Sorry I was writting the elog, but I had to dive into the chamber (@LHO) before completion.

The Guralp cable has been pulled and put in the corner to the left of the water cooler:

Ben came by today before the cable had been pulled but he said he'll be back tomorrow.

Nodus' /export and /etc directories are now being backed up at /cvs/cds/caltech/nodus_backup

They will be rsync'd over as part of the nightly tape backups (scripts/backup/rsync.backup)

The nodus restart caused a bit of downtime. The apache configuration files were accidentally deleted the other day, so elog/svn/wikis were just holding on in memory; this fact was unfortunately not elogged. 

Things should be up and running again, except for the 8080->8081 elog redirection which I haven't been able to figure out.

I will also set up the NFS backup to include nodus configuration files from now on

Usual Ubuntu apt-get upgrades; long delayed but now happening.

[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.

I could not get Den's circuit to work for some reason with microphone input, so I decided to try to use another circuit I found online. I made some modifications to this circuit and made a schematic:

Using this circuit, I have been able to amplify microphone input and adjust my passband. Currently, this circuit has a high-pass at about 7 Hz and a low-pass at about 23 kHz. I tested the microphone using Audacity, an audio testing program. I produced various sine waves at different frequencies using this program and confirmed that my passband was working as intended. I also used a function generator to ensure that the gain fell off at the cutoff frequencies. Finally, I measured the frequency response of my amplifier circuit:

ampTest_03-08-2016_180448.pdf

A text file with the parameters of my frequency response and the raw data is attached as well.

These results are encouraging but I wanted to get some feedback on this new circuit before continuing. This circuit seems to do everything that Den's circuit did but in this case I have a better understanding of the functions of the circuit elements and it is slightly simpler.

Actually, if the power goes off and back on, the ethernet connection comes back online after about 5 seconds, or faster if it is disconnected and reconnected. The main issue was that the cable had partially slipped out (ie both power and network connections were loose); I suggest that the final setup should use ethernet cables that have a locking tab as this one does not. 

Ni plated SmCo magnets with specification of LIGO-C1103521-v2 for SOS ordered from Electron Energy Corp 

100 pieces of Ni- Platted magnets are in 9-27-2016 They are stored at clean cabinet S15

EP30-2 epoxy  1/2 pt kit 250 ml of part A and 25 ml of part B should be here in 7 days. These can packed epoxy is much more economical than the double barrel cartridges.

Spare SOS wire clamps will be out of the machine shop next week.

Lydia helped me to troubleshoot the Accromag connection problems which I was facing previously.  If power goes off/turned off manually, the ethernet cable has to be pulled out and put back again until only a non-blinking green light is observed. I was foolish enough that I did not use secure power connections. About the random symbol, a code block was not closed in the other supporting file which was being called in the main program. There are still some port errors and register errors, which I would work on later tonight.

Guralps as connected with pictures

ETMY UL epoxy soaking dish. All teflon in glass.

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.

[lydia, steve, ericq, gautam]

Summary:

• ETMX is now suspended by wire clamps (winches have been removed) 
• 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

I found the DAFI screen as a button inside of the LSC screen - I think its more logically found from the sitemap, so I'll move it into there as well.

Gautam and I noticed a 60 Hz + harmonics hum which comes from the DAFI. Its the noisiest thing in the control room. It goes away when we unplug the fiber coming into the control room FiBox receiver, so its not a ground loop on this end. Probably a ground loop at the LSC rack.

Upon further investigation we notice that the Fibox at the LSC rack had its gain turned all the way up to +70 dB. This seemed too much, we reduced it to ~20 (?) so that we could use more of the DAC range.  Also, it is powered by a AC/DC converter plugged in to the LSC rack power strip. We cannot use this for a permanent install - must power the FiBox using the same power supplies as are used for the LSC electronics. Probably we'll have to make a little box that takes the fused rack power of 15 V and turns it into +12 V with a regulator (max current of 0.15 A). Making sure that the FiBox doesn't pollute the rest of the LSC stuff with its nasty internal DC-DC converters.

We also put a high pass in the output filter banks of DAFI. For the PEM channels we put in a 60 Hz comb. WE then routed the Y-end Guralp in through the boxes and out the output, mostly bypassing the frequency shifting and AGC. It seems that there is still a problem with GUR2.

Does anyone know which one is GUR1 and which one is GUR2? I don't remember the result of the Guralp cable switching adventures - maybe Koji or Steve does. According to the trend it was totally dead before March and in March it became alive enough for us to see ~30 ADC counts of action, so way smaller than GUR111 or GUR snoopy or whatever its called.

There were many unknown and unsolved problems with using modbusApp for linux-arm architecture. So I tried to install the necessary files to setup Acromag Busworks card 1221-000 on Zita(192.168.113.217), which is a linux-x86_64 machine on the martian network. After installing a few dependencies and seting up few symbolic links for some libraries, everything is successfully configured. Initially I was unable to run myiocconfig.cmd file(as mentioned by Aiden on ATF wiki page) due to a undefined macro error for envset. Later I found that this error might be due to THIS bug in epics base. So, I removed the first four lines of that given code and directly referenced the .db file's location and it worked.

Now, I am facing another issue while running this file but on different line. Random symbols are returned on the last second line of the file each time I run it. I have attached the screenshots of those errors. I tried changing the encoding of the file several times but still it is showing the same error.

Gautam and Steve,

The clamp's left side was jammed onto the left guide pin. It was installed slit facing left. Gautam had to use force to remove it. The clamp should move freely seating on the guide rods till torque aplied. Do not move on with the hanging of optic with a jammed clamp. Fix it.

Never use force as you are hanging - aligning optic. The clamp is in the shop for resurfacing and slit opening.

I cleaned up the south Electronics bench today.

The other two, as well as several of the desks are in some chaotic state of degradation. Please clean up your areas and put away projects which do not need to remain staged for several months. Try to eliminate "that's not mine" and "I don't know who's that is" from your vocabulary.  Fight back against entropy!

[lydia, gautam]

Summary: Third unsuccessful attempt at getting ETMX suspended. I think we should dial the torque wrench back down to 1.0 N m from 1.5 N m for tightening the primary clamp at the top of the SOS tower. No damage to magnets, standoff successfully retrieved (it is sitting in the steel bowl)

Details:

• We burned through two sets of wires today.
• First, the assembly Eric and I had put together last night failed when Eric tightened the wire clamp (no torque wrench was used I think?)
• This afternoon, Lydia and I re-assembled the suspension once again. Standoff was successfully inserted, coarse pitch balancing was achieved relatively easily - we think that the coarse pitch balance can be achieved if the end of the wire standoff closer to the groove is ~0.5mm ahead (i.e. towards HR side) of the guide rod.
• Checked leveling of scribe lines, gave an extra 0.25 turns on the winches in anticipation of the wire sagging
• Inserted OSEMs just short of magnets, verified that they were approximately centered, if anything, slightly above center, again in anticipation of the wire sagging. 
• After taking pictures, we went ahead and attempted to clamp the wire (ALL EARTHQUAKE STOPS WERE ENGAGED)
• Eric commented that the clamp piece did not slide in smoothly on the dowels (indeed it does not come off very easily either, I have just left it on for now). I don't remeber it being so difficult prior to us sending it into the maching shop to get rid of the grooves made by the suspension wire the first time around. But with the torque wrench, the piece moved in relatively easily (we had sanded down rough edges prior to putting this piece onto the suspension earlier in the afternoon.
• I could feel that the torque wrench coming up on its limit. But the wire snapped before the torque wrench clicked. As far as I am aware, there were no rough edges on the piece, but perhaps we missed a spot?
• I took the opportunity to discharge the optic using ionized nitrogen at 40psi. After about 2-3 minutes of a steady stream, I verified that a piece of the suspension wire no longer gets attracted to the barrel, as was the case earlier today.

Unfortunately I don't know of a more deterministic way of deciding on a "safe" torque with which to tighten the bolts except by trial and error. It is also possible that the clamping piece is damaged in some way and is responsible for these breakages, but short of getting the edges chamfered, I am not sure what will help in this regard.

Unrelated to this work: earlier today before the first wire failure, while I was optimistic about doing fine pitch balancing and gluing the standoff, I set up an optical lever arm ~3m in length, with the beam from the HeNe on the clean bench at 5.5 in above the table, and parallel to it (verified using Iris close to the HeNe and at the end of the lever arm). I also set up the PZT buzzer - it needs a function generator as well for our application, so I brought one into the cleanroom from the lab, isopropanol wiped it. The procedure says apply 5Vrms triangular wave at 1000Hz, but our SR function generators can't put out such a large signal, the most they could manage was ~2Vrms (we have to be careful about applying an offset as well so as to not send any negative voltages to the PZT voltage unit's "External input". All the pieces we need for the fine pitch balancing should be in the cleanroom now.

I set up a test inverting amplifier circuit using the LT1677 opamp:

The input signal was a sine wave from the function generator with peak to peak amplitude of 20 mV and a frequency of 500 Hz and I received an output with an amplitude of about 670 mV and the same 500 Hz frequency, agreeing with the expected gain of -332k/10k = -33.2:

So now I know that the LT1677 works as expected with a negative supply voltage. My issue with Den's original circuit is that I was getting some clipping on the input to pin 2, which didn't seem to be due to any of the capacitors- I switched them all out. I set up a modified version of Den's circuit using a negative voltage input to see if I could fix this clipping issue:

I might reduce the input voltages to +5V and -5V- I couldn't get my inverting amp circuit to work with +12V and -12V. I'll start testing this new circuit next week and start setting up some amplifier boxes.

Unbaked steel music wire from  "Ca Fine Wire Co" from 24" od spool, od 0.0017" used. Identical to the one that broke.

The set up as shown with silver plated screws-washers on clamp. The unused clamp edges were sanded on P800 paper at 45 degrees just not to be very sharp.

Use your finger to feel the sharpness of  edge and sand till it gets a little bit not so sharp. The drawing note is "sharp edges" on wire clamp for low loss, high Q in mind.

The wire broke at the midle with single load 295 grms

The wire hold on overnight at single load 242 grms  Vezo torque wrench is not accurate!  This test was performed ~ 1.5Nm  DO NOT USE THIS NUMBER! (added at 8-10-2016)

This gives us a factor of 2 safety  with loop suspended of 250 grms small optic.

While the air bake oven situation is being improved, how about to buy a cheepo toaster oven at Target, BestBuy, or anywhere?

We don't need precise temp control for the glue cure test. At LLO I saw that they are using cooking grade oven for this purpose.
(Of course, we should not use this oven for foods once it is used for epoxy)

I have a fryer temp sensor in my office on the freezer stole from the 40m long time ago. You should be able to measure high temp.

If you have such an oven, I'd love to borrow it for the OMC lab later, as I expect to work on epoxy bonding later.

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

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

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

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

I tried to recompile the modbusApp binary for linux-arm acrhitecture since I suspected someting wrong with it. But still the problem persists; I can connect to acromag but cannot access the channels. I have also reconfigured new acromag bus works terminal XT 1221-000 and I want to test if I could access its channels. My target is to complete this acromag setup work before sunday morning so that I can focus towards having some useful results for my presentation.
 

[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. 

I'd recommend replacing the wire and grinding down the clamp to prevent cutting the wire. Since we have almost never replaced clamps, many of them probably have grooves from the wires and can make unpleasant cuts. Better safe than sorry in this case.

While ETMX magnets were curing, I wanted to try and suspend ETMY in the endchamber, put in the OSEMS and see if the magnets aligned well with the coils, and run the same type of diagnostics we have been doing for ETMX. However, while I was trying to slip the optic into the wire, the UL magnet on ETMY broke off. I recovered the magnet and now both optic and magnet are back in the cleanroom. The magnet dumbbell has been cleaned with acetone and then sandpaper to remove residual epoxy - it remains to clean the residue off the optic itself before re-gluing the magnet tonight

I also noticed that the existing wire in the suspension had a kink in it. It looks fairly sharp, and I think we should change the wire while re-inserting the optic. Putting the optic into an existing loop of wire is tricky, as if you go in from the front of the suspension cage, the magnets on the AR side attract the wire, and makes it quite difficult to loop the wire around. I have to think of some way of holding the wires in place while the optic is being placed, and then, once the optic is roughly in position, slip the wire into the grooves in the standoffs. 

I took the opportunity to replace the face OSEM coil holder screws while the chamber was open. 

EDIT 9 August 2016: It was in fact the LR magnet that was knocked off.

I took some pictures with the digital microscope of the aluminum standoffs removed from ETMX. The first one had some leftover epoxy still attached, so I was able to distinguish which part of the groove was occupied by the wire. A better microscope would help (this one has a maximum magification of 80, 200 or so would be much better) but I was still able to see what looks like a second minimum inside the groove at the wire location (see Attachments 1 and 2). The bottom edge of the standoff shows the profile of the groove on the opposite side from the glue. I took several photos with different lighting angles and at different locations on the microscope stage and convinced myself that this was not just an artificial effect. I also took photos of the groove in a different place and did not see this feature (Attachment 3).

The other standoff in the same container had no visible damage to the groove or to the body of the rod. I rotated it under the mocroscope and could celarly see the 'V' shape all the way around. The smooth undanaged groove caught the light more easily and was obvious. The damaged one is scratched around much of the surface, but the undamaged standoff is very smooth. Eric, were both aluminum standoffs in the container with the extra ruby one taken off ETMX, or was one of them new? in any case, see Attachement 4 for a comparison. The believed damage is somewhat visible on the top edge of the lower standoff in the photo. 

[Edit:] Also, in the drawings it looks like the specified radius for the bottom of the groove (0.001 in) is smaller than the radius of the wire (0.00085 in). This would prevent having two clean points of contact like Steve and Gautam were describing as the goal. This is also true of drawings for the new Sapphire guiderods, though the dimensions are in metric units the specified radius of the groove bottom is smaller than the wire's diameter, but larger than its radius. Maybe this providied the initial ability for the wire to move around and carve two distinct grooves. 

Attachment #1 - After multiple trials shimming the magnet gluing rig with teflon spacers, we think that we managed to find a configuration in which the side magnet edge is between 0.25 mm and 0.5 mm from the groove in the ruby wire standoff in which the wire will sit. 

Attachment #2 - Zoomed in view of the side magnet.

Of course we won't know until we suspend the optic, but we believe that we have mitigated the misalignment between the side OSEM axis and side magnet.

The short term plan is to try and suspend ETMY in the end chamber and have a look at the alignment between all magnets and OSEM coils for it. Once the epoxy on ETMX is cured, we will try and suspend the optic again, this time taking extra care while tightening the wire clamps.

Unrelated to this work: Bob just informed me that we had left the air bake oven on overnight - this unfortunately melted the plastic thermocouple inside.

The clamp is in the machine for milling off the grooves. It's condition is normal. The edges needs some 800 sand paper so it is not sharp anywhere.

How did those nicks get on the edge? Fortunatelly they did not aligned with the wire.

[gautam, ericq]

Brief summary, some pictures and such follow in the daytime. 

• All magnets enclosed by OSEMS were knocked off. (This means one side magnet remained, on the guiderod side)
• Glue residue cleaned from ETMX
• Dumbbell feet were cleaned of glue, finely sanded, re-scored with a razor blade
• The magnet gluing fixture was painstakingly aligned multiple times, adjusting the shim height to get a magnet/wire groove clearance of 0.25-5mm
• Epoxy mixed, test batch cured perfectly, applied to 5 dumbbells (after triple-checking polarities) and set to glue. 

The epoxy needs at least 12 hours of room temperature air curing, so no touchy until 3:30PM on Jul 28!

I recreated Den's microphone amplifier circuit on a solderless breadboard to test it and make sure it does what it's supposed to. So far it seems like everything is working- I'll do some testing tomorrow to see what the amplified output is like for some test noises. Here's the circuit diagram that Den made (his elog as well https://nodus.ligo.caltech.edu:8081/40m/6651):

I'm not sure why he set up the circuit the way he did- he has pin 7 grounded and pin 4 going to +12V while in the datasheet for the opamp (http://cds.linear.com/docs/en/datasheet/1677fa.pdf), pin 7 goes to positive voltage and pin 4 goes to negative voltage. There's some other strange things about the circuit that I don't really understand, such as the motivation for using no negative voltage source, but for now I'm going to stick with Den's design and then make some modifications after I have things working and a better understanding of the problem.

Here's my current plan:

-Make sure Den's amplifier works, test it out and make changes if necessary

-Make multiple amplifier circuits on soldering breadboard

-Either make a new amplifier box or reuse Den's old box depending on how many changes I make to the original circuit

-Solder EM172s to BNC connectors, set them up around the floor suspended

-Get the amplifier box hooked up, set up some data channels for the acoustic noise

-Add new acoustic noise tab to the summary pages

Den also mentioned that he wanted me to measure the coupling of acoustic noise to DARM.

For the rest of this vent, at least, we need to start using the EQ stops more frequently. Whenever the suspension is being worked on clamp the optic. When you need it to be free back off the stops, but only by a few hundred microns - never more than a millimeter.

Best to take our time and use the stops often. With all the magnets being broken off, its not clear now how many partially cracked glue joints we have on dumbells which didn't completely fall off.

While tightening the bolts on the ETMX wire clamp, the wire broke. All four face magnets broke off. 

Fortunately, no pieces were lost.

               July 27, 2016             2  new 1103P from Edmonds in: P947034 & P947039, manf. date April 2016,

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. 

We have no number for the CFM without calculation. We can't assume a random number like 10-15

Thanks for checking this out Koji

The builder in 1996 was Process System International, Inc ( Westborough, MA ) It does not exist any longer or I just could not find them. Flow diagramm at Atm1

Should I be keep looking for a company who could quote us for building a similar smaller unit with 10 - 15 cfm flowrate?

Note: my intension with the two mobile-overhead HEPA filter was the same as John Worden's " clean air overpressured tent " at chamber entrance.

Atm2, Our unit has 650 cfm, velocity 90 fpm at resistance 0.5"    It may be enough to give a little overpressure if we seal it well to the chamber

We use to use them to minimize dirt getting inside the chanbers.

I've visited the purge clean air system at LHO Yarm mid-station with John Worden.

The system is described C981637. There is a schematic in C981637-06-V (Vol.6).pdf although the schematic has some differences (or uncorrected mistakes).

This system is intended to provide positive pressure when a soft cover is attached to a chamber door. When the door is open, the purging does not help to keep the chamber clean because the flow is too slow. This protection has to be done with overhead HEPA filters (22x5000cfm). It may be possible that this purge air helps the tube not to allow dusts to come in. But before using this, the chambers and the tubes have to be cleaned, according to John.

- Here at the site, the purge air system is started up a day before the vent. This system is used for the vent air, the purge air, and turbo foreline filling.

- Air intake (attachment 1): At the site, the air is intaken from the VEA. We want to incorporate somewhat clean air instead of dirty, dusty, outside air.

- Initial filter (attachment 2): a high volume filter before the compressors.

- The compressors (attachment 3, 4) are 5x 6 horse power air compressor each goes up to 160 psi. They are turned on and off depending on the demand of the air. Which is turned on is revolved by the controller to equalize the compressor usage hours.

- The compressed air goes through the air cooler (heat exchanger) to remove the heat by the compressor work.

- This air goes through prefilters and accumulated in the air receiver (100psi) (attachment 5). This receiver tank has an automated vent valve for periodical water drainage at the bottom.

- The accumulated air is discharged to twin drier towers (attachment 6, blue). The tower is operated by the controller (attachment 7) alternately with a period of 4min (or 10min by setting). When one of the towers is working, a humid air comes from the bottom and the dry air is discharged from the top. A part of the dry air goes into the other tower from the top to the bottom and dries the tower. There is a vent at the bottom to discharge water periodically.

- The dried air goes through 4 types of filters. After the last filter, all of the plumbing should be made of stainless steel to keep cleanliness.

- The air goes to the pressure reducing regulator (attachment 8, gray). The final flow speed at the chamber side is 50cfm max, according to John.

- The lower pressure air goes through the final filter (attachment 8, blue). As the pressure is low, this filter is big in order to keep the volume of the air flow.

- The purge air is supplied to the chamber side with KF50 (attachment 9). There is a vent valve (attachment 10) for safety and also to run a dry air for at least a day before the use to clean up the supply line. The purge line is disconnected when no in use.

- The entire system (attachment 11) and size comparison (attachment 12).

c1susaux (which controls watchdogs and alignments for all non-ETM optics) was down, the last BURT was done yesterday around 2PM. 

I restarted via keying the crate. I restored the BURT snapshot from yesterday.

[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. 

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

Ugh. 

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.

(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.

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.

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.

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.

[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.

Please find the new attached plots and the new script.

[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.