Test of an alog submission, reports of full disk problems.

Test of an alog submission, reports of full disk problems.

[Paul, Cheryl, Giacomo]

Yesterday (Friday) evening the reading from WFS_A and WFS_B didn't quite seem to make sense, despite them having been aligned a few hours before by Cheryl. Paul and I went back to the IO table to do some more systematic testing. Bottom line is that quadrant 3 of WFS_A seems defective. It has a large offset and possibly a reduced sensitivity (although the fact that it has some sensitivity might be partially good news).

Note that this is the same unit that showed the anomalous heating described in entry 5131. The tests performed in that occasion were too superficial to notice the defect.

Although it might be initially possible to still use this sensor for some ASC test (by compensating for the offset and sensitivity in software), we will eventually need to remove WFS_A from the table and test it. To our knowledge, no spare is readily available.

This is the set of measurements we performed (values are in adc counts). We first (column 2) measured the dark current (note that for some reason the single quadrants have a sign inversion wrt the sum), then centered the beam on the WFS witht he IMC locked (column 3), then intentionally unlocked the IMC (column 4), then realigned the beam again (column 5) and finally re-locked the IMC (column 6). Note that the change in reading between IMC locked/unlocked in not necessarily due to beam wondering, as the shape of the beam itself is very different between the unlocked (mostly gaussian) and locked (mostly junk) states.

Attached are plots of dust counts > .3 microns and > .5 microns in particles per cubic foot from approximately 5 PM Jan. 17 to 5 PM Jan. 18. Also attached are plots of the modes to show when they were running/acquiring data. Dust monitor 10 in the H1 PSL enclosure is still indicating a calibration failure. The plots of the status gave a 'No data output' error, but I'm not sure what it means, since plots were generated and look reasonable.

The airbake oven in the LSB Optics Lab is baking 10 of the Nichrome wrapped glass formers. These will be baking over the weekend and are sort of precariously stacked. If you are in the Optics Lab and need to move the oven please contact me before jostling anything around.

Jim & I moved one stack of the Trim Mass & Damping Assemblies (D1003161) 5" +Y.  Next we removed 0.75kg from each of two Assemblies to compensate for the strut that SUS has added to the Quad.  These two Assemblies are located at A27,B48 & A36,B48 (D1001989 sht3.)

At this point, Travis came into the chamber and removed the SUS protection pieces and the IAS CornerCube; he did not remove the Teflon Stops and the SUS remains locked.
Next, Jim unlocked Stage2 and the CPS numbers settled down suggesting that when the Teflon Stops are removed, all corners will look pretty good.  Corner 1 is a little low and removing those stops should lift that side of Stage2.  Then Jim unlocked Stage1 and the CPS numbers look comfortably close to the pre/vent & ISI lock time at the start of the year.

So next step is to back off the HEPI locks--they are very lightly engaged.  Check the optical table level.  Have IAS check X position, adjust as required with HEPI.  Unlock the SUS and check pitch & yaw; adjust as required.

[Giacomo, Matt, Lisa, Cheryl, Keita, Kiwamu, Paul]

With the mode cleaner locking easily again, we were able to measure the open loop transfer function at the IMC servo board. Three such transfer functions are shown in the first attached plot here ('IMC_OLTFs.pdf), with these settings common to each transfer function:

• Servo fast gain = -2dB
• Servo slow gain = 0dB
• Servo common mode 'compensation filter' 40kHz/4kHz ON
• MC2 M3 input filter gain = 1
• MC2 M3 lock filters: [150:4], [CLP100], gain = -1000
• MC M3 input filter gain = 1
• MC2 M2 lock filters: [0.1:1], [0.01:0.1], [ELP70], gain = 0.005

And these settings specific to each transfer function:

Low gain 'lock acquisition' mode

• Common mode gain = 0dB
• Common mode boost filter 1kHz/20kHz OFF

High gain mode

• Common mode gain = 24dB
• Common mode boost filter 1kHz/20kHz ON

High gain mode + notch filter 

• Common mode gain = 24dB
• Common mode boost filter 1kHz/20kHz ON
• Analog notch filter placed between demodulator I phase output and servo input (see attached plot 'Notch_TF.pdf' for notch filter transfer function)

And now a bit of explanation:

From low gain mode to the high gain mode, we engaged the first common mode boost filter on the servo board, and ramped the gain up in steps, all the while looking at the OLTF up to maybe 500kHz. From this we expected that we should be able to push the UGF up quite a bit past 100kHz, but when we got past 24dB common gain, the loop became unstable (despite apparently having enough phase margin at the UGF. We looked out to a little higher frequency and saw the feature at 730kHz, which at 24dB was just poking above 0dB and apparently causing the instability. To cure this problem we tried implementing a notch + low pass filter at the servo input. This succeeded in squashing the 730kHz peak, but also lost us a few precious degrees of phase margin at the UGF. As a result, we still saw instability above 25dB common mode gain. The notch filter is no longer in the circuit, but will reside in Cheryl's office for a while in case someone finds it useful later on, or wants to modify it e.g. to make the notch Q higher. We discussed possible causes for the 730kHz feature - it may be related to the feature in the FSS OLTF measurement shown in entry 5093, though we couldn't be sure of the frequency axis in the attached plot. We have also reduced the common mode gain for now to 20dB, to keep the phase margin around 45deg. This leads to our new 'standard' locked high gain mode:

'Standard' High gain mode

• Common mode gain = 20dB
• Common mode boost filter 1kHz/20kHz ON

Maybe once we get an autolocker script running we can have the above settings as the final state (for now).

The notch filter design, made by Matt, is attached, along with a picture of the box itself, in case anyone wants to use this in future and wonders what it looks like.

• Apollo at EY preparing for in-chamber cleaning
• IO team worked on the mode cleaner all day (mostly from the CR), interleaving with Hugo's ISI testing at HAM 2 and HAM 3 during the afternoon
• It appears that the mode cleaner will remain locked overnight and the LVEA will persist in modified laser safe, with the curtained area in laser hazard
• Ace serviced the portapotties along both arms today
• Alarms:  Dust 15 (9:07, 10:57, 12:05, 12:09), Dust 8 (12:04), H1CDS_IOP_SUS_WATCHDOG (several between 10:45 and 12:30).
• Note the a-logs about the move of the BSC1 SUS today. 
• At 16:00, the H1CDS_IOP_SUS_WATCHDOG alarm tree shows red for ITMY, SEIB1, SEIB1DACKILL, and IPC, and yellow for ETMY
• Work permits signed by ops today:  3672 (BSC1 illuminator), 3671 (BSC1 illuminator and video viewports), 3669 (SUS TF scripting), 3666 (ICC at BSC10), 3665 (leave input arm under rough vacuum, pump HAM 6 (see Kyle's entry below)).

Mark B.

Deepak centered the OSEMs on PRM and PR3 so I rechecked settings and got the damping working. I noticed that the WD thresholds had not been set nor the filters enabled, so I fixed that and redid the safe.snap files.

Damped and undamped TFs for both will commence shortly and continue through the night. The respective Measurement Status indicators will light when a measurement is in progress.

I'm using the beam that is transmitted through the bottom periscope mirror to monitor the IO beam pointing.  The beam is the pick off for the OSA, and is normally (and currently) blocked when not in use for diagnostics.

The ITMy in BSC1 has been moved 8mm in the -Y direction to place it in its correct position.  An attempt to improve the yaw of the suspension was also made at the same time, but will need to be rechecked upon re-suspending after SEI completes their work.

The 8mm axial position error of the ITMy was adjusted this morning.  The Axial position is now 33175.7mm (distance from the total station setup at y manifold), which is 0.7mm East of the ideal position (33175.0 mm) and well within the ±3mm tolerance for axial position.  We also did an approximate 1.3 mrad CCW yaw correction.  This is a rough calculation since the ITMy was left locked, therefore no accurate numbers could be measured for the current lateral & vertical positions and pitch & yaw of the optic.

Volume to be left unpumped but under vacuum until further notice

The IMC lost lock tonight at about 4:00 AM local time. It is not clear why (no big drift in the control channels).

We had trouble recovering lock this morning, unitl we discovered that there were problems with the windows machine controlling the slow digital system.

After we reset the system, restore the working settings on the common mode board and readjusted the delay line value (I'm stressing this as the default setting after a reset of the system results in almost all the signal being in the Q quadrature, with a consequently unusable error signal... good to keep in mind!), we were able to reacquire lock very easily.

WP3668

Thursday afternoon Dan from LDAS upgraded the last of our QFS file servers to Solaris 11.  During the outage only h1fw0 was writing frames. Since the related h1nds0 is the default NDS so the data gap should not be noticable.

Giacomo, Paul, Keita, Hugo, Matt, Lisa

The IMC is locked and happy.
The stability problems were due to the ISI, Hugo put it in a configuration which allowed us to recover a stable lock.

We measured the open loop TF of the whole system, it was stable up to 30 kHz UGF.
We also measured the cross-over VCO/MC2_M3: it is about 15 Hz (it can be stable as high as 100 Hz).

The MC2_M3/M2 cross over is well below 1 Hz.

A detailed entry with the measured transfer functions and gain settings will follow.

We also centered the WFSs on IOT2 and found that a 90/10 beam splitter was used instead of a 50/50 in front of WFS_A, 
explaining the factor 10 power difference between the two WFSs.

We leave the IMC locked for the night, and we should be able to start checking the WFSs signal path tomorrow.