[Keita, Gabriele]

Summary

The ISS second loop is working fine, we could operate it at 36 W input power, with a bandwidth of about 16 kHz, all three boosts on, with a open-loop gain of 41 dB at 1 kHz.

Details

Today we continued out work on the ISS second loop. At the beginning we could engage the second loop at 2 W input power, with a gain of 26 dB, and then increase the power to 5 W. However, from 5 W up, it was not possible to have a second loop unity gain frequency higher than about 1-2 kHz. If the gain was any higher, some intermittent oscillation were visible in the time series and spectrum of the ISS signals.

We decided to go to the floor and measure the second loop open-loop transfer function with the analog input. There was a large peak at about 82 kHz, giving us less than 5 dB of gain margin. This explained why we could not increase the ISS second loop gain, and why we failed increasing smoothly the power. We traced the problem to a gain peaking in the ISS first loop: by reducing the first loop common gain from 13 dB to 8 dB, the peak was gone and we were able to smoothly increase the ISS second loop gain.

With an input power of 36W (the maximum we could get) we set the ISS second loop gain to 20dB, obtaining a unity gain frequency of about 16 kHz. We then disabled the AC coupling loop (by holding the output and disabling the input) and could engage all three boosts. The ISS second loop open-loop gain at 1 kHz was 41 dB. There is no visible transient when engaging or disengaging the boosts. NOTE: this measurement was taken with an input power of 2 W and increasing the ISS second loop gain to 40 dB to make the boosts stable.

Plots

The first plot attached below shows the open loop transfer function of the ISS second loop with the AC coupling on (blue) and off (red), without any boosts. You can't engage boosts with the AC coupling on.

The second plot shows the in-loop (red and green) and out-of-loop (blue) error signals without boosts (green) and with boosts (red).

The third plot shows some measured OLTF with AC coupling on: BLUE = 2 W gain 26dB, GREEN = 4 W gain 26 dB, BROWN = 8 W gain 36 dB, pink = 8 W gain 20 dB, CYAN = 16 W gain 17 dB, RED = 36 W gain 20 dB

The fourth plot shows the effect of the ISS first loop gain: there is gain peaking at ~80kHz when the first loop gain is 13 dB, no peaking when the gain is 8 dB.

The fifth plot shows the engagement of the boosts. NOTE: this measurement was taken with an input power of 2 W and increasing the ISS second loop gain to 40 dB to make the boosts stable.

The sixth plot shows the effect of switching on and off the AC coupling loop.

Danny, Georgia

This morning we worked on the ETMY HWS table. All mirror labels are referenced from this diagram.

• We installed a new 50 um core fiber on the output of the SLED, in place of the old 200 um core fiber. There is still some clipping on the table but we believe the clipped beam is only the cladding modes of the fiber. The first two attached pictures show the beam with a bright center (core) and dimmer halo (cladding): the first is a picture of the beam ~50 cm after the SLED (before any mode matching optics), the second is at HWS-M4.
• We replaced the mirror mount of HWS-M2 with a picometer controlled mount (though have not installed the picometer controllers).
• We tweaked up the alignment on the table, getting the SLED beam and ALS beam reflected off the ETM co-aligned, and the alignment onto the Hartmann camera.
• The SLED beam reflected off the test mass is visible on the HWS (third attachment). It looks like there is some clipping in yaw.

A continuation of alog 43151.

I noticed the IMC in power was running at 37W, and the new large area EOM PD was reading much less than that, so I adjusted the calibration of H1:IMC-PWR_EOM_OUT16, and H1:PSL-EOM_A_DC_POWERMON channels, so they now read 37W.  Snapshots of changes attached.

Note h2b, not h2a.

h1sush2b experienced a timing glitch at 13:09, we think due to activity in the CER. IO Chassis comms were not lost, I restarted the models after they were safe'd and sdf'ed (h1susim, h1sushtts{rm1, rm2}).

   With the return of high pressure over the area the haze and smoky conditions have also returned. There are dozens of fires burning all around the west and northwest, which are contributing to the degraded air quality.  See the attached NW-Fires map.

   These conditions are forecast to persist until Wednesday at the least.

   Exercise caution when working outside. It is best to stay inside with you have respiratory issues or are experiencing things like burning/watering eyes, burning in your lungs, shortness of breath and/or persistent coughing. If symptoms do not improve you should consult your doctor.

Morning Particle Counts (per cubic foot of air)

The PEM corner station AA chassis have some dead channels and will need to be removed for repair:
Channel 7 (bottom chassis) - (MIC EBAY)
Channel 2 (bottom chassis) - (MIC HAM7)
Channel 29 (2nd from bottom chassis) - (MIC INPUTOPTICS/HAM2)

Cables will be run for accelerometers in the following locations this Tuesday:
HAM 1 - X, Y, Z (top)
HAM 2 - X
HAM 5 - Y, Z (top)
HAM 6 - Y
BSC 2 - X, Z (bottom)
BSC 3 - Z (bottom)

Sheila, Haocun, Nutsinee

This morning we had a chance to inject the squeezer seed beam with the main interferometer misaligned while people were working on HWS and the ISS.  We didn't have trouble finding the beam or aligning it to the SRM angle we have been using recently for locking.  Attached is a screenshot of the slider values for which we can close the AS centering loops on the seed beam and close the OMC QPD loops.  

We took an OMC scan, but it is possible that the seed beam was resonating a higher order mode, so we will have to return to this.  

12 hours of minute trends where the winds where over 5 meters/second(mps), [~11mph] are attached.  First is the means of the three sensors overlayed.  Looks okay with some rough times.

Second plot has the three sensors plotted separately and the differences between the sensors; ideally the difference is zero.  Some areas of larger (~1mps) diffs and other times where they are very small.  The bimodal trend may be from shifty directions, gustiness, or maybe the trends themselves.  It's a long stretch of time but I'll zoom in and check second trends and full data where able.

Laser Status:
SysStat is good
Front End Power is 33.7W (should be around 30 W)
HPO Output Power is ~74W
Front End Watch is GREEN
70W Watch is GREEN

PMC:
It has been locked 0 days, 0 hr 0 minutes (should be days/weeks)
Reflected power = 15.07Watts
Transmitted power = 41.82Watts
PowerSum = 56.89Watts.

FSS:
It has been locked for 0 days 2 hr and 4 min (should be days/weeks)
TPD[V] = 1.969V (min 0.9V)

ISS:
The diffracted power is around 3.1% (should be 3-5%)
Last saturation event was 0 days 0 hours and 20 minutes ago (should be days/weeks)

Possible Issues:
LRA out of range, see SYSSTAT.adl

Today:
Hartmann table work at end Y

Tuesday:
Property services audit
Vacuum wiring at both end stations
Charge measurements
Concrete pouring at mid X and behind VPW
PEM cable runs for accelerometers in LVEA
HAM1 HEPI loops updated to be more aggressive
HAM2/3 model change and test
Moving anemometers at wind fence
PSL PD commissioning
PSL IO photos
WAP updates 6-8 am
Beckhoff topology change at end Y

All plots seem nominally ok.

Restart of h1sush2a following loss of communications with IO Chassis.

model restarts logged for Sat 11/Aug/2018
2018_08_11 08:31 h1iopsush2a
2018_08_11 08:32 h1iopsush2a
2018_08_11 08:33 h1susmc1
2018_08_11 08:33 h1susmc3
2018_08_11 08:33 h1suspr3
2018_08_11 08:33 h1susprm

Sheila, Craig, Georgia

We've had another difficult day for locking, perhaps because it has been windy but there might be something else going on. Here are a few things that we did:

• Changed PRC ALIGN in Initial alignment to use REFL A 9I instead of B for PRX alignment, because it seems like the lock point of B is not correct for yaw, while the lock point of A maximizes the build up. 
• offloaded the OM alignment sliders due to last night's move of the AS_A pico
• Yesterday we reduced the IMC UGF back to 35 kHz, because Craig saw that the IMC has been loosing lock on its own (overnight when no one was trying to lock) since we increased the UGF to 85 kHz. I also reduced the gain for ALS COMM this morning to compensate.
• We've had trouble with DRMI acquitision, and RF DARM, and DHARD WFS. 

[Nergis, Haocun]

After locking the OPO, we were able to get a locked SEED beam on the SQZT6 for homodyne work.

Main steps:

• Homodyne balancing:
  • Adjust the LO beam power to ~0.5mW on each diode.
  • Rotate the BS until the DIFF channel gets to 0.
• Visibility maximize:
  • Adjust the LO beam power to the same level with SEED.
  • Block one of the diodes, and use the DIFF channel for measurements.
  • Adjust the alignment by steering the mirrors in the SEED beam to get a maximum visibility.
  • Moving the lenses around to get the best lens positions for the final maximum visibility.

We did the visibility maximization process with PD2, getting 96%, but it was only 92% for PD1. Then we found that when the homodyne is balancing for the LO beam, the two diodes read very different values with the SEED beam. I checked the polarization of the two beams, and both of them are well s-polarized.

This led me to go back and recheck the diodes of the homodyne, finding that PD2's reading is only about half of value of PD1 when shining the same beam on them. Also, Daniel and I inspected with an IR viewer, and found that there is a bright reflection from PD2. We probably need a new diode for PD2, but this means the mode matching is good enough, and we can still use the current set up to work on the CLF and LO loop.

Some changes of the mode matching solution: (I will update the diagram later soon.)

• L0: ROC = +350mm
• L12: ROC = +150mm
• L13 is removed.
• Now both of the beam waists are ~200um located at ~2inches before the BS.

Craig, Hang, Georgia, Sheila

We've been having trouble locking, probably because of the wind and a small EQ, and perhaps because the IMC UGF was too high.  We decided to use some single bounce time to investigate why we can't engage the OMC ASC.  We were able to engage it when we were doing OMC scans just over a week ago. We haven't been able to lock the OMC because we rail the OM3 +OMC suspensions if we try to engage the QPD loops.

Hang and I noticed that the picomotor for AS_A was accidentally moved on August 7th.  Even though the settings were set back, we suspect that the pointing onto the QPD may not have been restored because of the hysteresis of the picomotor.  On August 7th the AS_C pico was moved for a better SR2 pointing through the OFI.

Craig used his script that restores optics to a given time using the top mass witnesses to restore SR2, OM1,2,3 and the OMC to their alignments from July 31st at 22:53 UTC, which is the time of one of our single bounce scans. We saw that this brought the OMC QPDs closer to their lock point, and pico'd AS_A to center the beam on the diode.  AS_B pico has not moved since Thomas Vo adjusted it in June so we didn't touch that. Once AS_A was centered here we closed the AS centering loops, and pico's AS_A while it was in loop to bring the OMC ASC error signals to zero.  

After this was done we were able to close the OMC APD loops without a problem, and then walked SR2 back to it's more recent alignment.  The OMs are still not railed. 

We have started a 1 hour ring heater test at 04:00:00 UTC. The ring heater on ETMX will run for 1 hour at 3W.

We have shuttered the ALS green beam while we do this test, it can be unshuttered in the morning.

Corner station RGA scan attached. N2 peak is high. We will monitor to see how it decreases with time. SEM voltage set to 1300V.