I took a look at the integrated DARM 0-2000 Hz spectrum from 50 hours of 30-minute FScans SFTs taken
over the last few days. A couple of sample plots are shown below, and a more extensive set of plots is
attached in a zip file. The alphabetic labels on narrow lines conform to those defined in this earlier pre-ER7 report.

Highlights and lowlights:
* The 0.1698-Hz comb seen before is gone.
* The 3.9994-Hz comb seen before is gone. 
* The 36.9725-Hz comb seen before is gone.
* The 16-Hz comb seen in ER7 is still prevalent throughout the spectrum. The 64-Hz harmonics are no longer marked separately, since they don't seem as special as they once did.
* There is a new 1-Hz comb with a 0.5-Hz offset, that becomes visible at about 16.5 Hz and peters out around 69.5 Hz (for this integration time). This comb seems likely connected to there being strong digital lines at 0.5 Hz and 1 Hz.

There are some new single lines marked here and there (with 'x'), plus some new calibration lines. I have not removed singles marked previously, in case they reappear with deeper integrations to be done after more ER8 data is available.

Figure 1 - 0-2000 Hz
Figure 2 - 20-100 Hz (note the new 1-Hz comb marked with 'O' for 'One'

Since LLO had been down in this afternoon, I took this oportunity to renew the dtt templates that are for measuring the transfer function of each stage of ETMY. I tuned the envelop parameters while the interferometer was locked at 23 W in the NOMINAL_LOW_NOISE state. The attached are the resultant templates. The frequency range is newly adjusted to [10 200] Hz with 21 frequency data points as planned. Each one takes several minutes to complete the measurement. According to the results I got, we can get a quite good coherence for all the relevant stages (i.e. L1, L2 and L3 stages) at all the frequency points with a coherence of more than 0.99. On the other hand, the template for measuring the DARM closed loop in this particular frequency band may need a bit more tuning because the coherence was not as great as the ones for the ETMY transfer functions.

Daniel, Dan, Evan

Summary

We took another measurement of 45 MHz oscillator frequency noise into DARM.

The conclusions are as follows: (1) like the previous measurement, the transfer function is flat in terms of frequency noise coupling into DCPD current, but (2) the coupling is about 7×10⁻⁷ mA/Hz, which is 5 to 6 times lower than the previous measurement. Assuming a flat 45 MHz phase noise of 4×10⁻⁷ rad/Hz^1/2, we expect a contribution in the DCPD sum that is 3×10⁻¹⁰ Hz/Hz^1/2 and rising like f, which is not enough to explain the excess we see (and isn't the right shape).

In the previous measurement, we had some trouble with the calibration (namely, the voltage-to-frequency coefficient on the IFR front panel didn't match what we measured with a mixer), and also we were shaking the 9 MHz and 45 MHz sideband phases simultaneously. So I am more inclined to believe this measurement.

Details

1. First we wanted to measure the relative delay of the 9 MHz and 45 MHz sidebands using the nominal (OCXO/HG) configuration, so that we could preserve this phase when switching to the IFR. On a scope we saw that the crest of the 45 MHz lagged behind the 9 MHz crest by 12.8(4) ns. [Of course, this is cable-length dependent and has no absolute meaning.]
2. Then we set up a PLL as shown in the attached diagram. We lock an IFR to the 45 MHz output of the HG and use this output to generate the 45 MHz signals for the interferometer. This PLL has a ugf of 46 kHz or so. By 7 kHz it has 20+ dB of loop suppression, so for the rest of this analysis we don't correct for the loop gain.
3. We calibrated the PLL drive by tuning the error point offset knob on the LB1005 and watching the relative delay between the 45 MHz drives of the IFR and the HG. From this, we measured that the calibration at the error point is 45 mV/ns, which is 0.16 V/rad.
4. Then using the same cable lengths as in the first step, we looked at the of the 9 MHz (from the OCXO) and the 45 MHz (from the IFR) on a scope and tuned the error point offset to give an identical delay as before.
5. Then we hooked up the spare LSC DAC channel to the unused ("B") error-point input of the LB1005. The SFM for this channel is calibrated so that the excitation is in volts. We verified this in the CER with a scope. [The calibration uses FM1, which is a flat gain of 3276.8 ct/ct, along with a factor of 2 in the SFM gain. We're not sure why we need this factor of 2 to get the right calibration, since we think the calibration should be 2¹⁶ ct / 20 V = 3276.8 ct/V.]
6. Then we relocked the interferometer and measured the transfer function from the LSC DAC channel into the DCPD sum.

The attachments show the calibrated transfer function (both in terms of phase noise and frequency noise).

Locked about 5 hours into day shift - a continuation from owl shift.

LLO down and commissioners arrive, so went to commissioning mode.

Excitation broke the lock.

IFO relocked with only a tweak to the BS alignment for DRMI.

Commissioning continues, but this lock does not have an extra stage of whitening on the OMC - see note below.

--- 

OMC_Lock has a new stage ADD_WHITENING

This is added after the IFO reaches Nominal_Low_Noise, BUT

H1:OMC-DCPD_A_IN1 and H1:OMC-DCPD_B_IN1 need to be less than 3000 counts peak to peak, or adding the extra whitening will saturate... and bad will happen like lock loss or increased noise

Commissioners arrived and LLO is down, so took IFO out of Observing/Undisturbed Mode for commissioning work.

IFO has been in lock 10+ hours.

H1 has been locked for 10 hours as of 20:00 UTC with a steady range of a bit more than 60.  The detector has experienced one or two momentary disruptions per hour over the last seven hours.  Since 17:00 when I arrived, the voice inside has indicated ETMY when these have occurred.  Cheryl had initiated an oplev strip tool earlier this morning; the H1:SUS-ETMY_L3_OPLEV_SUM_OUTPUT trace has moved higher throughout the last couple of hours.  SDF:  OMC Table (5) and Calcs Table (29) are red.  Vacuum:  Several LX and LY ion pump status readouts are linking red. And CP-1 is reading 23.  Dust:  EX dust is alarming white.

8/22 OWL Shift:  7:00-15:00UTC (00:00-8:00PDT), all times posted in UTC

Arrived to Commissioning on a locked H1, and L1 down for last 12+hrs.  Environemental conditions were nominal with wind dipping below 20mph & all seismic bands also quiet.

Want to reiterate that for ER8, we are deeming 1pm - 10pm (with L1 down) as the Commissioning window.  And I'd say if you need a measurement done during the 1-10pm window and H1 is locked, break lock in H1 and do your measurement if L1 is already down.

Additionally, before Evan, Dan, Stefan left, I made sure to have them clean up any differences on SDF.  Most were cleared up except for the OMC. 

After the Commissioning work, H1 has been locked the rest of the shift with nice range ~65Mpc & a few ETMy glitches dropping range.  DARM looks nice.  At times we seem to run below the reference from 10-20Hz.  There is also a bump at about 330Hz which is above reference.  H1 was much less glitchy for this OWL shift vs yesterday.

Shift Activities:

• 7:30 Dan & Evan out to LVEA for PLL set-up
• 8:30 Dan/Evan back.  Mentioned noise around HAM4 (transformer making noise and something else also making noise)
• 9:27 EY Dust monitor started alarming (not surprising with smoke in the air) with high counts for most of the shift on the order of tens of thousands of counts.
• 10:20 On CDS Overview noticed a CFC bit for H1OMC (due to Evan).  Load Coefficients was run to clear this.
• 10:25 With Violin Modes low, Added Whitening to the OMC (via OMC_LOCK guardian)
• 10:31  Went to Observing Mode
• 12:06, 12:38, 13:00, 13:55, 14:42 ETMy saturation
• 13:00 Gave a call to LLO to check on their status (because here they looked like they had good range, but on the GWI.stat page, their status is listed as "NOT OK".  Traced issue to their ODC Observation Ready bit (operator buttons were marked for:  Undisturbed & Observing)--  It was RED.  We then tracked this down to possibly a PSL excitation.  Gary was able to kill the excitation test point and they are now back to GREEN (i.e. OK + Intent).
• Handing off to Cheryl on this smoky morning.

SUMMARY:  Arrived to an H1 locked and in Commissioning, and L1 down for last 12+hrs.  There was some commissioning work and then H1 was taken to Observing Mode at 65Mpc.  Environemental conditions were nominal with wind dipping below 20mph & all seismic bands also quiet.

Commissioning Activity

Had a discussion about WP5442 with commissioners and since L1 was down and there was a measurement which needed to be done before O1, gave them a few hours to run a PLL measurement (they had it from roughly 7-10UTC).

H1 Back To Observing

Once they were done and H1 was back up to Low Noise, a roll mode was noticed aroudn ~41Hz (Dan/Evan mentioned it's a triple).  It rung down after about 10min, but it was huge at the onset.

While checking items before going to Observing Mode, noticed a CFC bit for H1OMC on the CDS Overview.  This was due to Evan & a diagnostic for LSC CARM (which we don't use).  I hit Load Coefficients to clear this bit.

At this point we were hovering at about 55Mpc.  Since we had low violin modes, transitioned from READY_FOR_HANDOFF to  ADD_WHITENING on the OMC_LOCK guardian (and then went right back to READY_FOR_HANDOFF).  This took the range up to 65Mpc. 

The range then went to a cool 65Mpc and the DARM spectrum looked very nice (compared to the previous night)--spectrum was very close/better than the reference.

SDF Overview had some DIFFERENCES, but Evan/Dan cleared most of them.  The only differences left were for:

OMC (5 diffs)

• slider one state at lock acquisition & another value at low noise....should we Not Monitor?
• offsets:  these will change quite a bit.  Not monitor?

CALCS (29 diffs)

• Long list as mentioned earlier

We ran dither lines for BS and SRM during the power increase, as well as during the 45MHz EOM modulation depth reduction:

Lines:
H1:SUS-SRM_M3_ISCINF_P_EXC 7.0Hz, 300cts
H1:SUS-SRM_M3_ISCINF_Y_EXC 7.5Hz, 900cts
H1:SUS-BS_M3_ISCINF_P_EXC  8.0Hz, 100cts
H1:SUS-BS_M3_ISCINF_Y_EXC  8.5Hz,  30cts

Lines started by        2015/08/22 06:23 UTC
Start PWR UP:           2015/08/22 06:24 UTC
Stop PWR UP:            2015/08/22 06:26 UTC
Start EOM MOD:          2015/08/22 07:02 UTC
Stop  EOM MOD (-4dB):   2015/08/22 07:11 UTC
Lock loss:              2015/08/22 07:15 UTC

The EOM reduction reached -3dB, and was lost due to a SRC1_Y run-away.

Attached are (all plots have 72 min span, halting just before lockloss):
- Plot 1: AS RF36 PIT and YAW signals, plus the ASAIR_A_LF_OUTPUT for reference, showing i) power increase, ii)  beam diverter closing, and reopening, iii) modulation index reduction.
= Plot 2: All quadrants of the AS36 WFS, on the same scale
More details later.

Mostly quiet night, first couple of hours were hindered by winds maxing out at ~40mph. Once the max got down to ~35 we were able to lock. Winds have been slowly declining since.

~1:00 UTC Dan discovered an OMC PZT was tripped. See alog 20767.

Most of the rest of the night has been noise hunting.

~6:55 UTC, I went on the roof to look for grass fires as the front of the OSB smelled like smoke, and the cameras were too grainy to see anything. Commissioning crew reported no clear effect on IFO, but there was a series of saturations on ETMY.

Jenne, Dan, control room people

Attached are some additional plots of the glitches that Sheila posted about earlier today.  These are the same 'DRMI' glitches which we observed back in ER7 -- or, at least, they are similar enough that I can't tell the difference. 

In our most recent lock stretches, started around 0400 UTC, the glitches have gone away.  The mystery continues.

The excess noise is loudest in POP_A_RF9_I_ERR, which is what we use for PRCL in low noise.  We also see noise in POPA_45_I_ERR (used for SRCL), and not so much in the Q-phases.  See the first plot.  So, they're not an issue with the PD or the demod electronics.  It seems like real length noise, except the noise is very flat.  It's hard to imagine a glitchy actuator making flat noise in the PRC and SRC lengths.

FWIW the noise is also visible in POPAIR, with the same pattern as POPA.  We also see the excess noise in REFLA_45_I and Q (second plot).

Since these glitches appeared in ER7 we have implemented the offloading of the PRM and SRM M3 stages, so the drives to the last stage are mostly around zero.  We looked for any correlation with zero-crossings in the SRM and PRM M3 coils (third and fourth plots).  No smoking gun.

We were locked most of the day until ~21:00, out of lock for around an hour, and came back up relatively easily ~22:00.  Another successful PRMI-->DRMI transition trick seemed to help expedite the process. 

Although I failed to note specific times, Kyle and Gerardo were working at Y-2-8 most of the day, and Jodi visited the mid stations for property tagging work.  Neither of these seemed to effect the IFO performance noticably.

Winds have been in the 20-30mph range for the past 4 hours, with a few gusts to ~40mph.

Sudarshan reports that a PCal line was turned off sometime last night.  He is turning it back on at 17:53.

Using the calibrated DRMI channels created and described by Kiwamu in entry 18742, I grabbed data from the lock of August 3, 2015, starting at 04:20:00 UTC. The attached 4 page PDF shows spectra of the open loop and residual displacement noise for SRCL, MICH and PRCL. The 4th page shows the coherence of SRCL with the other 2 degrees of freedom.

The SRCL spectra has a curious shape: it comes down quickly with frequency to 10 Hz, then is fairly flat from 10 Hz to 50 Hz, then falls by a factor of 5 or so to the (presumed) shot noise level that is reached above 100 Hz. What is this noise shelf between 10 Hz and 80 Hz? That is exactly the region where the SRCL noise coupling to DARM is troublesome. Our usual approach is to send a SRCL correction path to DARM to reduce the coupling, but this spectrum shows that there should also be some gain to be had by reducing this noise shelf.

The last page of the PDF shows the coherence between SRCL and MICH & PRCL, and it indicates that the SRCL noise shelf could be coupling from PRCL noise -- the coherence is fairly high in this band, though not unity. This suggests that the DRMI signals could use some of the demodulator phase and input matrix tuning that Rana has recently done on L1, reported in LLO log entry 19540.

To complete this log entry, it would be useful if someone at LHO could add the open loop transfer functions for each loop (models), and other pertinent info such as DC photocurrents for these detectors and the input matrix coefficients.