Jenne, Lisa, Stefan,

Still running at 40W, for 2h.

Tried to damp some PIs and go to low-noise.

- We successfully damped 15009Hz (ETMY) and 15542Hz (ETMY) (damp settings picture attached.)

- 15541Hz (ETMX) was ringing up.So we tried switching to ETMY and transition the ETMX coil driver to low noise.

- We successfully switch the coil drivers, but...

- We switched to ETMY, low noise, held lock for a while, but saturated the ETMY ESD with 20Hz noise from the ASC, as well as a 532.77Hz line, that we don't know the origin off. (PI?) (picture)

===================================

Also, we realized that DTT is a bit too smart: The 64kHz channel H1:OMC-PI_DCPD_64KHZ_A_DQ can in principle look at PIs above the Nyquest through aliasing. However, since DTT only alows you to select a freqency about 10% below the Nyquist frequency, there is an effecive dead band where DTT cannot see PIs between ~29500Hz and ~36036Hz. The MATLAB script below produces a spectrum up to the Nyquist. Indeed, we found an elevated mode at 30018.3Hz, although it was not quite saturating.

MATLAB code to get spectrum up to Nyquist frequency:

addpath /ligo/svncommon/NbSVN/aligonoisebudget/trunk/Externals/SimulinkNb/Utils/
gwd = GWData();
gwd.make_kerberos_ready;
gwd.site_info(2).port = 31200;
gwd.site_info(2).server = 'nds.ligo-wa.caltech.edu';
H1.channels = {'H1:OMC-PI_DCPD_64KHZ_A_DQ'};
time_fetch = tconvert('26 Jun 2016 01:15:00');
[data, t, ~] = gwd.fetch(time_fetch, 1000, H1.channels);
Fs=4*16384;
pwelch(data,[],[],[],Fs)
 

When I got in a few minutes ago, I noticed that the power into the vacuum had been oscillating for at least as long as our 20 min wall trends.  I'm not totally sure what was going on, but the PSL guardian was following along and adjusting the normalization factor so that the MC stayed locked.  Perhaps TJ can look into this on Monday, but on the PSL guardian screen it said that 38W was requested and the state it was in was the goto_2W, but it looks like the actual rotation stage was going back and forth being requested 25W and 55W. 

Anyhow, it seems like it's back under control now, but we should figure out what caused this so we don't do it too often.  It's probably to do with the fact that Terra was trying to step down the PSL power just before the last lockloss (alog 27963), but still the ISC_LOCK DOWN state or the PSL guardian needs to be able to handle this situation.

Attached is a 6 hour trend showing the situation just before I stopped the oscillation. (Actually, I was going to post a trend with the rotation stage request, and the guardian states for the PSL and ISC lock guardians, but now I can't connect to nds1.  sigh. nds1 is still down, but I can get data from nds0) 

15542 Hz (ETMY) and 15522 Hz (ITMX) are parametrically unstable at 40 W after ~2 hour lock even after ring heater power increase. Only 15521 Hz was successfully damped with ESD actuation.

After a few hours locked at 40 W, the 15.5 kHz mode began to grow for both ETMY and ITMX. I'd watched a few other modes rise and fall during the lock, so I didn't start trying to damp until peaks had grown by over an order of magnitude. I was able to quickly damp 15522 (ITMX) with 2 Hz BP, -60 deg filter, and saturating the drive. 

I was not able to damp 15542 (ETMY). Driving did slow its growth but I couldn't find a damping filter combination that actually damped. I started trying to damp ETMY ~1 min after starting ITMX, so there's a chance I could've caught it earlier, but as you can see below it was also just ringing up faster. I suggest next 40 W lock we turn the damping filter on from the beginning. 

Below I've tracked both frequencies in the OMC DCPDs, showing the PI growth and damping (or failing at damping). I attach a power spectrum showing progression as well. 

When it was clear I wasn't able to damp, I tried stepping the power down 40 --> 38 --> 36 W but the lock broke quickly during this (not directly from the PI); sorry Stefan + Lisa. I'm leaving the interferometer in the DOWN state.  I've edited the new PI wiki accordingly. 

We are seeing 8 peaks in at least two of the horizontal mechanical mode groups (instead of the expected 4, one for each test mass).

Below are spectra of the two mode groups as seen in the OMC DCPDs, taken while locked at 2 W and 20 W. 

Compared to the 15000 vertical mode group here.

When I drove the 15070 Hz group: 

• Driving ETMX with +/- 60 deg phase alternately rings up 15070.5 and 15073.5
• Driving ETMY with same - 60 deg phase and same sign rang up 15072.7 and 15066.6; flipping phase moved 15066.6 peak to right ~1  Hz
• Driving ITMX with opposite signs alternately rings up and damps 15063 and 15077 (alog 27659)

When I drove the 15600 Hz group:

• Driving each test mass with a wide BP over the whole mode group and trying different phases only rang up one peak each
• Driving ETMY rings up 15627.5 but also 15542 just as strongly, even though the latter is supposedly part of an orthogonal mode group 

See wiki for frequencies I was able to drive and thus assign to a specific test mass.

Ideas:

• Mode splitting due to asymmetries in the test masses from ear placement, etc. However, Carl and Slawek both independently failed to see this result when adding asymmetries to their models. 
• Violin mode coupling. However, by these high frequencies violin mode harmonics would cover a wide spread; would they not be just as likely to be seen in any mode group?
• PUM mechanical mode resonances coupling through the violin modes. 

Lisa, Stefan

- We looked  at the DC stability of the transmon: over ~week time scale the TMS drifts by
   ~2 urad in P and Y
   <10u in T and V
- This means that a TMS QPD combination that is tuned for SOFT (instead of insensitive to P/Y) will drift the beam waist around by 4.3mm, or about 1/3 of the beam waist - too big (compare this to the 10u in T and V). We thus need to use the TMS P/Y insensitive QPD reference for long term reference. We can blend to a soft/hard basis at AC if we need it for controling the soft degree of freedom.

- For now we added an IF-statement to the Guardian that allows us easily to switch the input matrix and related offsets.
- We also hard-coded the QPD offests (both Sheila's from today and the ones from 5 days ago).
- Running at 20W, we switched back to the 5 days input matrix and offsets, resulting in a PRgain increase from 30 to 32.

- After that we fine-tweaked the soft loop yaw offsets. We just used the offsets in the control filter banks. We got the best recycling gain with
   H1:ASC-DSOFT_Y_OFFSET = 0.12
   H1:ASC-CSOFT_Y_OFFSET = 0.12
  neither of which are in Guardian yet.
- Finally, we tried closing the SCR1 P and Y loops with the following matrix:
   A36IP -0.5
   B36IP 1.0
   A36IY -1.5
   B36IY 0.26 (changed today - not in guardian yet)
 pitch worked, yaw ran away (see plot). Looks like the signal in A36IY triggered the runaway by flipping its sign.  (B36IY had the right sign)

- We also reduced the OMC_DCPD power setpoint  (i.e. effectively the DARM offset) to 15mA.

- We thus left the SRM open for the night.

I've created a PI Damping wiki to straightforwardly step through the basics of damping PI. It includes a table of mechanical mode frequencies that have actually been seen here (with the corresponding test mass and modal shape), measured Q values, reference spectra at higher power, and a walk through of the PI MEDM screens. 

This page is located in the OPS Wiki, with the PI Damping link right under the violin mode damping link. 

Please feel free to add to it and let me know if I should clarify or add anything. Note that things (such as MEDM screens) are still in development.

1/2 turn open on LLCV bypass valve - took 30 sec. to overfill CP3 to the point that LN2 was flowing out both exhaust lines

Keita, Sheila, Jenne, TJ, Kiwamu,

We had one lockloss today due to an unstable behavior in the 3rd loop. Looking at the data, we figured that this was caused by the dynamic power normalization (H1:PSL-PWR_SCALE_OFFSET) which introduced glitches to the TR signals through the (discretized) normalization. These glitches then propagated to the 1st loop through the 3rd loop and eventually caused the lockloss. This is actually something Jenne and I thought we fixed two days ago by editing the LASER_PWR guardian (not aloged). We checked that the guardian code had been appropriately edited; it seems that the edition has not been effective for some reason. We restarted the node to enforce the edition. So the dynamic normalization should not happen when LASER_PWR reaches the requested stable state. Hopefully this will be the last time to talk about this issue.

The attached shows time series data, showing the glitches by the dynamic normalization.

Shelia Dwyer, Craig Cahillane

We have changed the CSOFT and DSOFT input matrix in an attempt to isolate the CSOFT and DSOFT error signals from one another.

In aLOG 27944, Shelia mentions separating the HARD and SOFT signals in the input matrix.  This aLOG is dedicated to the common and differential mode separation.

To get solely common and differential modes, we must have our X arm and Y arm signals scaled by factors u and v to be of the same order:

CSOFT = u * X_sig + v * Y_sig
DSOFT = u * X_sig - v * Y_sig

We worked on finding u and v by making ~ 1 μ radian alignment changes in the X and Y ITMs and measuring the combination of TRX A and TRX B signals that is insensitive to HARD, according to aLOG 27944. The same was done for the TRY A and TRY B output signals:
Measurements

        X_sig (X Combo)    Y_sig (Y Combo)
Yaw     0.03975           -0.0781
Pitch   0.0302             0.106

We then found and normalized u and v by the same scalar, separated out the TR? A and TR? B components of the HARD insensitive signals, and put them in the input matrix for both Pitch and Yaw:

        u (Yaw X)     v (Yaw Y)     u (Pitch X)   v (Pitch Y) 
TR? A  -0.3521        0.0848        0.9420        0.0201
TR? B   0.8187       -0.4456        0.1936       -0.2733

In the actual input matrices we have flipped every sign in the numbers above in order to have a positive gain in the CSOFT and DSOFT control loop filter banks.

The code that calculates the above matrix lives in

/ligo/home/sheila.dwyer/Alignment/DSOFT/sens_TMS.m

To see if reducing h1fw1's disk loading would make it more stable, Thursday at 11:30PDT we changed h1fw1's daqdrc file to stop it writing science frames on the next daqd restart. Despite h1fw1 having restarted itself six times already Thursday morning, it then went into a period of stability from 09:53 through to 23:15, at which time it restarted and stopped writing science frames. What happened next was interesting, here is the timeline:

Thu 23:15PDT h1fw1 writes last science frame

Thu 23:20PDT h1fw1 restarts daqd

Thu 23:30PDT h1nds1 restarts

Thu 23:39PDT h1nds0 stops working, but its process still exists so monit does not restart it

Fri 05:02PDT h1fw1 restarts, test has failed at this point

The interesting points are: h1nds1 restarted once 10 minutes after the config change. Perhaps not surprising because it uses h1fw1's frames. At 23:39PDT h1nds0 stopped serving data. This is totally surprising, there is no link between h1nds0 and h1fw1 that we know of.

Since Guardian is the sole NDS client for h1nds0, several Guardian nodes reported nds problems while h1nds0 was in its frozen state. DIAG_MAIN for example reported nds failures from Thr 23:40PDT through Fri 10:54PDT.

J. Kissel for the Wind Team

I took the opportunity to grab some pictures of the X-End building exterior and brand new wind fence pathfinder. Winds were roughly 25 mph, so I also grabbed a video. It's too big for the aLOG, so I've posted it to youtube.

Notes on the fence:
- There we no tumbleweeds gathered around the fence
- The material seems to be holding up well (not stressed/stretched too much where it's attached to the fence), and 
- pressing on the back of the material opposite the wind direction it feels like a fully extended sail, but not near any yield point.
- The tops of the posts are rattle a little bit.

The final, as built, design of the fence:
- 3 posts, 24 ft as-purchased; 20 ft is above ground and 4 ft are in concrete in the ground.
- Posts cover 30ft left-to-right, spaced 15 ft apart.
- 6 ft gap between ground and fence material, and material spans the posts left-to-right and is 6 ft tall (so there's room to extend the material upward).
- The material is 30% coverage, or 70% porous. 

Also, 
SEI aLOG 1024 shows the first bit of wind modeling that's being done at Stanford by a summer undergrad Ian Gomez. If you're really cool, you can check out more preliminary results (at this point, just pretty pictures) in the Stanford Engineering Test Facility's eLogBook: ETF eLOG 2593.

My thoughts, after seeing these initial results -- which (rightfully so) start off with a flat bit of ground and a simple box for a building -- that those simple models will get us pretty far for the Y-end where the topography is pretty darn flat. However, the topography is more interesting at the X-end, and my hope would be that by the end of the summer, Ian's models might get just sophisticated enough to predict wind flow around the X-end building. 

You'll recall from the single-PEM-anemometer comparison between X-end and Y-end during wind storms (see LHO aLOG 17574), that Y-end moves about a factor of 2 more than X-end. The topography may have a good bit to do with it.

The plan is to overfill CP4 this afternoon up to 100%, disconnect the flow meter from the exhaust pipe, then time how long it takes to pour LN2 out the exhaust (just like we do for a CP3 overfill), and then reconnect the flow meter, while leaving CP4 in manual mode over the weekend. I will monitor it from home. 

NOTE:  CP4 overfill will generate an alarm

Nergis, Peter, Stefan,

Currently, as we transition from 10W to 57W input power, our recycling gain drops from about 34 to 27. It seems like we need to tune the common TCS:

Attached are 3 plots:

Plot 1: DC signals:

PR_GAIN and normalized arm power (both blue)
AS_DC A and B (green and red)
POP_DC A and B (cyan and purple)
REFL_DC A and B (yellow and black)

Note the interesting behaviour of the REFL DC, all while AS_DC is linear in power.

Plot 2:

Arm and power recycling cavity powers, as well as test mass pitch control signals. The test masses have to compensate for radiation pressure, making the pitch control signal proportional to the arm cavity power.

Plot 3: RF signals:

Power and signal recycling cavity sideband buildups.