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ID Date Author Typedown Category Subject
  2928   Thu May 13 23:59:46 2010 ZachSummaryIOOMC table leveled

 After the recent removal of the old IMMT and the relocation of the Faraday isolator, the MC table was tilted a bit (southward and slightly westward---as of when I opened the chamber this afternoon). I re-leveled it by putting an extra two rectangular ballast blocks on the stack that was already hanging off the NNE edge of the table (there are a total of 4 in the stack now). I also screwed down the circular block that Koji and I put between the Faraday and SM1 on Tuesday, and re-mounted the two wire harness towers onto the table.

Needless to say, this threw the MC way out of alignment. I spent the rest of the afternoon reacquiring alignment and getting it to lock robustly. Here is a summary:

  • I adjusted MC3 until I got the 2nd, 3rd+ pass beams to overlap with the input beam between MC1&3, then I adjusted MC2&1 semi-methodically until I got something flashing at the transmitted end. This took some time.
  • I went back into the control room, engaged the loops and acquired lock on the TEM00 mode, whereupon I found that the beam spot was WAY off center on MC2 (due to my meddling with all the mirrors to get resonance flashes). I began using the MC2_spot_up (etc) scripts we wrote the other day to re-center it.
  • After a few iterations, the lock became weak, and eventually gave out. This is because the REFL beam was falling off the RFPD (and being clipped by the iris on the AP table), so I moved the iris and re-centered the beam on the diode.
  • With that, I was able to get the MC2 spot more or less centered, but then I noticed that---though the lock was clearly strong as evidenced both by the REFL power dip and visually via the camera on MC2---it looked like crap on the CCD. It seemed like there was some higher order mode structure sloshing around on top of the 00 spot, which didn't make any sense, until I realized that it was just a diffraction pattern from the TRANS beam getting clipped somewhere on the way out of the vacuum system.
  • I went back to the AP table, where I noticed that the TRANS beam was hitting near the edges of several of the mirrors on the way back to the PSL table, including the first one out of the viewport, so I turned IM4 to center the beam on this mirror, then proceeded to center the beam on each mirror downstream and then onto the CCD.
  • After getting a clear picture of the transmission on the CCD, centering the spot even better on MC2, then fine-tuning MC2&3 to strengthen the lock, I went back to the MC table to check that the transmitted beam was still passing through the center of the Faraday, which, by none other than an act of God, it was.
  • Having done the necessary work in the tank, I ran the A2L_MC2 script to fine-tune the centering of the spot on MC2. It needed a couple steps up and to the side, but after that the actuator gains for pitch and yaw were both balanced again to within ~2%, which is only slightly above the measurement error. We will probably need to adjust this continually, especially during the upgrade, so I didn't bother with getting it better than that.

After that, I shut off the loops, blocked the beam, and put the light doors back on the tanks. Then I went to the parking lot, then I got in my car, etc, etc, etc.

  2929   Fri May 14 03:30:45 2010 KojiSummaryIOOMC table leveled

Thanks Zach.This was a great job.

It was not mentioned but: was the Faraday clamped down on the table?


  2931   Fri May 14 10:33:01 2010 ZachSummaryIOOMC table leveled

Ah... no, I didn't. That explains why there were loose dogclamps on the table. I wrapped them in foil and put them on the clean cart. Can this wait until the next time we open the tank (i.e. to measure the beam profile), or should I go over there and clamp it down today?


  2935   Sat May 15 04:13:33 2010 KojiSummaryIOOMC table leveled

Fixing at the next time is absolutely OK.


Ah... no, I didn't. That explains why there were loose dogclamps on the table. I wrapped them in foil and put them on the clean cart. Can this wait until the next time we open the tank (i.e. to measure the beam profile), or should I go over there and clamp it down today? 


  2995   Wed May 26 18:54:55 2010 AidanSummaryGreen LockingMounted Crystal 724 in the Doubling Oven

Andri and I mounted the Raicol Crystal #724 in one of the new Covesion Ovens. The procedure was the same as before - see elog entry here.

There was one issue - the glass plate that goes on top of the crystal is coated on one side with ITO (Indium-Tin Oxide) and it's not 100% certain that this was mounted in the correct orientation. It is virtually impossible to tell which side of the glass is coated.

The base plate of the oven was tapped for an M3 hole. We retapped it for an 8-32 and bolted it to a post and that one of the New Focus 4-axis translation stage. The assembly is currently bolted to the PSL table, awaiting use.

  3048   Thu Jun 3 22:33:31 2010 valeraSummaryCDSsimulated plant work

 I put matlab files and a summary into the 40m wiki for the fitting of the 40m Optickle transfer functions and generating digital filters for the simulated plant:


The filters are not loaded yet. Joe and Alex will make a rcg code to make a matrix of filters (currently 5x15=75 elements) which will enable the simulated plant tf's.

Joe and I tried to put a signal through the DARM loop but the signal was not going through the memory location in the scx part of the simulated plant.


Edit by Joe:

I was able to track it down to the spx model not running properly.  It needed the Burt Restore flag set to 1.  I hadn't done that since the last rebuild, so it wasn't actually calculating anything until I flipped that flag.  The data is now circulating all the way around.  If I turn on the final input (the same one with the initial 1.0 offset), the data circulates completely around and starts integrating up.  So the loop has been closed, just without all the correct filters in.

  3052   Sun Jun 6 08:08:05 2010 rana, sanjitSummaryElectronicsCapacitor Bridge Test

To get a feel for the Capacitive Bridge problems, we setup a simple bridge using fixed (1 nF) caps on a breadboard. We used an SR830 Lock-In amplifier to drive it and readout the noise.


We measured the cap values with an LCR meter. They were all within a few % of 0.99 nF.

With a 0.5 V drive to the top of the bridge, the A-B voltage was ~2 mV as expected from the matching of the capacitors.

(** Note about the gain in the SR830: In order to find the magnitude of the input referred signal, one has to divide by G. G = (10 V)/ Sensitivity. 'Sensitivity' is the setting on the front panel.)

  1. Directly measuring from Vs to ground gives 0.5 V, as expected. This is done to verify the calibration later on.
  2. Shorting the A and B wires to ground gives ~0 V and lets us measure the noise. On the spectrum analyzer it was ~400 nV/rHz at 100 Hz and rising slowly to 4 uV/rHz at 100 mHz. In this state, the sensitivity was 10 mV, so the overall gain was 1000. That gives an input referred level of ~0.4 nV/rHz at the input.
  3. Hooking up now to A-B: the signal is ~10x larger than the 'dark' noise everywhere. 2 uV/rHz @ 100 Hz, 10 uV/rHz @ 10 Hz, 50 uV/rHz @ 1 Hz. The spectrum is very non-stationary; changing by factors of several up and down between averages. Probably a problem with the cheapo contacts in the breadboard + wind. The gain in this state was still 1000. So at 1 Hz, its 50 nV/rHz referred to the input.

To convert into units of capacitance fluctuation, we multiply by the capacitance of the capacitors (1 nF) and divide out by the peak-peak voltage (1 V). So the bridge sensitivity is 50e-9 * 1e-9 = 5 x 10^-17 F/rHz.

If we assume that we will have a capacitive displacement transducer giving 1 nF capacitance change for a 0.1 mm displacement, this bridge would have a sensitivity of 5 x 10^-12 m/rHz @ 1 Hz. We would like to do ~50-100x better than this. The next steps should be:

  1. Solder it all together on a PCB to have less air current sensitivity and decent contacts.
  2. Use a low-noise FET input. Since the impedance of the bridge is ~5 kOhms at this frequency, we are probably current noise limited.
  3. Estimate the oscillator amplitude noise sensitivity.
  3061   Wed Jun 9 21:05:44 2010 ranaSummaryComputersop540m is not to be used

This is a reminder (mainly for Steve, who somehow doesn't believe these things) that op540m is not to be used for your general pleasure.

No web, no dataviewer, no DTT. Using these things often makes the graphical X-Windows crash. I have had to restart the StripTool, our seismic BLRMS and our Alarms many times because someone uses op540m, makes it crash, and then does not restart the processes.

Stop breaking op540m, Steve!

  3080   Wed Jun 16 11:31:19 2010 josephbSummaryComputersRemoved scaling fonts from medm on Allegra

Because it was driving me crazy while working on the new medm screens for the simulated plant, I went and removed the aliased font entries in /usr/share/X11/fonts/misc/fonts.alias that are associated with medm.  Specifically I removed the lines  starting with widgetDM_.  I made a backup in the same directory called fonts.alias.bak with the old lines.

Medm now behaves the same on op440m, rosalba, and allegra - i.e. it can't find the widgetDM_ scalable fonts and defaults to a legible fixed font.

  3091   Sun Jun 20 16:07:23 2010 KojiSummaryCOCCalibration of the metrology lab interferometer

Kiwamu and Koji


We have visited GariLynn's lab to make a calibration of the metrology interferometer. 

The newly calibrated value is

RoC(SRMU01) = 153.3+/- 1.6 [m]

This is to be compared with the specification of 142m +/- 5m

Although the calibration deviation from the previous value was found to be 1.3%, it is far from explaining the curvature difference between the spec (142m) and the measured value.


The previous measurements of the SRM curvatures showed larger RoCs by ~10% compared with the spec.

It can be caused by the mis-calibration of the pixel size of the CCD in the metrology interferometer.
In order to confirm the calibration value, an object with known dimension should be measured by the instrument.


We've got a flat blank optic from "Advanced Thin Film" together with a metalic ring.
The ring has been attached on the blank optic with 3 fragments of a double sided tape.
The RoC of SRMU1 was also measured in order to obtain "the radius of curvature of the day".

The calibration process is as follows:

  1. Measure the diameters of the ring by a caliper in advance to its attachment to the blank.
  2. Determine the inner and outer diameter of the ring in the obtained image.
    Note that the obtained image is pre-calibrated by the default value given by the measurement program
      (i.e. 0.270194mm/pixel for horizontal)
  3. Check the ratio of the diameters with the measured value by the caliper. Correct a systematic effect.
  4. Compare the image measurement and the caliper measurement.


  1. The outer and inner diameters of 2.000" and 1.660" (measured by a caliper, error 0.005"). The ratio is 0.830+/-0.003.
  2. The center and radius for the inner circle were estimated to be (79.7924, 91.6372) and 21.4025 [mm].
    The center and radius for the outer circle were estimated to be (79.6532, 91.6816) and 25.6925 [mm].

    The error would be ~0.01mm considering they sweep 500 pixels by the circle and the pixel size is 0.27mm. i.e. 0.27/Sqrt(500) ~ 0.01mm
  3. Ratio of the inner and outer diameter is 0.8330 +/- 0.0005.
    The systematic error of x is given by solving (21.4025+x)/(25.6925-x)=0.83 ==> x = -0.042 +/- 0.043 [mm]. This is just a 0.2% correction.
    By correcting the above effect, we get (Rin, Rout) = (21.36 +/- 0.046, 25.74 +/- 0.047).
  4. By comparing the result with the caliper measurement, we get calibration factor of 1.013 +/- 0.005.
    This means we measured "1mm" as "1.013mm". The scale was too small.

    We have got the calibration of 0.2737+/-0.0014 [mm/pixel].


Because of the calibration error, we measured too long RoC. The same day, we measured the curvature of SRMU01 as 155.26 m.
The newly calibrated value is

RoC(SRMU01) = 153.3+/- 1.6 [m]

This is the value to be compared with the specification of 142m +/- 5m


Attachment 1: ring1_inner_centering.pdf
Attachment 2: ring1_outer_centering.pdf
Attachment 3: SRMU01_pic.png
  3102   Wed Jun 23 12:28:34 2010 RazibSummaryPhase CameraWeeekly Summary

This past week I have completed the following tasks:


1. Built a trigger and power box for the camera GC 750M (06058) and took some test images to see whether the trigger box really works. Result: It is doing fine!

2. Went over the setup that is already sitting on the table. Ref: Aidan's elog entry

3. Attended seminars and talks given by Alan, Jahms, Koji and Rana.

4. Attended the mandatory laser safety training by Peter.


Expected task for this week (could be more):

1. Work out analytical expressions of the power of the carrier and sidebands going to the camera in the setup. (As suggested by Rana and Joe)

2. Work on producing beat signal to the camera using the He-Ne laser setup.

3. Move,if possible, to the Nd:YAG setup.

4. Go over the codes and paper by the past SURFers on the phase camera experiment.





Attachment 2: test1.png
  3106   Wed Jun 23 15:15:53 2010 josephbSummaryComputers40m computer security issue from last night and this morning

The following is not 100% accurate, but represents my understanding of the events currently.  I'm trying to get a full description from Christian and will hopefully be able to update this information later today.


Last night around 7:30 pm, Caltech detected evidence of computer virus located behind a linksys router with mac address matching our NAT router, and at the IP  We did not initially recognize the mac address as the routers because the labeled mac address was off by a digit, so we were looking for another old router for awhile.  In addition, pings to were not working from inside or outside of the martian network, but the router was clearly working.  

However, about 5 minutes after Christian and Mike left, I found I could ping the address.  When I placed the address into a web browser, the address brought us to the control interface for our NAT router (but only from the martian side, from the outside world it wasn't possible to reach it).

They turned logging on the router (which had been off by default) and started monitoring the traffic for a short time.  Some unusual IP addresses showed up, and Mike said something about someone trying to IP spoof warning coming up.  Something about a file sharing port showing up was briefly mentioned as well.

The outside IP address was changed to and dhcp which apparently was on, was turned off.  The password was changed and is in the usual place we keep router passwords.

Update: Christian said Mike has written up a security report and that he'll talk to him tomorrow and forward the relevant information to me.  He notes there is possibly an infected laptop/workstation still at large.  This could also be a personal laptop that was accidently connected to the martian network.  Since it was found to be set to dhcp, its possible a laptop was connected to the wrong side and the user might not have realized this.


  3125   Sat Jun 26 21:13:19 2010 ranaSummaryComputer Scripts / ProgramsCOMSOL 4.0 Installation

I've installed COMSOL 4.0 for 32/64 bit Linux in /cvs/cds/caltech/apps/linux64/COMSOL40/

It seems to work, sort of.


  1. It did NOT work according to the instructions. The CentOS automount had mounted /dev/scd0 on /media/COMSOL40. In this configuration, I was getting a permission denied error when trying to run the default setup script. I did a 'sudo umount /dev/scd0' to get rid of this bad mount and then remounted using 'sudo mount /dev/dvd /mnt'. After doing this, I ran the setup script '/mnt/setup' and got the GUI which started installing as usual.
  2. I also pointed it at the linux64/matlab/ installation.
  3. It seems to not work right on Rosalba because of my previous java episode. The x-forwarding from megatron also fails. It does work on allegra, however.
  3127   Mon Jun 28 12:48:04 2010 josephbSummaryCDSCDS adapter board notes

The following is according to the drawing by Ben Abbott found at http://www.ligo.caltech.edu/~babbott/40m_sus_wiring.pdf

This applies to SUS:

Two ICS 110Bs.  Each has 2 (4 total) 44 shielded conductors going to DAQ Interface Chassis  (D990147-A).  See pages 2 and 4.

Three Pentek 6102 Analog Outputs to LSC Anti-Image Board (D000186 Rev A).  Each connected via 40 conductor ribbon cable (so 3 total). See page 5.

Eight XY220 to various whitening and dewhitening filters.  50 conductor ribbon cable for each (8 total). See page 10.

Three Pentek 6102 Analog Input to Op Lev interface board. 40 conductor ribbon cable for each (3 total).  See page 13.


The following look to be part of the AUX crate, and thus don't need replacement:

Five VMIC113A to various Coil Drives, Optical Levers, and Whitening boards.  64 conductor ribbon cable for each (5 total). See page 11.

Three XY220 to various Coil boards. 50 conductor ribbon for each (3 total).  See page 11.

The following is according to the drawing by Jay found at http://www.ligo.caltech.edu/~jay/drawings/d020006-03.pdf

This applies to WFS and LSC:

Two XY220 to whitening 1 and 2 boards.  50 conductor ribbon for each (2 total).  See page 3.

Pentek 6102 to LSC Anti-image. 50 conductor ribbon. (1 total). See page 5.


The following are unclear if they belong to the FE or the Aux crate.  Unable to check the physical setup at the moment.

One VMIC3113A to LSC I & Q, RFAM, QPD INT. 64 conductor ribbon cable. (Total 1).  See page 4.

One XY220 to QPD Int.  50 conductor ribbon cable. (Total 1). See page 4.


The following look to be part of WFS, and aren't needed:

Two Pentek 6102 Analog Input to WFS boards. 40 conductor ribbon cables (2 Total). See page 1.

The following are part of the Aux crate, and don't need to be replaced:

Two VMIC3113A to Demods, PD, MC servo amp, PZT driver, Anti-imaging board. 64 conductor ribbon cable (2 Total). See page 3.

Two XY220 to Demods, MC Servo Amp, QPD Int boards.  50 conductor ribbon cable (2 Total). See page 3.

Three VMIC4116 to Demod and whitening boards.  50 conductor ribbon cable (3 Total). See page 3.

  3129   Mon Jun 28 21:26:05 2010 ranaSummaryCDSCDS adapter board notes

Those drawings are an OK start, but its obvious that things have changed at the 40m since 2002. We cannot rely on these drawings to determine all of the channel counts, etc.

I thought we had already been through all this...If not, we'll have to spend one afternoon going around and marking it all up. 

  3163   Wed Jul 7 00:15:29 2010 tara,RanaSummaryPSLpower spectral density from RefCav transmitted beam

I measured the RC transmitted light signals here at the 40m. I made all connections through the PSL patch panel.

Other than two steering mirrors in front of the periscope, and the steering mirror for the RFPD which were used to steer

the beam into the cavity and the RFPD respectively, no optics are adjusted.

We re-aligned the beam into the cavity (the DC level increased from 2 V to 3.83V) (Fig2) (We could not recover the power back to what it was 90 days ago)

and the reflected beam to the center of the RFPD.


I measured the spectral density of the signal of the transmitted beam behind RefCav in both time and frequency domain.

This will be compared with the result from PSL lab later, so I can see how stable the signal should be.

I did not convert Vrms/rtHz to Hz/rtHz because I only look at the relative intensity of the transmitted beam which will be compared to the setup at PSL lab. 



 We care about this power fluctuation because we plan to measure

 photo refractive noise on the cavity's mirros

(this is the noise caused by dn/dT in the coatings and the substrate,

the absorption from fluctuating power on the coating/mirror changes

the temperature which eventually changes the effective length of the cavity as seen by the laser.)


      The plan is to modulate the power of the beam going into the cavity,

the absorption from ac part will induce frequency noise which we want to see.

Since the transmitted power of the cavity is proportional to the power inside the cavity.

 Fluctuations  from other factors, for example, gain setting,  will limit our measurement. 

That's why we are concerned about the stability of the transmitted beam and made this measurement.


Attachment 1: RIN_rftrans.png
Attachment 2: tara.png
  3164   Wed Jul 7 10:42:29 2010 KojiSummaryPSLpower spectral density from RefCav transmitted beam

How do you calibrate this to Hz/rtHz?


I measured the RC transmitted light signals here at the 40m. I made all connections through the PSL patch panel. No optics/PD were touched.

I measured the spectral density of the signal of the transmitted beam behind RefCav in both time and frequency domain.

This will be compared with the result from PSL lab later, so I can see how stable the signal should be.

We re-aligned the beam into the cavity (the DC level increased from 2 V to 3.83V)

and the reflected beam to the center of the RFPD.



  3186   Fri Jul 9 11:41:58 2010 GopalSummaryOptic StacksTop Optic Layer Complete; Mechanical Tests Giving Problems

For the last week, I have been attempting to determine the mirror stack transfer function which relates mechanical mirror response to a given ground-motion drive. The idea is to model the stacks in COMSOL and ultimately apply mechanical tests for manual calculation.


Procuring the correct drawings to base my 3D models off of was no simple task. There are two binders full of a random assortment of drawings, and some of them are associated with the smaller chambers, while others are appropriate for the main chamber, which is what we're interested in right now. For future workers, I suggest checking that your drawings are appropriate for the task at hand with other people before wasting time beginning the painstaking process of CAD design in COMSOL.


The drawings that I ultimately decided to use are attached below. They detail four layers of stacks, each which arrange 15, 12, 8, and 5 (going from bottom to top) Viton damping springs in an orderly fashion. The numbers have been chosen to keep the load per spring as constant as possible, in order for all springs to oscillate with as close a resonant frequency to each other as possible.


Stack_1_Drawing.JPG   Stack_2_Drawing.JPG


 Stack_3_Drawing.JPG    Stack_4_Drawing.JPG




After making some minor simplifications, I have finished modeling the top stack:




After triangular meshing, before my many failed attempts at mechanical testing:




Both the Viton and steel portions have been given their material properties, and so I should be (theoretically ) ready to perform some eigenfrequency calculations on this simplified system. If my predictions are correct, these eigenfrequencies shouldn’t be too far of the eigenfrequencies of the 4-layer stacked system, because of the layout of the springs. I’ve tried doing mechanical tests on the top stack alone, but there hasn’t been much progress yet on this end, mostly because of some boundary value exceptions that COMSOL keeps throwing at me.


In the next couple weeks or so, I plan to extend this model to combine all four layers into one completed stack, along with a simple steel base and mirror platform. I also plan to figure out how to make eigenfrequency and transfer function measurements.


Lastly, to anyone who is experienced with COMSOL, I am facing two major roadblocks and could really use your help:


1) How to import one model into another, merge models together, or copy and paste the same model over and over.

2) Understanding and debugging run-time errors during mechanical testing.


If you have any idea how to attack either of these issues, please talk to me! Thanks!


  3189   Fri Jul 9 20:16:19 2010 ranaSummaryPSLThings I did to the PSL today: Refcav, PMC, cameras, etc.

I re-aligned the beam into the PMC. I got basically no improvement. So I instead changed the .LOW setting so that PMCTRANS would no longer go yellow and make the donkey sound.

I did the same for the MOPA's AMPMON because its decayed state is now nominal.


Steve and I removed the thermal insulation from around the reference cavity vacuum chamber. It wasn't really any good anyways.

Here are the denuded photos:


Steve and I are now planning to replace the foam with some good foam, but before that we will wrap the RC chamber with copper sheets like you would wrap a filet mignon with applewood bacon.

This should reduce the thermal gradients across the can. We will then mount the sensors directly to the copper sheet using thermal epoxy. We will also use copper to cover most of this hugely

oversized window flange - we only need a ~1" hole to get the 0.3 mm beam out of there.


My hope is that all of this will improve the temperature stability of this cavity. Right now the daily frequency fluctuations of the NPRO (locked to the RC) are ~100 MHz. This implies

that the cavity dT = (100 MHz) / (299792458 / 1064e-9) / (5e-7) = 1 deg.    That's sad....


I also changed the RC_REFL cam to manual gain from AGC. I cranked it to max gain so that we can see the REFL image better.

  3190   Sun Jul 11 20:11:48 2010 ranaSummaryPSLRC trend after the insulation removal



  3196   Mon Jul 12 14:22:36 2010 JenneSummaryPSLThings I did to the PSL today: Refcav, PMC, cameras, etc.


I re-aligned the beam into the PMC. I got basically no improvement. So I instead changed the .LOW setting so that PMCTRANS would no longer go yellow and make the donkey sound.

I did the same for the MOPA's AMPMON because its decayed state is now nominal.

[Jenne, Chip]

The alarm was still going, because the LOLO setting was higher than the LOW, which is a little bit silly.  So we changed the .LOLO setting to 0.80 (the LOW was set to 0.82)

We also changed psl.db to reflect these values, so that they'll be in there the next time c1psl gets rebooted.

  3210   Tue Jul 13 21:04:49 2010 tara,ranaSummaryPSLTransfer function of FSS servo

 I measured FSS's open loop transfer function.

For FSS servo schematic, see D040105-B.  

4395A's source out is connected to Test point 2 on the patch panel.

Test Point 2 is enabled by FSS medm screen.

"A" channel is connected to In1, on the patch panel.

"R" channel is connected to In2, on the patch panel.

the plot shows signal from A/R.

Note that the magnitude has not been corrected for the impedance match yet.

So the real UGF will be different from the plot.



4395A setup


network analyzer mode

frequency span 1k - 10MHz

Intermediate frequency bandwidth 100Hz

Attenuator: 0 for both channels

Source out power: -30 dBm

sweep log frequency


medm screen setup


TP2: enabled

Common gain -4.8 dB

Fast Gain 16 dB

Attachment 1: TF_FSS_ser.png
  3212   Wed Jul 14 01:05:27 2010 Sharmila,KatharineSummaryelogMaglev

Yesterday we hooked up the Quadrant Maglev control to the power supply to test the components in the Input/Output part of the circuit.

The output from the buffer was an unexpected high noise signal which was caused by some circuit components.

Consequently these were replaced/removed after confirming the source of noise.

The following is a story of how it was done.

To test the components of input/output, we measured the output across TP_PD3(Test Point -Photo Diode 3).
We got a high noise signal with a frequency of several kHz.

We tested the values of various electronic components. The resistances R5 and R6 did not measure as mentioned(each had a value of 50 K in the schematic). The value of R6 was 10 K and we replaced R5 with a 10 K resistor. We still got the noise signal at 5.760 kHz with a Pk-Pk voltage of 2.6 V. The resistors in R-LED measured 1.5 K instead of the marked 2.2 K.

We had three suspects in hand:

  • BUF634P : A buffer from the Sallen-Key filter to the LED.
  • C24 : A capacitor which is a part of the Sallen-Key filter.
  • C23 : A capacitor in the feedback circuit of the Sallen-Key filter.

BUF634P : The data sheet for the BUF634P instructed a short across the 1-4 terminals in the presence of capacitive load.  We followed this to overcome the effect(if any) of the extra-long BNC cables which we were using. The oscilloscope still waved 'Hi!' at a few kHz. We removed the buffer and also the feedback resistor R42 from the circuit, what we were testing boiled down to measuring the output of the Sallen-Key filter. The output still contained the funny yet properly periodic signal at a few kHz.      


C24: Removing C24 did not do any good.

C23: As a final step C23 was removed. And ... We got a stable DC at 9.86 V(almost stable DC with a low noise at a few MHz). C24 and the buffer were replaced and output seemed fine. The output was a high frequency sine wave which was riding on a DC of 9.96 V.



We rechecked if the LED was on and the infrared viewer gave a positive signal.

We went ahead obtaining the transfer function of the feedback control for which we used a spectrum analyzer.

The input for feedback system is a photo current whereas the spectrum analyzer tests the circuit with a voltage impulse.  Hence the voltage input from the spectrum analyzer needs to be converted into current of suitable amplitude(few microamps) for testing the spectrum analyzer.  Similarly the output which is a coil current needs to be changed to a voltage output through a load for feeding into the channel of the spectrum analyzer. We used a suitable resistance box with BNC receiving ends to do this. We obtained a plot for the transfer function which is shown below.


Future plans:

- Check the calculated transfer functions with the plot of the spectrum analyzer

- Model the entire(OSEM, magnet, actuators etc.) system in Simulink and calculate the overall transfer function

- Stable levitation of the 1X1 system

  3217   Wed Jul 14 12:12:03 2010 RazibSummaryPhase CameraWeekly update

This week I was mainly interested in investigating the noise source at the phase camera. So having this issue in mind, my activities are the following:

1. I worked on producing multiple beat signal (1Hz and 5Hz). Elog entry.

2. I altered the setup so that instead of triggering the camera from the signal generator, we are now triggering it from the beat signal from the reference beam and sideband.

3. I made the nice little aluminium table for all the amplifiers, mixer and splitters to sit at one place instead of floating around.

4. I talked with Aidan and Joe and verified my calculation and extended it to further investigation of the noise source in the setup.


Plan for the upcoming week:

1. Measure and calibrate the camera w.r.t the power incident on it.

2. Investigate the noise source.

  3223   Wed Jul 14 19:15:26 2010 GopalSummaryOptic StacksREVISION: Eigenfrequency Analysis of Single Stack Complete

My previous eigenfrequency analysis was incorrect by two orders of magnitude due to the misuse of Young's Modulus information for Viton. After editing this parameter (as documented on 7/14 19:00), the eigenmodes became much more reasonable. I also discovered the Deformation option under the Surface Plotting Options, which makes the eigenmodes of the single stack much more apparant.

Attached are pictures of the first four eigenmodes:

First Eigenmode: y-translational, 7.49 Hz


Second Eigenmode: x-translational, 7.55 Hz


Third Eigenmode: z-rotational, 8.63 Hz


Fourth Eigenmode: z-translational, 18.26 Hz



Attachment 2: Eigenfrequency_2_Stack4.png
  3232   Thu Jul 15 19:27:04 2010 ranaSummaryPSLRC trend after the insulation removal


As you can see, there was not much (if any) worsening of the laser frequency fluctuation from removing the RefCav insulation. The plots below are zooomed in:


I have used the same peak-to-peak scale so that its easy to compare the fluctuations before (LEFT) and after (RIGHT).

As you can clearly see, the laser frequency moves just as much now (the SLOW_DC) as it did before when it had the insulation. Only now the apparent (i.e. fake) RC temperature fluctuations are much larger. So this sensor is fairly useless as configured.

  3247   Mon Jul 19 21:47:36 2010 ranaSummaryDAQDAQ timing test

Since we now have a good measurement of the phase noise of the Rb clock Marconi locked to the Rb clock, I wanted to use that to check out the old DAQ system:

I used Megan's phase noise setup - Marconi #2 is putting out 11000013 Hz at 13 dBm into the ZP-3MH mixer. Marconi #1 is putting out 3 dBm at 11000000 Hz into the RF input.

The output goes through a 50 Ohm load and then a Mini-Circuits BNC LP filter (either 2 or 5 MHz). Then an SR560 set for low noise, G = 5, AC coupling, 1-pole LP @ 1 kHz.

This SR560 output goes into the channel C1:IOO-MC_DRUM1 (which is sampled at 16384 Hz with ICS-110B after the usual Sander Liu AA chassis containing the INA134s).

  3260   Wed Jul 21 15:43:38 2010 MeganSummaryPSLCopper Layer Thickness on the Reference Cavity

Using the equation for thermal resistance

Rthermal = L/(k*A)

where k is the thermal conductivity of a material, L is the length, and A is the surface area through which the heat passes, I could find the thermal resistance of the copper and stainless steel on the reference cavity. To reduce temperature gradients across the vacuum chamber, the thermal resistance of the copper must be the same or less than that of the stainless steel. Since the copper is directly on top of the stainless steel, the length and width will be the same for both, just the thickness will be different (for ease of calculation, I assumed flat, rectangular strips of the metal). Assuming we wish to have a thermal resistance of the copper n times less than that of the stainless steel, we have

RCu = RSS/n


L/(kCu*w*tCu) = L/(kSS*w*tSS*n)

so that

tCu/tSS = n*kSS/kCu

We know that kSS = 401 W/m*K and KCu = 16 W/m*K, so

tCu/tSS = 0.0399*n

By using the drawings for the short reference cavity vacuum chamber (the only one I could find drawings for online) I found a thickness of the walls of 0.12 in or 0.3048 cm. So for the same thermal resistance in both metals, the copper must be 0.0122 cm thick and for a thermal resistance 10 times less, it must be 0.122 cm thick. So we will have to keep wrapping the copper on the vacuum chamber!

  3299   Tue Jul 27 16:03:36 2010 ranaSummaryDAQDAQ timing test


Since we now have a good measurement of the phase noise of the Rb clock Marconi locked to the Rb clock, I wanted to use that to check out the old DAQ system:

I used Megan's phase noise setup - Marconi #2 is putting out 11000013 Hz at 13 dBm into the ZP-3MH mixer. Marconi #1 is putting out 3 dBm at 11000000 Hz into the RF input.

The output goes through a 50 Ohm load and then a Mini-Circuits BNC LP filter (either 2 or 5 MHz). Then an SR560 set for low noise, G = 5, AC coupling, 1-pole LP @ 1 kHz.

This SR560 output goes into the channel C1:IOO-MC_DRUM1 (which is sampled at 16384 Hz with ICS-110B after the usual Sander Liu AA chassis containing the INA134s).

 This is the 0.3 mHz BW spectrum of this test - as you can see the apparent linewidth (assuming the width is all caused by the DAQ jitter) is comparable to the BW and therefore not resolved.

Basically, the Hanning window function is not sharp enough to do this test and so I will do it offline in Matlab.

Attachment 1: Untitled.png
  3300   Tue Jul 27 16:33:50 2010 KojiSummaryGeneralHigh school students tour

Jenne made the 40m tour for the annual visit of 30-40 students.


Tour 2009 http://nodus.ligo.caltech.edu:8080/40m/1717

Tour 2008 http://nodus.ligo.caltech.edu:8080/40m/737


Attachment 1: IMG_2657.jpg
  3317   Thu Jul 29 12:13:28 2010 kiwamuSummaryCDSnear term plan

 [Joe and Kiwamu]


  3318   Thu Jul 29 12:31:09 2010 KojiSummaryGeneralLab Schedule

29 Thu BS chamber work: Move cable towers / green steering mirrors / (2 TTs with TT charactrization) / Put the heavy door by 5PM.
30 Fri Pumping down
31 Sat WFS work by Nancy

1 Sun - 5 Thu WFS work by Nancy
5 Thu PSL Table prep
6 Fri PSL Table prep / Likely to shut down the PSL

9 Mon PSL Table prep / shutting down of the PSL (optional)
10 Tue PSL box Frame lifting
12 Thu PSL table tapping

16 Mon - 17 Tue concrete pouring preparation
19 Thu - 23 Fri Tripod placement
24 Tue - 26 Thu concrete pouring

Attachment 1: PSL_work_schedule.pdf
  3324   Thu Jul 29 20:43:32 2010 GopalSummaryOptic StacksModeling Tips and Tilts

I have discovered a method of completely characterizing the 6x6 response of all six types (x-,y-, and z- translational/rotational) of oscillatory disturbances at the base of the stack.

  • "Tipping" drives are trivial, and simply require a face load in the appropriate direction.
  • "Tilting" drives could use a torque, but I am instead implementing multiple edge loads in opposing directions to create the appropriate net curl. This curl will be kept constant across the three axes for sake of comparing the resulting transfer functions.
  • "Tipping" responses are once again trivial, and merely require the displacement vector of the top center coordinate to be recorded.
  • "Tilting" responses require the normal vector to be recorded and manipulated to produce the angular coordinates (assuming right-handed coordinate system):
    • θx = tan-1(x/z)
    • θy = tan-1(y/z)
    • θz = tan-1(y/x)

The first three concepts have been confirmed through simulations to produce correct transfer functions. The last test seems to be producing some problems, in that the vector normal to the equilibrium position (an obvious and useless piece of information) is sometimes given instead of the vector normal to the position of maximum displacement. This means that, as of now, I have the capability of measure the half of the complete 6x6 matrix of transfer functions in the coming weeks. The first three of eighteen transfer functions are attached below and will be included in my progress report.


  3339   Sat Jul 31 04:03:11 2010 GopalSummaryOptic StacksComplete Displacement Translational Transfer Function Matrix

Over the past 36 hours, I've run full-fledged FDAs on KALLO.

The transfer functions for translational drives and responses are neatly described by the attached transfer function "matrix."


Next steps:

1) Extend the 3x3 analysis to include tilts and rotations in a 6x6 analysis.

2) Figure out how to do the same types of tests for phase instead of displacement.

  3345   Sun Aug 1 21:04:45 2010 ranaSummaryComputer Scripts / ProgramsMC Autolocker fixed

Someone had left a typo in the MC autolocker script recently while trying to set the lock threshold to 0.09. As a result, the autlocker wouldn't run.

I repaired it, made a few readability improvements, and checked in the new version to the SVN. If you make script changes, check them in. If you think its too minor of a change for a SVN checkin, don't do it at all.

  3346   Sun Aug 1 21:40:27 2010 ranaSummaryPSLFSS: SLOWDC response

I bet you thought that the NPRO slow actuator response could be well represented by a pole at ~0.1 Hz? Well, that's just what they want you to believe.

I attach the response measured in FSS-FAST (with no feedback to the SLOW actuator) when the SLOW is given a step. As you may remember from

kindergarten, the response of a single pole low pass should just be an exponential. Clearly, there's more here than 1 pole.

 I also inserted a factor of 0.01 in the FSSSlowServo code so I could make the gain sliders have reasonable values (they used to all be ~1e-3). The SVN and the MEDM snapshot are updated.

Attachment 1: Untitled.png
  3378   Fri Aug 6 17:47:36 2010 steveSummaryGeneralcranes load tested at 1998 lbs




The guy from KroneCrane (sp?) came today and started the crane inspection on the X End Crane. There were issues with our crane so he's going to resume on Monday. We turned off the MOPA fur the duration of the inspection.

  1. None of our cranes have oil in the gearbox and it seems that they never did since they have never been maintained. Sloppy installation job. The crane oiling guy is going to come in on Monday.
  2. They tried to test the X-End crane with 2500 lbs. (its a 1 ton crane). This tripped the thermal overload on the crane as intended with this test. Unfortunately, the thermal overload switch disabled the 'goes down' circuit instead of the 'goes up' circuit as it should. We double checked the wiring diagram to confirm our hypothesis. Seems the X-End crane was wired up incorrectly in the first place 16 years ago. We'll have to get this fixed.

The plan is that they will bring enough weight to test it at slightly over the rating (1 Ton + 10 %) and we'll retry the certification after the oiling on Monday.

 The south end crane has one more flaw. The wall cantilever is imbalanced: meaning it wants to rotate south ward, because its axis is off.

This effects the rope winding on the drum as it is shown on Atm2

Atm1 is showing Jay Swar of KoneCrane and the two 1250 lbs load that was used for the test. Overloading the crane at 125% is general practice at load testing.

It was good to see that the load brakes were working well at 2500 lbs. Finally we found a good service company! and thanks for Rana and Alberto

for coming in on Saturday.

 Jeff Stinson, technician of KoneCrane inspected the south end crane hoist gear box. This was the one that was really low on oil. The full condition require

~ 950cc of EPX-7 (50-70W) high viscosity gear oil. The remaining 120 cc oil was drained and the gear box cover was removed. See Atm 1

He found the gear box, load brake and gearing in good condition. The slow periodic sound of the drive was explained by the split bearings at Atm 3

The Vertex and the east end crane gear boxes needed only 60 cc oil to be added to each Atm 4 and their drives were tested.

Conclusion: all 3 gear boxes and drives are in good working condition.

Tomorrow's plan: load test at 1 ton and correct-check  3 phase wiring.

 Atm1, service report: load test were performed at max horizontal reach with 1998 lbs ( American Ton is 2000 lbs)

          Vertical drives and brakes worked well. The 5 minutes sagging test showed less than 1 mm movement .

          The wiring is correct. Earlier hypothesis regarding the wiring ignored the mechanical brake action.

Our cranes are certified now. Operator training and SOP is in the work.

Vertex Folding I -beam will get latch-lock and the south end I-beam will be leveled.

Atm2, south end

Atm3, east end

Atm4, folding crane at ITMX at 14 ft horizontal reach

Attachment 1: 0.9ton.PDF
Attachment 2: P1060523.JPG
Attachment 3: P1060532.JPG
Attachment 4: P1060541.JPG
  3382   Sat Aug 7 10:47:38 2010 KojiSummaryelogelog restarted / source of the trouble eliminated

Nancy notified me that the elog crashed. It was fixed.

I restarted elog, but it kept crashing. Some of the entries on Aug 6th caused the trouble.

I tried to refresh the pictures in entries 3376, 3377, 3378. Still it kept crashing.
I started to dig into the elog file itself. (/cvs/cds/caltech/elog/elog-2.7.5/logbooks/40m/100806a.log)

FInally I found that there was some invalid reply links in the entry 3379.

Date: Fri, 06 Aug 2010 19:29:59 -0700
Reply to: 3379
In reply to: 3379

The entry is refering this entry itself. That is weird. So I deleted the reply-to and in-reply-to lines.
Then elogd got happy.

In fact, 3379 was a dupulication of 3380, so I deleted this entry.

  3385   Sat Aug 7 21:57:56 2010 ranaSummaryDMFseisBLRMS restarted

The green xterm on op540m which is running the seisBLRMS DMF got stuck somehow ~3 days ago and lost its NDS connection. I closed the matlab session and restarted it. Seismic trends are now back online.

Attachment 1: Untitled.png
  3395   Tue Aug 10 22:40:55 2010 KojiSummaryPEMAccelerometer located on and below the PSL table

Result of the accelerometer measurement


We wanted to characterize the PSL table before the work before its lifting up.
We put a set of three-axis Wilcoxon accelerometers on the ground and another set on the PSL table through the weekend.


- The data at 9th Aug 00:00(UTC) is used. This was Sunday 5PM in the local time.
- The freq resolution was 0.01Hz. The # of avg was 50.

- The accelerometer signals were calibrated by the value 1.2e-7 V/(m/s^2). We use this absolute value of the spectrum for the comparison purpose.

- The accelerometers were aligned to North(X), East(Y), and Up(Z). There was the coherence observed from 2~20Hz.
  The transfer functions are valid only this frequency region although we still can set the lower bound of them.

- The transfer functions in the horizontal directions show huge peaks at around 20Hz. The Q of the peaks are ~30 to ~100.
  The vertical transfer function shows somewhat lower peak at around 50Hz with Q of ~10.

Some thoughts

- The low resonant freq and the high Q of the horizontal mode comes from the heaviness of the table.

- We are going to raise the table. This will usually mean that we get the lower resonant freq. This is not nice.

- So, the decision to use 6 tripods rather than 4 was right.
- The steel tripods are expected to give both more rigidity and more damping than the chep-looking hollow Newport legs.
- Concrete grouting of the tripods will also lower the effective height and will benefit for us.


Attachment 1: PEM_100809.pdf
  3403   Wed Aug 11 16:56:00 2010 KojiSummaryEnvironmentCovering of the IFO

Katharine, Sharmila, Gopal, Kiwamu, Jenne, Aidan, Steve, and Koji

A guy from the carpenter shop has done the drilling work in the morning.

In the afternoon we wrapped the central part of the interferometer with plastic sheets in order to avoid the dusts from the tile ripping that will happen tomorrow.

Attachment 1: IMG_2732.jpg
  3423   Fri Aug 13 20:58:20 2010 JennaSummaryElectronicsRubidium clock phase noise measurement

 Here's an overview of the rubidium measurement:





 We have two SRS FS275 Rubidium clocks which are locked together using the built-in PLL through the 1pps input/output. The default time constant for this locking is 18.2 hours because it's designed to be locked to a GPS. We changed this time constant to .57 hours (as decribed in this elog entry) to get the clocks to more reliably lock to each other. We then mix the 10MHz outputs together using a 7dbm mixer (see elog here and picture below)



The signal then goes through an AC-coupled SR560 with a gain of 100 and LPF at 10kHz, and is then fed into the DAQ. In the first picture below you can make out what all the lights are labeled, and in the second you can see what lights are on. I couldn't get a picture that did both in one, sadly.



  3472   Wed Aug 25 16:13:32 2010 steveSummaryPEMPSL optical table is back into operation at 32.75" level

The tile work was done yesterday after noon.

This morning Mike Gerfen and me lowered the enclosure frame to normal height.

Keven- janitor and I removed plastic covers from chambers, racks, SP, MC2 and clean tool boxes.


The afternoon Jenne, Kiwamu, Joe and Aiden cleaned the enclosure inside out. The particle count measured zero inside the enclosure with HEPAs on when the covers were

removed. The MOPA and all other components were happy to see us in excellent condition.

This table height is very user friendly!


Safety grounds were reconnected.


Atm1, new tiles around the concrete slab

Atm2, frame lowered with low cross bars reinstalled

Atm3, the enclosure frame's north west foot is connected to ground

Atm4, PSL optical table is connected to ground at the north east corner through 1 Mohm

Atm5, PSL optical table level at a stimulating, back-friendly height

Attachment 1: P1060764.JPG
Attachment 2: P1060768.JPG
Attachment 3: P1060777.JPG
Attachment 4: P1060776.JPG
Attachment 5: P1060780.JPG
  3487   Mon Aug 30 13:57:25 2010 KojiSummaryPSLPSL table vibrational performance after the upgrade

Jenne and Koji

Last week Jenne has put the accelerometers on and under the PSL table immediately after the plastic sheets were removed.

So I took the same measurement as I did on 9th Aug.

Here is the comparison of the vibrational performance of the table before and after the modification.

Basically the table is now stiffer and more damped than it was before.
We don't find any eminent structure below (at least) 70Hz.

This result is obtained despite elevating of the table.

1) Attachment 1

For the horizontal comparison (top),  it is clearly seen that the large resonant peak at 20Hz was eliminated.
At least the new resonances went up to 70-90Hz region. Y is basically equivalent to X.

For the vertical comparison (bottom), it is clearly seen that the resonant peaks at around 50 & 70Hz were eliminated. 
At least no new resonance is seen.

2) Attachment 2

All-in-one plot for the measurement --- spectra, coherences, transfer functions --- after the upgrade. I put the same plot for the one before the upgrade.

Attachment 1: PEM_100830_SPE.pdf
Attachment 2: PEM_100830.pdf
PEM_100830.pdf PEM_100830.pdf
  3488   Mon Aug 30 18:22:00 2010 ranaSummaryPSLPSL Enclosure is UNSTABLE

The lifting and resetting of the BLUE PSL enclosure has made it unstable somehow. When I push on it a little it rocks back and forth a lot.

Steve, please look into what's happening and stiffen it if you can. Its too unstable right now.

  3513   Thu Sep 2 14:11:17 2010 steveSummaryPEMsouth end crane balancing is completed

The crane I -beam now leveled at all degrees of rotation.  The lower hinge was moved southward  about 1/4 of an inch.  Performance was tested at 2000 lbs


Atm1, work in progress

Atm2, load test at 1 Ton

Atm3, service report

Attachment 1: P1060798.JPG
Attachment 2: P1060800.JPG
Attachment 3: P1060804.JPG
  3545   Wed Sep 8 11:56:24 2010 kiwamuSummaryCDSSeptember CDS test plan

 Joe and Kiwamu

We discussed about our CDS plan for this September. The summary of the plan and "to do list" are now on the wiki page;



  Basically there are three major missions that we will do in this month;

1. complete damping of the vertex suspensions
2. Preparation for Green locking
3. Development of Simulated Plants

 We also try to keep updating the wiki page.

  3567   Mon Sep 13 12:09:42 2010 kiwamuSummaryGeneralelog restarted

 Elog didn't respond, so I restarted it with the script.

Before killing the process somehow two elog daemons were running at the same time. I killed those two manually. 

  3576   Wed Sep 15 14:34:57 2010 josephbSummaryCDSPlan for RFM switch over

Steps for RFM switch over:

1) Ensure the new frame builder code is working properly:

   A) Get Alex to finish compiling the frame builder and test on Megatron.

   B) Test the new frame builder code on fb40m (which is running Solaris) in a reversible way.  Change directory structure away from Data1, Data2, to use actual times.

   C) Confirm new frame builder code still records slow channels (c1dcuepics).

2) Ensure awg, tpman, and diagnostic codes (dtt) are working with the new front end code.

3) Physically move RFM cables from old front ends to the new front ends.  Remove excess connections from the network.

4) Merge the megatron/c1sus/c1iscex/c1ioo network with the main network.

   A) Update all the network settings on the machines as well as Linux1

   B) Remove the network switch separating the networks.

4) Start the new frame builder code on fb40m.

  3579   Wed Sep 15 19:29:13 2010 valeraSummary PSL power budget
 Location  Power (mW)
 NPRO - after HWP  252
 Rejected by input FI polarizer  38
 After output FI polarizer  175
 Into PMC  164
 PMC reflected  37
 PMC transmitted  71
 PMC leakage  1.5
 After PMC TRANS PD/Camera BS


 After RefCav EOM  1.1
 Into RefCav  0.3


- NPRO injection current 1.0 A

- PMC losses ~32%

- FSS AOM diffraction efficiency ~52%

ELOG V3.1.3-