08:08 IFO fully locked @ ~ 18Mpc  (according to SensMon).

Evan, Sheila, Dan, Kiwamu, Lisa 

SUMMARY 

The wind dropped below 20 mph in the evening, and we started locking. After some roll, bounce and violin damping, we made it to DC readout @ 8W. We successfully transitioned DARM to ETMY with low noise ESD and got some MICH feed-forward cancellation going. We improved the noise between 30-200 Hz, and reached  28 Mpc  (according to SensMon). 

The noise was more stationary than  previously observed . 

However,  the OMC is still shaking , and it is not good. Dan has a resonant gain for DARM ready to be tested to reduce the noise around 3 Hz, but we didn't manage to get that done tonight. 

We leave the interferometer locked at 28 Mpc starting at March 24, 2015 9:17 UTC . 


DARM control on ETMY with low noise ESD  

We did the transition from ETMX to ETMY L2 for DARM, but the interferometer was very glitchy, and we decided to abandon L2 control and try the new  Den's strategy  to do the feed-forward to ITM(Y) L2. 
Evan got about a factor of 10 subtraction (FM9 has BS plant inversion in LSC-MICHFF filter bank, gain +0.048). 

ASC cut-off filters 

Since none of the ASC loops had cut-offs, we decided to add  some . They are now engaged by the Guardian. A more fine tuning will happen at some point. 

Started switching coil driver to low noise  

We started switching the coil driver to  low noise . Evan will post a table later with the successful switches we did after acquiring the DRMI lock. We need to do more work on this, some failed.

Lisa, Dan, Sheila, Evan, Kiwamu

We checked the evolution of the flickers in OMC TRANS over time.  It appears that the features between 1-5Hz have always been there, but the amplitude has grown by a factor of ~3-6 in the past two weeks.

In the attached plot, the ampltiude of the 3Hz peak on Mar 6 was about 0.004 / rt[Hz], and today it is 0.02 / rt[Hz].

We've added rolloffs to the ASC loops, turned on the 'resg1' filter in the ETMY_M0_DAMP_L filter bank (this adds a RG at 1Hz and an overall gain of +6dB), and looked accusingly at the OMC TRANS camera image.  No change so far.  Next idea is to try a boost in the DARM loop gain at low frequency.

Lisa, Evan, Sheila, Keita, Jim W, Kiwamu,

Today we had an issue in which the Y end PDH loop kept unlocking due to a high longitudinal motion (more than 12 um peak-to-peak at 50 mHz). The wind was high at 20 mph on average with 40 mph at highest most of the time today starting from 9 am local. In this report I attempt to summarize the issue associated with today's windy condition.

(Y arm motion was too high)

When we started fully locking the interferometer, we noticed that the ALS loops frequently dropped their locks in the middle of the locking sequence. It turned out that the Y arm motion was so high the end VCO saturated in every several minutes. The X PDH also had a similar amplitude but it was slightly smaller than that of the Y arm by ~ 20% which barely allowed the X arm to stay locked. The attached is a 5 minutes trend of relevant channels under a condition that:

• without ALS diff loop.
• without ALS comm loop.
• with local tidal feedback loops on X and Y arms with UGF of about 0.03 Hz for both loops.
• ISI ETMX stage 1 is in 90 mHz blend configuration without the BRS correction
• ISI ETMY stage 1 is in 90 mHz blend configuration.

As shown in the plots, the Y arm PDH control signal (ALS-Y_REFL_CTRL_OUT_DQ) went up and down at a frequency of 50 mHz. This channel is calibrated into the Y arm displacement in um. When it went below -7 um or above 7 um it unlocks essentially because the end VCO rails. The X arm showed a similar amplitude, but amplitude was not as big as that of the Y arm. The X arm dropped the lock less frequently than the Y arm.

(Some attempt with a high band width tidal)

We then started increasing the bandwidth of the local tidal feedback which picks up signals from the end PDH control and offload it to the L1 stage of ETMY. The idea is that we wanted to physically quiet down the ETMY motion so that the VCO can stay within the range. We increased the gain of both X and Y local tidal loops by a factor of 3. So their UGFs are now 0.1 Hz.  At the end the attempts, the wind incidentally came back down to 10-30 mph so we can not really say if this scheme helped.

I added a new Guardian node to the overview screen today (screenshot attached). SYS_DIAG will run different tests to check for particular conditions. If a test finds a problem it will bring up a notification. Just like other Guardian nodes, opening the main screen will allow you to click on all notifications and see the entire list, otherwise it will cycle through them in the space provided on the mini.

I will still be tweeking little things here or there, but it is definitely usable/useful now.

The tests that it currently runs are :

• ALS_SHG_SERVO: Checks to see if the ASL SHG Temp Control Servo is ON
• BRS_DAMP: Check if the BRS Damping turntable is on and working
• BRS_DEAD: Checks if the BRS is software dead or needs to be rebooted
• SEI_STATE: Checks is the SEI systems are in their nominal configurations
• TCS_LASER: Checks the TCS laser output (only TCSX for the moment)
• BLRMS_MATRIX: Checks if the BLRMS matrices are mostly green
• COIL_DRIVER: Checks that coil drivers have not gone down
• SUS_OUT_OF_RANGE: Like the Drift Monitor, if a suspension stays too far it will notify
• PEM_CHANGE: For now it is only looking at major earthquakes (VEA temps, high winds in the future)
• MC_WFS: Checks the MC WFS are engaged
• OL_SUMS: Check OpLev sums are low when suspensions are aligned
• SW_WD: If a software WatchDog is tripped....we will know
• Bounce/Roll/Violin_Modes: Checks if the quad modes have rung up (thresholds need some works still)
• PSL_Noise_Eater: Check that the Noise Eater is engaged
• DAC_CTRL_SIGNALS: Checks that the SUS and SEI are sending out control signals (not running yet)

When you select the requested state to INIT the log will list out the tests that it is currently running.

If there are other tests that you would like to see on here please let me know!

Scott L. Ed P. Chris S.

61 meters cleaned towards single door between X-1-6 and X-1-7.
Continuous monitoring of beam tube pressures by control room operator during cleaning operations.

Bubba John W.

All of the axial fans are lubricated.
Corner station SF 4 has at least 1 bearing that needs to be replaced and is currently off line awaiting parts. We will monitor the LVEA temperatures very closely but this should not have any adverse affect on the temperatures. 
End X SF 2 also has a bearing that is suspect. This fan is off also. 

07:00 Cris and Karen into the LVEA

08:25 RMS wathcdogs tripped on ETMs. ETMY reset from medm reset. ETMX still showing a trip on L2 UL.

08:53 RMS trip on L2 ETMX cleared by power cycle

09:35 ISS diff power was up to 10% +. I adjusted the refsignal to (-)2.07 for a net diffracte power of ~7%.

10:07 R McCarthy back from installin ESD filter at EY

10:16 Bubba to start greasing fans at mid stations. (MidX first)

10:45 Jim switched end stations from 45MHz ISI filter blendsto 90MHz filter blends due to the SSW winds exceeding 35-40 mph.

11:21 Jodi to MidY

11:34 Bubba movning to mid Y 

12:02 Very windy day today. Sustained winds at ~26mph with gusts exceeding 40 at times

12:15 D Barker and J Batch to EX (non VEA)

12:55 Bubba and John to EX to grease fans

13:27 D Barker and J Batch to EY (non VEA) to address TCT (timing) problem.

13:46 Bubba and John to EY to grease fans

14:30 Calum and Kate on site

14:35 Bubba and John back from Ends. 

16:00 Bubba done with fans.

This message tests the automagic emailling of the detchar@ligo.org list when the 'DetChar' task is used on a post.

Again following un on Kiwamu's report, I took a look at the non stationarity of the noise during the low noise lock.

In brief, the largest contribution to noise in the 50-200 Hz region comes from MICH/SRCL, and it'slargely modulated by angular motions, mainly ETMs and (maybe) PRM.

Some more details follow. The first plot shows a spectrogram, with a quite clear almost periodic fluctuation of the noise. As usual, I computed the BLRMS in the 100-200 Hz region, to obtain the second plot. In the same plot I show the reconstructed BLRMS using local witness sensors of all main mirrors. The reconstruction is resonably good, and the channel ranking (figure 3) seems to indicate that PRM and ETMY are the most important contributors to the noise non stationarity.

A much better reconstruction of the BLRMS time variation can be obtained using the WFS and QPD angular signals, as shown in figure 4 and 5. The BLRMS is almost perfectly reconstructed. The channel ranking shows that AS_B_RF45_Q is the largest contribution, which seems to confirm that DHARD is important. The strange thing is that I can't see any signal here to indicate that PRM is important.

The last three figures show a "coherogram" (not sure if this word really exists) of DARM with auxiliary d.o.f.s output. Those plots show the coherence as a function of both frequency and time, similarly to what a spectrogram does. Clearly, the fluctuating noise is due mainly to SRCL noise, with a coupling coefficient strongly modulated by the angular fluctuations.

Following up on Kiwamu's report, here is the summary page for the coherences during the low noise lock:

https://ldas-jobs.ligo.caltech.edu/~gabriele.vajente/bruco_1110961816/

As usual, here is my digest.

In brief: we need MICH/SRCL subtraction, check SRC angular controls, they might be injecting noise, better tune the IMC longitudinal offset if possible

More details:

• At low frequency, below 5 Hz, the most prominent coherence with with SUS-ETMY_M0_DAMP_L_IN1. However, I'm not sure about the origin of this signal, so it might well be that it's just a DARM control signal fed to the top stage.
• Below about 100 Hz and especially below 30 Hz there is a significant coherence with SRC angular signals, in particular: SUS-SR2_M3_LOCK_Y_IN1 and SUS-SRM_M3_LOCK_Y_IN1. My guess is that the SR2 and SRM control signals are very similar, after the implementation of the driving diagonalization 
• MICH is likely the dominant source of noise in the 20-100 Hz region. SRCL is showing large coherence up to 200-300 Hz.
• We still see coherence of SRCL and PRCL signals (and REFL/POP signals) at high frequency, up to kHzs. This is likely due to the IMC longitudinal offset. It seems to me that the situation is slightly better now.
• Coherence is high with IMC angular signals at the 200-400 Hz peaks
• At about 450-500 Hz there is a lot of coherence with ITMX_L2 signals, which I guess is due to the violin mode damping. It might be worth checking if this is re-injecting any noise
• Coherence with intensity noise is not very high, but neither very low. In particular there seems to be a line at 1080 Hz.

P.S. Why are you sending DARM signal into the CARM filter bank?

Commissioners were complaining of excess arm motion, so I've changed the blends on the beamline directions on St1, from the nominal 45mhz blends to 90mhz. To review for those not in the seismic know, this is done by opening the St1 Blend screen from the BSC ISI overview and clicking on the 90mhz blend in the appropriate direction (i.e. X for ETMX, Y for ETMY). Attached screens show overview with circled blend screen, St1 Blend overview, close up the blend X bank. It's not perfectly clear that we need to be using the 45mhz blend or if the 90mhz blend is good enough, but I've been talking to some of the commissioner about maybe doing an assessment when it's convenient.

TJ asked me about the BRS this morning, as it was tripping an alarm he had set. When I opened the overview, the numbers were rather large and swinging rapidly (over a minute it was going from -40000 cts to +40000 cts, the transition was a couple seconds. The attached dataviewer trend shows it has bee doing this since the 21st, starting about 15:00 UTC. No clue what happened.

Dan, Kiwamu,

At one point last night, we noticed that a roll mode rang up at ~14 Hz. The peak height in the DARM spectrum (ffted with a 0.1 Hz BW) exhibited a anomalously high value of more than 10^-12 m/sqrt Hz.

So we worked on damping the peak, this time with the AS_WFS_A_45Q signal (alog 16864) which is a state-of-the-art Livingston technique. We were successfully able to damp the mode to an ordinary height of about 10^-14 m/sqrt Hz level in the DARM spectrum.

(Identification process)

First of all, see how terrible the roll mode was:

The red curve is from Mar-17-2015 8:51:00 UTC and we were intentionally stayed on the rf DARM rather than the DC readout to combat the roll mode. Even though there was some confusion in identifying which suspension had been rang up, eventually we confirmed that the roll mode was from ITMX by taking coherence between AS_WFS_A_45Q and the OPLEV_PIT signal of each test mass. In fact, the ITMX oplev was able to see the roll mode in its spectrum with a peak ~ 10 times higher than the noise floor while the rest of the oplevs did not see a visible peak.

In addition, after the successful damping on ITMX, the AS_WFS_A still showed a bit high peak but with a slightly lower frequency (~ 200 mHz ) than that of ITMX. We then identified that this was in turn from ETMY by looking at the coherence again. This lead us to another damping work on ETMY which we were also able to damp.

(Damping setup)

The AS WFS_A signal was routed from the ASC model with a gain of +1 (in ASC_OUTMATRIX_TESTMASS_DAMP). I found that both were damped well with a positive gain in SUS-E(I)TMX(Y)_M0_DAMP_R.

As for ITMX, I ended up with FM3 (-100 dB), FM4 (bp13.9) and a gain of +40. Although I had to start from a gain of +1 in order not to saturate the DAC due ot the high amplitude in the roll mode. Then I gradually increased the gain as the DAC counts reduced. Once I went to a gain of more than 10, the mode was damped relatively quickly probably on a time scale of about a couple of minutes.

As for ETMY, I ended up with FM4 (bp13.9) and a gain of +0.0008. At one point I went to a gain of +0.005, but this actually started increasing the peak height. So I had to set the gain back to + 0.0008. This loop could damp out the mode on a time scale of a couple minutes as well.

(Why they rang up ?)

We don't know.  One observation is that before the modes rang up, Sheila was trying to increase the recycling gain by manually touching the ITMs.