[Sasha, Masha, Liz, Eric]

A bunch of surfs in the lab just noticed that ETMX is going crazy (laser is shifting everywhere) due to a 4.5 EQ that just hit LA. The optic is already shut down according to the watchdogs.

[Mayank, Koji]

We aligned the ETMX with help of reflection of green beam from the ETMX. 

ITMX was aligned with Michelson fringe.

We could see the flashing of green HOM and the flashing of IR. However there was no signal at TRX. This is beacuse we have not connected the Higain PD yet.  In oder to use the QPD signal instead of Higain PD we set a negative threshold of PD selection.

We were able to see the flasing on the ndscope and the adgusted the ITMX and ETMX aligment to improve the transmission.

Even with high transmission we were not able to get any locking with ETMX actuation. We shifted to ITMX actuation and doubled the gain  to lock the Xarm.

To explore this assymettery in ETMX and ITMX actuation. We measured the transfer function of C1:SUS-ITMX_LSC_EXC to C1:LSC-XARM_IN1 and C1:SUS-ETMX_LSC_EXC to C1:LSC-XARM_IN1.  (Attachment #1). The TFs look different.

This could be because the Anti-De-Whitening is not yet updated for the ETMX new coil driver.        

To Do:

• Shift the boards on the rack.
• Connect BNC board to interface HighGainPD, Green ReFL etc.
• Recover the Suspension and OPlev functions.
• Update the AntiDewhitening Filter

All of the SUS used to have only 1 filter module for SIDE. They now have 3 filter modules for SIDE just like the other DOFs.

Today I moved the filters around so that the sensor filters are in SDSEN, the servo filters are in SUSSIDE, and the dewhitening for the coil is in SDCOIL.

I noticed along the way that the bounce/roll mode notches for all of the suspensions are still set for the frequencies of the previous suspensions. Suresh has 'volunteered' to find the new frequencies and make the new bandstop filters by looking up the seminal work on this by Dan Busby / Sam Waldman.

I calculated a better lens solution for the ETMX side view with the simple python script that's attached. The camera is still not as close to the viewport as we would like, and now the front lens is almost all the up to the end of the tube. With a little more playing around there maybe a better way, especially if we expand the repertoire of focal lengths. Using Steve's wonderful camera fixture I put the beam spot in focus. I turned the camera sideways for better use of the field of view, and now the beam spot actually fills the center area of the beam, to the point where we probably don't want more magnification or else we start losing the tails of the Gaussian.

We'll take a serious of images tomorrow, and will have an estimate of the scatter loss by the end of tomorrow.

We don't really have to calibrate the lens, just the CCD, which we've done. It's more about knowing the true aperture size to know how much solid angle you're capturing to infer the total amount of scatter. For our custom lens tubes this is the ID of the retaining ring.

The Edmund Optics lens tube looks tempting, but itcomes at a price. Thorlabs sells lens tubes that offer a more flexibility than what we have right now, so I bought a few different ones, and also more 150mm 2" lenses. This will allow for more compact solutions and offer some in-situ focusing ability that doesn't require detaching the lens tube like now. Should be here in a couple of days, then we'll be able to enclose the GigE camera in the viewport can with a similar field of view we have now.

I also bought a collimation package for the AS port fiber stuff so we can move ahead with the ringdown measurements and also mode spectroscopy.

 Telescope front lens to wall distance 25 cm,  GigE camera lenght 6 cm and cat6 cable 2cm

 Atm3,   Existing short camera  can has 16cm  lenght to lexan guard on viewport. Available 2" od periscope tube lenght is 8cm. The one in use 16 cm long.

             Note: we can fabricate a lite cover with tube that would accomodate longer telescope.

             Can we calibrate the AR coated M5018-SW and compare it's performance agains the 2" periscope

             Look at the Edmond Optics 3" od camera lens with AR

This lower priced   1" apeture Navitar lens  can be an option too.

 Atm1,   Now I can see dust. This is much better. The focus is not right yet.

Atm2,   Chamber viewport wiped and image refocused. Actually I was focusing on the dust.

ETMX oplev laser is dead. It will be replaced this after noon. Sus damping recovered.

I don't see any evidence of it getting more stable. It seems there was a big step in January, but the problem we were talking about - the suspension shifting when it gets a big kick - can't be proven to be gone or not by just looking at the trends. The real issue is whether or not it slips when we put in a large step in the LSC.

ETMX appears to be fine.  It was stuck to its OSEMs in the usual way.  I touched it and it dislodged and is now swinging freely.  Damping loops have been re-engaged.

While working on recovering interferometer alignment, I noticed that the ETMX Oplev SUM channel reported 0 counts. Attachment #1 shows the 200 day trend - despite the missing data, the accelerating downward decay is evident. I confirmed that there is no light coming out of the HeNe by walking down to EX. The label on the HeNe says it was installed in March 2017, so the lifetime was ~30 months. Seems a little short? I may replace this later today.

To facilitate POX locking investigations, I replaced this HeNe today with one of the spares Chub/Steve had acquired some time ago. Details:

• Part number: Lumentum 22037130 (1103P)
• Serial number: PA00836
• Manufacture date: 01/2019
• Power output: ~2.64 mW (Measured with Ophir power meter in the 632nm setting)
• Power received on QPD: ~0.37 mW = ~18700 cts (Measured with Ophir power meter in the 632nm setting)

The RIN of the sum channel with the Oplev servo engaged, along with that for the other core FPMI optics, in shown in Attachment #1. The ETMX HeNe RIN is compatible with the other HeNes in the lab (the high-frequency behaviour of the BS Oplev is different from the other four because the QPD whitening electronics are different).

Not sure what to make of the ETMY RIN profile being so different from the others, seems like some kind of glitchy behaviour, I could see the mean level of the ASD moving up and down as I was taking the averages in DTT. Needs further investigation.

The old / broken HeNe is placed i(nside the packaging of the abovementioned replacement HeNe) on Steve's old desk for disposal in the proper way.

*It looked like Steve had hooked up a thermocouple to be able to monitor the temperature of the HeNe head. I removed this feature as I figured if we don't have this hooked up to the DAQ, it isn't a really useful diagnostic. If we want, we can restore this in a more useful way.

After this activity, the DC bias voltage required on ETMX to restore good X arm cavity alignment has changed by ~1.3 V. Assuming a full actuation range of 30 mrad for +/- 10 V, this implies that the pitch alignment of the stack has changed by ~2 mrad? Or maybe the suspension wires shifted in the standoff grooves by a small amount? This is ~x10 larger than the typical change imparted while working on the table, e.g. during a vent.

Main point is that this kind of range requirement should probably be factored in when thinking about the high-voltage coil driver actuation.

• 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.

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

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?

The slow readback of the ETMX side seems to also have something flaky and bi-stable. This is not an issue for damping, but it disables the SIDE watchdog for ETMX and makes it unsafe if we accidentally use the wrong damping sign.

The slow signal from the side sensor on ETMX was last seen in action sometime in May 2010!  And then the frame builder has no data for a while on this channel.  After that the channel shows some bistability starting Sept 2010 but has not been working.  The fast channel of this sensor  (C1:SUS-ETMX_SDSEN_OUTPUT) does work so the sensor is working.  Probably is a loose contact... needs to be fixed.

Jenne, Anamaria

We aligned the ETMX OSEMs and ran into this issue. Looking at the SENSOR_SIDE channel, we pulled out the OSEM and determined that the open light voltage is 874 counts, so we centered it around 440 as well as we could. This is same channel as its slow counterpart SDSEN_OUTPUT (grey number immediately to the right on SUS medms).

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.

Koji suggested going through the following steps to check the ETMX suspension:

1. Do a free swing test to obtain the input matrix
2. Run the coil balancing script to change the gains on the them
3. Do the ring down test without closing the loop with the OPLEV and just with the OSEM to get Q~5
4. Tune the OPLEV servo gains

Suggestions welcome.
Tuning the ASC would make more sense once ETMX has been calibrated. Will run the free swing test tonight.

Update to 17809. The free swing test for ETMX took quite some time, here's a brief summary of what was going wrong and a small update on it.

tldr: The scripts haven't been too helpful to obtain the resonant frequencies. Paco (to the rescue) suggested pulling up the raw data from the channels and get a spectrum manually. From the free swing test that was run on Wednesday (1:00am, was ended abruptly), there was enough data to be able to obtain the resonant frequencies for the Position (0.9524Hz) and Pitch (0.7238Hz) DOFs. The resonant frequencies for Yaw (0.8334Hz) and Side (1.0001Hz) were obtained as well (Aug_Res_Freqs.png).
The percent change in resonant frequencies from the last free swing test run by Yehonathan (17714) for all modes was < 2%. Thus, I will skip the diagonalization and moving to the next step of tuning the coils.

Procedure & Possible Changes

The data was collected in batches, for POS, PITCH (SUSfreeswing_ETMX_1377417624_POS_PIT_YAW_SIDE.txt) (1050 seconds, 15 kicks, 10000 counts) first and then for YAW (SUSfreeswing_ETMX_1377619412_YAW.txt) and SIDE (SUSfreeswing_ETMX_1377623258_SIDE.txt) (720 seconds, 5 kicks, 10000 counts) respectively. At some point, the default could be changed for freeSwing.py as the default setting (15 kicks, 1050 seconds) or 4 DOFs takes (4*15*1050/3600 = 17.5 hours) to new setting (5 kicks, 720 seconds) (4*5*720/3600 = 4 hours). getResFreqs.py is still troublesome so the analysis for this particular test was done in python. The notebook (freeSwingtest_Aug23.ipynb) is attached. It uses 2 really nice snippets of code that Paco has written to obtain the channel data and get the spectra (welch) .

Troublemakers
With some hardware changes to the ETMX (suspectedly the acromag), the script assumes some things which were important to run the test. Manual adjustments: Damping turned off, ramp times for DAMP FILTERS and Coil Outputs set to 0 in EPICS. 

The default value for the kick is 30000. However, kicking with this offset in the DOF basis gave clipping in the coil outputs. This was changed by giving it a 10000 offset using options.

Suspicion: In order to run the subsequent scripts (getResFreqs.py and sus_diagonalization.py), it's important to run freeSwing.py by giving the degrees of freedom for which you would want to obtain the resonant frequencies (eg  -k POS PIT YAW SIDE) as there is an internal dependency for it. Not sure how the UR Coil kick (default) is usually processed ahead (need to read into this in detail)

Even with the above changes, getResFreqs.py was having trouble reading data from the channel (ValueError: could not broadcast input array from shape (xxxx) into shape (xxxx)). Unsure why. 

With the same options (5 kicks, 720 seconds, 10000 counts) for the freeswing test conducted at 01:00am (SUSfreeswing_ETMX_1377565258_YAW_SIDE.txt) and 09:00am (SUSfreeswing_ETMX_1377619412_YAW.txt), the time series for YAW looks terrible for the former (?????). The comparisions are attached (freeswing_yaw_5kicks_10000counts_720s_good.png , freeswing_yaw_5kicks_10000counts_720s_bad.png)

Resonant Frequency in Position:  0.9524518193317955 Hz
Resonant Frequency in Pitch:  0.7238633826921645 Hz
Resonant Frequency in Yaw:  0.833423765599566 Hz
Resonant Frequency in Side:  1.0001085187194791 Hz

COIL BALANCING FOR ETMX
Summary : I ran coil balancing on ETMX using the CoilStrengthBalancing.ipynb script to get a feel for it, no changes were required from the last time it was run by Paco. I realized I was measuring the wrong signal for the POS coupling (C1:SUS-ETMX_SUSPOS_IN1) while trying to minimize the BUT-POS coupling. This was stupid because the shadow sensors and actuation coils in this case are the OSEMs. The LSC error signal would be more appropriate for measuring the POS coupling.

The convention for the actuation vector used for the coils is [UL, UR, LL, LR]. The frequency, excitation counts are given through the LOCKIN1 channel (SUS->ETMX->LOCKIN1->f(Hz), Amp). The excitation vector is set in (SUS->ETMX->Output Filters->LOCKIN1)
Here, the excitation frequency used = 13Hz.
For "decoupling" the degrees of freedom, the script used is given in /opt/rtcds/caltech/c1/Git/40m/scripts/SUS/coilStrengthBalancing/ETMX/CoilStrengthBalancing.ipynb. In here, small steps are taken to "remove" the DOF contribution such that \\new_gain = old_gain +/- e*(decoupling DOF vector)\\. (e = step size)
The decoupling signals are observed in diaggui in the frequency range of (0 - 20Hz) and a bandwidth of 0.5Hz with exponential averaging (10 averages)

1. Minimizing BUT-POS coupling
Here, the LSC error signal (C1:LSC-POX11_I_IN1) is observed to measure the coupling in POS. For this, the arm is kept locked to obtain a decent error signal.
SANITY CHECK: This was tested by exciting POS [1,1,1,1] at 13Hz and measuring at the LSC error signal in diaggui which indeed showed a peak at 13Hz indeed. Damp filters and OPLEV servos were enabled to prevent the loss of lock.
The initial excitation was given to the Butterfly DOF [1, -1, -1, 1] at 10000 counts and 5 steps were taken in both directions of the POS vector to decouple the POS DOF. The initial peak showing up in the LSC error signal was already at a minimum. The excitation was ramped up to 20000 counts, where the peak was still very small. Thus, no change was made here (Attachment 1).

2. Minimizing POS-PIT coupling
Here, the OPLEV signal for PIT (C1:SUS-ETMX_OL_PIT_IN1) is observed to measure the coupling in PIT. The damping filters and OPLEV servos are disabled.
The initial excitation is given to POS [1, 1, 1, 1] at 5000 counts and 5 steps were taken in both directions of the PIT vector to decouple the PIT DOF. The initial peak showing up in the OPLEV signal was already at a minimum. Thus, no change was made here (Attachment 2).

3. Minimizing POS-PIT coupling
Here, the OPLEV signal for YAW (C1:SUS-ETMX_OL_YAW_IN1) is observed to measure the coupling in YAW. The damping filters and OPLEV servos ared disabled.
The initial excitation is given to POS [1, 1, 1, 1] at 5000 counts and 5 steps were taken in both directions of the YAW vector to decouple the YAW DOF. The initial peak showing up in the OPLEV signal was already at a minimum. Thus, no change was made here (Attachment 3).

4. Minimizing PIT-YAW coupling
This was one rather robust and was not susceptible to the decoupling process. Here, the OPLEV signal for both PIT (C1:SUS-ETMX_OL_PIT_IN1) and YAW (C1:SUS-ETMX_OL_YAW_IN1) are used to measure their relative coupling. Either of the DOF can be excited and while the other DOF can be used for the decoupling vector. Here, PIT was excited and the decoupling DOF vector was YAW. The damping filters and OPLEV servos ared disabled.
The initial excitation was given to the PIT DOF [1, 1, -1, -1] at 5000 counts and 5 steps were taken in both directions of the YAW vector to decouple the YAW DOF. The initial peak showing up in the YAW signal was already at a minimum. The excitation was ramped up to 10000 counts, however the YAW peak barely moved. Thus, no change was made here (Attachment 4).

To next.

Fitting results: 

 Pitch

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. 

Earthquake m4.1 test for ETMX and moves ITMX.  ITMX-LR sensor 0.3V

I sat down in the control room to find that ETMX and PRM's watchdogs had been tripped.  I don't know how long they've been crazy, but there was a big something that showed up in the seismometers around 16:30UTC, or ~11:30 this morning.  I don't find any significant earthquakes on the USGS site for that time though, so it might be more local, i.e. work next door or trucks or whatever.

I take back the suggestion that it was that seismic event.  Clearly the PRM and the ETMX were kicked at different times, neither of which is the same as the seismic action. Mystery.  You can see they have been ringing down for a while though, which is neat. 

I replaced the two remaining D-Sub M/M cables that still had gender-changers with M/F cables today, completing the mechanical and wiring work on the ETMX rack. All backplane adapter boards were secured to a cross-strut of the crate using zip ties. This was necessary because the adapter boards don't fit the crate with their panels attached ( the ETMX eurocrate is the only one with slightly different dimensions from all the others), and the we can't mount them to the strut using the panels. This won't be an issue on any of the other crates.

In other news:

I disabled the legacy support in the three Acromag ADC units and set the input averaging to 10 samples via the USB configuration utility. The documentation is unfortunately a little sparse about what this actually means. The manual states that "fresh input data is available to the network every 10ms", so the sampling rate is for sure faster than 100Hz. Since the IOC updates its channels every .1 seconds I assume that an averaging value of 10 to reduce the input noise is safe. The maximum value the configuration tool permits is 200. I tried this using the CryoLab DAQ and set all input channels to 200 and used StripTool to look at the time series of a slow oscillation (.1Hz) with a large amplitude (16Vpp) and looked for missed data points, indicating too long wait times for channels updates. There was no such qualitative difference between 1 sample, 10 samples, and 200 samples, so even pushing the averaging value to max seemed okay. I went with the conservative value of 10 for the ETMX DAQ, but we can likely increase this if noise on the slow inputs becomes an issue.

The input scaling of the ADC channels has been corrected. I changed the conversion method in the EPICS records from manual using the ASLO and AOFF fields to using engineering units via EGUF and EGUL. This required a little attention. The Acromags scale the dynamic input range of +/- 10V to +/- 30,000 raw value, but the EPICS IOC interprets the data type as ranging from -32767 to +32768, so the EGUF and EGUL fields must be set to -10.923 and +10.923 to achieve proper scaling. I also changed the SCAN field on all ADC channels to 0.1 seconds. This has been done for all ADC and DAC channel records.

ETMX is misbehaving again.  I went to go squish his cable at the rack and at the satellite box, but it still happened at least once.

Anecdotally and without science, it seems to happen when ETMX is being asked to move a "big" amount.  If I move the sliders too quickly (steps of 1e-3, but holding down the arrow key for about 1 second) or if I offload the ASS outputs when they're too large (above 10ish?), ETMX jumps so that it's about 50 urad off in yaw according to the oplev (sometimes right, more often left), and either 0 or 50urad off in pitch (up if right in yaw, down if left in yaw). 

So far, by-hand slowly offloading the ASS outputs using the sliders seems to keep it happy.

I would ask if this is some DAC bit flipping or something, but it's happening for outputs through both the fast front ends (ASS offloading) and the slow computers (sliders moved too fast).  So.  I don't know what it could be, except the usual cable jiggling out issue.

Anyhow, annoying, but not a show stopper.

Okay, now ETMX's badness is a show-stopper.  I'm not sure why, but after this last lockloss, ETMX won't stay put.  Right now (as opposed to earlier tonight) it seems to only be happening when I enable LSC pushing on the SUS.  ETMX is happy to sit and stay locked on TEM00 green while I write this entry, but if I go and try to turn on the LSC it'll be wacky again.  Daytime work.

Anyhow, this is too bad, since I was feelin' pretty good about transitioning DARM over to AS55. 

I had a line on (50 counts at 503.1 Hz pushing differentially on the ETMs), and could clearly see the sign flip happen in normalized AS55Q between arm powers of 4 and 6.  The line also told me that I needed a matrix element of negative a few x10^-4 in the AS55Q -> DARM spot.  Unfortunately, I was missing a zero (so I was making my matrix element too big by a factor of 10) in my ezcastep line, so both times I tried to transition I lost lock. 

So.  I think that we should put values of 0.5 into the power normalization for our test case (I was using SRCL_IN1 as my tester) since that's the approximate value that the DCtrans uses, and see what size AS55Q matrix element DARM wants tomorrow (tonight was 1.6-3 x 10^-4, but with 1's in the normalization matrix).  I feel positive about us getting over to AS55. 

Also, Q is (I assume) going to work some more tomorrow on PRMI->REFL165, and Diego is going to re-test his new IR resonance finding script.  Manasa, if you're not swamped with other stuff, can you please see if you can have a look at ETMX?  Maybe don't change any settings, but see what things being turned on makes ETMX crazy (if it's still happening in the morning). 

Upgrading the ETMX coil drivers calls for new coil balancing.

XARM locking using ETMX actuation shows a lot of TRX variation. To make life slightly easier I switch to ITMX actuation. Indeed, the ITMX variation.

1. I drive the ETMX butterfly mode at 13Hz, 10000 cts, and measure the XARM_IN1 signal on diaggui to minimize BUT->POS coupling. There is significant peak at 13Hz.

2. Changing the current coil gains from [-0.8, 1, -1, 1] to [-1,1,-1,1] already reduced the coupling significantly and it seemed that even for 20000 cts the 13 Hz could not be obsereved.

Next, I minimize the POS->PIT coupling

1. I turn off ETMX damping loops.

2. I drive the ETMX POS mode at 13Hz, 1000cts and measure C1:SUS-ETMX_OL_PIT_IN1

3. POS->PIT coupling is minimized using Anchal's technique. When the peak disappears I increase the dither amp to 100000

Next, POS->YAW is minimized in the same way.

Note: when the coil gains change so does the alignment. It is necessary to bring the optic back to the center of the QPD to make fair comparisons.

Since the gains have changed it is necessary to tune the damping loops again.

I measure Q=6 for POS, Q=4 for PIT and Q=3 for YAW.
I decide to reduce the gain of YAW a from 5 to 2.5. Q=5 for PIT now.

I also tune the ETMX OPLEV gains from 1.2 to 1.4.

Final coil balancing gains were:

UL = -1.233 , UR = 0.801, LL =0.767, LR = -1.199

[Paco, yehonathan]

Following Yehonathan's work from yesterday, I found the following coil balancing gains for ETMX:

['UL', 'UR', 'LR', 'LL'] = [-0.993  1.047 -1.007  0.953]

I decided to take a quick look at the data. Changes made to the ETMX coil driver board:

1. Fast path series resistances: 400 ohm ---> 2.25 kOhm (= 2x 4.5 kohm in parallel). Measured (with DMM) resistance in all 5 paths varied by less than 3 ohms (~0.2%).
2. All thick film resistors in signal (fast and bias) paths changed to thin film.
3. AD797 ---> Op27 for monitor output.
4. Above-mentioned mon output (30Hz HPF-ed) routed to FP LEMO mon via 100ohm for diagnostic purposes.
5. 4x Trim-pots in analog path removed. 

I also took the chance to check the integrity of the LM6321 ICs. In the past, a large DC offset on the output pin of these has been indicative of a faulty IC. But I checked all the ICs with a DMM, and saw no anomalies.

Measurement condition was that (i) the Fast input was terminated to ground via 50ohm, (ii) the Bias input was shorted to ground. SR785 was used with G=100 Busby preamp (in which Steve installed new batteries today, for someone had left it on for who knows how long) for making the measurement. The voltage measurement was made at the D-Sub connector on the front panel which would be connected to the Sat. Box, with the coil driver not connected to anything downstream.

Summary of results:

[Attachment #1] - Noise measurement out to 800 Hz. The noise only seems to agree with the LISO model above 300 Hz. Not sure if the low-frequency excess is real or a measurement artefact. Tomorrow, I plan to make an LPF pomona box to filter out the HF pickup and see if the low-frequency characteristics change at all. Need to think about what this corner freq. needs to be. In any case, such a device is probably required to do measurements inside the VEA.

[Attachment #2] - Noise measurement for full SR785 span. The 19.5 kHz harmonics are visible. I have a theory about the origin of these, need to do a couple of more tests to confirm and will make a separate log.

[Attachment #3] - zip of LISO file used for modeling coil driver. I don't have the ASCII art in this, so need to double check to make sure I haven't connected some wrong nodes, but I think it's correct.

Measurements seem to be consistent with LISO model predictions.

*Note: Curves labelled "LISO model ..." are really quad sum of liso pred + busby box noise.

My main finding tonight is: With the increased series resistance (400 ohm ---> 2.25 kohm), LISO modeling tells me that even though the series resistance (Johnson noise) used to dominate the voltage noise at the output to the OSEM, the voltage noise of the LT1125 in the bias path now dominates. Since we are planning to re-design the entire bias path anyways, I am not too worried about this for the moment.

I will upload more details + photos + data + schematic + LISO model breakdown tomorrow to a DCC page. 

gautam noon 21 June 2018: I was looking at the wrong LISO breakdown curves. So the input stage Op27 voltage noise used to dominate. Now the Bias path LT1125 voltage noise dominates. None of the conclusions are affected... I've uploaded the corrected plots and LISO file here now. 

I finished the re-soldering work today, and have measured the coil driver noise pre-Mods and post-Mods. Analysis tomorrow. I am holding off on re-installing the board tonight as it is likely we will have to tune all the loops to make them work with the reduced range. So ETMX will remain de-commissioned until tomorrow.

Initial tests look promising. Local damping works and I even locked the X arm using POX, although I did it in a fake way by simply inserting a x5.625 (=2.25 kohm / 400 ohm) gain in the coil driver filter banks. I will now tune the individual loop gains to account for the reduced actuation range.

Now I have changed the loop gains for local damping loops, Oplev loops, and POX locking loop to account for the reduced actuation range. The dither alignment servo (X arm ASS) has not been re-commissioned yet...

Per discussion today eve, barring objections, I will do the following tomorrow morning:

1. Remove ETMX coil driver board from 1X9
   • Change series resistances on the fast path to 2x4k in parallel. One will be snipped off once we are happy we can still lock.
   • Remove AD797s, potentiometers.
   • Thick film-->thin film for important components.
2. Remove ETMX de-whitening board from 1X9
   • Remove x3 analog gain.
   • Thick film-->thin film for important components.

I checked the four rear coils on ETMX by exciting XXCOIL_EXC channel in DTT with amplitude 1000@ 500 Hz and observing the oplev PERROR and YERROR channels.  Each coil showed a clear signal in PERROR, about 2e-6 cts.  Anyway, the coils passed this test.

 I also made xfer fctns of the 4 piston coils on ETMY and ETMX with OL_PIT.  (I looked at all 4 even though the attached plot only shows three.)  So it looks ike the coils are OK.

Background:
  c1iscex machine is currently being setup and RT model c1scx is running.
  But ETMX(south) didn't seem to be damped, so I checked it.

What I did:
  1. Checked the wiring. It seemed to be OK.
    Looked LEMO monitor output of SUS PD Whitening Board(D000210) with oscilloscope and they seemed to be getting some sensor signal except SDSEN.
      SDSEN is funny. C1:SUS-ETMX_SPDMon decreases slowly when PD input cable is disconnected, and increases slowly when connected.
      There might be some problem in the circuits.
    Looked LEMO monitor output of SOS Coil Driver Module(D010001) with oscilloscope and they seemed to be receiving correct signal from DAC.
      When ULCOIL offset is added, ch1 increased and so on.

  2. Checked the direction of SUSDOF motion when kicked with one coil.
    The result was;

    This table tells you, when ULCOIL_OFFSET increases, SUSPOS increases and so on.
    If URCOIL and LLCOIL are swapped, they look correct.
    Also, they have opposite sign to the usual optics(e.g. MCs, BS, PRM).

  3. Changed TO_COIL matrix according to the table above(see Attachment #1). Changed signs of XXCOIL_GAINs.

  4. ETMX damped!

Plan:
  - Check the wiring after SOS Coil Driver Module and circuit around SDSEN
  - Check whitening and dewhitening filters. We connected a binary output cable, but didn't checked them yet.
  - Make a script for step 2
  - Activate new DAQ channels for ETMX (what is the current new fresh up-to-date latest fb restart procedure?)

Finally I see what kicks the sus damping off

ETMX sus damping recovered.

Note: The giant metal garbage container was moved from the south west corner of CES months ago.

Huh? So should we ask them to put the container back? Or do you have some other theory about ETMX tripping that is not garbage related?

ETMX sus damping restored

ETMX sus damping restored

No we can't do that because the c1scx model is not working properly.

If you look into the real time controller screen you will find what I mean.

ETMX sus damping restored

ETMX sus damping restored.  It is still noisy

 I should have elogged, but I turned off the watchdog to remind myself that iscex computer is still crashed.  "Turning on" the damping doesn't do anything since there aren't any signals going to the coils from the computer.