Starting CP3 fill. LLCV enabled. LLCV set to manual control. LLCV set to 50% open. Fill completed in 38 seconds. LLCV set back to 16.0% open.
Starting CP4 fill. LLCV enabled. LLCV set to manual control. LLCV set to 70% open. Fill completed in 1902 seconds. TC A did not register fill. LLCV set back to 43.0% open.

model restarts logged for Thu 23/Mar/2017 - Mon 20/Mar/2017 No restarts reported

no code changes during Tuesday maintenance.

We always thought that the video of ITMY is worse than ITMX but we were not sure about the camera/lens setting.

Richard opened the iris of both ITMX and ITMY gige camera all the way on Tuesday, and they still look the same. In the attached, several pictures with different exposures are combined, but even without doing anything ITMY looks obviously brighter.

Is there any hidden variable here?

(Added later: Non-conclusion of this alog is, it seems as if ITMY HR has larger scattering than ITMX HR, and that ITMX HR doesn't seem to have a  single big scatterer, but I'm still wondering if this is due to some hidden setting somewhere.)

I have added an (unreleased) algorithm into the GDS/DCS pipeline to compute the SRC spring frequency and Q. This algorithm was used to collect 18 hours of data on February 4 (first plot) and 18 hours of data on March 4 (second plot). The plots include kappa_c, the cavity pole, the SRC spring frequency, the SRC Q, and 4 of the coherence uncertainties (uncertainty of the 7.93 Hz line is not yet available).

The derivation this algorithm was based on is similar to what Jeff has posted ( https://dcc.ligo.org/DocDB/0140/T1700106/001/T1700106-v1.pdf ), with differences noted below:
1) The approximation made at the bottom of p4 and top of p5 was only used in the calculation of kappa_c and the cavity pole. So SRC detuning effects were not accounted for in computing S_c. However, kappa_c and the computed cavity pole were used in the calculation of S_s.
2) In eq. 18, I have a minus (-) sign instead of a plus (+) sign before EP6. S_c = S(f_1, t) has been computed this way in GDS/DCS since the start of O2 (I assume during O1 as well).
3) Similarly, in eq. 20, I have a minus sign (-) before EP12.
4) In the lower two equations of 13, I have the terms under the square root subtracted in the opposite order, as suggested by Shivaraj. (Also, I noted that the expression for Q should only depend on S(f_2, t), with no dependence on S(f_1, t). )

The smoothing (128s running median + 10s average) was done on f_s and 1/Q, since that is the way they would be applied to h(t). Therefore, the zero-crossings of 1/Q show up as asymptotes in the plot of Q. I think it would be better to output 1/Q in a channel rather than Q for this reason.

There is a noticeable ramping up of f_s at the beginning of lock stretches, and the range of values agrees with what has been measured previously.

I've noted that it is quite difficult to resolve the value of Q with good accuracy. These are some reasons I suspect:
1) Higher uncertainty of calibration measurements at low frequency can add a systematic error to the EPICS values computed at 7.93 Hz. This may be why the Q is more often negative than positive ??
2) In the calculation of S_s, the actuation strength is subtracted from the ratio of pcal and DARM_ERR. Since this is such a low frequency, the subtracted values are close to the same value in magnitude and phase. Thus, subtracting magnifies both systematic error and uncertainty.
3) The imaginary part of S_s (see eq. 13, bottom equation) in the denominator, is very close to zero, so small fluctuations (about zero, as it turns out) in 1/Q cause large fluctuations in Q.

These reasons make it difficult to measure Q with this method. The effect of these measured-Q fluctuations on S_s, the factor we would actually apply to h(t) (see eq. 22), is not enormous, so long as we apply the smoothing to 1/Q, as I have done here.

TITLE: 03/24 Day Shift: 15:00-23:00 UTC (08:00-16:00 PST), all times posted in UTC
STATE of H1: Observing at 67Mpc
OUTGOING OPERATOR: Patrick
CURRENT ENVIRONMENT:
    Wind: 5mph Gusts, 4mph 5min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.38 μm/s
QUICK SUMMARY: Glad to see us recovered from yesterday and we are now riding a 4 hours lock at 67Mpc

TITLE: 03/24 Owl Shift: 07:00-15:00 UTC (00:00-08:00 PST), all times posted in UTC
STATE of H1: Observing at 67Mpc
INCOMING OPERATOR: TJ
SHIFT SUMMARY: One lock loss. Cause not immediately apparent. No major issues relocking. Had a verbal alarms notification of a timing system error (see alog 35058). Tumbleweed baling has started at LSB.
LOG:

Closed bash terminal that was obscuring screenshot of nuc0 DMT Omega plot
10:27 UTC Lockloss
11:07 UTC Back to observing
11:11 UTC PI mode 28 rang up and back down on its own
11:19 UTC Changed phase to damp PI mode 27
11:50 UTC Verbal alarm: Timing system error.
14:04 UTC Tumbleweed balers started tractor, waiting for it to warm up, then driving it to start baling at the LSB.
14:38 UTC Damped PI mode 27

I have shut down the instrument air compressors at M X. All of the pneumatic actuators have been replaced with electric actuators. The only call for air at that station would be when the vacuum system needs to run the turbo pumps or for the water storage tank. The compressors are still readily available for these functions, they will just need to be turned back on. 
Eventually all of the I A compressors will be placed in this stand by mode and not continually running and cycling, saving both electricity and maintenance cost.
I do plan to cycle these on a monthly basis just so they will be ready when needed.  

At 11:50:12 UTC verbal alarms reported: 'Timing system error'. I worked my way through the timing medm screens, trending each error channel to see which screen to go to next. In the end I found H1:SYS-TIMING_C_FO_A_PORT_2_SLAVE_ERROR_CODE went to 40 briefly. I'm not sure how to interpret this. Trends of the sequential error codes are attached.

Lost lock at 10:27 UTC. Cause unclear. Almost back to NLN.

TITLE: 03/24 Owl Shift: 07:00-15:00 UTC (00:00-08:00 PST), all times posted in UTC
STATE of H1: Observing at 67Mpc
OUTGOING OPERATOR: Jeff
CURRENT ENVIRONMENT:
    Wind: 6mph Gusts, 4mph 5min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.37 μm/s 
QUICK SUMMARY:

No apparent issues.

Shift Summary: In Commissioning mode at start of shift. One Commissioning Lockloss. Relocking the IFO took a couple of tries. Robert ran the fire pump (WP #6529) while LLO was down. Back to Observing after Robert finished fire pump test.  

A2L Pitch is well below the reference; Yaw is up to about 0.7

There is still a bit of noise in 20 to 50 Hz, which is moving the range around. Other than this, the rest of the shift passed without difficulty.

   Back up and Observing after commissioning work finished. When we first locked the noise between 20 and about 100 Hz was bouncing around and keeping the range suppressed. It has subsided and the range is back up around 67 to 71 Mpc. 
   All good at this time. 

   Bubba called - The tumbelweed balers are finished on the X-Arm for the evening. Work will resume tomorrow morning, probably around the LSB. 

Daniel, Keita, Richard, TJ, Kiwamu,

We found that the newly installed harmonic generator (35033) had different relative RF phase than the previous for all the harmonic frequencies with respect to the seed frequency 9 MHz (as pointed out by Daniel, 35038).

This impacted on interferometer's sensing demodulation phases at several places, making us unable to lock the interferometer.

We spent almost all the working hours today retuning the relevant demodulation phases. After retuning them, we managed to get back to full lock.

[Adjustment of demodulation phases]

See the attached SDFs for a summary of the changes. Here is a list of the demodulation phases that we changed today.

• LSC-REFLAIR_B_RF27
• LSC-REFLAIR_B_RF135
• LSC-POPAIR_B_RF18
• LSC-POPAIR_B_RF90
• LSC-ASAIR_B_RF90
• ASC-AS_A_RF36

Even though we could have tuned ASC-AS_B_RF36, we decided not to do this today. According to ASC-AS_A_RF36 which needed to change its demodulation phase by -23 deg, a sensible thing to do is to rotate the AS_B as well by the same amount. However, because AS_B_RF36 is not in use in full lock and is used only for lock acquisition which went smoothly without changing the demodulation phase, we don't bother it for the moment.

REFL27 was adjusted by minimizing the PRCL contribution in its Q phase. REFL135 was adjusted by minimizing the SRCL component in its Q phase. The 2f signals (18 and 90 MHz) were adjusted to maximizing the amplitude in their I phase when the DRMI was kept locked with both arm cavities held at a off resonance point. ASC-AS_ARF36 was adjusted by minimizing the BS contribution in to its I phase.

[Adjustment of 3f input matrix]

As we adjusted the demodulation phases, we also went through checking the input matrix for the 3f signals for holding the DRMI. We have changed the REFL27I -> PRCL gain from -4.0 to -2.0 and the REFL27I -> SRCL gain from 0.6 to 3.2. The former was adjusted to match the optical gain of REFL9I and REFL27I by exciting PRM at 30 Hz with 10 counts. The latter was adjusted by minimizing PRM coupling into the SRCL signal with an excitation on PRM at 30 Hz with a 10 counts.

These changes are implemented in the ISC_DRMI guardian.

[Electronics measurement and some phase madness]

In addition to these adjustments, Keita, Richard and I went to the CER and measured the relative RF phase between the old harmonic generator unit and the new one for each harmonic frequency using an RF analyzer. With this measurement we attempted to determine the required demodulation phase changes before actually changing the demodulation phases ini the digital system. However this didn't really work out for the following reason.

We brought the old unit to the CER with us and powered it up right next to the newly installed unit. We then split the 9 MHz seed via an RF distribution amplifier into two and fed each of them to each harmonic generator unit. Then we measured the relative phase and amplitude of all harmonic pairs (e.g. 18 MHz from the old unit v.s. 18 MHz from the new unit). However, as it turned out later, the RF distribution amplifier had random relative phase between the outputs. This, of course, screwed up our assumption that the input of the two harmonic generators were synchronized in their phases. Since we didn't measure the relative phase between the two seed signals, the measurement helped only for figuring out the demodulation phases associated with the 45 MHz family.

Nonetheless, I post the measurement results here for the record.

Note that this measurement was performed before we changed the RF attenuates (35045).

Upon entering the control room, I noticed that we have a low frequency oscillation in the PRC gain, POP DC, etc. on our front wall striptool.  Turns out, this is the same as what Jim documented last night in alog 34999, and likely comes from Sheila's changing of the oplev damping cutoff in alog 34988.

I would like to go back to the old 10 Hz cutoff that we used to have in the oplevs, to see if that fixes this.  However, Sheila noted to me that the old cutoff is zero history, no ramp, so we can't just go out of Observe and switch filters.  I'll need to change the filters to always on, few sec ramp, load the filters, then we can switch back.

I analyzed the HWS data for the lock-acquisition that occurs around 1173641000. The "point source" lens appears very quickly (within the first 60s) and then we see a larger thermal blooming over the next few hundred seconds. I've plotted the data below (both gradient field and wavefront OPD). There are a few obviously errant spots in the HWS gradient field data. Since I'm still getting used to Python, I've not managed to successfully strip these off yet. However, it is safe to ignore them.

Check out the video too. Next step is to match a COMSOL model of thermal lensing with a point absorber to the data to get a best estimate of the size of absorber and the power absorbed (preliminary estimates are of the order of 10mW).

FYI: this measurement compares the system before, during and after a lock-acquisition (ignore the title that says "lock-loss"). The previous measurement, 34853, looked at lens decay before, during and after a lock-loss.