[Vaishali, Jenne]

We used the last few minutes of commissioning time today to measure the ASC sensing matrix.  This is the first time that we have made this measurement since POPX was installed.  Per JeffK's suggestion, we turned off the 7.9Hz calibration line to avoid confusion with our 8.125Hz measurement frequency (we used his new guardian state that actually turns off all the Pcal lines, then turns them back on before we go to NLN).  

Vaishali is looking at this data to compare with previous measurements, and her Finesse model.

Recall that in the table below, elements that are grayed out have lower coherence.

Sensing Matrix, [W/rad]

Sheila found two issues when modifying the H1ASC.txt filter file this morning:

 1. A change to an existing filer caused foton to freeze up

 2. Loading a change to a filter (which was turned off) onto h1asc caused lock loss

I suspect both issues were due to the fact that today was the first time the h1asc filterfile was being handled by the new version of foton (with the higher number of significant digits in the gain).

issue 1) We later found that the foton freeze up could not be reproduced, perhaps it was because the old format file was being read and modified? We'll see if this error appears in other systems.

issue 2) Since every gain was recalculated with the higher number of digits, perhaps loading all the filters glitched the system enough to cause lock loss? One suggestion is that if a filter file is being changed to the new format for the first time, we should only load all of  the filters on a Tuesday morning (or perhaps perform this full load on every model at that time).

It looks like the drives during ALS DIFF to ETMX are about a factor of 2.5 times larger than they were 2 years ago. 

Kyle, Chandra 

Chandra had freed a bird that had got itself stuck in the "sticky mat" used to trap insects at the X-mid earlier today.  Unfortunately, it flew into the VEA.  Following Keita's Thursday 1 O-clock'ish meeting, we followed up by opening all of the roll-up doors and, with the lights off, persuaded it to exit.  We had to "bump" the crane bridge a few times to encourage the bird to leave - which it eventually did.  (Don't get me wrong.  I'm all for recycling and liberating caught birds etc. but if she next finds a struggling beached whale along the X-arm access road - she's on her own!)

Link to full report: https://wiki.ligo.org/DetChar/DataQuality/DQShiftLHO20170417

Summary below (see full report for details):

• Percentage of time spent observing (95.5%+51.6%+63.4%)/3 = 70.2%
  • planned commissioning in addition to regular maintenance reduced this percentage
• Typical BNS range of around 65-70 Mpc, but degraded a bit by the end of the day on Wednesday (just under 60 Mpc)
• Relatively quiet 50 hz - 100 hz glitching is continuing (reported in previous DQ shift)
• A population of glitches around 25-50 hz appeared on Wednesday, witnessed by the ETMY OpLev? (similar glitches have been noticed before)
  • Also coincident with FEC overflows
  • OpLev damping is OFF.

Yesterday morning I did a few tests of misaligning the OMC and putting excitations on the alignment loops. (see LLO alogs 32885 and comment and 28979 ).  Depending on which method you use to estimate the normal RMS OMC alignment fluctuations, the OMC jitter noise is at least a factor of 2 below DARM or better.

• Misalignments of the OMC did not produce any reproducible noise in DARM without an excitation (first attachment).  The misalignments that I used are smaller than was recently used at LLO. 
• There are three ways (that I know of) to estimate how large the offset was compared to the normal RMS alignment fluctuations: using the in loop error signal, looking at the motion on the QPDs, and the method that Koji described in his alog where the coupling from an an excitation is increased until it the coupling becomes linear and much larger than the coupling due to the normal alignment fluctuations. 

• According to the QPDs and in loop error signals, my offsets were large enough compared to the RMS that we don't need to worry about this noise source. 
• The normal RMS fluctuations that I would estimate based on the change in the coupling of the excitation would be much larger, meaning that this test only assures us that this noise is below the level of DARM by the coupling increase factor.

You can see that the behavior of POS Y is different from the other loops, this is the only loop where my offset was large enough to measure coherence between the excitation and DARM, but it was a small change in the optical gain.  My excitations were not large enough to change the RMS seen on the QPDs (second attachment shows excitation sizes). Our OMC alignment loops are very slow, it takes 2-3 minutes for them to respond to a change in offset.

Some notes on what I think is implied in the LLO alogs:

When we are locked on DC readout the ratio of the optical gains for the misaligned/aligned OMC is the square root of what the ratio of transmitted powers would be if DARM were not locked on the DCPDs (thanks Keita): 

• If we misalign the OMC when we are not locked on DC readout, the ratio of the transmitted power misaligned over aligned is (1-A).
• The power on the OMC DCPDs is held constant by the DARM loop, so the DARM offset changes from L0(aligned) to L1 (misaligned) (P=alpha L0^2=alpha(1-A) L1^2)  This means L1=L0/sqrt(1-A)
• We can measure the ratio of the optical gain for the misaligned OMC/ aligned OMC (kappaC1/kappaC0=(1-A)L1/L0=sqrt(1-A))

My understanding of Koji's method for estimating the rms: (Delta theta is normal alignment fluctuations, dtheta is the excitation, and theta0 is the offset. )

1. Normal contribution to DARM noise is proportional to DeltaTheta^2 (should be smaller than DARM, gold is upper limit)
2. Contribution to DARM noise with excitation but no misalignment is proportional to dtheta^2+2dTheta*DeltaTheta (forest green curves in first attachment) (DARM will not be coherent with the excitation in this case)
3. Contribution to DARM noise with offset but no excitation 2*DeltaTheta*theta0 (should be small, fuchsia curves would be larger than gold reference otherwise)
4. excitation and offset- (2)+(3)+2theta0*dTheta (mint green curves) (DARM will be coherent with excitation if this term dominates over DeltaTheta*dTheta)

I think that what Koji is doing is taking the ratio of (4)/(2) (coupling increase in the table above) and estimating that that is the ratio of the offset/normal RMS. 

Spring enabled the EE shop to work on setting up power for the LEMIs, and I had a look at the new signals. The top plot in the figure shows that we can see Schumann Resonances quite well, up to quite close to 60 Hz. The bottom two plots show some transient signals that might interfere with a feed-forward system.

It looks like the signals are degraded by wind. I am not surprised because we see wind noise in buried seismometers. I think we would have this vibration problem even on a perfect flat because of the variation in Bernoulli’s forces associated with gusts. It may be that a LEMI signal is generated by the wind because of slight motions of the magnetometers in the earth’s huge DC magnetic field. We buried the LEMIs about 18 inches deep (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=29096). I think we might be able to mitigate the noise some by going much deeper.  Once we have the vault seismometer working, it would be a good project to test the wind vibration hypothesis by comparing the LEMI and seismic signals.

There also seem to be some transients, some long and some short, possibly self inflicted by our system. It would be good to look into which transients would be a problem, and for those, details such as whether they are correlated with time of day, the average time between transients, etc., in order to help determine their source.

Finally, I would like to get the full system calibrated by comparing to a battery powered fluxgate magnetometer.

TITLE: 04/20 Owl Shift: 07:00-15:00 UTC (00:00-08:00 PST), all times posted in UTC
STATE of H1: Observing at 56Mpc
INCOMING OPERATOR: Nutsinee
SHIFT SUMMARY:

H1 locked for entire shift. Slight dip in range due to 5.5 Russian quake. Otherwise, non-eventful night.
LOG:

TITLE: 04/20 Owl Shift: 07:00-15:00 UTC (00:00-08:00 PST), all times posted in UTC
STATE of H1: Observing at 61Mpc
OUTGOING OPERATOR: Patrick
CURRENT ENVIRONMENT:
    Wind: 26mph Gusts, 22mph 5min avg
    Primary useism: 0.10 μm/s
    Secondary useism: 0.19 μm/s
QUICK SUMMARY:

H1 freshly re-locked. Modes damped as per Patrick's aLog. a2l shows ETMX out in YAW by ~.68. Will run the dither script at my first convenience.

TITLE: 04/20 Eve Shift: 23:00-07:00 UTC (16:00-00:00 PST), all times posted in UTC
STATE of H1: Observing at 61Mpc
INCOMING OPERATOR: Ed
SHIFT SUMMARY: Lock loss possibly coincident with wind gust at EY. Back to observing. Bounce mode around ~9 Hz is high but damping. Turned on FM6 per Ed's suggestion to damp ETMY violin mode at ~4kHz.
LOG:

23:37 UTC GRB alert. LLO also received.
04:14 UTC LLO lost lock. Out of observing to run a2l.
04:23 UTC Back to observing.
05:59 UTC Lock loss. Wind gust at EY?
06:45 UTC Observing. Turned on FM6 for H1:SUS-ETMY_L2_DAMP_MODE10 and accepted SDF difference (attached). Damped PI mode 27 by changing phase.

Have remained in observing. Range appears to have recovered after initial dip. No known issues.

Evan G., Robert S.

Looking back at Keith R.'s aLOGs documenting a changes happening on March 14 (see 35146, 35274, and 35328), we found that one cause seems to be the shuttering of the OpLev lasers on March 14. Right around this time, 17:00 UTC on March 14 at EY and 16:07 UTC at EX, there is an increase in line activity.

The correlated cause is Travis' visit to the end station to take images of the Pcal spot positions. The images are taken using the Pcal camera system and needs the OpLevs to be shuttered so that a clean image can be taken without the light contamination. We spoke with Travis and he explained that he disconnected the USB interface between the DSLR and the ethernet adapter, and used a laptop to directly take images. Around this time, the lines seem to get worse in the magnetometer channels (see, for example, the plots attached to Keith's aLOG 35328).

After establishing this connection, we went to the end stations to turn off the ethernet adapters for the Pcal cameras (the cameras are blocked anyway, so this active connection is not needed). I made some magnetometer spectra before and after this change (see attached). This shows that a number of lines in the magnetometers are reduced or are now down in the noise.

Hopefully this will mitigate some of the recent reports of combs in h(t). 

We also performed a short test turning off another ethernet adapter for the H1 illuminator and PD. This was turned off at 20:05:16 18/04/2014 UTC and turned back on at 20:09:56 UTC. I'll post another aLOG with this investigation as well.