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ID Date Author Type Category Subjectdown
  7316   Thu Aug 30 08:37:11 2012 SteveUpdateSUSETMX and ITMX needs more attention

Quote:

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.

Screenshot.png

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

  12348   Thu Jul 28 16:43:01 2016 LydiaUpdateGeneralETMX aluminium standoff groove condition

 

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. 

  5517   Thu Sep 22 13:45:17 2011 PaulUpdateSUSETMX actuator response fits

Fitting results: 

 Pitch

-- Fit completed after 305 iterations--
 Started with: Gain = 3e-05,
 Q factor = 5,
 Pole frequency = 0.6776,
 Fit results:  Gain = 1.85497e-06,
 Q factor = 23.7233,
 Pole frequency = 0.956686
 Residual (normalised against the sum of input datapoints) = 0.0202483
 
Yaw
-- Fit completed after 334 iterations--
 Started with: Gain = 3e-05,
 Q factor = 5,
 Pole frequency = 0.6776,
 Fit results:  Gain = 2.518e-06,
 Q factor = 7.21618,
 Pole frequency = 0.853559
 Residual (normalised against the sum of input datapoints) = 0.0570132
  12382   Sun Aug 7 14:53:39 2016 ericq UpdateSUSETMX Standoff gluing was successful

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] 

  Yaw Pitch Pos Side
Design frequencies from T000134: 0.773 Hz 0.856 Hz 1.001 Hz  
ETMX Measurement in-air 2010 0.828 Hz 1.04 Hz 0.908 Hz 0.949 Hz
Pre-gluing 0.785 Hz 0.709 Hz 0.949 Hz 0.975 Hz
Post-gluing 0.789 Hz 0.705 Hz 0.953 Hz 0.984 Hz

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.

  5146   Tue Aug 9 01:35:45 2011 SureshUpdateSUSETMX Side Sensor slow channel down for a long time

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.

ETMX-SDSEN_trend1.png         ETMX_SDSEN_trend2.png

 

  5255   Wed Aug 17 15:47:18 2011 AnamariaUpdateSUSETMX Side Sensor slow channel down for a long time

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).

 

 

Quote:

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.

 

 

  4889   Mon Jun 27 00:23:11 2011 ranaUpdateCDSETMX SIDE problem

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.

  12377   Fri Aug 5 02:17:10 2016 gautamUpdateSUSETMX Ruby Wire Standoff Ready for Gluing

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
  12378   Fri Aug 5 04:43:09 2016 KojiUpdateSUSETMX Ruby Wire Standoff Ready for Gluing

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?

  12381   Fri Aug 5 18:21:28 2016 gautamUpdateSUSETMX Ruby Wire Standoff GLUED
  • 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.

 

 
 
 

 

  14736   Tue Jul 9 08:33:31 2019 gautamSummarySUSETMX PIT bias voltage changed by ~1V

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.

Quote:

We unstuck ETMX by shaking the stack. Most effective was to apply large periodic human sized force to the north STACIS mounts.

  14911   Sun Sep 29 16:08:25 2019 gautamUpdateOptical LeversETMX Oplev HeNe replaced

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.

Quote:

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.

  14902   Fri Sep 20 11:39:04 2019 gautamUpdateOptical LeversETMX Oplev HeNe Dead

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.

  7309   Wed Aug 29 17:09:57 2012 jamieUpdateSUSETMX OK, free swinging

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.

Screenshot.png

  11646   Fri Sep 25 19:06:13 2015 ranaUpdateSUSETMX IS drifting

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.

Quote:

We have talked about the drift of ETMX sus on the Wednesday meeting.

It has stopped moving on Jan 8, 2015 and it has been reasanable stable since than.

 

  12885   Tue Mar 14 09:08:11 2017 SteveUpdateOptical LeversETMX HeNe is dead

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

  13377   Thu Oct 12 07:56:33 2017 SteveHowToCamerasETMX GigE side view at 50 deg of IR scattering

 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.

Quote:

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.

 

 

  13389   Wed Oct 18 11:37:58 2017 johannesHowToCamerasETMX GigE side view at 50 deg
uote:

 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

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.

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.

  13375   Thu Oct 12 01:03:49 2017 johannesHowToCamerasETMX GigE side view

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.

 

  4293   Mon Feb 14 23:29:04 2011 ranaSummarySUSETMX Fitlers moved around

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.

  7113   Wed Aug 8 09:46:29 2012 MashaUpdateEnvironmentETMX EQ

[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.

  880   Mon Aug 25 14:42:09 2008 EricConfigurationCamerasETMX Digital Camera
I changed the lens on the camera looking at the ETMX to a 16mm, 1:1.4 zoom lens. This is in preparation to measure a couple parameters that depend on the camera's position and angle, so please avoid repositioning it for a couple of days.
  676   Tue Jul 15 19:15:57 2008 ranaSummarySUSETMX Dewhitening characterization
Since the boys found that the ETM dewhitening transient was kicking the IFO out of lock we
decided to investigate.

First, we wrote a script to diagnose and then tune the DC gain of the dewhitening filters'
digital compensation filter (a.k.a. FM9 or SimDW). It is in the scripts/SUS/ directory
and is called dwgaintuner. It puts in an offset on each coil's DAC channel and
then reads back the Vmon on the coil driver with the DWF on and off. It reports the ratio of these
voltages which you can then type into the FM9/SimDW filter's gain field. We learned that the
difference between the analog DWF path and the bypass path was ~3% (which is consistent with
what you expect from the use of 1% resistors). We need to repeat this for all of the rest of
the suspended optics except for MC1 and MC3.

This Vmon method is better than what's used at the sites so we will export this new technology.

The attached plot shows some switching transients with only the local damping on:
BLUE:   Output of filter bank during an FM9 turn off. This is the transient which goes to the DAC.
        The transients are mostly of the same magnitude as this.
RED:    This is the input of the filter module during another such transient.
GREEN:  Tried another switch; this time I filtered the time series in DTT by typing the SimDW into
        the Triggered Time Series filter field. This should be simulating what comes out of the
        output of the DW board - to convert to volts multiply by 15/32768.
PURPLE: Same kind of filtering as the GREEN, but with also a double 30 Hz highpass to remove the low
        frequency damping control signals. You can see that the total transient is only ~5 counts
        or ~1 mV at the coil driver output. This is comparable to the relative offset in the bypass
        and filter paths.
  13523   Wed Jan 10 12:42:27 2018 gautamUpdateSUSETMX DC alignment

I've been observing this for a few days: ETMX's DC alignment seems to drift by so much that the previously well aligned X arm cavity is now totally misaligned.

The wall StripTool trace shows that both the X and Y arms were locked with arm transmissions around 1 till c1psl conked out - so in the attached plot, around 1400 UTC, the arm cavity was well aligned. So the sudden jump in the OSEM sensor signals is the time at which LSC control to the ETM was triggered OFF. But as seen in the attached plot, after the lockloss, the Oplev signals seem to show that the mirror alignment drifted by >50urad. This level of drift isn't consistent with the OSEM sensor signals - of course, the Oplev calibration could be off, but the tension in values is almost an order of magnitude. The misalignment seems real - the other Oplev spots have stuck around near the (0,0) points where I recentered them last night, only ETMX seems to have undergone misalignment.

Need to think about what's happening here. Note that this kind of "drift" behaviour seems to be distinct from the infamous ETMX "glitching" problem that was supposed to have been fixed in the 2016 vent.

 

  13527   Wed Jan 10 18:53:31 2018 gautamUpdateSUSETMX DC alignment

I should've put in the SUSPIT and SUSYAW channels in the previous screenshot. I re-aligned ETMX till I could see IR flashes in the arm, and also was able to lock the green beam on a TEM00 mode with reasonable transmission. As I suspected, this brought the Oplev spot back near the center of it's QPD. But the answer to the question "How much did I move the ETM by" still varies by ~1 order of magnitude, depending on if you believe the OSEM SUSPIT and SUSYAW signals, or the Oplev error signals - I don't know which, if any, of these, are calibrated.

  13528   Wed Jan 10 22:19:44 2018 ranaUpdateSUSETMX DC alignment

Best to just calibrate the ETM OL in the usual way. I bet the OSEM outputs have a cal uncertainty of ~50% since the input matrix changes as a function of the DC alignment. Still, a 30 urad pitch mis-alignment gives a (30e-6 rad)(40 m) ~ 1 mm beam spot shift. This would be enough to flash other modes, but it would still be easy to lock on a TEM00 like this. I also doubt that the OL calibration is valid outside of some region near zero - can easily check by moving the ETM bias sliders.

Quote:

I should've put in the SUSPIT and SUSYAW channels in the previous screenshot. I re-aligned ETMX till I could see IR flashes in the arm, and also was able to lock the green beam on a TEM00 mode with reasonable transmission. As I suspected, this brought the Oplev spot back near the center of it's QPD. But the answer to the question "How much did I move the ETM by" still varies by ~1 order of magnitude, depending on if you believe the OSEM SUSPIT and SUSYAW signals, or the Oplev error signals - I don't know which, if any, of these, are calibrated.

What we still don't know is if this is due to Johannes/Aaron working at the ETMX rack (bumping some of the flaky coil cables and/or bumping the blue beams which support the stack). Adding or substracting weight from the stack supports will give us an ETM mis alignment.

  12051   Mon Mar 28 10:43:18 2016 SteveUpdateendtable upgradeETMX 4'x2' optical table pictures

 

 

  10757   Fri Dec 5 00:52:51 2014 JenneUpdateSUSETMX 2nd order violin

We looked at the spectra of POX and POY during IR lock, and Q saw a peak at 1285 in POX only.  We're actuating on the ETMs, so it must be an ETMX violin mode, although it doesn't match the others that are in the table.

Anyhow, I added it to FM9.  While I was doing that, I realized that yesterday I had forgotten to put back the 3rd order ETM violin notch, so that is also in FM9.

  6729   Thu May 31 11:02:14 2012 steveUpdateLockingETMX 1064 trans camera

Quote:

Quote:

...will be helpful for acquiring lock after the vent.  We should install a camera at ETMX.

 Do that.

 Jenne and Steve

Sony CCD in place needs alignment and ND filter

  6838   Wed Jun 20 16:37:11 2012 yutaUpdateLockingETMX 1064 trans camera

[Jenne, Yuta]

We made ETMXT camera working.
We connected the camera to video mux, placed 10% pick off mirror in front of TRX PD, lead the beam go to ETMXT camera.
Transmission to the TRY PD was 23.8 uW, but now, it's 21.3 uW (2.3 uW goes to the camera).
So, we changed C1:LSC-TRX_GAIN from -0.00181818 to -0.00203158 (=-0.00181818*23.8/21.3).

There is a channel for power normalization, C1:LSC-TRX_POW_NORM, but is 1 and it looks like we are using this gain for the normalization. Situation of TRY is the same as TRX.

  6847   Thu Jun 21 12:56:49 2012 yutaUpdateLockingETMX 1064 trans camera

Quote:

[Jenne, Yuta]

We made ETMXT camera working.

 Xarm_EndTableLayout_NewTransCamera.png

Here's the new end table layout, for the transmitted IR stuff.

  13617   Wed Feb 7 16:09:06 2018 SteveUpdateSUSETMX -15V dc corrected

The ETMX  Sorrenson power supply -15V was running at -13.9V

  10645   Tue Oct 28 11:45:21 2014 manasaUpdateSUSETMX - observation

I looked at what are the situations that make ETMX lose alignment.

This is not occur all that often this morning; less than 10 times in may be the last 4 hours of poking the X arm. I found that the bad behavior of ETMX also exists in certain other cases apart from the case when we enable LSC.

(I) Even the MISALIGN and RESTORE scripts for the suspensions make the suspension behave bad. The RESTORE script while in the process of  bringing back the suspension to the place where it was, kicks it to some place else sometimes (even with LSC disabled)

(II) The suspension also gets kicked while realigning ETMX manually using sliders at 10^-3 (pace of 2-3 steps at a time).

I am suspecting something wrong right at the coil inputs and gains of the suspension.

Also, I recollect that  we haven't done a check on the X arm LSC limiters and filters ramping times like it was done for the Y arm ( Elog 9877 ). We should do this check to be sure that we are not seeing a mixed puddle of problems from 2 sources.

  2632   Tue Feb 23 14:56:24 2010 steveUpdateGeneralETMX optical table mass

Our janitor dropped one 48" long  fluorescent tube on the top cover of ETMX-isct. This accident made glasses fly all over the place.

He cleaned up nicely, but please beware of small glass pieces around ETMX chamber.

We did not clean up on the table in order to reserve oplev and green ITMX pointing alignment.

Plot below shows that the alignment was not effected.

 

 

  12171   Mon Jun 13 10:01:58 2016 SteveUpdateSUSETMX jumps

 

Quote:

ETMX has been jumping around again lately. Just now, I zeroed the ETMX alignment offsets in the SUS model, and centered the ETMX oplev spot via slow machine sliders. OSEM damping is on, oplev damping is off. Let's see how it moves around in the next day or so. 

GPS: 1149635923 

UTC: Jun 10 2016 23:18:26

 

  11092   Tue Mar 3 09:42:40 2015 SteveUpdateSUSETMX is drifting

The temperature of the east and south ends  are normal, they are about the same.

 

  7317   Thu Aug 30 12:01:27 2012 janosch, Manasa,SteveUpdate ETMX

We have done some work at ETMX today. We installed the baffle and placed two mirrors on the table.

The baffle position/orientation still needs to be checked more thoroughly to make sure that the beam will pass through the center of the baffle hole.

One of the two mirrors will stay on the table as pickoff. The other is only temporarily installed for alignment purposes. Later today we will shoot a laser into the chamber that will reflect off one of these mirrors towards the center of ITMX, then go back to the pickoff mirror next to ETMX and hopefully make it through the viewport.

To place the pickoff mirror, we had to move the "cable rack" next to ETMX a few inches towards the back of the table.

  7318   Thu Aug 30 13:10:41 2012 jamieUpdateCamerasETMX

Quote:

We have done some work at ETMX today. We installed the baffle and placed two mirrors on the table.

The baffle position/orientation still needs to be checked more thoroughly to make sure that the beam will pass through the center of the baffle hole.

I must say that I am not at all happy with the baffle situation.  It is currently completely blocking our camera view of the ETMX face.  Here's a video capture of the ETMX face camera:

etmx-face-baffle.png

The circle is the baffle hole, through which we can see just the bottom edge of the test mass.  I don't think whatever benefit the baffle gives out weights the benefit of being able to see the spot on the mirror.

This afternoon we will try to adjust the baffle, and maybe the camera view mirror, to see if we can get a better shot of the center of the TM.  If we can see the beam spot through the hole we can probably live with it.  If not, I think we should remove the baffle.

  7319   Thu Aug 30 17:03:32 2012 janosch, Manasa, SteveUpdate ETMX

The baffle has been moved away from ETMX towards the edge of the table (in fact, it is a little beyond the edge). It is also rotated so that its long edge is horizontal. In this way it was possible to center the baffle hole with respect to the optical axis, but also make it possible that the camera looks over the baffle.

We have tried to get an alignment beam from view port -> ETMX pick-off ->ITMX-> back to EX. This work was pretty much unsuccessful though. We could see the green laser scattering around ITMX, but there was no good way to know when the beam hit ITMX. So tomorrow we will find a better way to check where the beam is hitting at ITMX and finish the alignment of the scattering pick-off mirror.

  7412   Wed Sep 19 17:48:47 2012 DenUpdateModern ControlETMX

Time domain control using LQR technique is now applied to ETMX sus position. The plan was to do it for oplevs, I'll do it after the vent.

The cost function for state space variables was determined by TF  900 / (s + 30)^2. There was no penulty imposed for velocity, only for position. We can try that configuration as well.

etmx_suspos.png

  3966   Mon Nov 22 18:39:53 2010 JenneUpdateSUSETMU07: magnets glued to optic. ETMU05: magnets removed

[Suresh, Jenne]

A story about minor disasters, and crises averted:

Once upon a time, in a cleanroom not so far away..... there lived an optic.  To preserve anonymity, we shall call him "ETMU05".  This optic had a rough day.  When removing the grippers from the magnet-to-optic fixture, 4 out of 6 magnets broke off the dumbbells (the dumbbells were still securely glued to the optic...these had come out of the same batch that had problems last week, same problem).  The remaining 2, LL and LR, were sadly of the same polarity.  This is bad, because it means that the "humans" taking care of "ETMU05" didn't check the polarity of the face magnets properly, and ensure that they were laid out in an every-other pattern (LL and UR having the same polarity, and LR and UL having the opposite).  So, the humans removed all magnets and dumbbells from ETMU05.  All remaining glue was carefully scrubbed off the surfaces of ETMU05 using lens paper and acetone, and the magnets and dumbbells were sonicated in acetone, scrubbed with a lint-free wipe, sonicated again, and then scrubbed again to remove the glue.  ETMU05 had a nice cleansing, and was drag wiped on both the AR and HR surfaces with acetone and iso.  ETMU05 is now on vacation in a nice little foil hut.

His friend, (let's call him ETMU07) had a set of magnets (with polarities carefully confirmed) glued to him.  The cleaned magnets and dumbbells removed from ETMU05 were reglued to their dumbbells, and should be dry by tomorrow. 

.....And then they lived happily ever after.  The End.

 


The revised schedule / status table:

StatusTable.png

  3979   Tue Nov 23 18:08:28 2010 JenneUpdateSUSETMU07: Balanced, standoff glued. ETMU05: Magnets glued to optic

[Koji, Jenne]

ETMU07 had its wire winched to the correct height, was balanced, standoff glued.  Can be ready for going into the oven tomorrow, if an oven is available.  (One of Bob's ovens has a leak, so he's down an oven, which puts everything behind schedule.  We may not be able to get anything into the oven until Monday).

ETMU05 had magnets glued to the optic.  Hopefully tomorrow we will winch the wire and balance the optic, and glue the standoff, and be ready to go into the oven on Monday.

The spring plungers were sonicated, but have not yet been baked.  I told Daphen that we'd like the optics baked first, so that we can get ETMX in the chamber ASAP, and then the spring plungers as soon as possible so that we can install ETMY and put the OSEMs in.

The updated status table:

StatusTable.png

  3984   Wed Nov 24 17:57:24 2010 JenneUpdateSUSETMU07: Baking. ETMU05: Needs side magnets reglued

[Jenne, Koji]

We removed ETMU07 from the suspension tower, after confirming that the balance was still good.  Bob put it in the oven to bake over the weekend.  The spring plungers and our spare magnets are all in there as well. 

I tried to remove the grippers from ETMU05, and when I did, both side dumbbells came off of the optic.  Unfortunately, I was working on getting channels into the DAQ, so I did not clean and reglue ETMU05 today.  However Joe told me that we don't have any ETMY controls as yet, and we're not going to do Yarm locking (probably) in the next week or so, so this doesn't really set any schedules back. 

The cleaning of ETMU05 will be tricky.  Getting the residual glue off of the optic will be fine, but for the dumbbells, we'd like to clean the glue off of the end of the dumbbells using a lint free wipe soaked in acetone, but we don't want to get any acetone in the magnet-to-dumbbell joint, and we don't want to break the magnet-to-dumbbell joint.  So we'll have to be very careful when doing this cleaning. 

The Status Table:

StatusTable.png

  3956   Fri Nov 19 16:13:09 2010 JenneUpdateSUSETMU05: magnets glued to optic

[Jenne, Suresh]

Suresh and I glued the intact-from-the-first-round magnets to ETMU05.  I accidentally got too much glue on one of the dumbbells (the glue was connecting the dumbbell to the gripper - bad news if we let that dry), and while I was cleaning it, the magnet broke off.  So I used one of the ones that Suresh had re-glued last night, and he is putting that one back together after some cleaning. 

To set the fixture, Suresh had the great idea of using small pieces of foil underneath the teflon pads to set the height of the optic in the fixture.  The optic still rests on the teflon pads, but with the foil we have finer control over how the optic sits.  Neat.  Since both ETMs are the same, we shouldn't have to do any more adjustment for the other ETM.

The updated Status Table:

StatusTable.png

  4018   Mon Dec 6 23:33:15 2010 JenneUpdateSUSETMU05 winched, balanced, glued!!!!!!

[Suresh, Jenne]

We Finished!!!

ETMU05 (ETMY) had its wire winched to the correct height, was balanced, and had the standoff glued.  Since it's kind of like final exam week at Caltech, Suresh had his suspension exam today, and did most of this work himself, with me hanging around and watching. 

As you can see in my almost entirely green table, all that is left to do with the whole suspensions project is bake the optic (hopefully Bob has time / space this week), and then stick it in the chamber!  Hooray!!! (Can you tell I'm excited to not spend too much more time in the cleanroom?)

The table:

StatusTable.png

  4022   Tue Dec 7 18:37:15 2010 SureshUpdateSUSETMU05 ready for baking

The ETMU05 has been removed from the suspension and put into the little foil house. 

Before removing it I checked the position and pitch of the optic with reference to the table top. 

The height:

     Using the traveling microscope I checked the height of the scribe lines from the table top.  They are at equal heights, centered on 5.5 inches, correct to about a quarter of the width of the scribe line.

The pitch

    The retro-reflection of the He-Ne laser beam is correct to within one diameter of the beam at a distance of about 1.5m.  This is the reflection from the rear, AR coated, surface.  The reflection from the front, HR coated, surface was down by about two diameters.

Jenne has checked with Bob and agreed on a date for baking the optic.

 

 

  3991   Mon Nov 29 22:50:07 2010 SureshUpdateSUSETMU05 Side Magnets glued back

[Suresh, Jenne]

ETMU05 : Gluing Side magnets back on to the optic.

The following steps taken in this process:

1) The two magnet+dumbell units which had come loose from the optic needed to be cleaned.  A lint free wipe was placed on the table top and a few cc of acetone was poured on to it.  The free end of the dumbbell was then scrubbed on this wipe till the surface regained its shine.  The dumbell was held at its narrow part with a forceps to avoid any strain on the magnet-dumbbell joint.

2) The optic was then removed from its gluing fixture (by loosening only one of the three retaining screws) and placed in an Al ring. The glue left behind by the side magnets was scrubbed off with a optical tissue wetted with Acetone. 

3) The optic was returned to the gluing fixture.  The position of the optic was checked by inserting the brass portion of the gripper and making sure that the face magnets are centered in it [Jenne doubled checked to be sure we got everything right].

4) The side magnets were glued on and the optic in the fixture has been placed in the foil-house.

If all goes well we will be able to balance the ETMU05 and give it to Bob for baking.

 

ETMU07 : It is still in the oven and we need to ask Bob to take out. It will be available for installation in the 40m tomorrow.  

 

  9290   Fri Oct 25 04:54:21 2013 MasayukiUpdateSUSETM violin mode

Summary

When PRMI + 2arms are locked yesterday, we heard the noise from suspension violin mode. For attenuation of that noise, we should design the resonant filter at that frequency and put into the ALS servo. I tried to measure the violin mode of ETMs SUS.

What I did

 1.The arms were locked by IR PDH. I used awggui to excite the suspention. I injected the Normal waveform, 10 Hz of bandwidth wave into C1:SUS-ETMs_ULCOIL_EXC. I put cheby filter in the FIlter of awggui. The order of that filter was 4, that has same bandwidth as that of injection wave and ripple was 4dB. I increase the injection gain with some ramp time(5sec). I swept from 600 Hz to 700 Hz. During that injection I saw the PDH error signal (POX11I and POY11I) in order to find resonance peak of violin mode.
 In ETMX resonances were easily found. That were at 631 Hz and 691 Hz. the 631 Hz peak was seen ALS error signal yesterday. On the other hand, I couldn't find ETMY violin mode. No peaks appeared any frequency.

2. For find the ETMY violin mode, I used dtt swept sine measurement. The excitation channel was C1:SUS-ETMs_ULCOIL_EXC. I measured the TF from excitation channel to POX11I and POY11I error signal. The measurement range was above 400 Hz and below 1000Hz,. The number of point is 600. I attached that result.
In ETMX curve, the coherence become bad near the resonant frequency of violin mode and also the TF is large. Although ETMX violin modes are obvious, ETMY violin modes are not visible. At 660 Hz, 780 Hz, 900 Hz the coherence is not good. That is because 60 Hz comb noise.

Discussion

 I attached the spectrum of the POX and POY error signal. Black and red curve is measured different time. I didn't inject any signal in both measurement, but the violin mode excitation has huge difference. Also there are peaks at beat frequency between violin mode and bounce mode(16 Hz), yaw motion(3 Hz). In ALS in-loop noise or XARM in-loop measurement, sometimes this region had big spikes. That was because of this resonance. And also that resonance peak couples to POY11I.

 I will measure the Q and design the resonant filter for ALS.

  4041   Fri Dec 10 11:04:03 2010 OsamuUpdateSUSETM oplev mufunctioning

20101208_ETMX_oplev_sum.png

 

This plot shows ETM oplev and OSEM trend for 10 hours on day before yesterday as almost the same as plot shown this entry. I reported the 10-30minites fluctuations were seen, but I noticed it comes from not suspension but from oplev power fluctuation.

After Kiwamu fixed the ETM OSEM touch yesterday afternoon, still the same trend was seen, so we had thought what we fixed was not enough. This morning I looked at the yesterday's and day before yesterday's trend and noticed the simila trend both the pit and yaw in ETM oplev but not on the OSEM trend. Kiwamu suggested me to put the oplev sum on the same plot. It was!

So, ETMX is not bad, but in fact, still alignment fluctuation exist on the cavity. ITM?

 

  15488   Wed Jul 15 21:08:43 2020 gautamUpdateElectronicsETM coil outputs DQed

To facilitate this investigation, I've DQed the 4 face coil outputs for the two ETMs. EX is currently running with 5 times the series resistance of EY, so it'll be a nice consistency check. Compilation, installation etc went smooth. But when restarting the c1scx model, there was a weird issue - the foton file, C1SCX.txt, got completely wiped (all filter coefficients were empty, even though the filter module names themselves existed). I just copied the chiara backup version, restarted the model, and all was well again.

This corresponds to 8 additional channels, recorded at 16k as float 32 numbers, so in the worst case (neglecting any clever compression algorithms), we are using disk space at a rate of ~4 MB/s more. Seems okay, but anyway, I will remove these DQ channels in a few days, once we're happy we have enough info to inform the coil driver design.

spoke too soon - there was an RFM error for the TRX channel, and restarting that model on c1sus took down all the vertex FEs. Anyways, now, things are back to normal I think. The remaining red light in c1lsc is from the DNN model not running - I forgot to remove those channels, this would've been a good chance! Anyways, given that there is an MLTI in construction, I'm removing these channels from the c1lsc model, so the next time we restart, the changes will be propagated.

For whatever reason, my usual locking scripts aren't able to get me to the PRFPMI locked state - some EPICS channel value must not have been set correctly after the model reboot 😞. I'll debug in the coming days.

Fun times lie ahead for getting the new BHD FEs installed I guess 🤡 ....

Quote:
 

Looking at signals to the ETMs from the current lock acquisition sequence, the RMS current to a single coil is approximately _____ (to be filled in later).

So we may need a version of the fast coil driver that supports a low noise mode (with large series resistance) and a high-range mode (with lower series resistance for lock acquisition).

ELOG V3.1.3-