  Koji and I adjusted the steering mirrors in front of the PMC, but we could not get a transmission higher than 1.78.

12.  We came back to the control room, and changed the 126MOPA_126CURADJ slider to -2.263 which gives a 126MOPA_CURMON to 2.503.  This increased PMC_TRANS up to 2.1. 

13.  Koji did a bit more steering mirror adjustment, but didn't get any more improvement.

14.  Koji then did a scan of the FSS SLOW actuator, and found a better temperature place (~ -5.0)for the laser to sit in.  This place (presumably with less mode hopping) lets the PMC_TRANS get up to 2.3, almost 2.4.  We leave things at this place, with the 126MOPA_126CURADJ slider at -2.263. 

Now that the MOPA is putting out more power, we can adjust the waveplate before the PBS to determine how much power we dump, so that we have ~constant power all the time.


Also, the PMCR view on the Quad TVs in the Control Room has been changed so it actually is PMCR, not PMCT like it has been for a long time.

  2007   Sun Sep 27 12:52:56 2009 ranaUpdateMOPAIncreasing the power from the MOPA

This is a trend of the last 20 days. After our work with the NPRO, we have recovered only 5% in PMC trans power, although there's an apparent 15% increase in AMPMON.

The AMPMON increase is partly fake; the AMPMON PD has too much of an ND filter in front of it and it has a strong angle dependence. In the future, we should not use this filter in a permanent setup. This is not a humidity dependence.

The recovery of the refcav power mainly came from tweaking the two steering mirrors just before and just after the 21.5 MHz PC. I used those knobs because that is the part of the refcav path closest to the initial disturbance (NPRO).

BTW, the cost of a 1W Innolight NPRO is $35k and a 2W Innolight NPRO is $53k. Since Jenne is on fellowship this year, we can afford the 2W laser, but she has to be given priority in naming the laser.

Attachment 1: Picture_3.png
ELOG V3.1.3-