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ID Date Author Type Category Subjectup
  5693   Wed Oct 19 09:44:10 2011 steveUpdateSUSETMX oplev power spectrum

Quote:

 ETMX oplev had 6 mm diameter beam on the qpd.  I relayed the beam path with 2 lenses  to get back  3 mm beam on the qpd

BRC 037  -100 Bi _concave lens and PCX 25  200 VIS do the job. Unfortunately the concave lens has the AR 1064.

 

 

 Coherence at 1 and 2-3 Hz only. He/Ne laser intensity noise is not an issue.

  9973   Tue May 20 09:12:25 2014 SteveSummarySUSETMX oplev qpd board

Quote:

 ETMX oplev qpd gain has to be increased.

 

 Atm3, Oplev sum read 12,000 counts when the qpd was disconnected ?

           Dark qpd was zero and normal He/Ne incident on qpd was 1,730 counts.

  9975   Tue May 20 15:54:39 2014 ranaSummarySUSETMX oplev qpd board

 This QPD circuit (D980325-C1 ) uses the nice OP497 Quad FET opamp as the transimpedance amplifier. It has a low enough current noise, such that we can increase the resistors (R1-4) up to 100k and still be Johnson noise limited. We should also make sure that the compensation caps (C3-6) are ~2.2 nF so as to not destabilize the opamp. f_low = 1/2/pi/R/C = 730 Hz.

I will do the swap later today unless someone else gets to it first. (note: check for oscillations w/ fast scope probe after installing)


I did these modification tonight. The slideshow of some images is attached. Instead of 100k, I used 97.6k thin film, since this seemed like an oddball size that doesn't get used otherwise. I forgot to measure the dark noise of the quadrants before doing the swap, but comparing the pit/yaw/sum before/after the swap shows that the signal is basically unchanged (since pit/yaw is normalized by SUM), but that the noise is lower by a factor of a few above 100 Hz due to being above ADC noise now. Previously, it was bottoming out at ~10 prad/rHz. Since the signal is unchanged, I guess that the calibration and therefore the loop gain should not have changed either...

And the sum went up by almost 10x as expected from the resistor change.

  5680   Mon Oct 17 17:07:30 2011 steveUpdateSUSETMX oplev returning beam od 3 mm

 ETMX oplev had 6 mm diameter beam on the qpd.  I relayed the beam path with 2 lenses  to get back  3 mm beam on the qpd

BRC 037  -100 Bi _concave lens and PCX 25  200 VIS do the job. Unfortunately the concave lens has the AR 1064.

 

 

  146   Fri Nov 30 13:46:50 2007 robConfigurationElectronicsETMX oplev dead again

Quote:
In the interests of getting the Xarm alignment script working again, I reset the local damping gains for the test masses to their previous known working values (1), then I noticed that the ETMX oplev was dead. Since the scripts use the oplev motion as a readback for the optic motion, this means the script was basically blindly swinging the optics around. Some monkeying around with swapping HeNe power supplies eventually led to the conclusion that the power strip is funky, since the laser works when plugged into another power strip. Even weirder, the HeNe and the power supply indicator light have some sort of XOR relationship going on. When one works, the other doesn't. Steve will sort out this confusion later; we're good for now.


Ech. The HeNe quit again. Let's replace it and see what happens.
  147   Fri Nov 30 19:11:05 2007 ranaConfigurationElectronicsETMX oplev dead again
I removed the ETMX HeNe and put in on a test table and it fired up fine. In its
previous location the light on the HeNe power supply was not lighting up. If
that's still on over the weekend we'l blame the power strip; the HeNe is a JDS
2.7 mW laser from 2002.
  5587   Fri Sep 30 17:01:29 2011 steveUpdateSUSETMX oplev intensity effect on noise

Kiwamu and Steve,

This is one of the better oplev set up we have. Single bounce from TM, no mirror on stack. One lens and one  mirror on ISCT. Old Uniphase 1103P laser on heafty 3" od mounts.

Somewhat  big ~5-6 mm spot on qpd in  1,300 counts.

The intensity noise effect can be seen at 1 Hz and 3-20 Hz

Oplev servo was OFF

  5844   Wed Nov 9 07:57:39 2011 steveUpdateSUSETMX oplev is down and sus damping restored

The ETMX oplev returning beam is well centered on the qpd. We lost this signal 2 days ago. I will check on the qpd.

ETMX sus damping restored.       c1iscex computer is down

  5845   Wed Nov 9 10:35:30 2011 jamieUpdateSUSETMX oplev is down and sus damping restored

Quote:

The ETMX oplev returning beam is well centered on the qpd. We lost this signal 2 days ago. I will check on the qpd.

ETMX sus damping restored

 As reported a couple days ago, the ETMX IO chassis has no timing signal.  This is why we there is no QPD signal and why we turned off the ETMX watchdog.  In fact, I believe that there is probably nothing coming out of the ETMX suspension controller at all.

I'm working on getting the timing board replaced.  Hopefully today.

  9947   Tue May 13 17:03:05 2014 SteveSummarySUSETMX oplev laser replaced

Quote:

Quote:

For some reason or another, I decided that we should see if the optical lever servos were injecting too much noise into the test masses. The ITMs are much worse than the ETMs and I am afeared that they might be making the main noise for our arms in the 20-40 Hz region. Jenne is checking up on these feedback loops to see what's up.

To estimate the actuator gains of the mirrors, I turned on 1 count drives from LSC/CAL oscillators into the LSC drives of each test mass at the frequencies shown in the plot with the resulting peaks showing up in in POX/Y with the single arm locks in red. I will leave these going permanently, but with 0.1 count ampltiudes; we need to make it so in the scripts.

 I'm in the process of filling this table

OPLEV

SERVO     

300 ^

2:0

BR ELP RLP BOOST RES

GAIN

QPD

COUNTS

 

QPD

mW

QPD

beam

OD

HE/NE

output

mW

%

back

on QPD

                                
ETMY PIT  FM1  FM5    55      -30 8,200 0.2   3.3  
        YAW  FM1  FM5    55      -28          
ETMX PIT  FM1  FM5  35        4.4 900 0.2   1.7  
       YAW  FM1  FM5  35       2.1  1,750  0.33    2.8  
ITMY PIT  FM1  FM5        3.3   52 14,400 0.4   9.5  
      YAW  FM1  FM5        3.3  -46          
ITMX PIT  FM1  FM5  50      3.3   30 7,400 0.17   2.8  
       YAW  FM1  FM5  50      3.3  -20          
BS  PIT  FM1  FM5  35      3.3   9 2,800 0.05   2.8  
    YAW  FM1  FM5  35      3.3  -9          
PRM  PIT FM1  FM5  55   FM7  3.3  7 3200 0.06   2.8  
       YAW FM1  FM5  55   FM7  3.3  -5          
SRM  PIT  FM1            -20       9.5  
       YAW  FM1            20          

 I should replace ETMX He/Ne laser

 

  9948   Tue May 13 17:31:32 2014 JenneSummarySUSETMX oplev laser replaced: New oplev gains set

I took loop measurements of ETMX pit and yaw, and set the upper UGF to be ~6Hz for both.  This required a pitch gain of 25, and a yaw gain of 16.

The spectra look similar to what they were before Steve did the swap.

OLerr_13May2014.pdf

OLfb_13May2014.pdf

  11729   Wed Nov 4 14:44:00 2015 ericqUpdateSUSETMX oplev servo disabled

I've turned the ETMX oplev servos off for the time being. (At the input side, so that no scripts will accidently turn it on).

Thus, only the local damping is being applied, let's see if we see any kicks...

  11733   Wed Nov 4 22:42:02 2015 ericqUpdateSUSETMX oplev servo disabled

During this time period, it looks like there was maybe one excursion. Here are the individual OSEM signals, which I think to be calibrated to microns. 

When I'm doing other things, I'm going to intentionally leave the watchdog tripped, and see if anything happens. 

  11744   Mon Nov 9 23:22:18 2015 ericqUpdateSUSETMX oplev servo disabled

During a ETMX kick that just occured, with only local damping on, the slow VMon channels didn't show any noticable change. 

  11752   Wed Nov 11 14:06:09 2015 ranaUpdateSUSETMX oplev servo disabled

How many volts does it take to pitch the ETM by 5 urad?

  11758   Thu Nov 12 10:47:17 2015 ericqUpdateSUSETMX oplev servo disabled

By looking at the oplev and Vmons before and after a step of 90 counts in SUS-ETMX_PIT_OFFSET, I observe:

  • UL: +1.53mV / urad
  • UR: -1.94mV / urad
  • LR: -1.54mV / urad
  • LL: +1.92mv / urad

The random error associated with these measurements is ~0.02mV

So, the ~7urad urad shift seen in my earlier post would mean a change of around 10mV in the Vmon signals, which isn't evident in the traces. So, this is possibly a piece of evidence in favor of a real mechanical shift, rather than an electronic glitch. 

  9950   Tue May 13 22:55:57 2014 JenneSummarySUSETMX oplev: cleanup

I believe that the Xend aux laser was turned off earlier today, for Steve's work swapping out the oplev.  When I went down there, the red "off" LED was illuminated, and the LCD screen was showing something.  I pushed the green "on" button, and I immediately got green.

Also, I saw that the 24Hz roll mode was very rung up on ETMX.  I looked at the FM5 "bounce roll" filter, and it had some old values, 12Hz and 18Hz for the resonant gains.  All other optics have the proper 16Hz and 24Hz frequencies.  I copied the BS oplev bounce roll filter over to ETMX pit and yaw (both were wrong), and loaded them in.  The mode is starting to ring down.

  9738   Tue Mar 18 18:05:57 2014 SteveUpdateSUSETMX osem UR

 

  UR osem IR shield glass is pushed back. It came out of its clip holder. The magnet is free.

  Atm2,  UL & LL magnets  centered poorly. Almost hinging on opposite sides.

              UR & LR centered well.  There have plenty of room to move in an earth quake.

  12612   Sun Nov 13 23:42:43 2016 LydiaUpdateSUSETMX output matrix data

I took data of the ETMX SUSPOS, SUSPIT and SUSYAW channels while driving each of the 4 face coils. I manually turned off all the damping except the side. 

Excitation: I used white noise bandpassed from 0.4 to 5 Hz in order to examine the responses around the resonance frequencies. To avoid ringing things up too much, I started with a very weak drive signal and gradually increased it until it seemed to have an effect on the mirror motion by looking at the oplev signals/sensor RMS values on the SUS screen; it's possible I'll need to do it again with a stronger signal if there's not enough coherence in the data. 

Finding the matrix: The plan is to estimate the transfer function of the coil drive signal with the sensed degrees of freedom (specified by the already diagonalized input matrix). This transfer function can be averaged around the resonance peak for each dof to find the elements of the matrix that converts signals to dof responses, (the "response matrix", which is the inverse of the output matrix). Each column of the response matrix gets normalized so that the degrees of freedom influence the drive signals in the right ratio. 

Other notes: 

  • I had some trouble getting the awg python library to work: I had to manually edit a CDLL statement to use the absolute path of an .so file. I wasn't sure what environment variable to set to make it look in the right folder automatically.
  • The awg ArbitraryLoop object seems to be affected by cds getdata calls (The EXC signal stopes early and then stop() hangs) so I ended up doing the excitation and data reading in 2 separate scripts. 
  • Reminder that the watchdogs must be on "Normal" for the EXC signal to make it to the coils, so the damping must be turned off manually with the watchdogs still on if you want to drive without damping. 
  14982   Mon Oct 21 16:02:21 2019 gautamUpdateSUSETMX over the weekend

Looking at the sensor and oplev trends over the weekend, there was only one event where the optic seems to have been macroscopically misaligned, at ~11:05:00 UTC on Oct 19 (early Saturday morning PDT). I attach a plot of the 2kHz time series data that has the mean value subtracted and a 0.6-1.2 Hz notch filter applied to remove the pendulum motion for better visualization. The y-axis calibration for the top plot assumes 1 ct ~= 1 um. This "glitch" seems to have a timescale of a few seconds, which is consistent with what we see on the CCD monitors when the cavity is locked - the alignment drifts away over a few seconds.

As usual, this tells us nothing conclusive. Anyways, I am re-enabling the watchdog and pushing on with locking activity and hope the suspension cooperates.

Quote:
 

The satellite box was reconnected and the suspension was left with watchdog off but OSEM roughly centered. We will watch for glitches over the weekend.

  4000   Tue Nov 30 18:15:52 2010 JenneUpdateSUSETMX ready to be installed. ETMY ready for winching

[Jenne, Kiwamu]

We put ETMX back in its tower, and confirmed its balance.  It might be pointing a teensy bit upward, but it is way less than the DC pointing offset we see when we put the OSEMs in the towers (since the PDs and LEDs have some magnetic bits to them).

Discussions are ongoing as to where the ETM should sit on its table, but we'll probably toss it into the chamber later this evening.

I took ETMY out of the magnet gluing fixture, and put it in a ring, in the foil house.  It is ready to have the wire winched and get balanced at our convenience.

The updated status table:

StatusTable.png

  12274   Fri Jul 8 14:03:26 2016 ericqUpdateGeneralETMX removed from suspension

ETMX is currently in the clean room, the barrel is the tiniest bit submerged in acetone that will remove a guide rod, standoff, and side OSEM. 

Additional inpsection of the standoffs on the flow bench did not provide any insight, pictures are in picasa. Here is a cropped version of a picture we took:

 

We should look at them under a microscope.

  12276   Fri Jul 8 16:33:26 2016 ericqUpdateGeneralETMX removed from suspension

The magnet, guide rod, and standoff came off without too much force. However, some epoxy residue remains on the barrel. I didn't really want to scrape it off, so I've opted for more soaking. Much of the acetone had evaporated already, so I put some more - just to the point where the residue is submerged. 

  12278   Fri Jul 8 20:44:09 2016 KojiUpdateGeneralETMX removed from suspension

In the evening, I went into the clean room to check how it goes.

- The air around the table is quite warm like a hell. Is this normal?

- I checked how the scattered epoxy spots look like. They were not touching the bath anymore due to evaporation.
- I scraped the spots with the tweezers there. They were easily removed. The particlates on the side barrel were wiped by a wipe with aceton. (Result: Attachment 3)

- Then looked at the other side. I poked the standoff with the tweezer. It was easily removed. I don't think the bond was too weak. Just the area of the bond was so tiny.
- Also residue was scraped by a tweezer and wiped with a cloth. (Attachment 2)

- The removed stand off is in the stainless bowl together with the parts that Eric removed.

- I didn't want to leave the optic in the aceton fume. It was placed on a metal donuts for a 3" optic. (Attachment 4)

- I couldn't find a vacant clean glass jar for the lid. So, a foil hut was built. We should be very careful not to scratch the optic when we remove the hut. (Attachment 5)

- The aceton bath was covered with the foil as it was. (Attachment 6)

  5853   Wed Nov 9 17:41:17 2011 JenneUpdateComputersETMX restored

Jamie did computer magic.  I burt restored scxepics, and restored ETMX damping.

  8510   Tue Apr 30 10:54:35 2013 JenneUpdateSUSETMX restored

I'm not sure why or when it was tripped, but I have restored the ETMX watchdog.

  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 :/

  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!

  14977   Fri Oct 18 17:35:07 2019 gautamUpdateSUSETMX sat box disconnected

Koji suggested systematic investigation of the ETMX suspension electronics. The tests to be done are:

  1. Characterization of PD whitening amplifiers - with the satellite box disconnected, we will look for glitches in the OSEM channels.
  2. Characterization of LT1125s in the PD chain of the amplifiers - with the in-vacuum OSEMs disconnected, we will look for glitches due to the on-board transimpedance amplifiers of the satellite box.
  3. Characterization using the satellite box tester - this will signal problems with the physical OSEMs.
  4. Characterization of the suspension coil driver electronics - this will happen later.

So the ETMX satellite box is unplugged now, starting 530 pm PDT.

The satellite box was reconnected and the suspension was left with watchdog off but OSEM roughly centered. We will watch for glitches over the weekend.

  7079   Thu Aug 2 21:40:55 2012 JamieUpdateSimulationsETMX simplant model revived

I revived the ETMX simplant model, c1spx.  It's running on cpu4 on c1iscex, and interfaces with C1scx via SHMEM.

The channel names for the simplant suspensions will be SUP, so the channel from this model will C1:SUP-ETMX_.

Next I'll try to get the ITMX and LSC ("LSP") simplant models running so we can run a "full" cavity simulation.

Sasha has been working on LSP, so we should be ready to do something with that soon.  In the mean time she's going to fix up the SPX MEDM screens, since some channel names have been changed since it was last run.

  7500   Mon Oct 8 10:56:59 2012 JenneUpdateSUSETMX slow machine dead??

I think the ETMX slow machine might be dead.  All of the regular FE readbacks are fine, and the c1iscex FE computer looks fine, but the slow readbacks are all whited out. 

I turned off the damping loops for ETMX, since I don't have access to the watchdog disable/enable switch.  I guess checking this out will be task #1 for Monday morning.

  7502   Mon Oct 8 11:44:21 2012 JenneUpdateSUSETMX slow machine fine

Quote:

I think the ETMX slow machine might be dead.  All of the regular FE readbacks are fine, and the c1iscex FE computer looks fine, but the slow readbacks are all whited out. 

I turned off the damping loops for ETMX, since I don't have access to the watchdog disable/enable switch.  I guess checking this out will be task #1 for Monday morning.

 For lack of a better idea, I keyed the crate.  The computer came back up just fine, ETMX is happily damped again.

  5675   Mon Oct 17 07:57:24 2011 steveUpdateSUSETMX sus damping restored
  12362   Wed Aug 3 00:15:39 2016 gautamUpdateSUSETMX suspended

[lydia, steve, ericq, gautam]

Summary:

  • ETMX is now suspended by wire clamps (winches have been removed) yes
  • Wire clamp was machined by shop, D groove widened to spec, old wire grooves removed from face
  • We also sanded the part of the suspension tower in contact with the primary wire clamp, as there were a couple of craters there which looked dangerous (pictures to follow)
  • Height was adjusted by centering magnets on OSEMs. We then winched an extra half turn in anticipation of wire sag
  • I then proceeded to tighten, first, the primary wire standoff (I reduced the torque on the torque wrench to ~1.25Nm), and then the secondary wire clamps.
  • Checked that the ruby standoff is sitting on the optic barrel and not on glue 
  • Later in the evening, I inserted OSEMs, centered magnets, and checked that the damping scheme set up last week works (I'm leaving the damping on, bottom EQ stops are ~0.5mm from the optic)
  • Checked the pitch balancing - initially, we were ~60mrad off. By using the tweezers to gently adjust the position of the ruby standoff (after clamping the optic, turning the damping off), I was able to improve the situation a little bit - now we are ~20 mrad off. I am not attempting to do the fine pitch balancing tonight, but all parts of the PZT buzzer set up are ready to go in the cleanroom.
  • Unfortunately, in the process of doing the pitch balancing, the position of the magnets relative to the OSEM coils have moved. Now the UR magnet looks a little high relative to the coil, but perhaps after any sag has set in, we should be alright. Else, we can probably get away by inserting one of the little metal shim pieces, the adjustment required is small.
  • Lydia will upload some photos soon. 
  • We actually went through another failed attempt today - this time, the problem was that the winches were not sufficiently secure at the top, such that when the range of the winch was nearing its end, the whole assembly twisted and took the wire along with it. Perhaps this would not have happened if we had a winch adaptor plate handy...
  • Plan for tomorrow:
    • ​Fine pitch balancing using PZT buzzer
    • Clean ETMY epoxy residue from knocked off magnet
    • Glue wire standoff
    • Glue ETMY magnet
  12370   Thu Aug 4 03:14:39 2016 gautamUpdateSUSETMX suspended
Quote:

[lydia, steve, ericq, gautam]

Summary:

  • ETMX is now suspended by wire clamps (winches have been removed) yes
  • Unfortunately, in the process of doing the pitch balancing, the position of the magnets relative to the OSEM coils have moved. Now the UR magnet looks a little high relative to the coil, but perhaps after any sag has set in, we should be alright. Else, we can probably get away by inserting one of the little metal shim pieces, the adjustment required is small

[lydia, ericq, gautam]

  • Turns out setting the height of the optic with the OSEMs isn't quite reliable. We were indeed too high, for all the OSEMs
  • Related to the above - we observed no sag (which is one of the reasons we winched a little bit extra in the first place)
  • Eric and I re-did the suspension in the afternoon. We found no wire grooves in the primary (or secondary) clamps, so we just reused them (is this a red flag? should we be using more torque?)
  • This time we set the height using the traveling microscope - double checked the height to which the microscope was levelled = 5.5"
  • Having checked the height of both scribe lines, we proceeded to clamp the suspension, with ~1.35Nm of torque (since 1.25Nm seemed a little low, no wire grooves were made in the clamps) - clamping was successful
  • In the evening, Lydia and I attempted to do the fine pitch balancing
  • Both left side magnets (as viewed from the AR side) are low (within 0.5mm of the teflon). Right side magnets are pretty well centered. But left side ones seemed usable so we went ahead and tried to turn the damping on.
  • Damping worked reasonably well
  • Tried to do fine pitch balancing with PZT buzzer. Reduced voltage from Fn generator to 0.4Vrms (down from 1.7Vrms) but had limited success. 
  • I was able to do much better with just the teflon tipped tweezers. So gave up on the PZT buzzer
  • After ~3hours of a random walk between two pretty-close-to-ideal positions, we have now realized a fine pitch balancing of ~1mrad (~3mm off the ideal height of 5.5" over a lever arm of ~1.5m, but the mirror tilt is half of this angle)
  • Actually, I was able to do much better - at one point, we even had the reflected beam dead center on the iris 1.5m away. But adjusting the OSEM positions even a little bit (say from oscillating around 40% to 50% of the maximum value) has a BIG effect on the pitch balance (it caused a misalignment of 4mrad)
  • I think gluing the standoff without destroying the fine pitch balancing is going to be very challenging, judging by how gently I had to touch the standoff to destroy the fine pitch balance completely. Perhaps we want to consider using some 3 axis stage to bring the needle with glue in and perturb the standoff as little as possible

    Lydia also briefly played around with the IR camera to inspect the OSEMs. A more thorough investigation will be done once the cage is in for air baking. From our initial survey, we feel that the beams are pretty well aligned along the straight line between PD and LED - we estimate the upper bound on any misalignment to be ~10 degrees.

 

  12426   Sun Aug 21 16:23:05 2016 gautamUpdateSUSETMX suspended
  • ETMX has been successfully suspended
  • I've used one of the new wire clamps, and also the new suspension wire 
  • Because the HR face has first contact, pitch balancing cannot be checked at this point. But since the pitch balance was checked after the standoff was glued, there is no reason to believe it would have changed
  • Heights of the two scribe lines were checked with the microscope and verified to be at 5.5" above the tabletop. Also checked the position of the scribe line on the bottom of the optic to make sure the optic wasn't somehow rotated
  • Checked that wire was in the groove in the standoff on both sides, and that the optic was freely hanging with no EQ stops engaged. I also verified that there are no obvious kinks/other funny features where the wire is in contact with the optic barrel below the standoffs.
  • Wire clamps were tightened with the new torque wrench and 5 in. lb. (0.56 N m) of torque. Primary clamp was successfully tightened. However, the wire snapped between the primary and secondary clamps on one side. It is unclear to me how or why this happened. But since the primary wire clamp is the important one, I don't think it is worth re-suspending ETMX all over again
  • I've left the cage on the flow bench for now, with EQ stops engaged. OSEM coils have yet to be inserted, but I suppose we want to do this in the vacuum chamber now to do the fine rotation to minimize the bounce mode in the OSEM signals
  • I've prepared ETMY and its cage for suspension, will work on it tomorrow
  12351   Fri Jul 29 03:32:30 2016 ericqUpdateGeneralETMX suspended once more

[gautam, ericq]

Tonight's progress on ETMX:

  • All pickle pickers removed successfully, face magnet positions look symmetric (all on border of AR coating), side magnet same location as in yesterday's photo
  • Flipped around clamp blocks on winches and top blocks, refinished main clamp block not on tower yet
  • Trimmed viton tips of EQ stops, I had left them too long before, leading to bending and unwanted translation when in contact with optic
  • Inserted optic into bottom EQ stops, turned bolts to position optic at correct height and sort of pitch leveled
  • Threaded new length of wire up through both sides, clamped at winch. Made an effort to avoid any wire twisting. 
  • Winched until enough tension to sit in standoff groove, inserted second ruby standoff
  • Winched to just come up off of bottom EQ stops, observed neccesary correction of second standoff for rough pitch balance
  • Roughly pitch balanced by iterating standoff location
  • Partially inserted OSEMS, all four face magnets looked low. We figure it's more likely that our microscope was set to the wrong height, than all four OSEMS being too high by the same amount. (Given how the face magnets are all located on the concentric circle of the AR coating, we know there wasn't much translation error in the magnet gluing)
  • Did some common mode winching of both wire ends to get magnets to correct height, all OSEM alignments look good
  • Inserted OSEMs to half of open voltage
  • Having trouble engaging stable damping of all DoFs, this will be followed up in the daytime.

Since the air bake oven we had been using is out of commision, we're not sure where to do our EP30 test runs. If we are fortunate, we can get the fine pitch balance done tomorrow while Bob is still around, so he can help us quickly bake the test dots, so we can do the standoff gluing. 

  12363   Wed Aug 3 09:26:54 2016 LydiaUpdateSUSETMX suspended: photos

Here are the photos we took showing the magnet positions in the OSEMs, and others showing the positions of the wire and unglued standoff. These were taken before the pitch balancing adjustment Gautam described, which apparently cause UR to be a little too high. Thoe OSEMs were all inserted only until the ends of the magnets were almost inside, to lower the risk of knocking any magnets off.

 At the time of these pictures, all magnets except LL were intentionally positioned slightly above the center of the OSEM in anticipation of wire sag. The LL magnet was approximately centered in the OSEM. It was not possible to get both LL and UL the same height relative to their respective OSEMs, possibly due to a spacing error when they were glued to the optic. 

Attachment 1: Position of wire along bottom of the optic. Looks adequately centered and not kinked. 

Attachment 2: Photo showing good contact between the sandoff and the barrel of the optic. The standoff does not appear to be resting on glue from the guiderod. 

Attachment 3: Shows position of standoff and wire after rough pitch banacing. Wire is visibly resting in the groove.

Attachment 4: SD magnet location photographed through OSEM.

Attachment 5: LL magnet location photographed through OSEM.

Attachment 6: LR magnet location photographed through OSEM.

Attachment 7: UL magnet location photographed through OSEM.

Attachment 8: UR magnet location photographed through OSEM.

 

  12340   Tue Jul 26 18:07:57 2016 gautamUpdateGeneralETMX suspension - Further OSEM Tests

Today, we did the following:

  • Once again, inserted all four face OSEMs till the sensor voltage readouts were approximately half their saturation value. The presence of some ferromagnetic material in the Honeywell components makes this tricky as each coil is coupled to the other three, but we were able to converge to a point where all the voltage readouts were oscillating around a mean value of ~40-60% of their maximum value, with all the damping loops OFF.
  • Turned on all damping loops, and verified that the OSEM positioning was indeed such that the sensor readout is nominally around 50% of the saturation value. The air buffeting around the clean bench means that the damping isn't nearly as effective as it is inside the vacuum chamber.
  • Attempted to increase the gain on the damping loops - we first switched out the Chebyshev low-pass filter in all the damping loops for something a little less aggressive, to allow us to turn up the gain. However, this experiment wasn't a success, when we turned the damping loops on, they were ringing the optic up.
  • At this point, Eric checked the offset sliders (summed in via the slow system) and saw that they were not zero. We zeroed these, but naturally, they destroyed the OSEM positioning equilibrium we had established earlier. So we had to go back and re-position the OSEMs
  • After re-centering the face OSEM magnets relative to the LED-PD pair, we insertd the side OSEM such that the side magnet completely occluded the PD. Interestingly, Eric noticed that the magnetic attraction between OSEM and magnets conspired to center the side magnet fairly well in the side OSEM, when it completely blocked the PD. However, when he returned the side OSEM coil to its nominal operating position of approximately half-blocking the PD, some minor misalignment was re-introduced (i.e. even when the optic was swinging mostly along the axis of the side OSEM, the voltage readout did not quite go down to 0). 
  • We then decided to compare the spectra for the error signals for the 4 DOFs with the current configuration (i.e. suspension clamped down to table top, optic freely hanging, all OSEMs reasonably well centered, and with the ETMX SUS model reverted to its normal state) to some reference (see Attachment #1). I initially thought I would wait for the optic to settle down a bit more before taking the spectra, but it doesn't seem to be showing any signs of getting any quieter in the last one hour. In Attachment #1, I have plotted as reference the spectra of the error signals from the early hours of 4 July 2016, at which point we were at atmosphere but the heavy doors were not yet off, so this is not really a fair comparison, but we don't really have a period in which the optic was exposed to the atmosphere and with the OSEMs in place, at least from this vent. Colors are identical for a given DOF, with todays trace as a solid line, and the reference dashed.
  • We did not check the room available to install some shimming piece of metal in the side OSEM holder, as a possible solution to solve the misalignment problem. Steve has already found pieces of varying thickness, and they are soaking in acetone right now, we plan to air bake them tomorrow. 

I will have another look at the spectra tomorrow morning, to see if the damping improves overnight. 

  12335   Mon Jul 25 20:37:46 2016 gautamUpdateGeneralETMX suspension - Side OSEM test

[Lydia, gautam]

Summary: We did some preliminary tests to check if at least one of the side magnet positions is usable for the side OSEM. We mainly wanted to check how much dynamic range we lose because of the sub-optimal longitudinal positioning of the side magnet. We found that when the side magnet was mainly moving along the axis of the side OSEM (with minimal yaw motion as gauged by eye), the PD voltage bottomed out at ~80 counts (while the completely unoccluded readout was ~800 counts). 

Details:

  1. First, we placed the face OSEMs into their holders one by one, and adjusted their position till the readout was approximately half the saturation value (as judged by the average value of the readout, at this point, the mirror was still swinging around a fair bit).
  2. Next, we enabled the POS, PIT and YAW damping (with all existing settings unchanged), but with the SD coil input and output disabled. We had to increase the watchdog threshold to ~600mV.
  3. Once the optic was reasonably well damped (~70mV on the watchdog was the best we saw), I put in the side OSEM till the PD was completely occluded. At this point, I enganed the earthquake stops, and then released the mirror such that it was freely hanging. I then observed the optic by eye, and noted a time when the dominant motion was along the axis of the side OSEM coil (i.e. minimal YAW motion). 
  4. Attachment #1 shows time series plots of the 5 OSEM PD voltage monitors. Perhaps because the side OSEM input was disabled, the damping wasn't as efficient as it normally is (also there is a fan blowing air around the clean bench). But at the point indicated on the plot, the YAW motion was negligible to the eye, while the dominant motion was along the axis of the coil. During this time, the readout bottomed out at approximately 10% of the saturation value (towards the end of these plots, I disabled the damping loops and began pulling the OSEMs out one by one). Because the damping was imperfect, this is only an approximate guess of how much dynamic range we are losing. But does this warrant regluing the side magnet?

Other remarks:

  • The 4 face magents were reasonably well centered in the coil. While Eric and I were looking at this earlier today, the LL magnet looked a little close to the coil, but after putting all 4 OSEMs in, the situation looked reasonable to the eye. I couldn't take pictures because of space constraints, and furthermore, it's almost impossible to hold the camera in the correct vertical position. 
  • Steve, Eric and I couldn't find the OSEM gender changer anywhere in the lab and it wasn't in the box it was advertised to be in. So we made a custom cheater cable, and cleaned it by wiping with Isoprop., and wrapped it in foil for use in this test. The OSEM pins should probably be cleaned before we put these back in vacuum. 
  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.

  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

 

  12716   Fri Jan 13 23:39:46 2017 gautamUpdateGeneralETMX suspension electronics problems?

[Koji,gautam]

After Koji's leap second fix, we were playing around with the X arm locking. In particular, we were playing around with the limit value on the X arm LSC filter bank - the nominal value is 4000, we wanted to see if we could increase this without kicking the optic while acquiring arm lock. We initially increased it to 8000, and then turned it off altogether. Then we rapidly turned the output of the servo ON/OFF, and looked at the arm transmission to see if it came back to the level before unlocking, as an indication of whether the optic was kicked.

These trials suggested a value of 8000 for the limiter was OK, so we left the LSC mode on with the limiter set to 8000. But just as we were about to leave for the night, I noticed on the wall Striptool that the X arm was unlocked. Investigating, we found that the green wasn't even locking to a HOM. Further investigation of the Oplev spot showed that ETMX had received a large kick (both pitch and law errors were ~200urad). ITMX was unaffected.

We initially tried lowering the LSC limit value back to 4000, then used first the Oplev spot and then the green to align the arm. But turning on LSC misaligned the arm after acquiring lock. So we decided to leave LSC off, thinking that the notorious ETMX suspension problems have resurfaced. As a diagnostic, we figured we'd leave the watchdog tripped, and use the Oplev to see if the optic was getting kicked. But the act of turning the watchdog off kicked the optic again (WHY?!).

Looking at the ETMX sus screen, turning off all the damping and LSC (but watchdog on) still leaves a non-zero offset in the "Vmon" field, between 0.02-0.05V depending on the coil. Turning the watchdog OFF takes all these to 0.009V, although I can see the LR value fluctuating between 0.004V and 0.009V. I went to the Xend and squished all the cables on the Sat. Box, but the problem persisted.

At this time, I can't think of any explanation, so I am giving up for the night. To avoid unnecessarily kicking the optic, I am going to unplug the suspension from the Sat. Box and leave one of our tester boxes plugged in, lets see if that sheds any light on the situation...


Notes:

  1. The +/-20V sorensens at this end were "tripped" for a few days after the power glitch until they were reset and turned back on yesterday. But this should not affect Vmon, as these Sorensens only supply the DC voltage for the coil bias, which is a slow machine channel?
  2. The X arm was staying locked and well aligned for hours on end earlier this afternon - in fact it was locked for about 2 hours 6-8 hours ago, I can still see the trace on the wall StripTool....
  12729   Tue Jan 17 21:31:57 2017 gautamUpdateGeneralETMX suspension electronics problems?

Last night, I plugged the ETMX suspension coils back into the satellite box. Tonight, we turned on the damping loops for ETMX. Rana centered the Oplev so we can use that as an additional diagnostic to see if the optic gets kicked around overnight. We will re-assess the situation tomorrow.

Sometime earlier today, Lydia noticed that the +/- 5V Sorensens at the X end were not displaying their nominal voltage/current values (as per the stickers on them). She corrected this.

  12730   Wed Jan 18 10:41:14 2017 gautamUpdateGeneralETMX suspension electronics problems?

Summary pages show no kicking in the ETMX watchdogs from midnight to 6 AM (0800 - 1400 UTC):

https://nodus.ligo.caltech.edu:30889/detcharsummary/day/20170118/sus/watchdogs/

  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
  7541   Sun Oct 14 16:44:20 2012 DenUpdatePEMETMX table

 I've measured ETMX table motion compared to ground motion using accelerometers. Data and settings in the xml file are at the svn directory 40m_seismic/etmx.

DSC_4742.jpg

  7542   Sun Oct 14 17:26:03 2012 DenUpdatePEMETMX table

Quote:

 I've measured ETMX table motion compared to ground motion using accelerometers. Data and settings in the xml file are at the svn directory 40m_seismic/etmx

 High frequency (>60 Hz) resonances that are present at the ETMX motion spectrum seem to be understandable. Amplification ETMX/GROUND of a factor of 2 at 1 Hz is interesting. I've monitored ACC DQ channels for a few hours and noticed that usually spectrum looks like in the previous elog. But every ~40 min ETMX motion is much higher then ground motion at low frequencies (<5 Hz). I wonder if this a reaction of a table to outside disturbances or accelerometer issue.

 

ELOG V3.1.3-