Gabriele, Hang

We were able to close all the DRMI ASC loops, including SRC2 (AS_C -> a combination of SRM & SR2; as Gabriele pico'ed the beam to the center of AS_C).

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Earlier today we had difficulties closing the AS72 PIT loops for BS and SRM. At the same time we also noticed that the POP18 was much noisier than what we had on the past Saturday. The previously used AS36 signal also showed large offsets in PIT locking point (we tried to close the AS36_I -> SRM loop once using the o2 settings and once it was closed the POP90 started to increase).

We then realized that the whole IFO plane drifted in pitch, and our Saturday locking point for PRM (i.e. offsets in ASC POP A QPD) was no more good. After adjusting the PIT offset in ASC-POP_A_PIT_OFFSET from -0.85 (Saturday value) to -0.96 (new value), the POP18 became much cleaner and the AS72 worked again. However, now we are on the edge of the POP QPD. If the drift continues at the current pace, we will soon lose our error signal for PRM. We might need to walk the whole IFO alignment to compensate for this drift.

This issue was only in pitch, for yaw no significant drift was noticed. The AS72 for yaw also seemed to be pretty robust (as the sensing matrices measured at different times were pretty consistent for yaw).

To make the things a bit more robust, we also did the following modifications:

1. When first engaging the BS loops in DRMI+ALS, we used the AS_B_45_Q signal which was a true wavefront sensor signal and thus was more robust than AS72. The SRM was directly locked with AS72.

2. For the AS72 sensing matrix, we modified it to the following:

For PIT this matrix did not well decouple the two DOFs, yet the signals we used were relatively robust. We need to have some gain hierarchy here. For YAW the matrix was consistent with what we had on Saturday.

3. After BS zeroed AS_45 signal, we adaptively adjust the AS72 phase so that the DC power is phased into I-phase. This is currently done in the DRMI guardian ENGAGE_DRMI_ASC state. If people don't think this is the most elegant place to do the adaptive adjustment, we can think about other places to do it. 

4. After the phase adjustment, we transition the BS signal to AS72 for CARM offset reduction.

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The above procedure was put into guardian. I tested it twice by directly calling the guardian to engage the loops (before adding the adaptive phase adjustment part). It succeeded once. The other time it failed at the input part. It was probably because the PRM started from a place too far away from its locking point and the PRC1 loop was not fast enough to keep up with the INP1 and PRC2 ones.

After adding in the adaptive phasing, I could not relocked the IFO because the ALS_YARM complained about fiber polarization and I do not know where to adjust it. Nonetheless I tried it once in the DRMI only state (no arms). It seemed fine to directly calling the ENGAGE_DRMI_ASC guardian state to lock the ASC loops.

RobertS, PeterK, RickS

• With growing concerns about the state of the hinges on the acoustic door to the Laser Room, RobertS and I first tried (lightly) greasing the hinge pins with some of the Bralco or Castrol low-vapor-pressure grease used for the vane-axial fans.  Then, with the loud stick-slipping and flexing of the upper hinge still occurring, we removed the jamb-side hinge half (see photos below) after supporting the outboard end of the door leaf.  We found what appears to be excessive wear on the contact portion of the hinge pin (these hinges lift the door off of the threshold as the door is opened by rotating up an inclined plane).  We wiped the old grease off as best we could both on the male hinge pin and the female receptacle of the door-side hinge half.  We then greased the pin and re-installed the jamb-side hinge half.  The door operates much more easily and smoothly now without any obvious indication of the stick-slipping that was occurring earlier.  We should probably service the other two hinges in a similar manner.
   
• Using a nice, ~ 4 ft. long section of cable tray that PeterK got from RichardM, we started the process of organizing the cables around and under the PSL table in hopes of being able to work there without standing on cables (see photos).  We moved the ten spare Lemo cables into the tray, then improvised a method of holding them, ordered from numbers 1-10 on the side of the table (see photos).  This seems to be a big improvement for convenience and particulate control.  Lots more to be done in this regard.
   
• We had to move the dust monitor slightly in order to install the cable tray under the table.  The kapton tape holding the dust monitor intake nozzle came loose so we mounted the intake a bit more permanently.  We'll likely want to find a better location for the monitor and intake nozzle, maybe just down a foot or few toward HAM1 and mounted higher such that the input nozzle is closer to the center of the table and not so susceptible to spikes from people brushing against it as they work along the side of hte table.

Removed IP11 old controller, DualVac type, and replaced it with a new Gamma controller.  Reconfigured wiring at the breakout box, and landed the wires for the new controller.  All that freed up multiple wires at the breakout box, which are going to be used to take other signals to the vacuum rack, for example readback signals from the controller for IP15 (Ion pump at Y2-8).

While replacing this controller, the controller for one of the NEGs at Y-End (NEXTorr neg) was moved from its temporary location to its permanent location, a rack that will house all controllers for this station, see photo.

Beckhoff system at the vacuum rack will need to be reconfigured for the new controller readback signals to make sense, the controller is ON and IP11 is pumping on a very small volume, since it is isolated from the main volume via its gate valve.

This closes WP#7755.

I did another cavity scan for the OPO in vacuum.

The image is attached as below.  (The y-axes units are in volts. )

• The 00 mode for green calculated from transmitted power is now ~83% . This is higher than the last measurement here.
• The 20 mode being 13% of the 00 mode, which is also better.
• The PZT calibration is still ~20V/FSR.

Next steps:

• OPO Tec Servo controller setting for vacuum. Currently the servo works, but when we set a new temperature, the temperature goes to the other direction and then comes back.
• OPO loops improvements. (Nutseinee and Daniel are working on)
• Set the position of the crystal to the optimized location.
• Send SEED in, and measure the SEED beam mode for homodyne path mode matching, with the temperature for dual resonance without NLG.

Today, I isolated IP4 for 30 minutes or so and noted that it responded by decreasing from a nominal 2.6 mA @ 6e-8 torr to 0.6 mA (~1e-8 torr) while at 7000V,  This compares to IP12 (also isolated) which is showing 0.081 mA @ 1.5e-9 torr while at 7000V.  What's the point?  I'm glad I asked!  1.5e-9 torr is good enough for a new pump when pumping against on unbaked O-ring valve.  

I lowered the HV from 7000V to 5000V on IP4 and IP2 for a brief period this afternoon (see attached).  I've since restored them to 7000V,  

Note that lowering the pressure by increasing the pump speed does not exdpedite the recovery from a vent cycle, i.e. change the slope of the pump down.  Rather, time is the limiting factor once in molecular flow barring increasing the temperature.  

Patrick, Corey, Georgia

We have been running the old optical lever quadrant-by-quadrant effective bias measurements, accumulating data in the lead up to a potential ion-pump test. Posting the trends over the last almost-month now, for ETMX (attachment 1) and ETMY (attachment 2). I'm also posting the results from one measurement of ETMY (attachment 3), showing the transfer function of ESD quadrant drive to optical lever pitch and yaw, as a function of bias voltage, for the 3 connected quadrants.

ETMY does seem to have, on average, higher effective bias than ETMX. The measured Veff drifts significantly over time.

Danny V., TJ S.

This morning we swapped the 1" PBS ALS-M11 for a 2" from Edmund Optics to relieve some of the clipping seen on the HWSEY. The procedure was the same as for EX, but this time we had to search around a bit for a spot to be seen on both QPDs. I think we got lucky last time. Once we found and centered the spots on the QPDs with good sums, we noticed that the spots on the WFS also looked centered. We then reengaged the loops for the QPDs and WFS, and all was good.

We then checked the HWS beam and it was still clipping, mainly from HWS-M1B & HWS-M1C (table layout: <a href="https://dcc.ligo.org/LIGO-D1400241">D1400241</a>). We swapped M1C with a picomotored optic holder, and after aligning that ran out of time.

There is more aligning to be done, as commissioning permits. Aidan also wants us to try a 50um core fiber, as our 200um diverges faster than we would like.

WP 7749 (Add GS13INF..._OUT to Frames)  FRS 11049 (HAM2 & 3 GS13 Gain Switching failure)

I've only looked at the first switch failure closely but I have many more in the can (just ask the operator JeffB) now with the model change adding the GS13INF_.._OUT channels to the frames.

My theory at the moment looking at the first trip is that the corner 2 & corner 3 switching is cross wired.  I don't know where yet as that mapping is complex--working on it.  Meanwhile...

Look at the attachment and listen to my story...

After getting the GS13INF_OUTs into the frame, I put the platforms into nominal ISOLATED state except the GS13s were in the low gain mode.  I manually toggled off every filter for the GS13 gain state and noted the success of the switch.  For HAM4, every filter switched with out bothering the platform.  On HAMs 2 & 3, corner 1 H & V all switched with out bothering the platform.  Conversely, on HAMs 2 & 3, corners 2 & 3 both H & V, every switch of FM 4 or 5 tripped the platform.  I did not repeat every switch because the trips took time to recover, and, trips of the verticals on the ISI also tripped the SUSs on board.  However, every repeat yielded the same result as noted, there was no inconsistent result.  So I zoom into the first trip when I toggled the DW filter on HAM2 H2:

1/2 second of data displayed. Note the H2 (corner 2) SWSTAT change as the FM5 Dewhitening filter changes state.  So you can see that the H2 signal (upper left green) gets more high frequency noise even compared to before the switch when the analog whitening is on and its digital DW filter is on; so the digital DW goes away but the analog whitening is still on.  Conversely, looking at the H3 GS13 signal (lower right,) the analog & digital whitening and dewhitening filters are on and then the analog whitening is disabled and the digital dewhitening remains on and the signal gets very clean.  Note that the H1 GS13 signal is unaffected.

So, bottom line, current theory: corner 2 digital filter is wired to corner 3 analog filter.

Why it could be happening.  Maybe best bet is the problem where long long ago, the PSL group asks SEI/ISI to change feedthrus on the chamber because cables they had would not reach the flange.  Normally on the ISI, corners 1 & 2 are near each other because the first CPS satellite crate has room for two corners ( there is not a separate crate for each corner on the HAMs.)  When SEI changed to a different chamber feedthru, ISI cable length limits necessitated putting corners 1 & 3 into the same CPS satellite crate.  We wanted all a corner's channels to go to the same feedthru so GS13 and coil drivers cables were also moved (see SEISMIC REFERENCE note on D1002873.)  Since the CPS channels from a crate are on the same cable, corners 1 & 3 go into the same Interface chassis and hence the model must reflect this difference.  It is around here that I suspect the problem.

The python command scripts must manage to most of the time switch the corners 2 & 3 quickly enough that it seems to work, usually.  The guardian scripts however must do it just enough more slowly that it blows up.

I'll look at the other switches done and see if this story all holds up.

Dick, Marc, Nolan

Replaced 6 baluns in ISC Racks R1 and R2. The insertion loss and phase shift through each balun was measured prior to installation, and compared to the phase shift through removed balun. Serial numbers, locations, bode plots and phase differences for each are annotated in the attached file (Doc and PDF formats). Noise measurements are attached, with most recent measurement (Aug 7, 2018) after replacement of final 6 baluns in green. 

    Rick reminded me that the current pre-modecleaner was meant to be operated with a UGF of 1 kHz, as per
T1700543.  There are also loop shape changes that are not
implemented with this servo card.  However in order to reduce the UGF to 1 kHz, both the optical and electronic
gains had to be reduced.  The unlocked light level was previously ~1.35 V, is now 0.28 V.  This has been
reflected in changes to the locking thresholds on the MEDM screen.

    SCRN0006.jpg shows the pre-modecleaner open loop transfer function after the above changes were made.
SCRN0007.jpg shows the power noise measured with an out of loop photodiode.  Gone are the sharp ~22 kHz
and harmonics peaks.

Danny, TJ, Georgia, TVo

Big ups to Sheila for running our measurement after ISC was finished with their work for the night.

Yesterday Georgia and Danny put in an iris on ITMX to crop out a prompt reflected beam from an in-chamber lens so that we can try to compare the spherical power on both ITMX and ITMY HWS when injecting 6 Watts of power into the ring heaters (3 top, 3 bottom):

Note that there is still a bit of clipping on ITMX on the top right corner.  Using the results of a COMSOL model here, where it quotes

Model Prediction
HWS ITMX Measured
HWS ITMY Measured