8:05 Kyle closing gate valves in vertex

8:10 Gerardo to LVEA assisting Kyle

8:12 Jim loading new isolation filters on HAM 2,3,4

8:21 Fil to EX, EY working on OpLev wiring

8:25 Vern and Richard to LVEA

8:28 Doug to LVEA OpLev test bed, moving to EX

8:33 Elli to EY HWS work

8:33 Jeff B to LVEA dessicant cabinet work

8:35 Hugh to HAM1 for L4C work

8:48 HAM6 picomotors shutdown for vent

9:20 Peter K to H1 PSL enclosure with Corey

9:31 Richard to LVEA checking Pirani gauge

9:33 Jeff B done

9:43 Vern out

9:49 Porta potty service on site

9:49 Betsy to LVEA

10:02 Jeff B to HAM6

10:13 Corey out

10:20 Hanford FD to LVEA

10:27 Cris and Karn to ends

10:52 Koji, Dan, Ross to HAM6

10:54 OMC and OMs to SAFE, HAM6 ISI to OFFLINE

10:55 PR3 light pipe install and align

11:01 Andres to West bay

11:05 Peter K done in H1 PSL, moving to H2 PSL

11:08 Andres done

11:37 Peter K done

11:58 Doug and Jason done at PR3 OpLev

12:03 Hugh done

12:05 HAM6 open for business

12:07 Elli done at EY

12:20 Dan, Koji, Keita, Corey to HAM6

12:37 Fil installing dewpoint cabling LVEA

12:47 Elli to EX for HWS work

12:58 Betsy to HAM6

13:08 Richard to LVEA

13:09 Betsy out

13:33 Sudarshan to EY for PEM work

13:40 Jeff B to HAM6

14:30 Doug and Jason to EY for OpLev work

14:45 Fil to LVEA retreiving tools

   Attached below are the particle counts taken during the removal of the HAM6 East door. Counts were in line with expectations and in chamber counts below expectations. Checks with people working in and around the chamber all showed to be below the clean-100 levels. Last counts taken in the chamber this afternoon showed 10 0.3 micron and 0 for 0.5 and 1.0 micron particles. 

Checked the crystal chiller water level as per the OPS Tues. checklist.  Noted that it was filled on 4/3 (by Peter K, I assume) and that the level was midway between Min. and Max. level.  No water added.

Replaced non-functioning L4C (L4-C) sn L41367 with L41365.  Looks okay, will continue testing.

How?  Deisolated platform.  Locked only corner2 foot to Caging brace (oh yeah, had to adjust rear caging brace to proper position) w/ ~5mil + bias from Ready state--the Actuators tend to pull a few mils (5-10) from the nominal shimmed position.  Disconnected Actuator from brackets but did not loosen brackets hoping this would help retain position.  This won't always work.  Shimmed and locked down actuator.  Disconnected Actuator from Foot.  Powered down Pier Pod, dewired, and removed it and the holder bracket (to get access to L4C Clamp bolts.)  Removed the two Horizontal Actuator Adapters.  Loosened the three L4C holder bolts, loosened the two L4C clamp bolts.  Left the L4C leveling shims in place since we really level the holder, not the L4C.  Pulled the L4C and clamped in the replacement.  Rewired to check spectra--looked okay.  Dewired again.  Reversed process: Actuator Adapters, Actuator to Foot (worked nicely, all the bolts went in smoothly,) Bolted Actuator to Brackets (Housing,) rewired Pier Pod.  Numbers look very similar to before.  Unlocked Actuator and removed shims.  Unlocked Foot--position within 200 counts of position before.  Reengaged Isolation, no problem.

Now the position could actually be different but I really don't think by much (a few mils at the worst) and I don't think ISC is that sensitive here.  But, feel free to drive it to where it is needed.

D. Cook, J. Oberling

ETMx

We moved the recently tweaked oplev laser (SN 197) from our testbed at HAM3 to ETMx.  This laser will thermally stabilize over the course of the afternoon, then we will start monitoring it to perform, if necessary, the final tweaks.  While we were at End X we installed the 50 lb. lead damper assembly onto the ETMx receiver pylon.  Due to the laser swap and the damper install, the oplev needed to be realigned, so we did that as well.

PR3

At the request of commissioners we realigned the PR3 optical lever.  While out there, we installed the light pipe support assembly (see attached picture) to keep the light pipe on the receiver from sagging.

I was taking HAM's 2-4 down this morning to install higher gain control loops. HAM's 2 and 4 went down and came right back up. HAM3 refused to re-isolate, and it took a while to figure it out. It turns out that HAM3 is restoring a large pitch (RY) offset, and Guardian is restoring this offset at roughly the same time it tries to engage the horizontal iso loops. When it does this it sends a large tilt to the GS13's and trips the ISI. Eventually I got around this by switching the GS13s to low gain, and the ISI came right up, whereupon I switched the GS13s back to high gain. A couple thoughts:

1. We should restore fewer DOFs on the HAM's. It wouldn't have prevented this particular problem, but the ISI doesn't wander much, the HAM's don't trip often. I also think that the commissioners probably only care about a few angular DOF's (sadly RY on HAM3 is probably one) and keeping  historical  x/y offsets only make isolating/de-isolating the ISI's and troubleshooting more difficult.

2. HAM3 is restoring a 4000 nrad offset. We should try to offload this to HEPI. Isolating and de-isolating HAM3 ISI is made more difficult by servoing to this position because it sends a big tilt to the GS-13s, which see it as translation.

3. If we can't risk shifting this offset, we should add GS-13 gain switching to the HAM's. Hugh found this sent an impulse to the BS, but that only mattered because it disturbed Mich. We only maybe need this on HAMs because of the need to restore ISI angular offsets (which we don't do on BSCs) and we don't need to switch while operating the IFO. The infrastructure exists, the SEI group may need to do a tiny bit of thought about how to implement it. We only need to switch when transitioning to and from isolated.

I reset the accumulated WD counter for ITMX.  It had a count of 389.

Attached are the Phase 3b damped and undamped TFs of SR3 taken over the last few months.

The damped TFs of M1 are pretty squashed, but this is because there is some pretty heavy damping filtering engaged for commissioning.

07:28    The LVEA has transitioned to LASER SAFE to facilitate the removal of the doors from HAM6.

In preparation for today's work in HAM6, the inteferometer has been left in a single bounce configuration, with the spots in HAM6 centered on their respective QPDs.

I had to move the OMs a bit. The original slider values are as follows:

The new slider values are as follows:

Sheila, Evan

Summary

By increasing the gains on the common-mode and IMC boards, we pushed the CARM UGF up to 35 kHz and saw a reduction in the high-frequency noise floor of DARM.

Some further loop tuning is required to make this viable as a long-term change.

Details

Based on Sheila's earlier measurement of the IMC OLTF, we felt it was safe to increase the gain at the IMC error point (both the error signal and the AO) by 2 dB. Then we increased the CARM gain by 6 dB (using the IN2 slider on the CM board). These changes gave a UGF of 35 kHz with 25° of phase. [See plot and zip file.]

This gave a noticeable improvement in the frequency noise as seen by REFL_A 9I, which is currently the out-of-loop CARM sensor. [See plot.]

Consequently, there was a small but noticeable improvement in the high-frequency noise floor of the DARM spectrum. [See plot with red and gold, taken while still feeding DARM back to ETMX.] In the full locking configuration, the noise floor now touches the GWINC curve from 300 Hz to 3 kHz [See plot with purple.]

Obviously this CARM phase margin is quite thin, and we don't want to run like this as a matter of course. In order to win more phase, perhaps we need to look at the IMC loop and the FSS. Peter K last measured the FSS UGF to be 200 kHz with 30° of phase (on the low end of the phase bubble). In comparison, at LLO the FSS UGF is 500 kHz with 60° of phase.

More details

Nominal gains are 0 dB for CM IN2 [the CARM error signal], 5 dB for MC IN1 [the IMC error signal], and 0 dB for MC IN2 [the AO signal].

The gains used here are 6 dB for CM IN2, 7 dB for MC IN1, and 2 dB for MC IN2.

At the start of the evening, REFL_A 9I had no whitening filters engaged and 0 dB of whitening gain. It now has 1 stage of whitening, 21 dB of gain and a −21 dB filter engaged in FM4 (I and Q). There is some saturation during the lock acquisition, but in full lock the I and Q inputs are now at least a factor of 5 in ASD above the ADC noise floor everywhere. I also changed the digital phase rotation from 77° to 90°, as was hinted at earlier.

Evan, Sheila

In response to alog 17555 we have changed the L1/L3 crossover for ETMY, similar to what was described in LLO alog 14428.  

We adjusted the plant inversion a bit, increasing the Q of the 3.6 Hz zeros from 6 to 12, added a lead filter (2 Hz zero, 8 Hz pole, this is currently split into two filter banks but can be combined next time we loose lock.)  We were able to push to crossover from  about 0.7 Hz as measured in 17625 to about 2.5 Hz, with about 30 degrees of phase margin.  We also added a boost, with zeros at 0.3 Hz with a Q of 1.5.  (the second lead filter and the boost are in the L2 bank, and are not currently turned on by the guardian.  I plan to move them to the L1 bank before adding them.)

The first screenshot shows two measurements of the crossover, one before the plant inversion was tuned and the second lead was added, and the red one is the configuration now.  The second screenshot shows that the rms ESD drive was reduced by a factor of 2,gain peaking around 3 Hz accounts for about half the rms.  LLO was able to get the rms drive lower, but this is good enough to turn off the ESD linearization.  

We left the IFO alone in this configuration (linearization off) for a few minutes at a time: 8:55 UTC April 7 to 9:03 UTC, and again from 9:41 UTC to 9:57 UTC.  We are going to leave the IFO in single bounce for the vent tomorow, so there won't be any long stretches of data to check for glitches until after the vent.  

Ross Kennedy and Ed Daw.

During the lock around 00:43:42 UTC tonight we took a coherence/cross spectrum measurement between REFL AIR9 and OMC DCPD1. The first figure attached shows the 
ASD in each channel. These were taken remotely using an SR785. 8 800 bin ASDs each covering a frequency span of 12.8 kHz were assembled to cover a total bandwidth of 102.4kHz with 16Hz resolution bandwidth. The second figure shows coherence per 16 Hz bin (above) and the phase of the cross spectral density (below). Note that the peak coherence is around 0.04 per Hz over a 16Hz bin, or 0.64 over the whole bin.

J. Kissel, S. Dwyer

Sheila's taken another DARM open loop gain transfer function just a second ago at my request, such that we can get a handle on how much the loop (and therefore the calibration) has changed since Koji improved the DCPD compensation (see LHO aLOG 17647. I'll process and make a statement tomorrow but I record some details here for the record. 

Parameters needed for Kiwamu's bare-bones calibration model:
DARM Gain = +1300
DARM FMs ON = 1,2,3,4,5,6,7,9

ETMY UIM Gain = +0.2
UIM FMs = 1,2,3,5

The .xml has been copied over and committed to the calibration repository, here
/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/PreER7/H1/Measurements/DARMOLGTFs/
2015-04-06_H1_DARM_OLGTF_LHOaLOG17710.xml

Today I started hacking through the weeds that had grown up the SUS SDFs for the last 2 unattended weeks.  While I still have more pruning to do, I addressed:

- ODC DAMP GOOD state updates on medm and SDF where DIFFs were found - likely more tidy up needed per sus.

- Low noise BIO/COIL changes 17504 and 17478.

- Cleaned up SUS TEST banks (ignoring GAIN, OFFSET, TRAMP values, but continuing to watch SW1 and SW2 for when bank gets left on)

- Found lots of LIMITs engaged, so wrote their values into the safe.snap

- Set SDF to ignore SW2 of many LOCK and TEST banks which were in SDF DIFF state since now SUS GRD aligns and misaligns via these, alog 17259.  Reenabled SW1 monitoring in many cases where inputs will remain enabled now.  Where alignment offsets were written into TEST banks, I've written the values into the sus snap.safe.

- Zeroed out the R0 P TEST OFFSET of 200 that Keita put in a long time ago and inadvertently got written into the ETMx safe.snap and subsequently reenabled.  These should be off, 16865 - Today I turned the R0 P offset off, again.  Also, the R0 Y TEST bank offset (0.0) was enabled so I turned that off.  Our understanding is that no R0 chain offsets should be enabled.

Per JeffK's request, I have switched ETMX to the "windy" configuration. The ISI was already running the 90mhz blend since sometime this weekend. I've now also engaged the low frequency sensor correction on the X direction with the BRS turned on. I've been fiddling a little with the Z blend filters on St1, adding low pass filters to the 90mhz Z blend, but it doesn't seem to affect the St2 performance much. I'll post more on that in a bit.

[Ed. Merilh, Jason Oberling, Doug Cook, Suresh D]

Doug replaced the diode laser at the HAM3 oplev this morning after it was fixed for reducing glitching (SL No. 197) in the optics lab 2.   We wanted to let it settle for a while and reach thermal equilitbrium before adjustting the power level.  We did that around 12:30PM and I checked the results around 4PM.  The laser is still settling down  as seen in the attached plots.  We plan to monitor it for another day.