Laser Status:
SysStat is good
Front End power is 29.79W (should be around 30 W)
Frontend Watch is GREEN
HPO Watch is RED

PMC:
It has been locked 5.0 days, 1.0 hr 36.0 minutes (should be days/weeks)
Reflected power is 1.822Watts and PowerSum = 23.85Watts.

FSS:
It has been locked for 0.0 days 0.0 h and 3.0 min (should be days/weeks)
TPD[V] = 1.432V (min 0.9V)

ISS:
The diffracted power is around 8.727% (should be 5-9%)
Last saturation event was 0.0 days 0.0 hours and 2.0 minutes ago (should be days/weeks)
 

Other than work permits, the morning meeting consisted primarily of Tuesday maintenance planning.  Items for Tues. maintenance include:

• PSL team looking at optical surfaces of HPO
• Richard working on sync cabling for CPS and status of PI
• Bubba shimming crane rails
• Hugh huddle testing of unused STS2s
• Jeff B dust monitor vacuum system work
• PSL front end diode current increase (time permitting)

Aidan here (next week?) for TCS work

Dave O, Elli, and new student here for HWS work

Peter gave us notice of a 2W NPRO running in the staging building triples lab.  Signage and barriers are up.

The X1 DTS has been restarted with the exception of the frame writer and NDS. The LDAS gateway computer seems reluctant to boot, and is required for the frame writer and NDS.

no restarts reported for both days.

There are small glitches very close to each second boundary in the ETMY drive signal and the ETMY SUS ad SEI rack magnetometers.

In order to investigate the half-Hz combs in DARM (see alog 20790), I took an hour of data and folded it with a four-second period. If there is a repeated glitch at any multiple of this period, it should become far more visible. The result is that in several channels, there are glitches very near the boundary of each GPS second. The peak time of these glitches seems to be about 10 milliseconds after the start of the second. The glitch does not repeat identically every second. There is one shape in the first second, then one with an opposite polarity in the next second.

The first two attached plots are for the SUS and SEI racks, which are shown with a 40-Hz zero-phase lowpass. The SUS has a narrow spike, and the negative spike is larger than the positive one. The SEI signal is more complicated. The ETMY L3 MASTER signal, which is the DARM output to the ESD, is shown with a 10 to 50 Hz bandpass. These glitches are more like sine-Gaussians, but the even and odd seconds still seem to have opposite polarities.

There are more channels with similar glitches. We can make a more thorough investigation, and use more data and more times, to try to track down the origin of these glitches. Hopefully these glitches are responsible for the 0.5 Hz combs such that removing them will improve those.

An electromagnetic shaker on the blue cross beams of the BS chamber produced greater upconversion than was produced by shaking of any other chamber or the PSL table (ITMY wasn’t shaken) (https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=24194). I unsuccessfully tried to reproduce this upconversion using stage 2 ISI injections in X, Y and Z (I did not try RX, RY or RZ). Next I investigated the upconversion by injecting single lines with the EM shaker on the BS cross beams in order to find the most sensitive frequency band. Figure 1 shows the line injections that produced the most upconversion; they are located between 40 and 65 Hz. Lines injected with amplitudes between 1 and 2 orders of magnitude greater than normal produced broad features around the injection frequency and at harmonics, with amplitudes that were several times background in DARM. The next step will be to inject uniform bands in order to estimate the contribution of the 40-65 Hz vibration background to the DARM noise in the 80-200 Hz band. 

I spent some time looking at how we can reduce the DARM residual.

In the attached plot (template lives in evan.hall/Public/Templates/LSC/DarmResReduce_2015-01-23.xml), yellow shows the nominal DARM residual and estimated freerunning displacement.

Blue shows the residual after the addition of a 3 Hz resonant gain. I put this in LSC-DARM FM10, so the freerunning estimate should still be correct. [However, since the DARM filter bank is full, I had to overwrite some other filter. After this test was over, I reverted my changes and placed this RG filter in the LSC-OMC_DC filter bank for safekeeping.]

Red shows the residual after the addition of the 3 Hz resonant gain, as well as a microseism boost, which I put in LSC-OMC_DC. This affects the freerunning estimate, but the amplitude and phase changes at and above 10 Hz are minimal (less than 2 ° of phase change at 10 Hz).

I ran BruCo on one hour of data from last night. The report is available here:

https://ldas-jobs.ligo.caltech.edu/~gabriele.vajente/bruco_1137640217/

At low frequency, SRCL and DHARD_P are the largest contributions. SRCL is still a factor of few below the measured noise, while DHARD is very close around 14 Hz.

There is coherence with magnetometers (still far from the measured noise)

• EY_MAY_EBAY_SEIRACK at many lines below 100 Hz,
• EY_MAG_EBAY_SUSRACK_Z kind of broadband at  high frequency

No significant broadband coherence in the mistery noise region.

A 7.1 earthquake in Alaska at 10:30 UTC tripped many watchdogs. I reset all and went back to nominal working conditions for all seismic isolation at about 17:30 UTC.

Aborting a DTT measurement caused a lockloss - no good, although not a new phenomenon.

Since there are so many SDF diffs, I'm wouldn't put the IFO in Observe anyway, so I'm going to just leave it Down for the night.

Evan, Gabriele

There are too many SDF to accept, so we're just leaving the IFO undisturbed in low noise, starting 3:10 UTC

We noticed a small bump in DARM at about 360 Hz, coherent with PRCL. We added a 270-430 Hz elliptic band-stop. DARM improved and the coherence is almost gone. We are losing 9 degrees of phase at 50 Hz (PRCL UGF).

The filter is implemented in the SUS filter bank.

1220 - 1235 hrs. local -> To and from Y-mid 

Next manual overfill expected Monday, Jan 25th before 4:00 pm

I retuned the MICH feed-forward path. I injected noise in SRCL and measured the transfer function to DARM: TF_SRCL_DARM. Then I injected noise at the feed-forward input, with the FF shaping filters off, but with SBVio1 and SBVio2 on. I measured the transfer function from SRCLFF_IN2 to DARM: TF_SRCLFF_DARM. The optimal feed-forward filter should then be -TF_SRCL_DARM/TF_SRCL_FF. The first plot shows the measurement and the fit. Again, I decided not to fit the sharp features due to the  bounce and roll filters.

I implemented the new filter in the bank 'newFF' and engaged it. The performance improved, as shown by the  reduced coherence. The peak at 3 Hz also reduced a bit. See the second plot: green no feed-forward; blue old feed-forward, red new filter. The last plot compares the old (blue) and new (red) filters. With the new filter, I also switched on an AC coupling (double zero, double pole at 0.1 Hz).

Kiwamu, Sudarshan

ISS Outer Loop Servo Board (S1400214) was modified to include a zero at 100 Hz to obtain a better phase margin. This was done by replacing a resistor R74 from 0 Ohm to 154 Ohm (D1300439) and has been documneted in the E-traveler. 

Initial test has been done after the modification and the board will be installed today during the maintenanace period. Further performance test will be done after the installation and with loop closed.

Inner Loop

ISS Inner Loop has  UGF of 22 KHz with a phase margin of about 50 degress. This was measured with variable gain set at 6 dB for the best phase margin. This is the normal operation settings for Inner Loop.

Outer Loop

Outer Loop has a UGF of 1 KHz ( designed for 4 KHz) with a phase margin of  about 30 degrees. The variable gain was set at 40 dB (max available) and an additional gain stage(?) was switched on as well.

Also tried moving the the Inner loop gain to see if it shows any improvement on the outer loop but no luck.

TF Plots are attached.