With the lower noise seen in CARM, we can now see clear coherence of some higher frequency lines with DARM. The frequencies are centered at 556, 574, 835, 860, 1115 and 1148 Hz, but are not very high Q. The third set of twin lines looks like a straight harmonics of the first set, whereas the second set is 1.5 times the frequencies of the first set. This would indicate fundamentals at 278 and 287 Hz, which are barely visible. There is also a small indication of the 5th harmonics at 1393 and 1435 Hz.

Pep Covas, Sheila Dwyer

Earlier today we added some notches to top mass damping and ASC loops to try to address some of the lines in DARM Pep writes about here: 48947  We went through a similar exercise in 2016, some links are included here: 31553

We found that the 40.9Hz HSTS resonances weren't notched in the ASC signals sent to PRM, PR2, SRM or SR2, so Pep added notches to all of those loops in M3 LOCK P and Y. 

We also suspected that the 46.09 Hz line might be an HLTS resonance, in the resonance wiki they are predicted to be at 44.73Hz, but we weren't able to find measurements.  Pep added notches for 46Hz to the top mass damping for both SR3 and PR3.  

We also looked around a bit for something that could be done for the 27.7 Hz line, in the wiki the closest frequency is MC2 but it is not an perfect match.  One thing that we can try is adding HSTS notches to the MCWFS loops, which are currently missing them.  

It seems as though this has helped with the 46Hz line, and Pep is going to look more closely at the 40.9 Hz line with more data.  

We lost the AS36 phasing that I did yesterday in full lock with the computer crash last night.  I set the phase today during a DRMI-only time to zero the sum of the Q phase of AS_A_RF36, which gave me a phase 30 degrees different than my full lock phase yesterday. 

We were able to acquire lock with this new phasing.  As we thermalize, the Q sum is drifting away from zero.  Right now at about 90 minutes into the lock the ideal phase (from atan(Q/I)) is 10 degrees different than the DRMI-only phase, in a direction consistent with yesterday's measurement.  So, right now in full lock after 90 min, the ideal phasing is 20 degrees different than the value I found yesterday (and yesterday I might have overshot a few degrees).

So far, it seems as though Daniel is right that we could potentially servo the AS36 phase by calculating the arctan of Qsum/Isum.  Probably we could do this in guardian, since it only needs a ~1 minute cadence or less; it's not a fast thing that would require a model change (although we could do that too or instead).

 The multi-mode misery of the squeezer laser continues. 22 days ago the laser was adjusted and it looked reasonable for a few days with 45-50mW green output. Now it seems to vary between 35 and 45mW. At 40mW and below the power stabilization circuit is running out of range and rails the actuator.

It was reported that we cannot lock the squeezer laser when the noise eater is turned off. This is simply due to the fact that the auto-locker stops when there is an apparent error in the laser, and the current laser screen expects the noise eater to be on. Added a new nominal state for the noise eater relay that should take care of this problem in the future. It requires the new Beckhoff code to be activated first.

Ops Shift Transition: 05/08/2019, Eve Shift 23:00 – 7:00 (16:00-00:00) - UTC (PT)

State of H1: Locked

Intent Bit: Commissioning

Weather: ~10 mph wind, sunny

Primary 0.03 – 0.1Hz: 0.01 um/s

Secondary 0.1 – 0.3Hz: 0.1 um/s

Outgoing Operator: Jeff

Quick Summary: Locked for ten minutes, Jeff is in charge of the IFO for calibration work.

It looks like the PR3 sliders weren't restored after the Dolphin crash last night, so our IFO alignment has been a bit wonky all morning (one lock we saw some beam on AS AIR even with the beam diverter closed, which indicates something is definitely funky).

I restored the PR3 sliders, and now JeffB is doing an initial alignment starting with INPUT_ALIGN (the green arm alignment should still be fine from Corey's alignment last night).  Hopefully this will help things out a bit.

   Added 100ml water to the Crystal Chiller. 
   The Diode Chiller water level is good; no water added. 
   Both filters look good. 

  Closing FAMIS #10508

no water required at this time.

   After relocking had code error for GRD-HIGH_FREQ_LINES_MAIN node. Pep made a code change and will reload at the next opportunity. 

    Relocked the IFO (Thanks to Ed & Corey) at NLN and went back into Observing after accepting the SDF Diff in the attached screen shots. 

I received a call from Jeff Bartlett that the 3 working HWS have all stopped (ITMX was not running due to the clipping issue in the vertex).

After getting permission from Jeff, I logged into the HWS machines and found that they all stopped at the same time. Checking the disk usage confirmed my suspicion that the data disk (/data) was indeed full. We'll have to look into whether the clean-up script is still working - it might be but it's possible that it wasn't clearing out everything and this, like Thanos, was just inevitable. Once I confirm that all data more than 48 hours old is archived at CIT, we can remove all the old data and get the HWS code running again.

Keita made the point that we should phase AS36 where it needs to be for putting the BS signal all in one quadrant, and then use the MICH ASC offset if we need to adjust the BS pointing at 35W.  Keita, looking at the BS resonances while we're in lock, guesses that we're using a phase about 70 degrees away from what we should be.

When we had ~just gotten to 35W IFO lock I put in a BS pitch dither line at 8 Hz with 600 counts, and phased AS36 to minimize the peak in AS_A_RF36_I_PIT.  So far, the ASC seems okay, although we're only about an hour into the lock.  This doesn't put the SUM of Q to zero, which leaves us vulnerable to DC centering-like effects.

As Daniel has already noticed, to do this I have moved the AS_A_RF36 phase 34 degrees opposite of what I had been asking operators to do, which puts us 74 degrees different from what we had been using for the later parts of lock (after about 90 mins).  This is nearly exactly what Keita had guessed by roughly eyeballing some spectra.  The next question becomes: how was it working at all?? Have we basically not been controlling our BS motion for the last few days?  I'm hopeful, although haven't confirmed, that we'll be able to acquire lock with this phase and not have to change things part way through the lock, with the idea that we had been acquiring with a phase about 40 degrees wrong, but then moving it a further 30 degrees in the wrong direction made the gain in MICH ASC so low that we weren't controlling the BS, which is why we struggled to lock.

   Ran initial alignment and relocked the IFO after the Tuesday maintenance window. Ready to go into Observing after accepting the SDF Diffs in the screen shots posted below. 

Cheryl Daniel

The IOT2L table drawing can be found here: D1300357. We installed a 2" turning mirror after IO_MCR_M3 a the location of IO_MCR_BD2. The beam is sent to the right on the drawing where it encounters a 2" lens with focal lens 100mm. A Thorlabs PDA100A2 was installed somewhat prior to the focus of the beam and acts the trigger PD. Its gain was set to 0dB. A 14mm reflective shutter with was put in front of the IMC LSC PD. When closed the reflected beam is steered onto a razor blade beam dump.

Next we swapped IO_MCR_BS1 with a 90:10 beamsplitter and increased the power using the halfwave plate IO_MCR_HWP1.

The power on the photodetectors before and after:

The wavefront sensors seem to have lost about 30% of power, whereas the DC PD power has increased by about 7.

We reduced the IMC IN1GAIN by 20dB. This gives us a ugf around 42kHz. Later in the locking process this gain will be increased by another 3dB which would give us a ugf around ~65kHz. This is a little bit puzzling, since we would expect a 16dB gain to give us the old ugf, which was around 70kHz.

We took about 4 hours of time for commissioning today:

• Jenne and I did some PUM/ESD crossover measurements for different A2L gains, this was orginally planned as part of the calibration activities yesterday but we didn't get to it then, so took some commisioning time for it today.  
• While this was going on, several other activities happened: 
  • Nutsinee got a measurement of squeezing and anti-squeezing as the CLF demod phase rotated for lower nonlinear gain. 
  • Nutsinee addressed a problem with the green power stabilization servo, which will probably need to be addressed again.
  • Robert and Sharan took photos looking into viewports on HAM6
  • Craig measured a few REFL spectra.
  • We also in this lock are summing the two refl detectors, which is in the guardian (48762)

A quick summary of the cross over measurements (Jenne, Sheila):

Motivation:

• We do not understand the DARM actuator below 10 Hz well, we know that angular cross couplings have a large impact on the DARM cross overs since turning off our L2A decoupling filters helped with our 4.2 Hz instabilities and helped the calibration of the PUM actuator match the model (which doesn't currently account for angular cross couplings).  Jenne did some modeling of the impact of L2P on the pum actuation: 48738 Here is document with some thoughts about the actuator cross couplings and how we could change our decoupling in teh actuator: T1900148
• Turning off the length to angle decoupling meant that we also had to turn off a boost in the PUM stage, which is not ideal since it means that we now have rather shallow offloading of the DARM actuation, and less low frequency gain.   I suspect this poor offloading and angle to length decoupling is contributing to at least some of our locklosses when the environment is challenging: 1239507497  According to the (matlab) model of the DARM loop, engaging the boost in the PUM should not be a problem. 
• While working on calibration, we measured the PUM/ESD cross over down to 10 Hz (after the L2A filters were turned off) and compared this to the pyDARM model, and we see that there is starting to be a larger discrepancy at low frequencies: 48250
• One hypothesis for why we have a discrepancy in the model of the cross over could be because of a cross coupling through the ASC loops: 
  • the pum length drive could show up in the ASC loops, either because of the mechanical coupling of length drive to pitch in the actuator or because the angular sensors are sensitive to length. 
  • The angular loops then drive the pum, where we apply a scalar decoupling gain.  We know that there is some frequency dependence of this coupling, and that our decoupling at 5-10 Hz will be worse than at 20-30 Hz, because when we used scalar gains and tried to change the dither frequency used by ADS to below 10 Hz, the angular noise coupling to DARM was increased at 20-40 Hz.  So our scalar decoupling is potentially introducing (or at least changing) a cross coupling back from the angular loops to DARM.

Measurement:

• We measured the cross over between the PUM+ UIM and the ESD by driving at L2 LOCK L, see attached screenshot.  (This is saved in the CalSVN, we will take some time to compare this to a model soon).  
• To test the hypothesis that an angular cross coupling through the A2L drivealign path is impacting our cross over, we then turned off ADS and set the A2L gains to zero, which doesn't actually move the spots on the optics. First we did this for ETMX only (pink traces), then turned off A2L on all 4 test mass PUMs (cyan).  We do see a difference in the measured cross over from 7-10 Hz with the ADS gains off.