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ID Date Author Typeup Category Subject
  12213   Thu Jun 23 17:24:32 2016 ericqUpdateGeneralTweaks

I spent some time this afternoon reviving some of my CESAR/ESCOBAR shenanigans on the Y arm. I found it neccesary to adjust a few things.

  • PMC realigned 
  • ETMY oplev centered
  • Y End green realigned
  • PSL/Y Green beat realigned

Afterwards, ALSY noise levels were good. 

  12215   Mon Jun 27 15:12:09 2016 varunUpdateCDSDAFI update: stereo output

Using an RC to BNC connector from the inner drawer, I have added a second output cable going from the output Fibox in the control room to the audio mixer.


I have updated the DAFI with the following changes:

1) Separated both the channels of stereo output completely, as well as in the GUI.

2) Added text monitors for the inputs and outputs.

The stereo output is now ready except for a cable going from the second channel of the output fibox to the audio mixer.

Attached is the main DAF_OVERVIEW screen and its link button from the LSC screen labelled "DAFI"


I wish to have stereo audio output for the DAF module. Hence, there needs to be a second output from the DAF. I added this second output to the model. Following are the details:

FiBox: It consists of two analog inputs which are digitized and multiplexed and transmitted optically. (only 1 fiber is needed due to multiplexing). Attachment 1 shows the fibox with its 2 analog inputs (one of which, is connected), and 1 fiber output. The output of the DAF goes to the FiBox. Until today, the Fibox recieved only 1 analog input. This analog signal comes from the DAC-8 (count starting from 0), which is located at "CH 1 OUT" SMA output in the "MONITORS" bin on the racks (attachment 2).

I have added another output channel to the DAF model both in software and in hardware. The DAF now also uses DAC-9 analog output which goes to the second analog input of the FiBox. The DAC-9 output is located at "CH 2 OUT" SMA output in the "MONITORS" bin on the racks (attachment 4).

After making the changes, the Fibox is shown in attacment 3.

Testing: The LSC input on passing through the DAF block is given through two different DAC outputs, to the same Fibox channel (one after the other), and the output is heard. More concrete testing will be done tomorrow. It will be as follows:

1) Currently, I need to search for a suitable cable that would connect the second channel of the output fibox to the audio mixer. After doing this, end to end testing of both channels will be done.

2) I could not access the AWG, probably because the DAQ was offline today afternoon. Using a signal from the AWG will give a more concrete testing of the stereo output.

3) After this, I will separate the two channels of the stereo completely (currectly they are seperated only at the DAF output stage)

4) I also will edit the medm gui appropriately.



I have added Enable buttons for each of the DSP blocks, and labels for the matrix elements. The input matrix takes inputs from each of the 4 channels: ADC1, ADC2, LSC and EXC, and routes them to the audio processing blocks (attachment 2). The output matrix (attachment 3) takes the outputs of the various DSP blocks and routes them to the output and then to the speakers. 




Attachment 1: IMG_20160627_151753247.jpg
  12217   Mon Jun 27 15:47:17 2016 SteveUpdateGeneralQPR clean room gloves

I got some QPR Nitrile gloves. They are LIGO approved.White nitrile gloves are naturally anti-static- 109 ohms

Their touch not as good as laytex  gloves but try to use them.


  12218   Tue Jun 28 09:14:27 2016 SteveUpdateSUS ETMX optics preparation to be rehanged

Given the effect on the contrast defect, the consensus at the meeting Wednesday 6-22  was that we should continue to use the existing ETMX optic. 

Does this imply that we can simply:
  • Vent
  • Remove the current ETMX suspension, and optic from the suspension
  • Replace the standoffs (and guide rod if necessary), leaving the current magnets in place
  • Re-suspend on the current, existing suspension, with new wire clamps
That is, if we are keeping the current optic, do we gain anything by replacing the whole suspension? Is there any reason to remove and replace magnets? (The wire clamps do need to be replaced, as a groove forms when they are installed.)
This could allow us to vent and execute this whole thing sooner. 
-Eric Q.
Yes, I think this is a reasonable approach. Besides the wire standoffs and wireclamps, the only other problem might by a worn groove in the top piece of the suspension (not the clamp piece, but the piece that the clamp holds the wire up against).
How about use the current ETM, but put it into the new suspension body with new wire standoffs?

D Location

Number on






 Baked Clean

 Pieces Needed



In Stock

(on tower )

31,20,19,13 viton tips   not cut yet baked material in stock
30 6-32x0.75" stops 4 (4)  
29 steel music wire 0.017" not baked on roll  needs good wipes
28  1/4 "washer 4 (4)  
27 lock washer 4 50 install
26 Ag plated 1/4-20x1.25 4 (4)  
25 Ag plated1/4-25x.75 & not plated 20 (20)  
24 SS 4-40x.5 2 (2)  
23 SS 4-40x.38 4 (4)  
22 spring plunger 4+2 (4+2)  
18 magnets, 1.9mm od, length 3.2 mm 5 ~30 not coated, rusty buy Ni coated ones for future use
17 guide rod, 0.635 mm od, 3.3 mm 3 6 Al
16 wire standoff, 1 mm od, 4.8 mm 2 2 Al and ruby (ruby groove not centered)
15 short OSEMs 5 6  
14 spare ETMX in 40m wiki 1 1  confirmed in cabinet
12 dumbbell standoff 5 6  
11 Al stiffening plate 1 (1)  
10 wire clamp B in sus block 2 (2)  
9 wire clamp A 1 (1)  
8-7 lower clamp for lifting optics 2 (2)  
6 upper clamp to hold down optic 1 (1)  
5-4 left-right side of tower  1 ea (1ea)  
3 tower base 1 (1)  
2 sus block 1 (1)  
1 lower and upper OSEM holders 1ea (1ea)  
48 sandind fixture for magnet&dumbbell      
45 magnet-dumbbell assemblly fixture 1 1  
43 guide rod gluing fixture     shipped from LOH .... D000335...needs cleaning
  First contact   3-15-2013 purchase check expiration date OK
  FCPEEK peeler ring disk for TM cleaning 10 front,10 back side  have sheets only 32&19mm ID punches ordered
  GordonBrush custom for LIGO optical cleaning ~5 1 (3/8wide nylonSS) more from Calum available
  EP30-2 epoxy have  have expiration date 9-24-2016

NOT finished, last edited 6-28


Attachment 1: nylonFCss.jpg
  12219   Tue Jun 28 16:06:09 2016 gautamUpdateCOCRC folding mirrors - further checks

Having investigated the mode-overlap as a function of RoC of the PRC and SRC folding mirrors, I've now been looking into possible stability issues, with the help of some code that EricQ wrote some time back for a similar investigation, but using Finesse to calculate the round trip Gouy phase and other relevant parameters for our current IFO configuration. 

To do so, I've been using:

  1. Most up to date arm length measurements of 37.81m for the Y arm and 37.79m for the X arm
  2. RoCs of all the mirrors from the phase map summary page
  3. Loss numbers from our November investigations

As a first check, I used flat folding mirrors to see what the HOM coupling structure into the IFO is like (the idea being then to track the positions of HOM resonances in terms of CARM offset as I sweep the RoC of the folding mirror). 

However, just working with the flat folding mirror configuration suggests that there are order 2 22MHz and order 4 44MHz HOM resonances that are really close to the carrier resonance (see attached plots). This seems to be originating from the fact that the Y-arm length is 37.81m (while the "ideal" length is 37.795m), and also the fact that the ETM RoCs are ~3m larger than the design specification of 57m. Interestingly, this problem isn't completely mitigated if we use the ideal arm lengths, although the order 2 resonances do move further away from the carrier resonance, but are still around a CARM offset of +/- 2nm. If we use the design RoC for the ETMs of 57m, then the HOM resonances move completely off the scale of these plots... 

Attachment 1: C1_HOMcurves_Y.pdf
Attachment 2: C1_HOMcurves_DR.pdf
  12220   Tue Jun 28 16:09:41 2016 PrafulUpdateGeneral40m Summary Pages

Set up gwsumm on optimus and generated summary pages from both L1 and C1 data. Still a few manual steps need to be taken during generation, not fully automated due to some network/username issues. nds2 now working from optimus after restarting nds2 server.

  12221   Tue Jun 28 16:10:49 2016 PrafulUpdateGeneralBluebird Microphones

Found 1 out of 2 bluebird microphones in the 40m.

  12222   Tue Jun 28 17:11:27 2016 PrafulUpdateGeneralEM172 Microphones

Found 60 EM172 microphones. Previous elog with details: 7777.

  12224   Tue Jun 28 22:54:43 2016 AakashUpdateGeneralSeismometer Enclosure Development | SURF 2016

The existing enclosure for seismometer at LIGO 40m lab is a cylindrical stainless steel can placed upside down over the seismometer. It has more empty space between the seismometer and the internal surface of enclosure which is not desirable(I'll quantitatively elaborate this statement once my temperature measuring setup is ready).


Stainless steel has a thermal conductivity in the range of 16.3 to 16.7 W/m/K and magnetic permeability 1.260e-6 H/m.Assuming an ambient temperature 298K, and the temperature inside the enclosure as 295K, as well as substituting all the values for dimesions and material properties of existing enclosure,
k=16.4 W/mK, μ=1.260e-6 H/m, L=2ft=0.6096m, b=r2 =0.5ft=0.1524m, thickness=5mm, a=r1 =0.1474m.
So by using the textbook relations(I have mentioned them in my report), the value of attenuation coefficient is 5.953584e-05 and the value of rate of heat transfer= 5.64913 kW. The attenuation coefficient value is quite better for steel but proper care needs to be taken to avoid heat transfer. For studying the variation of rate of heat transfer and attenuation with the thickness of enclosure material, I have plotted the following attached graphs for different materials which include hardened stainless steel, aluminium, pure iron and nanoperm-muMetal.



About Data Acquisation

I have already invested a lot of time to configure and use acromag busworks card over ethernet. So now I have made an arrangement to measure temperature by AD592CNZ temperature transducer IC. I would be using raspberry pi for acquiring data untill I figure out a way to use acromag busworks card for the same. This setup of acquiring logging temperature using raspberry pi is mostly ready except the calibration part.

  12225   Wed Jun 29 00:09:36 2016 AakashUpdateGeneralThings from past | SURF 2016

I have taken out the heaters and temperature sensors from the enclosure which was made by Megan last summer. Soon I will test and configure those heaters.

  12226   Wed Jun 29 08:20:04 2016 SteveUpdateSUS First Contact shelf life
We'll follow LIGO policy:
Our policy is to use first contact within 1 year of purchase for use in the interferometers.  For inspection use I am comfortable with out-of-date use.

GaryLinn offered their indate First Contact for use.


  12227   Wed Jun 29 14:32:22 2016 SteveUpdateSUS how to remove epoxy from optics


Hi Steve -

I found the doc I was looking for:


Specifically, you might find guidance in Section 5 and the pictures at the end of the doc.  This should work for Vacseal as well.

Good luck - it will take some time (hours to day or 2)...
I'll be interested to know how it goes.

GariLynn helped us develop this procedure so you could also ask her to cast an eye over the setup if you are worried.


ps: there is no existing fixture to hold SOS optic while soaking it

  12228   Wed Jun 29 15:34:00 2016 SteveUpdatesafetySURF 2016 safety

Praful Vasiceddy received 40m specific basic safety training.


Aakash Patil received 40m specific basic safety training.


Hello, I am Varun Kelkar. I will be working at the 40m lab as a SURF student this summer with Eric Quintero on Audio processing for real time control system signals. This week I will mostly be working on implementing basic DSP C-code offline. Currently I am trying to write a code for noise whitening.


Varun has received 40m specific basic safety training today.



  12229   Wed Jun 29 16:02:29 2016 SteveUpdateSUS ETMX beam baffle

In the attached photo from 2012, one can see the installed black glass baffle. According to the drawings (LIGO-DNNNXXX) this one has a clear aperture of 40 mm.

In (someplace ?) we have clean baffles with a 50 mm aperture which can be installed during this vent. In order to be more conservative, let us choose to swap these out for all 4 test masses during the upcoming vent using the green laser as an alignment guide, as Koji described at today's lunch meeting.

They are located at the top of E1 drawer cabinet

Attachment 1: IMG_1608.JPG
  12230   Wed Jun 29 16:05:47 2016 ericqUpdateSUSETMX suspension readiness

I've gone through the SOS suspension document (E970037) and some old elogs to get an idea of all the accesories we need for the process of suspending, aside from the tower itself, which Steve has already put together. Gautam and I have laid our eyes upon most of the critical pieces. Some other objects are unknown, and perhaps not strictly neccesary. 

Confirmed to exist:

  • Guide rod gluing fixture
  • 3 axis micrometer + microscope doohicky
  • PZT buzzer (for fine standoff positioning)
  • Winch fixture (the plate maybe doesn't fit perfectly on the top of the SOS tower, but one bolt will probably work)
  • Spare guide rods and ruby standoffs
  • Magnet+dumbell gluing fixture (in case we need to glue a new magnet+dumbell pair)
  • Magnet to optic gluing fixture (including "pickle pickers"/grippers)
  • 0.017" suspension wire
  • HeNe laser + QPD + beam height target (confirmed working on scope)

In addition, I am told that we have a long ribbon cable that can run from the X end to the clean room to enable OSEM damping control while we do the pitch alignment.

Things mentioned in the procedure I have not found:

  • Something called an "SOS set screw tool" (D961412)
    • Not mentioned specifically what this is for
  • Edmund scientific pocket measuring microscope + bushing
    • Seems to be intended for centering OSEM holding plate on the magnet position. I found no mention of this use in 40m elogs. It can likely be done by eye
  • SOS cleaning bracket (D970181)
    • This is likely for the old liquinox cleaning procedure. We'll be using first contact.

Some other tasks and their status:

  • Check cleanroom table levelling:
    • Done via 12" spirit level, looks good
  • Glue removal strategy / fixture
    • Steve is working on this
  • Cut and apply viton tips to earthquake stops
    • Either gautam will do this, or we will use the current suspension's stops
  12231   Thu Jun 30 10:03:16 2016 SteveUpdateSUS how to remove epoxy from optics

Proposed Acetone soak dish for SOS epoxy softening.

It has good acces through 5" top ID. The set up is stable and teflon lined.

Materials: glass jar with SS cover, teflon bricks, 0.008" teflon wrapped "high density Drever bricks" and aluminum

Drever brick: I beleive it is a Tungsten alloy. We used it as vac-bat savor at the coffe can. It has high density, heavy and hard, it was never identified.

I will soak one brick  to see if it has any reaction ability with acetone.


NO means that only Glass and Teflon can be used for this fixture in  Acetone. We can not take a chance on the coating!

I guess the small surface area Aluminum dumbbell, guide rod and-or wire standoff, magnet and epoxy does not degrade the acetone such way that it effects our coating.

Not ot mention, that only the very edge of the coating would in this solution.



Attachment 1: SOSsoakDish.jpg
Attachment 2: SOSsoakDish_tv.jpg
  12232   Thu Jun 30 14:31:02 2016 ChemistryUpdateSUSNO

  12233   Thu Jun 30 16:11:57 2016 ericqUpdateGeneralVent Prep

I have updated the vent prep checklist on the wiki. Gautam and I did the following things from it:

  • Center all oplevs, transmon QPDs 
    • ETMX oplev has not been centered, since it's moving around so much, and we're going to immediately move the suspension anyways.
  • Align the arm cavities for IR and align the green lasers to the arms. 
    • AUX X Green was aligned while the X arm was well aligned. Soon thereafter, ETMX wandered away, but the green will remain a good reference
  • Update the SUS Dritmon values 
  • Reconcile all SDF differences 
  • Reduce input power to no more than 100mW by adjusting wave plate+PBS setup on the PSL table BEFORE the PMC. (Using the WP + PBS that already exist after the laser.) 

  • Replace 10% BS before MC REFL PD with Y1 mirror and lock MC at low power.
    • I don't think we've vented since the most recent slew of changes to the IMC servo, so its not surprising that the current low power scripts don't work. I'm working on locking the IMC, but this does not prevent us from initiating the vent tomorrow.


The following bullets have not yet been executed:

  • Close shutter of PSL-IR and green shutters at the ends 
  • Make sure the jam nuts are protecting bellows 
  • Check crane functionality & cleanliness 

  • Turn off HV into vacuum: OMC is not wired this time 
  • Particle count must be under 10,000 counts / cf min for 0.5 micron 
  • Check all metal window covers are on. 
  • Check 5 cylinders (24 cft size) of instrument grade air, called Alfa Gas 1 in stock.
  12234   Thu Jun 30 16:21:32 2016 gautamUpdateCOCSideband HOMs resonating in arms

[EricQ, gautam]

Last night, we set about trying to see if we could measure and verify the predictions of the simulations, and if there are indeed HOM sidebands co-resonating with the carrier. Koji pointed out that if we clip the transmitted beam from the arm incident on a PD, then the power of the higher order HG modes no longer integrate to 0 (i.e. the orthogonality is broken), and so if there are indeed some co-resonating modes, we should be able to see the beat between them on a spectrum analyzer. The procedure we followed was:

  1. Choose a suitable PD to measure the beat. We chose to use the Thorlabs PDA10CF because it has ~150MHz bandwidth, and also the responsivity is reasonable at 1064nm.
  2. We started our measurements at the Y-end. There was a sufficiently fast lens in the beam path between the transmon QPD and the high gain PD at the Y end, so we went ahead and simply switched out the high gain thorlabs PDA520 for the PDA10CF. To power the PDA10CF, we borrowed the power cable from the green REFL PD temporarily.
  3. We maximized the DC power of the photodiode signal using an oscilloscope. Then to introduce the above-mentioned clipping and orthogonality-breaking, we misaligned the beam on the PD until the DC power was ~2/3 the maximum value. 
  4. We then hooked up the PD output to the Agilent network analizyer (with a DC block).
  5. We measured the spectrum of the PD signal around 11.066MHz (with 100kHz span) and higher harmonics up to 55MHz and used a narrow bandwidth (100Hz) and long integration time (64 averages) to see if we could find any peaks. More details in the results section.
  6. Having satisfied ourselves with the Y-end measurements, we 
  • restored the power cable to the green beat PD
  • re-installed the thorlabs PDA520 
  • verified that both IR and green could be locked to the arm

We then repeated the above steps at the X-end (but here, an additional lens had to be installed to focus the IR beam onto the PDA10CF - there was, however, sufficient space on the table so we didn't need to remove the PDA520 for this measurement).


Y-end: DC power on the photodiode at optimal alignment ~ 200mV => spectra taken by deliberately misaligning the beam incident on the PD till the DC power was ~120mV (see remarks about these values).

RF sideband (Y-arm) Peak height (uV) Beat power (nW) RF sideband (X-arm) Peak height (uV) Beat Power (nW)
11 1.55 0.52 11 1.2 0.4
22 10.6 3.53 22 none seen N.A.
33 none seen N.A. 33 none seen N.A.
44 22.0 7.33 44 7 2.33
55 8.6 2.97 55 5 1.67

I converted the peak heights seen on the spectrum analyzer in volts to power by dividing by transimpedance (=5*10^3 V/A into a 50ohm load) * responsivity at 1064nm (~0.6A/W for PDA10CF).


  1. This effect flagged by the simulations seems to be real. Unfortunately I can't get a more quantitative picture because we can't quantify the mode-overlap between the carrier 00 mode and any higher order mode on the beat PD (as we know nothing about the profile of these modes), but the simulations did suggets that the 2nd order 22MHz and 4th order 44MHz HOMs are the ones closest to the carrier 00 resonance (see Attachments #2 and #3), which is kind of borne out by these results. 
  2. I disbelieve the conversions into power that I have done above, but have just put them in for now, because a DC power of 200mW at the Y-end suggests that there is >160uW of light transmitted from the arm, which is at least twice what we expect from a simple FP cavity calculation with the best-known parameters. If I've missed out something obvious in doing this conversion, please let me know! 
  3. For the Y-arm, the region around 55MHz had a peak (presumably from the sideband HOM beating with the carrier) but also a bunch of other weird sub-structures. I'm attaching a photo of the analyzer screen. Not sure what to make of this...
Attachment 1: image.jpeg
Attachment 2: C1_HOMcurves_Y.pdf
Attachment 3: C1_HOMcurves_X.pdf
  12235   Thu Jun 30 21:24:36 2016 ericqUpdateGeneralVent Prep

Steve has ordered some teflon parts to take the place of the metal parts in his acetone-soaking jig. They should arrive tomorrow. 

So, we will be begin the venting process tomorrow. Doors to come off on Tuesday.

  12236   Fri Jul 1 01:52:54 2016 AakashUpdateGeneralSeismometer Enclosure Development | SURF 2016

I have transferred most of the temperature measurement stuff from the front area to seismometer at the end of Y-arm.  While arranging the components I have taken all care that they will not interfere with existing system. Also, I have temporarily taken a monitor from the front area to the area near same seismometer as I couldn't talk to Rpi via ssh. For next twelve hours, I am now recording temperature inside as well as outside the seismometer enclosure. Some temperature sensors are inside the enclosure while some are outside the seismometer enclosure.


  12237   Fri Jul 1 09:20:44 2016 SteveUpdateVACvent 78


1, Fix ETMX sus "jump issue"

2, First Contact clean the arms

3, Install new spare cold cathode and convectron gauges: InstruTech-Hornet

4, Install 50 mm apeture beam baffles

5, Check and clean optical quality viewport from inside


The following bullets were executed:

  • Closed shutter of PSL-IR and green shutters at the ends 
  • Checked jam nuts are protecting bellows 
  • Check crane functionality & cleanliness last week

  • Particle count must be under 10,000 counts / cf min for 0.5 micron 
  • Checked all metal window covers are on. 
  • Check 5 cylinders (24 cft size) of instrument grade air, called Alfa Gas 1 in stock.
  • Took pictures of medm screens: sus-sum, aligned oplevs pos, alignment values and vac configuration
  • Turned Oplev servos off
  • Closed V1 and VM1, opened VM2
  • Opened VV1 manual valve to Nitrogen cylinder and let the P1 to rise to 25 Torr
  • Switched over to Instrument Grade Air Cylinder and continoed the vent with 8-10 PSI reading at the pressure regulator

We are venting the 40m IFO



Steve has ordered some teflon parts to take the place of the metal parts in his acetone-soaking jig. They should arrive tomorrow. 

So, we will be begin the venting process tomorrow. Doors to come off on Tuesday.


Attachment 1: vent78.png
Attachment 2: vent78at250T.png
  12238   Fri Jul 1 15:48:10 2016 SteveUpdateVACvent 78 at 710 Torr

I just disconnected the 6th instrument grade air cylinder from the vacuum envelope at 720 Torr. Now it will reach equilibrium through a filter as it sucks in lab air.

This is the sure way not to over pressurize the chamber.


Attachment 1: pd78at710T.png
  12240   Mon Jul 4 10:30:37 2016 ericqUpdateGeneralPreliminary vent plans

Here are some plans / rough procedures for this week's vent. It is unlikely that I have though of everything, but this should be a reasonable starting point.

The mode cleaner still hasn't been locked in air, we may not want to touch the Y arm optics until we are able to lock to the Y arm and dither align, so we are sure to keep the input pointing from drifting away too much.

Primary objectives:

  • Re-suspend ETMX
  • First contact of all arm cavity optics

Secondary objectives:

  • Install new gauges
  • Replace 40mm baffles with 50mm baffles
  • Check cleanliness of inner viewport surfaces

ETMX project

  • Open ETMX chamber
  • Take all manner of photos of ETMX suspension in-situ
    • If some kind of obvious issue is evident, fix it, proceed accordingly
  • Mark suspension position
  • Move suspension to edge of the table, more pictures + inspection
  • Move suspension to flow bench, remove optic
  • Transport optic to clean room
  • Acetone soaking / standoff removal
  • Re-glue side magnet
  • Re-glue guide rod + standoff
  • OSEM transplant from old to new suspension
  • Suspend, following SOS suspension procedure
  • Drive optic around, see if jumps are evident
  • Clean with first contact
  • Reinstall optic, align, etc.

Optic cleaning

For $optic in [ITMX, ITMY, ETMY]:

  • Open chamber
  • Take many, many pictures
  • Mark suspension position
  • move suspension to edge, take pictures of HR surfaces
  • Mark OSEM orientation, remove oems
  • Clean AR and HR surfaces with first contact
  • Reinstall OSEMS at proper position, rotate to minimize bounce/roll coupling
  • Reinstall optic, align, etc.
  12241   Tue Jul 5 09:25:31 2016 SteveUpdateSUS how to remove epoxy from optics

Glass soaking dish with teflon guides.


Proposed Acetone soak dish for SOS epoxy softening.

It has good acces through 5" top ID. The set up is stable and teflon lined.

Materials: glass jar with SS cover, teflon bricks, 0.008" teflon wrapped "high density Drever bricks" and aluminum

Drever brick: I beleive it is a Tungsten alloy. We used it as vac-bat savor at the coffe can. It has high density, heavy and hard, it was never identified.

I will soak one brick  to see if it has any reaction ability with acetone.


NO means that only Glass and Teflon can be used for this fixture in  Acetone. We can not take a chance on the coating!

I guess the small surface area Aluminum dumbbell, guide rod and-or wire standoff, magnet and epoxy does not degrade the acetone such way that it effects our coating.

Not ot mention, that only the very edge of the coating would in this solution.




Attachment 1: SOSsoakingDish.jpg
Attachment 2: SOSsoakingD.jpg
  12242   Tue Jul 5 14:12:56 2016 varunUpdateElectronicsAntialiasing Filter Update

I am trying to design an antialiasing filter, which also has two switchable whitening stages. I have designed a first version of a PCB for this.

The board takes differential input through PCB mountable BNCs. It consists of an instrumentaiton amplifier made using quad opamp ADA4004, followed by two whitening blocks, also made using ADA4004, which can be bypassed if needed, depending upon a control input. The mux used for this purpose is Maxim MAX4158EUA. These two whitening blocks are followed by 2 the LPF stages. A third LPF stage could be added if needed. These use AD829 opamps. After the LPFs are two amplifiers for giving a differential output through two output BNCs. The schematic is shown in attachment 1: "AA.pdf". The top layers of the layout are shown in attachment 2 (AAtop.pdf), the bottom layers in attachment 3 (AAbottom.pdf), and the entire layout in attachment 4 (AAbrd.pdf). 

The board has 6 layers (in the order from top to bottom):

1) Top signal layer; 

2) Internal plane 1 (GND),

3) Internal plane 2 (+15V),

4) Internal plane 3 (-15V),

5) Internal plane 4 (GND),

6) Bottom signal layer. 

Power: +15, -15 and GND is given through a 4 pin header connector. 

The dimensions of the board are 1550 mil \times 6115 mil (38.1mm\times155.3mm) and the overall dimensions including the protruding BNC edges are 1550 mil \times 7675 mil (38.1mm\times194.9mm)

I would like to have inputs on the layout telling me if any component/trace needs to be changed/better placed, any other things about the board need to be changed, etc.


P.S.: I have also added a zipped folder "AA.zip" containing the schematic and board files, as well as the above pdfs.

Attachment 1: AA.pdf
Attachment 2: AAtop.pdf
Attachment 3: AAbottom.pdf
Attachment 4: AAbrd.pdf
Attachment 5: AA.zip
  12243   Tue Jul 5 17:14:02 2016 ericqUpdateGeneralVent progress

Rough summary of today's progress:

  • IMC locked, reasonably aligned. (Only have MC2 trans reference, no WFS)
    • FSS Slow lock threshold got lowered to 1k MC2 trans
    • Autolocker doesn't really work, though I made some modifcations to it that reflect the manual locking that works
  • TTs, PRMI optics moved around until AS and REFL spots looked good. 
    • Small flashes visible in TRY
    • ND filter on Y transmon QPD removed, since we have so little light
  • Y arm was not locked, but this was deemed suitable to proceed
  • Heavy doors taken off ETMX and ITMX chambers, light doors put on.
  • Went into ETMX chamber, poked around, took a bunch of pictures (Gautam is uploading has uploaded to picasa (foteee account), the two best ones of the stand-offs on either side are attached, although I guess we can't really conclude anything from these except that on the side with the OSEM, there seems to be a few extra stray bits of epoxy residue...)
  • Removed ETMX side OSEM to get a picture of that side of optic (it is currently off, ETMX watchdog shutdown for now...)
  • Checked that table is level with clean spirit level (it was to within the resolution of the spirit level which is quoted as 0.42mm/m)

I didn't really see anything out of the ordinary on the ETMX suspension. Earthquake stops had clearance, OSEMS were secure, no visible glue degredation on face magnets. Inspection with green LED flashlight didn't reveal any obscene dirtieness on either face, just a few particles here and there. The top of the opic barrel unsurprisingly has a good amount of particulate. The wire grooves are way too small to resolve anything at this point, other than that they exist.

The suspension footprint is already marked, tomorrow we can move the suspension closer to the door to get an even closer look at it, before removing it from the chamber. 

Attachment 1: noOsemSide.JPG
Attachment 2: OSEMside.JPG
  12244   Tue Jul 5 18:44:39 2016 PrafulUpdateComputer Scripts / ProgramsWorking 40m Summary Pages

After hardware errors prevented me from using optimus, I switched my generation of summary pages back to the clusters. A day's worth of data is still too much to process using one computer, but I have successfully made summary pages for a timescales of a couple of hours on this site: https://ldas-jobs.ligo.caltech.edu/~praful.vasireddy/


Currently, I'm working on learning the current plot-generation code so that it can eventually be modified to include an interactive component (e.g., hovering over a point on a timeseries would display the GPS time). Also, the 40m summary pages have been down for the past 3 weeks but should be up and working soon as the clusters are now alive.

  12245   Tue Jul 5 19:10:41 2016 ranaUpdateGeneralVent progress

I'd suggest clamping and moving it to the flow bench so you can inspect with a bright light. Then remove the wire and inspect the standoff, but hurry up with getting it in the soak bath so you can start on the cleaning of the other ones.

I wonder if we're really sure that its a mechanical problem with ETMX.

Gautam tells me that the local damping was always ON when looking for the jumps. This means that the coil driver was still hooked up and we can't rule out glitches in the DAC or the coil driver.

The UL OSEM shows the biggest movement (10 microns). The LR shows the second most (6-7 microns). The others are 2x less. So its consistent with a voltage change on UL,

Is this consistent with a slip in one of the wire standoffs? I think no.


Attachment 1: jumpEvent20151105.png
  12246   Tue Jul 5 21:51:35 2016 ericqUpdateGeneralVent progress

One glitch was seen to occur without a change in the output voltage monitors in ELOG 11744

  12247   Tue Jul 5 23:38:42 2016 gautamUpdateGeneralVent progress - ETMX SUS Coil driver electronics investigation

With Koji's help, I've hacked together an arrangement that will allow us to monitor the output of the coil driver to the UL coil. 

The arrangement consists of a short custom ribbon cable with female DB25 connectors on both ends - the particular wire sending the signal to the UL coil has a 100 ohm resistor wired in series, because the coil has resistance ~20ohm, and the output of the coil driver board has a series 200(?) ohm resistor, so by directly monitoring the voltage at this point, we may not see a glitch as it may register too small. Tangentially related: the schematic of the coil driver board suggests that the buffered output monitor has a gain of 0.5. 

To monitor the voltage, I use the board to which the 4 Oplev signals are currently hooked up. Channel 7 on this particular board (corresponding to ADC channel 30 on c1scx) was conveniently wired up for some prior test, so I used this channel. Then, I modified the C1SCX model to add a testpoint to monitor the output of this ADC. Then, I turned OFF the input on the coil output filter for the UL Coil (i.e. C1:SUS-ETMX_ULCOIL_SW1) so that we can send a known, controlled signal to the UL Coil by means of awggui. Next, I added an excitation at 5 Hz, amplitude 20 counts (as the signal to the coil under normal conditions was approximately of this amplitude) to the excitation channel of the same filter module, which is the state I am leaving the setup in for the night. I have confirmed that I see this 5Hz oscillation on the monitor channel I set up. Oddly, the 0 crossings of the oscillations happen at approximately -1000 counts and not at 0 counts. I wonder where this offset is coming from? The two points I am monitoring the voltage across is shown in the attached photograph - the black clip is connected to the lead carrying the return signal from the coil.

I also wanted to set up a math block in the model itself that monitors, in addition to the raw ADC channel, a copy from which the known applied signal has been cancelled, as presumably a glitch would be more obvious in such a record. However, I was unable to access the excitation channel to the ULCOIL filter from within the SCX model. So I am just recording the raw output for tonight...

Attachment 1: image.jpeg
  12248   Wed Jul 6 08:34:00 2016 SteveUpdateVACRGA scan at day 639

The last RGA scan of this pumpdown 78

Pressure plot of 640 days long pd 78

CC1 cold cathode gauge was jump started with an accidental pressure glitch, that you can see on P1 plot


Attachment 1: RGAscan639d.png
Attachment 2: pd78d640.png
  12249   Wed Jul 6 09:34:26 2016 SteveUpdateGeneralPRM sensing voltage LR

Yesterday Q noticed that PRM_sensor_LR was 0.098V  This actually went to ~ zero on 7-3


Attachment 1: PRM_LR.png
  12250   Wed Jul 6 10:58:07 2016 SteveUpdateVACvent 78 valve configuration

Vacuum Status: Chamber Open

All chamber annuloses are vented.  Vac Monitor screen is not communicating with gauges. The valve position indicator are working.

RGA is pumped by Maglev through VM2


Attachment 1: CamberOpen.png
  12251   Wed Jul 6 10:58:29 2016 VarunUpdateCDSDAFI review

The DAFI block was reviewed by Rana yesterday. The following changes/improvements were suggested: (Updated on 20th July 2016 with tasks taat remain in red)

1) include all the various channels like PEM, LSC, ASC, SUS, SEI, etc. as the inputs. Currently the inputs are only the LSC.
2) include all the control signals.
3) create a very detailed diagram of the entire signal flow and plan tasks accordingly.
4) Enable cascading of various DSP processes.
5) Adjusting the gain of the AGC such that the amplitude of the output signal comes to about half the peak amplitude offered by the ADC. This will help taking advantage of the entire dynamic range of the ADC.
6) change the enable button styles from a text input based controller to a button controller.
7) Currently, disabling a particular signal terminates the signal. Instead, it should turn into a unity gain block on disabling.
8) Check if the Fibox does AC coupling or not. If not, add an AC coupling arrangement in the DAFI.
9) Check the nature of the ADC1 and ADC2 inputs to the DAFI. I checked them yesterday, and they are channels 25 and 26 of ADC0, which are empty.

  12252   Wed Jul 6 11:02:41 2016 PrafulUpdateComputer Scripts / ProgramsVMon Tab on Summary Pages

I've added a new tab for VMon under the SUS parent tab. I'm still working out the scale and units, but let me know if you think this is a useful addition. Here's a link to my summary page that has this tab: https://ldas-jobs.ligo.caltech.edu/~praful.vasireddy/1151193617-1151193917/sus/vmon/

I'll have another tab with VMon BLRMS up soon.

Also, the main summary pages should be back online soon after Max fixed a bug. I'll try to add the SUS/VMon tab to the main pages as well.

  12253   Wed Jul 6 16:40:09 2016 AakashUpdateGeneralSeismometer Enclosure Development | SURF 2016

I am using AD592CNZ temperature transducer ICs for measuring temperature inside as well as outside the enclosure. It is a  current output IC which outputs current proportional to temperature. As mentioned in the data sheet of AD592, I am using the following two schematics:


Though I still need to calibrate these temperature transducers, I did some measurements. I have temperature readings, and now my goal in few days is to find a transfer function of temperature fluctuations inside the enclosure to outside the enclosure.


About data acquisition:

We have re-configured the raspberry pi(B8:27:EB:70:D0:D8) on martian network. It's new ip address is Also, we have added the Acromag Busworks card(00:01:C3:00:9F:C8) on the martian network and its ip address is   

  12254   Wed Jul 6 17:17:22 2016 PrafulUpdateComputer Scripts / ProgramsNew Tabs and Working Summary Pages

The main C1 summary pages are back online now thanks to Max and Duncan, with a gap in pages from June 8th to July 4th. Also, I've added my new VMon and Sensors tabs to the SUS parent tab on the main pages. These new tabs are now up and running on the July 7th summary page.

Here's a link to the main nodus pages with the new tabs: https://nodus.ligo.caltech.edu:30889/detcharsummary/day/20160707/sus/vmon/

And another to my ldas page with the tabs implemented: https://ldas-jobs.ligo.caltech.edu/~praful.vasireddy/1150848017-1150848317/sus/vmon/

Let me know if you have any suggestions or see anything wrong with these additions, I'm still working on getting the scales to be right for all graphs.

  12255   Wed Jul 6 19:36:45 2016 KojiUpdateGeneralSUS Vmon

I wanted to know what this Vmon exactly is. D010001 is telling us that the Vmon channels are HPFed with fc=30Hz (Attachment 1). Is this true?

I checked the quiscent noise spectrum of the ITMX UL coil output (C1:SUS-ITMX_ULCOIL_OUT) and the corresponding VMON (C1:SUS-ITMX_ULVmon). (Attachment 2 Ref curves). I did not find any good coherence. So the nominal quiscent Vmon output is carrying no useful information. 

Question: How much do we need to excite the coil output in order to see any meaningful signal?

As I excite the ITMX UL coil (C1:SUS-ITMX_ULCOIL_EXC) with uniform noise of 100-300 counts below 0.3Hz, I eventually could see the increase of the power spectrum and the coherence (Attachment 2). Below 0.1 Hz the coherence was ~1 and the transfer function was measured to be -75dB and flat. But wait, why is the transfer function flat?

In fact, if I inject broadband noise to the coil, I could increase the coil output and Vmon at the same time without gaining the coherence. (Attachment 3). After some more investigation, I suspect that this HPF is diabled (= bypassed) and aliasing of the high freq signal is causing the noise in Vmon.

In order to check this hypothesis, we need to visit the board.

Attachment 1: HPF.png
Attachment 2: 160706_ITMX_VMON2.pdf
Attachment 3: 160706_ITMX_VMON1.pdf
  12256   Wed Jul 6 20:51:00 2016 KojiUpdateGeneralSeismometer Enclosure Development | SURF 2016

Circuit1: It is nice to receive the voltage across the transimpedance resistor with a high impedance buffer (or amplifier), as close to the resister as possible. This amplifier needs to have low numbers for input bias current, input offset current, and input current noise. These current noise becomes the noise of the temperature reading. On the top of that, the input voltage noise of the buffer will be added to the output. The typical noise model can be found in http://www.analog.com/media/en/technical-documentation/application-notes/AN-940.pdf

The good candidates for the buffer is LT1128, ADA4004, OPA140, and LT1012. If the application is not too sensitive to the total noise, OPA604 is a good choise with easier handling.

Circuit2: With the same reason, AD741 is an old generic amp that is not a great choise for this purpose. The current noise is more significant because of the higher transimpedance here. The same noise model as above can be used to analyze the performance.

  12257   Wed Jul 6 21:05:36 2016 KojiUpdateComputer Scripts / ProgramsNew Tabs and Working Summary Pages

I started to receive emails from cron every 15min. Is the email related to this? And is it normal? I never received these cron emails before when the sum-page was running.

Attachment 1: cron_mail.txt.zip
  12258   Wed Jul 6 21:09:09 2016 not KojiUpdateComputer Scripts / ProgramsNew Tabs and Working Summary Pages

I don't know much about how the cron job runs, I'll forward this to Max.


I started to receive emails from cron every 15min. Is the email related to this? And is it normal? I never received these cron emails before when the sum-page was running.

Max says it should be fixed now. Have the emails stopped?

  12259   Wed Jul 6 21:16:17 2016 Max IsiUpdateComputer Scripts / ProgramsNew Tabs and Working Summary Pages

This should be fixed now—apologies for the spam.


I don't know much about how the cron job runs, I'll forward this to Max.


I started to receive emails from cron every 15min. Is the email related to this? And is it normal? I never received these cron emails before when the sum-page was running.



  12260   Wed Jul 6 21:50:21 2016 KojiUpdateComputer Scripts / ProgramsNew Tabs and Working Summary Pages

It seemed something has been done. And I got cron emails.
Then, it seemed something has been done. And the emails stopped.

  12261   Wed Jul 6 22:58:01 2016 gautamUpdateGeneralVent progress - ETMX SUS Coil driver electronics investigation

I've made a few changes to the monitoring setup in the hope we catch a glitch in the DAC output/ sus coil driver electronics. Summary of important changes:

  1. I'm using a CDS oscillator to send a signal of 20counts amplitude, 5.0 Hz to the coil rather than an excitation point. This way, I have access to the known signal we are sending, and can subtract it from the measured signal. 
  2. To account for the phase delay between the excitation from the oscillator to the measured excitation, I am using an all-pass filter to manually delay the oscillator signal (internally in the model) before subtracting it from the measured output.

It remains to see if we will actually be able to see the glitch in long stretches of data - it is unclear to me how big a glitch will be in terms of ADC counts.

The relevant channels are : C1:SCX-UL_DIFF_MON and C1:SCX-UL_DIFF_MON_EPICS (pardon the naming conventions as the setup is only temporary after all). Both these should be hovering around 0 in the absence of any glitching. The noise in the measured signal seems to be around 2 ADC counts. I am leaving this as is overnight, hopefully the ETMX coil drive signal chain obliges and gives us some conclusive evidence...

I have not committed any of the model changes to the SVN. 

  12262   Wed Jul 6 23:01:03 2016 gautamUpdateGeneralpianosa monitor dead

One of the pianosa monitors has ceased to function frown For now, it has been set up to operate with just the one monitor.

One of Donatella's monitors has a defective display as well. Maybe we should source some replacements. Koji has said we will talk to Larry Wallace about this..

  12263   Thu Jul 7 00:25:07 2016 ericqUpdateGeneralVent progress - ETMX SUS Coil driver electronics investigation

It may be advantageous to look at the coil output data from when the OSEM damping is on, to try and reproduce the real output signal amplitude that gets sent to the coils.

  12264   Thu Jul 7 09:13:54 2016 SteveUpdateSUSSOS gluing fixture

Atm 1, It's right arm is perfect.

Atm 3-4, The left one has bended (dropped) end.

Atm 2, Our ruby wire stanoffs will fit the jig. Ruby OD 1.27 mm vs. old Aluminum OD 1.0 mm. Length ruby 6.4 mm vs Al 4.8 mm

Atm 5, The fixture translation stages are a bit loooose. Careful use of the micrometer is needed to be precise

Betsy agreed that the 40m will keep SOS fixtures.

Attachment 1: SOSgluingFixRarmWend.jpg
Attachment 2: SOSgluingFixRarm.jpg
Attachment 3: SOSgluingFixLarm45.jpg
Attachment 4: SOSgluingFixLarm.jpg
Attachment 5: SOSgluingFixture.jpg
  12265   Thu Jul 7 10:49:03 2016 gautamUpdateGeneralVent progress - ETMX SUS Coil driver electronics investigation

It may be advantageous to look at the coil output data from when the OSEM damping is on, to try and reproduce the real output signal amplitude that gets sent to the coils.

The amplitude of the applied signal (20) was indeed chosen to roughly match what goes to the coils normally when the OSEM damping is on.

There appears to be no evidence of a detectable glitch in the last 10 hours or so (see attachment #1 - of course this is a 16Hz channel and the full data is yet to be looked at)... I guess the verdict on this is still inconclusive.

Attachment 1: UL_glitchMon_Striptool.png
  12266   Thu Jul 7 12:44:52 2016 varunUpdateCDSDAFI update

Attached is a diagram, showing the entire (planned) signal flow of the DAF model. Some thoughts on the implementation after discussion with eric:

1) Since the LSC control signals and ASC signals are running on the c1lsc FE at the same rate as DAFI (16kHz), it would be wise to start from these.

   Current implementation: has a matrix at the end of the LSC PD signals, which selects one of the PD signals and outputs it to the DAFI via IPC communication.

    Proposed Changes: Add another matrix at the end of the LSC PD signals, to give to the second stereo output. Similarly, add two matrices each at the end of the LSC control signals and     the ASC signals. Each matrix must select one of the signals and output it to the DAF via IPC.

2) The PEM running on the c1sus FE system will have to be brought to DAFI in a similar fashon. However, since c1sus runs at 2kHz, there is a possibility of imaging while the signal is    transfered to the DAFI. This could be taken care of by an anti imaging filter, or inserting zeros between two samples coming at to the 16 kHz system from the 2kHz system and then low-passing it to remove the aliased parts. (similar to upsampling)

3) For the SUS control signals, input can be given from a matrix prepared for each optic seperately.

Attachment 1: DAFI.pdf
ELOG V3.1.3-