I didn't have a separate training set and data set, so I think that's why the graphs came out looking too good. The units on the graphs are also incorrect, I was interpreting PSD as ASD. I haven't been able to get my Wiener filtering code working well- I get unreasonable subtractions like the noise being larger than the unfiltered signal, so Eric showed me this frequency-dependent calculation described here: https://dcc.ligo.org/LIGO-P990002

This seems to be working well so far:

freq1.pdf

freq2.pdf

freq3.pdf

Here's all the plots on one figure:

frequency_dependent.pdf

Let me know if this looks believable.

This elog is meant to summarize my numerical simulations for looking into the effects of curvature on the RC mirrors. I've tried to go through my reasoning (which may or may not be correct) and once this gets a bit more refined, I will put all of this into a technical note.

Motivation: 

• Both the G&H (PR2, SR2) and Laseroptik (PR3 SR3) are convex on the HR side with RoCs of approximately -600m and -700m (though as stated in the linked elog, I'm not actually sure if there are measurements of this number) EDIT AUG15: There are measurements for the Laseroptik mirrors here
  GV April 8 2017: This elog by Jenne suggests that the installed PR2 has an RoC of approximately -700m. Koji has uploaded the phase map data for the RC TT mirrors to /users/public_html/40m_phasemap/40m_TT and /users/public_html/40m_phasemap/40m_TT2. The G&H mirror data seems to be in the former folder, and it looks like there are two mirrors, one with RoC of ~ -700m and the other with RoC of ~ -500m. Does this mean PR2 has RoC -700m and SR2 has RoC -500m?
• As a result, both the PRC and SRC were close to instability
• By flipping the folding mirrors, the instability has been mitigated, but at the expense of the non-ideal situation where the AR coated side and the substrate are now inside the recycling cavity
• We would like to order some new folding mirrors. In order to avoid receiving convex mirrors from the vendor, we want to specify a concave curvature for the HR side
• The aim of this investigation is to look at how concave we should make these mirrors, because although the cavity stability improves with concavity of the HR side, possible disadvantages of having too convex mirrors are:
  • ​Mode-mismatch between the recycling cavities and the arms
  • Astigmatism

The study:

• I've built a Finesse model for the 40m, which has been used for all the numerical studies quoted here
• In constructing this Finesse model, I've used the following sources to specify various paramaters:
  • ​RoCs, R, T and physical dimensions of 4 test-masses, PRM, SRM and BS: Core optics wiki page
  • Losses - arm losses from Yutaro's measurements in elog11857 and elog11818 (distributed equally between ITM and ETM). For other optics, a generic value of 25ppm was used
  • "Ideal" lengths for our current modulation frequency were used for the various cavities (37.795m for the arms, 6.753m for PRC, 5.399 for SRC)
  • The folding mirrors (PR2, PR3, SR2, SR3) are initialized as flat in the model
• I performed some low-level checks (e.g. arm linewidth, PRC FSR etc) to check that the model was sensible
• I then proceeded to investigate the effects of curvature on the folding mirrors. Specifically, I investigated the following:
  • What is the mode mismatch between the recycling cavity mode and the arm as a function of the RoC of the folding mirror?
  • What is the effect of the RoC of the folding mirrors on the round-trip gouy phase accumulated (and hence the transverse mode spacing) in the recycling cavities?
• For now, the parameter space explored is from 300m concave to 1000m concave. An RoC of 1km for a 2" optic corresponds to a sag of ~0.3 microns. I will explore the 1km-10km concave space and update the results shortly

Results:

• Attachments #1 and #2 show the mode mismatch between the recycling cavity and the arm for various curvatures. The colorbars have been normalized to span the same range in all the plots
• For both the PRC and the SRC, if we have folding mirrors with an RoC of 1000m concave, we will have a mode mismatch of 2-3%. The number gets worse the more convex the mirror
• Attachments #3 and #4 show the one-way accumulated Gouy phase. Here, I have varied the curvature of the folding mirrors along a specific axis at a time (i.e. I've assumed that the folding mirrors are identical). I've also added the transverse mode spacing as a second y-axis. I have yet to check how these numbers compare with the linewidth of the 00-mode for the various fields, but for 1km concave folding mirrors, the TMS is in the region of 2MHz 

To do:

• I will extend the range of RoCs explored to 10km concave and post results - but I will have to check with EricG to make sure that it is feasible for us to specify curvatures in this range
• I was trying to use the RT gouy phase as calcluated by my Finesse simulations to plug into some analytical expressions to try and generate plots like this for various RoCs of the folding mirrors, but if the TMS calculations suffice, I will abandon these efforts
• What are the other specifications we need to worry about before placing an order? Some thoughts from Rana's earlier elog:
  • The coatings need to be dichroic to allow extraction of the green beam (but only PR3/SR3 is currently dichroic?)
  • Wedge angle on the AR side?
• Are there any other obvious sanity checks I should carry out?

Seems to good to be true. Maybe you're over fitting? Please put all the traces on one plot and let us know how you do the parameter setting. You should use half the data for training the filter and the second half for doing the subtraction.

I used the Wiener filtering method described by Ignacio and Jessica (https://dcc.ligo.org/DocDB/0119/T1500195/002/SURF_Final.pdf and https://dcc.ligo.org/public/0119/T1500194/001/Final_Report.pdf) and got the following results:

mic1_wiener.pdf

mic2_wiener.pdf

mic3_wiener.pdf

The channel readout has a gain of 0.0005 and the ADC is 16-bit and operates are 20V. The channel also reads the data out in Pa. I therefore had to multiply the timeseries by 1/0.0005=2000 to get it in units of counts and then by (20 Volts)/(2^16 counts) to get back to the original signal in volts. The PSDs were generated after doing this calibration. I also squared, integrated, and square rooted the PSDs to get an RMS voltage for each microphone as a sanity check:

Mic 1: 0.00036 V

Mic 2: 0.00023 V

Mic 3: 0.00028 V

These values seem reasonable given that the timeseries look like this:

timeseries_elog.pdf

2.1 mag earth quake in Norhten Ca

Our seimometers need professorial centering. Related electronics must be checked too.

The results of my first huddle test were not so good- one of the signals did not match the other two very well- so I changed the setup so that the mics would be better oriented to receive the same signal. Pictures of the new setup are attached.

I also noticed some problems with one of my microphones so I soldered a new mic to bnc and switched it out. Just judging from Dataviewer, the signals seem to be more similar now. I'll be taking data for another few hours to confirm.

I needed to move the pitch slider on the IFO align screen to -2.10 (V?) from 0 to get the HeNe spot to the center of the iris. The slider runs from -10V to 10V, so this is something like 10% of its range. I am not sure if it means anything, but the last saved backup value of this pitch slider was -3.70. Of course, application of the bias will affect all the coils, and when the optic is pitch balanced, the lower magnets are a little too far out and the upper magnets are a little too far in (see Attachment #1), as we expect for a downward pitch misalignment to be corrected. I suppose we can iteratively play with the coil positions and the bias such that the coils are centered and we are well balanced (maybe this explains the old value of -3.70). 

I also checked that the side magnet can completely occlude its PD. With the damping on, by pushing the coil all the way in, the output of the side PD went down to 0.

The summary pages have been updated with the new naming seismometer channel naming conventions. Here's a link to them working on my own page: https://ldas-jobs.ligo.caltech.edu/~praful.vasireddy/1154908817-1154909717/pem/seismic/
 

Let me know if the actual pages aren't working when they come back online or if there's something that needs to be changed.

How much pitch bias do you need in order to correct this pitch misalignment?
That may give you the idea how bad this misalignment is.

Summary:

• ETMY has been re-suspended
• Reglued magnets (and also those that weren't knocked off) quite well with OSEM coils (see attachments)
• Pitch balance is off by ~2.8mrad (8mm over 1.5m lever arm) after inserting and centering OSEMs
• The same damping scheme used during the ETMX re-suspension process works reasonably well with ETMY as well

Details:

• I suspected that I had not tightened the wire clamp enough yesterday, and that the wire had slipped once the winches were removed
• Steve and I looked into the torque wrench situation today, and I realised that I had not been using the torque wrench correctly. What I thought were clicks indicating that the set torque has been reached was in fact just the sound the piece makes when going the opposite way relative to the direction set by the clip on the torque wrench. Anyways, the point is that while I thought I was tightening the screws with ~1.3Nm of torque, what was actually being applied was much less (although I don't have a good way to quantify how much less)
• So today I put the winches back on top of the tower, and winched the optic back up to the correct height using the ususal scribe line + microscope prescription
• I then tightened the wire clamp by hand. This is obviously not very repeatable, but it will have to do until we get a torque wrench with the correct range
• This seems to have done the trick - I did the tightening shortly after lunch, and after ~10 hours, there is no evidence of any wire sag
• I then proceeded to insert the OSEMs, first not all the way in to check the clearance available to the magnet, and once I was satisfied there was no danger of knocking anything off, went ahead and inserted the coils till the PD readouts were approximately half of the maximum (i.e. fully un-occluded) values. I used the OSEM coils originally on the ETMY tower, but all the other readout and drive electronics in the signal chain (satellite box included) belong to the ETMX setup (so as to avoid any cable routing over 80m from the Y end to the cleanroom). After some adjustment of the OSEM holding plates, I was able to center the magnets relative to the coils 
• The tower only allows for a side OSEM to be inserted on one side. The other side does not have a threaded hole for a set screw. So we are forced to use the reglued magnet and not the side magnet that was not knocked off. By eye, it looks like the magnet may never completely occlude the LED, but the Striptool trace I was using to monitor the output of the PD did not yield any conclusive evidence. The optic was moving around a lot and I did not perform this check after turning the damping on
• I was able to damp the optic as well as we were able to damp ETMX on the clean bench (with the HEPA turned OFF). I had to turn the YAW gain down from 100-->75 to avoid some oscillations 
• I then proceeded to check the pitch balance with the HeNe. The spot is low on an iris 1.43m away by ~8mm, which corresponds to a pitch misalignment of ~2.8mrad. I am not sure what to make of this - but perhaps its not unreasonable that we see this? Is there any record of what fine pitch balancing was achieved when the optic was put together back in 2010? This is also very sensitive to how far in/out the OSEM coils are, and though I've tried to center the coils as best as I can, I obviously have not done a perfect job...

What's next?

• Is the observed pitch imbalance a deal breaker? If so, I guess we need to re-glue a standoff? 
• Are we willing to accept the side OSEM situation? (Tomorrow, I need to do a check to see what, if any, dynamic range we lose, with the damping on)
• If both the above are not problems we need to worry about, then:
  • ETMY + ETMX -------> Vacuum bake on 22nd August (? - Bob also told me earlier today that he will try and put in some old turbo pump next week, and if that works, we could possibly get in the queue even before the 22nd)
  • ETMY tower -------> Steve for sanding and removing wire grooves -------> Air bake
  • ETMX tower -------> Air bake (provided the latest round of wire tightening has not left any grooves in the top piece of the tower, if it has, this needs to be cleaned up too)
  • Some lengths of SOS wire (for re-suspending optics after bake) -------> Air bake

Attachments:

Attachment #1: Striptool trace showing all OSEM coils have been pushed in till the PD readout is approximately half the fully open value

Attachment #2: Pitch balance is off by ~2.8mrad (the Iris center is 5.5" above the table)

Attachment #3: UR magnet

Attachment #4: UL magnet

Attachment #5: LR magnet

Attachment #6: LR magnet

Attachment #7: SD magnet

In order to help Praful do his huddle test, I have temporarily arranged for the outputs of the 3 channels he wants to monitor to be acquired as DQ channels at 2048 Hz by editing the C1PEM model. No prior DQ channels were set up for the microphones. Data collected overnight should be sufficient for Praful's analysis, so we can remove these DQ channels from C1PEM before committing the updated model to the svn. There is in fact a filter that is enabled for these microphone channels that claims to convert the amplified microphone output to Pascals, but it is just a gain of 0.0005. 

In the long term, once we install microphones around the IFO, we can update C1PEM to reflect the naming conventions for the microphones as is appropriate.

I set up 3 of my circuits in the interferometer near MC2 to do a huddle test. I have the signals from my microphones going into C1:PEM-MIC_1_IN1, C1:PEM-MIC_2_IN1, and C1:PEM-MIC_3_IN1. These are channels C17-C19. Here are some pictures of my setup:

I'll likely be collecting data from this for a couple of hours. Please don't touch it for now- it should be gone soon. There are some wires running along the floor near MC2 as well.

[ericq, Lydia]

We changed the seismometer channel names from, e.g. C1:PEM-SEIS_GUR1_X to C1:PEM-SEIS_EY_X.

• GUR1 referred to the seismometer at the Y end, GUR2 referred to the seismometer at the X end, and STS1 referred to the seismometer at the vertex. These have been renamed EY, EX, and BS respectively in all channel and filter names. 
• The models for c1pem and c1oaf were changed in Simulink. The DAQ boxes were also updated with the new names. The script which forcibly renames channels saved to disk was edited to no longer refer to the GUR1, GUR2 etc channels. Going along with what Rana suggested we decided not to change the names of the renamed channels this way when saving, so the data saved from the seismometers can be found under e.g. C1:PEM-SEIS_EY_X_OUT_DQ. 
• The filter files generated by Foton were changed to reflect the new channel names. 
• We compiled the changes to the models and restarted the models on the relevant machines (c1lsc for the c1oaf model and c1sus for the c1pem model). c1sus_aux was down so we manually restarted it to turn off the watchdogs as a precaution before putting too much strain on c1sus. 
• The MEDM screens now show the correct information, relabeled with the new names under PEM-RMS. 
• The striptool display projected on the wall now shows the appropriate C1:PEM-RMS_BS channels and has been renamed to "SeismicRainbowBS.strip" 
• We verivied that the new channels can be accessed live and the data from the DQ channels is saved to disk. 
• After the changes were complete, we attempted to commiting to svn (the commit also included bringing the MEDM screen files into version control.) However the svn server was taking a long time to respond, so we will try again tomorrow to commit the file changes. 
• There are still some lefotver unused channels with name sinculding STS_2 and STS_3 that refer to seismomters we no longer use. We left these alone. 

Summary of new channel names:

C1:PEM-RMS_{BS, EX, or EY}_{X, Y, or Z} followed by the same filtering options as before, e.g. _BP_1_3_OUT

C1:PEM-SEIS_{BS, EX, or EY}_{X, Y, or Z}_{EXC, IN1, IN2, OUT, or OUT_DQ} 

C1:OAF-WIT_{BS, EX, or EY}_{X, Y, or Z}_{EXC, IN1, IN2, or OUT} 

The 7.5 in-lb of Wiha seems at the upper end of torque range for a 4-40 SS screw

Wiha 28502 ordered with range 5 -10 in-lb for silver plated 4-40 screws

Do not trust the Venzo torque wrench under 2 Nm ! It miss lead me.

Recommended torque values for silver-plated fasteners are here. For aLIGO we use the guidelines in T1100066-v6, This doc is posted in 40m wiki under Mechanics also.

So, we'll use 6 in-lbs  on silver plated 18-8 stainless steel socket head cap screw 4-40 x 3/8 into SS tower bridge.

Please replace these clamp screws every time if they were tightened without a torque wrench.

The saga has started here  We have to give credit to the Boss who fixed it. The seismometers themself are not labeled yet.

Atm6  added on 8-12-2016   EX needed to be centered

Thanks to Max for the nice plost at summery pages

[lydia, gautam]

Rana felt it was alright to use the wire clamp and suspension cage in its existing condition for checking the ETMY magnet-OSEM coil alignment. So we set about trying to re-suspend ETMY. The summary of our attempts:

• Transferred optic from magnet gluing rig to the suspension cage
• Adjusted bottom EQ stops till the scribe lines on both sides were at 5.5" as verified with the microscope
• Looped cleaned length of wire around optic, attached free ends to winches, placed the wires under light tension by finger-pulling the slack out
• Lowered the bottom EQ stops
• Winched the optic to the right height
• Clamped the wire with the only wire clamp on this variant of the suspension cage. We used the same torque wrench at the same torque setting as was successful for ETMX. But after removing the winches, and releasing the face EQ stops, the optic seems to have sagged a lot - it now touches all the bottom EQ stops, and the more I lower it, the more it seems to come down. Perhaps it is the effect of the wire grooves in the cage, or that the wire-clamp itself is slightly different from the piece used on the ETMX cage, but 1.3Nm of torque doesn't seem to have tightened the wire clamp sufficiently
• We can still probably salvage the situation by re-attaching the winches to the top of the cage, setting the optic to the right height again, and clamping the wire clamp with more torque (as this is just a check to see that the reglued magnet configuration is compatible with the OSEM coil positions on the cage). Before air baking the cage, we will have the old wire grooves removed, and then suspend the optic with a fresh loop of wire after the bake
• We could not check the magnet-OSEM alignment because of the slipping of the wire through the clamp. We decided against pushing on tonight
• Optic is currently in the cage, resting on the bottom EQ stops and with all face EQ stops within 1mm of the optic. The OSEM coils have not been inserted into the holders

Regarding the vacuum bake of the optics: why do we want to do this again? Koji mentioned that the EP30-2 curing process does not require a bake, and there is also no mention of requiring a vacuum bake in the EP30-2 gluing guide. Is there any other reason for us to vacuum bake the optic?

After some cable swapping, we now have both Guralp seismometers running and the times series and spectra look similar to each other and motley healthy.

Bean and I took a look at the whole situation today. Ben had nicely fixed the Dsub end of the EX cable (the EY one is still just a sad joke), After installing this newly fixed cable, we still saw no signals. There was some confusion in the control room about using the MED displays to diagnose seismometers: flickering MEDM values cannot be used for this. It would be like checking a pizza box temperature to determine if the pizza is any good.

1. Although the +/- 12V LEDs on the front panel are dim, we confirmed that the produce 11.94V even when loaded with a seismometer. So its a LED circuit problem not a power problem.
2. We were able to inject signals into the front panel with a breakout board and see them in DV for Input 1, but not Input 2.
3. After Ben left, I kept poking around and found that the Guralp chassis output gets broken out into 3x3 BNC cables before going to the PEM BNC panel (and then on to the PEM ADC). This is where the problem was.
4. The Input #3 BNC cables were connected to the long cables going to the 'GUR2' channels of the PEM. The Input#2 BNC cables were connected to some short BNC cables that were just hanging from the rack. So, somewhere during the debugging of the past N months, someone plugged this in wrong and didn't notice or forgot to switch it back. So all of the tests using DV or DTT or MEDM since that time have been invalid.

Tomorrow, Lydia is going to change all of the labels and channel names. The new names will be EX & EY to prevent this kind of huge waste of time with channel name swapping. That means no more illegal names with the label maker, Steve.

From the spectrum you can see that the EX seismometer (GUR2) is still not centered or at least its oscillating at 245 Hz for some reason. This should go away after some power cycling or recentering using the magic wand.

I noticed some anomalies in the mechanical setups at the ends:

1. Some junk has been stored on top of the EX seismometer. Please never, even temporarily, store your power supplies, tools, or donuts on top of the vibration sensitive sensors. Just put it on the floor and improve your carma.
2. The EY seismometer has some fishy wires being fished between the can and the rubber seal. This is verboten. That seal must be flush to prevent pressure fluctuations and wires in there will ruin the smooth contact permanently. Temperature sensor wires must go through the grantie block feed-through or else its pointless.
3. The flimsy insulation on the EY seismo is waay toooo mickey mouse. Real thermal insulation should be done using the yellow foam that Jenne used for the seismo huddle test. This flimsy silvery stuff is OK for making hats and mittens and beer cozy's, but its not research grade foam.

New Wiha 28504 torque wrench for SOS wire clamping. It's range 7.5  - 20 in-lb in 0.5 steps [ 0.9 - 2.2 Nm ] Audible and perceptible click when the pre-set torque has been attained at ±6% accuracy.  

The new ETMX sus wire torqued to ~ 11.5 in-lb [1.3 Nm ]

The Guralp cable has been reconnected and powered after having the connector changed out.
 

The pickle pickers came off nicely and both magnets seem to be glued on okay. The alignment of the face magnets look pretty good, but we will only really know once we suspend the mirror, check the pitch balance, and put in the OSEM coils.

I brought the ETMY suspension tower + OSEM coils out of the vacuum chamber into the cleanroom. Given that the old wire had a pretty sharp kink in it, I removed it with the intention of suspending the optic with a new length of wire. I noticed a few potential problems:

Attachment #1 - ETMY tower is different from ETMX tower: 

• The ETMY suspension seems to be of an older generation - it does not have the the two secondary wire clamps. 
• The top piece was attached to the body of the tower using non-silver-plated screws. Steve tells me this is the wrong type, and we can switch these out when we put it back together.
• The wire clamp itself doesn't have much of a groove from the wire. But the wires have made asymmetric grooves in the tower itself (the left groove is deeper than the right as seen in Attachment #1), that are clearly visible. Should we get these grooves removed before attempting re-suspension? How do we want to remove it? Steve thinks the best option is to send it to the shop for milling, as there is hardly any room to rub sandpaper along the piece because of the pins, and these pins don't come out. 
• Or do we just not care about these grooves for now, if we are planning to use new wire anyways after air-baking the towers? 
• Steve thinks we should have a few spares of these top blocks handy (the latest version, with the secondary clamps), he wants to know if we should place an order for these (we already have 10 spare wire clamp pieces available for if/when we need them)

Attachment #2 - the base of the tower is significantly rusty:

• A few wipes with an acetone soaked rag yielded quite a lot of rust
• Steve thinks this is because the wrong type of stainless steel was used
• Does this have to do with the cage being of an older variety? After a few vigorous wipes, no more rust came off, but the rusting process will presumably keep generating new rust? Is this a concern? Do we want to change this piece before putting the tower back in?

I am holding off on attempting to re-suspend the optic for now, until we decide if the old wire grooves need to be removed or not. If we are okay with re-using the same piece as is, or if we are okay with using sandpaper and not the machine shop to remove the grooves, I will resume the re-suspension process. 

Eric suggested another alternative, which is to use the old ETMX tower. I don't recall it being rusted, but this has to be checked again. The other problem of the wire-grooves would possibly still be an issue.

Regarding the vacuum bake of the ETMs, Bob tells us that the best case scenario we are looking at is September.

I checked out the cable that I took from you, and all of the connections looked right.  The only thing I did notice was that some of the soldered wires on the 37-pin connector had gotten hot enough to melt their insulation, and potentially short together.  I cut off that connector, and left it on your desk to check out.  I put on a new connector, and checked the pinout.  If the Guralps still doesn't work, we'll have to check out other possibilities.

Summary:

Given that ETMX looks to be in good shape and the optic and suspension tower are ready for vacuum and air bakes respectively, I set about re-gluing the knocked off magnet of ETMY. In my previous elog, I had identified the knocked off magnet as the UL magnet. But in fact, it was the LR magnet that broke off. This is actually one of the magnets that was knocked off when Johannes was removing the optic from the vacuum chamber. I have edited the old elog accordingly. 

Step 1: Removing epoxy residue

• I used the teflon+glass rig Steve put together for this purpose
• After soaking for ~2 hours in acetone, I was able to remove approximately half of the ring residue by lightly pushing with a wipe.
• The other half wouldn't budge so I let it soak for another 4 hours
• After 6 hours of soaking, I was able to get all of the epoxy residue off - it doesn't simply dissolve in the acetone, I had to push a little with one of the cotton-tipped paddles in the cleanroom
• I gave the portion exposed to acetone a quick drag wipe with isopropanol. I didn't spend too much time trying to clean the AR side given that we will be using first contact anyways.
• I have not touched the HR side for now, even though a small portion of it was exposed to acetone. While cleaning the HR face with first contact, this portion can be inspected and cleaned if necessary

Step 2: Putting the optic in the magnet gluing jig

• I transferred the optic to the magnet gluing jig
• Given that we weren't touching any side magnets, I reasoned I did not have to go through the elaborate shimming routine to account for the wedge of the optic that we had to do in the recent past
• However, I did not think to put a thicker teflon spacer on the lower side of the wedge, and as a result, I knocked off the UR magnet as well as the jig did not have sufficient clearance
• Fortunately, the UR magnet came off cleanly, there was hardly any epoxy residue left on the optic. The UR magnet was NOT one of the magnets knocked off by Johannes while removing the optic from the vacuum chamber
• I gave the area formerly occupied by the UL magnet 3-4 wipes with acetone and then 1-2 wipes with isopropanol
• At this stage, I proceeded to re-insert the magnet-gluing jig. I used the two scribe lines on the outer side of the jig to fix the rotation of the jig, and used the remaining two attached face magnets to fix the overall position of the jig (by centering these magnets relative to the apertures on the jig). In order to center well, I had to unscrew the stuck silver plated screw on the jig by 1 turn
• Having arranged the jig satisfactorily, I proceeded to remove epoxy residue off the dumbbell of the recently knocked off UL magnet using first a razor blade, then sandpaper and finally made some new grooves with a razor blade. I then cleaned the surface of the dumbbell to be in contact with the optic with isopropanol. All of this was done for the LR magnet two weeks ago right after it was knocked off

Step 3: Gluing the magnets

• I prepared the magnets in the pickle pickers
• I discarded 1 full squeeze of the epoxy after it reached the tip of the mixing fixture, and then extracted another full squeeze of the gun for mixing and gluing the magnets
• I mixed the epoxy in an Al foil vessel for 3-4 minutes, and then placed a few drops on a piece of Al foil for a test bake at 200F for ~15 minutes
• The test bake went well, so I proceeded to apply glue to the dumbbells and re-glue the magnets to the optic
• The gluing was done around midnight, so we should be able to have a look at this post lunch tomorrow.

Provided the gluing goes well, the plan for tomorrow is:

1. Bring ETMY suspension tower from the vacuum chamber to the cleanroom along with its OSEMs
2. Suspend ETMY with a new length of wire (this should be much more straightforward than our ETMX exploits as both standoffs are already glued)
3. Insert OSEMs, check that all 4 face magnets are well centered w.r.t. their coils and also that at least one side magnet is well aligned relative to its coil and can be used 
4. If step 3 goes well, then ETMY is also ready for a vacuum bake. I guess we can also air bake the ETMY suspension tower, there's plenty of room in the oven

I came in to check on ETMX. I freed the earthquake stops, and found that the OSEMS were reasonably, but not perfectly, centered. Turning on the damping, I found that the pitch balance is biased slightly downwards at about ~0.5mrad, which is acceptable. 

As another check for how much we moved the standoff while gluing, we can look at the spectra of the OSEMS while the mirror is free swinging, and see if/how the resonance frequencies have moved around. As Gautam previously mentioned, the pitch frequency is even softer than we expected from the thicker ruby standoff alone. This is due to the excess glue around the guide rod forcing us to position the standoff even lower to have good contact with the optic's barrel. In the plot below, the design yaw/pit/pos frequencies are the dashed lines, and the measured frequencies are the solid lines. 

[The plot is not in spectral density units, so that the peak heights reflect real units of motion at each resonance frequency. Data and code used to generate the plot is attached] 

According to the calculations from ELOG 12316, this pitch frequency implies the support point is 0.317mm lower than the design value of 0.985mm. (However, this is just an approximation and does not include the fact that each standoff is at a different height.)

Nevertheless, this difference is frequency is not so large that the dynamics of the suspension will be qualitatively changed in some important way; really, the pitch frequency is just ~1.5dB lower. So, I deemed our standoff gluing a success, removed the optic from the suspension, and placed it in an optic holding ring after giving the top of the barrel a gentle drap wipe with some iso. At this point, I used the microscope to look at the ruby standoff groove. As far as I can tell, no glue has invaded the groove - it looks sharp as ever. (whew)

I also wiped the wire with acetone and easily removed the glue droplets. However, I noted that (as is the case for ETMY) the wire is deformed at the points where it was in contact with the standoffs. I wonder if we should re-suspend with new wire, or accept the current deformed wires.

In any case, we can now move on to air baking the ETMX tower and gluing the stray magnet back onto ETMY.

• The latest twist in this apparently never-ending saga was that even though fine pitch balancing was achieved, the wire was out of the groove on both sides!
• I rectified this situation in the morning, did the fine pitch balancing in the afternoon
• Koji's suggestion of adjusting the OSEM holding plate totally did the trick, all four magnets are reasonably well centered relative to the vertical now...
• After the latest round of fine pitch balancing, we are now tilted in pitch backwards (i.e. towards the AR face) by <0.7mrad. 
• Prior to gluing, I visually inspected the optic to check that (see attachments):
  • Wires are in grooves on both sides
  • Unglued ruby standoff has the correct "rotation", i.e. that the wire contacts the standoff after the groove has started, and leaves it before the groove ends, since the groove doesn't go all the way around the standoff
  • Section of wire around the bottom half of the optic has no obvious kinks/other funny features
  • Unglued standoff is in contact with the barrel
  • All magnets are well clear of teflon in OSEM coils on both sides
• Eric also checked the frequencies of the various modes (PIT, YAW, POS and SIDE) by looking at the power spectrum of the free-swinging error signals on the coils. The pitch mode is now softer than before, at ~710mHz
• We then proceeded to glue the optic, using a needle to apply the glue (optic was clamped using face EQ stops, bottom EQ stops were not engaged as we felt this would affect the fine pitch balancing
• During the process, it looks like we may have inadvertently gotten some glue onto the wire (see attachments) - it doesn't look like any has seeped into the groove itself, but there is definitely some on the wire. We can possibly try cleaning this once the optic is out. In the worst case scenario, we will have to loop another section of wire, but the fine pitch balancing should be unaffected provided we did not perturb the optic too much
• Bob has said the large oven will be available to bake the cages on Tuesday, August 9th. By this time, we should have ETMY suspended as well (we were unable to glue the knocked off magnet on ETMY as the glass bowl we had for soaking the edge of the optic in acetone to remove the epoxy residue broke while I was assembling the various pieces of Teflon inside it. Steve is procuring a new one on Monday). It is still unclear when we can vacuum bake the two ETMs...

Attachments:

Attachment #1: Wire is in the groove in the unglued wire-standoff, groove rotation looks pretty good.

Attachment #2: Ruby standoff is sitting on the barrel of the optic (if you zoom in)

Attachment #3: Side magnet is well centered w.r.t OSEM coil

Attachment #4: UR magnet is well centered w.r.t OSEM coil

Attachment #5: UL magnet is well centered w.r.t OSEM coil

Attachment #6: LL magnet is well centered w.r.t OSEM coil

Attachment #7: LR magnet is well centered w.r.t OSEM coil

Attachment #8: Wire is in the groove in the glued Ruby standoff

Attachment #9: Standoff after gluing. 3-4 drops of epoxy are visible on the wire, but none looks to have seeped into the groove itself

Attachment #10: Side view of newly glued Ruby standoff

Attachment #11: Before and After gluing shots.

I took the spectrum of an EM172 connected to my amplifier inside and outside a large box filled with foam layers:

I also made a diagram with my plan for the microphone amplifier boxes. This is a bottom view:

The dimensions I got from this box: http://www.digikey.com/product-detail/en/bud-industries/CU-4472/377-1476-ND/696705

This seemed like the size I was looking for and it has a mounting flange that could make suspending it easier. Let me know if you have any suggestions.

I'll be doing a Huddle test next week to get a better idea of the noise floor and well as starting construction of the circuits to go inside the boxes and the boxes themselves.
 

0.0017" OD., 500ft steel music wire ordered. Pictures of the existing roll are below. It will be on 8" OD. spool too.

If only the LL magnet looks too low, doesn't this mean that the OSEMs are not arranged in a square shape?
If so, you can fix this misalignment by moving the OSEM holding plate rather than OSEM shimming, can't you?

Part 1: Rotation of optic

• As reported in my elog yesterday, both the left magnets (UL and LL) seemed too low relative to the OSEM coils
• Eric and I checked the height of the scribe lines using the microscope and found that the scribe lines were low on the left side and high on the right side (as viewed from the AR side) by approximately the same amount, confirming our suspicion that the optic was rotated. The position of the scribe line on the bottom of the optic relative to the bottom-rear face EQ stop also suggested the same
• Eric brought in the bottom EQ stops, and once the wire was slightly unloaded, rotated the optic by the required amount by hand 
• This process took two tries, but we were successful
• Re-checked heights of scribe lines using microscope, and once we were satisfied, re-did the coarse pitch balancing

Part 2: Replacement of holder for top pair of OSEMs

• Eric and I had difficulty removing the UR OSEM-holding screw
• This is the non-silver-coated new variety of screw
• It got to a point where I could neither move the screw in or out, even with the help of a pair of pliers
• I decided to swap out the piece of the suspension tower holding the top two OSEMs (UR and UL) with the same piece from the old ETMX tower that is currently residing on the flow bench at the south end (along with the accompanying piece that overhangs the optic and holds the front-face and top earthquake stops
• I cleaned the piece 3-4 times with acetone, and then a couple of times with isopropanol. I adjudged this to be sufficient as we are going to air bake the tower anyways prior to installation in the vacuum chamber
• I then swapped the pieces:
  • First I brought in the bottom pairs of EQ stops
  • Next, I secured the optic using the three lower face EQ stops
  • Then, I removed the EQ stop screws from the overhanging piece, after which I removed the overhanging piece itself
  • After removing the top-back EQ stop, I removed the OSEM-holding piece from the suspension tower
  • Did the above steps in reverse, installing the new piece
• All went smoothly. This piece does not have a serial number unfortunately
• After this, I re-inserted the OSEMs, and judged the magnet-coil alignment to be satisfactory to proceed further
• We decided to use the old variety of silver plated OSEM holding screws for the top two OSEMs (by choice) and the side OSEM (the new variety is too short anyways). During the course of my work tonight, I found this worked way better. The bottom pair of OSEMs remain held by the new variety of unplated screws. We may want to review whether we really want to use this new type of screws (I believe the idea is to make it easier to tighten and loosen the screws)

Part 3: Fine pitch balancing

• As per the SOS assembly procedure, I turned off the HEPA filters at the clean bench for this part of the work
• Checked that the HeNe beam incident on the optic was level with the tabletop, beam height set to 5.5"
• Proceeded to do the fine pitch balancing the same way as described in yesterday's elog (i.e. no PZT buzzer, just fine touches by hand)
• I was able to converge fairly quickly to a good point in configuration space
• After re-centering the OSEM coils such that the PD output was ~50% of its maximum value (see Attachment #1), I found over a lever arm length of 56" (=1.42m) a beam height deviation from 5.5" by <2mm. This corresponds to 0.7mrad pitching forwards towards the HR side
• The suspension assembly procedure tells us to aim for 0.5mrad, but I think this is close enough for standoff gluing, as this misalignment is extremely sensitive to the OSEM coil positions (although I would say, from Attachment #1, that they are actually pretty well centered)
• The only thing that concerns me is that the LL magnet is still a little low relative to the coil. This can be fixed by shimming if necessary...

Attachment #1: Striptool trace showing OSEMs are pretty well centered (towards the end, I turned on the HEPA filters again, which explains the shift of the traces). The y-axis is normalized such that the maximum displayed corresponds to the fully open PD output of the coils

Attachment #2: Fine pitch balancing optical lever setup

Attachment #3: Tower assembly

Attachment #4: SIDE OSEM close-up

Attachment #5: UR OSEM close-up

Attachment #6: UL OSEM close-up

Attachment #7: LL OSEM close-up (this is the concerning one)

Attachment #8: LR OSEM close-up

We should also check the following (I forgot and don't want to wear my clean jumpsuit again now to take more photos):

1. Wire is still in groove
2. Standoff is sitting on the optic barrel and not on epoxy residue of the guiderod

Late coming elog about the deletion of the apahce config files

Thu Aug 4 8:50ish 2016

Please don't restart apache2

I accidentally deleted four files in /etc/apache2/sites-available / on nodus. The deleted files were

elog   nodus  public_html  svn

I believe public_html is not used as it is not linked from /etc/apache2/sites-enabled

They are the web server config files and need to be reconfigured manually. We have no backup.

Currently all the web services are running as it was. However, once apache2 is restarted, we'll lose the services.

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!