J. Kissel, J. Betzwieser

No rocket science here, but I wanted to post to an aLOG such that we have a convenient reference to cite. Recall that the latest ESD linearization algorithm is described in G1500036, and we're using a simplified version of said algorithm because we do not compensate for charge, namely, when the ii'th linearized quadrant's output is
Vii = Vb * (1 - sqrt( 2 * ( (Fii / Vb^2) * G_ct + 1 ) ) )
where Vb is the bias voltage, Fii is the digitally requested ii'th quadrant's force input to the linearization algorithm, and G_ct is the EPICs record representing the linear force coefficient.

Since even this simplified linearization function is rather daunting to gather intuition about signs, I've made a few plots demonstrating how the algorithm plays with a 100 [Hz] frequency, 10 [ct] amplitude sine wave input request, showing both the output of the algorithm and the resulting force on the optic. The 10 [ct] was chosen because that's roughly what I see requested out of LOCK bank during low noise for both detectors. I've used LLO's numbers for the force coefficient EPICs record (G_{ct} = +/- 512000 [ct]) and bias voltage (Vb = +/- 127999 [ct]). 

As the title suggests, the sign of the output of the linearization algorithm signal gets flipped w.r.t. its input, regardless of the bias sign. 

This impacts the reconstruction of CAL-CS and therefore h(t),  in that LLO uses linearization and LHO does not, and it hasn't been included in the matlab model of the IFO to-date. It also is a piece to the missing sign puzzle (LHO aLOGs 21627 and 21703): there are therefore three polarity flips one must deal with in the ESD chain: the sign of the bias voltage, whether the linearization is on or off, and that the ESD itself is an inherently attractive actuator. It's those pieces that hadn't been considered in detail, which has result in the confusion between LLO and LHO's reconstruction of the actuation path -- at least on the TST / L3 stage.

Lockloss @ 17:53 UTC.  Likely due to 6.5 magnitude EQ in Chile.

LDAS switch has failed over the weekend, due to be replaced.  This caused several sites to be unavailable (Omega glitch plots and summary pages to name a few).

VE will need access to X-2-8 this week.  Will notify operators.

HFD on site tomorrow for annual fire inspection.

Air compressor isolators in hand.  Installation on hold until further notice.

Tuesday maintenance activities scheduled for tomorrow:

• TCS chiller forklifting in mechanical room
• Solar panel install at end stations
• supply fan 3 bearing repair
• LN2 delivery (one is also scheduled for Thurs.)
• GDS pipeline install for calibration
• SYS DIAG guardian work
• photo record of CDS racks
• sweep of LVEA for things not attached to IFO
• PEM STS2 vault maintenance
• HEPI fluid level check

The Master switch needs to be closed so Guardian has the setpoint wrong.  Not sure how long this has been as the channels are not trendable.  Maybe guardian needs a reload, or an init cycle.  Otherwise, not to worry until out of lock to try these guardian fixes.

Title: 9/21 Day Shift 15:00-23:00 UTC (8:00-16:00 PDT). All time posted in UTC.

State of H1: Observing

Outgoing Operator: Jeff Bartlett

Summary: Locked in Observing for ~9 hours.

   Laser Status:

Activity Log: All Times in UTC (PT)

07:00 (00:00) Take over from TJ
07:09 (00:09) IFO locked at NOMINAL_LOW_NOISE, 22.7W, 71Mpc
07:16 (00:16) Set Intent Bit to Observing 
08:17 (01:17) ETMY saturation
08:36 (01:36) ETMY saturation
09:43 (02:43) ETMY saturation
12:03 (05:03) ETMY saturation
13:33 (06:33) ETMY saturation
14:41 (07:41) ETMY saturation
14:45 (07:45) Christina moving 1-ton truck from Carpenters shop to LSB
15:00 (08:00) Turn over to Travis


End of Shift Summary:

Title: 09/21/2015, Evening Shift 07:00 – 15:00 (00:00 – 08:00) All times in UTC (PT)

Support: None needed

Incoming Operator: Travis

Shift Summary: 
- 07:09 Relocked IFO after Lockloss (possible 6.3mag EQ in Chile. Set the Intent bit to Observing at 07:16 (00:16).
- Smooth Owl shift last night. IFO locked in NOMINAL_LOW_NOISE at 22.7W with 68 to 72Mpc range for 8 hours. No significant seismic events during the shift. The wind was fluctuating between 20 plus mph and single digit speeds during the shift. This morning wind speeds are back up to high teens to low 20mphs. 
   6 ETMY saturation events during the shift, with minor effect on range.

Looking at the past 12 months of laser output power trend data (see image PastYear.png).  During first long stretch
between 10-21-2014 and 5-10-2015, of 202 days, the output power decay is approximately 10 mW/day. Going by a crude
fit by eye.  The second stretch which coincides with when the diode current was last increased, the output power
decay is approximately 20 mW/day.

Also attached are trends from the past 120 days.  The image Fit120.png shows the regression fit to the data as
given by Grace.  The fitted decay rates are ~15 mW /day and ~20 mW/day.  So for the ~90 days of the observing
we might lose ~1.8 W from the laser.  Which would bring the power into the IMC accordingly.

At some point we need to ask ourselves at which point do we increase the diode current to up the laser power
to preserve the status quo?  Alternatively is a ~1.8 W power loss by the end of the run, enough to worry about?

   H1 in Observing mode for past 4 hours. Wind has dropped to a light breeze. There was some low frequency seismic noise at END-Y for the past two hours (could be wind related) that has tapered off. Three reported ETM-Y saturations over the past 4 hours.
   IFO is stable with a 74Mpc range. All appears normal.      

Transition Summary:
Title:  09/21/2015, Owl Shift 07:00 – 15:00 (00:00 – 08:00) All times in UTC (PT)

State of H1: At 07:09 (00:00) ReLocked at NOMINAL_LOW_NOISE, 22.7W, 71Mpc

Outgoing Operator: TJ

Quick Summary: At the shift change TJ was relocking the IFO after Lockloss. 07:16 (00:16) set the Intent bit to Observing. Seismic activity is ringing down after 6.3 mag EQ in Chile. Wind is mid-teens to low 20mph.  

Title: 09/20 Eve Shift 23:00-7:00 UTC (16:00-0:00 PST).  All times in UTC.

State of H1: Relocking

Shift Summery: Relocked after some high winds and then stayed locked for 6+ hours. Small issue with a RF45 EOM driver that took us out of Observing while Stephan fixed it. Lost lost at 6:20 and have been on our way back up since.

Incoming Operator: Jeff B.

Log:

• 23:27 GRB, Not locked at the time
• 0:08 Observing
• 1:58 Out of Observing to fix Non Stationary noise (alog21709)
• 2:17 Observing
• 2:45 ETMY saturation
• 2:59 Stephan reloaded ISC_LOCK. This was necessary for the DOWN state to be able to return to the proper settings.
• 3:33 ETMY saturation
• 3:44 ETMY sat.
• 3:53 ETMY sat.
• 5:25 ETMY sat.
• 6:19 DHARD Y Boost ON, out of Observing
• 6:20 Lockloss

Lockloss @ 6:20 UTC

Terramon showed a 6.3 earthquake, and when I saw LLO go down I turned on the DHARD Y boost as Sheila suggested in alog21708 at 6:19. A minute or so later we lost lock. I'm not sure if the earthquake brought us down, the new boost, or something else entirely.

There is a problem with the network switch connecting LDAS to GC in the DCS room in the onsite warehouse.

This means the cluster head nodes, ldas-grid, ldas-pcdev1, detchar, and the nds2 server at LHO are unreachable.

This may be why the summary pages are not updating.

However the computers are up and jobs are running.

I've been to the site, talked with the operator, then walked from the control to the warehouse to check on the network switch. It appears to be dead. (See my email below.)

Also, ldas-pcdev2 and the web server (located in a different room) are up and reachable and can see the data for the summary pages. I've contacted Duncan Macleod to see if there is away to get the summary pages to update again, using the working connections.

We may not be able to replace the broken switch until tomorrow.

Note that this does not affect the flow of data to LDAS at LHO or CIT.

-------- Original Message --------
Subject: Re: [DASWG] Re: Problem with the head nodes at LHO
Date: Sun, 20 Sep 2015 20:39:06 -0700
From: Gregory Mendell <gmendell@ligo-wa.caltech.edu>
To: daswg@ligo.org
CC: LDAS_ADMIN_ALL <ldas_admin_all@ligo.caltech.edu>,  "detchar@ligo.org" <detchar@ligo.org>

On 9/20/15 7:16 PM, Gregory Mendell wrote:
> The problem appears to be that nds, ldas-grid, and ldas-pcdev1 are
> unreachable from outside the internal ldas network.
>
> These computers are up and jobs are running.
>
> I will be checking on the GC switch in the ldas room at LHO once I get
> out to the site (in about 30 minutes).

The switch has no link lights on any of its copper or fiber connections
and no indication it is getting power.

Power cycling and pushing reset button several time did not work.

Moving power cord to another circuit did not work. (Other switches and
computers are all up and showing lights on the same circuits, so it was
unlikely this would have worked anyways.)

I'm in touch with Dan Moraru. If we don't have a spare we'll have to
replace the broken switch tomorrow.

Regards,
Greg
 

While I was investigating alog21712 I found that the ISC_LOCK Guardian node went into error at 22:43 UTC.  "AttributeError: 'REFL_IN_VACUO' has no attribute 'failure' ". Seems like a code error but I don't see an log if it was fixed or just reloaded or what. I will investgate further when I get a chance.

The DIAG_MAIN node will go into error a little less than once a day, and report:

File "/ligo/apps/linux-x86_64/cdsutils-497/lib/python2.7/site-packages/cdsutils/avg.py", line 67, in avg
2015-09-21T01:10:35.46180     for buf in conn.iterate(*args):

RuntimeError: Requested data were not found

(screenshot attached)

While this only requires the operator to reload the node, the cdsutils avg package is used in other nodes such as ISC_LOCK and OMC_LOCK (and others that I can't think of off the top of my head). This inconsistancy also omits its use in the DIAG_CRIT node, for fear that it will not be able to find the data, bring the node into error, and then out of Observation.

Operators: Please log and screenshot the Guardian log any time that a Guardian node goes into error. This will help us diagnose the problem, or others, faster.

It was noted recently elsewhere that there are a pair of lines in DARM near 41 Hz
that may be the roll modes of triplet suspensions. In particular, there is
a prediction of 40.369 Hz for the roll mode labeled ModeR3.

Attached is a zoom of displacement spectrum in that band from 50 hours of early 
ER8 data. Since one naively expects a bounce mode at 1/sqrt(2) of the roll mode,
also attached is a zoom of that region for which the evidence of
bounce modes seems weak. The visible lines are much narrower,
and one coincides with an integer frequency.

For completeness, I also looked at various potential subharmonics  and harmonics
of these lines, in case the 41-Hz pair come from some other source with non-linear coupling. 
The only ones that appeared at all plausible were at about 2/3 of 41 Hz.

Specifically, the peaks at 40.9365 and 41.0127 Hz have potential 2/3 partners at
27.4170 and 27.5025 Hz (ratios: 0.6697 and 0.6706) -- see 3rd attachment. The 
non-equality of the ratios with 0.6667 is not necessarily inconsistent with a harmonic
relation, since we've seen that quad suspension violin modes do not follow a strict harmonic 
progression, and triplets are almost as complicated as quads. On the other hand, I do not see
any evidence at all for the 4th or 5th harmonics in the data set, despite the comparable strain
strengths seen for the putative 2nd and 3rd harmonics. 

Notes:
* The frequency ranges of the three plots are chosen so that the two peaks would
appear in the same physical locations in the graphs if the nominal sqrt(2) and 2/3 relations were exact..
* There is another, smaller peak of comparable width between the two peaks near 27 Hz,
which may be another mechanical resonance.
* The 27.5025-Hz line has a width that encompasses a 25.5000-hz line that is part of a
1-Hz comb with a 0.5-Hz offset reported previously.

Daniel, Evan

We looked at the DARM spectrum in the vicinity of the OMC dither line (at 4100 Hz) and its second harmonic (at 8200 Hz) using the OMC DCPD IOP channels.

The spectrum around the line itself appears to be bilinear, perhaps as one would expect (if the OMC is exactly on resonance, there should be no first-order modulation of the transmitted power). The second harmonic of the line is quite clean, with no obvious upconversion. Is this what we should expect?