As a sanity check we measured the loss on the homodyne path on SQZT6: Loss = 10.7mW/430mW = 2.7% from 4 mirrors + beamsplitter + 3 lenses.

Seed power to homodyne = .430 mW (between measured between periscope mirror1 and periscope mirror2)

.272 mW. and .269 mW on each homodyne diode (seed + LO)
59.5 and 62.2 respectively on each diode (LO only).

Diode 1 seed =  272-59.5 = 212.5 ;   Diode 2 seed =  269-62.2 = 206.8: Total seed power on both diodes = 419.3

Loss = 10.7mW/430mW = 2.5% from 4 mirrors + beamsplitter + 3 lenses.

Note I discovered we currently have no beam dumps before homodyne for parasitic interferometry, this should be addressed but is unlikely to be the cause of our loss issue.

After we closed out HAM6 we took a scan to ensure our alignment were good (alog45372). Our 00 mode was 88.2% then. Today I took another scan and turns out our 00 mode is now down to 78%. That's 10.2% drop. 

I put 20dB attenuator on the 80MHz LO during this measurement so I can compare directly to a scan from out close out log. The attenuator has been taken out.

S. Karki, J. Kissel, R. Savage

After hitting nominal low noise this afternoon, I noticed that PCALY RX PD was not lining up well with CAL-DELTAL_EXTERNAL on the wall FOM -- the PCAL was over estimating it's "meters" by a factor of ~1.4 (we know it was a PCAL flaw because nothing had changed in the DARM loop, nor in the DELTAL_EXTERNAL calibration). 

Rick, Sudarshan, and I quickly found an honest mistake in their implementation of the newly "exploded view" of the calculation of the Newtons / RXPD Volt (implemented yesterday LHO aLOG 46449) -- namely, one component of the calculation, the ratio between the working standard and each EY RX and TX PDs, were flip-flopped (channels H1:CAL-PCALY_FORCE_COEFF_ALPHA_R and H1:CAL-PCALY_FORCE_COEFF_ALPHA_T).

Finding the mistake, they updated the list of EPICs records, (and changed the content of the attachment in LHO aLOG 46449 without changing the name), so I've copied it to Cal repo, so now lives (and committed) here:
    /ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/O3/H1/Results/CALCS_FE/lho_yend_pcal_epics_created-20190116.txt
which has been run, installed, and accepted into both the SAFE.snap and OBSERVE.snap files for h1caley.

We're back in nominal low noise, and the PCAL RX PD lines now line up well with DELTAL_EXTERNAL. Problem fixed.

In LHO:46179 we reported an anomalous phase advance in the DHARD PIT OLTF at ~ 0.8 Hz. 

It turns out that such a feature can be modeled by including cross-couplings in both actuators and sensors. Please see the attached plot. 

In the model we considered the single-arm case which is equivalent and the X and Y arms are balanced. On the other hand, we assumed the ETM has an actuation strength 10% stronger than the ITM, and each soft mode angle we sensed was actually one ideal soft mode minus one ideal hard mode. Without any fine-tuning of the parameters, the model taking into account the cross-couplings almost perfectly matched to the measurement data. 

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

The mathematical details were also attached (actImba.pdf). The basic idea is to project all the quantities with imperfections onto the ideal hard-soft basis (also note that the hard/soft radiation feedback is independent of the strength of actuation magnets), and then extend the regular SISO loop analysis to the MIMO case. The latter is easily achieved by replacing the vector transfer functions into transfer matrices. The effective oltf is then obtained by first finding the close-loop response and then use oltf= 1/cltf - 1. 

NikoL, Dimitri Estevez (Virgo), SudarshanK (remotely), RickS

This morning, we calibrated the Yend Pcal readback channels using the working standard (WSH) that we had delivered to Yend yesterday afternoon and left powered up overnight.

We encountered a couple of software issues related to the updates to calculate the force coefficients in the frontend, but we were able to complete the measurements.

The power sensor coefficients calculated today were very close to the values we calculated from the measurements made on December 13.

We decided to go ahead and switch to using the force coefficients calculated in the frontend (using JeffK's new code).  We updated the epics values using the data from our Dec. 13th measurement and captured in the .txt file attached in that entry.  We "put" the values into the epics records by just copying and pasting the text in the lho_yend_pcal_epics_created-20190115.txt file attached to this entry and in the SVN at

/ligo/svncommon/CalSVN/aligocalibration/trunk/Runs/O3/H1/Results/CALCS_FE/yend_pcal_epics_created-20190115.txt

The new  Pcal power sensor calibration values (N/V) and comparisons with the previous values are:

This last lock, we got to 30W just fine, but lost lock just before nominal low noise, at the CARM gain increase.  Sheila mentions that the increased CARM gain was put into the guardian last night, but that the measurements showing that gain is okay were taken after we'd thermalized.  It's possible that we can't put in the extra CARM gain until we've lost enough 9MHz buildup.

I reverted the CARM gain increase in guardian, and we locked just fine.

We just moved h1guardian1 to new hardware, with more CPU and memory.  The guardian system is being recovered now.

The new machine has 20 hyperthreaded cores (Intel Xeon 2640 V4 2.4GHz) and 128G of RAM.  This is about twice the resources of the old machine.

The old machine was seeing frequent (couple of times a day) EPICS channel connection drop outs, which would cause EZCA connection errors on the guardian nodes and problems locking.  The load on the old machine was very high (>90% load on all 10 CPUs constantly), and the theory was that that was contributing the EPICS connection issues.  We should have considerably more headroom on this new machine, which will hopefully ameliorate the EPICS issues.

htop on the new machine:

TITLE: 01/16 Day Shift: 16:00-00:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Commissioning
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    Wind: 3mph Gusts, 2mph 5min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.38 μm/s
QUICK SUMMARY:

• guardian hardware is bring upgraded, currently down, Richard, Jamie,Carlos working on it
• Vanessa to EY to clean - estimate is 40 minute
• Karen to EX to drop off supplies

Koji, Craig

We had a nine hour lock today.  Koji and I went out on the floor 10:20 UTC in order to measure CARM and IMC OLGs and spectrum, and killed it by the time we had walked around to the PSL racks.  
We were aware of the possibility of lockloss, and took great care to be as nimble as possible, so this is not great, completely prohibitive to in-lock rack work.

In the recent past, we had not been so sensitive to LVEA incursions during full lock.  Not sure what has changed.  All LSC, ASC, and dither loop error signals seem within reasonable range.  IMC_F has a large excursion to -400 kHz directly before lockloss, simultaneous with our excursion.  Most likely possibility in my mind is us walking around disturbed the IMC.  Have there been any changes to HAM2 or 3 isolation?

Craig, Georgia, Danny, Sheila

We have re-tuned the SRCL feedforward for 30 W interferometer configuration. The updated feedforward reduced SRCL coupling to DARM from 60Hz to 500Hz (driven measurement shown in final attachment).

We measured the transfer function from SRCL to DARM without feedforward, and from the SRCL-FF path to DARM, using templates found here:

/opt/rtcds/userapps/release/lsc/h1/scripts/feedforward/

We then used Craig's ipython notebook to fit these transfer functions and calculate the feedforward filtering required to cancel SRCL noise in DARM. The notebook is found here:

/ligo/home/craig.cahillane/Git/Feedforward/SRCL2DARMfeedforward.ipynb

This notebook uses iirrational to fit the transfer functions. We added some human tweaking to the fit to minimise the resonant peak at ~8Hz. First attachment shows the data (blue), iirrational's fit (orange), and the human-modified fit that was implemented in the feedforward filter (green). Note that the fit to the phase of the TF is not good below 60 Hz, so perhaps there is room for iterative improvement on these filters.

The second attachment shows the old SRCL-FF filter (Nov7) compared to our new filter (Jan15).

The final attachment shows the SRCL to DARM coupling reduction: yellow is DARM (and SRCL) with no excitation, blue is with the old feedforward, purple is the new feedforward.

Georgia, Koji, Jeff K, Sheila

We made a couple of small updates to the OMC_LOCK guardian and omcparams:

TUNE_OFFSETS state

We had a lockloss straight after transitioning to DC readout. Looking back at the guardian log (first attachment) we see that in the TUNE_OFFSETS state, where the guardian measures RF DARM to OMC transfer function and sets some gains to match them, the transfer function failed and some channels are set to nan. I'm not sure yet what IFO conditions created this condition, but we added an error flag to the TUNE_OFFSETS state to prevent the OMC from proceeding to READY_FOR_HANDOFF if the TF fails.

FIND_CARRIER

The OMC guardian has been having trouble finding the carrier on its own in the last ~week. In FIND_CARRIER it sweeps PZT2 and looks at the DCPD's, first finding the two 45 MHz sidebands and then searching for the carrier halfway between them. The current offset on PZT2 for the carrier resonance is ~77V, and the scan sweeps from 20-80V, it looks like in our current sweep range we only see one 45 MHz sideband and the carrier. The second attached photo shows the data for two sweeps, third is zoomed into one sweep. I will reduce the starting PZT offset in omcparams so that we  sweep through both 45 MHz sidebands on the lower (~28V) carrier resonance, given past issues with 9MHz higher order modes resonant at large PZT offsets.

Sheila, TVo, Georgia, Craig, Danny

• Last night as well as today we saw that there is a slow (~60 second period) oscillation of PRC1Y (AC coupled QPD to PRM), which seems to be fighting the dither loop.  We tried to turn off the PRC1Y twice, leaving the dither loop on, and both times an instability rang up in CSOFT P at 0.5 Hz.  Tonight we reduced the gain of CSOFT P by 20dB, and the oscillation went away. We were then able to turn off PRC1Y, and the low frequency oscillation is also gone. 
• Georgia added 10dB of gain to the YAW3 dither loop (which is for PRM), which she is putting in the guardian. 
• TVo and I saw that the X QPD combination used for the CSOFT P loop wasn't orthogonal to the CHARD combo, which we think it should be.  We put the matrix that is orthogonal to CHARD in CSOFT P A, and switched to that (0.111 for XA, 0.159 for XB, and 0.039 for Y B).  We increased the CSOFT P gain, and saw something ring up at 0.5 Hz again. 
• We sat with the CSOFT P gain low for about a half hour again, before something rang up at 0.5 Hz again, most visible in CHARD Y.  We increased the gain of CHARD Y by a factor of 2, and this made the oscillation go away.  With the CHARD Y gain increased, we could again increase the CSOFT P gain back to normal without anything ringing up. 

This current ASC situation seems better than what we've had the last several days, so we probably want to make some of these changes permanent, but we don't want to make any changes in the guardian since ASC engagement has been tricky and we may not have a chance to test things. I think that turning off PRC1Y, and increasing the CHARDY gain from 3 to 6 are definitely improvements.  The change to the CSOFT input matrix I'm not so sure about. 

Summary: BRUCO gave us a few interesting clues about our current noise, including a broadband contribution to the DARM noise that seems to couple through the 9 MHz sideband. 

We had 20 minutes of glitch free data from 1231532246 to 1231533411.  This was before Georgia and Danny fixed the ISS second loop clipping 46412, which improved the noise from 27-15 Hz and around 350-400 Hz. Gabriele and Joe Areda managed to run BRUCO (and update the code to deal with some other updates), a report is here: https://ldas-jobs.ligo.caltech.edu/~gabriele.vajente/bruco_lho_1231532246/

Some interesting features (other than the ISS coherence)

• The peak at 90 Hz which has appeared in our spectrum since December has coherence with accelerometers and ISI sensors around HAM5. This is where PEM injections on the HAM5/6 chamber walls showed some noise that was well below DARM in the past, so we can try exciting those ISIs, or the OFI to see if that has gotten worse. 
  • Some templates used in the past for shaking HAM5 are in /ligo/home/sheila.dwyer/noise_budget/simple-noise-budget/restructured_nb/input/ISI
• The broad coherence of the OMC QPD sums with DARM (OMC QPD A sum).  Some of this is just the intensity noise that is also witnessed by the ISS second loop out of loop sensors (PD7)  The attached screenshot shows a comparison of this coherence before and after the ISS fix, as you would expect the ISS fix reduces the coherence at the frequencies where the ISS noise was reduced, but the broad coherence is unchanged.  The legend in this screenshot is wrong, the gold DARM spectrum is not a 92 Mpc reference.  We aren't sure of our calibration at the moment. 
  • We increased the modulation depth for 45 MHz by 3dB from 5:29 UTC to 6:28 UTC on Jan 16th.  There were many loud glitches in this period, but there is a quiet time that starts at 5:47, the coherence of the OMC QPD with DARM was unchanged at this time.  So this noise isn't coupling through the 45 MHz sidebands.
  • We increased the 9MHz modulation depth by 3 dB from 6:40 UTC to 7 UTC, and the coherence increased, roughly scaling with the sideband power.  (Our range also dropped by about 10 Mpc) Koji reminds us that we've seen a 9 MHz higher order mode in the OMC camera before: 29395  We can't see much in the camera tonight, if we increase the exposure we saturate the camera to the edge of the screen, so if we want to recreate Jenne's images we probably need to go to the new camera housing and move the camera or add a lens.  
  • We could add more whitening to these QPDs, and will plan to do that next time we are unlocked. 
• We hadn't redone the SRCL FF since the increase in power and changes to TCS, so this showed up in BRUCO.  Georgia, Craig and Danny have improved the feedforward above 60 Hz (separate alog).  

I ran the IMC a2l script, and some gains changed so much that I was not confident that they were correct, because the IMC optics OSEM values had not changed more than 5urad, so no large gain changes were expected.  I started another measurement, but it did not finish, so the current gains are ok enough, but could be updated tonight when there's a lock loss, or in the morning I'll revisit.

During the several hour lock over night, that I found the IFO in this morning there were some strange combs in the CARM signals. 

The particularly strange thing is that I see these spikes in the LSC-MCL signals for that lock first thing this morning, but haven't really seen them in any later locks today.  During the lock that the spikes are there, there are a few times that the spikes go away for 2-4 sec, but they always came back.  In the next lock, the spikes were almost never there, but did come in 2 or 3 times for 1-2 sec, but then went away again.  Between these 2 locks, I'm not aware that any configuration changes were made to the CARM system.

The SR785 was plugged in to the IFO common mode board, and the excitation input was enabled, so it's possible that the SR785 and whatever mysterious grounding problems we've been having are the culprit.  But, since the SR785 wasn't unplugged until much later in the day, I'm not so sure.  Anyhow, we're going to try to make a habit of unplugging any instruments from the ISC racks as soon as a measurement is complete, just in case.

It looks to me like there are 2 different combs, both very near 232 Hz, but they are drifting in time relative to one another.  See attached DARM spectrum with the giant comb, as well as ndscope screenshots from 2 different times during the same lock.  The ndscope screenshots also show that the IFO is in the same state (NomLowNoise) for both of these times.  No gain sliders in the common mode or IMC servo boards were being moved either.

SudarshanK, RickS

We completed calibration of the Pcal power sensors at EndY today using the new Working Standard (WSH). This calibration also incorporates the changes we made to the Pcal Tx and Rx  power sensors on Tuesday (LHO  alog 45876). The results of this set of endstation calibration measurements can be found in the attached text file.

All the data, plots and the intermediate results from this calibration measurement can be found at https://svn.ligo.caltech.edu/svn/aligocalibration/trunk/Projects/PhotonCalibrator/measurements/LHO_EndY/D20181213/

Using these measurements plus the Working Standard to Gold Standard responsivity measurements, new Gold Standard measurement from NIST (-8.0985 V/W) and the in-vacuum optical efficiency measurements we did during the vent, the force coefficients for the Pcal TxPD and RxPD in N/V are:

TxPD : 1.5049E-09 N/V

RxPD: 1.0223E-09 N/V

The previous values used during O2 and still implemented in the filter files are: 

TxPD : 1.5160e-09 N/V

RxPD: 1.0475E-09 N/V

They differ from these new values by about 0.7 and 2.4%, respectively.

We are not going to update the calibration at this time. We will wait until the next long lock opportunity to test the new values by comparing with X-End Pcal.

The parameter file that is required to generate the force coefficient in the front model is attached as well. Note: We have left the TX and RX (AA) gain factor as 1.