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ID Date Author Type Category Subjectup
  12445   Fri Aug 26 11:35:44 2016 gautamUpdateSUSETMY UL sensor problematic

I've been noticing that the ETMY UL sensor output has been erratic  over the last few days. It seems to be jumping around a lot, even though there is no discernable change in any of the other sensor signals. Damping is OFF, which means the sensor signals should just be a reflection of actual test mass motion. But the fact that only one sensor output is erratic leads me to believe that the problem is in the electronics. I've also double checked that we aren't touching any EQ stops. Also, we had centered all the sensor outputs to half their maximum value pretty carefully. But looking at the Striptool traces, I now find that the UL sensor output has settled at some other value. Simply removing the OSEM connector and plugging it in again leads to the sensor output going back to the carefully centered value. Could it be that the photodiode has gone bad? If so, do we have spare OSEMs to use? I will also re-squish the satellite box cables to see if that fixes the problem.

Attachments:

Attachment #1: Sensor output spectra around the bounce mode peak. Nothing was touched inside the chamber between the time this spectrum was taken and the spectrum I put up last night (in fact the chamber was closed)

Attachment #2: UL sensor output is erratic, while the others show no glitching. This supports the hypothesis that the problem is electronic. The glitch itself happened while the chamber was closed.

Attachment #3: The only difference between this trace and Attachment #2 is that the UL connector was removed and plugged in (OSEM wasn't touched)

  12446   Fri Aug 26 14:05:38 2016 SteveUpdateSUSETMY UL sensor problematic

This problem has existed well before the vent

 

  12447   Fri Aug 26 14:09:46 2016 ericqUpdateSUSETMY UL sensor problematic

We do indeed have a box of clean spare OSEMs, it should be out with all of the other boxes of clean stuff we had for the suspension building. You could also try swapping in a different satellite box, to see if the circuit powering the OSEM PD is to blame.

  12449   Sun Aug 28 21:40:11 2016 gautamUpdateSUSETMY UL sensor problematic

I wanted to observe the UL coil for any excursions over the weekend. Looking at the 2 day trend, something is definitely wrong. These glitches/excursions are much more pronounced than what is seen in the pre-vent plots Steve had put up.

In order to try and narrow down whether the problem is with the Satellite box or the LED/PD themselves, I switched the Satellite box at the Y end with the Satellite box for ITMY (at ~930pm tonight). Hopefully over a 12 hour observation period, we see something that will allow us to make some conclusion. 

  12450   Mon Aug 29 09:37:05 2016 gautamUpdateSUSETMY UL sensor problematic

It looks like the problem is indeed in the Satellite box. Attachment #1 shows the second trend for the last 12 hours (~930pm 28 Aug 2016 - 930am 29 Aug 2016) for the ITMY and ETMY sensor signals. The satellite boxes for the two were switched during this time (the switch is seen at the leftmost edge of the plots). After the switch, ETMY UL has been well behaved, though ITMY UL shows evidence of excursions similar to what we have been seeing. All the ITMY coils are pulled out of the suspension cage currently, and are just sitting on the optical table, so they should just be reading out a constant value. I think this is conclusive evidence that the problem is with the Satellite box and not the OSEM itself. I will pull the Satellite box out and have a look at its innards to see if I can find the origin of the problem...

  242   Wed Jan 16 18:24:41 2008 ranaUpdateSUSETMY Watchdog
Because Steve keeps complaining about ETMY, I looked at some minute trend to see if there was something exotic happening at that time. It looks like there is some tremendous seismic activity to make it happen.

The trend shows that there is nothing special happening on the ETMX accelerometer or the ETMX suspension. At the same time, however, there is a huge jump in the ETMY sensors and therefore the watchdog signal. Whenever the watchdog value goes above 140, it trips.

After Andrey moves some accelerometers over to the Y end we can see the effect more directly.
  2204   Sun Nov 8 14:18:25 2009 AlbertoUpdateSUSETMY Watchdogs tripped

This afternoon I re-enabled the ETMY coils after I found that the watchdogs for the mirror had tripped last night at 2:06am.

  14551   Thu Apr 18 22:35:23 2019 gautamUpdateSUSETMY actuator diagnosis

[rana, gautam]

Rana did a checkout of my story about oddness of the ETMY suspension. Today, we focused on the actuators - the goal was to find the correct coefficients on the 4 face coils that would result in diagonal actuation (i.e. if we actuate on PIT, it only truly moves the PIT DoF, as witnessed by the Oplev, and so on for the other DoFs). Here are the details:

  1. Ramp times for filter modules:
    • All the filter modules in the output matrix did not have ramp times set.
    • We used python, cdsutils and ezca to script the writing of a 3 second ramp to all the elements of the 5x6 output matrix.
    • The script lives at /opt/rtcds/caltech/c1/scripts/cds/addRampTimes.py, can be used to implement similar scripts to initialize large numbers of channels (limiters, ramp times etc).
  2. Bounce mode checkout:
    • ​The motivation here was to check if there is anomalously large coupling of the bounce mode to any of the other DoFs for ETMY relative to the other optics
    • The ITMs have a different (~15.9 Hz) bounce mode frequency compared to the ETMs (~16.2 Hz).
    • I hypothesize that this is because the ETMs were re-suspended in 2016 using new suspension wire.
    • We should check out specs of the wires, look for either thickness differences or alloying composition variation (Steve has already documented some of this in the elog linked above). Possibly also check out the bounce mode for a 250g load on the table top.
  3. Step responses for PIT and YAW
    • With the Oplevs disabled (but other local damping loops engaged), we applied a step of 100 DAC counts to the PIT and YAW DoFs from the realtime system (one at a time)
    • We saw significant cross-coupling of the YAW step coupling to PIT, at the level of 50%.
  4. OSEM coil coefficient balancing
    • I had done this a couple of months ago looking at the DC gain of the 1/f^2 pendulum response.
    • Rana suggested an alternate methodology 
      • we used the lock-in amplifier infrastructure on the SUS screens to drive a sine wave
      • Frequencies were chosen to be ~10.5 Hz and ~13.5 Hz, to be outside the Oplev loop bandwidth
      • Tests were done with the Oplev loop engaged. The Oplev error signal was used as a diagnostic to investigate the PIT/YAW cross coupling.
      • In the initial tests, we saw coupling at the 20% level. If the Oplev head is rotated by 0.05 rad relative to the "true" horizontal-vertical coordinate system, we'd expect 5% cross coupling. So this was already a red flag (i.e. it is hard to believe that Oplev QPD shenanigans are responsible for our observations). We decided to re-diagonalize the actuation.
      • The output matrix elements for the lock-in-amplifier oscillator signals were adjusted by adding some amount of YAW to the PIT elements (script lives at /opt/rtcds/caltech/c1/scripts/SUS/stepOutMat.py), and vice versa, and we tried to reduce the height of the cross-coupled peaks (viewed on DTT using exponential weighting, 4 avgs, 0.1 Hz BW - note that the DTT cursor menu has a peak find option!). DTT Template saved at /users/Templates/SUS/ETMY-actDiag.xml
      • This worked really well for minimizing PIT response while driving YAW, not as well for minimizing YAW in PIT. 
      • Next, we added some YAW to a POS drive to minimize the any signal at this drive frequency in the Oplev YAW error signal. Once that was done, we minimized the peak in the Oplev PIT error signal by adding some amount of PIT actuation.
      • So we now have matrices that minimize the cross coupling between these DoFs - the idea is to back out the actuation coefficients for the 4 OSEM coils that gives us the most diagonal actuation, at least at AC. 
  5. Next steps:
    • All of our tests tonight were at AC - once the coil balancing has been done at AC, we have to check the cross coupling at DC. If everything is working correctly, the response should also be fairly well decoupled at DC, but if not, we have to come up with a hypothesis as to why the AC and DC responses are different.
    • Can we gain any additional info from driving the pringle mode and minimizing it in the Oplev error signals? Or is the problem overconstrained?
    • After the output matrix diagonalization is done, drive the optic in POS, PIT and YAW, and construct the input matrix this way (i.e. transfer function), as an alternative to the usual free-swinging ringdown method. Look at what kind of an input matrix we get.
    • Repeat the free-swinging ringdown with the ETMY bias voltage adjusted such that all the OSEM PDmons report ~100 um different position from the "nominal" position (i.e. when the Y arm cavity is aligned). Investigate whether the resulting eigenmode frequencies / Qs are radically different. I'm setting the optic free-swinging on my way out tonight. Optic kicked at 1239690286.
  2255   Thu Nov 12 15:40:27 2009 josephb, koji, peterUpdateComputersETMY and Megatron test take 1

We connected megatron to the IO chassis which in turn was plugged into the rest of the ITMY setup.  We had manually turned the watchdogs off before we touched anything, to ensure we didn't accidently drive the optic.  The connections seem to go smoothly.

However, on reboot of megatron with the IO chassis powered up, we were unable to actually start the code.  (The subsystem has been renamed from SAS to TST, short for test).  While starttst claimed to start the IOC Server, we couldn't find the process running, nor did the medm screens associated with it work.

As a sanity test, we tried running mdp, Peter's plant model, but even that didn't actually run.  Although it also gave an odd error we hadn't seen before:

"epicsThreadOnceOsd epicsMutexLock failed."

Running startmdp a second time didn't give the error message, but still no running code.  The mdp medm screens remained white.

We turned the IO chassis off and rebooted megatron, but we're still having the same problem.

 

Things to try tomorrow:

1) Try disconnecting megatron completely from the IO chassis and get it to a state identical to that of last night, when the mdp and mdc did run.

2) Confirm the .mdl files are still valid, and try rebuilding them

  15653   Mon Nov 2 12:44:25 2020 gautamUpdateGeneralETMY and OMC chamber heavy doors off

[koji, rana, gautam]

This morning, we did the following;

  1. Removed the ETMY chamber heavy door. It is stored on the rack at the east end.
  2. Removed OMC chamber heavy door. It is smaller than the other chamber doors, so doesn't sit on the standard size rack we have. So it is laid flat, on a clean sheet of ameristat, on a cart next to the NE corner of the PSL table.
  3. After taking some photos of the chamber and making sure the position of the suspension tower was marked by some stops, we removed the ETMY cage and moved it to the cleanroom area. The optic was EQ stopped during the transport, and the OSEMs were removed. The ETMY Oplev HeNe was turned off and the PSL was shuttered to allow us to work without goggles.
  4. The broken off magnet was retrieved from inside the OSEM. The shadow sensor voltage recovered a value of ~800cts, which means the LED/PD pair on the UR OSEM seems to work fine, and it was in fact the magnet blocking the PD that was the issue.
  5. In the cleanroom area, we removed the optic from the wire loop and placed it on the magnet gluing fixture. The wire is intact (for now), so there is some hope of re-suspending it in the same loop.

The OSEMs remain in the EY vacuum chamber. The next set of steps are:

  1. Clean the EP30-2 residue from the broken magnet joint - this will require some scrubbing with an acetone soaked scrub or similar implement.
  2. Reglue the broken magnet.

We will most likely work on this tomorrow. At ~1615, I briefly opened the PSL shutter and tweaked the IMC alignment. We will almost certainly change the pointing into the IMC when we remove the old OMC and rebalance that table, so care should be taken when working on that...

Quote:
  1. We are now ready to take the doors off. 
  755   Tue Jul 29 13:54:08 2008 ranaUpdateSUSETMY and PRM have EQ related problems
The attached trend shows that ETMY and PRM both had large steps in their sensors
around the time of the EQ and didn't return afterwards. The calibration of the
OSEM sensors is ~0.5 mm/V. The PRM sensors respond when we give it huge biases
but there is very little change in the ETMY. Almost certainly true that the
optics have shifted in their wire slings and that we will have to vent to
examine and repair at least ETMY.

Jenne is looking at the spectra of the other suspensions to see if there is
other more subtle issues.
  756   Tue Jul 29 14:38:02 2008 robUpdateSUSETMY and PRM have EQ related problems

Quote:
The attached trend shows that ETMY and PRM both had large steps in their sensors
around the time of the EQ and didn't return afterwards. The calibration of the
OSEM sensors is ~0.5 mm/V. The PRM sensors respond when we give it huge biases
but there is very little change in the ETMY. Almost certainly true that the
optics have shifted in their wire slings and that we will have to vent to
examine and repair at least ETMY.

Jenne is looking at the spectra of the other suspensions to see if there is
other more subtle issues.


Some additional notes/update:

ETMY, PRM, & MC2 had OSEM signals at a rail (indicating stuck optics). Driving the optics with full scale DAC output freed ETMY and MC2, so while these may have shifted in their slings it may be possible to avoid a repair vent. PRM is still stuck. One OSEM appears to respond with full range to large drives, but the other three face OSEMS remain disturbingly near the rail (HIGH, which is what would happen if a magnet fell off).
  12434   Tue Aug 23 19:35:38 2016 gautamUpdateSUSETMY back in IFO

[johannes, gautam]

Summary: Today we moved the suspended ETMY optic back into the chamber from the cleanroom. Once in the chamber, we positioned the optic using the stops that marked the previous position of the optic. We then shortened the arm length by 19mm (in order to match the X and Y arm lengths. The F.C. coat on the HR face was removed prior to the final placement of the optic. We then adjusted the OSEM positions in their holders to get the sensor outputs to half their maximum value.

We did not get to check where the input beam hits the optic or see if the pitch balance of the optic is such that the reflected beam makes it back to the ITM. The plan for tomorrow is to do this. 


Part 1: Cleanroom work

  • We worked a little more on trying to adjust the rotational position of the OSEM coils in order to minimize the coupling of the bounce mode into the sensor signals. 
  • We had limited success in this regard. After about an hour, we concluded that it made more sense to do this in the chamber itself. For one thing, the drive electronics for the Y end are different (in the cleanroom, we are using the X end electronics, satellite box etc.).
  • We adjusted the position of the OSEMs till the sensor output readout was half the open value as best as we could. We also made sure that the wire was in the groove on both sides and that the magnets were well centered in the vertical direction relative to the OSEM coils and that there was no danger of knocking any magnets off (see attached pictures).
  • We then engaged all the EQ stops, and transferred the suspension cage to a cart (topped with Al foil, wiped clean) for transportation to the Y-end (with OSEMs left in).

Part 2: Transportation of optic

  • Nothing special here, just took great care while going over bumps near doors between the cleanroom and the IFO, and along the Y-arm itself.
  • Definitely a 2 man job - one person can lift a pair of wheels over any bumps while the other can make sure there is no danger of the cage toppling over. 

Part 3: Chamber work

  • PSL shutter was closed for this part of work. Earlier today, I found that C1SUSAUX had failed yet again (why are all the slow computers dying more often nowadays?!). I restarted the slow machine, and locked the mode cleaner. The alignment hadn't drifted so much from when EricQ had last aligned the IMC, and with only minimal tweaking, I was able to lock the IMC and see a beam on the REFL camera.
  • First, I transferred the suspension cage onto the edge of the table inside the chamber. Care was taken not to accidentally place the cage onto the trailing OSEM wires.
  • There were some specks of dust on the barrel of the optic, and also the cage. These were removed with clean wipes and isopropanol.
  • I judged that it would be too precarious to remove the F.C. with the optic in its final desired position. So we decided to take the coat off with the optic at the edge of the table. The central part of the HR face looks pretty clean. Even though the whole HR face was cleaned with F.C., the part that was left uncovered prior to putting the optic back into the chamber has a few specks of dust on it (see attachments). These could not be removed just by blowing ionized air. I was hesitant to drag wipe the optic, so I left things as is. In any case, the optic as a whole is MUCH cleaner (to my eye at least) than prior to the cleaning. 
  • Conveniently, the stops marking the previous position of the optic were on the far side and back.
  • Since we wanted to shorten the Y arm length by 2 cm, we placed a clean steel ruler of width 19mm in front of the rear stop (see attached pictures). I then moved the cage back along the side stop till I hit the ruler.
  • I then clamped the optic down, removed the spacing ruler, and re-adjusted the position of the rear stop to mark the new position of ETMY.
  • We were concerned that the change of position of the cage on the table affected the leveling. Checking with a clean spirit level, we found evidence of a slight tilt in the direction towards the vertex of the IFO, as expected from the way the ETMY cage was moved. To compensate for this, I moved one of the counterweight masses (see attachments) till the spirit level showed the table to be level (to its resolution) in two perpendicular directions
  • We then plugged in the OSEMs into the DB25 connectors on the table. We found that the Y-end electronics were giving different readouts from what we had been seeing in the cleanroom with the X end electronics (not surprising I guess). We resolved to pull out all the OSEMs, check their maximum sensor output values, and re-insert them till the sensor output was half this maximum as best as we could. NOTE TO SELF: UPDATE THE WIKI PAGE!
  • We turned on the damping, and found that the exisiting input matrix performs fairly well.
  • We took a quick look at the spectra of the sensor outputs - interestingly, with the suspension on the seismic stacks inside the chamber, the 16.4 Hz bounce mode peak showed up clearly (these were totally absent in the cleanroom). I did not attempt any fine rotation of the OSEMs in the holders (it is not even clear to me how good/bad the present configuration is) because I reasoned we first need to apply a pitch bias to get the beam back to the ITMY chamber and then re-adjust the OSEM coils. The bounce mode decoupling will be the last step. 
  • For tonight, we decided to leave the optic freely swinging (with EQ stops close by) so that tomorrow, we can look at the offline spectra of sensor outputs and if necessary, re-diagonalize the suspension. 
  • After checking nothing unwanted was left behind in the chamber, we closed it up for tonight.

Plan for tomorrow:

  • Pitch balancing check (by looking at reflected beam at ITMY)
  • Re-adjust OSEMs on ETMY, minimize bounce mode coupling into sensor outputs
  • Make Y arm cavity by re-positioning ITMY

Attachments:

Attachment #1: Wire is in groove in side without OSEM

Attachment #2: Wire is in groove in side with OSEM (picture taken with OSEM coil removed)

Attachment #3: UL magent relative to OSEM coil

Attachment #4: LL magent relative to OSEM coil

Attachment #5: LR magnet relative to OSEM coil

Attachment #6: UR magnet relative to OSEM coil

Attachment #7: Side magnet relative to OSEM coil

Attachment #8: ETMY HR face with F.C. film removed. Non-covered part isn't super clean, but the covered part itself does not have any large specks of dust visible.

Attachment #9: Scheme adopted to shorten Y arm length by 19mm.

Attachment #10: Current situation inside EY chamber. Counterweight that was moved to balance the table is indicated.

 

  12444   Thu Aug 25 21:11:43 2016 gautamUpdateSUSETMY back in IFO

There was some confusion as to the order in which we should go about trying to recover the Y arm. But here are the steps we decided on in the end.

  1. Use the tip tilts to make sure the input beam is hitting roughly the center of ETMY, with ITMY left out.
  2. Use the reflected beam from the ETM as viewed in the ITM chamber to set the pitch bias on ETM.
  3. Center OSEM coils on ETM, rotate them to minimize bounce mode coupling into the sensor signals.
  4. Install the ITM, look for cavity flashes, and use alignment biases to try and lock the Y arm in air.

Yesterday, Eric, Johannes and I tried to do step 1, but after some hours of beam walking, we were unsuccessful. Today morning, Koji suggested that the ITM wedge could be playing a part - essentially, over 40m, the wedge would shift the beam horizontally by ~30cm, which is kind of what we were seeing yesterday. That is, with 0 biases to the tip tilts, we could find the beam in the ETM chamber, towards the end of the table, ~30cm away from where it should be (since the input pointing is adjusted taking this effect into account, but we were doing all of our alignment attempts without the ITM in).

So, we shifted strategy today. The idea was to trust that the green beam was well aligned to the cavity axis (we had maximized the green transmission before the vent), and set the pitch bias voltage to ETMY by making the reflected beam overlap with itself. This was done successfully, and we needed to apply a pitch bias of ~-2.70 (value on the MEDM screen slider), which agrees well with what I was seeing in the cleanroom. We then adjusted the OSEMs to bring the sensor outputs to half their nominal maximum value. Next, we went into the ITMX chamber, and were able to find the green beam, at the right height, and approximately where we expect the center of the ITM to be (this supports the hypothesis that the green input pointing was pretty good). I am however concerned if this is truly the right value of the bias for making a cavity with the ITM, because the pre-vent value of the pitch bias slider for ETMY was at -3.7, which is a 30% difference from the current value (and I can't think of a reason why this should have changed, the standoffs weren't touched for ETMY). If we go ahead and fine tune the OSEMs rotationally assuming this is the right bias to have, we may end up with sub-optimal bounce mode coupling into the sensor signals if we have to apply a significantly larger/smaller offset to realise a cavity? The alternative is to put in the ITM, and set the pitch balance using the IR beam, and then go about rotating OSEMs. The obvious downside is that we have to peel the F.C. off, risking dirtying the ITMs.

For much of the rest of the day, we were trying to play with the rotation of the OSEM coils in order to minimize the bounce mode coupling into the sensor signals. We weren't able to come up with a good scheme to do this measurement, and I couldn't find any elog which details how this was done in the past. The problem is we have no target as to how good is good enough, and it is extremely difficult to gauge whether our rotation has improved the situation or not. For instance, with no rotation of the OSEMs, by observing the bounce mode peak height over a period of 20-30 minutes, we saw the peak height change by a factor of at least 3. This is not really surprising I guess, because the impulses that are exciting the bounce mode are stochastic (or at least they should be), and so it is very hard to make an apples to apples comparison as to whether a rotation has improved the situation on.

After some thought, the best I can come up with is the following. If anyone has better ideas or if my idea is flawed, or if this is a huge waste of time, please correct me!

  1. Adopt this spectrum (except the side signal) as a reference for what constitutes "good" rotational orientation of the OSEMs (even though it is for ETMX not ETMY).
  2. Start with one coil. The suspension assembly document tells us to expect the orientation with minimal bounce coupling to be located within 20 degrees of "the vertical", the vertical being defined as that orientation in which the line connecting the LED and PD as seen by eye is vertical. So start with the coil oriented vertically, as best as possible by eye.
  3. Damp the optic for ~1min, with the curtain covering the chamber entrance. Ideally, we want the door back on, as this lowers the noise floor significantly, but it is too cumbersome to replace even the light door so I suppose we will have to compromise.
  4. Take a reference spectrum. In the interest of time, I think a bandwidth of 0.1Hz on the Fourier Transform should be sufficient. (Tangentially related - the BW you specify in the measurement setup in DTT doesn't seem to be the BW with which the spectrum is computed, I wonder why that is?)
  5. It is basically impossible to rotate the coil continuously. So divide the range to be explored into steps (so each step will involve rotating the coil by ~2 degrees (I don't know if this number is physically feasible, but some discrete step will be involved). Rotate the coil, center it such that the sensor output is close to half the maximum.
  6. Pull the curtain down, damp the optic, and take another spectrum. If the bounce mode peak is higher, abandon this direction of rotation, and rotate the other way. We accept as the optimal position the one from which the bounce mode peak height gets worse by rotating to either side.

Of course, this method assumes that the excitation into the bounce mode is a constant over time. I'm also attaching the spectrum of the OSEM sensor signals right now - the optic is in the chamber, free swinging (no damping) with the door on (so it is fairly quiet). The LR signal seems to be the best (indeed seems to match the levels in this plot), but it is not clear whether the others can be improved or not.


There was also some concern as to whether we will be able to see the beam in the ETMX chamber once the ITM has been re-installed. Assuming we get 100mW out of the IMC, PRM transmission of 5.5%, and ITM transmission of 1.4%, we get ~35uW incident on the ETM, which while isn't a lot, should be sufficient to see using an IR card.

  1412   Fri Mar 20 12:07:19 2009 YoichiConfigurationASCETMY beam centering
I forgot to put this in the elog.
Last Sunday night, I centered the beam on the ETMY because it was too low.
To do so, I wrote scripts (beamCenterETMY-P and beamCenterETMY-Y) to continuously align the Y-arm while I'm moving the beam on the end QPD.
These scripts will continuously do the dithering servo and QPD centering in one direction (pitch for beamCenterETMY-P, yaw for the other).
So if you move the steering mirror in front of the end QPD, the servo will eventually move the beam spot on the ETM.
I centered the beam just by looking at the camera image.
No coupling measurements from Pitch/Yaw to length was done.
  5037   Tue Jul 26 11:38:45 2011 steveUpdateSUSETMY bias checked

 

 I test drove ETMY biases.

PITCH  worked well in slow and fast modes. Slow drive was from the IFO alignment screen C1:SUS-ETMY_PIT_COM and

the fast one from C1:SUS-ETMY_ASCPIT_OFFSET

YAW did not.  It was always diagonal. It was  specially bad with the fast drive. I compared them with ETMX. ETMX yaw is diagonal a little bit too.

The OPLEV return spots on the qpd ETMX and ETMY are big 5-6 mm diameter. The ETMY spot has weird geometry to qpd.

  4932   Fri Jul 1 18:54:34 2011 JamieUpdateSUSETMY binary whitening switching confirmed to be fixed

After finally figuring out what was messed up with ETMY I was able to get good measurements of the binary whitening switching on ETMY to determine that it is in fact working now:

ETMY
ul : 3.2937569959  = 10.3538310999 db
ll : 3.28988426634 = 10.3436124066 db
sd : 3.34670033732 = 10.4923365497 db
lr : 3.08727050163 =  9.7914936665 db
ur : 3.27587751842 = 10.3065531117 db

  12452   Mon Aug 29 21:53:14 2016 LydiaUpdateSUSETMY bounce mode coupling

[gautam, johannes, lydia]

We decided to try some different approaches on minimizing the ETMY bounce coupling today, since the peak height in the previously attched spectrum was  higher than the previously recorded levels in 2011 for all but the LR OSEM.

  • We recoreded a coarse reference spectrum with the light door off and the HEPA filter on. 
  • We attempted to match UL, UR and LL orientation to their apparent position in photos takes before the OSEMs were initially removed. We found that every OSEM showed a stronger bounce coupling, including those that had not been moved. We repeated the spectrum a few times, damping the optic and then turning the damping back off between each data set. The effect persisted, so we decided to move them back to where they started today (the final posiitons of our earlier optimization attempt). 
  • The peaks returned to approximately their reference levels for all except LL. UL was still the worst overall, so we attempted to more finely tune its angle without success: we saw increases in the peak height in both directions again (when turned approx. 3-4 degrees). 
  • We then turned the UL OSEM by 90 degrees. (See Attachment 1). Surprisingly, the 16.4 Hz peak height was greatly reduced (by a factor of 7-9). We took another spectrum to confirm and the peak was significantly lower than the reference yet again. We decided to leave the OSEM in this configuration in order to take a finer spectrum (See Attachment 2). However, this means that while the magnet looks well centered in the OSEM, the sideways range of motion is reduced and there are no earthquake stops preventing string side to side swings, so care should be taken in the ETMY chamber. 
  • Before starting, we had discussed a possilbe mechanism for bounce coupling that could potentially be minimized by turning the OSEM so that the nominal beam direction was horizontal. This would be possible if the beam of light inside the OSEM were directed toward the front or back, i.e. if it had some component parallel to the POS axis. Then, if the component of the beam in the plane of the optic's surface is oriented vertically, the bounce mode will move the edge of the magnet's shadow in and out of the center of the beam, allowing for strong coupling (proportional to the size of the angle). Turning the OSEM by 90 degrees would eliminate this kind of coupling. 
  • It's also true that (regardless of the mechanism) minimizing bounce couling for an OSEM maximizes the side coupling. The side coupling values of the pre-vent diagonalization matrices might be useful to compare to what we see now, to find out if the minimization we do in fact increases the side coupling (if not, maybe we are not truly minimizing the bounce coupling but observing some other effect, or our measurement method is too inconsistent.) Thoughts on this are welcome. 
  • Now that this improvement has been found, we should do a more thorough investigation to see where the true optimum position is (no small steps have been taken around this new position, and the minimum could also be at some angle in between).
  • In the interest of finishing the vent, should we try to find out exactly why the optimal angles seem so different than expected, or should we just try to minimize as best we can and move on to setting up the Y arm cavity? 
  4060   Wed Dec 15 17:21:20 2010 josephbUpdateCDSETMY controls status

Status:

The c1iscey was converted over to be a diskless Gentoo machine like the other front ends, following the instructions found here.  Its front end model, c1scy was copied and approriately changed from the c1scx model, along with the filter banks.  A new IOP c1x05 was created and assigned to c1iscey.

The c1iscey IO chassis had the small 4 PCI slot board removed and a large 17 PCI slot board put in.  It was repopulated with an ADC/DAC/BO and RFM card.  The host interface board from Rolf was also put in. 

On start up, the IOP process did not see or recognize any of the cards in the IO chassis.

Four reboots later, the IOP code had seen the ADC/DAC/BO/RFM card once.  And on that reboot, there was a time out on the ADC which caused the IOP code to exit.

In addition to the not seeing the PCI cards most of the time, several cables still need to be put together for plugging into the the adapter boards and a box need to be made for the DAC adapter electronics.

 

  4075   Mon Dec 20 10:06:36 2010 kiwamuUpdateCDSETMY damped

  Last Saturday I succeeded in damping the ETMY suspension eventually.

This means now ALL the suspensions are happily damped. 

It looked like some combination of gains and control filters had made unstabie conditions.

 2010Dec18.png

  I actually was playing with the on/off switches of the control filters and the gain values just for fun.

Then finally I found it worked when the chebyshev filters were off. This is the same situation as Yuta told me about two months before.

Other things like the input and the output matrix looked nothing is wrong, except for the sign flips at ULSEN and SDSEN as I mentioned in the last entry (see here).

So we still should take a look at the analog filters in order to make sure why the signs are flipped.

  133   Wed Nov 28 17:15:26 2007 ranaConfigurationSUSETMY damping / watchdogs
Steve has noted that ETMY was often tripping its watchdog. I saw this again today.

So I checked the damping settings. Someone had set the SIDE gain to +1. The gain which gives
it a Q of ~10 is +10. I set the SIDE gain to +20. I checked and the ETMX gain is -16 so now
they're at least similar. I have updated the snapshot to reflect the new value.

Hopefully now it will be more well behaved.
  1103   Fri Oct 31 08:52:19 2008 steveUpdateSUSETMY damping restored
ETMY watchdogs were tripped yesterday morning also. This is a problem that existed some months ago.(?)
Our seimo channels are inactive.
  2813   Tue Apr 20 08:00:52 2010 steveUpdateSUSETMY damping restored

ETMY sus damping was restored

  4775   Tue May 31 17:30:42 2011 steveUpdateSUSETMY damping restored

ETMY's watch dogs were found tripped. They were restored.

  6643   Mon May 14 08:49:47 2012 steveUpdateSUSETMY damping restored

ETMY sus damping restored.

  9388   Fri Nov 15 08:01:20 2013 SteveUpdateSUSETMY damping restored

ETMY sus damping restored

  9600   Wed Feb 5 09:28:32 2014 SteveUpdateSUSETMY damping restored

ETMY damping restored.

  1572   Sun May 10 13:41:17 2009 steveUpdateVACETMY damping restored, VC1 opened

ETMY damping restored.

Cryo  interlock closed VC1 ~2 days ago. P1 is 6.3 mTorr. Cryo temp 12K stable, reset photoswitch and opened VC1

  4068   Fri Dec 17 02:22:06 2010 kiwamuUpdateCDSETMY damping: not good

  I made some efforts in order to damp ETMY, however it still doesn't happily work.

 It looks like something wrong is going on around the whitening filters and the AA filter borad.

I will briefly check those analog parts tomorrow morning.

 

- - -(symptom)

Signs of the UL and the SD readouts are flipped, which I don't know why.

At the testpoints on the analog PD interface board, all the signs are the same. This is good.

But after the signals go through the whitening filters and AA filters, UL and SD become sign-flipped.

I tried compensating the sign-flips by changing the sign by means of the software, but it didn't help the damping. 

In fact the suspension got crazy when I activated the damping. So I have no idea if we are looking at exactly right readouts or some sort of different signals.

 

- - -(fixing DAC connector)

 I fixed a connector of the DAC ribbon cable since the solderless connector was loosely locked to its cable.

Before fixing this connector I couldn't apply voltages on some of the coils  but now it is working well.

  14608   Wed May 15 00:40:19 2019 gautamUpdateSUSETMY diagnosis plan

I collected some free-swinging data from earlier today evening. There are still only 3 peaks visible in the ASDs, see Attachment #1.

Plan for tomorrow:

TBH, I don't have any clear ideas as to what we are supposed to do to to fix the problem (or even what the problem is). So here is my plan for now:

  1. Take pictures of relative position of magnet and OSEM coil for all five coils
  2. Inspect positions of all EQ stops - back them well out if any look suspiciously close
  3. Inspect suspension wire for any kinks
  4. Inspect position of suspension wire in standoff

I anticipate that these will throw up some more clues 

  2366   Tue Dec 8 13:03:26 2009 KojiUpdateCOCETMY drag wiped

Jenne, Kiwamu, Alberto, Steve, Bob, Koji

We wiped ETMY after recovery of the computer system. We take the lunch and resume at 14:00 for ITMX.
Detailed reports will follow.

  8595   Fri May 17 15:38:51 2013 SteveUpdate40m upgradingETMY enclosure is on the way back

 

 It  will arrive around 10 am Monday morning.

 

  8423   Mon Apr 8 16:37:26 2013 SteveUpdate40m UpgradingETMY enclosure wall transmission

 

 Enclosure cover #1 transmission measured  in 1064 nm,  156 mW,  P polarization and beam size ~ 1 mm

As condition:  fully assembled, protective layer removed, tinted- adhesive activated on yellow acrylic on top of each other.

T = 1.2 % in 20 minutes exposure test. This agrees with the test measurement of 6-18-2012

There is a reflected  2-3 cm circular glare that is barely visible on sensor card. It is well below 1 mW level

As we are installing the NPRO with ~350 mW of power we have to address what additional shield should be installed.

The June 2012 test with 1W power burned through of the 3 layer  IR coated films in 3-4 hours.

We 'll use Aluminum shields in the high power path till we come up with better solution.

  2956   Thu May 20 12:10:44 2010 kiwamuUpdatePhotosETMY end table

 I updated the photo of ETMY end table on the wiki.

http://lhocds.ligo-wa.caltech.edu:8000/40m/Optical_Tables

  4848   Tue Jun 21 19:10:29 2011 SureshUpdateEnvironmentETMY end table

[Suresh, Sonali]

There were small pieces of glass, remnants of a fluorescent tube, which were lying around on the ETMY end table for a while now.  We picked up the larger pieces by hand and used the HEPA filtered vacuum cleaner to pick up the remaining glass and dust on the table. 

  5163   Wed Aug 10 01:40:40 2011 KojiUpdateSUSETMY exploration

[Rana Koji Jenne Jamie]

- The situation of the ETMY suspension is improved.
- The damping servos except for Pitch are now functional.
- We intentionally turned off the damping servos for the matrix measurements.


- Opened the light door of the ETMY chamber.

- We set up the CDS SUS lockin:

        Excite UL/UR/LL/LR equally [by setting the output matrix (1, 1, 1, 1, 0)] at 3.12Hz with 2000 cnts
        Put the OSEM PD outputs into lockin one by one. For the image rejection, 0.1Hz 4th order LPF has been used though we like to use a faster settling LPF.

- Found only UL was responding to the excitation. After fitzing with the cables and connectors, it was found that the DAC card was loose from the bus.
  By pushing the card the responses have been back. [Note we had the reboot of c1iscey almost at the same time.]

- Checked the response in the I channel of the lockin.
        UL -8ish / UR +7ish / LR +5ish / LL +2ish

- Tweaked LL sensor to get better response ==> in vain. Decided to move the lower OSEM plate for the better positioning of the LR/LL.
- Got reasonable (+5ish) response for LL.

- Confirmed that the POS/YAW/SIDE damping works with positive gains. PITCH did not work with the negative gain (but that could be a good sign.)

- Let the suspension freely swinging for a while (~30min). Checked the side/pos separation. They are not perfect but seemed diagonalizable.

- Closed the light door.

- Jenne will make a better kick/free-swing test later.

  5164   Wed Aug 10 02:29:38 2011 JenneUpdateSUSETMY exploration

Quote:

- Jenne will make a better kick/free-swing test later.

 02:27am, ran the new freeswinging-ifo.csh script.  It's just a copy of freeswinging-all.csh, but it doesn't include the MC mirrors, since Suresh and Kiwamu are still working.  

Now we have copies of the script for -all, -mc, -ifo to cover the various sections of the suspended interferometer.

  1603   Mon May 18 21:34:18 2009 ranaConfigurationSUSETMY f2pRatio script run
Now that the ETMY optical lever is not so bad, I ran the f2pRatio script and it seems to have worked.

I cleaned up the script a little also. Updated in the SVN.

ETMY's A2L scripts have to be run to reduce the A2L noise once the arm is locked again. Might also need
to set the OL UGF too.
  1605   Tue May 19 12:30:41 2009 robConfigurationSUSETMY f2pRatio script run

Quote:
Now that the ETMY optical lever is not so bad, I ran the f2pRatio script and it seems to have worked.

I cleaned up the script a little also. Updated in the SVN.

ETMY's A2L scripts have to be run to reduce the A2L noise once the arm is locked again. Might also need
to set the OL UGF too.


Just to show, in part, what the script does.

The F2A filters are turned on at 12:21, and the oplev no longer responds to large LSC drives in ETMY.
  16731   Thu Mar 17 11:40:41 2022 PacoUpdateSUSETMY green PZT HV supply

[Anchal, Paco]

We installed a HV kepco power supply for the green PZT steering the YAUX beam. We did this in anticipation of the YARM alignment to take place this afternoon. We borrowed an unused DC power supply labeled "OMC Power spply" and made an appropriate SMA connection (Attachment #1), Then we set the Vset to 100.0 Volts and the current limit to 10 mA. Once we enabled the output we saw the 5.6 mA of current drawn by the eurocard in accordance with the wiki log (Attachment #2). 

It may not be possible to use the PZT as per this so this work may not have a direct impact on our upcoming alignment task.


We probably bumped the ethernet cable (martian network) on c1iscey, so the FE models stopped showing up on the medm screens. When we connected it back, it seemed like the FE kept running the model and only IPC showed error. We restarted the rtcds models on c1iscey and burtrestored to today morning 5:19 am.

burtwb -f /cvs/cds/rtcds/caltech/c1/burt/autoburt/today/05:19/c1scyepics.snap -l /tmp/controls_1220317_115006_0.write.log -o /tmp/controls_1220317_115006_0.nowrite.snap -v

ETMY is properly damping now and the oplev is roughly centered as well but the OPLEV Servos are off. We did not turn them on.
We should be able to carry out our cavity arm alignment today afternoon on both arms now.

  12412   Tue Aug 16 08:04:49 2016 SteveUpdateSUSETMY had Aluminum bridge

The SOS ETMY tower had and Aluminum bridge. How is it possible that this was true? Is SS better than Al for some quantitative scientifc reason ???

Their weight ratio as measured  =  922 / 307 g = 3

Destinies:  SS 304 / Al 6061  >  0.289 / 0.098  [ lb /in3 ] =  2.94

  5215   Fri Aug 12 17:37:11 2011 JenneUpdateSUSETMY hopefully good again

[Jamie, Jenne]

We went in to have a look-see at ETMY since it looked stuck-ish.  Jamie noticed that the side magnet was pretty close to the teflon plates of the OSEM.  We rotated it a bit, and now its all better.  We also adjusted the OSEMs until their mid-ranges were happy.  The U's were a little low, and the L's were a little high, as if the optic were a bit pitched backward.  Anyhow, we checked that the table is level, and tweaked the OSEMs.  We're starting the free-swinging test now...

Excited all optics

Fri Aug 12 17:38:53 PDT 2011
997231148

  5216   Fri Aug 12 20:28:13 2011 JenneUpdateSUSETMY hopefully good again

Quote:

[Jamie, Jenne]

We went in to have a look-see at ETMY since it looked stuck-ish.  Jamie noticed that the side magnet was pretty close to the teflon plates of the OSEM.  We rotated it a bit, and now its all better.  We also adjusted the OSEMs until their mid-ranges were happy.  The U's were a little low, and the L's were a little high, as if the optic were a bit pitched backward.  Anyhow, we checked that the table is level, and tweaked the OSEMs.  We're starting the free-swinging test now...

Excited all optics

Fri Aug 12 17:38:53 PDT 2011
997231148

 Hmmm.  I'm no longer convinced that ETMY is healthy.  I think that when I gave it a kick, it's bouncing against something.  I can't fit the peaks to get the input matrix.  I guess step 1 is to try giving it a smaller kick for the free swinging spectra.  But if the owl shift folk feel like it, they might have a look-see.

  14611   Wed May 15 17:46:24 2019 gautamUpdateSUSETMY inspection

I setup the usual mini-cleanroom setup around the ETMY chamber. Then I carried out the investigative plan outlined here.

Main finding: I saw a fiber of what looks like first contact on the bottom left (as viewed from HR side) of ETMY, connecting the optic to the cage. See Attachment #1. I don't know that this can explain the problem with the missing eigenmode, it's not a hard constraint.  Seems like something that should be addressed in any case. How do we want to remove this? Just use a tweezer and pull it off, or apply a larger FC patch and then pull it off? I'm pretty sure it's first contact and not a piece of PEEK mesh because I can see it is adhered to the HR side of the optic, but couldn't capture that detail in a photo.

There weren't any obvious problem with the magnet positioning inside the OSEM, or the suspension wire. All the EQ stop tips were >3mm away from the optic.

I also backed out the bottom EQ stops on the far (south side) of the optic by ~2 full turns of the screw. Taking another free-swinging dataset now to see if anything has changed. I will upload all the photos I took, with annotations, to the gPhotos later today eve. Light doors back on at ~1730.

Update 10pm: the photos have been uploaded. I've added a "description" to each photo which should convey the message of that particualr shot, it shows up in my browser on the bottom left of the photo but can also be accessed by clicking the "info" icon. Please have a look and comment if something sticks out as odd / requires correction.

Update 1045pm: I looked at the freeswinging data from earlier today. Still only 3 peaks around 1 Hz.

The following optics were kicked:
ETMY
Wed May 15 17:45:51 PDT 2019
1242002769
  14612   Wed May 15 19:36:29 2019 KojiUpdateSUSETMY instepction

A pair of tweezer is OK as long as there is no magnets around. You need to (somewhat) constrain the mirror with the EQ stops so that you can pull the fiber without dragging the mirror.

  5704   Wed Oct 19 17:33:07 2011 kiwamuUpdateGreen LockingETMY mechanical shutter : fully functional

The mechanical shutter on the Y end is now fully functional.

 

 It is newly named to 'C1AUX_GREEN_Y_Shutter' in the EPICS world.

It uses the same binary output channel which had been served for the POY shutter.

To change the EPICS name I edited a db file called ShutterInterLock.db, which resides in /cvs/cds/caltech/target/c1aux.

After editing the file I rebooted the c1aux machine, by telnet and the reboot command in order to make the change effective.

Also I added this new shutter on the ALS overview screen (see the attachment below)

MechShutter.png

Quote from #5701

The ETMY  shutter can be remotely switched from medm screen POY of mechanical shutters.

The new cable from ETMY controller goes to east vertex EV-ISCT where it is connected to POY shutter hook up BNC cable.

  5701   Wed Oct 19 16:28:35 2011 steveUpdateGreen LockingETMY mechanical shutter is working

Quote:

Uniblitz mechanical shutter installed in the green beam path at ETMY-ISCT  The remote control cable has not been connected.

The ETMY  shutter can be remotely switched from medm screen POY of mechanical shutters.

The new cable from ETMY controller goes to east vertex EV-ISCT where it is connected to POY shutter hook up BNC cable.

  5177   Wed Aug 10 18:25:45 2011 JenneUpdateSUSETMY mini-update

[Jenne, Jamie]

ETMY is now in its new nominal position, according to the rails that Kiwamu put in the other day.  OSEM voltages are all centered, and the magnets looked pretty well centered in the OSEM bores.  We're taking data for some free swinging spectra, to check the decoupling. 

Next up: Align Y-green to the arm, then move on to fixing the other optics that Jamie pointed out.

  8590   Thu May 16 08:32:05 2013 SteveUpdate40m upgradingETMY op table disabled

 

All ETMY optical table electronics- lasers-pds turned off, disconnected in order to remove enclosure.

linguaa.jpg

  8596   Fri May 17 16:06:14 2013 ranaUpdate40m upgradingETMY op table disabled

 

 TODO:

  1. We need to replace all of the floppy anodized Al dumps with clean razor blade dumps on stiff mounts. BOTH of the rejected ports of the 1064 FI need some kind of custom dump.
  2. All of the leakthrough beams of the HR mirrors also need razor dumps. A good rule of thumb is that your first notion of how to implement the beam dump is NOT good enough.
  3. The whole lens / modematching situation for the 1064 and 532 paths will have to be redone so as to put the beam waists inside the Faraday crystal (NOT outside). The beam waist in the 4.7 mm diameter Faraday should be ~0.3-0.4 mm.
  4. The efficiency that we got for the doubling shows that we don't need the cylindrical lenses - they are nice, but not needed to get 90% of the max power.
  5. The lenses between the 1064 FI and the doubler should be put onto a base that can be used to adjust the lens position for MM optimization. Nothing fancy, just something slideable.
  6. For this iteration of the table, we can do as Annalisa has written so as to get the green MM lenses ordered ASAP. After next week we can come up with a new plan before dismantling the EX table.
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