Kiwamu, Matt, Stefan

We were still suspicious of the 2-omega RF buildup signals, so we decided to put a line on the PRM length at 303Hz, and demodulate the line. To avoid loop feed-back we turned on the existing "notches" FM8 filter in PRCL1. POP9_I was demodulated at 303Hz in H1:LSC-LOCKIN_1_DEMOD_3_I_OUTPUT.

Assuming good overlap, we would expect the gain to scale as sqrt(carrier recycling gain * 9MHz recycling gain).

Interestingly, the 9MHz sideband drops by about the same amount as the carrier, but with a timne constant of about 10min (vs about 1 min for the carrier).

The attached plot shows the power increase to 40W, without the soft offset adjustment that usually happens right away. All scales (except purple) start at zero at the bottom of the plot.

Conclusions:

- POP18 is not reliable - it suggest a larger gain drop than the optical gain.

- The optical gain (RF9 & carrier) does drop by the same 25% as the carrier, but on a much longer time constant.

Following my talk at the Systems meeting, I've added some pdfs to the DCC entry with 'publicity plots' of the improvements due to the BRS:
G1601529: Tilt- and Sensor-correction filter tuning at LHO.

The figure of merit I apply to these plots is that we want to reduce RMS velocity. I believe this is the correct figure of merit 
from DC up until at least the lowest Quad resonances. This saves us the worry of trying to compare bumps and dips in spectra. In all the 
following plots, the dashed curves represent the high-to-low RMS of the solid curves of the same colour. Most of them start from some 
cut-off frequency, to isolate the low frequency contributions. In general, the output of all inertial sensors can be regarded as noise 
below 0.1Hz, since it's either uncorrelated or it's something that will be common to the ends and the corner.

The only new figure here 'Sensor correction vs not' suggests that the noise injection from sensor correction, about 8e-8m/s from 0.1Hz to DC, 
is lower than the potential benefit of sensor correction, about 9e-8m/s from 0.3Hz to 0.1Hz, even with high winds (25mph) and very low 
microseismic motion. With higher microseism and lower wind, this ratio will only improve. Still, during very quiet times, we may be better 
off disabling low-f sensor correction everywhere.

at 16:58 PDT all user models on h1susey stopped running. It looks like the IOP model developed a DAC error, and stopped running all the DAC cards (and also powered down the SUS-AI chassis). The IOP model continued to run (user models had stopped with ADC TIMEOUT errors in dmsg), so we could determine the SWWD RMS readbacks were well below trip levels. Hugh got seismic driving again by overriding the broken SUS IPC.

At 17:09 PDT I restarted all the models on h1susey (iop, etmy, tmsy and etmypi). 

Title:  07/13/2016, Day Shift 15:00 – 23:00 (08:00 – 16:00) All times in UTC (PT)
State of H1: IFO unlocked. Peter working on FSS instability. 
Commissioning: 
Outgoing Operator:  None
 
Activity Log: All Times in UTC (PT)

14:35 (07:35) Peter – In the LVEA working on the FSS
14:56 (07:56) Peter – Out of the LVEA 
15:00 (08:00) Start of shift
17:10 (10:10) Carlos – Rebooting Digital Video Server-1
17:30 (10:30) Peter – Alignment work on PMC (WP #5994)
18:45 (11:45) Hertz Equipment Rental on site to deliver snorkel lift to End-Y (WP #5995)
20:39 (13:39) Robert – Going to End-Y to setup magnetometer
21:10 (14:10) Kyle – Going to Mid-Y to overfill CP3
21:14 (14:14) Robert – Back from End-Y
22:18 (15:18) Kyle – Back from Mid-Y
23:00 (16:00) Hand off to Nutsinee
 

End of Shift Summary:

Title: 07/13/2016, Day Shift 15:00 – 23:00 (08:00 – 16:00) All times in UTC (PT)
Support:  Peter, Cheryl, Stefan, Sheila, Keita, Kiwamu
Incoming Operator: Nutsinee 

Shift Detail Summary: Peter working on FSS instability. Working on relocking after FSS was stable. Locked at INCREASE_POWER, 39.5W. Hand off to commissioners.  

1440 -1510 hrs. local -> To and from Y-mid 

Opened exhaust check valve bypass valve, opened LLCV bypass valve 1/2 turn -> LN2 @ exhaust in 60 seconds -> Restored valves to as found configuration. 

Next CP3 overfill to be Friday, July 15th. 


Also, demonstrated MTP Safety Valve functionality when backed by local scroll pump (rediscovered that the "NORMOAL" light LED on the turbo controller is burned out) -> Let MTP brake phase complete but am leaving turbo rotor levitated, i.e. controller energized, overnight -> will de-energize tomorrow. 

(C. Gray, H. Radkins, M. Robinson)

Ran through the new SEI FAMIS task, H1 ISI CPS Sensor Noise Spectra Check (this one is #6854).  Will be making slight edits to the procedure, but it should be ready to add to the line-up of FAMIS tasks for LHO Operators. 

This is a weekly measurement and I picked a quiet measurement time from about 2am PST.  Running the measurement for the BSC & HAM ISIs did NOT show any blaring issues with the CPS.  Hugh's eye was caught by a bump for the ETMx's Stage2 at around 67Hz.  (Screenshot of BSC & HAM CPS spectra is attached).

Attached are pressure trends from cold cathode gauges from Jan. 2016 to now. The noise level of the gauge seems to be higher since Beckhoff system was installed.

With the long total duration from 0 to full lock it becomes more important to shave off some script run time where possible.

In that spirit I relaxed the tolerances for ASC convergence in CARM_ON_TR, which is just before the automatic WFS relief:

                # tolerances retried on 20160713
                # wfsTolerancePit = [5,200, 100, 300, 200, 100] 
                # wfsToleranceYaw = [5,200, 100, 300, 200, 100]
                # tolerances from 20160713, intended for speed-up
                wfsTolerancePit = [5,400, 200, 600, 400, 200]
                wfsToleranceYaw = [5,400, 200, 600, 400, 200]
 

If the quality of the relief gets worse, we might have to revisit then. (I suspect that the thermal heating at 40W is the bigger problem though.)

The FSS had a hard time acquiring lock and staying locked this morning.  I had noticed that the pre-modecleaner
reflected spot looked "mis-aligned".  The pre-modecleaner alignment was tweaked up, bringing back the vaguely
familiar reflected spot.  The reference cavity alignment was also tweaked up but really there was no substantial
improvement in its transmission.

    Whilst the frequency servo was trying to acquire, I noticed that the injection locking relock counter had
jumped from ~3 this morning to over 40.  In addition the high power oscillator PZT showed a few discrete level
jumps.

    Even with the input modecleaner disabled, the laser frequency was being yanked as can be seen from the reflected
spot showing more than the usual two lobes.  I tried re-acquiring the FSS lock at a different NPRO crystal temperature.
Previously the slow voltage slider was around -0.0010.  Now it is around -0.2630.  I have also changed the locking
search ramp to reflect this.  Things seem to be more stable at this operating point - the input modecleaner acquired
lock for a start.

    If the FSS lock is reacquired at a slow voltage close to zero and the FSS has a hard time maintaining lock, and
things seem better at a different slow voltage, this could be an age-related symptom of the NPRO.  Something to watch
out for.

Here are some plots comparing a power up from the end of O1, where we didn't have a significant drop in power recycling gain going from 2 Watts to 23 Watts, to one from last night.  

The first plot shows several monitors of recycling gain for the 2 power ups, plotted against time in the middle coumn and input power in the third column.  All three monitors of carrier recycling tell the same story: In december the recycling gain didn't drop significantly between 2 watts and 25 Watts, now it drops 6-8% by 23 Watts and 15-16% by 40Watts of input power. The beahvoir of AS90 drops by about 8% going from 2 Watts to 23 Watts, and 15% by 40 Watts, which is not sigificantly different from the behavoir in Decemeber.  The power at POP18 drops by 48% durring the power up, we can't compare this to December since the diode was saturated then.

The second plot shows the power on the baffle PDs durring the 2 power ups.  It shows that even before we had a bad recycling gain drop, we had a lot of power hitting the baffle PDs.  

Ed, Hugh

...at least I'm confident they are. If folks could keep an eye on these occurrences asnd report any foolery to me, for now, I'll assume no news is good news.

JeffB reported the ITMX was found tripped this morning.  Pretty clearly it was the arrival of the S-waves ; the platform is already tripped when the largest amplitude, lower frequency surface waves arrive later.  The attached trend clearly shows the sharp peaks arriving at the ground STS in the Bier Garten at the moment the Watchdog State goes high.  Why the ITMX is the platform that is most sensitive is an ongoing investigation.  The earliest arrive P-Wave should be largely vertical (Z) where the next arriving S-Waves will be horizontal. A Clue!!

Tried to do some FSS related measurements to see why it was the FSS kept losing lock.
Unfortunately it seems the FSS fieldbox signals of interest - which is just about all
of them as far as transfer function measurements are concerned - are not of any use
in their current state.

    In doing a measurement this morning, the injection locking was broken which in
turn tripped the high power oscillator's power watch dog.  The laser restarted without
any issue.

The missing equipment hunt concluded with limited success. There are still a few items missing. 
Fred, Vern, and Richard thanked all for the efforts. 

PSL – Looking into an instability with the FSS.
CDS – Working on frame writer problem
VAC – Will need to bake out the End-Y RGA before O2. 
All other subsystems report no problem.

There will be no maintenance window on Thursday.
There will be a safety meeting this afternoon at 15:00.

   The ITM-X ISI Stage 1 and Stage 2 WDs tripped at 12:35:25 and 12:35:30 (UTC) respectively. No problem resetting. Was not highlighted on Ops Overview MEDM. 

Nutsinee, Kiwamu,

WP5990

We have (re-) set up the polarization monitors on the HWS table by HAM4. We have confirmed that they are functional. For those who are interested in the polarization data, here are the channels to look at:

• H1:TCS-IFO_POLZ_S_HWS_OUT
• H1:TCS-IFO_POLZ_P_HWS_OUT

In theory, they should be in unit of watts as measured at the HWS table.

[Installation notes]

This time, we have newly installed a short pass optic (DMSP950L from Thorlabs) to pick off the main interferometer beam without getting too much contamination from either the SLED light (790 nm) or the ALS beam (532 nm). The short pass mirror was inserted between the bottom periscope mirror and the first iris (D1400252-v1). Looking at the green light at the table from the end stations, we learned that the beam size is already pretty small and (visually) small enough for the beams to fit into the PDA50Bs without a lens. So we decided to go without lenses as opposed to the previous setup (24046).

The short pass mirror reflects the interferometer beam toward the left on D1400252. We placed a PBS (CM1-PBS25-1064-HP) on the left side of the short pass and placed the PDA50Bs. The power reflectivity of the newly installedshort pass mirror was measured to be 5% +/-3% for 532 nm. The absolute power (assuming the Nova hand held power meter is accurate) of the reflected green light was measured to be 1 uW.

One thing we leaned today was that the green light is not so trustable to get the optimum alignment. We first aligned the optics with the green light and then noticed that the infrared beams were almost falling off of the PDA80Bs. So we then closed the shutters and aligned them with the actual infrared beam.

The manual gain settings are:

• S_POL: 70 dB
• P_POL: 50 dB

The digital gains were also changed accordingly so that the calibration of these channels should be accurate.

J. Kissel, S. Dwyer, S. Ballmer

We continue to have trouble with the FSS oscillating after a lock loss, in that it'll often either take several minutes to relax, or it requires manual intervention such as briefly reducing the common gain of the FSS loop. As such, Sheila took a look at the IMC PDH loop to look for problems and instabilities there. I looked over her shoulder at her results, and saw some areas for improvement in the loop design. The current loop design has an UGF at 66 [kHz], with a phase margin of 68 [deg]. However the gain margin around ~200 [kHz] is pretty dismal because of what looks to be some icky features in the physical plant. These features have been shown to be directly influenced by the FSS common gain (see second attachment in LHO aLOG 28183).

I figure, given that we've got oodles of phase margin, what harm could be done by just adding a simple 200 [kHz] pole in loop, and reducing the gain by ~2 [dB]? As such I took Sheila's data, which lives here 
/opt/rtcds/userapps/release/isc/common/scripts/netgpib/netgpibdata/TFAG4395A_12-07-2016_163422.txt
(also attached) and added these modifications offline as a design study. 

In the attached plots, I compare the as-measured IMC PDH Open Loop Gain, G, Loop Suppression, (1/1+G), and the Closed Loop Gain, (G/1+G), against one modified as described above (blue is as measured, and green is the modified design study). 

The results are encouraging: a still-substantial UGF of 47 [kHz], and a very-healthy phase margin of 58 [deg]. However, as can bee seen in the loop suppression and the closed loop gain, there is far less gain-peaking and/or a much great gain margin and we would no longer have to worry about the icky features in the plant that are so sensitive to the FSS common gain.

Where to stick such an analog filter? It's of course dubious to claim that the MEDM screen for such a system is representative of the analog electronics, but assuming it is, one can see that there is the possibility of a switchable daughter board in the FAST path that gets shipped off to the PSL AOM for the FSS. Because it's switchable, we can toss whatever simple filter in there that we like, and then compare and contrast the performance for ~1 week to see if it improves the stability problems we've been having.

What impact would this have on the full IFO's CARM loop? I'll remind you of Evan's loop analysis of the whole frequency stabilization spaghetti monster in LHO aLOG 22188. There he suggests that the CARM UGF is around 17 kHz, so as long as the Closed Loop Gain around there is the same, then this change in the IMC PDH loop should have little impact [[I just made this sentence up based on just a few words from Sheila who asked me to look at the CLG. I'm not confident of its truth. Experts should chime in here]]. Indeed the third .pdf attachment shows that G/(1+G) of the IMC PDH loop, regardless of modification remains unity out to 100 [kHz].