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  12283   Sun Jul 10 15:38:01 2016 ericqUpdateGeneralETMX in guiderod/standoff gluing fixture

I was hoping to glue a standoff and guide rod today, but some problems have reared their heads. Story follows:

Upon first placng the optic into the standoff gluing fixture, I was presented with a geometric problem. In the assembly procedure, one glues the rods before the magnets, which prevents a situation like this:

When what you want to do is this:

So, I spun the optic around such that the magnet is on the far side of the scribe line from the side arm, and instead of extending the side arm past the scribe line, will bring it back towards the near side. I also swapped the arms of the fixture such that the guide rod will be glued on the opposite side of the optic than the side magnet, so the side magnet won't get in the way when doing the pitch adjustment of the second standoff.

Then, I found the scribed ruby rods, and took a look at one under a microscope. The groove looks nice and sharp. I placed the standoff in the side arm of the fixture.

However, the fact that the groove does not go all the way around the standoff leads to problem #1: when adjusting the position of the side arm, the standoff seems to roll around unpredictably, making it hard to deterministically position it while keeping the groove facing outwards. 

Problem #2 is not too surprising give Steve's finding about the guide rod holding arm in ELOG 12264. Given that the tip is banged up, the guide rod does not sit straight in the arm, making it crooked. This would lead to the second standoff's groove not being well aligned to the suspension wire.

I will meditate on solutions to these problems... I have covered the optic and fixture with the same foil hut Koji made on Friday.


Also, I peeked at the aluminum standoffs under the microscope. Since the groove goes all the way around, we don't really know where the wire was seated before. Still, there are some places where the groove looks kind of worn:

  12284   Sun Jul 10 15:54:23 2016 ericqUpdateCDSAll models restarted

For some reason, all of the non-IOP models on the vertex frontends had crashed.

To get all of the bits green, I ended up restarting all models on all frontends. (This means Gautam's coil tests have been interrupted.)

  12285   Sun Jul 10 17:33:00 2016 ericqUpdateGeneralVent progress

It took a little time, but I relocked the IMC and realigned to the point where the PRC is flashing, visible on REFL and AS, and tiny flashes are visible in TRY.

  12286   Sun Jul 10 18:20:39 2016 ranaUpdateElectronicsAntialiasing Filter Update

Comments on the schematic:

  1. Only the instrumentation amp should be made up of the ADA4004. Not the whitening parts.
  2. Please think about the front panel design and make a drawing of the front and back panels. Power connectors, indicators, switches, etc. Take a look at some of our existing 1U rack electronics to see what standard arrangements are. Add a front and back panel drawing to the elog.
  3. The whitening and anti-aliasing opamps can all be OP27 SOIC-8 for now. Later, if we need better noise performance or speed we can use faster opamps.
  4. There should be a 3rd stage of AA. Each of the exisitng stages (U5, U6) can only be second order and we want the option to have a 6th order low pass.
  5. There should be 100 nF decoupling capacitors on the power pins of all the single opamps.
  6. There is a low noise power daugther board made by Ben Abbott which you can use on the DCC. It should accept the direct power connector from the back panel and supply regulated power to the board.
  7. Take care to update the lower right hand corner info box with updated drawing version #'s and author name.
  8. The MAX4158 is 16 years old. It may be good if you can find a newer parts so it doesn't go obsolete.
  9. All of the R & C on the board should be sized 1206 for the SMD.
  10. For the whitening and AA filtering stages, we want the capability to use larger size parts (e.g. the red WIMA caps that are in the blue spinny box). So you will have to use larger footprints for those.
  11. The resistors should all be 0.1% thin film or metal film.
  12287   Sun Jul 10 20:08:44 2016 varunUpdateCDSDAFI Update: Changes in LSC and PEM models

I have added the PEM signals mentioned in the previous elog as DAF inputs through PCIE IPC, and compiled and restarted the c1pem and c1daf models. 

Attached are the pictures of the simulink diagram of the addition in the PEM and the DAF. 

Since the signals are moving from a 2kHz clock rate machine to a 16kHz clock rate machine, some imaging effects are possible, which I have to look into.

  12289   Mon Jul 11 15:13:22 2016 gautamUpdateGeneralVent progress: in-date First Contact procured

I have obtained 2x100cc bottles of in-date first contact from Garilynn (use before date is 09/14/2016) for cleaning of our test-masses. They are presently wrapped in foil in the plastic box with all the other first contact supplies.

  12290   Tue Jul 12 09:18:12 2016 ericqUpdateGeneralSlippery substance mystery

I found a note on Steve's desk that R. Abbott left yesterday afternoon about an unidentified slippery substance being present on the floor by cabinet S12, along the X arm. (Steve is away this week)

Just now, I found no trace of the substance in the vicinity of that cabinent (which is one of the cabinets for clean objects). Maybe the janitor cleaned it already?

  12291   Tue Jul 12 09:35:51 2016 JohannesUpdateGeneralSlippery substance mystery

I've noticed the spot that Rich means before, too. I think you only notice this when you're wearing the shoe covers, not sneakers or crocs. I didn't see any 'substance', it seems more like the floor finish (wax?) seems to be more slippery in that area than others.

Quote:

I found a note on Steve's desk that R. Abbott left yesterday afternoon about an unidentified slippery substance being present on the floor by cabinet S12, along the X arm. (Steve is away this week)

Just now, I found no trace of the substance in the vicinity of that cabinent (which is one of the cabinets for clean objects). Maybe the janitor cleaned it already?

 

  12292   Tue Jul 12 16:08:00 2016 ericqUpdateGeneralETMX ruby guided gluing

[ericq, Koji]

We have positioned and applied epoxy to one ruby standoff on ETMX, for overnight curing according to the SOS standoff gluing procedure. This included:

  • Removing and reinserting the guiderod until the groove is properly oriented, as seen by microscope
  • finding the right vertical offset with the microscope + 3 axis micrometer stage
  • axial centering by equalizing the distances from the grove to each bevelled edge of the barrel with the microscope stage
  • mixing epoxy
  • Testing the mix by putting some drops on some foil, and putting that in a 200F oven for 15 minutes, and checking that it cured well
  • Applying some tiny droplets of expoxy using the tip of some copper wire, making an effort to keep epoxy away from the glue

Instead of trying to fix up a way of gluing the guiderod with the proper alignment, we chose to be more conservative and glue the standoff today, then switch the gluing fixture's arms tomorrow to glue the guide rod with the good fixture arm. 

Additionally, we chose to glue one of the more assymetric standoffs on this first side. What I mean by this is: We have 3 ruby standoffs with grooves. Two of them have the groove about 1/8th of the way along their length, and one has it about 1/4 of the way. Since the second standoff is going to be glued while suspended, after pitch balancing, we figure that we want to use the more centered groove on that side, meaning we used one of the 1/8th standoffs today.

Unfortunately, we neglected to take any pictures :/

  12293   Tue Jul 12 18:13:19 2016 KojiUpdateVACN2 bottle replaced

Gautam, Koji

We replaced the right N2 bottle as it was empty.

  12294   Tue Jul 12 20:16:15 2016 LydiaUpdateGeneralITMX dust

Looked at ITMX. Johannes and I both saw a fairly large speck of dust near the center of the HR side. We tried to take some photos but couldn't get any with good focus. 

  12295   Tue Jul 12 23:51:16 2016 JohannesUpdateGeneralVent progress - ETMY inspection

On Monday I inspected ETMY, and found nothing really remarkable. There was only little dust on the HR side, and nothing visible in the center. The AR side has some visible dust, nothing too crazy, but some of it near the center.

  12296   Wed Jul 13 00:01:38 2016 JohannesUpdateGeneralITMX dust

We ran out of illuminator juice, and short-term charging couldn't restore enough battery life to continue the work. We should be able to get some better pictures tomorrow.

Quote:

Looked at ITMX. Johannes and I both saw a fairly large speck of dust near the center of the HR side. We tried to take some photos but couldn't get any with good focus

 

  12297   Wed Jul 13 00:38:25 2016 JohannesUpdateGeneralVent progress - ETMY attempted repositioning

[Lydia, Johannes]

We attempted to move the ETMY suspension near the access port in preparation for the cleaning process. The plan was to move in the face restraints first to the point of almost making contact, then the ones underneath so the optic is sitting on them, followed by the top one facing down, and then bringing in the stops on the faces.

While moving in the stoppers I noticed that the far lower stopper on the HR side was barely touching the face of the optic in its resting position and was basically pushing it sideways when moved forward. It was just on the edge, so I tried to compensate minimally by moving the underneath stops a little further on the near side, trying to let it 'slide' over a little so the screw would have better contact. I must have been too generous with the adjustment, because while proceeding I noticed at some point that the stick magnets on one side of the optic were not attached anymore but laying inside the OSEMs. The side magnet was also missing, it is now sitting on the suspension jig base plate. The dumbbells all seem intact, but we'll test them before we reglue the magnets to the optic. This is extremely unfortunate, but hopefully won't take too long to fix. At the very least, as Koji put it, the cleaning will be easier with the optic out of the suspension. Still, what a bummer.

  12298   Wed Jul 13 03:16:47 2016 KojiUpdateGeneralITMX dust

Multicolor flash light:

- It seems that the usb port charging doesn't work.

- There is a battery charger on Steve's desk. I set the batteries on it.

 

White LED flash light:

- I temporarily brought a compatible charger from WB. It's charging two batteries behind the LCD display on my desk.

 

  12299   Wed Jul 13 15:35:56 2016 LydiaUpdateGeneralVent Progress - ETMY repositioned and removed

[Lydia, Johannes]

Took photos to document the original OSEM orientation and wrote down the serial numbers for each position. We removed the OSEMs, moved the suspension to the accessible side of the table and took out the optic, which was brought to the clean room to have the magnets reglued. The ETMY chamber is now closed up with the OSEMs and clamps inside on the table, and should not need to be reopened until the magnets have been reattached. 

  12300   Wed Jul 13 21:13:51 2016 KojiUpdateGeneralETMX guide rod gluing / ETMY Magnet gluing

[Eric, Koji]

  • ETMX: The Al guide rod has been glued on the mirror.
  • ETMY: The UR, LR, and SD magnets have been glued on the mirror.
  • For both, we are waiting for the glue getting cured.

Handing over message to the next step

  • ETMX: The arm of the fixture has probably been glued together with the guide rod. It has to be taken care when the fixture is removed.
    (See
    ETMX gluing section and Attachment 13)

ETMX: guide rod gluing (done) -> fixture unmounting side -> fixture setting -> magnet gluing -> suspend -> pitch balance -> ruby gluing -> air bake
ETMY: magnet (done) -> fixture unmounting -> air bake


ETMY gluing

Mirror transport:
- A transport setup was made with a donut holder for a 3" optic, glass jar, stain less tray, and a CS Stat zipbag. (Attachment 1)

Shimming:
- The magnets have been glued witht the gluing fixture. (Attachment 2)
- We checked the dimensions of the glued magnet and found that the thicker side has to be raised by 1mm. (We used the fact that the relative distance between the wire groove and the magnet is always the same.)
- The ETMs have 2.5deg wedge and this corresponds to 3.2mm height difference between the left and right edges. This meant that the thinner side had to be raised by 4.2mm.
- We used a 0.9mm Teflon sheet for the thicker side (Attachment 3) and two 2.2mm Teflon pieces for the thinner side (Attachment 4). For stabilization of the fixture, two Teflon tubes with a diameter of ~3mm are inserted to the top and bottom side of the mirror (Attachment 5).

Magnet orientation:
- Mirror orientation in the fixture (Attachment 6).
- It was confirmed that existing UR, LR, and Right SD magnets have the polarity of N facing out, S facing out, and N facing out. And we confirmed that this is consistent with ETMX and the procedure document (E970037)
- Along with the procedure document, we arranged the magnet-dumbbells UL, LL, and Left SD magnets to have S-out, N-out, and N-out. (Attachments 7, 8, and 9)

Gluing:
- In prior to gluing, all three dumbbells surfaces were cleaned by acetone and razor blade scrubbing.
- After the epoxy curing test (see below), the three magnet-dumbbell pairs have been glued on the mirror. A single dub of EP30-2 was applied to each dumbbell surface.

- Attachments 10, 11, and 12 shows how glue is spread at each joint.

ETMX gluing

Guide rod positioning:
- The longitudinal position of the guide rod was adjusted using the micrometer microscope such that it located at the center of the mirror thickness.
- The guide rod is not long enough to have the edges sticking out from the form of the fixture arm. Therefore only arm finger of the arm held the guide rod. 
- The height was adjusted to be 1.73mm (68mil) lower than the mirror scribe line. The mirror is fixed on the fixture upside down. So this bonds the guide rod above the scribe line.

Gluing:
- Then the epoxy was applied to the guide rod. The glue was applied to two edges of the rod, but capillary action spread the glue around the rod. It seemed that the fixture and the rod were connected with the glue. Care should be taken when the fixture is going to be removed. (Attachment 13)
- The top side (in the picture) where the stand-off will come is still relatively kept clean. So it must be OK for the stand off. If there is an issue, we can shave the epoxy with a razor blade.

Glue testing

- EP30-2 tends to fail to get cured. In order to check the mixture is properly made or not, we put a test piece into air bake oven.
- The procedure says, 200F 15min bake show if the glue is in a good shape or not.

- We have the temperature sensor setup on a air bake oven, but it seemed that the indicated temperature there is overestimate.
  The heating setting of 2 was enough to show the temp of 100degC although EP30-2 didn't get cured with this setting.

- Our experience says that heater setting of "5" makes the temperature ~90degC. On July 12nd, this setting showed the temp of 90degC. Today (July 13rd) it didn't. In the both cases, the epoxy got cured nicely. So we should use this setting.

  12301   Thu Jul 14 01:00:33 2016 KojiUpdateGeneralETMX ruby guided gluing

Today I took the picture of the glued ruby stand-off. The groove has not been invaded by the epoxy!

  12302   Thu Jul 14 22:29:57 2016 ericq UpdateGeneralETMX guide rod gluing / ETMY Magnet gluing

The pickle puckers came off ETMY cleanly yes ETMY now rests in the ring holder, under a glass jar, with all of its magnets.

We removed the guiderod gluing fixture from ETMX without any apparent damage to the fixture arm, optic, or guiderod epoxy joint. 

I started measuring some distances on the optic for the side magnet gluing, but am not sure of it yet. So, I didn't manage to start the gluing today. 

  12303   Thu Jul 14 23:38:59 2016 varunUpdateCDSc1lsc FE unresponsive

Today, at around 10:30, c1lsc machine froze and stopped responding to ping and ssh after I compiled and restarted c1daf. I think it is due to a large array in one of my codes. The daqd.log file shows the following:


..................................................................
CA.Client.Exception...............................................
    Warning: "Virtual circuit unresponsive"
    Context: "c1lsc.martian.113.168.192.in-addr.arpa:5064"
    Source File: ../tcpiiu.cpp line 945
    Current Time: Thu Jul 14 2016 22:27:42.102649102
..................................................................

I think the c1lsc FE may need a hard reboot.

  12304   Fri Jul 15 12:21:28 2016 varunUpdateCDSc1lsc FE unresponsive

c1lsc is up and running, Eric did a manual reboot today.

Quote:

Today, at around 10:30, c1lsc machine froze and stopped responding to ping and ssh after I compiled and restarted c1daf. I think it is due to a large array in one of my codes. The daqd.log file shows the following:


..................................................................
CA.Client.Exception...............................................
    Warning: "Virtual circuit unresponsive"
    Context: "c1lsc.martian.113.168.192.in-addr.arpa:5064"
    Source File: ../tcpiiu.cpp line 945
    Current Time: Thu Jul 14 2016 22:27:42.102649102
..................................................................

I think the c1lsc FE may need a hard reboot.

 

  12305   Fri Jul 15 16:23:51 2016 ericq UpdateGeneralGluing setbacks

[ericq, Lydia]

Here is a picture of the ETMX guide rod post-gluing. There is unfortunately a fair amount of excess. The "tab" is the result from the epoxy travelling along the finger of the fixture arm that held the guide rod.

We set out to glue the previously remove ETMX side magnet, and set up the fixture to do so. For ETMX we needed 3 mm of shimming on the thick side, and 6mm on the thin side.

However, while cleaning the magnet+dumbbell base of epoxy residue, I broke the dumbbell off of the magnet no

We then fetched the spare side magnet that Steve had been holding onto. While cleaning it, it was dropped and dissapeared from this plane of existence nono

So, instead of gluing a side magnet today, we are gluing the existing magnet and dumbbell back together:

Sadly, this used up the last of our EP30.nonono

Though Koji had the foresight to order more(yes), it will not arrive until Monday/Tuesday, so no side magnet gluing until then.frown

  12306   Fri Jul 15 17:44:37 2016 AakashSummaryGeneralAcromag Setup | SURF2016

Aidan has described the physical connections and initial setup here :  https://nodus.ligo.caltech.edu:30889/ATFWiki/doku.php?id=main:resources:computing:acromag#recovering_from_a_terminal_power_communication_outage  .

Since I used a Raspberry Pi(domenica.martian) for communicating to Acromag(acroey.martian) card, I had to recompile everything for linux-arm architecture. 

For EPICS installation, download the EPICS base from http://www.aps.anl.gov/epics/download/base/baseR3.14.12.3.tar.gz . Installing dependencies, build, install epics at /usr/local/epics. By downloading modbusApp source from https://llocds.ligo-la.caltech.edu/daq/software/source/epics-3.14.12.2_long-source.tar.gz  , build the modbusApp for linux-arm architecture in modules/modbus directory inside epics base.

Put all the files mentioned by Aidan and run a tmux session to grab channels.

Also, pyModbus can be used to read the channels. I'll put the physical connections schematic shortly.

  12307   Sat Jul 16 00:30:42 2016 varunUpdateCDSDAFI update: Frequency warping | c1lsc unresponsive

Summary: I am trying to implement frequency warping/pitch shifting on the real time FE. Here is a description long overdue:

Description: The overall idea is as follows:

The DFT of a frame x_i[n]  is given by X_i[k] = \sum_{n=0}^{m-1}x_i[n]e^{-j2\pi \frac{kn}{m}}. A matrix W containing all W_{kn} = e^{-j2\pi \frac{kn}{m}} for k, n = 1, 2, ..., m can be calculated and predefined in the code. The input arrival rate is 16384 Hz, i.e. once in every 60 $\mu$s time window. Hence, the fourier coefficients can be updated cumulatively in each cycle using the current value of the input, previous value of the fourier coefficient and the components of the W matrix. This will distribute the computational load of the FFT into all the time windows. Similar operations can be carried out for the inverse STFT.

I have written and run a pseudo-real time code on my CPU. The following is the essence:
 Let the frame-length be M, and the intended scale factor of the frequency warping be 'r'. The frame overlap is 50%. At each clock cycle, the following tasks are performed:  (1 to 3 are routine tasks performed at every clock cycle, 4 is a special task performed only when a frame is filled.)
 1) Take input and apply hanning window to it.
 2) Cumulate X_i[k] for every k using the value of x_i[n] (the input) at that particular instant. Also start to cumulate X_{i+1}[k], which will be later transfered to X_i[k].
 3) Because of 4), we now have 'r+1' filled frames corresponding to output fft. Now take the ifft using two consecutive frames corresponding to only two time series points. The computations required for this task are the same as the computations required for calculation of the fourier coefficients iteratively, since the entire time series ifft is not computed.
 4) Do these special tasks after each frame gets filled:
      At this point, the ffts of the current frame and a previous frame is ready. Let us call them X1 and X2.
      Calculate phase difference between the two.
      Calculate all the interpolated |Y_i| in between these two frames depending upon the scale factor.
      Assign phase of X1 to first Y frame and assign increasing phase to all the other Y frames.
      and also do all the usual non-special tasks.

This code takes about 9-10 microseconds for a cycle with special tasks, and 5-6 microseconds for a cycle with routine tasks on my laptop (brought down from 100 microseconds peak time in the earlier offline implementation due to elemination of explicit dft and reduction in fft size), for a frame size of 32 samples. However, when fed into the c1lsc FE, it crashes, as it has done once again today evening, in the same fashon as yesterday. There could be 2 possible reasons:

1) Size of the array containing the W_{kn} matrix elements is too large for the FE memory,

2) the computations are taking up more than 60 microseconds.

Since there are already a few codes with similar array sizes, I am more inclined to think that 2) is more likely.

Another problem that I am anticipating is that for a 32 point dft and a sampling rate of 16kHz, the frequency resolution achieved is about 500 Hz, which is not sufficient if we need to represent seismic signals. The only way I can think of, for representing such signals with a small number of fft points, is to reduce the effective sampling rate, i.e. do DSP on inputs at a much lower rate than 16kHz (say 1kHz, which will give a resolution of ~30 Hz, or 2kHz giving a resolution of ~60Hz). Another advantage of this method is that it frees up more clock cycles for computation, thus the computational load can be further distributed.  The problem in this implementation is that it will increase the delays.

  12308   Mon Jul 18 05:05:05 2016 AakashUpdateGeneralHeater for Seismometer Enclosure | SURF 2016

I took off the silicon rubber heaters which were used by a SURF last year for heating the enclosure. The heater data sheet has mentioned the power dentsities, but I doubted the values. So I wanted to measure the actual power density by these heaters. I think the rubber heaters are broken somewhere within, the surface is not heated evenly. Although I don't have a good quantative reason to use, I was thinking to use a thermoelectric cooling module for the enclosure. 

From the data I collected few days back, I am trying to obtain a transfer function of temperature inside the enclosure to that of outside. My aim is to measure the pole frequency of temperature fluctuations inside the enclosure relative to the outside fluctuations.

 

  12309   Mon Jul 18 18:44:52 2016 varunUpdateCDSc1lsc FE recovered

c1lsc FE is up and running.

Details:

2) The machine was manually rebooted.

3) c1daf was recompiled and installed, with the problematic piece of code removed.

4) NTP timing was adjusted.

5) Frame Builder was restarted.

6) All models on c1lsc machine were restarted.

Attachment 1 shows the CDS status after the recovery. I wont be trying to run frequency warping immediately, I will first finish implementing the other harmless modules first.

  12310   Tue Jul 19 13:21:42 2016 JohannesUpdateGeneralVent progress - ETMY attempted repositioning

[Lydia, Johannes]

We moved ITMY from its original position to a place near the access point. We took the OSEMs off first, and noticed that the short flat head screw driver was still a little too long to properly reach the set screws for the lower OSEMs. We were able to gradually loosen them, though and thus remove the lower OSEMs as well. We had to move a cable tower out of the way, but used clamps to mark its position. After making sure the optic is held by its earthquake stops, we moved it to its cleaning location. All magnets are still attached.

  12311   Tue Jul 19 15:16:43 2016 SteveUpdatesafetysafety training

Our new graduate student Lydia received 40m specific safety training.

  12312   Tue Jul 19 15:30:08 2016 SteveUpdateGeneralHEPA dryer and dust

I set up a simple HEPA filter dryer to dry your clean room garment before  you can put it away into your storage box.

Our lab is dusty ! This is  specially important when we are vented. Please wipe things daily and cover item with foils .... etc.

  12313   Tue Jul 19 16:39:29 2016 LydiaUpdateGeneralETMX magnet gluing/guiderod excess glue removed

[ericq, Lydia]

The epoxy arrived. Eric managed to remove the excess glue below the guiderod with a razor blade (see attachment 1). The magnet and dumbell that came apart were reglued successfully and passed the stregth test of picking up the magnet from the table by the dumbell, so the magnet was glued back on the optic and is setting in the gluing apparatus (see attachment 2).

We double checked the polarity against the side magnets on ETMY. Because of the gluing position strategy (a fixed distance toward the HR side from the groove location), the other side magnet appears slightly below the center of the gluing barrel, which after some discussion with Koji was determined to be ok. 

  12314   Wed Jul 20 11:39:07 2016 SteveUpdateVACvent 78 day 20

RGA background scan

Quote:

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

 

 

  12315   Wed Jul 20 13:58:55 2016 SteveUpdateSUSSUS damping out of vac chamber

Cheater cable to be used in clean room pitch gluing alingment.

Satelite amp needs to be there.

Atm 2-3, The ETMs  suspension damping cable  are connected at the end racks. All others go to 1X5

Atm 4-5, The other end of this cable in the high cable tray at 1X3 as shown. We'll disconnect the shorty and move the end to ETMX ( or any sus at 1X5 )

 

  12316   Wed Jul 20 14:03:01 2016 ericqUpdateSUSEffect of thicker ruby standoffs

The new ETMX ruby guide rods are slightly thicker than the old aluminum ones; specifically 1.27mm vs 1.0mm.

Since we did not change the guide rod location in response to this fact, the vertical position of the suspension point changes, which in turn changes the dynamics of the suspension. Specifically, since the standoff is placed below the guide rod, the suspension point is lowered, which makes the pitch mode softer. I crunched a few numbers and have determined that this effect should not be a problem.

Given the wiki's value of the ETMX pitch resonance frequency of 0.829 Hz, I predict a the new pitch resonance frequency of 0.800 Hz.

(wiki link: https://wiki-40m.ligo.caltech.edu/Suspensions/Mechanical_Resonances)


A useful document about the dynamics of our suspension can be found at T000134

From this document, one will find that the effect of changing the suspension point height over the optic center of mass,`b`, on the pitch resonance frequency (while keeping all other dimensions equal) to be:

\frac{\omega'_\theta}{\omega_\theta} \approx \sqrt{\frac{b'}{b}}

The top of the standoff is fixed by the guide rod, so let's say that b' is given by the position of the center of the Ruby standoff. This is then smaller than the previous b by the differences in the radii of the standoffs:

b' = b - \frac{\oslash_{\textrm{ruby}}-\oslash_{\textrm{Al}}}{2}

The nominal value of b is 0.985mm. Thus, the pitch resonance frequency is changed by factor of 0.965, i.e. 3.5% smaller. Then, taking the wiki value of 0.829 Hz results in 0.800Hz, a 30mHz decrease.

  12317   Thu Jul 21 05:22:26 2016 AakashUpdateGeneralTemperature measurements across the enclosure | SURF 2016

I have measured the transfer function of temperature fluctuations inside the enclosure to that of the temperature fluctuations outside. The transfer function has been estimated by using 'tfestimate' which is library function in Matlab and which estimates the transfer function based on Welch's method. The attached plots shows the transfer function of the temperature inside the enclosure to that of outside temperature.

fig1.pdf

fig2.pdf

In order to determine a relation between temperature inside the enclosure to that of the outside temperature, I have calculated the mean squared coherence.  I have used Matlab's 'mscohere' library function which uses Welch's method to calculate the coherence. Attached plot shows the coherence between the temperature across the enclosure.

fig3.pdf

Also, I have attached the matlab script which I used for generating these plots.

script21jul2016.m

  12318   Thu Jul 21 08:24:20 2016 SteveUpdatePEMants alart

The heat drives the ants to the lab!  Make sure the light doors are tight on the chambers.

 

  12319   Thu Jul 21 12:03:35 2016 varunUpdateCDSDAFI update: Humming noise in DAFI output

 

Summary: There was always a constant humming noise in the output of speakers of both the audio channels. Tried to resolve the problem. Details are given below:

Details: The source of the noise was the typical 60 Hz (and harmonics), ~13 mV peak to peak output, in at least three channels of the DAC. (two coming from the DAF module, and one not related to the DAF.) Attachment 1 shows the noise in both the DAF channels. As compared to that, the signal coming through the AGC weak, about 6 mV RMS, about the same order as noise. In order to resolve this, the gain of the AGC was increased, so that the RMS output voltage of the Fibox (FBAO, the one at the output) was about 1.23 V RMS. It is approximately equal to +4 dBu, which is the typical expected output of the Fibox, according to the datasheet.

  12320   Thu Jul 21 14:27:24 2016 varunUpdateCDSDAFI Update: Arbitrary Math block

Summary: I have added an arbitrary math block to the DAFI model, which takes two inputs, say X and Y, and can perform various unary and binary operations on them:

Details:

  • Unary Operations:
  1. Delay - There exists a text-based input to specify the amount of delay to be given to a particular signal.
  2. sin()
  3. cos()
  • Binary Operations:
  1. Weighted addition and multiplication: The output is calculated according to the relation: A*X + B*Y + C*X*Y. A, B, C are constant inputs, which can be given through text-based inputs in the GUI.
  2. MAX{X,Y}
  3. MIN{X,Y}

Attachment 1 shows the existing DAFI gui, updated with cascading of various DSP blocks, upto three levels, button-based ENABLE and DISABLE controls for all blocks except arb. math (the control on arb. math. is achieved by clicking on the block.) On clicking the arb. math block one is taken to the dedicated arb. math screen, which has enable buttons for all the processes listed above. A screenshot of this screen is in attachment 2. There is one control input, which controls all the unary operations on X and the binary operations on X and Y, and another control input which controls the unary operations on Y. switching on a particular arb. math process gives a particular control input, which choses the appropriate section of the code. At a time, only one process from the top grey block (corresponding to unary operations on X and binary operations on X and Y) and one process from the bottom grey block (corresponding to unary operations on Y) can be selected. Thus, the outputs which go from the arb. math block to the intermediate matrices (MATRIX1L or MATRIX2L) are:

a) Either an output of unary operation on X or a binary operation on X and Y, the specific one depending upon the control input,

    and

b) Output of a unary operation on Y, again the specific one depending upon the control input

Thus there is apparent asymmetricity in the action of the arb. math block on the two inputs. However, this is done in order to reduce to total number of outputs and control signals, and this can be easily taken care of by interchanging the inputs before the block. 

While compiling this code, the c1lsc machine had crashed once, it was found that this was due to a stray "printf()" command in the c code. This glich in the code now stands rectified  There is a possibility that the previous incidents of the code crashing could also be due to the existence of a printf() command. 

Preliminary Testing: I have done a preliminary testing of the arb math block, i.e. verified that on enabling the sin and cos processes, the output is less that 1, on swithching on the process of weighted avarage and multiplication, the output looks like it is right, for a few simple values of A, B, C, like 0, 1, etc. The delay block however is giving zero output for delay of more than 6 samples.

 

 

 

 

  12321   Thu Jul 21 15:03:13 2016 varunUpdateCDSDAFI Update

1) I have added the status summary of the DAFI block to the main FE status overview screen in the c1lsc cloumn. (attachment 1)

2) I have edited all the kissel matrix buttons appropriately, and given them appropriate lables. (attachment 2)

  12322   Thu Jul 21 17:01:59 2016 ericqUpdateGeneralETMX magnet gluing/guiderod excess glue removed

One step forward, two steps back...

While attempting to suspend ETMX, I broke off a side magnet crying

It is now gluing

(This is *not* the one that was previously glued. I.e., now both ETMX side magnets have been reglued)

  12323   Thu Jul 21 21:38:44 2016 AakashUpdateGeneralTemperature measurements across the enclosure | SURF 2016

I have made the changes as suggested by Gautam.

  12324   Thu Jul 21 22:02:35 2016 varunUpdateCDSDAFI update: Frequency warping

The code for frequency warping contained a "printf()" command, which had caused the system to crash in one another instance (refer elog 12320) . Hence, I tried running the code tody by removing this line. Unfortunately, this did not work. the model still crashed. Attached is the screenshot of the FE status.

  12325   Fri Jul 22 03:02:37 2016 KojiUpdateCOCFC painting

[Koji Gautam]

We have worked on the FC painting on ITMX and ITMY. We also replaced the OSEM fixing screws with the ones with a hex knob.
This was done except for the SD OSEM as the new screw was not long enough. We left an allen-key version of the screw for the SD OSEM.

All the full-resolution photos can be found on g-photo.


ITMY

Attachment1: The barrel was pretty dusty. Some dusts were observed on the HR face but it was not so terrible. The barrel and the HR face were blown with the ionized N2 and then wiped with IPA. The face wiping was done n a similar way as the drag wiping.

Attachment2: FC was applied to the HR surface.

Attachment3: The AR surface was also painted with FC. The brush touched the coil holder.

Attachment4: The brush touched the coil holder. Another PEEK tab was applied to remove this FC stain on the metal holder.

Attachment5: This is the result of successful removal of the FC stain.

ITMX

Attachment6: The OSEM arrangement before removal. We confirmed that the OSEM arrangement was as described on Wiki.

Attachment7/8: The ITMX was obviously a lot dirtier than ITMY. The barrel accumulated dusts.

Attachment9: This is the HR face picture with large dusts on it.

Attachment10: The HR surface was painted with FC.

Attachment11: This is the AR surface with FC painted.

  12326   Fri Jul 22 05:20:26 2016 AakashUpdateGeneralTemperature measurements across the enclosure | SURF 2016

Please find the new attached plots and the new script.

  12327   Fri Jul 22 23:03:23 2016 gautamUpdateGeneralETMX suspension - progress

[ericq, gautam]

Summary:

Today, we attempted to progress as far as we could towards getting the mirror suspended and gluing the second wire standoff. We think we have a workable setup now. At this stage, the suspension wire has been looped around the magnet, the second wire standoff has been inserted, coarse pitch balancing has been done, and we have verified that side OSEM/magnet positioning is tenable. Details below.

Details:

  1. First we verified that the epoxy on the side magnet re-glued yesterday had dried (verified using control setup of epoxy in aluminum foil + copper wire - we didn't perform any further tests like pulling the magnet off the tabletop as we were satisfied)
  2. We placed the optic inside the suspension cage, resting on the 4 lower earthquake stops.
  3. We looped the suspension wire around the optic. This is a somewhat challenging procedure. After consulting the documentation, we decided to follow the given advice and loop the wire around from the bottom of the optic, one side at a time. It is tricky to thread the wire between the two lower earthquake stops and get it up around the side. The side magnets were an unexpected ally in this effort as they served as some sort of intermediate checkpoint from which we could pull the wire further up. We then lightly clamped it to the winches mounted atop the suspension cage.
  4. After verifying that we had routed the wire correctly through the various stages (primary and secondary suspension points at the top of the cage), we placed the wire under very slight tension by had, and then tightly clamped the wires in the winches (we then cut off the excess length).
  5. In this state, we proceeded to install the second wire standoff (having verified that the wire was indeed sitting in the groove on the other side). 
  6. We then proceeded to raise the optic to the desired height (center of optic to 5.5 inches above the table top) with the help of the microscope and the lines on the barrel side. 
  7. Next, we attempted to freely suspend the optic (i.e. no contact with the viton tips). We were initially unsuccessful but Eric did some fine adjustment of the (unglued) standoff to achieve a stable configuration. However, the wire is now really close to the magnet - although it is not clear to me if it is touching the magnet as we initially suspected - see Attachment #1, it may be that if the wire is touching something, it is the dumbbell and not the magnet itself. While this is clearly not ideal, we think that this setup is workable as is. If after doing the pitch balancing, if the deviation of the wire becomes much more pronounced, we may have to re-glue the side magnet. In any case, both the horizontal scribed lines are now 5.5 inches above the table top.
  8. We then brought over the OSEMs from the ETMX vacuum chamber to the cleanroom. As a first check, we wanted to ensure that one of the side magnets could accommodate an OSEM (because both side magnets have been re-attached after the optic was removed from the old suspension). Attachment #2 suggests that this is possible, even though the relative positions of the side magnet and the shadow sensor may be sub-optimal. We will only really know after hooking up the electronics.

Remarks:

  1. We found that after a few hours, there was some sag introduced in the wire, presumably it stretched into an equilibrium position under the weight of the optic. We will re-check the heights tomorrow while conducting further tests.

Immediate to-do:

  1. Insert all OSEMS. Ensure that the magnet positions relative to the coil are compatible.
  2. Enable damping loops. We have a cable coming from the IFO area into the cleanroom through a hole-in-the-wall. We are missing a DB25 gender changer at the moment. 
  3. Do the pitch balancing.
  4. Glue the second standoff in place. 

Other attachments:

Attachment #3 - Unglued stand off with wire in the groove, mirror freely suspended.

Attachment #4 - Glued stand off with wire in the groove, mirror freely suspended. Clearance between wire and magnet looks reasonable.

Attachment #5 - Barrel of optic (underside), mirror freely suspended. The wire seems to be in a reasonable orientation along the barrel, albeit not perfectly parallel.


Koji just pointed out that we should check that the unglued ruby standoff is in good contact with the barrel of the optic. Attachment #1 suggests that maybe this is not the case. If you zoom into Attachment #1, it is not clear if the standoff is sitting on the glue.

  12328   Sun Jul 24 03:43:56 2016 ericqUpdateGeneralMagnet positioning

When Koji and I were gluing magnets to ETMY, we decided to position the side magnet based on the empirically observed offsets from the standoff groove seen at other side magnet locations. Specifically, we figured that the magnet should be glued 1.25mm closer to the HR surface than the wire groove.

However, Steve has told me that he believed that this distance should be something like 0.5mm. 

I used the 1.25mm figure when gluing the ETMX side magnets, which now do not align well to their OSEM mounts. While it is certainly possible that I made an error when shimming the fixture, I think it is also possible that this figure was incorrect. 

Sadly, after poring through the DCC and various elogs, I have not been able to come up with a definitive answer on what this offset should actually be.

One approach is to examine the suspension tower dimensions. I.e. when subject only to gravity, the wire loop should lie in the plane of the back face of the top block of the suspension, as it is constrained by the clamps. Thus, the standoff grooves also lie in this plane. The center of the side OSEM mounting holes are about 1.64mm in front of this plane, which is larger than the 1.25mm figure that Koji and I came up with. Examining the picture Gautam posted of the marginal magnet/OSEM alignement, we see that this figure would in fact move the magnet in the wrong direction...

ELOGs in which the intitial side magnet gluing and fixture shimming are detailed do not reference the absolute position of the side magnet, nor do they include any pictures of their fixture setup. (Some links for the curious: 2652 2654 2668)

The DCC isn't much help either, as it is not clear what version of the gluing fixture we actually have. There is a drawing for a 40m specific version, but it includes swappable side-magnet-pickle-picker-slots to achieve different positions for different (circa 2001) optics; this is not the kind of fixture we currently have in our possesion. (https://dcc.ligo.org/D010131) I have discovered that some versions of this fixture (https://dcc.ligo.org/d990168) include an assumed 0.5deg wedge angle and thus position the two side slots differently. Although the fixture we have has no identifying marks on it whatsoever (naturally), I measured the two side slots to be different in axial position by roughly 0.6mm, which is consistent with a 0.5deg wedge. Furthermore, the sign of this difference indicates that this fixture ring is designed for the opposite wedge orientation than our ETMs, which have a 2.5deg wedge, making this fixture wrong by 3deg (which is ~4mm over the diameter of the optic). 

We did not account for this for either ETMX or ETMY, so this is another source of error, but this does not give us much guidance on what the real absolute magnet position should be.

  12329   Mon Jul 25 10:54:55 2016 PrafulUpdateComputer Scripts / ProgramsFinished MEDM Tab on Summary Pages

The MEDM screen capture tab is now working and up on the summary pages: https://nodus.ligo.caltech.edu:30889/detcharsummary/day/20160725/medm/

Please let me know if you have any suggestions or notice any issues.

  12330   Mon Jul 25 12:22:18 2016 ranaUpdateComputer Scripts / ProgramsFinished MEDM Tab on Summary Pages

Looks pretty great. However, there's two problems:

1) Some of the MEDM screens don't show the time. You can fix this by editing the screens and copy/paste from screens which have working screens.

2) The snapshot script seems to not grab the full MEDM screen sometimes.

These are not a very big deal, so you can get the microphones working first and we can take care of this afterwards.

  12331   Mon Jul 25 13:01:49 2016 ericqUpdateGeneralETMX suspension - progress

(Full resolution versions of the photos in this ELOG are on picasa)

The OSEM gender changers were not in the box labelled as such, we need these to be able to use the OSEMS to see just how bad the side magnet alignment is, and to do any kind of damping for the fine pitch balancing. The hunt is on.

In the meantime, Gautam and I checked out the standoff seating, and alignment of the face OSEMS (after slightly adjusting the wire length - I guess some sagging is still happening).

With a bit of poking, we convinced ourselves that we sat the standoff in contact with the optic's barrel. Amazingly, we were able to maintain the coarse pitch balance of the optic.

We then partially inserted the face OSEMS, to check their magnet alignment. ("partially" means that the OSEM is not actually enclosing the magnet, we don't want to knock anything off) They seem ok, but not perfect. These magnets were not removed or reglued, so presumably their alignments should be unchanged.

  12332   Mon Jul 25 13:47:19 2016 ranaUpdateGeneralETMX suspension - progress

Ugh. frown

Steve, please look into getting some plated magnets (either SmCo or NdFeB is OK) of this size so that we can install cleaner magnets by the next vent.

  12334   Mon Jul 25 17:01:54 2016 SteveUpdateSUSETMX suspension - progress

ITMY side  : Magnet od 1.9 mm so wire to magnet gap ~ 0.2-0.3 mm

 

ELOG V3.1.3-