yesterday we noticed that ITMX has been tripping, it seems to happen within a minute or so of becoming fully isolated.  HEPI seems to have position loops running, there is no feedback from ISC to the suspension or HEPI.  The last few trips have been just stage 2, actuator trips.  It looks like something is ringing up.

The stage 2 blends were on Tbetter expect RZ, which was on Tcrappy for the two trips plotted in the first screenshot attached.  I've tried setting stage 2 blends to start, this also caused a trip which is the second attached screenshot.

Now I have set the guardian to isolated_damped, so that stage 1 is isolated and stage 2 is damped.  So far its not tripped. 

[Fil Arnaud]

Few days ago I realized SRM top mass dials were moving more than usually, so I took a spectra this morning which shows noise at around 1700Hz for LF RT SD and T3 osems signals. Those four osems are using the same quadrupus cable from the flange to the sat box. The spectra compares those four osems with SR3 RT SR3 SD SRM T1 and T2, which shows a peak at 1700Hz but much less higher.
We tried powering down the AI chassis and the coil drivers several times, which didn't fix the issue. I don't recall we powered down the AA chassis, so that might be the next thing to try. 
To be fixed.
 

I increased the laser power incident on IMC from 2 W to 10 W. I readjusted the IMC locking parameters and updated the IMC guardian. The IMC now locks fine.

In attendance: Fred, Vern, Koji, Sigg, Krishna, Worden, Jason, Patrick, Warner, Kissel, Sudarshian?, Arnaud, Kuwami, Gerardo, Sheila, Fil Alexas

OpLev - HAMs 2&3 complete

HAM6 -cabling completed. ISI will be unlocked for J Kissel to run TF. Jim will run TF as well and Koji will attempt to get OMC locked today so that doors can begin to be reinstalled on Monday. North door will be first. Checking for ground loops needs to be done.

TiltMeter at End-X -complete. Communication regarding activities at End-X needs to be addressed. ie, technical cleaning crew frequency. Possibly some signage at the VEA door was mentioned.

End-Y -Measurements taken during green light exposure revealed that charging is NOT being caused by green LASER. The next step will be to investigate ION pump effects.

Visitors next week: Nic Smith will be here 8/26 through 9/10

model restarts logged for Thu 21/Aug/2014
2014_08_21 18:27 h1fw1

unexpected restart of h1fw1

- Kapton washers to prevent picomotor sticking were installed on the HAM6 picos in the morning.
- Cable grounding were checked with Dan after Jim's cable rerouting in the evening. (Entry below)

The last ISC task before puting the north door is alignment of the OMC leakage trans beam on the northwest viewport (emulator).
With 2W PSL input, corresponding to 3~4mW on the OMC, I expect 20uW transmitted when the OMC is locked and well aligned.
It is probably tough to find.

We might just barely be able to see this beam with a CCD + zoom lens. Otherwise, we need to rely on increasing the input power to 10W.

Dan, Koji

After Jim finished working on the seismic platform, we checked the HAM6 electronics for ground loops.  We re-discovered the grounding of the beam diverter shields in the vacuum, and found another short on the shield for the ASC-AS_C QPD.  The beam diverter grounds appear to be due to the cable connector on the diverters themselves, and I think I recall that we essentially resigned ourselves to living with them.  Koji fiddled with the cables and the connectors for the AS_C QPD and the ground loop went away; all of the ISC and tip-tilt connections to HAM6 are free of grounding issues.  (We did not check the OMC SUS cabling, should do this tomorrow.)

Once we finished with the ground loops we checked the dither for the OMC PZT was functional.  We set the dither frequency at 3.3kHz and toyed with the amplitude while trying to understand the LV readback on the OMC control screen.  The numbers didn't make much sense to us (we need to understand what's going on in the PZT driver board), but we verified that there was a signal coming out of the driver board and going into the vacuum.  Tomorrow we will try to lock the OMC.

When we looked at the low-voltage PZT drive with an SR785 we immediately noticed an 8Hz comb in the spectrum, which has been observed previously at LLO.  The comb is mostly at high frequency and seems to depend on the amplitude of the drive, but it's loud and messy and it's on the DAC input to the PZT driver board.  The attached plot is an amplitude spectrum of the signal from the AI chassis on the input to the driver; note the units are in amplitude, not amplitude spectral density, because we were trying to understand the calibration of the digital controls.  The amplitude of the dither in the plot may be much higher or much lower than what we ultimately use to control the OMC; at LLO they use 0.3V but we don't yet understand the calibration of our input signal.  An oscilloscope trace of the signal leaving the PZT driver and going into the vacuum looks very noisy, with many periodic sharp glitches of ~1microsecond duration that are presumably the source of the comb in the frequency domain.  (Note: the comb is also visible in the LV readback of the PZT drive, using DTT.)

Sheila, Kiwamu

We spent some time this evening to find the POP beam. We successfully found the POP beam and managed to extract it to ISCT1.

We realigned the down stream because we had touched PR3 to get the POP beam. Now REFL, POP and AS beams are all coming out of the chambers.

POP beam:

With the use of an analog camera, we became able to see the POP beam hitting the swiss cheese baffle in HAM2. It was too high and off toward left in the camera view. We temporarily placed the camera at 3 o'clock position at HAM3 spool. This allowed us for steering PR3 to get the POP beam coming out to ISCT1. Note that we could not see the spot with the GigE camera somehow.

We then placed an analog camera in the POP path on ISCT1. This is now blocking the POP beam opn the table, but serving as a reference. Also, touching ITMY, we got the Michelson fringing.

Re-alignment:

Since we touched PR3, we had to realign the downstream. We touched SR3 and SR2. We tried to center the beam on the left part of the SR2 baffle, but this resulted in DAC saturation in SR2 when centering the beam on SRM by steering SR2. So at the end, we gave up the centering of yaw of SR2 and brought it back to where it was. This released the DAC in SR2 as expected and we then could steer SR2 into SRM easily. We confirmed that the beam was hitting AS_A, _B and _C QPDs. The attached is the screenshot of the current alignment.

Since we are not super-confident with the SR3 alignment at this point. The HAM6 crews can feel free to revert the entire alignment, if they want to.

J. Kissel, K. Venkateswara

We did some very basic analysis of the data from the BRS_RY_OUT and the T240_X channels. The first attached plot shows the ASD of 5000 seconds of data from this afternoon. There was good coherence between the BRS and the T240X but there seemed to be a scale factor mismatch. The phase between the signals was very nearly zero. Since I believe BRS calibration is superior :P, I chose to apply a fudge factor of 0.62 to the T240X. To do the subtraction, I simply took the T240X velocity time-series data, differentiated once to convert to acceleration and divided by g. This was then subtracted from the BRS_RY_OUT time-series data, whose ASD is the light blue curve shown in the first plot labelled as 'simple subtraction'.

The second file shows an ASD plot of the raw T240X, the tilt-subtracted T240X and the T240 spec. in displacement units. Note that the weather was rather mild in the afternoon and the tilt noise can get much worse under high wind speeds.

12,185 process variables added
3,163 process variables removed
2,303 process variables are now unmonitored

Plot of pressure after 1 day on turbo pump, charge test is ongoing.

J. Kissel, K. Venkateswara, R. Schofield, S. Karki

Robert didn't believe that we can use our change in gravity gradient to damp the rung-up 8.8 [mHz] oscillations in the BRS, so we performed a demonstrative test in his presence. 

With Krishna himself as our test mass, he
(1) Waited for the balance to come to an equilibrium position,
(2) Moved in next to the North (+X) side of the sensor and squatted there. His approach created a bit of torque noise, but more importantly created a change in local gravity, changing the equilibrium position of the balance up because his squatted C.o.M. is slightly higher than the beam. 
(3) Stood up, increasing his center of mass much higher. This causes little-to-no tilt/torque and again changes the local gravity gradient shifting the DC equilibrium position of the oscillation to shift up. 
(4) Squatted back down, restoring his center of mass to the original location. Again there is a quick bit of torque noise as he squats, but one can see the DC equilibrium position has shifted back (roughly) to it's original location.
All of these changes in C.o.M. served to excite the 8.8 [mHz] mode, which is why you see the amplitude of motion increase at each change.

The first attachment is the time series of the tilt readout, and the second is pictures of the two positions.

Checked out both HAM2 and HAM3 optical levers today.  No major problems with either, only thing was the transmitter telescope pitch/yaw adjustments for both oplevs were not locked down so they both had significantly drifted (completely off the mirror, no return back on the QPD).  This was rectified; both oplevs were realigned and locked down.  Beam profiles and power measurements were done for both (will attach a comment tomorrow with this info, left it all in the LVEA...).  New calibrations were NOT attempted as this requires moving the ISIs; will need to find a window between commissioning work (maintenance Tuesday perhaps) and sit down with someone from SEI to do this.

08:15 LVEA is LASER SAFE 

08:30 Automated message about 200 West Area Emergency Drill - e-mail sent out LHO-All

08:44 Vacuum status is normal IFO wide. Corner station is pumping down and currently at 10 ^-6 torr.

09:04 Travis -out to LVEA to look for cable clamps for Jim

09:17 Gerardo -down to End-X to test power supply for ION pump

09:18 200 West Area Drill is terminated

09:20 Praxxair in for N₂ delivery

09:30 Visitor arrived on-site for tour

09:40 Cyrus-to End-X to check out FMCS "thing" ?

09:54 Dale -will be bringing in a tour group around 11:00

09:56 Koji - into LVEA for capton washer installation in HAM6

10:13 Cyrus - back from End-X

10:18 Jason -OpLev work @ HAM3. Also cable swap on SR3

10:30 Gerardo -back from End-X

10:37 Cyrus -Back out to End-X to swap parts

10:38 Praxxair out

11:02 Cyrus - returns! (cue music and credits)

11:15 Tour group in control room

13:27 Gerardo -to End-X to test ION pump power supplies

13:45 Cris - cleaning at X-End

14:40 Cris - back from End -X

15:30 LVEA IS LASER HAZARD

@ ~15:30 LVEA is LASER HAZARD

Vacuum pump (located in the mechanical room) that feeds some of the dust monitors is no longer working. Trying to locate old unit.

Filiberto Clara

K. Venkateswara, J. Kissel

Noticed BRS had been rung up with X-End activity (see LHO aLOG 13533).
- Gravity dance to damp the 8.8 [mHz] mode
- Changed very-low-frequency high-pass from 1 [mHz] to 0.5 [mHz], to improve signal fidelity for subtraction. 1 [mHz] was adding ~10 [deg] of phase to the signal at 10 [mHz] -- too much in the region we wish to use the BRS signal for GND T240.
- restarted code at ~11:45p PDT

Notes for future gravity dances:
- When Tilt signal is on the upper-half of its sign wave, one needs to stand on the North (+X) side, if lower-half on the south (-X) side.
- Transition, or start standing on a given side at the amplitude peak
- As the resonance gets damped, you need to stand on a given side for less and less time
- +/- 500 [ct] amplitude = need to stand on one side for a full half cycle (~30-50 seconds), +/-50 [ct] amplitude = only a few seconds at a time
- +/- 25 counts is good enough. 

Note on determining frequency for high-pass: 
- filter coefficient = (1 - (desired freq)/(sampling freq))
- Sampling frequency = 50 [Hz], desired frequency = 5e-4 [Hz] ==> filter coefficient = 0.99998;