Since the ETMX L1 L2P filters gave us a unstable x-arm lock once ALS-DIFF was engaged, we switched to a DC-only strategy:
 - Instead of the the L2P/L2Y filters we simply used flat gains, and tuned them at 0.1 Hz:
     Pitch: -60dB (FM10) * gain of  5.3
     Yaw:   -60dB (FM10) * gain of -0.7

 - We also tweaked the ESD L2P/L2Y's at 2Hz:
     Pitch: gain of 0.021
     Yaw:   gain of 0.007

 - This left some AC pitch fluctuations on ETMX. The OPLEV took care of that. We now have a stable ALS DIFF and COMM running in this configuration.

model restarts logged for Sun 23/Nov/2014
2014_11_23 02:27 h1fw1

one unexpected restart. Conlog frequently changing channels log attached.

On the way to better initial alignment automation, there are some new scripts for TMS alignment in:

/opt/rtcds/userapps/release/asc/h1/scripts

they are alignTmsxDither.py and alignTmsyDither.py which use baffleAlign.py.  These are still a work in progress.  After testing is done, we will need to incorporate them into the IAS guardians.

The usual scripts (e.g., alignDitherFull.py) should be as before, and backup copies are in old_2014-11-24 just in case.

Matt, Dan

After Alexa gave us a quick alignment tutorial, we started by fiddling with the dither alignment of the X-arm.  The PD thresholds for dithering across the baffle PDs were set to very small values, so small that the dither would declare victory before it even started.  Matt has been working on the initial alignment, I'll let him say more about it.

We noticed that the green spot on the TMS-Y mirror, visible through ETMY, is very low.  There are large offsets in the EY green QPDs that steer the beam to what looks like a bad place on the mirror.  Zeroing these offsets (which is where they were for most of the last six months) would have forced us to begin a painful realignment procedure, so we left them as we found them.  Historically it looks like people have set these values to maximize the buildup in the arms, but it's hard to believe that the optimal beam position is so far off-center.

With the arms well-aligned for green we aligned the corner optics - IM4, PR2, PRM, BS, SRM.  The scripts for this went quickly, about five minutes.

Then we locked the DRMI, with the arms misaligned.  Locking tonight was fast and robust; the DRMI would lock within a few minutes (rarely more than 5 minutes), and would remain locked for tens of minutes.  There were many unexplained lock losses, so things are not as stable as we'd like, but we didn't see any mode hopping and the sideband buildup was consistently good.  Over three hours of DRMI locking we didn't observe a significant drift in the alignment.

We went through the DRMI guardian and commented out lots of gain/switch settings that weren't needed, mostly for the DC centering.  The script is now pretty fast, it goes from lock acquisition to ASC loops on in less than 30 seconds.  We did not observe any unexpected long pauses.  The duration of the script is dominated by ramping the SRM and PRM M2 gains, this takes 9 seconds total (4.5sec each).

We re-enabled the PRM and SRM2 offloading to M2.  We found the SRM offloading was a little flaky and sometimes broke the lock.  To make this a little gentler, we reduced the initial gain ramp to 1, and ramped the rest of the way (to 4.5) after the WFS turned on.

We measured the LSC OLTFs and found that MICH and PRCL didn't have much phase margin (~25deg each).  We reduced the gain for these loops so that they both have >30deg.  The MICH gain is now 3 (was 5) and PRCL is 15 (was 22).

Afterwards I mucked around with the OMC, I found a set of good misaligned values for ITMX and ITMY that minimized the RIN at the dark port when the other ITM was aligned (presumably this steers ghost beams away from the OMC).  Following Gabriele's instructions I used the picos to center the beam on IMC WFS A and added some offsets to the IMC ASC loops; this reduced the intensity noise measured by the ISS second loops PDs by a factor of three or so.  I tried to engage the ISS second loop but failed.  The script posted here did not appear to work; I tried to follow these directions but the loop was unstable.

Plots attached are MICH, PRCL, SRCL loops before we reduced the gain to get some phase back in MICH and PRCL.

no restarts reported.

conlog frequently changing channels list attached.

(Alexa, Evan, Stefan, Matt)

The ETMX bounce mode has been limiting us in locking ALS DIFF, and causes us to lose lock when the ESD saturates. The first attachment shows the coil outputs of the stages, and there is a clear peak in the ESDs (note this screen shot was taken with a much lower gain in DIFF and with the boosts off; this peak causes saturation when the DIFF gain is nominal). The second attachment shows the bounce mode appearing in the oplev spectrum. You can see that this mode starts to appear Friday and gets worse into today. Thursday night the mode looks fine, which explains why we were able to lock DIFF Thursday night. At some point Friday afternoon we turned off the ETMX L2 oplev damping; however, we see this mode ringing up before this was switched off.

no restarts reported.

conlog frequently changing channel report attached.

(Sheila, Evan, Dan, Kiwamu, Stefan, Alexa)

We were able to lock DRMI + arms off resonance a few times tonight, but the alignment was not great and we would mode hop and lose lock. The guardian is slow to engage the asc wfs, which usually help save the alignment and get the ASAIR build-up high. We need to take a look at our guardian script to get them to engage faster. We did not get a chance to try bringing the offset in and transitioning to TRX+TRY.

The other problem is that DRMI + arms off resonance takes a while to lock (around 20 min), and ALS DIFF is not staying locked for much longer than that. Nic and Sheila worked on a HEPI offloading script (see Nic's alog). However, by the time we got this up and running, ALS DIFF was not locking robustly. For one it seemed we had rung up the bounce mode at 9.8 Hz, which makes locking much more difficult. Another thing we noticed is that the ETMX oplev is glitching.

Of course, as I write this alog, ALS DIFF has been locked for 8 minutes ... unclear what changed.

Nic and Sheila ran Jim's script to run the overnight sensor correction test.

In these two weeks I optimized few times the IMC angular offsets, in order to reduce the coupling of beam jitter to intensity noise. Attached the MATLAB script I used to decide the optimal offsets. It grabs a period of data (of the order of some tens of minutes) and plot some scatter plots of how the band-limited RMS of intensity noise (measured with IM4_TRANS) depends on the IMC angular DOFs. The script parameters are set at the beginning, and the attached one shows the typical values I used.

The typical result is shown in the attached picture. In this case one can see thay intensity noise tends to be samller for positive values of DOF_1_P and negative values of DOF_3_P. My conclusion would be that we need to add an offset of about -20 on DOF_1_P and about 2e-3 to DOF_3_P. I didn't want to interfere with the ongoing locking activities, so I didn't add those offsets now.

We noticed that at least three times tonight, DIFF lost lock because of glitches in the ALS (Y) refl control signals.  The times were 0:18:12 UTC, 1:35:00 UTC, and 1:47:29 UTC, we didn't investigate all of the DIFF lock losses we had tonight so there could have been other examples.  The glitches were both more frequent and larger in the Y arm, but there are also glitches present in the X arm (they are independent glitches in the 2 arms).  We see the glitches even without ALS DIFF and COMM locked, they aren't in the optical levers, the PZT signals, or a number of other things we looked at.  

Evan and I drove down the to Y end to look on a fast scope at the glitches.  By the time we got down there, the glitches had largely stopped.